Дисертації з теми "Ground structures"
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1
Trygstad, Steinar. "Structural Behaviour of Post Tensioned Concrete Structures : Flat Slab. Slabs on Ground." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2001. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-114.
Повний текст джерелаАнотація:
In this investigation strength and structural behaviour of prestressed concrete is studied with one full scale test of one flat slab, 16000 mm x 19000 mm, and three slabs on ground each 4000 mm x 4000 mm with thickness 150 mm. The flat slab was constructed and tested in Aalesund. This slab has nine circular columns as support, each with diameter 450 mm. Thickness of this test slab was 230 mm and there were two spans in each direction, 2 x 9000 mm in x-direction and 2 x 7500 mm in y-direction from centre to centre column. The slab was reinforced with twenty tendons in the middle column strip in y-direction and eight tendons in both outer column strips. In x-direction tendons were distributed with 340 mm distance. There were also ordinary reinforcement bars in the slab. Strain gauges were welded to this reinforcement, which together with the deflection measurements gives a good indication of deformation and strains in the structure.
At a live load of 6.5 kN/m2 shear failure around the central column occurred: The shear capacity calculated after NS 3473 and EuroCode2 was passed with 58 and 69 %, respectively. Time dependent and non-linear FE analyses were performed with the program system DIANA. Although calculated and measured results partly agree well, the test show that this type of structure is complicated to analyse by non-linear FEM.
Prestressed slabs on ground have no tradition in Norway. In this test one reinforced and two prestressed slabs on ground were tested and compared to give a basis for a better solution for slabs on ground. This test was done in the laboratory at Norwegian University of Science and Technology in Trondheim. The first slab is reinforced with 8 mm bars in both directions distributed at a distance of 150 mm in top and bottom. Slab two and three are prestressed with 100 mm2 tendons located in the middle of slab thickness, and distributed at a distance of 630 mm in slab two and 930 mm in slab three. Strain gauges were glued to the reinforcement in slab one and at top and bottom surface of all three slabs. In slab two and three there were four load cells on the tendons.
Each slab were loaded with three different load cases, in the centre of slab, at the edge and finally in the corner. This test shows that stiffness of sub-base is one of the most important parameters when calculating slabs on ground. Deflection and crack load level depends of this parameter. Since the finish of slabs on ground is important, it can be more interesting to find the load level when cracks start, than deflection for the slab. It is shown in this test that crack load level was higher in prestressed slabs than in reinforced slab. There was no crack in the top surface with load in the centre, but strain gauges in the bottom surface indicate that crack starts at a load of 28 kN in the reinforced slab, and 45 kN in the prestressed slabs. Load at the edge give a crack load of 30 kN in reinforced slab, 45 kN and 60 kN in prestressed slabs. The last load case gives crack load of 30 kN in reinforced slab, 107 kN and 75 kN in prestressed slabs. As for the flat slab, FE analyses were performed for all of the three slabs on ground, and analyses shows that a good understanding of parameters like stiffness of sub-base and tension softening model, is needed for correct result of the analyses.
2
Barlow, Mark S. (Mark Steven). "Modeling and ground modal identification of space structures." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/43247.
Повний текст джерела
3
Annam, Kaushik. "Design of Bandstop Filters Using Defected Ground Structures." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1438420662.
Повний текст джерела
4
Hassani, Nezhad Gashti E. (Ehsan). "Thermo-mechanical behaviour of ground-source thermo-active structures." Doctoral thesis, Oulun yliopisto, 2016. http://urn.fi/urn:isbn:9789526214061.
Повний текст джерелаАнотація:
Abstract High energy prices and new environmental policies have made geothermal energy increasingly popular. The EU, including Finland, aims to increase the use of renewable energy resources and reduce carbon emissions. Geothermal energy pile foundations, so-called energy piles, are considered a viable alternative technology for producing energy instead of traditional methods. Geothermal heat pump systems are economically efficient and renewable environmentally friendly energy production systems in which the ground acts as a heat source in winter and as a heat sink in summer. Energy piles are economical systems, as they act as dual-purpose structures in energy production and load transfer from buildings to the ground, avoiding extra expenses in ground boring solely for energy production. However, use of ground heat exchangers (GHE) for energy production in energy piles can result in temperature variations in the pile shaft and surrounding soil, in turn affecting the thermo-mechanical behaviour of pile shaft and soil in both structural and geotechnical terms. Despite large numbers of energy piles being installed, there is still a lack of reliable information and experience about the thermo-mechanical behaviour of these structures and their energy efficiency in cold climates. This thesis investigated the efficiency performance of energy pile foundations and their productivity in cold climates by considering different groundwater flow effects and short-term imbalanced seasonal thermal loadings. The structural and geotechnical bearing capacity of different types of energy piles fitted with GHEs were also evaluated, using numerical models, and the possibility of collapse due to use of thermal systems was examined. Use of the model to compare the performance of different GHEs in terms of their efficiency revealed that at a particular fluid flow rate, double U-tube systems had greater productivity than other systems tested. The results also indicated that using energy piles under medium groundwater flow can improve the productivity of systems by around 20% compared with saturated conditions with no groundwater flow. It was also concluded that in a design context, the structural bearing capacity of piles needs to be reduced due to the additional thermal stresses induced by heating/cooling pile operationsTiivistelmä Kasvaneet energiakustannukset ja kiristyneet ympäristösäädökset ovat lisänneet geotermisten energiaratkaisujen suosiota. EU, mukaan lukien Suomi, on asettanut tavoitteekseen lisätä uusiutuvien energialähteiden käyttöä ja vähentää hiilidioksidipäästöjä. Geotermistä energiaa hyödyntävä paaluperustukset, niin kutsutut energiapaalut, tarjoavat uudenlaisen teknologian vähäpäästöisen energian tuottamiseen. Geotermiset lämpöpumppujärjestelmät, maalämpöpumput, ovat taloudellisia ja ympäristöystävällisiä energiantuotantomenetelmiä, jotka talviaikaan siirtävät maaperään varastoitunutta energiaa rakennuksen lämmittämiseen ja vastaavasti jäähdyttävät rakennusta kesällä siirtämällä lämpöä maaperään. Energiapaalujen taloudellisuus syntyy siitä, että ne pystyvät palvelemaan rakennusta kahdessa roolissa. Ne ovat osa rakennuksen energiajärjestelmää ja toimivat samalla myös kantavana rakenteena, joka siirtää rakennuksen kuormia perustuksilta maaperään. Lämpöpumppujärjestelmän kytkeminen paaluihin voi johtaa lämpötilan vaihteluun paaluissa sekä niitä ympäröivässä maaperässä, mikä puolestaan vaikuttaa paalujen ja maaperän lämpömekaanisiin, rakenteellisiin sekä geoteknisiin ominaisuuksiin. Vaikka energiapaaluja on asennettu jo paljon, ei paalujen lämpömekaanisesta käyttäytymisestä tai energiatehokkuudesta kylmien ilmastojen alueilla ole vielä paljoa tutkittua tietoa. Tässä väitöstutkimuksessa selvitettiin numeerisesti energiapaalujen rakennuspaikan pohjaolosuhteista riippuvaa tuottopotentiaalia Skandinaavisissa olosuhteissa ja ilmastossa. Tarkastelut kohdistuivat erityisesti pohjavesivirtauksen sekä vuodenaikojen ja ilman lämpötilan vaihtelun vaikutuksiin. Tutkimuksessa arvioitiin myös paalujen lämpötilan vaihtelujen vaikutuksia paalujen geoteknisiin ja rakenteellisiin ominaisuuksia sekä kestävyyteen. Numeeristen simulaatiotulosten perusteella betonipaaluun asennetun U-putkirakenteen avulla saavutetaan paras tuottopotentiaali. Tulokset osoittivat, että kohtalainen pohjaveden virtaus parantaa systeemin tuottoa noin 20 % verrattuna tilanteeseen, jossa vedellä kyllästetyssä maassa ei tapahdu pohjaveden virtausta. Analyysitulokset osoittavat myös, että paalujen lämpötilavaihteluista aiheutuvat lisäjännitykset vähentävät paalujen kantokykyä, mikä tulee ottaa huomioon paalujen mitoituksessa
5
Crawford, James MacKenzie. "Ground testing and model updating for flexible space structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ63579.pdf.
Повний текст джерела
6
Boxill, Lois E. C. "Foundation remediation of existing structures using ground densification methods." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/21792.
Повний текст джерела
7
Tsioulou, Alexandra. "Simulated ground motions for seismic risk assessment of structures." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10062053/.
Повний текст джерелаАнотація:
The recent advances in computational efficiency and the scarcity/absence of recorded ground motions for specific seismicity scenarios have led to an increasing interest in the use of ground motion simulations for seismic hazard analysis, structural demand assessment through response-history analysis, and ultimately seismic risk assessment. Two categories of ground motion simulations, physics-based and stochastic site-based are considered in this study. Physics-based ground motion simulations are generated using algorithms that solve the fault rupture and wave propagation problems and can be used for simulating past and future scenarios. Before being used with confidence, they need to be validated against records from past earthquakes. The first part of the study focuses on the development of rating/testing methodologies based on statistical and information theory measures for the validation of ground motion simulations obtained through an online platform for past earthquake events. The testing methodology is applied in a case-study utilising spectral-shape and duration-related intensity measures (IMs) as proxies for the nonlinear peak and cyclic structural response. Stochastic site-based ground motion simulations model the time-history at a site by fitting a statistical process to ground motion records with known earthquake and site characteristics. To be used in practice, it is important that the output IMs from the developed time-histories are consistent with these prescribed at the site of interest, something that is not necessarily guaranteed by the current models. The second part of the study presents a computationally efficient framework that addresses the modification of stochastic ground motion models for given seismicity scenarios with a dual goal of matching target IMs for specific structures, while preserving desired trends in the physical characteristics of the resultant time-histories. The modification framework is extended to achieve a match to the full probability model of the target IMs. Finally, the proposed modification is validated by comparison to seismic demand of hazard-compatible recorded ground motions. This study shows that ground motion simulation is a promising tool that can be used for many engineering applications.
8
Chan, Elim. "Radiation and scattering of structures above perfect and imperfect ground." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5204.
Повний текст джерела
9
Cropley, Ford. "Coherent vortical structures in the atmospheric boundary layer near ground." Thesis, Cranfield University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281042.
Повний текст джерела
10
Wu, Shuanglan. "Near-fault Ground Motions for Seismic Design of Bridge Structures." Kyoto University, 2018. http://hdl.handle.net/2433/232017.
Повний текст джерела
11
Koukleri, Stavroula. "Inelastic earthquake response and design of multistorey torsionally unbalanced structures." Thesis, University College London (University of London), 2000. http://discovery.ucl.ac.uk/1349433/.
Повний текст джерелаАнотація:
Structures exhibit coupled torsional and translational responses to earthquake ground motion input if their centres of floor mass and their centres of resistance do not coincide. However, torsional motions may occur even in nominally symmetric structures due to accidental eccentricity and torsional ground motions. The sources giving rise to accidental eccentricity include the difference between the assumed and actual distributions of mass and stiffness, asymmetric yielding strength, non-linear patterns of force-deformation relationships, and differences in coupling of the structural foundation with the supporting soil. Symmetric and regular buildings that are properly designed have a much higher ability to survive a strong earthquake event than asymmetric buildings and their response to earthquake loading is far more straightforward to predict and design for. On the other hand, even though the response of asymmetric buildings is more unpredictable, designers still have to compromise structural regularity to accommodate functional and aesthetic needs. As a result, serious and widespread damage associated with structural asymmetry has been observed repeatedly in past major earthquakes. In the first studies examining torsional effects in buildings, attention was focused on the elastic structural behaviour of single-storey buildings and the main purpose was to achieve a complete understanding of the effects of mass and stiffness eccentricities and to evaluate them by simple static models. However, as the response of real structures is mainly inelastic, these studies gave poor information on torsional behaviour and interest has moved towards non-linear response studies. In an effort to clarify some of the issues influencing the inelastic torsional response of multistorey asymmetric structures, this thesis presents a series of coherent parametric investigations. These investigations include comparing the response of various reference models to the performance of code-designed torsionally unbalanced structures. An extensive parametric investigation of torsionally responding structures designed as stipulated by a selection of major earthquake building codes is presented and the adequacy of the static torsional provisions is assessed for a wide range of structural configurations and parameters. Detailed investigations of torsionally asymmetric structures incorporating frame elements oriented along both orthogonal axes of the structure are also conducted and the effect of including the second earthquake component to simultaneously excite the structural models is quantified. The relative merits and deficiencies of each code provision are discussed and a new proposed optimised method is tested. All fundamental conclusions from the investigations conducted are presented and various topics for further research are proposed, which are considered to be both necessary and pertinent for increasing and refining the knowledge and understanding the complex behaviour of multistorey torsionally asymmetric buildings.
12
Caporaletti, Paola. "Tunnelling in layered ground and its effects on pre-existing masonry structures." Doctoral thesis, La Sapienza, 2005. http://hdl.handle.net/11573/917015.
Повний текст джерелаАнотація:
The research described in this dissertation concerns the soil movements
due to tunnelling in two layers ground condition and its effects on pre-existing
historical structures. In this introductory chapter the objectives and background of
the work are presented, followed by an overview of the methodology used to
investigate the problem and an outline of the following chapters.
13
Iwasaki, Yoshinori. "Geotechnical Study on Ground and Masonry Structures in Angkorfor Safeguarding Monuments." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/138469.
Повний текст джерела
14
Ward, Charles. "Modification of a Ground Based Atomic Oxygen Simulation Apparatus to Accommodate Three Dimensional Specimens." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1850.
Повний текст джерелаАнотація:
The space environment presents various challenges when designing systems and selecting materials for applications beyond Earth’s atmosphere. For mission success, these challenges must be considered. One of the detrimental aspects of the space en- vironment is Atomic Oxygen, AO. Only present in harmful quantities in Lower Earth Orbit, LEO, AO causes significant damage to materials by breaking molecular bonds. California Polytechnic State University’s, Cal Poly’s, space environments laboratory features an apparatus capable of simulating this environment. Very thin or short samples were tested to observe the mass loss due to erosion of the sample material. Recent modifications to the system allow it to expose surfaces of three dimensional objects to AO rather than only those two dimensional objects. Simulating this effect on taller samples makes available the opportunity to test coupons that are then used in additional testing to measure the effect of that erosion on other properties. Challenges in adapting the AO system are explored and addressed, as well as some possible use cases for future work. As a use case, bending moment specimens were exposed to AO prior to testing in four point bending. Multiple regression models were constructed to determine variables contributing to slope changes between specimen pairs’ linear-elastic regions of force-displacement graphs. Results show that AO exposed specimens had significantly gentler slopes in the linear elastic region of the force-displacement curve, meaning that AO exposure reduced structural rigidity of the coupons.
15
Ramshaw, Christine Lesley. "Computation of ground waves from pile driving and their effects on structures." Thesis, Durham University, 2002. http://etheses.dur.ac.uk/3762/.
Повний текст джерелаАнотація:
Present guidance on levels of vibration generated by pile driving is primarily empirical, conservative and often contradictory. The objective of this research was to model the ground waves generated by pile driving using the ABAQUS finite element program in order to predict the free ground surface response resulting from installation by both impact and vibratory hammers. New procedures including infinite element and quiet boundary formulations have been developed for the computation of ground surface vibrations caused by impact and vibratory driving of pre-formed piles. The procedures do not require a detailed knowledge of site conditions and are therefore particularly useful as a preliminary design tool and for modelling the large amount of site data that currently exists in order to assist in the development of more rational guidance. The work has brought together research from several areas of study in order to produce computational procedures for modelling vibrations from pile driving. The new models have been validated by comparisons with measurements from various piling sites. The new methods now need to be applied to a large number of varied sites in order to develop site specific guidance. It is envisaged that this guidance could be in the form of design charts or simple formulae for incorporation into the relevant British Standards or Eurocodes. A range of common building forms has been incorporated into the models. The results indicate that slender frames can be analysed by transient displacements imposed on the foundations; however, a full three-dimensional analysis with soil-structure interaction is required for walls and infilled panels so that the reduced foundation displacements are modelled correctly. The techniques developed during this project could be usefully extended to model the effects of pile driving on various geotechnical structures and pipelines and also other forms of excitation, such as vibrocompaction.
16
Mansour, Sharief Ramsis Nasief. "Evaluation of a novel design of masonry structures subject to ground movement." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47172.
Повний текст джерела
17
Medina, Ricardo A. Krawinkler Helmut. "Seismic demands for nondeteriorating frame structures and their dependence on ground motions /." Berkeley : Pacific Earthquake Engineering Research Center, 2004. http://peer.berkeley.edu/publications.
Повний текст джерелаАнотація:
Originally published as first author's thesis."May 2004." "John A. Blume Earthquake Engineering Center, Dept. of Civil & Environmental Engineering, Stanford University." Includes bibliographical references.
18
Kang, GiChun. "Assessing uplift displacement of buried geotechnical structures in liquefied ground during earthquakes." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120829.
Повний текст джерела
19
Bianchini, Marcello <1976>. "Improved ground motion intensity measures for reliability-based demand analysis of structures." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/959/1/Tesi_Bianchini_Marcello.pdf.
Повний текст джерелаАнотація:
In Performance-Based Earthquake Engineering (PBEE), evaluating the seismic performance (or seismic risk) of a structure at a designed site has gained major attention,
especially in the past decade. One of the objectives in PBEE is to quantify the seismic
reliability of a structure (due to the future random earthquakes) at a site. For that
purpose, Probabilistic Seismic Demand Analysis (PSDA) is utilized as a tool to estimate the Mean Annual Frequency (MAF) of exceeding a specified value of a structural
Engineering Demand Parameter (EDP).
This dissertation focuses mainly on applying an average of a certain number of spectral acceleration ordinates in a certain interval of periods, Sa,avg (T1,…,Tn), as scalar
ground motion Intensity Measure (IM) when assessing the seismic performance of inelastic structures. Since the interval of periods where computing Sa,avg is related to the more
or less influence of higher vibration modes on the inelastic response, it is appropriate to
speak about improved IMs. The results using these improved IMs are compared with
a conventional elastic-based scalar IMs (e.g., pseudo spectral acceleration, Sa (
T(¹)), or peak ground acceleration, PGA) and the advanced inelastic-based scalar IM (i.e.,
inelastic spectral displacement, Sdi). The advantages of applying improved IMs are:
(i ) "computability" of the seismic hazard according to traditional Probabilistic Seismic
Hazard Analysis (PSHA), because ground motion prediction models are already available for Sa (Ti), and hence it is possibile to employ existing models to assess hazard in
terms of Sa,avg, and (ii ) "efficiency" or smaller variability of structural response, which
was minimized to assess the optimal range to compute Sa,avg. More work is needed to
assess also "sufficiency" and "scaling robustness" desirable properties, which are disregarded in this dissertation. However, for ordinary records (i.e., with no pulse like
effects), using the improved IMs is found to be more accurate than using the elastic-
and inelastic-based IMs. For structural demands that are dominated by the first mode
of vibration, using Sa,avg can be negligible relative to the conventionally-used Sa (T(¹)) and the advanced Sdi. For structural demands with sign.cant higher-mode contribution,
an improved scalar IM that incorporates higher modes needs to be utilized.
In order to fully understand the influence of the IM on the seismis risk, a simplified
closed-form expression for the probability of exceeding a limit state capacity was chosen
as a reliability measure under seismic excitations and implemented for Reinforced Concrete (RC) frame structures. This closed-form expression is partuclarly useful for seismic
assessment and design of structures, taking into account the uncertainty in the generic
variables, structural "demand" and "capacity" as well as the uncertainty in seismic excitations. The assumed framework employs nonlinear Incremental Dynamic Analysis
(IDA) procedures in order to estimate variability in the response of the structure (demand) to seismic excitations, conditioned to IM. The estimation of the seismic risk using
the simplified closed-form expression is affected by IM, because the final seismic risk is
not constant, but with the same order of magnitude. Possible reasons concern the non-linear model assumed, or the insufficiency of the selected IM. Since it is impossibile to
state what is the "real" probability of exceeding a limit state looking the total risk, the
only way is represented by the optimization of the desirable properties of an IM.
20
Bianchini, Marcello <1976>. "Improved ground motion intensity measures for reliability-based demand analysis of structures." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/959/.
Повний текст джерелаАнотація:
In Performance-Based Earthquake Engineering (PBEE), evaluating the seismic performance (or seismic risk) of a structure at a designed site has gained major attention,
especially in the past decade. One of the objectives in PBEE is to quantify the seismic
reliability of a structure (due to the future random earthquakes) at a site. For that
purpose, Probabilistic Seismic Demand Analysis (PSDA) is utilized as a tool to estimate the Mean Annual Frequency (MAF) of exceeding a specified value of a structural
Engineering Demand Parameter (EDP).
This dissertation focuses mainly on applying an average of a certain number of spectral acceleration ordinates in a certain interval of periods, Sa,avg (T1,…,Tn), as scalar
ground motion Intensity Measure (IM) when assessing the seismic performance of inelastic structures. Since the interval of periods where computing Sa,avg is related to the more
or less influence of higher vibration modes on the inelastic response, it is appropriate to
speak about improved IMs. The results using these improved IMs are compared with
a conventional elastic-based scalar IMs (e.g., pseudo spectral acceleration, Sa (
T(¹)), or peak ground acceleration, PGA) and the advanced inelastic-based scalar IM (i.e.,
inelastic spectral displacement, Sdi). The advantages of applying improved IMs are:
(i ) "computability" of the seismic hazard according to traditional Probabilistic Seismic
Hazard Analysis (PSHA), because ground motion prediction models are already available for Sa (Ti), and hence it is possibile to employ existing models to assess hazard in
terms of Sa,avg, and (ii ) "efficiency" or smaller variability of structural response, which
was minimized to assess the optimal range to compute Sa,avg. More work is needed to
assess also "sufficiency" and "scaling robustness" desirable properties, which are disregarded in this dissertation. However, for ordinary records (i.e., with no pulse like
effects), using the improved IMs is found to be more accurate than using the elastic-
and inelastic-based IMs. For structural demands that are dominated by the first mode
of vibration, using Sa,avg can be negligible relative to the conventionally-used Sa (T(¹)) and the advanced Sdi. For structural demands with sign.cant higher-mode contribution,
an improved scalar IM that incorporates higher modes needs to be utilized.
In order to fully understand the influence of the IM on the seismis risk, a simplified
closed-form expression for the probability of exceeding a limit state capacity was chosen
as a reliability measure under seismic excitations and implemented for Reinforced Concrete (RC) frame structures. This closed-form expression is partuclarly useful for seismic
assessment and design of structures, taking into account the uncertainty in the generic
variables, structural "demand" and "capacity" as well as the uncertainty in seismic excitations. The assumed framework employs nonlinear Incremental Dynamic Analysis
(IDA) procedures in order to estimate variability in the response of the structure (demand) to seismic excitations, conditioned to IM. The estimation of the seismic risk using
the simplified closed-form expression is affected by IM, because the final seismic risk is
not constant, but with the same order of magnitude. Possible reasons concern the non-linear model assumed, or the insufficiency of the selected IM. Since it is impossibile to
state what is the "real" probability of exceeding a limit state looking the total risk, the
only way is represented by the optimization of the desirable properties of an IM.
21
Parsa, Amanullah. "EFFECT OF BUILDING ORIENTATION ON STRUCTURAL RESPONSE OF REINFORCED CONCRETE MOMENT RESISTING FRAME STRUCTURES." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2698.
Повний текст джерелаАнотація:
In time history analysis of structures, the geometric mean of two orthogonal horizontal components of ground motion in the as-recorded direction of sensors, have been used as measure of ground motion intensity prior to the 2009 NEHRP provision. The 2009 NEHRP Provisions and accordingly the seismic design provisions of the ASCE/SEI 7-10, modified the definition of ground motion intensity measure from geometric mean to the maximum direction ground motion, corresponding to the direction that results in peak response of the oscillator. Maximum direction response spectra are assumed to envelope the range of maximum possible responses over all nonredundant rotation angles. Two assumptions are made in the use maximum ground motion as the intensity measure: (1) the structure’s strength and stiffness properties are identical in all directions and (2) azimuth of the maximum spectral acceleration coincides with the one of the principal axes of the structure. The implications of these assumptions are examined in this study, using 3D computer models of multi-story structures having symmetric and asymmetric layouts and elastic vibration period of 0.2 second and 1.0 second subjected to a set of 25 ground-motion pairs recorded at a distance of more than 20 km from the fault. The influence of the ground-motion rotation angle on structural response (here lateral displacement and story drift) is examined to form benchmarks for evaluating the use of the maximum direction (MD) ground motions. The results of this study suggest that while MD ground motions do not always result in largest structural response, they tend to produce larger response than the as-recorded ground motions. On the other hand, more research on non-linear seismic time history analysis is recommended, especially for asymmetric layout plan buildings.
22
Hong, S. G. "Analysis and optimisation of passenger car front structures in frontal barrier impact." Thesis, Cranfield University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334670.
Повний текст джерела
23
Zhao, Ke. "The electronic structures of C28 and U@C28." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1100808287.
Повний текст джерела
24
Ozdemir, Gokhan. "Response Of Isolated Structures Under Bi-directional Excitations Of Near-field Ground Motions." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12612039/index.pdf.
Повний текст джерелаАнотація:
Simplified methods of analysis described in codes and specifications for
seismically isolated structures are always used either directly in special cases or for
checking the results of nonlinear response history analysis (RHA). Important
predictions for seismically isolated structures by simplified methods are the
maximum displacements and base shears of the isolation system. In this study, the
maximum isolator displacements and base shears determined by nonlinear RHA are
compared with those determined by the equivalent lateral force (ELF) procedure in
order to assess the accuracy of the simplified method in the case of bi-directional
excitations with near-field characteristics. However, although there are currently
many methods for ground motion selection and scaling, little guidance is available
to classify which method is more appropriate than the others in any applications.
Features of this study are that the ground motions used in analysis are selected and
scaled using contemporary concepts and that the ground excitation is considered biv
directional. The variations in response of isolated structures due to application of
ground motions uni-directionally and bi-directionally are also studied by employing
a scaling procedure that is appropriate for the bi-directional analysis. The proposed
new scaling methodology is an amplitude scaling method that is capable of
preserving the horizontal orthogonal components and it is developed especially for
dynamic analysis of isolated structures. Analyses are conducted for two different
symmetric reinforced concrete isolated structure for two different soil conditions in
structural analysis program SAP2000. Effect of asymmetry in superstructure on
isolator displacement is also investigated with further analyses considering 5% mass
eccentricity at each floor level. Furthermore, once the significance of the orthogonal
horizontal component on the response of isolation system is shown, the biaxial
interaction of hysteretic behavior of lead rubber bearings is implemented in
OpenSees by developing a subroutine which was not readily available.
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Henriquez, Nicholas. "Analyzing buried reinforced concrete structures subjected to ground shock from underground localized explosions." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024817.
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Pan, Peng. "Safety and functionality of base-isolated building structures subjected to vertical ground motions." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/145351.
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Whitney, Joshua Andrew. "Application of Electromagnetic Methods to Identify and Characterize Sub-surface Structures Associated with the Coles Hill Uranium Deposit." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/33080.
Повний текст джерелаАнотація:
The Coles Hill uranium deposit in Pittsylvania County, Virginia represents the largest unmined uranium resource in the United States, with an estimated resource of 110 million pounds of U3O8 in place with a cutoff grade of 0.025 wt% U3O8. The deposit is localized along a geologic unit that parallels the Chatham Fault, which separates the Triassic Danville Basin to the east from the older crystalline rocks to the west. The location of the Chatham Fault is important to understanding distribution of ore and for developing an effective mine plan. In this study the Chatham Fault location has been inferred from ground conductivity and ground penetrating radar (GPR) surveys. Anomalies in the data are consistent with previously mapped fault locations based on drillhole and geophysical data, such as gravity and magnetic surveys, collected in the 1980s. These results confirm that the strike of the Chatham Fault is approximately N40ºE and dips to the southeast with dip values ranging from 70º, in the northeast, to 50º, in the southwest.Master of Science
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Brown, Andrew, and Hua Lee. "SYNTHETIC APERTURE GROUND PENETRATING RADAR IMAGING FOR NONDESTRUCTIVE EVALUATION OF CIVIL AND GEOPHYSICAL STRUCTURES." International Foundation for Telemetering, 2001. http://hdl.handle.net/10150/607690.
Повний текст джерелаАнотація:
International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, NevadaSynthetic-aperture microwave imaging with ground penetrating radar systems has become a research topic of great importance for the potential applications in sensing and profiling of civil and geophysical structures. It allows us to visualize subsurface structures for nondestructive evaluation with microwave tomographic images. This paper provides an overview of the research program, ranging from the formation of the concepts, physical and mathematical modeling, formulation and development of the image reconstruction algorithms, laboratory experiments, and full-scale field tests.
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Sangiovanni, Maria. "Analysis of the response of irregular structures to the 2012 Emilia Earthquake ground-motions." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4239/.
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Theophilou, Artemis I. "A ground motion selection and modification method suitable for probabilistic seismic assessment of building structures." Thesis, University of Surrey, 2013. http://epubs.surrey.ac.uk/811162/.
Повний текст джерелаАнотація:
Probabilistic seismic assessment is of interest both in the design of new structures, and in the assessment of existing structures. An accurate prediction of the structural response distribution requires a large number of dynamic analyses, using a large number of ground motions. Such a task, however, requires substantial computational work, and, furthermore, is impeded by the scarcity of high intensity records. In this research a methodology is proposed for sampling optimized suites of ground motions, which methodology is comprised of a vector-valued intensity measure (IM), and a ground motion selection and modification (GMSM) method. Using the optimized suites, an optimized response prediction is obtained, which presents a compromise between the reduction in the number ground motions used, and the loss of accuracy. The proposed vector-valued IM is comprised of the spectral acceleration at the fundamental period, the Normalized Spectral Area (NSA) parameter, and, optionally, a measure of the nonlinearity level. NSA is defined as the area of the displacement response spectrum between the fundamental period and the ultimate elongated period, normalized to the spectral displacement at the fundamental period. In this way, it captures the effect of the excitation spectral characteristics (i.e. frequency composition) on the response. NSA is intended to have high correlation to various relative response parameters. With the proposed GMSM method, optimized suites are formed through stratified sampling on the NSA parameter, using datasets of ground motions normalized to the spectral acceleration at the fundamental mode, in order to replicate the IM true central tendency and true dispersion. Consequently, the response parameter true central tendency and true dispersion are also replicated. Stratified sampling results in a reduced standard error of the mean IM, contrasted to random sampling. The advantage of the proposed GMSM method is that when there is sufficiently high correlation between NSA and the relative response parameters, the standard error of the mean is also reduced.
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Olgun, Celal Guney. "Performance of Improved Ground and Reinforced Soil Structures during Earthquakes – Case Studies and Numerical Analyses." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/26002.
Повний текст джерелаАнотація:
The 1999 Kocaeli Earthquake (M=7.4) struck northwestern Turkey on August 17, 1999 and caused significant damage in urban areas located along Izmit Bay. The sites that suffered the greatest damages were located primarily in areas of poorest soil conditions, typically containing soft clays and silts and/or loose, liquefiable sands. Because the affected region is heavily developed with infrastructure and there is a preponderance of poor soils, a wide range of soil improvement measures had been used to mitigate anticipated earthquake damages throughout the region. Following the earthquake and significant aftershocks, Virginia Tech researchers traveled to Turkey to investigate the affected area to document geotechnical field performance. Primary focus of the Virginia tech team was given to investigating the performance of improved soil sites and reinforced soil structures. The sites were subjected to ground motions ranging from about 0.10g to 0.35g. The site locations ranged from 0 to 35 km from the zone of energy release. This dissertation presents in detail, the findings from the two most instructive sites. The investigation of these sties involved field reconnaissance, field and laboratory testing of soils, seismic analysis, numerical modeling, and other analytical work.Ph. D.
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Glicklin, Max Jay. "Development of a Ground Based Atomic Oxygen and Vacuum Ultraviolet Radiation Simulation Apparatus." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/799.
Повний текст джерелаАнотація:
The space environment possesses numerous unique and unusual attributes, creating challenges that must be considered in order to accomplish a successful space mission. Two of the detrimental aspects of the space environment include Atomic Oxygen, AO, and Ultraviolet, UV, radiation. UV radiation becomes more severe in space as there is no atmosphere to attenuate incoming photons, thereby exposing spacecraft to radiation that never reaches the surface of the Earth. Overall, space vehicles are exposed to a total of 107.4 Watts/m2 of light shorter than 400 nm. AO is created by the photo disassociation of molecular oxygen by UV radiation with wavelengths less than ~242.1 nm. AO is a major portion of the neutral atmosphere, and is the dominant species for altitudes between 180 and 675 km. Each of these environments can cause significant damage to spacecraft materials as they have sufficient energy to break molecular bonds: a generalization of AO energy is 4.5 +/- 1 eV while Vacuum Ultraviolet, VUV, radiation can break bonds as strong as 12.4 eV. Synergistic affects are observed when these two environments interact with materials simultaneously, resulting in an accelerated erosion rate. An apparatus has been developed in California Polytechnic State University’s, Cal Poly’s, space environments laboratory that can simulate the AO and VUV environments individually and simultaneously. This apparatus utilizes a radio frequency, RF, generator to produce a capacitively coupled plasma to create AO in conjunction with a deuterium lamp capable of emitting UV radiation as short as 115 nm. The system has been shown to produce an AO flux of 1.70 +/- 0.07•1016 atoms/cm2 while providing an equivalent sun power 4.5 times greater the solar output in the 120-200 nm region of UV light; all of this has been performed at a base pressure near 175 mTorr. Long duration tests of 24 hours, which would be analogous to durations used in a material interaction study, have shown an effective fluence of 1.47 +/- 0.06•1021 atoms/cm2, which would equate to an orbital exposure on the order of weeks to months. For the same duration a sample can be exposed to 108 equivalent sun hours of 120-200 nm radiation. Results from the simultaneous exposure also manifested an accelerated erosion rate, the expected synergetic reactions between the two environments.
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Ramin, Latifi. "Effect of pulse-like near-fault ground motions on inelastic response of structures including foundation flexibility." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45534.
Повний текст джерелаАнотація:
For the sites in close proximity to a causative fault where formation of near fault long period velocity pulses is conceivable, consideration of flexibility of the foundation system is very important. This is due to the fact that when the flexibility of the base is taken into account the period of the system is longer than the period of the same system assuming a fixed base. Depending on the depth and the stiffness of the underlying soil the period of the system approaches the period of the near fault long period pulses, hence the response of the structure could be much larger.
The purpose of this research is to study the nonlinear response of structures to pulse-like near fault ground motions with and without allowing for the foundation system flexibility.
To highlight the impact of the near fault ground motions the nonlinear responses of single degree of freedom systems (resembling fixed base structures) to the near fault ground motions are compared to the responses of the same systems to the equivalent far field ground motions.
The effects of (translational and rocking) flexibility of the foundation system is also considered using equivalent linear springs and lumped masses added to the base of the single degree of freedom systems.
A major parametric study is performed to determine which parameter has the most significant impact on the response of the structure for near fault ground motions when effect of flexibility of the foundation system is explicitly accounted for.
An efficient procedure has been developed for predicting the response of a structure with a flexible base to near fault ground motions deduced from the response of an equivalent single degree of freedom system to the equivalent far field ground motions. Validity of the proposed procedure for assessing the effects of near fault ground motions, and the influence of flexibility of the foundation system on the structures’ responses is verified using different analytical models, including a full 3D analysis of a bridge structure; the results proved to be quite satisfactory.
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Rivera, Mario A. "Seismic Response of Structures with Flexible Floor Slabs by a Dynamic Condensation Approach." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/29645.
Повний текст джерелаАнотація:
The flexibility of the floor slabs is quite often ignored in the seismic analysis of structures. In general, the rigid behavior assumption is appropriate to describe the in-plane response of floors. For seismic excitations with vertical components, however, the flexibility of the floor slabs in the out-of-plane direction may play a significant role and it can result in an increase in the seismic response. The simplified procedures used in the current practice to include the floor flexibility can lead to highly conservative estimates of the slab and supported equipment response. To include floor flexibility, a detailed finite element model of the structure can be constructed, but this procedure leads to a system with large degrees of freedom the solution of which can be time consuming and impractical. In this study, a new dynamic condensation approach is developed and proposed to reduce the size of the problem and to calculate the seismic response of structures with flexible floor slabs. Unlike other currently available dynamic condensation techniques, this approach is applicable to classically as well as nonclassically damped structures. The approach is also applicable to structures divided into substructures. The approach can be used to calculate as many lower eigenproperties as one desires. The remaining higher modal properties can also be obtained, if desired, by solving a complementary eigenvalue problem associated with the higher modes. The accuracy of the calculated eigenproperties can be increased to any desired level by iteratively solving a condensed and improved eigenvalue problem. Almost exact eigenproperties can be obtained in just a few iterative cycles. Numerical examples demonstrating the effectiveness of the proposed approach for calculating eigenproperties are presented. To calculate the seismic response, first the proposed dynamic condensation approach is utilized to calculate the eigenproperties of the structure accurately. These eigenproperties are then used to calculate the seismic response for random inputs such as a spectral density function or inputs defined in terms of design response spectra. Herein, this method is used to investigate the influence of the out-of-plane flexibility of the floor slabs on the response of primary and secondary systems subjected to vertical ground motions. The calculated results clearly show that inclusion of the floor flexibility in the analytical model increases the design response significantly, especially when computing acceleration floor response spectra. This has special relevance for secondary systems and equipment the design of which are based on the floor response spectra. The accuracy of the results predicted by two of the most popular methods used in practice to consider the floor flexibility effects, namely the cascade approach and the modified lumped mass method, is also investigated. The numerical results show that the cascade approach overestimates the seismic response, whereas the modified lumped mass method underestimates the response. Both methods can introduce significant errors in the response especially when computing accelerations and floor response spectra. For seismic design of secondary systems supported on flexible slabs, the use of the proposed condensation approach is thus advocated.Ph. D.
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Ieronymaki, Evangelia S. "Prediction and interpretation of ground movements due to tunneling in stiff clay and impacts on adjacent structures." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99610.
Повний текст джерелаАнотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 319-328).
Construction of large diameter tunnels is frequently accomplished by closed face tunnel boring machines (TBM) using a combination of face pressure and grouting around the precast lining in order to limit ground movements and potential damage to overlying structures. This thesis analyzes monitoring data from the Crossrail project involving twin tunnels construction using Earth Pressure Balance (EPB) machines in London Clay. The research focuses on the 'greenfield' response during tunnel excavation beneath Hyde Park. Far-field measurements of surface and subsurface ground movements were interpreted using 2D finite element analyses using a range of constitutive models with parameters calibrated to non-linear stress-strain properties measured in high quality laboratory tests on London Clay. The analyses optimize three input parameters corresponding to boundary deformations around the tunnel cavity, using a least squares fit to the measured ground movements. The results for the first tunnel (WB) show that even simple soil models are able to achieve good agreement with far field ground deformations, while more complex models (MIT-Si) can represent accurately movements occurring much closer to the tunnel lining and hence, provide a more reliable guide to deformation sources at the tunnel cavity. The study also shows how ground movements induced by the second (EB) tunnel were influenced by proximity to the completed WB tunnel. The results provide a comprehensive view of the ground movement pattern and a useful framework for understanding how ground response is linked to EPB control parameters that can be investigated using 3D finite element models. Comparisons with data from prior open-face shield construction of the Jubilee Line Extension (in similar ground conditions) show that there are pervasive differences in the magnitudes and cavity deformations modes associated with different methods of tunnel construction. The current analyses of soil-structure interaction consider the measured deformations of a concrete-framed structure, Avenfield House, caused by the twin Crossrail tunnels. The thesis proposes a simple elastic shear beam model of the structure and assumes that the cavity deformation parameters are uncoupled from the presence of the structure. The results demonstrate that deformations of the structure can be predicted using information from the greenfield ground response.
by Evangelia S. Ieronymaki.
Ph. D.
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Chen, Guang. "Modeling and Characterization of Plane Pair Structures in High-Speed Power Delivery Systems." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195454.
Повний текст джерелаАнотація:
The power/ground plane structure within an electronic system not only delivers power, but also provides return path for the currents associated with the propagating signals. The cavity resonances within the power/ground plane structure affect the signal integrity of the system at high frequencies. The chip complexity and clock speed continue to increase and new structures, such as meshed planes and electromagnetic bandgap structures, are used in plane pair structure design. The signal integrity analysis of the power/ground plane structure becomes exceedingly important and challenging.The primary goal of this research is an in-depth investigation of the impact of the cavity resonances associated with the plane pair structure on the signal integrity. This includes development of modeling, simulation, and measurement methodologies for accurate and efficient characterization or prediction of the time/frequency domain electrical characteristics of power/ground plane pair structures. This research is divided into three parts. First, new SPICE compatible models are proposed for the new structures, such as the meshed plane and EBG embedded plane pair designs, so that the power/ground plane designs with these new structures can be simulated efficiently. Second, the accuracy of the simulation results is vital. The behavior of the benchmark structures is simulated and simulation results are verified either experimentally or by comparing with those from tools that are proven to be accurate. Third, high frequency measurement data is vulnerable to all parasitic parameters. The factors that affect the accuracy of measured data are investigated and methods to improve the accuracy of the measured data are proposed and verified.
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Erdogan, Burcu. "Simple Models For Drift Estimates In Framed Structures During Near-field Earthquakes." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608699/index.pdf.
Повний текст джерелаАнотація:
Maximum interstory drift and the distribution of this drift along the height of the structure are the main causes of structural and nonstructural damage in frame type buildings subjected to earthquake ground motions. Estimation of maximum interstory drift ratio is a good measure of the local response of buildings. Recent earthquakes have revealed the susceptibility of the existing building stock to near-fault ground motions characterized by a large, long-duration velocity pulse. In order to find rational solutions for the destructive effects of near fault ground motions, it is necessary to determine drift demands of buildings. Practical, applicable and accurate methods that define the system behavior by means of some key parameters are needed to assess the building performances quickly instead of detailed modeling and calculations.
In this study, simple equations are proposed in order for the determination of the elastic interstory drift demand produced by near fault ground motions on regular and irregular steel frame structures. The proposed equations enable the prediction of maximum elastic ground story drift ratio of shear frames and the maximum elastic ground story drift ratio and maximum elastic interstory drift ratio of steel moment resisting frames. In addition, the effects of beam to column stiffness ratio, soft story factor, stiffness distribution coefficient, beam-to-column capacity ratio, seismic force reduction factor, ratio of pulse period to fundamental period, regular story height and number of stories on elastic and inelastic interstory drift demands are investigated in detail. An equation for the ratio of maximum inelastic interstory drift ratio to maximum elastic interstory drift ratio developed for a representative case is also presented.
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Köberle, Patrick [Verfasser]. "Ground-state structures and dynamics of dipolar Bose-Einstein condensates in single and multi-layered traps / Patrick Köberle." München : Verlag Dr. Hut, 2011. http://d-nb.info/1016531664/34.
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Rigato, Antonio Bruno. "Influence of angle of incidence on the seismic demands for inelastic structures subjected to bi-directional ground motions." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/7360.
Повний текст джерелаАнотація:
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Civil Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Halling, Marvin W. Hall John F. Hall John F. "Investigation of base-isolated structures during recent earthquakes and computer simulations utilizing near-source long-period ground motions /." Diss., Pasadena, Calif. : California Institute of Technology, 1995. http://resolver.caltech.edu/CaltechETD:etd-10152007-141910.
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Arben, PITARKA. "Modeling wave propagation in two-and three dimensional heterogeneous structures and its application to the strong ground motion prediction." 京都大学 (Kyoto University), 1997. http://hdl.handle.net/2433/202446.
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CALCINA, SERGIO VINCENZO. "Ambient vibration measurements for non-destructive evaluation of structures by means of seismic methods and ground-based microwave interferometry." Doctoral thesis, Università degli Studi di Cagliari, 2015. http://hdl.handle.net/11584/266845.
Повний текст джерелаАнотація:
This thesis collects the results of the researches carried out during the Ph.D. course in “Technologies for the Conservation of Architectural and Environmental Heritage” into the School of Civil Engineering and Architecture of the University of Cagliari. The main topics of this research are focused on the experimental dynamic analysis of the structures with prevalent, but not exclusive, interest for the analyses of historic structures. The research deals with several issues concerning both the experimental measurements and the relationships between vibration properties and structural features and materials.
The study starts with an introduction, developed into the first chapter, where the general principles of the experimental dynamic analysis methods of structures are presented and summarised, especially for the passive techniques based only on ambient vibrations records.
The next chapter presents and describes the main features of the Ground-based Radar Interferometry to perform remote measurements of vibrations, using the phase difference between reflected signals coming from the surface of the same object inside the radar scenario. This technique has been developed in relatively recent years and has seen a considerable spread thanks to the short time need for the measurements and for the capability to retrieve reliable time series of displacement without any contact sensors above the structures. Furthermore the vibration data, acquired with both conventional systems (such as seismic sensors, velocimeters, accelerometers, etc.) and the microwave interferometer IBIS-S (Image By Intereferometry Survey), have been compared.
Different case studies have been examined and critically discussed in the following chapters.
In particular, chapter three is focused on the analysis of the vibration properties of an earthquake damaged bell tower located near the epicenter of the Emilia earthquake. Both ex ante and ex post conditions respect to the seismic induced damage have been compared. For this purpose a non-contact dynamic survey has been carried out by means of the radar interferometry method. The campaign of measurements has been conducted after the earthquake to describe the dynamic behaviour of the structure with open fractures pattern and with significant structural damages. Finally, a Finite Element model of the structure has been done in order to compare the actual dynamic response of the tower with that one of the undamaged structure.
Chapter four looks at the influence of the vibration artificially induced by the coordinated movement of twenty people to improve main dynamic properties identification of the structure. In this case, the measurements have been carried out using the radar sensor by means of four stations located around the examined structure, the Leaning Tower of Pisa. The measurements have been performed in both operational mode using only wind induced vibrations and also with the artificial human forcing, applied at the top floor of the tower.
Chapter five describes both the experimental measurements and the numerical modelling carried out in order to derive the dynamic features of two similar bell towers. The comparison between the dynamic behaviour of the towers is aimed at studying the influence of the mechanical properties of different construction materials. In fact, the towers are symmetrically built on both sides of the main façade of a church but the two structures are made using different materials and with different construction techniques. The oldest tower is a stone masonry building and the second one is a Reinforced Concrete structure. In this case, the analyses have been carried out using vibration data acquired by means of both available systems, i.e. the IBIS-S radar interferometer for the
2
measurements related to the upper parts of the structure (not easily accessible) and some seismic transducers for the stations located inside of the building.
Chapter six finally presents the vibration measurements performed on a double curvature arch dam with different reservoir water level in order to analyse the variation of the linear dynamic response of the structure related to the water level height on the upstream side of the dam. The experimental surveys are described and the comparison with a numerical modelling is shown.
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Todkar, Shreedhar Savant. "Monitoring subsurface conditions of pavement structures using Ultra-wideband radar technology." Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4060.
Повний текст джерелаАнотація:
Dans le domaine du génie civil, la détection et la caractérisation de défauts (décollements, fissures non-débouchantes) sont des éléments importants de diagnostic qui influencent la mise en œuvre de politique d’entretien et de gestion. Les défauts sont représentatifs d’un état d’altération de la structure. Les caractéristiques géométriques de ces défauts (forme, largeur et longueur) ainsi que l’étendue et les cheminements d’eau induits par ces défauts est un indicateur de durabilité des ouvrages important. Cette détection permet de localiser une éventuelle pathologie, d’évaluer l’état de santé de la structure et de prédire son évolution. Dans ce contexte, les systèmes « radar à impulsions », appelé aussi GPR (Ground Penetrating radar) est utilisé depuis une trentaine d’années pour réaliser des opérations de contrôle non destructif dans le flux du trafic. Ils fournissent une mesure en continu de l’épaisseur de la couche de chaussée, mais permettent aussi la détection de décollements significatifs (centimétrique) entre couches, et de déterminer ainsi l’emplacement de contrôles structurels destructifs ultérieurs. Néanmoins, la résolution temporelle des GPR conventionnels ne permet pas de détecter directement des décollements d’interface millimétriques. L’objectif de ce travail est donc de réaliser une détection précoce de ce type de défauts. Ainsi, mes travaux se sont focalisés à la fois sur l'utilisation du radar ultra large bande (RSF) et sur le développement de méthodes d’intelligence artificielle (basées sur l’apprentissage supervisé). Des approches théoriques et expérimentales (dalle de chaussée Cerema et manège de fatigue de l’IFSTTAR) ont été réalisées. Elles ont permis de montrer la faisabilité de détecter des décollements fins dans les chausséesIn the field of civil engineering, the detection and characterization of defects (debondings, non-emerging cracks) are important diagnostic elements that influence the maintenance and management of the pavement structure. These defects represent an altered state of the structure. The geometric characteristics of these defects (shape, width and length) as well as their extent and the water seepage induced by these defects are important durability indicators of the structures. This detection makes it possible to locate a possible pathology, to evaluate the state of health of the structure and also predict its evolution. In this context, "pulse radar" systems, also called Ground Penetrating Radar (GPR) have been used for over thirty years to perform non- destructive testing operations in the traffic flow. They not only provide continuous measurement of the thickness of the pavement layer, but also allow the detection of significant (centimetric) inter-layer detachments, and thus determine the location of subsequent destructive structural controls. However, the temporal resolution of conventional GPRs does not allow direct detection of millimeteric interface debondings. Therefore, the objective of this work is to realize an early detection of such defects. My work is thus focused on both the use of ultra-wideband radar (SFR) and the development of artificial intelligence methods (based on supervised learning) to detect thin debondings. Theoretical and experimental approaches (Cerema test pavement slabs and IFSTTAR's fatigue carousel) were realized which have shown the feasibility of detecting fine debondings in pavements
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Stefanou, Stefanos. "Design, fabrication and characterisation of advanced substrate crosstalk suppression structures in silicon on insulator substrates with buried ground planes (GPSOI)." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268642.
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Howlader, Md Omar Faruq. "Development of a wall climbing robot and ground penetrating radar system for non-destructive testing of vertical safety critical concrete structures." Thesis, London South Bank University, 2016. http://researchopen.lsbu.ac.uk/1798/.
Повний текст джерелаАнотація:
This research aims to develop a unique adhesion mechanism for wall climbing robot to automate the technology of non-destructive testing (NDT) of large safety critical reinforced concrete structures such as nuclear power plants, bridge columns, dams etc. This research work investigates the effect of key design parameters involved in optimizing the adhesion force achieved from rare earth neodymium magnets. In order to penetrate a nominal concrete cover to achieve magnetic coupling with buried rebar and generate high enough adhesion force by using minimum number of permanent magnets, criteria such as distance between multiple magnets, thickness of flux concentrator are evaluated by implementing finite element analysis (FEA). The proposed adhesion module consists of three N42 grade neodymium magnets arranged in a unique arrangement on a flux concentrator called yoke. The preliminary FEA results suggest that, using two yoke modules with minimum distance between them generate 82 N higher adhesion force compared to a single module system with higher forceto-weight ratio of 4.36. Presence of multiple rebars in a dense mesh setting can assist the adhesion module to concentrate the magnetic flux along separate rebars. This extended concentration area has led to higher adhesion force of 135.73 N as well as enabling the robot to take turns. Results suggest that, having a 50×50 mm rebar meshing can sustain steep robot rotational movement along it’s centre of gravity where the adhesion force can fall as low as 150 N. A small, mobile prototype robot with on-board force sensor is built that exhibited 3600 of manoeuvrability on a 50×50 mm meshed rebars test rig with maximum adhesion force of 108 N at 35 mm air gap. Both experiment and simulationresults prove that the magnetic adhesion mechanism can generate efficient adhesion force for the climbing robot to operate on vertical reinforced concrete structures. In terms of the NDT sensor, an in-depth analysis of the ground penetrating radar (GPR) is carried out to develop a low cost operational laboratory prototype. A one-dimensional numerical framework based on finite difference time domain (FDTD) method is developed to model response behaviour of a GPR. The effects of electrical properties such as dielectric constant, conductivity of the media are evaluated. A Gaussian shaped pulse is used as source which propagates through the 1D array grid, and the pulse interactions at different media interfaces are investigated. A real life application of GPR to detect a buried steel bar in 1 m thick concrete block is modelled, and the results present 100% accurate detection of the steel bar along with measured depth of the concrete cover. The developed framework could be implemented to model multi-layer dielectric blocks with detection capability of various buried objects. Experimental models are built by utilizing a proposed antenna miniaturization technique of dipole antenna with additional radiating arms. The resultant reflection coefficient values indicate a reduction of 55% and 44% in length reduction compared to a conventional 100 MHz and 200 MHz dipole antenna respectively. The GPR transmitting pulse generator features an enhanced tuneable feature to make the GPR system more adaptable to various environmental conditions. The prototype pulse generator circuit can produce pulses with variable width from 750 ps to 10 ns. The final assembled robotic GPR system’s performance is validated by its capability of detecting and localizing an aluminium sheet and a rebar of 12 mm diameter buried under a test rig built of wood to mimic the concrete structure environment. The final calculations reveal a depth error of +0.1 m. However, the key focus of this work is to prove the design concept and the error in measurement can be addressed by utilizing narrower bandwidth pulse that the proposed pulse generator is capable of generating. In general, the proposed robotic GPR system developed in this research proves the concept of feasibility of undertaking inspection procedure on large concrete structures in hazardous environments that may not be accessible to human inspectors.
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Roca, Vich Isabel. "How the ground state in a material will be affected by the spin-phonon interactions between nuclei in diatomic molecular structures." Thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-297712.
Повний текст джерелаАнотація:
Wave-like phonons are often used to describe the heat capacity in materials. In this report the spin-phonon interaction between nuclei in a diatomic molecular structure is introduced by looking at the Hamiltonian in its ground state. The corresponding Green's functions are computed in order to investigate how this interaction affects the phonons. When calculating the spin, pseudo fermions and tensor products are introduced to make the calculation easier because the spin statistics could be a bit tricky to deal with. Three different cases of how the total interaction Hamiltonian behaves are investigated i.e. when the phonon is coupled to the spin. It turns out that in two of these cases an effect on the phonons can be seen but not in the other case.
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Shrestha, Bipin. "Numerical and Experimental study of pounding damages in adjacent bridge structures subjected to spatially varying ground motion and its mitigation method." Thesis, Curtin University, 2016. http://hdl.handle.net/20.500.11937/469.
Повний текст джерелаАнотація:
Bridge infrastructure is an integral component of the transportation network with significant strategic value and is expected to remain functional in the damaged area immediately after a strong earthquake. However, previous experiences have shown that keeping the bridges operational after a strong earthquake is very challenging. This study investigates the damages resulting from pounding and unseating at bridge superstructure and residual deformation of bridge substructure subjected to earthquake loading, and the possible mitigation methods.
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Oksuz, Nevin. "Quantum-chemical Study Of Geometrical And Electronic Structures Of Aromatic Five-membered Heterocyclic Oligomers In The Ground And Lowest Singlet Excited States." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605397/index.pdf.
Повний текст джерелаАнотація:
The nature of the ground state and the first (lowest) singlet excited state geometrical conformations and electronic transitions in the aromatic five-membered heterocyclic oligomers &ndasholigothiophenes (nT), oligofurans (nF), and oligopyrroles (nP)- containing up to six monomer units (total of 18 molecules) were explored using several computational methodologies. Geometry optimizations were carried out at Austin Model 1 (AM1), Restricted Hartree-Fock (RHF/6-31G*), and Density Functional Theory (DFT, B3LYP/6-31G*) levels for the ground-state conformations of these structurally well-defined heterocyclic oligomers. The Configuration Interaction Singles (CIS) method with the 6-31G* basis set was chosen in computation of the optimal geometry of the lowest singlet excited state. Lowest singlet excitation S1ß
S0 energies were calculated using the Zerner&rsquo
s Intermediate Neglect of Differential Overlap for Spectroscopy (ZINDO/S), CIS (CIS/6-31G*), and Time-Dependent DFT (TDDFT/6-31G* and TDDFT/6-31+G*) methods. In computation of the emission S1à
S0 energies, we have employed all methods above except ZINDO/S. In investigation of geometries of the ground and lowest singlet excited state, we compared the bond length alternation (BLA) parameters, Dri in the conjugated backbone of the oligomers. Saturation of the geometrical parameters at the center of oligomers was observed after a certain chain length. Among all methodologies used in computation of excitation (S1ß
S0) and emission (S1à
S0) energies, TDDFT results showed the best agreement with experimental data. Fits of computed and experimental excitation energies to an exponential function using the least squares method enabled us to predict Effective Conjugation Length (ECL) values. We obtained the ECLs of 17 (17), 16 (15), and 14 (13) monomer units for polythiophene (PTh), polyfuran (PFu), and polypyrrole (PPr), which have very good agreement with the results obtained from the fits of experimental data (the values in parentheses).
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Yue, Hailing. "Reconfigurable Passive RF/Microwave Components." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1467817602.
Повний текст джерела
50
Abidin, Zuhairiah Zainal. "Design, modelling and implementation of antennas using electromagnetic bandgap material and defected ground planes : surface meshing analysis and genetic algorithm optimisation on EBG and defected ground structures for reducing the mutual coupling between radiating elements of antenna array MIMO systems." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5385.
Повний текст джерелаАнотація:
The main objective of this research is to design, model and implement several antenna geometries using electromagnetic band gap (EBG) material and a defected ground plane. Several antenna applications are addressed with the aim of improving performance, particularly the mutual coupling between the elements. The EBG structures have the unique capability to prevent or assist the propagation of electromagnetic waves in a specific band of frequencies, and have been incorporated here in antenna structures to improve patterns and reduce mutual coupling in multielement arrays. A neutralization technique and defected ground plane structures have also been investigated as alternative approaches, and may be more practical in real applications. A new Uni-planar Compact EBG (UC-EBG) formed from a compact unit cell was presented, giving a stop band in the 2.4 GHz WLAN range. Dual band forms of the neutralization and defected ground plane techniques have also been developed and measured. The recorded results for all antenna configurations show good improvement in terms of the mutual coupling effect. The MIMO antenna performance with EBG, neutralization and defected ground of several wireless communication applications were analysed and evaluated. The correlation coefficient, total active reflection coefficient (TARC), channel capacity and capacity loss of the array antenna were computed and the results compared to measurements with good agreement. In addition, a computational method combining Genetic Algorithm (GA) with surface meshing code for the analysis of a 2×2 antenna arrays on EBG was developed. Here the impedance matrix resulting from the meshing analysis is manipulated by the GA process in order to find the optimal antenna and EBG operated at 2.4 GHz with the goal of targeting a specific fitness function. Furthermore, an investigation of GA on 2×2 printed slot on DGS was also done.