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1
Phansalkar, Nachiket S. "Seismic Substructure Design Workbook". University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1220554481.
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2
Velasco, Cesar A. Morales. "Substructure Synthesis Analysis and Hybrid Control Design for Buildings under Seismic Excitation". Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30367.
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We extend the application of the substructure synthesis method to more complex structures, and establish a design methodology for base isolation and active control in a distributed model of a building under seismic excitation. Our objective is to show that passive and active control complement each other in such an advantageous manner for the case at hand, that simple devices for both types of control are sufficient to achieve excellent response characteristics with very low control forces.
The Rayleigh-Ritz based substructure synthesis method proved to be highly successful in analyzing a structure more complex than the ones previously analyzed with it. Comparing the responses of the hybridly controlled building and the conventional fixed building under El Centro excitation, we conclude that the stresses are reduced by 99.6 %, the base displacement is reduced by 91.7 % and the required control force to achieve this is 1.1 % of the building weight.Ph. D.
3
Patty, Jill Kathleen. "Longitudinal seismic response of concrete substructure-to-steel superstructure integral bridge connections /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3061626.
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Dow, Ryan A. (Ryan Andrew) 1977. "Performance of glass panels under seismic loading". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/84274.
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5
Kim, Jubum. "Behavior of hybrid frames under seismic loading /". Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/10121.
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6
Mohammed, Mohammed Gaber Elshamandy. "GFRP-reinforced concrete columns under simulated seismic loading". Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/10242.
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Abstract : Steel and fiber-reinforced-polymer (FRP) materials have different mechanical and physical characteristics. High corrosion resistance, high strength to weight ratio, non-conductivity, favorable fatigue enable the FRP to be considered as alternative reinforcement for structures in harsh environment. Meanwhile, FRP bars have low modulus of elasticity and linear-elastic stress-strain curve. These features raise concerns about the applicability of using such materials as reinforcement for structures prone to earthquakes. The main demand for the structural members in structures subjected to seismic loads is dissipating energy without strength loss which is known as ductility. In the rigid frames, columns are expected to be the primary elements of energy dissipation in structures subjected to seismic loads.
The present study addresses the feasibility of reinforced-concrete columns totally reinforced with glass-fiber-reinforced-polymer (GFRP) bars achieving reasonable strength and the drift requirements specified in various codes. Eleven full-scale reinforced concrete columns—two reinforced with steel bars (as reference specimens) and nine totally reinforced with GFRP bars—were constructed and tested to failure. The columns were tested under quasi-static reversed cyclic lateral loading and simultaneously subjected to compression axial load. The columns are 400 mm square cross-section with a shear span 1650 mm. The specimen simulates a column with 3.7 m in height in a typical building with the point of contra-flexure located at the column mid-height. The tested parameters were the longitudinal reinforcement ratio (0.63, 0.95 and 2.14), the spacing of the transverse stirrups (80, 100, 150), tie configuration (C1, C2, C3 and C4), and axial load level (20%, 30% and 40%).
The test results clearly show that properly designed and detailed GFRP-reinforced concrete columns could reach high deformation levels with no strength degradation. An acceptable level of energy dissipation compared with steel-reinforced concrete columns is provided by GFRP reinforced concrete columns. The dissipated energy of GFRP reinforced concrete columns was 75% and 70% of the counter steel columns at 2.5% and 4% drift ratio respectively. High drift capacity achieved by the columns up to 10% with no significant loss in strength. The high drift capacity and acceptable dissipated energy enable the GFRP columns to be part of the moment resisting frames in regions prone to seismic activities. The experimental ultimate drift ratios were compared with the estimated drift ratios using the confinement Equation in CSA S806-12. It was found from the comparison that the confinement Equation underestimates values of the drift ratios thus the experimental drift ratios were used to modify transverse FRP reinforcement area in CSA S806-12. The hysteretic behavior encouraged to propose a design procedure for the columns to be part of the moderate ductile and ductile moment resisting frames. The development of design guidelines, however, depends on determining the elastic and inelastic deformations and on assessing the force modification factor and equivalent plastic-hinge length for GFRP-reinforced concrete columns. The experimental results of the GFRP-reinforced columns were used to justify the design guideline, proving the accuracy of the proposed design equations.L’acier et les matériaux à base de polymères renforcés de fibres (PRF) ont des caractéristiques physiques et mécaniques différentes. La résistance à la haute corrosion, le rapport résistance vs poids, la non-conductivité et la bonne résistance à la fatigue font des barres d’armature en PRF, un renforcement alternatif aux barres d’armature en acier, pour des structures dans des environnements agressifs. Cependant, les barres d’armature en PRF ont un bas module d’élasticité et une courbe contrainte-déformation sous forme linéaire. Ces caractéristiques soulèvent des problèmes d'applicabilité quant à l’utilisation de tels matériaux comme renforcement pour des structures situées en forte zone sismique. La principale exigence pour les éléments structuraux des structures soumises à des charges sismiques est la dissipation d'énergie sans perte de résistance connue sous le nom de ductilité. Dans les structures rigides de type cadre, on s'attend à ce que les colonnes soient les premiers éléments à dissiper l'énergie dans les structures soumises à ces charges. La présente étude traite de la faisabilité des colonnes en béton armé entièrement renforcées de barres d’armature en polymères renforcés de fibres de verre (PRFV), obtenant une résistance et un déplacement latéral raisonnable par rapport aux exigences spécifiées dans divers codes. Onze colonnes à grande échelle ont été fabriquées: deux colonnes renforcées de barres d'acier (comme spécimens de référence) et neuf colonnes renforcées entièrement de barres en PRFV. Les colonnes ont été testées jusqu’à la rupture sous une charge quasi-statique latérale cyclique inversée et soumises simultanément à une charge axiale de compression. Les colonnes ont une section carrée de 400 mm avec une portée de cisaillement de 1650 mm pour simuler une colonne de 3,7 m de hauteur dans un bâtiment typique avec le point d’inflexion situé à la mi-hauteur. Les paramètres testés sont : le taux d’armature longitudinal (0,63%, 0,95% et 2,14 %), l'espacement des étriers (80mm, 100mm, 150 mm), les différentes configurations (C1, C2, C3 et C4) et le niveau de charge axiale (20%, 30 % et 40%). Les résultats des essais montrent clairement que les colonnes en béton renforcées de PRFV et bien conçues peuvent atteindre des niveaux de déformation élevés sans réduction de résistance. Un niveau acceptable de dissipation d'énergie, par rapport aux colonnes en béton armé avec de l’armature en acier, est atteint par les colonnes en béton armé de PRFV. L'énergie dissipée des colonnes en béton armé de PRFV était respectivement de 75% et 70% des colonnes en acier à un rapport déplacement latéral de 2,5% et 4%. Un déplacement supérieur a été atteint par les colonnes en PRFV jusqu'à 10% sans perte significative de résistance. La capacité d’un déplacement supérieur et l’énergie dissipée acceptable permettent aux colonnes en PRFV de participer au moment résistant dans des régions sujettes à des activités sismiques. Les rapports des déplacements expérimentaux ultimes ont été comparés avec les rapports estimés en utilisant l’Équation de confinement du code CSA S806-12. À partir de la comparaison, il a été trouvé que l’Équation de confinement sous-estime les valeurs des rapports de déplacement, donc les rapports de déplacement expérimentaux étaient utilisés pour modifier la zone de renforcement transversal du code CSA S806-12. Le comportement hystérétique encourage à proposer une procédure de conception pour que les colonnes fassent partie des cadres rigides à ductilité modérée et résistant au moment. Cependant, l'élaboration de guides de conception dépend de la détermination des déformations élastiques et inélastiques et de l'évaluation du facteur de modification de la force sismique et de la longueur de la rotule plastique pour les colonnes en béton armé renforcées de PRFV. Les résultats expérimentaux des colonnes renforcées de PRFV étudiées ont été utilisés pour justifier la ligne directrice de conception, ce qui prouve l’efficacité des équations de conception proposées.
7
Gubbins, Julie. "Strut action in columns subjected to seismic loading". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33971.
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A series of three reinforced concrete columns was tested under simulated seismic loading to study the effect of the shear span-to-depth ratio on the shear transfer mechanisms. The full size columns were identical in cross section and steel detailing, the only difference being the shear span-to-depth ratio, with ratios of 2.0, 2.5, and 3.0. The specimens were designed and detailed to avoid flexural failure, and were loaded in reversed cyclic shear and moment until failure.This research project studies the two shear transfer mechanisms (compression field and direct strut action) observed in the reinforced concrete members. The capacity and behaviour of each specimen was predicted using a sectional response program (Response 2000), a two-dimensional non-linear finite element program (FIELDS), and the strut and tie method. These predictions, and comparisons with the actual experimental results, are presented and discussed. Guidance is provided for determining suitable strut and tie models to model both the compressive field and direct strut action of such columns.
8
Wallace, J. L. "Behaviour of beam lap splices under seismic loading". Thesis, University of Canterbury. Civil Engineering, 1996. http://hdl.handle.net/10092/9638.
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The results of an investigation into the performance of reinforced concrete beam-column subassemblages containing lap spliced reinforcement in the potential plastic hinge region of a beam are presented. Two specimens were tested with simulated seismic loading. One specimen complied with the New Zealand Concrete Design Code, NZS 3101:1982, except for the placement of the lap splices. The second specimen contained beam reinforcement details from a building constructed in the early 1960s. Current concrete design codes specify lap splices should not be placed in beam potential plastic hinge regions where inelastic reversing stresses are possible during seismic events. During testing the transverse steel specified for the confinement of the lap splices was unable to prevent bond deterioration between the spliced bars once inelastic bar strains had developed at one end of the splice. The failure of the lap splices led to a loss of lateral load capacity and a low level of ductility from the specimen.
Reinforced concrete buildings designed to pre-1970s codes may be considered inadequate when viewed in light of the provisions in current codes for seismic design. The testing of beam details taken from one such building indicates insufficient anchorage existed for the plain longitudinal beam bars in the joint. The loss of bond for the plain bars began in the initial load cycles of the test and led to a lack of specimen stiffness and lateral load capacity. The presence of the lap splices is considered to have accelerated the loss of bond from the bars.
Testing investigating the performance available from plain bar reinforced subassemblages should use anchorage for the bars that represent the conditions in the existing structure. The rapid loss of bond from the bars during cyclic loading can lead to the member end connections influencing the test results.
9
Kurc, Ozgur. "A Substructure Based Parallel Solution Framework for Solving Linear Structural Systems with Multiple Loading Conditions". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6923.
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This study presented a substructure based parallel linear solution framework for the static analysis of linear structural engineering problems having multiple loading conditions. The framework was composed of two separate programs designed to work on PC Clusters having the Windows operating system. The first program was responsible for creating the optimum substructures for the parallel solution and first partitioned the structure in such a way that the number of substructures was equal to the number of processors. Then, the estimated condensation time imbalance of the initial substructures was adjusted by iteratively transferring nodes from the substructures with slower estimated condensation times to the substructures with faster estimated condensation times. Once the final substructures were created, the second program started the solution. Each processor assembled its substructures stiffness matrix and condensed it to the interface with other substructures. The interface problem was solved by a parallel variable band solver. After computing the interface unknowns, each processor calculated the internal displacements and element stresses or forces. Examples which illustrate the applicability and efficiency of this approach were also presented. In these examples, the number of processors was varied from one to twelve to demonstrate the performance of the overall solution framework.
10
Li, Alex C. (Alex Chung-Hsing) 1974. "Effect of seismic loading on steel moment resisting frames". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50061.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1998.Includes bibliographical references (leaves 47-48).
In recent history, the use of Steel Moment Resisting Frames (SMRF) in many structural steel buildings has become popular among many engineers and designers. The use of these moment resisting frames allows for more open spaces between floors and columns than in buildings that use the more traditional braced frame construction. One of the critical aspects of the moment resisting frames is the connections between the beams and the columns. The Northridge earthquake near Los Angeles California in 1994 showed that the existing designs for SMRF connections were inadequate and unstable. As a result, new connection designs were needed for SMRF construction. This thesis will first discuss the causes for the failures of the SMRF connections that were discovered after the Northridge earthquake. Next, new performance and testing requirements for new connection designs will be examined. Lastly, one possible solution, the SidePlate connection system, will be analyzed.
by Alex C. Li.
M.Eng.
11
Eldawie, Alaaldeen Hassan. "COLLAPSE MODELING OF REINFORCED CONCRETE FRAMES UNDER SEISMIC LOADING". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595607477704066.
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Syed, Mohsin Sharifah Maszura Binti. "Behaviour of fibre-reinforced concrete structures under seismic loading". Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/17804.
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The present research is concerned with the modelling of the structural behaviour of steel fibre-reinforced concrete (SFRC) using non-linear finite-element (FE) analysis. Key structural response indicators such as load-deflection curves, strength, stiffness, ductility, energy absorption and cracking were examined. In particular, the potential for fibres to substitute for a reduction in conventional transverse reinforcement was studied. Such reduction is highly desirables in practice as it helps alleviate reinforcement congestion, often experienced in the seismic detailing of critical regions such as beam-column joints. Thus two key parameters were considered, namely reducing transverse reinforcement while increasing the amount of fibres. The reduction in conventional reinforcement was achieved mainly by increasing stirrups spacing (and also by reducing double-hoop arrangement commonly used in seismic detailing of joints). The behaviour of SFRC structural elements was studied under both monotonic and reversed-cyclic loadings (the latter used to mimic seismic action). Emphasis was initially focused on the study of available experimental data describing the effect of steel fibres on the post-cracking response of concrete. Consequently the SFRC constitutive model proposed by Lok and Xiao (1999) was selected. The numerical model was calibrated against existing experimental data to ensure the reliability of the FE predictions. Subsequently, further analyses were carried out investigating three main case studies namely, simply supported beams, two-span continuous (i.e. statically-indeterminate) columns, and both exterior and interior beam-column joints. Parametric studies were carried out covering the full practical range of steel fibre dosages and appropriate amounts of reduction in conventional transverse reinforcement. The results show that steel fibres increase the load-carrying capacity and stiffness (thus enhancing response at both the serviceability and ultimate limit states, which are important design considerations). Fibres were found also to improve ductility (as well as altering the mode of failure from a brittle to a ductile one).
13
Meng, Ronald L. "Design of moment end-plate connections for seismic loading". Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-11082006-133629/.
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Yapar, Ozgur. "Analysis Of Earthquake Loading, Wind Loading And Ice Loading Effects On Guyed Masts". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12612137/index.pdf.
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Guyed masts are special type of structures that are widely used in the telecommunication industry. In the past, there was no guideline for seismic design of these types of structures in the corresponding design codes. On the other hand, in the latest &ldquoG&rdquo
revision of the ANSI/TIA-EIA code there is a comprehensive design criterion for the seismic design of the guyed masts. However, during the design process of these structures the most common approach is to ignore the effect of seismic loading and use only the internal forces developed from the wind load and ice load analysis. In this study firstly the efficiency and accuracy of the commercial SAP2000 and PLS-TOWER software were investigated, then finite element models of three guyed masts that had been designed in Turkey with the heights 30m, 60m and 100m in the SAP2000 and PLS-TOWER software were analyzed under the effect of earthquake, wind and ice loadings. The most common design code recognized all over the world used for the design of the guyed masts is ANSI/TIA-EIA 222-G &ldquo
Structural Standards for Steel Antenna Towers and Supporting Structures&rdquo
. Thus, the corresponding sections of this code were followed during the study. The main objective of this research is to check the correctness of commercial SAP2000 and PLS-TOWER software and to investigate the effect of seismic actions on the guyed masts and also to gain a better understanding of the behavior of guyed masts under the effects of the wind, ice and earthquake loadings.
15
Tsuno, Kazuhiro. "Effect of seismic loading patterns on reinforced concrete bridge piers". Thesis, University of Canterbury. Department of Civil Engineering, 1999. http://hdl.handle.net/10092/2279.
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This research aims to determine the effect of loading pattern on the damage of a
reinforced concrete bridge column.
In the literature review, some common quasi-static loading patterns used in New
Zealand, United States and Japan are summarised, and the standard cyclic loading pattern
which has been used extensively at the University of Canterbury is introduced. The fatigue
based damage model used in this research to estimate the damage of the test specimens
is reviewed, and the de§.ign procedure of a reinforced concrete bridge column using the
latest Japanese specification is summarised.
Five specimens were made and tested with four different cyclic loading patterns; four
specimens were identical and one specimen was constructed with low strength concrete.
The specimens were scale models of a reinforced concrete bridge column designed using
the Japanese specification. Three specimens were cyclically loaded in one direction, and
the other two were bi-directionally loaded, all combined with a uniform axial load.
From the test result, the plastic hinge zone length was calculated and compared to
some theoretical values. Moment-curvature analyses were carried out and the energy
dissipated by the specimens was obtained from the test results. The transition of damage
index was also calculated from the loading history of the tests using a fatigue-based
damage model.
From the result of the analysis, a procedure to predict the failure of a reinforced
concrete column subjected to uni-directionalloading or bi-directionalloading, is proposed.
16
Al-Shaikh, Abdulrahman Hassan. "Cyclic static and seismic loading of laterally confined concrete prisms". Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38219.
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17
Ryan, John Christopher. "Evaluation of Extended End-Plate Moment Connections Under Seismic Loading". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/34981.
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An experimental investigation was conducted to study the extended end-plate moment connections subjected to cyclic loading. Seven specimens representing three end-plate moment connection configurations commonly used in the pre-engineered building industry were used. The connections were designed using yield-line theory to predict end-plate yielding and the modified Kennedy method to predict maximum bolt force calculations including prying action. A displacement controlled loading history was used to load the specimens. The maximum moments obtained experimentally and the experimental bolt forces throughout loading were compared with analytical predictions and finite element model results. The inelastic rotation of connections was calculated and conclusions were drawn on the compliance of these connections with current AISC specifications.Master of Science
18
Aaleti, Sriram R. "Behavior of rectangular concrete walls subjected to simulated seismic loading". [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3389080.
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Nicknam, Ahmad. "Non-linear analysis of reinforced concrete structures subjected to transient forces". Thesis, Heriot-Watt University, 1994. http://hdl.handle.net/10399/1432.
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20
RADAMPOLA, Senanie Sujeewa, i senanie s. radampola@mainroads qld gov au. "EVALUATION AND MODELLING PERFORMANCE OF CAPPING LAYER IN RAIL TRACK SUBSTRUCTURE". Central Queensland University. Centre for Railway Engineering, 2006. http://library-resources.cqu.edu.au./thesis/adt-QCQU/public/adt-QCQU20060817.115415.
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In the design of rail track structures where the subgrade cannot achieve the desired
capacity, enabling the required standard of track geometry to be maintained for the speed,
axle load and tonnage to be hauled, a capping layer of granular material is placed
between the natural ground or the embankment fill material and the ballast to protect the
underlying weaker layers.
In spite of the important role played by the capping layer, very little research has been
carried out on its performance. The current practice of design of the capping layer,
therefore, is based on working stress philosophy where reduced levels of stresses are
assumed not to degrade the subgrade. Even on tracks containing a thick ballast layer that
ensures allowable levels of working stress the subgrade has been found to have
permanently deformed. Design of capping layers based on plastic deformation,
therefore, appears appropriate. This thesis aims at determining the load levels that cause
detrimental plastic deformation in the capping layer.
The suite of material properties that characterise plastic deformations of capping layer is
neither readily available nor easily determined. This thesis proposes a cheaper method of
evaluating a range of capping layer material properties using penetration tests on
specimens contained in California Bearing Ratio (CBR) test moulds coupled with a finite
element modelling based back calculation technique. The suite of material properties
thus determined are used for the simulation of the behaviour of capping layers under the
boundary and loading conditions similar to those in practice. The predicted results are
validated using laboratory experiments on large size capping layer specimens.
21
Elmorsi, Mostafa Saad Eldine. "Analytical modeling of reinforced concrete beam column connections for seismic loading". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0006/NQ42844.pdf.
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22
Richins, Brian D. "Evaluation and Seismically Isolated Substructure Redesign of a Typical Multi-Span Pre-Stressed Concrete Girder Highway Bridge". DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/1064.
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Seismic considerations greatly influence the lateral and vertical design of a structure, often necessitating larger elements than would otherwise be required. Seismic isolation greatly reduces the demands on a structure due to earthquake loading, allowing the use of smaller, more efficient members and foundations. This case study illustrates the theory and procedure of evaluating the response of a recently built multi-span highway bridge using the most recent (2009) AASHTO code. Based on this response, an equivalent structure was designed to incorporate a seismic isolation system, and the substructure of the isolated bridge redesigned to meet the reduced demands more economically. The reduction in demands was quantified, and the member demands and overall responses of the two designs were compared. An overview of isolator design for the common isolator types available in the United States, with examples specific to the isolated structure that was designed, is also included as an addendum.
23
Riederer, Kevin Allen. "Assessment of confinement models for reinforced concrete columns subjected to seismic loading". Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/31503.
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Research conducted over the past several years has shown that factors such as axial load
level and the amount and spacing of confinement steel influence the performance of
reinforced concrete columns subjected to seismic loading. The aim of this research
project was to investigate the performance of the current ACI 318 confining steel
requirements and compare them to other codes and proposed models to determine their
suitability for a performance based design equation for implementation in Chapter 21 of
ACI 318.
The investigation was performed by analyzing the results of multiple reverse-cyclic
column tests presented in the UW/PEER Structural Performance Database. The
condensed database used in this investigation consisted solely of columns which
exhibited flexural failure and contained 145 rectangular and 50 circular columns.
First, a scatter plot was used to compare the confining requirements of each model with
the lateral drift observed for each column within the database. The plot showed the drift
ratio achieved by the column test versus a ratio of lateral steel Ash provided over that
which is required by ACI (Ash provided / Ash ACI)- A drift ratio of 2.5% was selected as the
performance target for the evaluation. Columns were identified as those which satisfied
the requirements of the model but failed the performance target ('unconservative') or
those which failed the requirements of the model but satisfied the performance target
('conservative'). For each model, the percentage of columns falling into these
classifications was calculated and compared.
Two fragility curves were generated for each model which provided the probability of a
column being classified as 'unconservative' or 'conservative' as a function of drift ratio.
A third curve was a combination of the first two and provided insight as to the overall
performance of the model.
For both the rectangular and circular column evaluations, the ACI model was determined
to be the least desirable of all models investigated. Based on the evaluation techniques
developed, specific models were selected as recommended alternatives to the current ACI
requirements. The recommended models minimize the potential of a column experiencing
lateral strength degradation before reaching the prescribed lateral drift limit.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
24
Kwarteng, Kenneth Owusu. "Effects of seismic loading on slender steel structures with semi-rigid joints". Thesis, Oxford Brookes University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.579170.
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A literature review of existing research on rack structures shows that connection models that are often adopted for the study of frame behaviour are usually based on the pre - yield stiffness. Record of experiments carried out and connection models developed from such experiments show that there is no reported study on the post - yielding behaviour of these connections under seismic loads. Seismic excitations often cause connections to rotate well beyond yielding and therefore requiring consideration of the post - yielding stiffnesses which developed in the connections to allow all the excessive stresses developed from the seismic effects to be re - distributed to other parts of the structure in prevention of premature collapse. The current study is an investigation into the semi - rigid and post - yielding behaviour of a beam end connector used in the UK storage rack industry. The pre and post - yielding behaviours of the connection under seismic condition undergo "pinching" which is the degradation of stiffness in the connection as a result of persistent loading and unloading of the beam, causing; significant wear and tear in the connection. The deterioration in the connection is manifested through material yielding, permanent geometric change and fatigue failure. The pinching behaviour in the connection was determined through experiments, which were conducted as part of this research. The experiments showed a steady rise in moment resistance within the elastic range of the connector. In this range every stiffness curve generated from the connection showed a slight deviation from the preceding curve but similar in shape. As the applied loads increased the connection behaved plastically with non recoverable looseness developing around the neutral or zero position as a result of the permanent deformation. There was then a sudden drop in strength followed again by a gradual increase in moment capacity which led to a shape similar to a butterfly wing, a "butterfly -shaped" moment rotation curve. The pinching was associated with significant looseness in the connection and this was shown in the moment rotation curve to get bigger with increases in the number of load cycles and magnitude of the applied load. A connection model to describe the "butterfly shaped" stiffness curve was then developed through regression analysis and this was used for the study of rack frame behaviour under seismic loading. A procedure for non linear dynamic analysis, based on Newton - Raphson and Newmark's methods was developed using stability functions to derive the structural stiffness and the pinching properties of the connections were then incorporated for the study. The research finally gives a revised design methodology, incorporating the pinching behaviour of the connections in comparison with existing design codes.
25
Nichol, Eric Andrew. "Experimental behaviour of inelastic mass-asymetric multi-storey buildings under seismic loading". Thesis, University College London (University of London), 1999. http://discovery.ucl.ac.uk/1318017/.
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Buildings with non coincident centres of mass and stiffness respond in both translation and rotation during seismic ground excitations. This translational and rotational interaction (torsional coupling) can lead to excessive forces in some structural members. This could possibly lead to structural failure if the building is not properly designed to accommodate this response interaction. Previous elastic analytical studies have determined the structural parameters that govern the degree of torsional coupling. However, the parameters found influencing torsional coupling during inelastic response in previous analytical studies have been found to be both more numerous and contradictory than those associated with the elastic response. This study concentrates on the inelastic behaviour of a series of four storey models representing idealized buildings. These building models have been developed from a previous experimental study on the elastic behaviour of torsional coupling. In this inelastic study, hinge units have been designed and used to simulate the yielding of the column or beam members in the experimental model, while maintaining ease of repeatability between tests. The yielding moment in these hinge units can be adjusted to alter the effective strength of the columns or beams in the model. This, along with the ability to vary the floor mass distribution, column sizes (diameter and length), and stiffness distribution allows for a degree of control on the structural parameters deemed important in previous inelastic analytical studies. Results are presented which illustrate the effects that the various structural configurations have on the different measures of inelastic building response, and its vulnerability to damage. These include changes in the building frequencies, member displacement ductilities and vulnerability, hysteretic energy dissipation, and peak structural responses. The study presents a comprehensive investigation of the column-yielding building models. Additionally, select key cases of the column yielding configurations are compared to both the beam-yielding models, and a computational model.
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Manasseh, Mazen 1980. "A web-controllable shaking table for remote structural testing under seismic loading". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29382.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004."June 2004."
Includes bibliographical references (leaf 73).
The thesis presents a remotely accessible system for controlling a shaker table laboratory experiment. The Shake Table WebLab is implemented at MIT's Civil Engineering Department under the Microsoft-sponsored iLab initiative for the development of educationally-oriented virtual experiments. Facilitated accessibility, safe operation and expandability are essentials at the root of the design and implementation of the Shake Table WebLab. The fully functional system allows students and researchers to excite a two-story structure, which is three feet high, by vibrating its base while receiving accelerometer readings from its three levels. Registered Internet users may upload their own input data, such as the seismic ground acceleration of a newly occurring earthquake, and therefore study the corresponding behavior of a real structure. The system is designed with an expandable architecture which enables future researchers to add functionalities that suit their fields of interest. Relevant fields of study include real-time signal processing and filtering techniques that would provide an understanding of how earthquakes affect a structure and therefore provide insight on means to minimize encountered damage in large-scale structures. An already developed tool utilizes frequency domain transfer functions to compare the measured structural response at the upper levels with a predictable result based on seismic vibrations applied at the structure's base. Two main characteristics of the web-based application are interactivity, provided through synchronized control/response processes, and sensor-based monitoring of the experiment.
(cont.) The system is built on the Microsoft .Net Framework through server-hosted Active Server Pages and browser-embedded Windows Form Controls. Web Service methods are implemented for initiating remote processes. Throughout the thesis, I state the motivations for conducting this project, the different online activities and generic administrative features, and a description of the implemented technologies and system components.
by Mazen Manasseh.
S.M.
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Butler, Luke C. "Behavior and Design of Cast-in-Place Anchors under Simulated Seismic Loading". University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382427376.
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Su, Danna. "SEISMIC PERFORMANCE OF HIGHWAY BRIDGES SUBJECTED TO STRONG EARTHQUAKES CONSIDERING VEHICLE-BRIDGE INTERACTION". Kyoto University, 2018. http://hdl.handle.net/2433/232014.
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Akin, Umut. "Seismic Assessment Of Reinforced Concrete Beam-to-column Connections Under Reversed Cyclic Loading". Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613123/index.pdf.
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Prior experimental research clearly reveals that the performance of reinforced concrete frame structures under earthquake loading is closely related to the behavior of beam-to-column connection regions. In order for a reinforced concrete building to have an adequate response under high lateral deformations, beam-to-column connections should be able to preserve their integrity. However, even today beam-to-column connections are assumed to be rigid or elastic, leading to an incorrect estimation of the structural response under earthquake loading. One of the basic reasons for the assumption of rigid joints is the lack of analytical models that adequately represent the seismic behavior of the connection region. In this thesis, an analytical model that realistically represents the beam-to-column connection response is developed, in the light of prior experimental data. The experimental subassemblies used in the generation of the analytical model are later modeled in OpenSees environment in order to verify the accuracy of the model. Throughout the research, utmost attention is paid for the model to be simple enough to be used practically and also to cover a wide range of beam to column connection properties.
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Mitra, Nilanjan. "An analytical study of reinforced concrete beam-column joint behavior under seismic loading /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/10156.
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Tafsirojjaman, Tafsirojjaman. "Mitigation of seismic and cyclic loading actions on steel structures by FRP strengthening". Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/207918/1/Tafsirojjaman_Tafsirojjaman_Thesis.pdf.
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This thesis aimed to develop an effective technique to mitigate the cyclic and seismic loading actions on steel structure by FRP strengthening. Extensive study has been done to understand the structural performance of FRP strengthened steel members, beam-column connections under monotonic and cyclic loading and FRP strengthened steel frames under seismic loading through experimental testing, finite element (FE) modelling and theoretical approach. The developed finite element and theoretical model predicted the structural responses of FRP strengthened steel structures accurately. The results showed that the FRP strengthening can effectively mitigate the cyclic and seismic loading actions on the steel structure.
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Elghazouli, Ahmed Youssef. "Earthquake resistance of composite beam-columns". Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/7906.
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Sumner, Emmett A. "Unified Design of Extended End-Plate Moment Connections Subject to Cyclic Loading". Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28078.
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Experimental and analytical research has been conducted to develop unified design procedures for eight extended end-plate moment connection configurations subject to cyclic/seismic loading. In addition, the suitability of extended end-plate moment connections for use in seismic force resisting moment frames was investigated. Eleven full-scale cyclic and nine monotonic extended end-plate moment connection tests were conducted. Design procedures for determining the required bolt diameter and grade, end-plate thickness, and column flange thickness were developed. The proposed design procedure utilizes a strong column, strong connection, and weak beam design philosophy. This forces the connecting beam to provide the required inelastic deformations through formation of a plastic hinge adjacent to the connection region. The proposed design procedure was used to make comparisons with ninety experimental tests conducted over the past twenty-six years. A limited finite element study was conducted to investigate the behavior of the column flange.
The experimental results demonstrate that extended end-plate moment connections can be detailed and designed to be suitable for use in seismic force resisting moment frames. The proposed design procedure strength predictions correlated well with the results from ninety experimental tests. The limited finite element modeling conducted as a part of this study, correlated well with the strength predictions produced by the proposed design procedure.Ph. D.
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Jackson, Perry Francis. "An investigation into the deformation behaviour of geosynthetic reinforced soil walls under seismic loading". Thesis, University of Canterbury. Department of Civil and Natural Resources Engineering, 2010. http://hdl.handle.net/10092/5522.
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Reinforcement of soil enables a soil slope or wall to be retained at angles steeper than the soil material’s angle of repose. Geosynthetic Reinforced Soil (GRS) systems enable shortened construction time, lower cost, increased seismic performance and potentially improve aesthetic benefits over their conventional retaining wall counterparts such as gravity and cantilever type retaining walls. Experience in previous earthquakes such as Northridge (1994), Kobe (1995), and Ji-Ji (1999) indicate good performance of reinforced soil retaining walls under high seismic loads. However, this good performance is not necessarily due to advanced understanding of their behaviour, rather this highlights the inherent stability of reinforced soil against high seismic loads and conservatism in static design practices.
This is an experimental study on a series of seven reduced-scale GRS model walls with FHR facing under seismic excitation conducted using a shake-table. The models were 900 mm high, reinforced by five layers of stiff Microgrid reinforcement, and were founded on a rigid foundation. The soil deposit backfill was constructed of dry dense Albany sand, compacted by vibration (average Dr = 90%). The influence of the L/H ratio and wall inclination on seismic performance was investigated by varying these important design parameters throughout the testing programme. The L/H ratio ranged from 0.6 – 0.9, and the walls were primarily vertical except for one test inclined at 70o to the horizontal.
During testing, facing displacements and accelerations within the backfill were recorded at varying levels of shaking intensity. Mechanisms of deformation, in particular, were of interest in this study. Global and local deformations within the backfill were investigated using two methods. The first utilised coloured horizontal and vertical sand markers placed within the backfill. The second utilised high-speed camera imaging for subsequent analysis using Geotechnical Particle Image Velocimetry (GeoPIV) software. GeoPIV enabled shear strains to be identified within the soil at far smaller strain levels than that rendered visible by eye using the coloured sand markers. The complementary methods allowed the complete spatial and temporal development of deformation within the backfill to be visualised.
Failure was predominantly by overturning, with some small sliding component. All models displayed a characteristic bi-linear displacement-acceleration curve, with the existence of a critical acceleration, below which deformations were minor, and above which ultimate failure occurs. During failure, the rate of sliding increased significantly.
An increase in the L/H ratio from 0.6 to 0.9 caused the displacement-acceleration curve to be shallower, and hence the wall to deform less at low levels of acceleration. Accelerations at failure also increased, from 0.5g to 0.7g, respectively. A similar trend of increased seismic performance was observed for the wall inclined at 70o to the horizontal, when compared to the other vertical walls.
Overturning was accompanied by the progressive development of multiple inclined shear surfaces from the wall crest to the back of the reinforced soil block. Failure of the models occurred when an inclined failure surface developed from the lowest layer of reinforcement to the wall crest. Deformations largely confirmed the two-wedge failure mechanism proposed by Horii et al. (2004).
For all tests, the reinforced soil block was observed to demonstrate non-rigid behaviour, with simple shearing along horizontal planes as well as strain localisations at the reinforcement or within the back of the reinforced soil block. This observation is contrary to design, which assumes the reinforced soil block to behave rigidly.
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AQUINO, GLADYS CELIA HURTADO. "LIQUEFACTION ASPECTS ON THE STABILITY OF A COPPER ORE HEAP LEACH UNDER SEISMIC LOADING". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31862@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
O fenômeno de liquefação continua sendo um dos temas mais importantes, complexos e controversos da engenharia geotécnica, sendo a liquefação dinâmica, causada por terremotos, o maior contribuinte de risco sísmico urbano em vários países andinos. O movimento causa incrementos da poropressão que reduz a tensão efetiva e conseqüentemente a resistência ao cisalhamento de solos arenosos. O presente trabalho de pesquisa apresenta e compara algumas das metodologias existentes para a avaliação do fenômeno de liquefação dinâmica, variando desde o método semi-empírico de Seed-Idriss para estimativas do potencial de liquefação até a execução de algumas análises numéricas, no contexto dinâmico, através do programa computacional FLAC 2D v.5. Um estudo de caso, para uma comparação dos diversos procedimentos, consiste na análise dinâmica de uma pilha de lixiviação de minério de cobre, situada em região de atividade sísmica no Peru que, devido a problemas no sistema de drenagem interna, resultou com um alto nível de saturação que poderia colocar sua estabilidade em risco devido à possibilidade de liquefação sob carregamento sísmico. Dos resultados obtidos nessas análises, pode-se afirmar que o método semi-empírico de Seed-Idriss, para determinação do potencial de liquefação, compara-se bastante bem com modelos mais sofisticados baseados em análises dinâmicas empregando tanto o modelo constitutivo de Finn quanto o modelo constitutivo elastoplástico UBCSAND.
The phenomenon of liquefaction is still one of the most important, complex and controversial subjects of the geotechnical engineering, being the dynamic liquefaction, caused by earthquakes, the major contributor to urban seismic risks in several Andesian countries. The shaking increases the pore water pressure which reduces the soil effective stress and, therefore, the shear strength of sandy soils. This dissertation presents and compares some of the proposed methodologies to evaluate the phenomenon of dynamic liquefaction, ranging from the semi-empirical method of Seed-Idriss to estimate the liquefaction potential to the execution of some numerical analyses, within the dynamic context, through the computational program FLAC 2D v.5. The case study, for the comparison among the several procedures, consists of a copper ore heap leach, situated in a high seismic activity zone in Peru, that experimented high levels of saturation, due to problems in the internal drainage system, that could put in risk the stability of the leach pad to the possibility of liquefaction under seismic loading. From the results of such analyses, one can say that the semi-empirical method proposed by Seed- Idriss for the determination of the liquefaction potential compares quite well with outputs from more sophisticated numerical analyses based on dynamic studies that incorporate either the Finn s or the elasto-plastic UBCSAND constitutive models.
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Han, Bo. "Hydro-mechanical coupling in numerical analysis of geotechnical structures under multi-directional seismic loading". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/28683.
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This thesis numerically investigates the seismic behaviour of geotechnical structures under multi-directional loading by employing the coupled hydro-mechanical (HM) formulation of the Imperial College Finite Element Program (ICFEP). The scope of the research work can be summarised as follows: Firstly, the stability of the generalised-α method (CH method) for the coupled consolidation formulation, is analytically investigated for the first time and the corresponding theoretical stability conditions are derived. The analytically derived stability conditions are validated by finite element (FE) analyses considering a range of loading conditions and soil permeability values. Secondly, the site response due to the vertical component of the ground motion is systematically investigated by employing analytical and numerical methods. The compressional wave propagation mechanism in saturated porous soils is investigated by the coupled HM formulation. Furthermore, the undertaken coupled FE analyses explore the effects of the parameters characterising the hydraulic phase, i.e. the soil permeability and soil state conditions, on the vertical site response. Thirdly, three-directional (3-D) site response analyses are conducted for the HINO site of the Japanese KiK-net down-hole array earthquake monitoring system. Different aspects of the numerical modelling for the site response analysis, such as the constitutive model, the use of 3-D input motion and the coupled consolidation formulation, are investigated and validated by the recordings from the KiK-net system. Further parametric studies investigate the impact of the variation of the water table, the soil permeability and the 3-D input motion on the multi-directional site response. Finally, the seismic response of a well-documented Chinese rockfill dam, the Yele dam, is investigated with the dynamic plane-strain FE analysis, accounting for the HM coupling and nonlinear soil response. The numerical predictions are compared against the available static and dynamic monitoring data, which allows for a rigorous validation of the developed numerical model. Furthermore, parametric studies of the Yele dam are conducted to explore the effects of several critical factors on the seismic response of rockfill dams, i.e. the reservoir simulation method, the permeability of materials comprising the dam body, the vertical ground motion and the reservoir water level.
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Carbone, Laura. "Interface behaviour of geosynthetics in landfill cover systems under static and seismic loading conditions". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU006/document.
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Les Installations de Stockage de Déchets actuelles sont munies de barrieres de confinement composites géosynthétiques et minerales. En couverture, les interfaces entre composants de ces systèmes installés sur forte pente peuvent constituer des surfaces de glissement préférentiel. L'étude de ces interfaces est donc cruciale pour l'évaluation de la stabilité des barrières de ces installations. Le comportement de ces interfaces, en particuliers des interfaces géosynthétique - géosynthétique se révèle complexe: il va dépendre de la nature des polymères, de l'endommagement , de la vitesse de glissement relatif, de la température. Les conditions de chargement sont aussi primordiales, statiques ou dynamiques (cas de seisme). L'originalité du travail effectué dans le cadre de la présente étude tient d'abord aux dispositifs expérimentaux utilisés en parallèle, un Plan incliné et une Table Vibrante, les deux permettant de simuler les conditions réelles sur site, sous faible contrainte normale, en conditions d'une part statiques, d'autre part dynamiques. Des procédures d'essai nouvelles ont permis une interprétation fine des résultats d'essais. En particulier la variation du frottement en fonction de la cinétique d'essai est clairement démontrée, et le couplage des résultats obtenus dans les deux configurations d'essai permet de montrer que leur interprétation est complexe et ne peut se limiter à celle proposée par la norme européenne. En particulier, le niveau du déplacement relatif et la vitesse de déplacement influent significativement sur les résultats. Une étude spécifique de l'endommagement est aussi présentéeModern landfills are equipped with multi-layered liners, including geosynthetic-geosynthetic and soil-geosynthetic interfaces. The interfaces represent weakness surfaces where the shear strength is a crucial aspect for the landfill stability. The behaviour of each interface can be different depending on the interactions of the materials in contact under the different load conditions (i.e. static and seismic loading). Nevertheless, the assessment of the geosynthetic interface shear strength can be difficult depending on different factors such as mechanical damage, time-dependent processes (ageing), stress dependent processes (such as repeated loading), coupled effects of both time and stress-strain dependent processes (creep or relaxation). In the present work, the static and the dynamic behaviour of typical geosynthetic - geosynthetic interfaces is investigated by means of the Inclined Plane and the Shaking Table tests since both devices permit to simulate experimental conditions close to them expected in landfill cover systems (low normal stress, small and large deformations). Two new test procedures are proposed and applied in order to assess the interface friction at both devices during all the phases of the tests. Taking advantage of the complementarity of both facilities, an innovative interpretation of test results considering the evolution of the shear strength parameters, passing from the static to the dynamic loading conditions, from small to large displacements is carried out. Furthermore, the dependence of the interface friction on different parameters such as the kinematic conditions, the normal stress and the mechanical damage is also investigated. In light of test results, it has been demonstrated that the variation of the interface friction could be significant, depending on the loading conditions (static or dynamic), on the actual kinematic conditions and on the level of deformation at which the interface is subjected
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Azimikor, Nazli. "Out-of-plane stability of reinforced masonry shear walls under seismic loading : cyclic uniaxial tests". Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42113.
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In recent years, widespread application of low-rise masonry construction, including post-disaster buildings like fire halls, has become limited in seismic regions of Canada. This is because the Canadian Masonry Design Standard (CSA S304.1-04) [Canadian Standard Association 2004] mandates stringent requirements on the design of ductile reinforced masonry (RM) shear walls, especially with regard to their height-to-thickness (h/t) ratios, which were restricted to ensure against out-of-plane instability. This failure mechanism has been observed in the end zones of reinforced concrete shear walls loaded in-plane in experimental research and in past earthquakes. However, there is a lack of similar evidence for RM shear walls; this is a motivation for the research program described in this thesis.
The research consists of several major tasks. First, a review of the literature on previous experimental research studies on RM shear walls was conducted, followed by comprehensive investigation into the parameters affecting out-of-plane instability of RM shear walls,. Based on the results of this literature review, the first phase of the experimental program was designed with a focus on modeling the RM wall end zone and understanding the mechanism of lateral instability. Five full-scale specimens representing the wall end zones were constructed and subjected to reversed cyclic axial tension and compression until failure. The effect of varying h/t ratios of the plastic hinge zone, as well as level of axial tensile strain on the out-of-plane instability was examined.
Based on the results of the experimental study, it was concluded that the level of applied tensile strain in the wall end zone is one of the critical factors governing its lateral instability. Therefore, the maximum tensile strain that may be imposed on a moderately ductile RM wall end-zone is determined based on a kinematic relationship between the axial strain and the out-of-plane displacement. A preliminary mechanic model has been proposed to predict the maximum tensile strain before instability takes place. The model can be incorporated into design provisions related to the thickness of shear walls of a given height. A comparison with the experimental results showed that the model offers conservative prediction of the maximum tensile strain.
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Zhang, Xudong (David). "Out-of-plane performance of partially grouted reinforced concrete masonry walls under simulated seismic loading". Thesis, University of Canterbury. Department of Civil Engineering, 1998. http://hdl.handle.net/10092/2251.
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This research project is part of a program reviewing the current masonry code NZS 4229:
1986. It involved testing two full-size partially grouted reinforced concrete masonry walls
with openings subjected to simulated out-of-plane seismic loading. Theoretical studies
were also carried out.
The first specimen was C shaped in plan, 904m long, 204m high, with 1.8m long return
walls at each end, and there were two doorway openings, one at each end of the main
wall. The second specimen plan was the same as the first one, except that there was one
door, one middle window and one comer window.. The walls were founded on the Ribraft
floors; and were constructed using standard 20 series concrete blocks, with vertical
reinforcement D12 at 800mm centres and 2D16 laid horizontally in the top two courses
acted as a bond beam. The amount of reinforcement is the minimum requirement in the
current masonry code NZS 4229: 1986. Only the cells containing reinforcement were
grouted.
The test results showed that both of the specimens exhibited a ductile behaviour with a
"pinched" shape of the hysteresis response, and the load carrying capacities did not
decrease even at the end of tests. The walls were capable of undergoing large amount of
inelastic deformation without collapse. The ultimate loads were 5.4kPa and 6.6kPa for
specimen 1 and 2, which were defined using the codified deflection limit of 2% story
drift in the current loading code NZS 4203: 1992.
The location and size of the openings influence the load resistance significantly. Mortar
strength does not reduce the failure load, but it has a significant effect on the cracking
load. Yield line theory can reasonably predict the out-of-plane strength of partially
grouted reinforced concrete masonry wall, and it gives a conservative prediction. The
experimental and theoretical studies suggest that the current masonry code NZS 4229:
1986 implies some degree of conservatism in application to the use of the partially
grouted reinforced masonry structure.
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Kyakula, Michael. "An improved spread plasticity model for inelastic analysis of R.C. frames subject to seismic loading". Thesis, University of Newcastle Upon Tyne, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399361.
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Zimos, D. K. "Modelling the post-peak response of existing reinforced concrete frame structures subjected to seismic loading". Thesis, City, University of London, 2017. http://openaccess.city.ac.uk/18531/.
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Structural members of reinforced concrete (R/C) buildings designed according to older, less stringent seismic codes are often vulnerable to shear or flexure-shear failure followed by axial failure. Thus, such substandard R/C structures are susceptible to vertical collapse, which pertains to the exceedance of vertical resistance of columns and connecting beams and can lead to the whole structure – or a substantial part of it – undergoing collapse. The largest database of shear and flexure-shear critical R/C columns cycled well beyond the onset of shear failure and/or up to the onset of axial failure is compiled and empirical relationships are developed for key parameters affecting the response of such members after the initiation of shear failure. A novel shear hysteresis model is proposed employing these relationships, based on experimental observations that deformations after the onset of shear failure tend to concentrate in a specific member region. A computationally efficient finite element model of the member-type is proposed, using the above shear hysteretic model and combining it with displacements arising from flexural and bond-slip deformations to get the full lateral force-lateral displacement response. It accounts for the interaction between flexural and shear deformations inside the potential plastic hinges, the distribution of flexural and shear flexibility along the element, as well as the location and extent of post-peak shear damage, without relying on assumptions about the bending moment distribution and avoiding shortcomings of previous beam-column models pertinent to numerical localisation. Thus, the full-range hysteretic response of substandard R/C elements can be predicted up to the onset of axial failure subsequent to shear failure with or without prior flexural yielding, while simultaneously accounting for potential flexural and anchorage failure modes. The proposed model is implemented in a finite element structural analysis software and its predictive capabilities are verified against quasi-static cyclic and shake-table test results of column and frame specimens. The model is shown to be sufficiently accurate not only in terms of total response, but more crucially in terms of individual deformation components. Overall, it is believed that the accuracy, versatility and simplicity of this model make it a valuable tool in seismic analysis of complex substandard R/C buildings. An experimental investigation of shear and flexure-shear critical R/C elements is carried out with the aim of independently validating the beam-column model. Furthermore, an opportunity is provided to verify the model’s underlying assumptions, which is of paramount importance for the reliability of its analytical predictions. The experiments were designed in such a manner as to investigate the effect of vertical load redistribution from axially failing members on the lateral post-peak response of neighbouring columns.
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Benamer, Mohamed R. Omar. "Computational modelling of hysteresis and damage in reinforced concrete bridge columns subject to seismic loading". Thesis, Swansea University, 2013. https://cronfa.swan.ac.uk/Record/cronfa42309.
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Box-girder bridges supported by single reinforced concrete (RC) columns are expected to sustain seismic shocks with minor structural damages in seismically active regions where transportation is substantially required for rescuing and evacuating tasks. Such viaducts are vulnerable to damage when they are subjected to strong ground motions and acceleration pulse records, especially when responding in a flexural mode or having relatively low core confinement. Using a nonlinear dynamic solver that applies the fibre element method, global and local damage curves are computed based on the dissipated energy under hysteretic curves and based on constitutive curves, respectively. The RC bridge with seismic isolation bearing is used as an alternative system to control the damage, and modelled using linkage elements between the substructure and super structure. It was found that seismic isolation can be controlled to dissipate partial seismic energy so that the RC column gains the least possible minor damage. Using a MatLab program, a fibre element nonlinear model was built using a simplified iterative process and simplified constitutive relations. The number of fibres and elements under the dynamic loading was found to be affecting the final results of the analysis. Using crack growth modelling based on fracture mechanics, the combined discrete element/finite element explicit-Elfen code was applied to investigate the crack growth in 3D dynamically loaded RC columns. Despite its excessive computational cost and time, this code provides reliable information about local damage in the RC column core. Earthquake records with the pulse acceleration phenomenon have a severe damage potential on the structure. The difference in damage intensities was detected by crack growth modelling for the same problem using different loading rates. Critically stressed zones can be investigated independently by using the relative response technique, in which responses from the numerically analysed structure are re-used as applied loads onto a small-scale crack model for the critical member. Two general conclusions can be obtained; bridges with single RC columns designed by the demand/capacity criterion could suffer severe damage and possible collapse when subjected to strong ground motions. Secondly; hysteresis-based methods provide a global damage evaluation based on strength and ductility only regardless of the damage growth inside the concrete core and the buckling of bars, which could lead to progressive collapse.
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Ghaemi, Arman. "Development of empirical approaches to estimate the seismic settlement of embankment dams under earthquake loading". Doctoral thesis, Université Laval, 2021. http://hdl.handle.net/20.500.11794/69816.
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La contribution significative de cette thèse se situe dans le domaine de la déformation sismique de différents types de barrages en enrochement. La déformation excessive permanente à la crête d’un barrage causée par les secousses du sol menacera la sécurité du barrage. Les caractéristiques de ces barrages et la gravité des tremblements de terre (quantifiée par des mesures d’intensité, c’est-à-dire des IM) sont identifiées comme les composants les plus critiques impliquées dans la performance sismique du barrage. Dans la première partie, une étude est réalisée sur la déformation sismique (tassement de la crête) des barrages en enrochement avec masque en béton (CFRD) et sa corrélation avec les IM de mouvements de sol. De cette manière, l’importance des principales caractéristiques des charges cycliques dans une étude de cas CFRD typique modélisée numériquement est soulignée. On en conclut qu’en plus de l’amplitude et de la durée du mouvement de sol, la réponse du barrage est fortement affectée par les caractéristiques de fréquence du séisme. En rassemblant les histoires de cas de CFRD disponibles et en analysant leur tassement sismique, un nouveau IM est proposé pour décrire efficacement le potentiel d’un séisme à induire un règlement dans les CFRD. Une nouvelle relation prédictive est alors établie qui relie la IM suggérée et l‘amplitude du tremblement de terre avec le tassement de crête étudié des cas CFRDs. Dans la deuxième partie, les données disponibles pour les barrages en enrochement à noyau de terre (ECRD) comprenant les valeurs de tassement rapportées et les mouvements de sol enregistrés lors des tremblements de terre sont analysées. Deux nouvelles approches sont développées en introduisant deux nouveaux IM et en les corrélant au règlement observé des cas ECRD. Les IM proposés pour les ECRD prennent en compte l’influence des aspects essentiels concernant le comportement non linéaire des barrages lors de séismes violents: dégradation de la rigidité des matériaux, augmentation de l’énergie dissipée et augmentation des périodes de vibration des barrages. Ces problèmes sont affectés par la déformation induite par le tremblement de terre, à travers laquelle la corrélation avec la déformation d'un barrage est découverte. Les analyses ont montré que l'occurrence du tassement est directement affectée par les amplitudes de déformation de cisaillement. Compte tenu de l'importance de la déformation de cisaillement, la dernière partie de cette thèse est consacrée aux caractéristiques dépendantes de la déformation des ECRD. À cette fin, des études empiriques ont été menées sur plusieurs séries chronologiques d'accélération pour les ECRD qui avaient été frappés par des tremblements de terre au Japon. Une série de graphiques et de relations a été établie pour estimer: (i) l'amplitude de la déformation de cisaillement induite; (ii) la diminution du module de cisaillement des noyaux des barrages; et (iii) augmentation des périodes fondamentales des barrages. Cette thèse fournit un assemblage approprié d'outils qui peuvent être utilisés dans la pratique de l'ingénierie, que ce soit à des fins d'analyse dynamique ou de conception. Les graphiques et les relations présentés ici sont basés sur l'examen et l'analyse de la performance réelle de nombreux barrages sous les tremblements de terre. Ils répondent non seulement aux lacunes des méthodes empiriques précédentes, mais sont également précis et efficaces.The significant contribution of this thesis is in the area of earthquake-induced deformation of different types of rockfill dams. The permanent excess deformation at a dam’s crest caused by ground-shaking will threaten the dam’s safety. The characteristics of these dams and the severity of the earthquakes (quantified by intensity measures, i.e., IMs) are identified as the most critical components involved in the dam’s seismic performance. In the first part, a study is performed on the seismic deformation (crest settlement) of concrete-face rockfill dams (CFRDs) and its correlation with ground motion IMs. In this way, the importance of cyclic loads’ main characteristics on a numerically modelled typical CFRD case study is underlined. It is concluded that in addition to the amplitude and duration of ground motion, the dam’s response is strongly affected by the frequency characteristics of the earthquake. By gathering available CFRD case histories and analyzing their seismic settlement, a new IM is proposed to efficiently describe an earthquake’s potential to induce settlement in CFRDs. A new predictive relationship is then established which relates the suggested IM and earthquake magnitude with the surveyed crest settlement of the CFRD cases. In the second part, the data available for earth-core rockfill dams (ECRDs) comprising the reported settlement values and the ground motions recorded during the earthquakes are analyzed. Two novel approaches are developed by introducing two new IMs and correlating them to the observed settlement of the ECRD cases. The IMs proposed for ECRDs take into account the influence of the essential aspects regarding the nonlinear behaviour of the dams during severe earthquakes: stiffness degradation of the materials, increase in dissipated energy, and increase in the dams’ periods of vibration. These issues are affected by the earthquake-induced strain, through which the correlation with a dam’s deformation is discovered. The analyses showed that the occurrence of settlement is directly affected by the shear strain amplitudes. Given the importance of the shear strain, the last part of this thesis is devoted to the strain-dependent characteristics of ECRDs. To this end, empirical studies were performed on several acceleration time series for ECRDs that had been struck by earthquakes in Japan. A series of graphs and relationships were established to estimate: (i) the amplitude of the induced shear strain; (ii) the decreased shear modulus of the dams’ cores; and (iii) increased fundamental periods of the dams. This thesis provides an appropriate assembly of tools that can be utilized in engineering practice, either for dynamic analysis or design purposes. The graphs and relationships presented herein are based on reviewing and analyzing the actual performance of numerous dams under earthquakes. They not only address the shortcomings of previous empirical methods, but are also accurate and efficient.
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Bruce, Trevor Louis. "Behavior of Post-Tensioning Systems Subjected to Inelastic Cyclic Loading". Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/49111.
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Post-tensioning (PT) strands have been employed in a number of self-centering seismic force resisting systems as part of the restoring force mechanism which virtually eliminates residual building drifts following seismic loading. As a result of the PT strands large elastic deformation capability, they have been proven to work efficiently in these types of systems. Although typically designed to stay elastic during design basis earthquake events, strands may experience inelastic cyclic loading during extreme earthquakes. Furthermore, the yielding and fracture behavior of PT strand systems is central to the collapse behavior of self-centering systems. The loading conditions to which PT strands are typically subjected in prestressed/post-tensioned concrete applications are vastly dissimilar, and only limited research has explored the behavior of PT strands as subjected to inelastic cyclic loading.
The testing program conducted to characterize the behavior of PT strand systems as they might be applied in self-centering applications incorporated more than fifty tests, including monotonic and cyclic tests to failure. Variations in the test configuration included strand obtained from two manufacturers, single-use and multiple-use anchorage systems, and variations in initial post-tensioning strand stress. Characteristics of the response that were investigated included seating losses, deformation capacity prior to initial fracture, additional deformation capacity after initial fracture, and the overall load-deformation behavior. Data was analyzed to provide recommendations for PT strand system usage in self-centering seismic force resisting systems. It was concluded that significant strength and ductility allow PT strand systems to consistently provide self-centering systems with reliable restoring force capability.Master of Science
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Akguzel, Umut. "Seismic Performance of FRP Retrofitted Exterior RC Beam-Column Joints under Varying Axial and Bidirectional Loading". Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2011. http://hdl.handle.net/10092/5993.
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Most of the experimental studies available in literature on the seismic assessment and retrofit of existing, poorly detailed, reinforced concrete (RC) beam-column joints typical of pre-1970s construction practice have concentrated on the two-dimensional (2D) response, using unidirectional cyclic loading testing protocols and a constant column axial load. Even more limited information is available on the performance of corner three-dimensional (3D) RC beam-column joints with substandard detailing subjected to a bidirectional-loading regime. In addition, little effort has been dedicated to the development of simple but reliable analysis and design procedure for FRP-strengthened joints.
This thesis aims to (1) investigate the effects of varying axial and bidirectional loading on the seismic performance of deficient exterior RC beam-column joints before and after retrofit and (2) develop performance-based seismic assessment and FRP-based retrofit procedures for exterior and corner beam-column joints. For this purpose, following a critical review on the seismic vulnerability of both existing and retrofitted exterior and corner beam-column joints under varying and bidirectional loading demands, a comprehensive experimental programme along with analytical and numerical studies are carried out.
A performance-based retrofit approach was adopted in order to achieve the desired ductile failure mode by modifying the hierarchy of strength within the beam-column joint system. In order to achieve this, existing retrofit design methodology available in literature was refined and a step-by-step procedure was proposed for the assessment of the as-built and proceeding retrofit design of FRP-retrofitted exterior beam-column joints. In addition, the role and importance of accounting for the correct demand conditions (e.g., the variation of axial loads) in the assessment of the existing joint and the design of the FRP retrofit scheme were discussed. In order to assist the retrofit design and assessment procedure a semi-empirical analytical model was developed to evaluate the joint shear resistance after FRP retrofit. Both the proposed assessment methodology and design procedure along with the analytical procedure were verified by experimental studies performed in this thesis and experimental tests available in the literature. Parametric analyses were also carried out to indicate the
Umut Akguzel Seismic Performance of FRP Retrofitted Exterior RC Beam-Column Joints
under Varying Axial and Bidirectional Loading
effectiveness of strengthening with different materials, configurations and failure limit states.
The feasibility and efficiency of a retrofitting intervention using GFRP composites were investigated based on the quasi-static cyclic tests conducted on four 2D exterior (plane frame) and two 3D corner (space frame) RC joints. All specimens were of 2/3 scale, designed according to pre-1970s construction practice. The properties of the specimens are summarized briefly as follows:
(1) Specimen 2D1 was tested under varying axial load as an exterior 2D benchmark unit;
(2) Specimen 2D2 was tested under constant axial load with minimum retrofit solution designed according to the proposed methodology;
(3) Specimen 2D3 was tested under varying axial load with the same retrofit scheme adopted in 2D2; (4) Specimen 2D4 was tested under varying axial load with improved retrofit scheme;
(5) Specimen 3D1 was tested under bidirectional loading with varying axial load as a benchmark;
(6) Specimen 3D2 was tested under bidirectional loading with varying axial load with improved retrofit scheme adopted in Specimen 2D4.
The test outcomes highlighted the potentially unconservative effects of neglecting the actual multiaxial load demand, when assessing the behaviour of existing beam-column joints and designing a proper retrofit intervention. Corner beam-column joints within a frame building were confirmed to be particularly vulnerable. However, with an adequate retrofit design accounting for the multiaxial load effects, the implemented retrofit solutions provided the necessary improvements of the behaviour of the as-built specimens. This resulted in the development of a more appropriate hierarchy of strength with the formation of plastic hinges in the beam and protection of the weaker mechanisms. The experimental findings were also used to identify the critical damage limit states and engineering parameters to be adopted within the framework of performance-based seismic retrofit design.
In addition to the experimental and analytical studies, FEM numerical studies based on microplane concrete model approach were carried out. Three-dimensional finite element (FE) models for retrofitted 2D exterior joint (Specimen 2D2) and as-built 3D corner joint (Specimen 3D1) were developed and analysed. The analysis results showed good agreement with the experimental results.
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Beni, Assa. "Response of Reinforced Concrete Beam-Columns and Frames to Lateral Seismic Loading Based on Material Properties". Kyoto University, 1997. http://hdl.handle.net/2433/202352.
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Forsgren, Erik, i Isak Berneheim. "Behavior of Swedish Concrete Buttress Dams at Sesmic Loading". Thesis, KTH, Betongbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189237.
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The aim of the thesis is to study the response of Swedish buttress dams if they are subjected to an earthquake of relevant magnitude to Sweden. Swedish dams are evaluated for an extensive amount of load cases, but not for earthquake loading. Therefore, it is not known how the Swedish buttress dams would respond during such loading. Earthquake engineering is practised only to a marginal extent in Sweden due to a low risk of major earthquakes. In fact, an earthquake hazard zonation map that provides data for earthquake resistant design, does not even exist for Sweden. Therefore, part of the thesis is aimed at acquiring data from alternative sources to enable seismic evaluation. The effect of earthquakes on Swedish buttress dams are analysed through case studies. The case studies are performed with numerical analysis using the commercial finite element program Brigade Plus. The case studies are performed on two buttress dam models that were selected based on an inventory of Swedish buttress dams. In the case studies, the dam models are evaluated for the Safety Evaluation Earthquake (SEE), which correspond to 10 000 years return period. At the SEE event, the Peak Ground Acceleration (PGA), is also related to the geographical location of a dam. The envelope of available PGA in Sweden was used in the case studies to cover the spectrum of PGA. The response of the dams to the lowest value of PGA is insignificant and the dams are essentially unaffected. However, for the highest value of PGA the responses indicates that the concrete of the dams is severely cracked and that the ultimate capacity of the reinforcement may be exceeded. Hence, it is concluded that the geographical location of a Swedish dam is highly influential on the response to earthquake loading.Syftet med denna uppsats är att analysera effekten på svenska betonglamelldammar i det fall de utsätts för en jordbävning av relevant magnitud för Sverige. Svenska dammar har blivit utvärderade för ett stort antal lastfall, dock ej för jordbävningslaster. Det är därför inte känt hur svenska betonglamelldammar uppträder under sådana laster. Jordbävningsdimensionering tillämpas endast marginellt i Sverige eftersom det föreligger låg risk för kraftfulla jordbävningar. Faktum är att en zonindelningskarta över jordbävningsrisk för byggnadsdimensionering inte ens existerar i Sverige. Därför dedikeras en del av uppsatsen till att hitta data från alternativa källor för seismisk utvärdering. Effekten av jordbävningar på svenska betonglamelldammar analyseras genom fallstudier. Dessa är genomförda baserat på numerisk analys med det kommersiella finita element programmet Brigade Plus. Analyserna är baserade på två utvalda betonglamelldammodeller som valdes genom en inventering av svenska betonglamelldammar. I fallstudien utvärderas dammarna för en Säkerhet Utvärderings Jordbävning (SUJ), denna motsvaras av 10 000 års återkomsttid. Vid en SUJ relateras den Maximala Mark Accelerationen (MAA) även till det geografiska läget av en damm. Ytterlighetsvärdena av tillgänglig MMA värden i Sverige användes i fallstudien för att täcka in hela spektrumet. Effekten av det lägsta MMA värdet på dammarna är obetydlig och dammarna kan anses i stort sett opåverkade. Det högsta värdet av MMA indikerar dock att dammarnas betong utsätts för stor uppsprickning och att kapaciteten av armeringen överskrids. Det kan därmed fastslås att det geografiska läget av en damm har stort inflytande över vilken effekt som kan förväntas vid en jordbävning
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Allington, Christopher James. "Seismic Performance of Moment Resisting Frame Members Produced from Lightweight Aggregate Concrete". Thesis, University of Canterbury. Civil Engineering, 2003. http://hdl.handle.net/10092/1254.
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A total of 47 lightweight aggregate concrete columns were constructed from four different types of lightweight aggregate and provided with different quantities of transverse reinforcement. The specimens were tested under a monotonically increasing level of compressive axial load. The rate of load application was varied from pseudo-static to the rate of dynamic loading expected during a major seismic excitation. The results from the experimental testing of the column members were used to derive a theoretical stress-strain model to predict the behaviour of lightweight aggregate concrete members under imposed loads. The stress-strain model was derived to predict the response of both lightweight aggregate and conventional weight concretes with compressive strengths up to and including 100 MPa. The model was calibrate against the experimental results obtained in this study and previously tested lightweight aggregate and conventional weight concrete columns. A series of pseudo-cyclic moment-curvature analyse were undertaking using the derived stress-strain model, to predict the behaviour of the lightweight aggregate concrete members when subjected to axial load and flexure. The results were compared to the confinement requirements in the potential plastic hinge regions of column elements required by the New Zealand Concrete Structures Standard, NZS3101: 1995. It was determined that the confinement requirements of NZS3101: 1995 were could be used to accurately determine the required quantity of transverse reinforcement for lightweight aggregate concrete members with a concrete density greater than 1700 kg/m3. A total of four lightweight aggregate concrete beam column subassemblies were constructed and tested under reversed cyclic lateral loading. The results from the specimen indicate that cyclic behaviour of the lightweight aggregate concrete was similar to conventional weight concrete. However the bond capacity between the longitudinal reinforcement and the surrounding concrete was weaker than previously tested conventional weight concrete members.
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Niraula, Manjil. "BEHAVIOR AND DESIGN OF THE CRITICAL MEMBER IN STRUCTURES WITH IN-PLANE DISCONTINUOUS BRACED FRAMES". OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2751.
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When a structure with an in-plane discontinuous frame is used, a discontinuous load path is formed due to the irregularity. This is continuous load path can lead to the failure of certain elements and the structure as a whole when the structure is exposed to lateral loading. In this study, an in-plane discontinuous frame structure is exposed to gravity as well as lateral loading due to which a discontinuous load path is formed. Due to the discontinuous load path, higher value of axial load is developed on a beam which is generally designed considering it as a flexural member. The main objective of this thesis is to determine if the beam can be designated as the critical member in the in-plane discontinuous frame and the comparison of the critical element with the corresponding element in a frame that has no structural irregularities. The objective is also to design the critical member considering it as a beam-column element considering the combined effect of bending and compression.
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Mohamed, Fathi Mohamed Omar. "Bearing Capacity and Settlement Behaviour of Footings Subjected to Static and Seismic Loading Conditions in Unsaturated Sandy Soils". Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30661.
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Several studies were undertaken by various investigators during the last five decades to better understand the engineering behaviour of unsaturated soils. These studies are justified as more than 33% of soils worldwide are found in either arid or semi-arid regions with evaporation losses exceeding water infiltration. Due to this reason, the natural ground water table in these regions is typically at a greater depth and the soil above it is in a state of unsaturated conditions. Foundations of structures such as the housing subdivisions, multi-storey buildings, bridges, retaining walls, silos, and other infrastructure constructed in these regions in sandy soils are usually built within the unsaturated zone (i.e., vadose zone). Limited studies are reported in the literature to understand the influence of capillary stresses (i.e., matric suction) on the bearing capacity, settlement and liquefaction potential of unsaturated sands. The influence of matric suction in the unsaturated zone of the sandy soils is ignored while estimating or evaluating bearing capacity, settlement and liquefaction resistance in conventional engineering practice. The focus of the research presented in the thesis has been directed towards better understanding of these aspects and providing rational and yet simple tools for the design of shallow foundations (i.e., footings) in sands under both static and dynamic loading conditions.
Terzaghi (1943) or Meyerhof (1951) equations for bearing capacity and Schmertmann et al. (1978) equation for settlement are routinely used by practicing engineers for sandy soils based on saturated soil properties. The assumption of saturated conditions leads to conservative estimates for bearing capacity; however, neglecting the influence of capillary stresses contributes to unreliable estimates of settlement or differential settlement of footings in unsaturated sands. There are no studies reported in the literature on how capillary stresses influence liquefaction, bearing capacity and settlement behavior in earthquake prone regions under dynamic loading conditions. An extensive experimental program has been undertaken to study these parameters using several specially designed and constructed equipment at the University of Ottawa.
The influence of matric suction, confinement and dilation on the bearing capacity of model footings in unsaturated sand was determined using the University of Ottawa Bearing Capacity Equipment (UOBCE-2011). Several series of plate load tests (PLTs) were carried out on a sandy soil both under saturated and unsaturated conditions. Based on these studies, a semi-empirical equation has been proposed for estimating the variation of bearing capacity with respect to matric suction. The saturated shear strength parameters and the soil water characteristic curve (SWCC) are required for using the proposed equation. This equation is consistent with the bearing capacity equation originally proposed by Terzaghi (1943) and later extended by Meyerhof (1951) for saturated soils. Chapter 2 provides the details of these studies.
The cone penetration test (CPT) is conventionally used for estimating the bearing capacity of foundations because it is simple and quick, while providing continuous records with depth. In this research program, a cone penetrometer was specially designed to investigate the influence of matric suction on the cone resistance in a controlled laboratory environment. Several series of CPTs were conducted in sand under both saturated and unsaturated conditions. Simple correlations were proposed from CPTs data to relate the bearing capacity of shallow foundations to cone resistance in saturated and unsaturated sands. The details of these studies are presented and summarized in Chapter 3.
Standard penetration tests (SPTs) and PLTs were conducted in-situ sand deposit at Carp region in Ottawa under both saturated and unsaturated conditions. The test results from the SPTs and PLTs at Carp were used along with other data from the literature for developing correlations for estimating the bearing capacity of both saturated and unsaturated sands. The proposed SPT-CPT-based technique is simple and reliable for estimation of the bearing capacity of footings in sands. Chapter 4 summarizes the details of these investigations.
Empirical relationships were proposed using the CPTs data to estimate the modulus of elasticity of sands for settlement estimation of footings in both saturated and unsaturated sands. This was achieved by modifying the Schmertmann et al. (1978) equation, which is conventionally used for settlement estimations in practice. Comparisons are provided between the three CPT-based methods that are commonly used for settlement estimations in practice and the proposed method for seven large scale footings in sandy soils. The results of the comparisons show that the proposed method provides better estimations for both saturated and unsaturated sands. Chapter 5 summarizes the details of these studies.
A Flexible Laminar Shear Box (FLSB of 800-mm3 in size) was specially designed and constructed to simulate and better understand the behaviour of model surface footing under seismic loads taking account of the influence of matric suction in an unsaturated sandy soil. The main purpose of using the FLSB is to simulate realistic in-situ soils behaviour during earthquake ground shaking. The FLSB test setup with model footing was placed on unidirectional 1-g shake table (aluminum platform of 1000-mm2 in size) during testing. The resistance of unsaturated sand to deformations and liquefaction under seismic loads was investigated. The results of the study show that matric suction offers significant resistance to liquefaction and settlement of footings in sand. Details of the equipment setup, test procedure and results of this study are presented in Chapter 6.
Simple techniques are provided in this thesis for estimating the bearing capacity and settlement behaviour of sandy soils taking account of the influence of capillary stresses (i.e., matric suction). These techniques are consistent with the methods used in conventional geotechnical engineering practice. The studies show that even low values of capillary stresses (i.e., 0 to 5 kPa) increases the bearing capacity by two to four folds, and the settlement of footings not only decreases significantly but also offers resistance to liquefaction in sands. These studies are promising and encouraging to use ground improvement techniques; such as capillary barrier techniques to maintain capillary stresses within the zone of influence below shallow foundations. Such techniques, not only contribute to the increase of bearing capacity, they reduce settlement and alleviate problems associated with earthquake effects in sandy soils.