Dissertations / Theses: 'Numerical evaluation of structural response'

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Hahn, Steven R. "An evaluation of acoustic response to structural modification." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17023.

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Terro, Mohamad Jamil. "Numerical modelling thermal and structural response of reinforced concrete structures in fire." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/7558.

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Kromanis, Rolands. "Structural performance evaluation of bridges : characterizing and integrating thermal response." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/17440.

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Bridge monitoring studies indicate that the quasi-static response of a bridge, while dependent on various input forces, is affected predominantly by variations in temperature. In many structures, the quasi-static response can even be approximated as equal to its thermal response. Consequently, interpretation of measurements from quasi-static monitoring requires accounting for the thermal response in measurements. Developing solutions to this challenge, which is critical to relate measurements to decision-making and thereby realize the full potential of SHM for bridge management, is the main focus of this research. This research proposes a data-driven approach referred to as temperature-based measurement interpretation (TB-MI) approach for structural performance evaluation of bridges based on continuous bridge monitoring. The approach characterizes and predicts thermal response of structures by exploiting the relationship between temperature distributions across a bridge and measured bridge response. The TB-MI approach has two components - (i) a regression-based thermal response prediction (RBTRP) methodology and (ii) an anomaly detection methodology. The RBTRP methodology generates models to predict real-time structural response from distributed temperature measurements. The anomaly detection methodology analyses prediction error signals, which are the differences between predicted and real-time response to detect the onset of anomaly events. In order to generate realistic data-sets for evaluating the proposed TB-MI approach, this research has built a small-scale truss structure in the laboratory as a test-bed. The truss is subject to accelerated diurnal temperature cycles using a system of heating lamps. Various damage scenarios are also simulated on this structure. This research further investigates if the underlying concept of using distributed temperature measurements to predict thermal response can be implemented using physics-based models. The case study of Cleddau Bridge is considered. This research also extends the general concept of predicting bridge response from knowledge of input loads to predict structural response due to traffic loads. Starting from the TB-MI approach, it creates an integrated approach for analyzing measured response due to both thermal and vehicular loads. The proposed approaches are evaluated on measurement time-histories from a number of case studies including numerical models, laboratory-scale truss and full-scale bridges. Results illustrate that the approaches accurately predicts thermal response, and that anomaly events are detectable using signal processing techniques such as signal subtraction method and cointegration. The study demonstrates that the proposed TB-MI approach is applicable for interpreting measurements from full-scale bridges, and can be integrated within a measurement interpretation platform for continuous bridge monitoring.

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Koyyapu, Naresh Kumar. "Numerical Computation of Transient Response of 2D Wedge Impact." ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2260.

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The diverse applications of advanced marine craft ascribed to their high speed and technological advancements has led to the use of stronger and lighter metals in such crafts. High speed, in effect also increases slamming loads as higher speed increases frequency of wave encounter while operating in waves. The present study is limited to wedge impact models. Fundamentally, the study is thus about two-dimensional (2D) wedge impact in water. In an attempt to predict the structural response to impact hydrodynamic force, a beam element based finite element (FE) computer program is written and the results of the code are presented in the thesis. A computational tool is developed to predict the transient elastic response of a 2D wedge under impact force using two different numerical methods. Both explicit and implicit numerical schemes have also been studied in order to apply to the present work. Explicit forth order Runge-Kutta (RK4) method and implicit Newmark-b (NB) method have been used in the present work. Coupling effects between excitation and response are ignored in the present numerical computations. Both the numerical schemes are validated using simple static solution and also modal expansion technique.

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Shahrokh, Esfahani Marjan, and Hamedani Rasoul Nilforoush. "Numerical Evaluation of Structural Behavior of the Simply Supported FRP-RC Beams." Thesis, KTH, Betongbyggnad, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-100876.

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The main problem of steel-reinforced concrete structures is corrosion of steel reinforcements which leads to premature failure of the concrete structures. This problem costs a lot annually to rehabilitate and repair these structures. In order to improve the long-term performance of reinforced concrete structures and for preventing this corrosion problem, Fiber Reinforced Polymer (FRP) bars can be substituted of conventional steel bars for reinforcing concrete structures. This study is a numerical study to evaluate structural behavior of the simply supported concrete beams reinforced with FRP bars in comparison with steel-reinforced concrete beams. The commercial Finite Element Modeling program, ABAQUS, has been used for this purpose and the ability of aforementioned program has been investigated to model non-linear behavior of the concrete material. In order to evaluate the structural behavior of FRP-reinforced concrete beams in this study, two different aspects have been considered; effect of different types and ratios of reinforcements and effect of different concrete qualities. For the first case, different types and ratios of reinforcements, four types of reinforcing bars; CFRP, GFRP, AFRP and steel, have been considered. In addition, the concrete material assumed to be of normal strength quality. For verifying the modeling results, all models for this case have been modeled based on an experimental study carried out by Kassem et al. (2011). For the second case, it is assumed that all the models contain high strength concrete (HSC) and the mechanical properties of concrete material in this case are based on an experimental study performed by Hallgren (1996). Hence, for comparing the results of the HSC and NSC models, mechanical properties of reinforcements used for the second case are the same as the first case. Furthermore, a detailed study of the non-linear behavior of concrete material and FE modeling of reinforced concrete structures has been presented. The results of modeling have been presented in terms of; moment vs. mid-span deflection curves, compressive strain in the outer fiber of concrete, tensile strain in the lower tensile reinforcement, cracking and ultimate moments, service and ultimate deflections, deformability factor and mode of failure. Finally, the results of modeling have been compared with predictions of several codes and standards such as; ACI 440-H, CSA S806-02 and ISIS Canada Model.
Det största problemet med stålarmerade betongkonstruktioner är korrosion av stålarmeringen vilket leder till tidiga skador i betongkonstruktionen. Årligen åtgår stora summor till reparation och ombyggnad av konstruktioner som drabbas av detta problem. För att förbättra den långsiktiga prestandan hos armerade betongkonstruktioner, och för att förhindra korrosionsproblemet, kan konventionella stålstänger ersättas av FRP-stänger (fiberarmerade polymerkompositer) för armering av betongkonstruktioner. Detta arbete är en numerisk undersökning för att uppskatta det strukturella beteendet av fritt upplagda betongbalkar, förstärkta med FRP-stänger i jämförelse med stålarmerade betongbalkar. Det kommersiella finita element modelleringsprogrammet ABAQUS, har använts för detta ändamål. Även programmets förmåga när det gäller att modellera icke-linjära beteenden av betongmaterial har undersökts. För att uppskatta det strukturella beteendet av FRP-armerade betongbalkar har hänsyn tagits till två olika aspekter, effekten av olika armeringstyper och deras proportioner samt effekten av olika betongkvaliteter. I det första fallet har olika armeringstyper och deras proportioner, fyra typer av armeringsstänger; CFRP, GFRP, AFRP och stål betraktats. Dessutom antas att betongen har normal hållfasthet. För att kontrollera resultatet av modelleringen, har i detta fall räkneexemplen baserats på experimentella studier utförda av Kassem et al. (2011). I det andra fallet har antagits att alla modeller innehåller höghållfast betong (HSC) och även de mekaniska egenskaperna hos betongmaterialet bygger i detta fall på en experimentell studie utförd av Hallgren (1996). För att jämföra resultatet av HSC- och NSC-modeller, är armeringens mekaniska egenskaper de samma som används för det andra fallet. Vidare har en detaljerad undersökning av betongmaterialets icke-linjära beteende och FE-modellering av armerade betongkonstruktioner presenterats. Resultaten av modelleringen har presenterats i form av; kurvor för sambandet mellan moment och mittspannets nedböjning, krympning i betongens översida, förlängningen av den lägre dragarmeringen, sprickmoment och maximalt moment, service- och maximal nedböjning, formfaktor samt typ av brott. Slutligen har resultaten från modellberäkningar jämförts med förutsägelser baserade på flera regler och standarder såsom; ACI 440-H, CSA S806-02 och ISIS Canada Model.

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Arslan, Hakan. "A Numerical Study On Response Factors For Steel Wall-frame Systems." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610811/index.pdf.

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A numerical study has been undertaken to evaluate the response of dual systems which consist of steel plate shear walls and moment resisting frames. The primary objective of the study was to investigate the influence of elastic base shear distribution between the wall and the frame on the global system response. A total of 10 walls and 30 wall-frame systems, ranging from 3 to 15 stories, were selected for numerical assessment. These systems represent cases in which the elastic base shear resisted by the frame has a share of 10%, 25%, or 50% of the total base shear resisted by the dual system. The numerical study consisted of 1600 time history analyses employing three-dimensional finite elements. All 40 structures were separately analyzed for elastic and inelastic response by subjecting to the selected suite of earthquake records. Interstory drifts, top story drift, base shears resisted by the wall and the frame were collected during each analysis. Based on the analysis results, important response quantities such as the response modification, the overstrength, the displacement amplification and ductility reduction factors are evaluated herein. Results are presented in terms of several measures such as the interstory drift ratio and the top story drift ratio. A discussion related to the influence of load share on the response factors is given.

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Kurban, Can Ozan. "A Numerical Study On Response Factors For Steel Plate Shear Wall Systems." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610741/index.pdf.

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Design recommendations for steel plate shear wall (SPSW) systems have recently been introduced into seismic provisions for steel buildings. Response modification, overstrength, and displacement amplification factors for SPSW systems presented in the design codes were based on professional experience and judgment. A numerical study has been undertaken to evaluate these factors for SPSW systems. Forty four unstiffened SPSWs possessing different geometrical characteristics were designed based on the recommendations given in the AISC Seismic Provisions. Bay width, number of stories, story mass, and steel plate thickness were considered as the prime variables that influence the response. Twenty records were selected to include the variability in ground motion characteristics. In order to provide a detailed analysis of the post-buckling response, three-dimensional finite element analyses were conducted for the 44 structures subjected to the selected suite of earthquake records. For each structure and earthquake record two analyses were conducted in which the first one includes geometrical nonlinearities and the other one includes both geometrical and material nonlinearities, resulting in a total of 1760 time history analysis. In this thesis, the details of the design and analysis methodology are given. Based on the analysis results response modification, overstrength and displacement amplification factors for SPSW systems are evaluated.

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Jamil, A. "Structural response of novel PU structures under quasi-static, impact and blast loading : experimental and numerical analyses." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3018626/.

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Hur, Jieun. "Seismic performance evaluation of switchboard cabinets using nonlinear numerical models." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45813.

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Past earthquake events have shown that seismic damage to electrical power systems in commercial buildings, hospitals, and other systems such as public service facilities can cause serious economic losses as well as operational problems. A methodology for evaluation of the seismic vulnerability of electrical power systems is needed and all essential components of the system must be included. A key system component is the switchboard cabinet which houses many different elements which control and monitor electrical power usage and distribution within a building. Switchboard cabinets vary in size and complexity and are manufactured by a number of different suppliers; a typical cabinet design was chosen for detailed evaluation in this investigation. This study presents a comprehensive framework for the evaluation of the seismic performance of electrical switchboard cabinets. This framework begins with the introduction and description of the essential equipment in building electrical power systems and explains possible seismic damage to this equipment. The shortcomings of previous studies are highlighted and advanced finite element models are developed to aid in their vulnerability estimation. Unlike previous research in this area, this study proposes practical, computationally efficient, and versatile numerical models, which can capture the critical nonlinear behavior of switchboard cabinets subjected to seismic excitations. A major goal of the current study was the development of nonlinear numerical models that can accommodate various support boundary conditions ranging from fixed, elasto-plastic to free. Using both linear and nonlinear dynamic analyses, this study presents an enhanced evaluation of the seismic behavior of switchboard cabinets. First the dynamic characteristics of switchboard cabinets are determined and then their seismic performance is assessed through nonlinear time history analysis using an expanded suite of ground motions. The seismic responses and associated ground motions are described and analyzed using probabilistic seismic demand models (PSDMs). Based on the PSDMs, the effectiveness and practicality of common intensity measures are discussed for different components. Correlation of intensity measures and seismic responses are then estimated for each component, and their seismic performance and uncertainties are quantified in terms of engineering demand parameters. The results of this study are intended for use in the seismic vulnerability assessment of essential electrical equipment in order to achieve more reliable electrical power systems resulting in reduced overall risk of both physical and operational failures of this important class of nonstructural components.

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Luboya, Silhady Tshitende. "Response of Footbridges equipped with TLD : A numerical and experimental assessment." Thesis, KTH, Bro- och stålbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278563.

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In recent years, an increase to design slender and aesthetically-pleasing structures have resulted in some structures having a low natural frequency. This is because the design calculation did not meet the requirement of serviceability performance. Structures can experience excessive vibrations when they are subjected to different types of dynamic loading. A device can be installed to prevent these vibrations.In this thesis, we study the response of buildings and lateral vibrations of footbridges equipped with Tuned Liquid Damper. The aim is to mitigate the first mode of vibration. Tuned Liquid Damper consists of a container in rectangular, cylindrical or arbitrary shape partially filled with shallow liquid, most often water is used as a regulating device system. The design properties of Tuned Liquid Damper is introduced and it is based on the analogyof the most popular damper, Tuned Mass Damper.An experimental study of a building frame model with four floors is conducted to validate the numerical results obtained from the simulation of the model in ANSYS. The linear and non-linear analysis are performed through a system coupling between Ansys mechanical and Fluent solver. The simulation results obtained are in good agreement with the experimental results.A parametric study is conducted with a simply supported steel footbridge. It is a 45 m long span with 3 m width and the flexural rigidity is modified to get the lateral vibration mode. The first lateral natural frequency obtained is 0.713 Hz. The load case for the study considered is according to Sétra guide. The variable parameters studied is the Tuned Liquid Damper water mass ratios: 0.7%, 1.0%, 2.0%, 3.0% and 4.0%. The results show a satisfactory performance of the footbridge model equipped with Tuned Liquid Damper. The accelerations are below 0.1 m/s2 which satisfied the requirement of 0.15 m/s2.

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Finozzi, Irene Barbara Nina Verfasser], and Harald [Akademischer Betreuer] [Budelmann. "Structural response of corrosion damaged RC members: numerical analyses and experimental investigation / Irene Barbara Nina Finozzi ; Betreuer: Harald Budelmann." Braunschweig : Technische Universität Braunschweig, 2017. http://d-nb.info/1175818283/34.

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Awang, Draup Awang Jefri. "Numerical simulation of the structural response of friction stir welded aluminium 2139-T8 alloy subjected to complex loading configurations." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/numerical-simulation-of-the-structural-response-of-friction-stir-welded-aluminium-2139t8-alloy-subjected-to-complex-loading-configurations(a840bd28-102d-4c15-be6c-b4e72631e875).html.

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Friction stir welding (FSW) and aluminium alloy 2139-T8 are currently being considered for use in future military vehicles. However, stringent regulations on weld integrity under extreme loading conditions limit the adoption of new technologies. Moreover, current finite element (FE) based methods do not give reliable predictions of strain distribution in welds, which makes it difficult to assess the performance of structures. Therefore, an extensive research program was carried out to develop a generalised finite element (FE) based methodology to predict the response of welded structures under complex loading configurations. The methodology enables the complex distribution of mechanical properties arising from welding, which is linked to microstructural variation, to be incorporated into a macro scale structural model. The method is general, and is applicable for any heat treatable aluminium alloy under a range of joining processes. To achieve this, the microstructure of 2139-T8 alloy was characterised at a range of length scales, with particular emphasis on the size and distribution of strengthening Omega precipitates. 2139-T8 was subjected to bead on plate FSW to enable characterisation of the effects of processing on the local microstructure. In addition, kinetic data for 2139-T8 was generated, allowing a simple softening model to be developed; this allowed the post-weld strength distribution to be predicted. The model was also used to recreate bulk specimens of 2139-T8 with equivalent local weld microstructure, which was verified by transmission electron microscopy. Material with equivalent microstructure was used to estimate the local mechanical property distributions across the weld, including the initial yield stress and plastic response; the mechanical properties of 2139-T8 are known to be representative of 2139-T84. From observations of this combined data, a methodology was developed to enable the estimation of the complex mechanical property distributions arising during welding. Furthermore, an automated computer program was written to implement the property distributions into FE based models. The methodology was verified using data generated for 2139-T8 and was used to simulate the response of FSW 2139-T8 loaded in uniaxial tension. The simulations were verified experimentally using digital image correlation (DIC) and the methodology was shown to demonstrate increased accuracy and reliability over existing FE methods, with respect to strain predictions. In addition, the method eliminates the need to calibrate the structural model to a particular loading configuration. Theoretically, the models are insensitive to loading and this property was tested by extending the model to simulate the strain distribution of large scale welded panels subject to explosive blast loading. The simulations were verified against blast tests where FSW 2139-T84 panels were subjected to blast loading from the detonation of plastic explosive. The results indicate that the modelling methodology developed is capable of producing accurate and reliable predictions of strain distribution in welded structures under complex loading configurations.

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SALVI, Jonathan. "Optimisation of Tuned Mass Damper Devices Towards Structural Vibration Reduction: Theoretical Settings and Numerical Analyses." Doctoral thesis, Università degli studi di Bergamo, 2014. http://hdl.handle.net/10446/224063.

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The present doctoral thesis concerns theoretical concepts and numerical studies on the optimisation of Tuned Mass Damper (TMD) devices towards the control and reduction of structural dynamic responses, with specific reference to the context of civil and seismic engineering. The fundamental background of the optimisation of the TMD parameters, also called tuning, is presented first in its main features, based on reference to the mainstream literature, and in the assessing the relevance of the structural properties and of the role of the characteristics of the external excitation. A comprehensive analysis on the tuning of passive TMDs as applied to a singledegree-of-freedom primary structure subjected to benchmark ideal excitations is carried out, focusing on a range of structural parameters typical of real engineering applications. Then, the outcomes have been interpolated through nonlinear least squares and optimum tuning formulas of the TMD parameters have been outlined for each excitation case, based on ad hoc polynomial fitting models. Comparisons with main references from the literature are provided. The optimisation of TMD devices has been also investigated for the mitigation of the transient response, with main focus on the impulse excitation. Initially, a throughout optimisation of the passive device is derived, with consideration of different excitation cases, objective functions and structural parameters. Then, the control device has been upgraded to a hybrid TMD by means of the addition of an active controller, with the main task of reducing as well the peak response. Different feedback control strategies have been evaluated, from the points of view of: stability, device performance and amount of supplied control force. An important part of this research deals with the concept of optimum seismic tuning of TMDs, with real earthquake input directly involved within the tuning process. This feature represents an innovative way of investigating the TMD performance, since the control device is theoretically optimised on each specific structure and seismic event. The proposed tuning procedure is presented in detail and applied to a significant selection of structures and earthquake input signals. The so obtained optimum TMD parameters are first depicted and compared to those obtainable from reference tuning formulas from the literature. A wide set of results concerning the performance of the TMD is presented, considering different kinematic and energy response indexes, in order to trace down general trends on the effectiveness of the TMD in reducing the seismic response. A further and important stage of this study deals with a crossed comparison involving the TMD performance and relevant indexes such as the modal parameters, the frequency amplitude of the seismic signal and the response spectra, so that to inspect possible connections between the efficiency of the control device and the characteristics of the structural and the dynamic context. The studies and related outcomes presented in this thesis shall represent a contribution to the development and improvement of Tuned Mass Damper devices in terms of optimum performance, towards the control of a wide range of structures. Therefore, the presented thesis work, though connoted by a main theoretical character, may display different crucial implications in practical engineering applications.

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Oruganti, Krishna, and krishnaov@yahoo com. "Evaluation of Damage in Structures using Vibration-based Analyses." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091002.143408.

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Composite materials are supplanting conventional metals in aerospace, automotive, civil and marine industries in recent times. This is mainly due to their high strength and light weight characteristics. But with all the advantages they have, they are prone to delamination or matrix cracking. These types of damage are often invisible and if undetected, could lead to appalling failures of structures. Although there are systems to detect such damage, the criticality assessment and prognosis of the damage is often more difficult to achieve. The research study conducted here primarily deals with the structural health monitoring of composite materials by analysing vibration signatures acquired from a laser vibrometer. The primary aim of the project is to develop a vibration based structural health monitoring (SHM) method for detecting flaws such as delamination within the composite beams. Secondly, the project emphasises on the method's ability to recognise the locatio n and severity of the damage within the structure. The system proposed relies on the examination of the displacement mode shapes acquired from the composite beams using the laser vibrometer and later processing them to curvature mode shapes for damage identification and characterization. Other identification techniques such as a C-scan has been applied to validate the location and size of the defects with the structures tested. The output from these plots enabled the successful identification of both the location and extent of damage within the structure with an accuracy of 96.5%. In addition to this, this project also introduces a method to experimentally compute the critical stress intensity factor, KIC for the composite beam. Based on this, a technique for extending the defect has been proposed and validated using concepts of fatigue and fracture mechanics. A composite specimen with a 40 mm wide delamination embedded within was loaded under fatigue conditions and extension of the defect by 4mm on either s ide of the specimen's loading axis was achieved satisfactorily. The experimental procedure to extend the defect using fatigue was validated using the SLV system. Displacement and Curvature mode shapes were acquired post-fatigue crack extension. Upon analysing and comparing the displacement and curvature mode shapes before and after crack extension, the extended delamination was identified satisfactorily.

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15

Van, Deventer Megan. "The development and empirical evaluation of an work engagement structural model." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96784.

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Thesis (MComm)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Work Engagement is one construct of many that forms part of the complex nomological network of constructs underlying the behaviour of working man2. Work Engagement is an important construct both from an individual as well as from an organisational perspective. Human resource management interventions aimed at enhancing Work Engagement aspire to contribute to the achievement of the organisation’s primary objective and the well-being of the organisation’s employees. Such interventions will most likely also be valued by individuals within the workplace, as individuals will be able to experience a sense of personal fulfilment through self-expression at work. It is therefore essential to gain a valid understanding of the Work Engagement construct and the psychological mechanism that underpins it, in order to design human resource interventions that will successfully enhance Work Engagement. The current study raises the question why variance in Work Engagement exists amongst different employees working in different organisational contexts. The research objective of the current study is to develop and empirically test an explanatory Work Engagement structural model that will provide a valid answer to this question. In this study, a comprehensive Work Engagement structural model was proposed. An ex post facto correlational design with structural equation modelling (SEM) as the statistical analysis technique was used to test the substantive research hypotheses as represented by the Work Engagement structural model. Furthermore, the current study tested two additional narrow-focus structural models describing the impact of value congruence on Work Engagement by using an ex post facto correlational design with polynomial regression as the statistical analysis technique. A convenience sample of 227 teachers working in public sector schools falling under the jurisdiction of the Western Cape Education Department (WCED) participated in the study. The comprehensive Work Engagement model achieved reasonable close fit. Support was found for all of the hypothesised theoretical relationships in the Work Engagement structural model, except for the influence of the PsyCap*Job Characteristics interaction effect on Meaningfulness and for three of the five latent polynomial regression terms added in the model in an attempt to derive response surface test values. The response surface analyses findings were mixed. Based on the obtained results, meaningful practical recommendations were derived.
AFRIKAANSE OPSOMMING: Werkverbintenis1 is een van ‘n groot verskeidenheid konstrukte wat deel vorm van die komplekse nomologiese netwerk van konstrukte wat die gedrag van die arbeidende mens onderlê. Werkverbintenis word as ‘n belangrike konstruk beskou vanuit ‘n individuele sowel as vanuit ‘n organisatoriese perspektief. Menslike hulpbronbestuurs-intervensies gerig op die bevordering van Werkverbintenis streef daarna om by te dra tot die bereiking van die organisasie se primêre doel sowel as tot die welstand van die organisasie se werknemers. Sodanige intervensies sal waarskynlik ook deur werknemers waardeer word, aangesien sodanige intervensies die kanse verhoog dat individue selfvervulling in hul werk sal ervaar omdat die werk hul die geleentheid bied om hulself in hul werk uit te leef. Dit is gevolglik noodsaaklik om ‘n geldige begrip te ontwikkel van die Werkverbintenis-konstruk en die sielkundige meganisme wat dit onderlê ten einde menslike hulpronbestuurs-intervensies te ontwerp wat suksesvol Werkverbintenis sal bevorder. Die huidige studie stel die vraag aan die orde waarom variansie in Werkverbintenis tussen verskillende werknemers bestaan wat in verskillende organisatoriese kontekste werk. Die navorsingsdoelstelling van die huidige studie is om ‘n verklarende Werkverbintenisstrukturele model te ontwikkel en te toets wat ‘n geldige antwoord op hierdie vraag sal bied. ‘n Omvattende Werkverbintenis strukturele model is in hierdie studie voorgestel. ‘n Ex post facto korrelatiewe ontwerp met strukturele vergelykingsmodellering (SVM) as die statistiese ontledingstegniek is gebruik om die substantiewe navorsingshipotese soos voorgestel deur die Werkverbintenis strukturele model te toets. Die huidige studie het voorts twee addisionele nouer-fokus strukturele modelle getoets wat die impak van waardekongruensie op Werkverbintenis beskryf deur middel van ‘n ex post facto korrelatiewe ontwerp met polinomiese regressie-ontleding as statistiese ontledingstegniek. ‘n Geriefsteekproef van 227 onderwysers wat in openbare skole werksaam is wat onder die beheer van die Wes Kaapse Department van Onderwys val (WKDO) het aan die studie deelgeneem. Die omvattende Werkverbintenis-model het redelik goeie pasgehalte getoon. Steun is gevind vir all die voorgestelde teoretiese verwantskappe in die Werkverbintenis strukturele model, behalwe vir die invloed van die Sielkundige kapitaal*Werk eienskappe-interaksie-effek op Betekenisvolheid en vir drie van die vyf polinomiese latente regressie-terme wat in die model ingesluit is in ‘n poging om responsoppervlakte-waardes af te lei. Gemengde resultate is verkry vir die responsoppervlakte-ontleding. Betekenisvolle praktiese aanbevelings is gemaak op grond van die navorsingsresultate.

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Bakir, Serhan. "Evaluation Of Seismic Response Modification Factors For Steel Frames By Non-linear Analysis." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607827/index.pdf.

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In this study steel framing systems are investigated with regards to their lateral load carrying capacity and in this context seismic response modification factors of individual systems are analyzed. Numerous load resisting layouts, such as different bracing systems and un-braced moment resisting frames with various bay and story configurations are designed and evaluated in a parametric fashion. Three types of beam to column connection conditions are incorporated in evaluation process. Frames, designed according to Turkish seismic code, are investigated by nonlinear static analysis with the guidance of previous studies and recent provisions of FEMA. Method of analysis, design and evaluation data are presented in detail. Previous studies in literature, history and the theory of response modification phenomenon is presented. Results are summarized, main weaknesses and ambiguities introduced to design by the use of &ldquo
R&rdquo
factors are stated depending on the observed behavior.

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FIERRO, Tony. "Implementation and use of advanced constitutive models in numerical codes for the evaluation of the soil response under seismic loadings." Doctoral thesis, Università degli studi del Molise, 2022. https://hdl.handle.net/11695/115267.

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La previsione del comportamento dei terreni sotto azioni sismiche rappresenta un arduo obiettivo da raggiungere per l’Ingegneria Geotecnica Sismica. In tali condizioni, è possible raggiungere un’ampio range di livelli deformativi. In questo contesto, un ruolo chiave lo gioca la modellazione numerica, ma differenti requisiti sono necessari affinchè essa sia efficace: il terreno va modellato con un solido modello costitutivo su una piattaforma software testata e la geometria del problema va correttamente definita. Con queste premesse, la tesi mostra l’implementazione e l’uso di modelli costitutivi avanzati in OpenSees, una piattaforma numerica open-source, per studiare l’applicabilità di questi ultimi a casi pratici. Sono stati considerati differenti scenari in cui sono mobilizzati livelli diversi di deformazione e di complessità crescente in termini di geometria del problema. Inizialmente, sono stati analizzati i modelli costitutivi più diffusi per riprodurre la risposta meccanica dei terreni granulari in condizioni non drenate. È emerso che SANISAND e PM4SAND sono gli unici disponibili in OpenSees, mentre il modello NTUASand02 non è mai stato implementato in un codice agli elmenti finiti per analisi di risposta sismica locale in condizioni non drenate. Per tale ragione, il modello è stato inserito in OpenSees e la procedura seguita per l’implementazione e la validazione del modello è mostrata in dettaglio. Sono state simulate prove triassiali e di taglio semplice, monotone e cicliche, in condizioni drenate e non, per osservare la risposta a livello dell’elemento e confrontare i risultati ottenuti in OpenSees con quelli dell’implementazione originale. Inoltre, sono stati testati differenti schemi di integrazione ed è stata riprodotta la curva di decadimento del modulo di rigidezza a taglio della sabbia del Nevada. I tre modelli (SANISAND, PM4SAND, NTUASand02) sono stati poi adottati per studiare la risposta sismica di una colonna di 20 m di sabbia del Nevada. Il confronto tra le risposte si è rivelato soddisfacente, specialmente in condizioni drenate e non drenate a bassi livelli deformativi. Quando, invece, si aumenta l’ampiezza del moto sismico, la liquefazione influenza molto la risposta. Poi, sono stati simulati due test in centrifuga in condizioni free-field condotti nell’ambito del Progetto LIQUEFACT sulla sabbia del Ticino. La linea mediana della scatola è stata riprodotta alla scala del prototipo e il terreno è modellato con PM4SAND. I risultati delle simulazioni hanno evidenziato come le serie temporali sono correttamente riprodotte, mentre le sovrappressioni neutre sono sovrastimate. Infine, è stato riprodotto il caso del bacino di San Giuliano di Puglia utilizzando l’interpreter parallelo OpenSeesSP su DesignSafe-CI. In particolare, nel 2002, il terremoto del Molise ha causato la morte di 27 bambini e una maestra nell’area di nuova costruzione del paese, mentre nel centro storico si sono osservati danni molto ridotti. Per tale ragione, il bacino è stato modellato in OpenSeesSP utilizzando i dati geotecnici più recenti ed il sistema di monitoraggio installato nel paese è stato utilizzato per la validazione del modello numerico. Il modello pressure-independent multi-yield è stato utilizzato per il bacino. In generale, si è osservato un buon accordo tra accelerogrammi simulati e registrati, mentre i profili del fattore di amplificazione sono risultati consistenti con la distribuzione del danno conseguente al sisma del 2002.
The prediction of soil behaviour when seismic loads are applied is a challenging task to be achieved in Geotechnical Earthquake Engineering. However, when dynamic loadings are involved, low-to-high strain levels are reached. In this context, a key role is played by the numerical modelling, and different features are required to make it reliable: the soil should be modelled exploiting a solid constitutive framework, a widely tested software platform should be adopted, and the geometry of the problem under analysis should be correctly defined. On these premises, the thesis focuses on the implementation and use of advanced constitutive models in an open-source numerical platform, namely OpenSees, to show their applicability to practical cases. Different scenarios mobilizing small-to-high strain levels are considered and an increasing complexity of the geometry of the problem is analyzed. Firstly, the most adopted constitutive models able to simulate granular soils behaviour under undrained conditions are reviewed; here, it emerged that SANISAND and PM4SAND only are available in OpenSees, while the NTUASand02 model has never been implemented in a finite element code to perform fully-coupled site response analysis. For this reason, the model has been added to the OpenSees framework, and the whole procedure to implement and validate the implementation is shown in detail. Drained and undrained, monotonic and cyclic, triaxial and direct simple shear tests have been performed to compare the elemental response obtained in OpenSees to that resulting from the original implementation. Furthermore, different integration schemes have been tested and the modulus reduction curve of Nevada sand has been simulated. Then, the three constitutive models (SANISAND, PM4SAND, NTUASand02) have been tested in the simulation of the response of a 20-m thick column of Nevada sand. The comparison between the resulting responses has revealed satisfactory, especially under drained conditions and under undrained conditions at low-strain levels. When the shaking amplitude increases, soil liquefaction strongly affects the responses. Then, two free-field centrifuge tests performed in the framework of LIQUEFACT project on Ticino Sand has been simulated. The centerline of the centrifuge box has been modelled at the prototype scale and the soil non-linearity has been accounted for using PM4SAND. The results of the simulations highlighted that the acceleration time-series are correctly reproduced, while the excess pore water pressure time series are overestimated. Finally, the paradigmatic case of the San Giuliano di Puglia basin is modelled exploiting the valuable computational capabilities of the single processor parallel interpreter OpenSeesSP on the DesignSafe-CI. In particular, in 2002, the Molise Earthquake caused the death of 27 children and a teacher in the newly built area of the town, while the historical core experienced limited damage. For this reason, the whole valley has been modelled in OpenSeesSP exploiting the most recent geotechnical data and the monitoring system installed in the town has been used as benchmark to validate the numerical model. The soil behaviour is modelled using the pressure-independent multi-yield constitutive model. Generally, a good agreement has been highlighted in the time domain by comparing recorded and simulated data, while the amplification factor profile is consistent to the damage distribution observed after the 2002 earthquake.

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18

Wei, Min. "A Structural and Psychometric Evaluation of a Situational Judgment Test: The Workplace Skills Survey." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc799488/.

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Some basic but desirable employability skills are antecedents of job performance. The Workplace Skills Survey (WSS) is a 48-item situational judgment test (SJT) used to assess non-technical workplace skills for both entry-level and experienced workers. Unfortunately, the psychometric evidence for use of its scores is far from adequate. The purpose of current study was two-fold: (a) to examine the proposed structure of WSS scores using confirmatory factor analysis (CFA), and (b) to explore the WSS item functioning and performance using item response theory (IRT). A sample of 1,018 Jamaican unattached youth completed the WSS instrument as part of a longitudinal study on the efficacy of a youth development program in Jamaica. Three CFA models were tested for the construct validity of WSS scores. Parameter estimations of item difficulty, item discrimination, and examinee’s proficiency estimations were obtained with item response theory (IRT) and plotted in item characteristics curves (ICCs) and item information curves (IICs). Results showed that the WSS performed quite well as a whole and provided precise measurement especially for respondents at latent trait levels of -0.5 and +1.5. However, some modifications of some items were recommended. CFA analyses showed supportive evidence of the one-factor construct model, while the six-factor model and higher-order model were not achieved. Several directions for future research are suggested.

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19

Mutlu, Mehmet Basar. "Numerical Simulations Of Reinforced Concrete Frames Tested Using Pseudo-dynamic Method." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614460/index.pdf.

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Considering the deficiencies frequently observed in the existing reinforced concrete buildings, detailed assessment and rehabilitation must be conducted to avoid significant life and value loss in seismic zones. In this sense, performance based evaluation methods suggested in the regulations and codes must be examined and revised through experimental and analytical research to provide safe and economical rehabilitation solutions. In this study, seismic behavior of three reinforced concrete frames built and tested in Middle East Technical University Structural Mechanics Laboratory is examined. The specimens are extracted from a typical interior frame of 3-story 3-bay reinforced concrete structure. One of the specimens has compliant design according to Turkish Earthquake Code (2007) and each of the other two specimens represents different types of deficiencies in terms of material strength and detailing. The test specimens were modeled using different modeling approaches and nonlinear dynamic analyses were conducted on the numerical models. Results of continuous pseudo-dynamic testing of three ground motions are presented and compared with the numerical simulations on models. Calibrated finite element models were used for evaluation of performance assessment procedure of Turkish Earthquake Code (2007) and further investigation on local deformation components in light of experimental findings and observations. Deformation sources of columns and joints were studied in terms of their interaction and contributions to the total drift. Estimated plastic hinge lengths of columns were compared with the experimental observations and the proposed expressions in the literature.

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20

Montalban, Laura. "Evaluation of a Contactless Excitation and Response System (CERS) for process planning applications : An experimental study." Thesis, KTH, Industriell produktion, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192679.

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Chatter vibration is a common problem for the manufacturing industry that limits the productivity, accuracy and surface quality of machined parts. This study is focused on the out of process methods, such as Stability Lobe Diagrams (SLD), that ensure the selection of the optimal cutting parameters in which the machining process is stable. Previous studies have found that the dynamic properties of the spindle change with the rotational speed. This fact can also affect the accuracy of the SLD predictions, since, the traditional structural dynamic tests such as the Experimental Modal Analysis (EMA) are carried out at static state. An alternative method for the calculation of speed - dependant SLD using a Contactless Excitation Response System (CERS) was proposed. The modal characteristics, such as natural frequencies and damping ratio were determined by EMA tests carried out at idle state whereas CERS measurements were performed at increasing rotational speeds up to 14000 rpm. Subsequently, the SLD at static and dynamic state were computed. Finally, it was concluded that there was not a significant variation of the dynamic properties and SLD prediction with spindle speed at the tested speed range (0 rev/min to 14000 rev/min).
Chatter är ett vanligt problem inom tillverkningsindustrin som begränsar produktiviteten och minskar noggrannheten och kvalitén på bearbetade ytor. Denna studie fokuserar på processkilda metoder, till exempel stabilitetsdiagram (SLD), vilka säkerställer valet av optimala skärparametrar för en stabil skärprocess. Tidigare studier har visat att spindelns dynamiska egenskaper är beroende av rotationshastigheten. Detta påverkar även noggrannheten vid skattningen av SLD eftersom traditionella strukturdynamiska tester, som experimentell modalanalys (EMA), utförs under statiskt tillstånd. En alternativ metod för bestämning av hastighetsberoende SLD med hjälp av ett beröringsfritt excitering- och svarssystem (CERS) föreslås. De modala egenskaperna, som till exempel egenfrekvens och dämpning, bestämdes med hjälp av EMA med stillastående spindel medan mätningar med CERS utfördes med ökad rotationshastighet upp till 14000 varv/min. Efter detta beräknades SLD för de båda fallen. Till sist drogs slutsatsen att testerna inte påvisade någon större skillnad, vare sig dynamiska egenskaper eller SLD skattning, för spindelhastigheter inom det testade intervallet (0 till 14000 varv/min).

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21

Hernandez, Jaime A. "Evaluation of the Response of Perpetual Pavement at Accelerated Pavement Loading Facility: Finite Element Analysis and Experimental Investigation." Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1281705838.

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22

Hoskins, Matt C. "Structural-Symbolic Translation Fluency: Reliability, Validity, and Usability." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etd/3012.

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Standardized formative mathematics assessments typically fail to capture the depth of current standards and curricula. Consequently, these assessments demonstrate limited utility for informing the instructional implementation choices of teachers. This problem is particularly salient as it relates to the mathematical problem solving process. The purpose of this study was to develop and evaluate the psychometric characteristics of Structural-Symbolic Translation Fluency, a curriculum-based measure (CBM) of mathematical problem solving. The development of the assessment was based on previous research describing the cognitive process of translation (Mayer, 2002) as well as mathematical concept development at the quantitative, structural, and symbolic levels (Dehaene, 2011; Faulkner, 2009; Griffin, 2004). Data on the Structural-Symbolic Translation Fluency assessment were collected from 11 mathematics and psychometrics experts and 42 second grade students during the spring of 2016. Data were analyzed through descriptive statistics, frequencies, Spearman-Brown correlation, joint probability of agreement, Pearson correlation, and hierarchical multiple regression. Psychometric features of interest included internal consistency, inter-rater reliability, test-retest reliability, content validity, and criterion-related validity. Testing of the 9 research questions revealed 9 significant findings. Despite significant statistical findings, several coefficients did not meet pre-established criteria required for validation. Hypothesized modifications to improve the psychometric characteristics are suggested as the focus of future research. In addition, recommendations are made concerning the role of assessing the translation process of mathematical problem solving.

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23

Singh, Gurjashan. "Health Monitoring of Round Objects using Multiple Structural Health Monitoring Techniques." FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/330.

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Structural Health Monitoring (SHM) techniques are widely used in a number of Non – destructive Evaluation (NDE) applications. There is a need to develop effective techniques for SHM, so that the safety and integrity of the structures can be improved. Two most widely used SHM methods for plates and rods use either the spectrum of the impedances or monitor the propagation of lamb waves. Piezoelectric wafer – active sensors (PWAS) were used for excitation and sensing. In this study, surface response to excitation (SuRE) and Lamb wave propagation was monitored to estimate the integrity of the round objects including the pipes, tubes and cutting tools. SuRE obtained the frequency response by applying sweep sine wave to surface. The envelope of the received signal was used to detect the arrival of lamb waves to the sensor. Both approaches detect the structural defects of the pipes and tubes and the wear of the cutting tool.

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Slein, Ryan Michael. "Evaluation of Strength Reduction Factor for Concentrically Braced Frames Based on Nonlinear Single Degree-of-Freedom Systems." DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1532.

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Strength Reduction Factor (R-Factor), often referred to as Response Modification Factor, is commonly used in the design of lateral force resisting systems under seismic loading. R-Factors allow for a reduction in design base shear demands, leading to more economical designs. The reduction of strength is remedied with ductile behavior in members of proper detailing. Modern seismic codes and provisions recommend R-Factors for many types of lateral force resisting systems. However these factors are independent of the system fundamental frequency and many other important system properties, resulting in factors that may result in an unfavorable seismic response. To evaluate the validity of prescribed R-Factors an extensive analytical parameter study was conducted using a FEM single degree-of-freedom Concentrically Braced Frame (CBF) under incremental dynamic analysis over a suite of ground motions. Parameters of the study include brace slenderness, fundamental frequency, increment resolution, FEM mesh refinement, effects of leaning columns, and effects of low-cycle fatigue. Results suggest that R-Factor can vary drastically for CBF systems with differing properties.

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25

Siruvole, Sandeep Kumar Lankarani Hamid M. "Evaluation of the occupant response and structural damage according to the newly proposed pole test under Federal Motor Vehicle Safety Standard side impact regulation." Diss., A link to full text of this thesis in SOAR, 2007. http://soar.wichita.edu/dspace/handle/10057/1173.

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Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
"May 2007." Title from PDF title page (viewed on Dec. 29, 2007). Thesis adviser: Hamid M. Lankarani. Includes bibliographic references (leaves 60-62).

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26

Piccioni, Flavio. "Numerical Evaluation of Mode II Disbonding on Fiberglass CCPs-Specimens and Material Characterization Utilizing a Distributed Sensing Rayleigh Backscattering System." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/19848/.

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Nowadays, composite materials have become the main construction materials for aeronautical structures, replacing traditional materials commonly used in this industry. However, composite structures are still characterized by conservative designs due to the lack of understanding from a physics-based approach their damage propagation and failure mechanisms. Since repairs of composite structures are a crucial part of the long-term use of composites in aerospace, the stakeholders require an in depth understanding of the physics of disbonding in composites. The aim of this research is a numerical evaluation of mode II disbonding on Center Cut Plies (CCPs) specimens with a preliminary study on material characterization performed through a Distributed Sensing System (DSS). In order to fulfill the objectives of this research, CCPs specimens manufactured from unidirectional fiber prepregs will be considered. The specimens will be produced from unidirectional prepregs in order to minimize the effects of residual stress fields introduced into the specimen during the curing process. That residual stress field will be evaluated and monitored making use of a Distributed Sensing System (DSS) optical fiber mounted and embedded within the laminas of the specimen. In addition, an analytical and numerical approach through FEM analysis will be adopted and validated to verify the experimental results obtained from the DSS.

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27

Elgazzar, Hesham. "End-Shield Bridges for High-Speed Railway : Full scale dynamic testing and numerical simulations." Licentiate thesis, KTH, Bro- och stålbyggnad, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-204774.

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The increasing need for High-Speed Railway (HSR) to reduce the travelling time requires increasing research within this field. Bridges are main components of any railway network, including HSR networks, and the optimization of their design for this purpose would contribute to a faster and more cost effective development of the HSR network. The initial investment, the running and maintenance costs of the bridges can be decreased through better understanding of the their dynamic behaviour. This thesis studies the dynamic behaviour of end-shield railway bridges under HSR operation. 2D beam analysis is used to study the effect of the distribution of the train’s axle load. Relatively accurate 3D FE-models are developed to study the effect of Soil-Structure Interaction (SSI) and the dynamic response of the bridges. Modelling alternatives are studied to develop an accurate model. A full scale test of a simply supported Bridge with end-shields using load-controlled forced excitation was performed and the results were used to verify the theoretical models. A manual model updating process of the material properties of the 3D FE-model is performed using FRFs from the field measurements. A Simple 2D model is also developed, where a spring/dashpot system is implemented to simplify SSI, and updated to reproduce the field measured responses. The conclusions of the project emphasize the importance of SSI effects in the dynamic analysis of end-shield bridges for predicting their dynamic behaviour. The conclusions also show that the modelling of the surrounding soil and the assumption of the soil material parameters have significant effect on the dynamic response. Even the boundary conditions, bedrock level and the ballast on the railway track affects the response. The results also show that the bridge’s concrete section behaves as uncracked section under the studied dynamic loading.

QC 20170403

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28

Hansell, Markus, and Panagiotis Tamtakos. "Dynamic analyses of hollow core slabs : Experimental and numerical analyses of an existing floor." Thesis, KTH, Bro- och stålbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278539.

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For intermediate floors in residential and office buildings, as well as in parking garages and malls, there is a wide use of hollow core concrete slabs in Sweden today. Hollow core slabs are precast and prestressed concrete elements with cylindrical-shaped voids extending along the length of the slab. These structural elements have the advantage compared to cast-in-situ concrete slabs that they have a high strength, due to the prestressing, and that the voids allow for a lower self-weight. Additionally, the voids allow for a reduction in the use of concrete material. These characteristics offer possibilities to build long-span floors with slender designs. However, a consequence of the slenderness of the slabs is that such floors have an increased sensitivity to vibrations induced by various dynamic loads. In residential and office buildings vibrations are primarily caused by human activity, and therefore concerns related to the serviceability of such floors are raised. These vibrations are often not related to problems with structural integrity, but rather to different aspects of comfort of the residents or workers. The aim of this thesis is to provide additional information regarding the dynamic behavior of hollow core floors. An experimental modal analysis has been performed on an existing floor in an office building. The dynamic properties in the form of natural frequencies, mode shapes, damping ratios and frequency response functions were derived and analyzed from these measurements. Subsequently, several finite element models were developed, aiming to reproduce the experimental dynamic behavior of the studied floor. The measurements initially showed some unexpected dynamic responses of the floor. For this reason, more advanced methods of signal analyses were applied to the data. The analyses showed that the slab has some closely spaced modes and that the modes of the floor are complex to a certain degree. The finite element models were studied with different configurations. In particular, the effect the model size, boundary conditions, material properties and potential structural discontinuities have on the dynamic response of the slab was studied. Sufficiently good agreement has been achieved between the experimental and numerical results in terms of natural frequencies and mode shapes. The acceleration amplitude responses of the numerical models were generally higher than the ones obtained from the measurements, which leads to difficulties in matching of the frequency response functions.
Håldäck i betong används idag i stor utsträckning som bjälklag i bostads- och kontorsbyggnader, liksom i parkeringsgarage och köpcentra. Håldäcksbjälklag består av prefabricerade och förspända betongelement, med cylindriska hål som sträcker sig i plattans längsriktning. Dessa konstruktionselement har fördelen, jämfört med platsgjutna betongplattor, att de har en hög hållfasthet på grund av förspänningen och att hålen möjliggör en lägre egenvikt. Dessutom gör hålen att en mindre mängd betongmaterial behövs. Dessa egenskaper ger möjligheter att bygga golv med långa spännvidder och slank design. En konsekvens av slankheten är emellertid att sådana golv har en ökad känslighet för vibrationer som orsakas av olika dynamiska belastningar. I bostads- och kontorsbyggnader orsakas vibrationer främst av mänsklig aktivitet, och därför finns det en del oro relaterad till sådana golvs brukbarhet. Dessa vibrationer är oftast inte relaterade till frågor om strukturell integritet, utan snarare till olika aspekter av boendes eller arbetares känsla av komfort. Syftet med detta examensarbete är att bidra till kunskapen om håldäcksbjälklags dynamiska beteende. En experimentell modalanalys har utförts på ett befintligt golv i en kontorsbyggnad. De dynamiska egenskaperna i form av egenfrekvenser, modformer, dämpning och frekvenssvarsfunktioner erhölls och analyserades med hjälp av dessa mätningar. Därefter utvecklades flera finita element modeller för att reproducera det experimentellt uppmätta dynamiska beteendet hos det studerade golvet. Mätningarna visade initialt något oväntade dynamiska responser från golvet. Av denna anledning applicerades mer avancerade signalanalysmetoder på datan. Analyserna visade att plattan har några moder inom ett litet frekvensintervall och att moderna till en viss grad är komplexa. De finita element modellerna studerades med olika konfigurationer. I synnerhet studerades effekten av modellstorleken, randvillkoren, materialegenskaperna och potentiella strukturella diskontinuiteter på golvets dynamiska respons. Tillräckligt bra överensstämmelse har uppnåtts mellan de experimentella och numeriska resultaten i form av egenfrekvenser och modformer. Accelerationsamplituderna för de numeriska modellerna var i allmänhet högre än de som erhölls under mätningarna, vilket leder till svårigheter att matcha frekvenssvarsfunktionerna.

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Kalluru, Mallikarjun. "One-way Coupled Hydroelastic Analysis of Aluminum Wedge Under Slamming." ScholarWorks@UNO, 2017. https://scholarworks.uno.edu/td/2414.

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The concept of using aluminum as the primary construction material for high speed ships and the hydroelastic behavior of the structure is widely gaining importance as a significant research topic in naval architecture. Aluminum is lighter than steel and hence can be predominantly used in high speed crafts which experiences significant slamming. This thesis work is focused on wedge shaped models. Free fall wedge impact is studied and a FORTRAN 90 computer program is developed to estimate the structural response of the wedge experiencing slamming by the use of matrix methods, finite element techniques and Newmark-Beta numerical time integration methods. The numerical solution is validated by comparison with the static solution. The theoretical hydrodynamic pressures which are used as input for this work was originally developed by using a flat cylinder theory [26]. The wedge drop at 0.6096 m (24 inch) drop height with an impact veloc- ity of v=3.05 m/s is based as the premise and the experimental pressure distributions measured by the pressure-transducers and the theoretical pressure predictions are used as inputs and the structural response is derived. Additionally, the response is compared for three different plate thicknesses and the results are compared against each other. The maximum deflection is comparable to the deflection evaluated from the experiment and tends to attain convergence as well. As the plate thickness reduces there tends to be a significant rise in the deflection values for the wedge plate, in the manner that when the plate thickness is halved there is a deviation of more than 75% in the deflection values as such.

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30

Bredesen, Michael H. "The Simulation & Evaluation of Surge Hazard Using a Response Surface Method in the New York Bight." UNF Digital Commons, 2015. http://digitalcommons.unf.edu/etd/568.

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Atmospheric features, such as tropical cyclones, act as a driving mechanism for many of the major hazards affecting coastal areas around the world. Accurate and efficient quantification of tropical cyclone surge hazard is essential to the development of resilient coastal communities, particularly given continued sea level trend concerns. Recent major tropical cyclones that have impacted the northeastern portion of the United States have resulted in devastating flooding in New York City, the most densely populated city in the US. As a part of national effort to re-evaluate coastal inundation hazards, the Federal Emergency Management Agency used the Joint Probability Method to re-evaluate surge hazard probabilities for Flood Insurance Rate Maps in the New York – New Jersey coastal areas, also termed the New York Bight. As originally developed, this method required many combinations of storm parameters to statistically characterize the local climatology for numerical model simulation. Even though high-performance computing efficiency has vastly improved in recent years, researchers have utilized different “Optimal Sampling” techniques to reduce the number of storm simulations needed in the traditional Joint Probability Method. This manuscript presents results from the simulation of over 350 synthetic tropical cyclones designed to produce significant surge in the New York Bight using the hydrodynamic Advanced Circulation numerical model, bypassing the need for Optimal Sampling schemes. This data set allowed for a careful assessment of joint probability distributions utilized for this area and the impacts of current assumptions used in deriving new flood-risk maps for the New York City area.

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Liu, Albert Darien. "THE EFFECT OF SENSOR MASS, SENSOR LOCATION, AND DELAMINATION LOCATION OF DIFFERENT COMPOSITE STRUCTURES UNDER DYNAMIC LOADING." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/917.

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This study investigated the effect of sensor mass, sensor location, and delamination location of different composite structures under dynamic loading. The study pertains to research of the use of accelerometers and dynamic response as a cost-effective and reliable method of structural health monitoring in composite structures. The composite structures in this research included carbon fiber plates, carbon fiber-foam sandwich panels, and carbon-fiber honeycomb sandwich panels. The composite structures were manufactured with the use of a Tetrahedron MTP-8 heat press. All work was conducted in the Cal Poly Aerospace Structures/Composites Laboratory. Initial delaminations were placed at several locations along the specimen, including the bending mode node line locations. The free vibration of the composite structure was forced through a harmonic horizontal vibration test using an Unholtz-Dickie shake system. A sinusoidal sweep input was considered for the test. The dynamic response of the composite test specimens were measured using piezoelectric accelerometers. Measurements were taken along horizontal and vertical locations on the surfaces of the composite structures. Square inch grids were marked on the surfaces to create a meshed grid system. Accelerometer measurements were taken at the center of the grids. The VIP Sensors 1011A piezoelectric accelerometer was used to measure vibration response. The measurements were then compared to response measurements taken from a PCB Piezotronics 353B04 single access accelerometer to determine the effects of sensor mass. Deviations in bending mode natural frequency and differences in mode shape amplitude became the criteria for evaluating the effect of sensor mass, sensor location, and delamination location. Changes in damping of the time response were also studied. The experimental results were compared to numerical models created using a finite element method. The experimental results and numerical values were shown to be in good agreement. The sensor mass greatly affected the accuracy and precision of vibration response measurements in the composites structures. The smaller weight and area of the VIP accelerometer helped to minimize the decrease in accuracy and precision due to sensor mass. The effect of sensor location was found to be coupled with the effect of sensor mass and the bending mode shape. The sensor location did not affect the vibration response measurements when the sensor mass was minimized. Off-center horizontal sensor placement showed the possibility of measuring vibration torsion modes. The effect of delamination changed the bending mode shape of the composite structure, which corresponded to a change in natural frequency. The greatest effect of the delamination was seen at the bending mode node lines, where the bending mode shape was most significantly affected. The effect of delamination was also dependent on the location of the delamination and the composite structure type. The results of this study provided considerations for future research of an active structural health monitoring system of composite structures using dynamic response measurements. The considerations included sensor mass reduction, sensor placement at constraints and bond areas and the presence of damping material.

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DJILALI, BERKANE LAIEB ZOHRA. "Evaluation numérique d'un coefficient de sécurité cinématique pour les barrages et les ouvrages en terre." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10193.

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Ce memoire presente une etude numerique et cinematique de la stabilite des barrages et des ouvrages en terre. Nous exposons tout d'abord une synthese de formulations des cfficients de securite etablis par les principales methodes anterieures. Nous elaborons ensuite une nouvelle approche de l'analyse de la stabilite des ouvrages en terre pour une forme de rupture circulaire. L'evaluation du cfficient de securite par cette approche ne tient pas compte, comme dans la theorie classique, de scenarios de rupture fictifs (reduction generale de la resistance mecanique du massif du sol), mais de la proximite du champ de vitesse de deplacement calcule par elements finis par rapport au champ de vitesse de deplacement de solide rigide. Cette methode peut se greffer sur un calcul par elements finis et evite la dichotomie entre les calculs en deplacement et les calculs a la rupture. La validation de cette approche se fait tout d'abord en examinant l'influence de la variation de plusieurs parametres (pente, caracteristiques mecaniques et chargement) sur le cfficient de securite cinematique. Les resultats obtenus sont ensuite compares a ceux fournis par les methodes anterieures (classiques et recentes). Nous developpons aussi une extension de l'approche cinematique de la stabilite des ouvrages en terre aux cas de lignes de glissement plus complexes. Les resultats obtenus sont confrontes d'une part a ceux fournis par la procedure cinematique dans le cas d'un glissement circulaire et d'autre part a ceux obtenus par une methode utilisant un scenario d'equilibre limite.

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Fiorin, Laura. "Seismic assessment of suspended ceilings through cyclic quasi-static tests." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3423162.

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The purpose of this work is the evaluation of the seismic behaviour of suspended ceilings by means of a combined experimental and numerical approach. As concerning the experimental aspects, nowadays the most common experimental produre applied to suspended ceilings worldwide regards shake-table tests, with a protocol defined to certify the ceilings for a determined seismic level. This methodology has some shortcomings, including the high cost and the influence of the input chosen on the experimental results. In fact, these tests have the aim to certify the product rather than providing mechanical characteristics of the specimen tested. Moreover, the results obtained with the certification process cannot be extended to similar products or geographic zones with different seismic risk. To overcome these limitations, an innovative experimental setup for monotonic and cyclic testing of suspended ceiling systems was designed, realized and applied. In order to have a complete characterization of suspended ceilings, an initial experimental campaign on inner joints was realized. These components, in fact, performed poorly in past earthquakes. In detail, 'standard' joints were compared to 'seismic' joints, specifically designed to resist to earthquake motion. Real-scale tests were then performed on the most common T-Grid suspended ceilings and other two typologies of metal ceilings with different structure. Moreover, dry-wall suspended ceilings with single and double plasterboard were tested. For each typology one monotonic and one cyclic quasi-static test were performed. Monotonic tests have the aim to identify the yielding parameters and the damage mechanisms and cyclic tests are performed according to the protocol described in FEMA 461 for cyclic quasi-static tests of non-structural components. The results allow to define the performance of suspended ceilings and to elaborate their capacity curves. As concerning the numerical part of the work, a numerical cascading approach was applied to study the uncoupled behaviour of suspended ceilings installed at different levels of buildings. Results from experimental campaign were used as input data for the numerical anlyses. Elastic linear time history analyses were performed on multi-story buildings with different vibration periods and the elastic floor response spectra were defined. Capacity curves defined experimentally and floor spectra were plotted in an ADRS (Acceleration Displacement Response Spectrum) domain in order to assess the seismic demand in terms of acceleration and displacement of suspended ceilings compared to their capacities. Dynamic analyses of suspended ceilings were conduced both in linear and non linear hypothesis and the results compared in order to assess the effectiveness of standard linear, or equivalent linear, static calculations.
Lo scopo della tesi è la valutazione del comportamento sismico di controsoffitti, tramite prove cicliche quasi statiche. La tipologia di prove più comune ad oggi, infatti, riguarda prove su tavole vibrante con un protocollo definito per certificare il prodotto per una certa azione sismica. Queste prove presentano varie limitazioni, tra cui il costo elevato e la stretta correlazione tra risultato e input scelto. Le prove infatti non hanno specifico scopo di ricerca se non l’obiettivo di certificare un prodotto, non forniscono informazioni sulle prestazioni meccaniche dei componenti testati e non permettono di estendere i risultati ottenuti ne su prodotti simili ne in zone geografiche con diverso rischio sismico. È stato quindi progettato un setup di prova innovativo in grado di realizzare prove monotone e cicliche quasi statiche su controsoffitti. Questa tipologia di prove permette di superare le limitazioni dell’attuale procedura sperimentale. Al fine di ottenere una caratterizzazione completa dei controsoffitti, sono stati testati i giunti interni, questi componenti infatti sono risultati danneggiati in seguito a eventi sismici. In particolare, sono stati testati sia giunti ‘standard’ che giunti ‘antisismici’, facenti parte di una particolare linea progettata per resistere all’azione sismica. Sono stati testati a grandezza reale sia controsoffitti con struttura a T (che rappresentano la tipologia più diffusa globalmente), che altri due controsoffitti con diversa sottostruttura metallica, infine le prove hanno riguardato anche controsoffitti con pannelli continui in cartongesso. Per ogni tipologia sono stati eseguite una prova monotona, al fine di individuare i parametri di snervamento e il meccanismo di rottura, e una prova ciclica, seguendo il protocollo indicato nelle FEMA 461 per prove cicliche quasi statiche per componenti non strutturali. I risultati ottenuti hanno permesso di definire la prestazione degli elementi testati e di elaborarne la curva di capacità. Tramite approccio numerico “a cascata”, che permette di eseguire uno studio disaccoppiato dei due elementi, è stato possibile studiare il comportamento dei controsoffitti installati a diversi piani. Sono state realizzate analisi time-history lineari elastiche su edifici multi-piano con diverso periodo di vibrazione e sono stati ricavati gli spettri di risposta al piano. Le curve di capacità dei controsoffitti, definite sperimentalmente, e gli spettri al piano sono stati definiti in un dominio ADRS (Acceleration Displacement Response Domain) al fine di valutare la domanda sismica in termini di spostamento e accellerazione in funzione della capacità dei controsoffitti.

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Susila, Gede Adi. "Experimental and numerical studies of masonry wall panels and timber frames of low-rise structures under seismic loadings in Indonesia." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/experimental-and-numerical-studies-of-masonry-wall-panels-and-timber-frames-of-lowrise-structures-under-seismic-loadings-in-indonesia(3ceb094b-4e6e-432a-b3de-3d4c306b0551).html.

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Indonesia is a developing country that suffers from earthquakes and windstorms and where at least 60% of houses are non-engineered structures, built by unskilled workers using masonry and timber. The non-engineered housing units developed in urban region are also vulnerable to seismic hazard due to the use of low quality of material and constructions method. Those structures are not resistant to extreme lateral loads or ground movement and their failure during an earthquake or storm can lead to significant loss of life. This thesis is concerned with the structural performance of Indonesian low-rise buildings made of masonry and timber under lateral seismic load. The research presented includes a survey of forms of building structure and experimental, analytical and numerical work to predict the behaviour of masonry wall and traditional timber frame buildings. Experimental testing of both masonry and timber have been carried out in Indonesia to establish the quality of materials and to provide material properties for numerical simulations. The experimental study found that the strength of Indonesia-Bali clay brick masonry are below the minimum standard required for masonry structures built in seismic regions, being at least 50% lower than the requirement specified in British Standard and Eurocode-6 (BS EN 1996-1-1:2005). In contrast, Indonesian timber materials meet the strength classes specified in British Standard/Eurocode- 5 (BS EN 338:2009) in the range of strength grade D35-40 and C35).Structural tests under monotonic and cyclic loading have been conducted on building components in Indonesia, to determine the load-displacement capacity of local hand-made masonry wall panels and timber frames in order to: (1) evaluate the performance of masonry and timber frame structure, (2) investigate the dynamic behaviour of both structures, (3) observe the effect of in-plane stiffness and ductility level, and (4) examine the anchoring joint at the base of timber frame that resists the overturning moment. From these tests, the structural ductility was found to be less than two which is below the requirement of the relevant guidelines from the Federal Emergency Management Agency, USA (FEMA-306). It was also observed that the lateral stiffness of masonry wall is much higher than the equivalent timber frame of the same height and length. The experimental value of stiffness of the masonry wall panel was found to be one-twelfth of the recommended values given in FEMA-356 and the Canadian Building code. The masonry wall provides relatively low displacement compared to the large displacement of the timber frame at the full capacity level of lateral load, with structural framing members of the latter remaining intact. The weak point of the timber frame is the mechanical joint and the capacity of slip joint governs the lateral load capacity of the whole frame. Detailed numerical models of the experimental specimens were setup in Abaqus using three-dimensional solid elements. Cohesive elements were used to simulate the mortar behaviour, exhibiting cracking and the associated physical separation of the elements. Appropriate contact definitions were used where relevant, especially for the timber frame joints. A range of available material plasticity models were reviewed: Drucker-Prager, Crystalline Plasticity, and Cohesive Damage model. It was found that the combination of Crystalline Plasticity model for the brick unit and timber, and the Cohesive Damage model for the mortar is capable of simulating the experimental load-displacement behaviour fairly accurately. The validated numerical models have been used to (1) predict the lateral load capacity, (2) determine the cracking load and patterns, (3) carry out a detailed parametric study by changing the geometric and material properties different to the experimental specimens. The numerical models were used to assess different strengthening measures such as using bamboo as reinforcement in the masonry walls for a complete single storey, and a two-storey houses including openings for doors and windows. The traditional footing of the timber structures was analysed using Abaqus and was found to be an excellent base isolation system which partly explains the survival of those structures in the past earthquakes. The experimental and numerical results have finally been used to develop a design guideline for new construction as well as recommendations for retrofitting of existing structures for improved performance under seismic lateral load.

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Nolte, Sandra, and sandra nolte@mh org au. "Approaches to the measurement of outcomes of chronic disease self-management interventions using a self-report inventory." RMIT University. Global Studies, Social Science & Planning, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080822.151606.

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Background Health education programs that are aimed at improving individuals' skills to self-manage are increasingly recognised as a critical component of chronic disease management. Despite the apparent need for such interventions, current studies show inconsistent results regarding program effectiveness, with meta-analyses indicating only marginal effects for some disease groups. A closer examination of these studies however suggests that the magnitude and inconsistency of the findings may be related to the types of outcomes that were assessed rather than specific disease groups. Where self-report measures were used, results tended to be smaller and inconsistent. It is therefore possible that current studies do not adequately reflect program effects because self-report outcomes have a high risk to be confounded by a range of potential biases. Objective The aim of this thesis was to identify and quantify the potential influence of biases in the measurement of change in chronic disease self-management interventions using self-report. Methods The research design targeted the processes that individuals undergo when filling out questionnaires and whether this has an influence on their self-report outcomes. This was achieved by developing a three-group research design. The Health Education Impact Questionnaire (heiQ) was used to collect outcomes data. While pretest questionnaires were identical across groups, three questionnaire versions were randomly distributed at posttest. One of the groups filled out traditional posttest questions (n=331), whereas the other two groups were asked to provide data in addition to posttest questions, with one group providing transition questions (n=304) and one providing retrospective pretest data (n=314). Resulting datasets were further examined for possible confounding effects through response shift and social desirability bias. Through the random allocation of the heiQs it was ensured that data were not influenced by potential intra-group effects. Results The thesis revealed that the design of the posttest questionnaire significantly influenced people's ratings of their posttest levels. In particular, when participants were asked to provide ratings of their retrospective pretest levels in addition to their posttest levels, the latter scores were significantly higher than those of participants who did not perform this additional task. Subsequent analyses however suggested that these differences could neither be explained by response shift nor by social desirability bias. Conclusions This research has provided important insight into the measurement of outcomes of chronic disease self-management interventions. While the threat to the validity of traditional pretest-posttest data due to confounding effects through response shift and social desirability biases could not be supported, the thesis has highlighted that the cognitive task that subjects are asked to perform when providing data at posttest significantly influenced their self-reported outcomes. Given that previous research has predominantly focused on other aspects of validity - such as applying control group designs to circumvent common threats to internal and external validity - this study suggests that more attention must be paid to the design of questionnaires. The thesis concludes that further research, in particular into the influence of cognitive tasks on obtained scores, is important to improve the interpretation of self-report outcomes data derived from participants of self-management interventions.

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Al-Dodoee, Omar Hashim Hassoon. "Conception et optimisation des matériaux et structures composites pour des applications navales : effet du slamming." Thesis, Brest, 2017. http://www.theses.fr/2017BRES0050/document.

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L'interaction fluide-structure vise à étudier le contact entre un fluide et un solide. Ce phénomène est très présent lors de l’impact d’une vague sur une structure ou l’inverse. La réponse de la structure peut être fortement affectée par l'action du fluide. L'étude de ce type d'interaction est motivée par le fait que les phénomènes résultants sont parfois catastrophiques pour les structures composites ou constituent dans la majorité des cas un facteur dimensionnant important. Le fluide est caractérisé par son champ de vitesse et de pression. Il exerce des forces aérodynamiques ou hydrodynamiques sur l'interface de la structure qui subit des déformations sous leurs actions. Ces déformations peuvent affecter localement le champ de l'écoulement et donc les charges appliquées. Ce cycle des interactions entre le fluide et le solide est caractéristique du phénomène de slamming. Pour une conception optimale des structures marines, la vitesse du navire est devenue un paramètre important. Par conséquent, les exigences de conception ont été optimisées par rapport au poids structurel. D'autre part, l'apparition des structures composites au cours des dernières décennies a favorisé l'exploitation de ces matériaux dans les grands projets de construction pour les applications marines et aérospatiales. Ceci est dû à la nature de leurs propriétés mécaniques, car elles présentent un rapport rigidité / poids élevé. En revanche, l'interaction entre les structures déformables et la surface libre de l'eau peut affecter le flux du fluide en contact avec la structure ainsi que et les charges hydrodynamiques estimées par rapport au corps rigide, en raison de l'apparition des effets hydro-élastiques. En outre, ces structures sont toujours soumises à des mécanismes de dommages différents et complexes sous un chargement dynamique. Pour ces raisons, la flexibilité et les modes de défaillance dans les matériaux composites présentent une complexité supplémentaire pour prédire les charges hydrodynamiques lorsqu'il y a une interaction avec un fluide (l'eau). Ceci a présenté un défi majeur pour utiliser ces matériaux dans les applications maritimes. Par conséquent, une attention particulière doit être accordée dans la phase de conception et l'analyse des performances pendant l'utilisation à vie. Les principales contributions de ce travail sont l’étude expérimentale et numérique du comportement dynamique des panneaux composites et la quantification de l'effet de la flexibilité de ces panneaux composites sur les charges hydrodynamiques et les déformations résultantes. Pour étudier ces effets, des panneaux composites stratifiés et sandwichs avec deux rigidités différentes sont soumis à diverses vitesses d'impact à l'aide d'une machine de choc équipée d'un système de contrôle de la vitesse. La résistance dynamique a été analysée en termes de charges hydrodynamiques, de déformations dynamiques et de mécanismes de défaillance pour différentes vitesses d'impact. L'analyse des résultats expérimentaux a montré que l’effort maximal augmente avec l’augmentation de la flexibilité des panneaux. D'autre part, le modèle numérique de tossage a été implémenté dans le logiciel Abaqus / Explicit basé sur l'approche du modèle Couplé Euler Lagrange (CEL). En outre, différents modes de défaillance des matériaux composites ont été développés et implémentés à l'aide d'une subroutine « VUMAT » définie par l'utilisateur et mis en œuvre dans le code de calcul éléments finis. Pour couvrir tous les modes de défaillance possibles dans les structures composites, l’implémentation de l’endommagement comprend : la rupture intralaminar, la décohésion de l'interface peau / âme et le cisaillement de l’âme. La confrontation des résultats expérimentaux avec les modèles numériques sur la prédiction de la force hydrodynamique et de la déformation du panneau valide l’approche adoptée
Generally, when marine vessels encounter the water surface on entry and subsequently re-enter the water at high speed (slamming), this can subject the bottom section of the vessels to both local and global effects and generate unwanted vibrations in the structure, especially over very short durations. In marine design, the vessel speed has become an important aspect for optimal structure. Therefore, design requirements have been optimized in relation to the structural weight. In other hand, the appearance of the composite structures in the last decades has encouraged the exploitation of these structures in major construction projects for lightweight marine and aerospace applications. This is due to the nature of their mechanical properties which shows a high stiffness-to-weight ratio. In contrast, the interaction between deformable structures and free water surface can be modified the fluid flow and changed the estimated hydrodynamic loads comparing with rigid body, due to appearance of hydroelastic effects. Moreover, these structures are always subject to different and complex damage mechanisms under dynamic loading. For these reasons, the flexibility and the damage failure modes in composite materials introduce additional complexity for predicting hydrodynamic loads when interactive with water. This considered a key challenge to use these materials in marine applications. Therefore, special attention must be taken in the design phase and the analysis of performances during lifetime use. The main contributions of this work are the experimental and numerical study of the dynamic behavior of composite panels and the quantification of the effect of the flexibility of these structures on the hydrodynamic loads and the resulting deformations. To study these effects, laminate composite and sandwich panels with two different rigidities and subjected to various impact velocities have been investigated experimentally using high speed shock machine with velocity control system. The dynamic resistance was analysed in terms of hydrodynamic loads, dynamic deformation and failure mechanisms for different impact velocities. The general analysis of experiment results were indicated that more flexible panel has a higher peak force as velocity increases compared with higher stiffness panels. On the other hand, the slamming model was implemented in Abaqus/Explicit software based on Coupled Eulerian Lagrangian model approach (CEL). In addition, different damage modes are developed and constructed using a user-defined material subroutine VUMAT and implemented in Finite element method, including the intralaminar damage, debonding in skin/core interface, and core shear to cover all possible damage modes throughout structures. The numerical model gave a good agreement results in judging with experimental data for prediction of the hydrodynamic force and panel deformation. Additionally, this study gives qualitative and quantitative data which provides clear guidance in design phase and the evolution of performances during lifetime of composite structures, for marine structure designers

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Saïd, Didier. "Étude théorique et numérique des vibrations de structures soumises à des chocs pyrotechniques." Cachan, Ecole normale supérieure, 1998. http://www.theses.fr/1998DENS0020.

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L'étude s'inscrit dans le cadre de la prévision des niveaux vibratoires induits par les chocs pyrotechniques lors de la phase de séparation des étages du lanceur Ariane 5, et plus particulièrement de la prévision des niveaux vibratoires dans la case a équipements. On développe une approche simplifiée permettant de déterminer la réponse dynamique de la structure à partir du calcul de matrices de rigidité dynamique exactes. Cette approche est réservée a des structures de type guides d'ondes dans lesquelles la direction de propagation des ondes est connue. On s'intéresse également a la prise en compte de liaisons entre structures ; on montre qu'il est possible de déterminer la matrice de rigidité dynamique des liaisons a partir de la connaissance des coefficients de réflexion et de transmission des ondes et des relations force-déplacement dans les éléments relies a la liaison.

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Pitot, de la Beaujardiere Jean-Francois Philipe. "Numerical simulation of the structural response of a composite rocket nozzle during the ignition transient /." 2009. http://hdl.handle.net/10413/925.

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Pitot, de la Beaujardiere Jean-Francois Philippe. "Numerical simulation of the structural response of a composite rocket nozzle during the ignition transient." Thesis, 2009. http://hdl.handle.net/10413/778.

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The following dissertation describes an investigation of the structural response behaviour of a composite solid rocket motor nozzle subjected to thermal and pressure loading during the motor ignition period, derived on the basis of a multidisciplinary numerical simulation approach. To provide quantitative and qualitative context to the results obtained, comparisons were made to the predicted aerothermostructural response of the nozzle over the entire motor burn period. The study considered two nozzle designs – an exploratory nozzle design used to establish the basic simulation methodology, and a prototype nozzle design that was employed as the primary subject for numerical experimentation work. Both designs were developed according to fundamental solid rocket motor nozzle design principles as non-vectoring nozzles for deployment in medium sized solid rocket booster motors. The designs feature extensive use of spatially reinforced carbon-carbon composites for thermostructural components, complemented by carbon-phenolic composites for thermal insulation and steel for the motor attachment substructures. All numerical simulations were conducted using the ADINA multiphysics finite element analysis code with respect to axisymmetric computational domains. Thermal and structural models were developed to simulate the structural response of the exploratory nozzle design in reference to the instantaneous application of pressure and thermal loading conditions derived from literature. Ignition and burn period response results were obtained for both quasi-static and dynamic analysis regimes. For the case of the prototype nozzle design, a flow model was specifically developed to simulate the flow of the exhaust gas stream within the nozzle, for the provision of transient and steady loading data to the associated thermal and structural models. This arrangement allowed for a more realistic representation of the interaction between the fluid, thermal and structural fields concerned. Results were once again obtained for short and long term scenarios with respect to quasi-static and dynamic interpretations. In addition, the aeroelastic interaction occurring between the nozzle and flow field during motor ignition was examined in detail. The results obtained in the present study provided significant indications with respect to a variety of response characteristics associated with the motor ignition period, including the magnitude and distribution of the displacement and stress responses, the importance of inertial effects in response computations, the stress response contributions made by thermal and pressure loading, the effect of loading condition quality, and the bearing of the rate of ignition on the calculated stress response. Through comparisons between the response behaviour predicted during the motor ignition and burn periods, the significance of considering the ignition period as a qualification and optimisation criterion in the design of characteristically similar solid rocket motor nozzles was established.
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.

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Sofiani, Farid Mehri. "Numerical study on Structural response of dental restorations using finite element method and meshless methods." Master's thesis, 2018. https://repositorio-aberto.up.pt/handle/10216/118167.

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Sofiani, Farid Mehri. "Numerical study on Structural response of dental restorations using finite element method and meshless methods." Dissertação, 2018. https://repositorio-aberto.up.pt/handle/10216/118167.

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De, Candia SM. "Experimental and numerical investigations into the underwater explosion induced whipping response of submerged platforms." Thesis, 2019. https://eprints.utas.edu.au/31703/1/De_Candia_whole_thesis.pdf.

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This thesis reports the findings of an experimental and numerical investigation into the whipping response of a submerged platform, due to loading from near-field, non-contact underwater explosion (UNDEX) events. The experimental investigation examined the whipping response of a generic submerged platform subjected to UNDEX. Eight scenarios were investigated, using different explosive charge sizes, longitudinal, and transverse stand-off locations, to explore the effects of these variables on the platform’s whipping response, and to provide validation data for the numerical investigation. It was found that UNDEX stand-off locations near the anti-node of the first bending mode shape induced the most severe whipping responses, while stand-offs near the node of the first bending mode shape had greatly reduced whipping responses. A numerical model was developed and validated against the experimental results, using incident pressure and strain measurements. Three numerical studies were conducted with the validated numerical model, investigating the effects of additional stand-off distances at the previously explored longitudinal stand-off locations, the whipping response from an intermediate charge size, and the effects of the UNDEX bubble loading on the whipping response by using a shock-only loading model. From these studies, the following novel contributions were made: The stand-off distance was found to only affect the whipping severity while the charge size and stand-off location determined the modal contributions of the whipping response. A comparison of the peak whipping response to the bubble pressure impulse suggests that three distinct forms of whipping could be induced, and these can be determined by the proximity of the UNDEX stand-off location to the nodes and anti-nodes of the platform’s first bending mode shape. These were classified as critical, resilient, and general whipping responses. The critical whipping response occurred when the UNDEX stand-off location was near the anti-node of the first bending mode shape. This was characterised by a dominant response of the first bending mode and minimal contribution from other bending modes in the overall response. The severity of this response increased nonlinearly as the bubble impulse increased and when the bubble pulsation frequency was similar to the first bending mode frequency. This is the most severe form of UNDEX induced whipping. The resilient whipping response occurred when the UNDEX stand-off location was near the node of the first bending mode shape. This was characterised by minimal contribution of the first bending mode compared to others in the overall response. From these scenarios, the bubble loading had minimal effect on the whipping response. This was confirmed from good correlation in comparisons of the strain responses from experimental measurements and the results from the numerical shock-only loading study. This is the least severe form of UNDEX induced whipping and the most desirable outcome from an unavoidable UNDEX threat. The general whipping response occurred when the UNDEX stand-off location was between the nodes and anti-nodes of the first bending mode shape. This was characterised by similar contributions of multiple bending mode responses in the overall response. The severity from this response increased linearly for increases in the bubble impulse. It is suggested this is the most likely form of UNDEX induced whipping to occur, based on the large number of variables involved with UNDEX loading and platform response scenarios. Current analysis methodologies are able to identify the resilient whipping response but some methods that focus on the shock response of a platform may not identify the critical and general whipping responses. This was demonstrated by comparison of the experimental measurements to a numerical shock-only loading models for the most severe UNDEX scenarios, where shock-only loading and response assumptions under-predicted the whipping response by 39 % and 54 % for the critical and general whipping responses respectively. The relative increase in the severity of the whipping response from a reduction in the stand-off distance was consistent for all similar forms of whipping. This suggests that the whipping severity from many different stand-off distances can be approximated through analysis of only a few scenarios at different stand-off locations on a specific naval platform. It is suggested that this knowledge may allow a rapid assessment tool to be developed that could determine a platform’s survivability from a wide variety of UNDEX scenarios. The trends from each form of whipping severity compared to bubble pressure impulse were examined with limited extrapolation. This suggested that four whipping response analysis regimes exist: far-field elastic, near-field and non-contact elastic, non-contact plastic, and contact damage. Exact limits of these regimes were not identified, and all are promising areas for further investigation.

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Sheehan, Therese, Xianghe Dai, T. M. Chan, and Dennis Lam. "Structural response of concrete-filled elliptical steel hollow sections under eccentric compression." 2012. http://hdl.handle.net/10454/5916.

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The purpose of this research is to examine the behaviour of elliptical concrete-filled steel tubular stub columns under a combination of axial force and bending moment. Most of the research carried out to date involving concrete-filled steel sections has focussed on circular and rectangular tubes, with each shape exhibiting distinct behaviour. The degree of concrete confinement provided by the hollow section wall has been studied under pure compression but remains ambiguous for combined compressive and bending loads, with no current design provision for this loading combination. To explore the structural behaviour, laboratory tests were carried out using eight stub columns of two different tube wall thicknesses and applying axial compression under various eccentricities. Moment-rotation relationships were produced for each specimen to establish the influence of cross-section dimension and axis of bending on overall response. Full 3D finite element models were developed, comparing the effect of different material constitutive models, until good agreement was found. Finally, analytical interaction curves were generated assuming plastic behaviour and compared with the experimental and finite element results. Ground work provided from these tests paves the way for the development of future design guidelines on the member level.

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"Effects of Structural Uncertainty on the Dynamic Response of Nearly-Straight Pipes Conveying Fluid: Modeling and Numerical Validation." Master's thesis, 2017. http://hdl.handle.net/2286/R.I.45028.

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abstract: This investigation is focused on the consideration of structural uncertainties in nearly-straight pipes conveying fluid and on the effects of these uncertainties on the dynamic response and stability of those pipes. Of interest more specifically are the structural uncertainties which affect directly the fluid flow and its feedback on the structural response, e.g., uncertainties on/variations of the inner cross-section and curvature of the pipe. Owing to the complexity of introducing such uncertainties directly in finite element models, it is desired to proceed directly at the level of modal models by randomizing simultaneously the appropriate mass, stiffness, and damping matrices. The maximum entropy framework is adopted to carry out the stochastic modeling of these matrices with appropriate symmetry constraints guaranteeing that the nature, e.g., divergence or flutter, of the bifurcation is preserved when introducing uncertainty. To support the formulation of this stochastic ROM, a series of finite element computations are first carried out for pipes with straight centerline but inner radius varying randomly along the pipe. The results of this numerical discovery effort demonstrate that the dominant effects originate from the variations of the exit flow speed, induced by the change in inner cross-section at the pipe end, with the uncertainty on the cross-section at other locations playing a secondary role. Relying on these observations, the stochastic reduced order model is constructed to model separately the uncertainty in inner cross-section at the pipe end and at other locations. Then, the fluid related mass, damping, and stiffness matrices of this stochastic reduced order model (ROM) are all determined from a single random matrix and a random variable. The predictions from this stochastic ROM are found to closely match the corresponding results obtained with the randomized finite element model. It is finally demonstrated that this stochastic ROM can easily be extended to account for the small effects due to uncertainty in pipe curvature.
Dissertation/Thesis
Masters Thesis Mechanical Engineering 2017

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Wang, Zhiyu. "Experimental and numerical study of structural frames with semi-interlocking masonry (SIM) infill panels." Thesis, 2017. http://hdl.handle.net/1959.13/1349863.

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Research Doctorate - Doctor of Philosophy (PhD)
Dry stack masonry is built without mortar. These masonry structures have attracted interest in the construction industry because they are easy to build. This potentially improves productivity and lowers costs, compared to traditional mortar-jointed masonry construction. Masonry walls are often used in framed structures as infill panels. To improve the seismic behaviour of these structures, a novel mortarless masonry building system based on semi-interlocking masonry (SIM) has been developed at the Centre for Infrastructure Performance and Reliability, University of Newcastle, Australia. In this system, the SIM units are capable of relative sliding in-plane when constructed as a panel, and locked against relative movement out-of-plane. Compared with traditional unreinforced masonry (URM), SIM can increase earthquake energy dissipation through friction between bricks. Under seismic loads, SIM panels do not detrimentally interfere with natural frame vibration but contribute positively to earthquake resistance, mainly by increasing damping. Therefore, SIM panels can be used in earthquake resistant framed structures as infill panels, and act as energy dissipation devices. In this thesis, an experimental and numerical study was conducted to investigate the nonlinear static and seismic behaviour of SIM infill panels. The results show that SIM infill panels are a viable alternative to traditional URM infill panels in seismically active areas. In the experimental part of the study, in-plane tests were performed on a steel frame with a topological SIM panel to evaluate the structural potential and the cyclic behaviour of the panels. The in-plane force-displacement behaviour of the structure, its stiffness degradation, energy dissipation, and its response mechanisms were studied and compared to the behaviour of the bare frame. The results indicate that the gap between the frame and the top of the panel significantly influences the composite response of the structure. Next, the responses of a steel frame with a topological SIM panel, and an RC frame with a prototype SIM panel were compared in terms of their crack patterns, hysteretic behaviour and energy dissipation. The prototype SIM panels and topological SIM panels had similar hysteretic behaviour, as well as the same energy dissipation mechanisms. They therefore produced similar seismic response capacities. Then, numerical models were developed in SeismoStruct. This program uses the equivalent diagonal strut model for masonry panels. This model was developed for traditional URM panels based on multiple experimental tests. However, conventional compressive struts do not form in SIM panels. SIM panels provide some resistance to diagonal compression and shear but this resistance relates to frictional forces between bricks and the frame. They are physically different to URM panels. No existing models that reflect the actual physical behaviour of SIM panels were located. In the numerical part of this study, the equivalent strut model was used with parameters adjusted to match the available experimental results for SIM. The model was calibrated and verified by comparing these results with those of the bare RC frame, the RC frame infilled with a prototype SIM panel, the RC frame infilled with a traditional URM panel, the bare steel frame and the steel frame with a topological SIM panel. In addition, model calibration and verification was also conducted for the following case studies: multistorey bare RC frame, multistorey RC frame with traditional URM infill panels and multistorey bare steel frame. Finally, numerical simulations were conducted to evaluate the nonlinear static and seismic behaviour of the SIM infill panels on the multistorey bare RC and steel frames, the multistorey frames with SIM panels with a gap between the top of the panels and the frame, the multistorey frames with SIM panels without a gap between the top of the panels and the frame, and the multistorey frames with traditional URM panels. The results show that the RC frame and the steel frame with SIM infill panels have structural properties which, in combination, help them to improve structural ductility and reduce the base shear force during extreme earthquake events. The experimental tests and numerical modelling conducted for this study were based on prototype SIM panels and topological SIM panels. Further research is needed to investigate how mechanical SIM panels with dowels react in out-of-plane tests and numerical models. The current models are limited to two-dimensional analyses of in-plane behaviour of framed structures with SIM infill panels. Three-dimensional models based on the actual observed behaviour of SIM panels need to be developed to capture the actual physical in-plane and out-of-plane behaviour of these panels.

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46

(7874897), Ryan T. Whelchel. "Evaluation and Structural Behavior of Deteriorated Precast, Prestressed Concrete Box Beams." Thesis, 2019.

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Adjacent precast, prestressed box beam bridges have a history of poor performance and have been observed to exhibit common types of deterioration including longitudinal cracking, concrete spalling, and deterioration of the concrete top flange. The nature of these types of deterioration leads to uncertainty of the extent and effect of deterioration on structural behavior. Due to limitations in previous research and understanding of the strength of deteriorated box beam bridges, conservative assumptions are being made for the assessment and load rating of these bridges. Furthermore, the design of new box beam bridges, which can offer an efficient and economical solution, is often discouraged due to poor past performance. Therefore, the objective of this research is to develop improved recommendations for the inspection, load rating, and design of adjacent box beam bridges. Through a series of bridge inspections, deteriorated box beams were identified and acquired for experimental testing. The extent of corrosion was determined through visual inspection, non-destructive evaluation, and destructive evaluation. Non-destructive tests (NDT) included the use of connectionless electrical pulse response analysis (CEPRA), ground penetrating radar (GPR), and half-cell potentials. The deteriorated capacity was determined through structural testing, and an analysis procedure was developed to estimate deteriorated behavior. A rehabilitation procedure was also developed to restore load transfer of adjacent beams in cases where shear key failures are suspected. Based on the understanding of deterioration developed through study of deteriorated adjacent box beam bridges, improved inspection and load rating procedure are provided along with design recommendations for the next generation of box beam bridges.

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47

Singh, Vikas Pratap. "Response And Reliability Analyses Of Soil Nail Walls." Thesis, 2009. http://hdl.handle.net/2005/1108.

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In the present thesis, studies on the response of soil nail walls subjected to static and seismic conditions using finite element based numerical simulations and the principle of reliability analysis have been performed. The basic methodology constitutes the study of various aspects of soil nail walls such as analyses of important external, internal and facing failure modes, development of axial forces, and displacement observations by considering various typical and prototype cases. For better understanding and presentation, subject matter of the thesis is organised in the following ten chapters. Chapter 1 of the thesis provides an introduction to the soil nailing technique and highlights some of its applications, advantages, and limitations. Chapter 2 provides a detailed review of existing literature on the soil nailing technique. Chapter 3 provides a detailed overview the various methodologies adopted in the thesis for the analyses and response study of the soil nail walls. Chapter 4 deals with the important aspects related to the plane strain finite element based numerical simulations of soil nail walls. In particular, addresses the implications of the use of advanced soil models and the consideration of bending stiffness of soil nails on the overall response of the soil nail walls. Chapter 5 presents finite element simulations based appraisal of the conventional design methodology of soil nail walls, and studies the response of typical soil nail walls under static and seismic conditions. Chapter 6 presents a reliability based study of the important failure modes of soil nail walls subjected to the variability in in-situ soil parameters, and highlights the importance of reliability analysis in context of soil nail walls. Chapter 7 proposes load and resistance factor design (LRFD) methodology in context of soil nail walls, and highlights the need in advancement of the existing conventional design methodology for soil nail walls. Chapter 8 illustrates the use of factorial design of experiment methodology in developing regression models for stability criteria analysis of soil nail walls. Chapter 9 proposes methods for assessing the adequacy of field pullout tests performed in accordance with the prevalent soil nailing guidelines. Further, a reliability based methodology is proposed for the evaluation and various applications of field pullout tests results have been illustrated. Chapter 10 summarises the various studies reported in the thesis and provides a few important conclusions. It is believed that the various studies reported in the thesis contribute to the enhancement of the existing knowledge on soil nailing technique, advancement in the analysis and design methods, and in general, are useful to the soil nailing practice.

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48

Garaga, Arunakumari. "Factors Affecting The Static And Dynamic Response Of Jointed Rock Masses." Thesis, 2008. http://hdl.handle.net/2005/772.

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Infrastructure is developing at an extremely fast pace which includes construction of metros, underground storage places, railway bridges, caverns and tunnels. Very often these structures are found in or on the rock masses. Rock masses are seldom found in nature without joints or discontinuities. Jointed rocks are characterized by the presence of inherent discontinuities of varied sizes with different orientations and intensities, which can have significant effect on their mechanical response. Constructions involving jointed rocks often become challenging jobs for Civil Engineers as the instability of slopes or excavations in these jointed rocks poses serious concerns, sometimes leading to the failure of structures built on them. Experimental investigations on jointed rock masses are not always feasible and pose formidable problems to the engineers. Apart from the technical difficulties of extracting undisturbed rock samples, it is very expensive and time consuming to conduct the experiments on jointed rock masses of huge dimensions. The most popular methods of evaluating the rock mass behaviour are the Numerical methods. In this thesis, numerical modelling of jointed rock masses is carried out using computer program FLAC (Fast Lagrangian Analysis of Continua). The objective of the present study is to study the effect of various joint parameters on the response of jointed rock masses in static as well as seismic shaking conditions. This is achieved through systematic series of numerical simulations of jointed rocks in triaxial compression, in underground openings and in large rock slopes. This thesis is an attempt to study the individual effect of different joint parameters on the rock mass behaviour and to integrate these results to provide useful insight into the behaviour of jointed rock mass under various joint conditions. In practice, it is almost impossible to explore all of the joint systems or to investigate all their mechanical characteristics and implementing them explicitly in the model. In these cases, the use of the equivalent continuum model to simulate the behaviour of jointed rock masses could be valuable. Hence this approach is mainly used in this thesis. Some numerical simulations with explicitly modelled joints are also presented for comparison with the continuum modelling. The applicability of Artificial Neural Networks for the prediction of stress-strain response of jointed rocks is also explored. Static, pseudo-static and dynamic analyses of a large rock slope in Himalayas is carried out and parametric seismic analysis of rock slope is carried out with varying input shaking, material damping and shear strength parameters. Results from the numerical studies showed that joint inclination is the most influencing parameter for the jointed rock mass behaviour. Rock masses exhibit lowest strength at critical angle of joint inclination and the deformations around excavations will be highest when the joints are inclined at an angle close to the critical angle. However at very high confining pressures, the influence of joint inclination gets subdued. Under seismic base shaking conditions, the deformations of rock masses largely depend on the acceleration response with time, frequency content and duration rather than the peak amplitude or the magnitude of earthquake. All these aspects are discussed in the light of results from numerical studies presented in this thesis.

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Stephen, D., Dennis Lam, J. Forth, J. Ye, and K. D. Tsavdaridis. "An evaluation of modelling approaches and column removal time on progressive collapse of building." 2018. http://hdl.handle.net/10454/16642.

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Yes
Over the last few decades, progressive collapse disasters have drawn the attention of codified bodies around the globe; as a consequence, there has been a renewed research interest. Structural engineering systems are prone to progressive collapse when subjected to abnormal loads beyond the ultimate capacity of critical structural members. Sudden loss of critical structural member(s) triggers failure mechanisms which may result in a total or partial collapse of the structure proportionate or disproportionate to the triggering event. Currently, researchers adopt different modelling techniques to simulate the loss of critical load bearing members for progressive collapse assessment. GSA guidelines recommend a column removal time less than a tenth of the period of the structure in the vertical vibration mode. Consequently, this recommendation allows a wide range of column removal time which produces inconsistent results satisfying GSA recommendation. A choice of a load time history function assumed for gravity and the internal column force interaction affects the response of the structure. This paper compares different alternative numerical approaches to simulate the sudden column removal in frame buildings and to investigate the effect of rising time on the structural response.

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50

Siruvole, Sandeep Kumar. "Evaluation of the occupant response and structural damage according to the newly proposed pole test under Federal Motor Vehicle Safety Standard side impact regulation." Thesis, 2007. http://hdl.handle.net/10057/1173.

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Every year around the world various types of automobile accidents occur, out of which side impact vehicular collisions are the most severe. Of these, side crashes into fixed narrow objects like trees, poles account for quarter percent of total deaths and serious injuries. Moreover these side impacts present a difficult problem for improving automotive crashworthiness because of the limited crushable zone between the vehicle occupant and the intruding door structure. To improve the automotive safety in side impacts a new pole test has been proposed under Federal Motor Vehicle Safety Standard (FMVSS) 214 to make the existing regulation more comprehensive in addressing the critical head and neck injuries in addition to thoracic and pelvis injuries. In this thesis, a finite element model of the Ford Taurus and Moving Deformable Barrier (MDB) as developed by National Crash Analysis Center (NCAC) has been used for the impact analysis. The US DOT-SID side impact dummy taken from MADYMO dummy database has been used as the vehicle occupant and the rigid pole modeled in MSC. Patran software as the narrow object. Computer Simulations have been analyzed according to the new proposed pole test and (FMVSS) 214 regulation. The critical injury values, the occupant kinematics and the structural damage have been compared justifying the need for the new pole test for improving the occupant safety.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.

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