Tesis sobre el tema "SEISMIC FORCE"
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Leaf, Timothy D. "Investigation of the vertical distribution of seismic forces in the static force and equivalent lateral force procedures for seismic design of multistory buildings /". Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1136093311&sid=1&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Manafpour, Alireza. "Force and displacement-based seismic design of RC buildings". Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398834.
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ZERBIN, Matteo. "Force-Based Seismic Design of Dual System RC Structures". Doctoral thesis, Università degli studi di Ferrara, 2017. http://hdl.handle.net/11392/2488041.
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Seismic design of standard structures is typically based on a force-based design approach. Over the years, this approach has proven to be robust and easy to apply by design engineers and – in combination with capacity design principles – it provided a good protection against premature structural failures. However, it is also known that the force-based design approach as it is implemented in the current generation of seismic design codes suffers from some shortcomings. One of these relates to the fact that the base shear is computed using a pre-defined force reduction factor, which is constant for a certain type of structural system. As a result of this, for the same design input, structures of the same type but different geometry are subjected to different ductility demands and show therefore a different performance during an earthquake. The objective of this research is to present an approach for computing force reduction factors using simple analytical models. These analytical models describe the deformed shape at yield and ultimate displacement of the structure and only require input data that are available when starting the design process, such as geometry and general material properties. The displacement profiles are obtained from section dimensions and section ductility capacities that can be estimated at the beginning of the design process. The so computed displacement ductility is taken as proxy of the force reduction factor. Such analytical models allow to link global to local ductility demands and therefore to compute an estimate of the force ductility reduction factors for wall and frame structures. Finally, this research develops an approach for frame-wall structures as combination of results obtained for wall and frame systems. The proposed method is applied to a set of frame-wall structures and validated by means of nonlinear time history analyses. Obtained results show that the proposed method yields a more accurate seismic performance than the current code design approach. The presented work therefore contributes to the development of revised force-based design guidelines for the next generation of seismic design codes.La progettazione sismica di strutture è tipicamente basato su un approccio progettuale basato sulle forze. Nel corso degli anni, questo approccio ha dimostrato di essere robusto e facile da applicare dai progettisti e, in combinazione con il principio di gerarchia delle resistenze, fornisce una buona protezione contro i meccanismi di collasso fragili. Tuttavia, è anche noto che l'approccio di progettazione in forze così come attuato nell’odierna generazione di normative soffre di alcune carenze. Uno di questi riguarda il fatto che il tagliante alla base è calcolato utilizzando un fattore di struttura predefinito, cioè costante per tipo di sistema strutturale. Di conseguenza, per lo stesso input di progettazione, strutture dello stesso tipo ma diversa geometria sono sottoposti ad una diversa domanda di duttilità e mostrano quindi una diversa prestazione durante un evento sismico. L'obiettivo di questo studio è quello di presentare un approccio per il calcolo fattori di struttura utilizzando modelli analitici semplici. Questi modelli analitici descrivono la deformata a snervamento e spostamento ultimo della struttura e richiedono solo dati di input disponibili all’inizio del processo di progettazione, quali dati geometrici e proprietà dei materiali. La deformata della struttura ottenuta dalle dimensioni delle sezioni e la capacità in termini di duttilità sezionale possono essere stimati all'inizio della progettazione. La duttilità è alla base della formulazione del fattore di struttura come proposto dai modelli analitici presentati. Tali modelli analitici permettono di collegare le duttilità sezionali alla duttilità strutturale e quindi calcolare una stima del fattore di struttura per struttura a pareti e a telaio. Infine, si sviluppa un approccio per strutture duali di tipo telaio-parete come combinazione di risultati ottenuti per i sistemi singoli. Il metodo proposto è applicato ad un insieme di strutture duali e validato con analisi dinamiche non lineari. Si dimostra che il metodo proposto produce una più accurata prestazione sismica rispetto all'approccio progettuale delle normative odierne. Il lavoro presentato contribuisce pertanto allo sviluppo di nuove linee guida per la progettazione sismica nella prossima generazione di normative.
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Hague, Samuel Dalton. "Eccentrically braced steel frames as a seismic force resisting system". Kansas State University, 2013. http://hdl.handle.net/2097/15610.
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Master of ScienceDepartment of Architectural Engineering
Kimberly Waggle Kramer
Braced frames are a common seismic lateral force resisting system used in steel structure. Eccentrically braced frames (EBFs) are a relatively new lateral force resisting system developed to resist seismic events in a predictable manner. Properly designed and detailed EBFs behave in a ductile manner through shear or flexural yielding of a link element. The link is created through brace eccentricity with either the column centerlines or the beam midpoint. The ductile yielding produces wide, balanced hysteresis loops, indicating excellent energy dissipation, which is required for high seismic events. This report explains the underlying research of the behavior of EBFs and details the seismic specification used in design. The design process of an EBF is described in detail with design calculations for a 2- and 5-story structure. The design process is from the AISC 341-10 Seismic Provisions for Structural Steel Buildings with the gravity and lateral loads calculated according to ASCE 7-10 Minimum Design Loads for Buildings and Other Structures. Seismic loads are calculated using the Equivalent Lateral Force Procedure. The final member sizes of the 2-story EBF are compared to the results of a study by Eric Grusenmeyer (2012). The results of the parametric study are discussed in detail.
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Fuqua, Brandon W. "Buckling restrained braced frames as a seismic force resisting system". Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1131.
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Li, Xinrong. "Reinforced concrete columns under seismic lateral force and varying axial load". Thesis, University of Canterbury. Civil Engineering, 1994. http://hdl.handle.net/10092/7593.
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The project is carried out with the intention to study the strength and ductility of reinforced concrete columns subjected to simulated seismic horizontal loading and varying axial load.
First, an extensive review of previous research on the behaviour of reinforced concrete members and hysteretic modelling is provided.
Then, the experimentally investigation which involves testing a total of nine reinforced concrete specimens under simultaneously cyclic lateral loading and varying axial load is carried out. The first series of six reinforced concrete column units were tested to obtain the variations in flexural hysteretic behaviour with fluctuation in axial load level. In the second phase of experimental investigation, three specimens were tested to study the shear strength of reinforced concrete columns subjected to cyclic lateral loading and varying axial load with emphasis placed on the study of degrading concrete shear resisting mechanisms and comparisons with the present design code equations for shear strength.
Following the experimental program, the mechanisms of shear resistance and the factors affecting the shear strength are considered. In particular, the effects of alternating tension and compression axial load on the shear resisting mechanisms are studied. On the basis of experimental results, proposals are made for predicting shear strength of reinforced concrete column of ductility and limited ductility.
Next, the theoretical work was undertaken to investigate the elastic and post-yield flexural rigidities of reinforced concrete sections. The equations for determining the elastic and post-yield flexural regidities are presented. Also, a moment-curvature hysteretic model including varying axial loading effect is proposed. The theoretical predictions for the moment-curvature hysteresis relationship were found to compare well with the experimental results.
Finally, an example is given of inelastic dynamic response analysis of reinforced concrete frame using the proposed moment-curvature model which includes the effects of varying axial load on the yield moment, and loading and unloading stiffness of the structural members.
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Murphy, Michael. "Performance based evaluation of prequalified steel seismic force resisting structures in Canada". Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43701.
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Structural Steel is one of the most important building materials used worldwide; special Seismic Force Resisting Systems (SFRS) have been developed to use steel to resist seismic forces in earthquake prone regions. In Canada, several steel SFRS have been adopted in the code, these include Moment Resisting Frames, Concentrically and Eccentrically Braced Frames, Buckling Restrained Braced Frames and Steel Plate Shear Walls; conventional construction frames may also be designed which have no seismic detailing. The design of these systems is covered comprehensively in literature; however no guidance has been provided regarding the selection of the best system for a project. In this thesis, the relative merits of each of the prequalified systems have been studied. A five story office building located in Vancouver, British Columbia, was redesigned nine times implementing each of the clauses for seismic design in CSA S16-09. The relative performance of each are compared using the Performance Based Earthquake Engineering (PBEE) method. PBEE accounts for the uncertainties in the seismic hazard, structural response and structural damage and their effect on the building performance during an earthquake. The relative merits of these systems were evaluated in terms of material usage and financial loss of the structure after a seismic event. The conclusion is that although the Moment Resisting Frame carries the lowest repair costs, it uses 20% more steel than the Eccentrically Braced Frame. The optimum systems in terms of material usage and repair costs were the Steel Plate Shear Wall (type ductile) and the Eccentric Braced Frame. The worst performing were the buildings designed with low ductility; both the conventional construction and limited ductility Concentrically Braced Frame structures performed poorly. Analysis shows that under the conditions of this thesis, most of the repair costs are related to the acceleration sensitive nonstructural components. Systems designed with higher ductility experienced lower accelerations and therefore lower costs. The PBEE methodology is an effective approach for evaluating different structures and comparing how they perform dynamically in an earthquake. Using PBEE, this thesis shows the advantages of frames designed in Canada for high ductility in economic terms.
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Stallbaumer, Cassandra. "Design comparison of hybrid masonry types for seismic lateral force resistance for low-rise buildings". Thesis, Kansas State University, 2016. http://hdl.handle.net/2097/32534.
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Master of ScienceArchitectural Engineering and Construction Science
Kimberly W. Kramer
The term hybrid masonry describes three variations of a lateral force resisting system that utilizes masonry panels inside steel framing to resist lateral loads from wind or earthquakes. The system originates from the rich history of masonry in the construction industry and is currently used in low-rise, low-seismic, wind-governed locations within the United States. Considerable research is focused on hybrid systems to prove their validity in high-seismic applications. The three variations of hybrid masonry are known by number. Type I hybrid masonry utilizes the masonry panel as a non-load-bearing masonry shear wall. Shear loads from the diaphragm are transferred into the beam, through metal plates, and over an air gap to the top of the masonry panel. The masonry panel transfers the shear to the beam below the panel using compression at the toe of the wall and tension through the reinforcement that is welded to the beam supporting the masonry. Steel framing in this system is designed to resist all gravity loads and effects from the shear wall. Type II hybrid masonry utilizes the masonry as a load-bearing masonry shear wall. The masonry wall, which is constructed from the ground up, supports the floor live loads and dead load of the wall, as well as the lateral seismic load. Shear is transferred from the diaphragm to the steel beam and into the attached masonry panel via shear studs. The masonry panel transfers the seismic load using compression at the toe and opposite corner of the panel. Type III hybrid masonry also utilizes the masonry panel as a load-bearing masonry shear wall, but the load transfer mechanisms are more complicated since the panel is attached to the surrounding steel framing on all four sides of the panel. This study created standard building designs for hybrid systems and a standard moment frame system with masonry infill in order to evaluate the validity of Type I and II hybrid masonry. The hybrid systems were compared to the standard of a moment frame system based on constructability, design, and economics.
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Bakr, Junied. "Displacement-based approach for seismic stability of retaining structures". Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/displacementbased-approach-for-seismic-stability-of-retaining-structures(fed35f6a-9a0d-46ae-8607-1dc434dc7c28).html.
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This thesis presents a unique finite element investigation of the seismic behaviour of 2 retaining wall types â a rigid retaining wall and a cantilever retaining wall. The commercial finite element program PLAXIS2D was used to develop the numerical simulation models. The research includes: (1) validating the finite element model with the results of 3 previously existing centrifuge tests taken from literature; (2) investigating the seismic response of rigid and cantilever retaining walls including studying the effects of contribution of wall displacement, wall and backfill seismic inertia and stiffness of the foundation soil; (3) developing analytical methods to concrete the findings of the numerical models. Based on the results of the seismic response of a rigid retaining wall, a unique relationship between the seismic earth pressure and wall displacement has been developed for the active and passive modes of failure. The seismic active earth pressure has been found to be not dependent on the wall displacement while the seismic passive earth pressure has been found to be highly affected by the wall displacement. The maximum seismic passive earth pressure force and relative horizontal displacement are predicted when the ground earthquake acceleration is applied with maximum amplitude and minimum frequency content. The seismic response of the wall was not affected by the ratio of the frequency content of the earthquake to the natural frequency of the wall-soil system. For the cantilever retaining wall detailed structural integrity and global analyses have been carried out. It has been observed that the seismic earth pressure, computed at the stem and along a vertical virtual plane are found to be out of phase with each other during the entire duration of the earthquake, and hence, the structural integrity and global stability should be evaluated and assessed individually. A critical case for the structural integrity is observed when the earthquake acceleration is applied towards the backfill soil and has frequency content close to the natural frequency of the retaining wall, while, for the global stability, the critical case is observed when the earthquake acceleration has maximum amplitude and is applied towards the backfill soil with minimum frequency content. The structural integrity is also found to be highly dependent on the ratio between the frequency content of earthquake acceleration to the natural frequency of the cantilever retaining wall. The relative horizontal displacement of a rigid and cantilever retaining wall is found to be highly affected by the duration of the earthquake in contrast to what has been observed for the seismic earth pressure force. The structural integrity of a rigid and cantilever retaining wall reduces when the backfill soil has a higher relative density, while the global stability increases when the backfill soil has a high relative density during an earthquake. The results obtained from the analytical methods reveal that the wall seismic inertia force has a significant effect on the structural integrity only for the top of the stem while the base of the stem does not get affected significantly. The modified Newmark sliding block method provided a more reasonable estimation of the relative horizontal displacement of a rigid retaining wall and a cantilever retaining wall compared with the classic Newmark sliding block method.
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Lowe, Joshua Brian. "Quantifying Seismic Risk for Portable Ground Support Equipment at Vandenberg Air Force Base". DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/269.
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This project develops a quantitative method to evaluate the seismic risk for portable GSE at Vandenberg Air Force Base. Using the latest probability data available from the USGS, risk thresholds are defined for portable GSE having the potential to cause a catastrophic event. Additionally, an example tool for design engineers was developed from the seismic codes showing the tipping hazard case can be simplified into strict geometrical terms. The misinterpretation and confusion regarding the Range Safety 24 Hour Rule exemption can be avoided by assessing seismic risk for portable GSE. By using the methods herein to quantify and understand seismic risk, more informed risk decisions can be made by engineering and management. The seismic codes and requirements used and referenced throughout include but are not limited to IBC, ASCE 7, EWR 127-1, and AFSPCMAN 91-710.
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Zahid, Muhammad. "Active earth pressure from c-Ø soil subjected to surcharge and seismic loadings". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2010. https://ro.ecu.edu.au/theses/1823.
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Construction of retaining structures to support soils at slopes steeper than their angle of repose has been a routine practice in most civil engineering projects. The successful design of such structures depends greatly on the calculation of total active force from the soil backfills, which has been a topic of research since the early development of analytical expressions presented by Coulomb (1776) and Rankine (1857). Mononobe-Okabe equation was developed during 1926-1929 for calculating total active earth pressure from cohesionless soil (f soil) backfills.
In recent past, attempts have been made to develop analytical expressions for the total seismic active force on retaining structures from the c-f soil backfills considering both horizontal and vertical seismic coefficients. However, an effort still requires presenting an analytical expression for a generalised case. Therefore, in this thesis, an attempt is made to extend the earlier expression (Shukla et al., 2009) for incorporating the effect of surcharge so that the newly developed expression can be used to estimate the total dynamic active force under both surcharge and seismic loading conditions.
The newly developed analytical expression results in several simplified expressions for static/dynamic cases, which have been presented by earlier researchers. A parametric study has been carried out to investigate the effect of surcharge and seismic loadings on the active earth pressure considering practical ranges of field parameters. It is observed that the total seismic active force increases linearly as the surcharge increases for any value of angle of shearing resistance and cohesion of the soil backfill; the rate of increase remains independent of the cohesion. As the horizontal seismic coefficient increases towards the wall, the total seismic active force increases nonlinearly, but it decreases with its increase towards the backfill for any value of shear strength parameters of the backfill. As the vertical seismic coefficient increases downwards, the total dynamic active force increases linearly, but it decreases for an upward increase. It is also noted that the critical value of the inclination to the horizontal of the failure plane decreases with an increase in surcharge. As the horizontal seismic coefficient increases towards the wall, the critical angle of inclination decreases nonlinearly, whereas it increases for an increase towards the backfill. Additionally, it has been noticed that the critical angleof inclination increases nonlinearly as the vertical seismic coefficient increases downwards, but it decreases with an increase in the upward direction.
Design charts have been presented for several possible cases. A numerical example is illustrated to explain the design steps so that practising engineers can design the retaining structures conveniently under surcharge and seismic loadings.
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Wearing, Christopher. "Evaluation of force distribution within a dual special moment-resisting and special concentric-brace frame system". Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/35483.
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Master of ScienceDepartment of Architectural Engineering and Construction Science
Kimberly W. Kramer
Dual Lateral Force Resisting Systems are currently required by code to include a Moment Resisting Frame capable of resisting at least 25% of the lateral loads. This thesis evaluates the seismic performance of a specific type of dual system: a Special Moment Resisting Frame-Special Concentric Brace Frame System (SMRF-SCBF) under three different force distributions. The three distributions were 80% - 20%, 75% - 25%, and 70% - 30% with the lesser force being allotted to the Special Moment Resisting Frame (SMRF) portion of the system. In order to evaluate the system, a parametric study was performed. The parametric study consisted of three SMRF-SCBF systems designed with different seismic force distributions. The aim of this study was to determine accuracy of the three different seismic force distributions. The accuracy was measured by comparing individual system models’ data and combined system models’ data. The data used for comparison included joint deflections (both horizontal and vertical), induced moments at moment connections, brace axial loads, column shears, and column base reactions. Two-dimensional models using the structural software RISA 3D were used to assist in designing the independent Seismic Force Resisting Systems. The designs of the frames were not finely tuned (smallest member size for strength), but were designed for drift (horizontal deflection) requirements and constructability issues. Connection designs were outside the scope of the study, except for constructability considerations – the SMRF and the SCBF did not have a common column; the frames were a bay apart connected with a link beam. The results indicated that a seismic force distribution of 75% to the SCBF and 25% to the SMRF most accurately predicts that frame’s behavior. A force distribution of 80% to the SCBF and 20% to the SMRF resulted in moderately accurate results as well. A vast opportunity for further research into this area of study exists. Alterations to the design process, consideration of wind loads, or additional force distributions are all recommended changes for further research into this topic.
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Kunwar, Sushil. "Comprehensive Evaluation of Composite Core Walls for Low-Seismic Force and Wind Load Applications". University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613750905724949.
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Zhang, Zhi y Zhi Zhang. "Analytical Investigation of Inertial Force-Limiting Floor Anchorage System for Seismic Resistant Building Structures". Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625385.
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This dissertation describes the analytical research as part of a comprehensive research program to develop a new floor anchorage system for seismic resistant design, termed the Inertial Force-limiting Floor Anchorage System (IFAS).
The IFAS intends to reduce damage in seismic resistant building structures by limiting the inertial force that develops in the building during earthquakes. The development of the IFAS is being conducted through a large research project involving both experimental and analytical research. This dissertation work focuses on analytical component of this research, which involves stand-alone computational simulation as well as analytical simulation in support of the experimental research (structural and shake table testing).
The analytical research covered in this dissertation includes four major parts:
(1) Examination of the fundamental dynamic behavior of structures possessing the IFAS (termed herein IFAS structures) by evaluation of simple two-degree of freedom systems (2DOF). The 2DOF system is based on a prototype structure, and simplified to represent only its fundamental mode response. Equations of motions are derived for the 2DOF system and used to find the optimum design space of the 2DOF system. The optimum design space is validated by transient analysis using earthquakes.
(2) Evaluation of the effectiveness of IFAS designs for different design parameters through earthquake simulations of two-dimensional (2D) nonlinear numerical models of an evaluation structure. The models are based on a IFAS prototype developed by a fellow researcher on the project at Lehigh University.
(3) Development and calibration of three-dimensional nonlinear numerical models of the shake table test specimen used in the experimental research. This model was used for predicting and designing the shake table testing program.
(4) Analytical parameter studies of the calibrated shake table test model. These studies include: relating the shake table test performance to the previous evaluation structure analytical response, performing extended parametric analyses, and investigating and explaining certain unexpected shake table test responses.
This dissertation describes the concept and scope of the analytical research, the analytical results, the conclusions, and suggests future work. The conclusions include analytical results that verify the IFAS effectiveness, show the potential of the IFAS in reducing building seismic demands, and provide an optimum design space of the IFAS.
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Taghikhany, Touraj. "Effect of variation of normal force on seismic performance of resilient sliding isolation systems". 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/145348.
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Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第11134号
工博第2413号
新制||工||1321(附属図書館)
22703
UT51-2004-R10
京都大学大学院工学研究科土木システム工学専攻
(主査)教授 家村 浩和, 教授 スコーソン チャールズ, 教授 鈴木 祥之
学位規則第4条第1項該当
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Dickof, Carla. "Clt infill panels in steel moment resisting frames as a hybrid seismic force resisting system". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44209.
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This paper examines CLT-steel hybrid systems at three, six, and nine storey heights to increase seismic force resistance compared to a plain wood system. CLT panels are used as infill in a steel moment frame combining the ductility of a steel moment frame system with a stiffness and light weight of CLT panels. This system allows for the combination of high strength and ductility of steel with high stiffness and light weight of timber. This thesis examines the seismic response of this type of hybrid seismic force resisting system (SFRS) in regions with moderate to high seismic hazard indices. A detailed non-linear model of a 2D infilled frame system and compared to the behavior of a similar plain steel frame at each height.
Parametric analysis was performed determining the effect of the panels and the connection configuration, steel frame design, and panel configuration in a multi-bay system. Static pushover loading was applied alongside semi-static cyclic loading to allow a basis of comparison to future experimental tests. Dynamic analysis using ten ground motions linearly scaled to the uniform hazard spectra for Vancouver, Canada with a return period of 2% in 50 years as, 10% in 50 years, and 50% in 50 years to examine the effect of infill panels on the interstorey drift of the three, six, and nine storey. The ultimate and yield strength and drift capacity are determined and used to determine the overstrength and ductility factors as described in the National Building Code of Canada 2010.
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Nippress, Stuart. "Subduction body force stresses, deformation and mantle seismic anisotropy at the 410 and 660km phase transitions". Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420748.
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Guo, Zifan. "Numerical Analysis of Passive Force on Skewed Bridge Abutments". BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/6151.
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Accounting for seismic forces and thermal expansion in bridge design requires an accurate passive force-deflection relationship for the abutment wall. Current design codes make no allowance for skew effects on passive force; however, large scale field tests indicate that there is a substantial reduction in peak passive force as skew angle increases. A reduction in passive force also reduces the transverse shear resistance on the abutment. The purpose of this study is to validate three-dimensional model using PLAXIS 3D, against large scale test results performed at Brigham Young University and to develop a set of calibrated finite element models. The model set could be used to evaluate the variation in passive resistance with skew angle for various abutment geometries and backfill types. Initially, the finite element model was calibrated using the results from a suite of field tests where the backfill material consisted of dense compacted sand. Results were available for skew angles of 0, 15, 30 and 45°. Numerical model results were compared with measured passive force-deflection curves, ground surface heave and displacement contours, longitudinal displacements, and failure plane geometry. Soil properties were defined by laboratory testing and in-situ direct shear tests on the compacted fill. Soil properties and mesh geometries were primarily calibrated based on the zero skew test results. The results were particularly sensitive to the soil friction angle, wall friction angle, angle of dilatancy, soil stiffness and lateral restraint of the abutment backwall movement. Reasonable agreement between measured and computed response was obtained in all cases confirming numerically that passive force decreases as skew angle increases Additional analyses were then performed for abutments with different soil boundaries.
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Hite, Monique C. "Evaluation of the Performance of Bridge Steel Pedestals under Low Seismic Loads". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14485.
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Many bridges are damaged by collisions from over-height vehicles resulting in significant impact to the transportation network. To reduce the likelihood of impact from over-height vehicles, steel pedestals have been used as a cost-effective, efficient means to increase bridge clearance heights. However, these steel pedestals installed on more than 50 bridges in Georgia have been designed with no consideration of seismic loads and may behave in a similar fashion to high-type steel bearings. Past earthquakes have revealed the susceptibility of high-type bearings to damage, resulting in the collapse of several bridges. Although Georgia is located in a low-to-moderate region of seismicity, earthquake design loads for steel pedestals should not be ignored. In this study, the potential vulnerabilities of steel pedestals having limited strength and deformation capacity and lack of adequate connection details for anchor bolts is assessed experimentally and analytically. Full-scale reversed cyclic quasi-static experimental tests are conducted on a 40' bridge specimen rehabilitated with 19" and 33" steel pedestals to determine the modes of deformation and mechanisms that can lead to modes of failure. The inelastic force-deformation hysteretic behavior of the steel pedestals obtained from experimental test results is used to calibrate an analytical bridge model developed in OpenSees. The analytical bridge model is idealized based on a multi-span continuous bridge in Georgia that has been rehabilitated with steel pedestals. The analytical bridge model is subjected to a suite of ground motions to evaluate the performance of the steel pedestals and the overall bridge system. Recommendations are made to the Georgia Department of Transportation (GDOT) for the design and construction of steel pedestals. The results of this research are useful for Georgia and other states in low-to-moderate seismic zones considering the use of steel pedestals to elevate bridges and therefore reduce the likelihood of over-height vehicle collisions.
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Curtis, Joshua Rex. "Effect of Inclined Loading on Passive Force-Deflection Curves and Skew Adjustment Factors". BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7255.
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Skewed bridges have exhibited poorer performance during lateral earthquake loading in comparison to non-skewed bridges (Apirakvorapinit et al. 2012; Elnashai et al. 2010). Results from numerical modeling by Shamsabadi et al. (2006), small-scale laboratory tests by Rollins and Jessee (2012), and several large-scale tests performed by Rollins et al. at Brigham Young University (Franke 2013; Marsh 2013; Palmer 2013; Smith 2014; Frederickson 2015) led to the proposal of a reduction curve used to determine a passive force skew reduction factor depending on abutment skew angle (Shamsabadi and Rollins 2014). In all previous tests, a uniform longitudinal load has been applied to the simulated bridge abutment. During seismic events, however, it is unlikely that bridge abutments would experience pure longitudinal loading. Rather, an inclined loading situation would be expected, causing rotation of the abutment backwall into the backfill. In this study, a large-scale test was performed where inclined loading was applied to a 30° skewed bridge abutment with sand backfill and compared to a baseline test with uniform loading and a non-skewed abutment. The impact of rotational force on the passive resistance of the backfill and the skew adjust factor was then evaluated. It was determined that inclined loading does not have a significant effect on the passive force skew reduction factor. However, the reduction factor was somewhat higher than predicted by the proposed reduction curve from Shamsabadi and Rollins 2014. This can be explained by a reduction in the effective skew angle caused by the friction between the side walls and the back wall. The inclined loading did not change the amount of movement required to mobilize passive resistance with ultimate passive force developing for displacements equal to 3 to 6% of the wall height. The rotation of the pile cap due to inclined loading produced higher earth pressure on the obtuse side of the skew wedge, as was expected.These findings largely resolve the concern that inclined loading situations during an earthquake may render the proposed passive force skew reduction curve invalid. We suggest that the proposed reduction curve remains accurate during inclined loading and should be implemented in current codes and practices to properly account for skew angle in bridge design.
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Shrestha, Santosh. "A COMPARATIVE STUDY OF EQUIVALENT LATERAL FORCE METHOD AND RESPONSE SPECTRUM ANALYSIS IN SEISMIC DESIGN OF STRUCTURAL FRAMES". OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2561.
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Equivalent Lateral Force Method (ELF) and Response Spectrum Analysis (RSA) are the two most popular methods of seismic design of structures. This study aims to present a comparative study of the two methods using hand-calculated approach as well as computer analysis according to ASCE 7-10 Standards. The two methods have been compared in terms of base shear and story forces by analyzing various models for different number of stories and different support conditions. It was found that ELF gives conservative results in comparison to RSA. This result was more obvious in case of four-story frames. Hence, for structures of increased elevation, the analysis from ELF may not be sufficient.
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Karakus, Hulya. "New Seismic Design Approaches For Block Type Quay Walls". Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608584/index.pdf.
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In this study, new design approaches are introduced for the seismic design of block type quay walls after reviewing the conventional methodologies. Within the development of the new design approaches an inverse triangular dynamic
pressures distributions are applied to define both seismic earth pressures and seismic surcharge pressures. Differently from the conventional design methodology, the hydrodynamic forces are taken into consideration while dynamic forces are specified and equivalent unit weight concept is used during
the both static and dynamic calculations Compatibility of this new design approaches are tested by case studies for the site and it is seen that the numerical results are in good agreement qualitatively with field measurements.
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Grusenmeyer, Eric. "Design comparison of ordinary concentric brace frames and special concentric brace frames for seismic lateral force resistance for low rise buildings". Kansas State University, 2012. http://hdl.handle.net/2097/14986.
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Master of ScienceDepartment of Architectural Engineering
Kimberly Waggle Kramer
Braced frames are a common seismic lateral force resisting system used in steel structures. Ordinary concentric braced frames (OCBFs) and special concentric braced frames (SCBFs) are two major types of frames. Brace layouts vary for both OCBFs and SCBFs. This report examines the inverted-V brace layout which is one common arrangement. OCBFs are designed to remain in the elastic range during the design extreme seismic event. As a result, OCBFs have relatively few special requirements for design. SCBFs are designed to enter the inelastic range during the design extreme seismic event while remaining elastic during minor earthquakes and in resisting wind loads. To achieve this, SCBFs must meet a variety of stringent design and detailing requirements to ensure robust seismic performance characterized by high levels of ductility. The design of steel seismic force resisting systems must comply with the requirements of the American Institute of Steel Construction’s (AISC) Seismic Provisions for Structural Steel Buildings. Seismic loads are determined in accordance with the American Society of Engineers Minimum Design Loads for Buildings and Other Structures. Seismic loads are very difficult to predict as is the behavior of structures during a large seismic event. However, a properly designed and detailed steel structure can safely withstand the effects of an earthquake. This report examines a two-story office building in a region of moderately high seismic activity. The building is designed using OCBFs and SCBFs. This report presents the designs of both systems including the calculation of loads, the design of frame members, and the design and detailing of the connections. The purpose of this report is to examine the differences in design and detailing for the two braced frame systems.
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GUPTA, ARUN KUMAR. "DETERMINATION OF SEISMIC PARAMETER OF RCC TALL BUILDING USING SHEAR CORE , SHEAR WALL AND SHEAR CORE WITH OUTRIGGER". Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18840.
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This report covers the detailed explanation about the determination of seismic parameter of
RCC tall building using shear core, shear wall and shear core with outrigger. Building are
subjected to various loads such as dead load, live load ,wind load and seismic load. Seismic
load has extreme adverse effect on building so it is necessary to perform seismic analysis This
paper describe about the response of building when it is subjected to seismic load , this
response can be shown by story drift and base shear. Seismic analysis has been performed on
(G+30) building which is located in zone 4 using ETABS software. Analysis has been
performed according to IS 1893 PART 1 (2016). This paper gives total rule to manual as wells
programming examination of seismic coefficient technique.
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Smith, Kyle Mark. "Passive Force on Skewed Bridge Abutments with Reinforced Concrete Wingwalls Based on Large-Scale Tests". BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5577.
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Skewed bridges have exhibited poorer performance during lateral earthquake loading when compared to non-skewed bridges (Apirakvorapinit et al. 2012; Elnashai et al. 2010). Results from small-scale laboratory tests by Rollins and Jessee (2012) and numerical modeling by Shamsabadi et al. (2006) suggest that skewed bridge abutments may provide only 35% of the non-skewed peak passive resistance when a bridge is skewed 45°. This reduction in peak passive force is of particular importance as 40% of the 600,000 bridges in the United States are skewed (Nichols 2012). Passive force-deflection results based on large-scale testing for this study largely confirm the significant reduction in peak passive resistance for abutments with longitudinal reinforced concrete wingwalls. Large-scale lateral load tests were performed on a non-skewed and 45° skewed abutment with densely compacted sand backfill. The 45° skewed abutment experienced a 54% reduction in peak passive resistance compared to the non-skewed abutment. The peak passive force for the 45° skewed abutment was estimated to occur at 5.0% of the backwall height compared to 2.2% of the backwall height for the non-skewed abutment. The 45° skewed abutment displayed evidence of rotation, primarily pushing the obtuse side of the abutment into the backfill, significantly more than the non-skewed abutment as it was loaded into the backfill. The structural and geotechnical response of the wingwalls was also monitored during large-scale testing. The wingwall on the obtuse side of the 45° skewed abutment experienced nearly 6 times the amount of horizontal soil pressure and 7 times the amount of bending moment compared to the non-skewed abutment. Pressure and bending moment distributions are provided along the height of the wingwall and indicate that the maximum moment occurs approximately 20 in (50.8 cm) below the top of the wingwall. A comparison of passive force per unit width suggests that MSE wall abutments provide 60% more passive resistance per unit width compared to reinforced concrete wingwall and unconfined abutment geometries at zero skew. These findings suggest that changes should be made to current codes and practices to properly account for skew angle in bridge design.
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Quezada, Eder, Yaneth Serrano y Guillermo Huaco. "Dynamic Amplification Factor Proposal for Seismic Resistant Design of Tall Buildings with Rigid Core Structural System". Smart Innovation, Systems and Technologies, 2021. http://hdl.handle.net/10757/653773.
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El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.Currently, there is an increase in the demand for tall buildings in the city of Lima. This research proposes to reduce the dynamic amplification factor through the seismic design of tall buildings based on the requirements of Peruvian code considering that they are regular in plan and height. Minimum base shear values according to the comparison of static seismic shear and dynamic shear from the spectral modal analysis were reviewed for cases of buildings larger than 120 m. The study of 28 reinforced concrete buildings was proposed, with different heights - varying from 24 to 36 floors, with different floor configurations, as well as the arrangement of the walls considering as a rigid core structural system. Additionally, the characteristics of the materials, the loads and combinations were defined. The responses of these buildings were determined by the response spectrum analysis (RSA) and then compared with those obtained by the lineal response history analysis (LRHA), for the last analysis, five Peruvian seismic records were used and scaled to 0.45 g. The seismic responses of the LRHA procedure were taken as a benchmark. The result of this study is the analysis and proposal of the C/R factor for high-rise buildings, as well as obtaining the base shear and drift verification. Minimum base shear values can be reduced for high or long-term buildings, being regular in plan and height.
Revisión por pares
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Fredrickson, Amy. "Large-Scale Testing of Passive Force Behavior for Skewed Bridge Abutments with Gravel and Geosynthetic Reinforced Soil (GRS) Backfills". BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5513.
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Correct understanding of passive force behavior is particularly key to lateral evaluations of bridges because plastic deformation of soil backfill is vital to dissipation of earthquake energy and thermally-induced stresses in abutments. Only recently have studies investigated the effects of skew on passive force. Numerical modeling and a handful of skewed abutment tests performed in sand backfill have found reduced passive force with increasing skew, but previous to this study no skewed tests had been performed in gravel or Geosynthetic Reinforced Soil (GRS) backfills. The goal of this study was to better understand passive force behavior in non-skewed and skewed abutments with gravel and GRS backfills. Prior to this study, passive pressures in a GRS integrated approach had not been investigated. Gravel backfills also lack extensive passive force tests.Large-scale testing was performed with non-skewed and 30° skewed abutment configurations. Two tests were performed at each skew angle, one with unconfined gravel backfill and one with GRS backfill, for a total of four tests. The test abutment backwall was 11 ft (3.35 m) wide, non-skewed, and 5.5 ft (1.68 m) high and loaded laterally into the backfill. However, due to actuator loading constraints, all tests except the non-skewed unconfined gravel test were performed to a backfill height of 3.5 ft (1.07 m). The passive force results for the unconfined gravel test was scaled to a 3.5 ft (1.07 m) height for comparison.Test results in both sets of backfills confirmed previous findings that there is significant reduction in passive force with skewed abutment configurations. The reduction factor was 0.58 for the gravel backfill and 0.63 for the GRS backfill, compared to the predicted reduction factor of 0.53 for a 30° skew. These results are within the scatter of previous skewed testing, but could indicate that slightly higher reduction factors may be applicable for gravel backfills. Both backfills exhibited greater passive strength than sand backfills due to increased internal friction angle and unit weight. The GRS backfill had reduced initial stiffness and only reached 79% to 87% of the passive force developed by the unreinforced gravel backfill. This reduction was considered to be a result of reduced interface friction due to the geotextile. Additionally, the GRS behaved more linearly than unreinforced soil. This backfill elasticity is favorable in the GRS-Integrated Bridge System (GRS-IBS) abutment configuration because it allows thermal movement without developing excessive induced stresses in the bridge superstructure.
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Castillo, Melgarejo Felix Alberto y Delgado Orlando Junior Gonzales. "Verificación estructural del edificio Floresty usando elementos finitos embebidos". Bachelor's thesis, Universidad Ricardo Palma, 2015. http://cybertesis.urp.edu.pe/handle/urp/1243.
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El Perú es un país sísmico debido que se encuentra cerca de una zona de Subducción donde la Placa de Nazca se mueve por debajo de la Placa Continental. En las llamadas zonas de subducción la placa acumula gran cantidad de energía al introducirse debajo de la otra, estas placas avanzan en sentido contrario comprimiéndose hasta llegar a un punto de ruptura de grandes volúmenes de roca generando sismos de gran magnitud.
En Lima se han producido fuertes sismos según los registros que se tienen de la época siendo el más fuerte en el año de 1746 donde hubo mucha destrucción y muchas personas murieron.
En el Perú se han desarrollado las normas E.060 Concreto armado y la E.030 Diseño Sismorresistente dentro del Reglamento Nacional de Edificaciones, estas normas son muy importantes para el diseño y buen comportamiento de las edificaciones. Las cuales se soportan en la cimentación, siendo ésta la encargada de transmitir las cargas al suelo distribuyéndolas de manera que no supere la presión admisible.
El área de estudio que se va a analizar se encuentra ubicado en el distrito de Surquillo de la provincia y departamento de Lima, donde se está ejecutando el edificio multifamiliar “Floresty”, del cual nos interesa su cimentación y los muros para su análisis. El análisis se llevará a cabo con el programa VisualFEA. Este programa nos arrojará diferentes resultados a pesar de haber sido considerado el acero como elemento embebido. La aplicación del programa para obtener diferentes resultados es el fin de la presente tesina.
Peru is a seismic country because it is near to a subduction zone where the Nazca Plate moves under the Continental Plate. In the denominated subduction zones, the plate accumulates a great amount of energy in getting into the other plate. These plates move forward to the contrary sense compressing themselves up to come to a break point of large volumes of rock generating earthquakes of great magnitude.
In Lima, strong earthquakes have occurred according to records kept until now, and the most significant was that of 1746 where there were a lot of destruction and where many people died.
In Peru, Reinforced Concrete E.060 and Earthquake Resistant Design E.030 Standards have developed in the National Construction Regulations. These standards are very important for designing and good building performance, which supports to the foundations, which is in charge of transferring the loads to the ground spreading these one so that it does not exceed allowable pressure.
E.060 standard contains minimal values, which shall fulfill for structure performance with ACI momentum coefficient method. However, it is possible design with finite-element method using VisualFEA software and the results are obtained with this software shall fulfill the standard.
The study area to analyze is within San Miguel District, Province and Department of Lima, where a multifamily apartment block is constructed, and we are interested in analyzing its foundation because it shows already a design given by projector; this design comes to be a pad foundation or foundation slab. It is from this item where we are going to start to proof it fulfills with ACI momentum coefficient method according to Peruvian Standard and it shapes with finite-element method through VisualFEA software whose results shall also fulfill.
In this sense, the main objective would be comparison and demonstration of analysis results of building F’s foundation slab using finite-element method through VisualFEA software; these results shall fulfill the Construction E.60 Peruvian standard with the ACI momentum coefficients method.
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O'Brien, Patrick Emmet. "Characterizing the Load-Deformation Behavior of Steel Deck Diaphragms using Past Test Data". Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78679.
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Recent research has identified that current code level seismic demands used for diaphragm design are considerably lower than demands in real structures during a seismic event. However, historical data has shown that steel deck diaphragms, common to steel framed buildings, perform exceptionally well during earthquake events. A new alternative diaphragm design procedure in ASCE 7-16 increases diaphragm seismic demand to better represent expected demands. The resulting elastic design forces from this method are reduced by a diaphragm design force reduction factor, Rs, to account for the ductility of the diaphragm system. Currently, there exist no provisions for Rs factors for steel deck diaphragms. This research was therefore initiated to understand inelastic steel deck diaphragm behavior and calculate Rs factors.
A review of the literature showed that a large number of experimental programs have been performed to obtain the in-plane load-deformation behavior of steel deck diaphragms. To unify review of these diaphragm tests and their relevant results, a database of over 750 tested specimens was created. A subset of 108 specimens with post-peak, inelastic behavior was identified for the characterization of diaphragm behavior and ductility. A new recommended method for predicting shear strength and stiffness for steel deck diaphragms with structural concrete fill is proposed along with an appropriate resistance factor. Diaphragm system level ductility and overstrength are estimated based on subassemblage test results and Rs factors are then calculated based on these parameters. The effects of certain variables such as deck thickness and fastener spacing on diaphragm ductility are explored.Master of Science
30
Quezada, Ramos Eder Nel, Arone Yaneth Serrano y Guillermo Huaco. "A comparative study of the seismic base shear force and story drift ratios using Time History and Modal Spectrum Analysis according to Peru Code E.030 and ASCE 7.16 on high-rise buildings". Institute of Electrical and Electronics Engineers Inc, 2020. http://hdl.handle.net/10757/656418.
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El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.Since the last decade there is an important increase of high-rise buildings in Peru, especially in urban areas. Therefore, it is necessary to assess if the Peruvian Seismic Code is applicable for this type of buildings which have long natural periods as their main characteristic. The main objective of this article is to compare the results of the base shear and story drift ratios of Peruvian seismic design code E.030 with those of the ASCE 7-16 standard to the case of high-rise buildings, this due to the fact that there is limited information for tall buildings in Peru or comparison between national or international code for this type of structures. These high rise buildings have square and rectangular plan floors. Half of them have moment frames and reinforce concrete slab around the rigid core and the others have post-tensioned slab as their vertical load resisting system and central core walls with peripheral columns as the lateral force resisting system. Hence, the response spectrum analysis (RSA) is carried out for every case of the four tall buildings with different configurations using both seismic codes. Then results are compared with the linear response history analysis (LRHA) considering five Peruvian ground motions records, which were scaled to 0.45g PGA. It was verified that generally both the base shear and the interstory drifts calculated using ASCE7-16 are less than that obtained with the seismic code E.030.
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Johnson, Curtis Mathias. "A comparison of Reduced Beam Section moment connection and Kaiser Bolted Bracket® moment connections in steel Special Moment Frames". Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/36233.
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Master of ScienceDepartment of Architectural Engineering and Construction Science
Kimberly W. Kramer
Of seismic steel lateral force resisting systems in practice today, the Moment Frame has most diverse connection types. Special Moment frames resist lateral loads through energy dissipation of the inelastic deformation of the beam members. The 1994 Northridge earthquake proved that the standard for welded beam-column connections were not sufficient to prevent damage to the connection or failure of the connection. Through numerous studies, new methods and standards for Special Moment Frame connections are presented in the Seismic Design Manual 2nd Edition to promote energy dissipation away from the beam-column connection. A common type of SMF is the Reduce Beams Section (RBS). To encourage inelastic deformation away from the beam-column connection, the beam flange’s dimensions are reduced a distance away from the beam-column connection; making the member “weaker” at that specific location dictating where the plastic hinging will occur during a seismic event. The reduction is usually taken in a semi-circular pattern. Another type of SMF connection is the Kaiser Bolted Bracket® (KBB) which consists of brackets that stiffen the beam-column connection. KBB connections are similar to RBS connections as the stiffness is higher near the connection and lower away from the connection. Instead of reducing the beam’s sectional properties, KBB uses a bracket to stiffen the connection. The building used in this parametric study is a 4-story office building. This thesis reports the results of the parametric study by comparing two SMF connections: Reduced Beam Section and Kaiser Bolted Brackets. This parametric study includes results from three Seismic Design Categories; B, C, and D, and the use of two different foundation connections; fixed and pinned. The purpose of this parametric study is to compare member sizes, member forces, and story drift. The results of Seismic Design Category D are discussed in depth in this thesis, while the results of Seismic Design Category B and C are provided in the Appendices.
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Just, Paul J. III. "A State of the Art Review of Special Plate Shear Walls". University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1459155417.
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Yzema, Fritz Alemagne. "États limites ultimes de cadres en acier isolés sismiquement avec des amortisseurs élastomères et des contreventements en chevrons". Mémoire, Université de Sherbrooke, 2014. http://savoirs.usherbrooke.ca/handle/11143/5347.
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Résumé : Ce projet de maîtrise s’intéresse au comportement ultime d’une structure en acier, contrôlée sismiquement par des amortisseurs élastomères et des contreventements en chevron. Les séismes peuvent causer des dommages considérables quand les infrastructures et les bâtiments ne sont pas construits selon les normes et les techniques appropriées. Par conséquent, réduire l’impact des séismes revient particulièrement à construire des ouvrages sécuritaires en tenant compte bien entendu du paramètre économique. Ainsi Gauron, Girard, Paultre et Proulx ont étudié en 2009, un système de reprise de forces latérales, constitué uniquement de treventements en chevron montés en série avec des amortisseurs en caoutchouc naturel fibré ayant de nombreux avantages. Premièrement, le système reste élastique sous le séisme de design en réduisant les efforts sismiques linéaires par un facteur supérieur à R[indice inférieur d] = 3 par rapport à un cadre conventionnel. Deuxièmement, il est capable de contrôler les déplacements sous la limite du CNBC 2010 (Code National du Bâtiment du Canada 2010), et même de réduire ces derniers dans certains cas. Par conséquent, il permet de réduire les sections des poutres et des poteaux des cadres par rapport à une structure conventionnelle ainsi que les coûts de réparation après un séisme. Toutefois, le comportement à l’état limite ultime d’un tel système, ses limites et ses réserves de sécurité restaient à déterminer. Ainsi, l’objectif global de ce projet de recherche est de déterminer les différents mécanismes de ruine possibles de ce système, d’établir des limites et réserves de sécurité, et de préciser, après avoir formulé certaines recommandations, à quelles conditions il peut être utilisé dans le dimensionnement de nouvelles structures. Pour atteindre les objectifs fixés, deux essais quasi statiques ont été réalisés sur deux cadres en acier dimensionnés avec le système. Des essais dynamiques ont aussi été réalisés afin d’avoir les propriétés viscoélastiques des amortisseurs. Le premier essai a mis en évidence un mécanisme de ruine inattendu et prématuré qui a souligné un défaut majeur dans les connexions des diagonales avec l’amortisseur. Le second essai a révélé un des mécanismes de ruine envisagés initialement où le caoutchouc se déchire après l’initiation du flambement dans la diagonale comprimée. Les résultats expérimentaux ont montré que l’amortisseur constitue le maillon faible du système, et que des efforts parasites peuvent réduire significativement la capacité portante des structures dimensionnées avec un tel système. Dans les deux cas, les résultats ont montré que la méthode de dimensionnement du système tel qu’elle est définie actuellement mérite d’être améliorée. En ce sens, des recommandations relatives au dimensionnement des différents éléments des structures dimensionnées avec le système ont été élaborées, particulièrement en ce qui concerne le caoutchouc et les connexions. // Abstract : This thesis focuses on the ultimate behavior of steel structures, controlled seismically by elastomeric dampers and chevron bracings. Earthquakes can cause considerable damages when infrastructures and buildings are not built considering appropriate standards and technics. Therefore, mitigating the impact of earthquakes means essentially building safe structures by taking account of economic parameters too. Thus Gauron, Girard, Paultre and Proulx studied in 2009 a seismic force resisting system consisting only of chevron braces connected in series with fiber-reinforced natural rubber dampers that offers many benefits. First, the system remains elastic under the design earthquake by reducing linear seismic efforts by a factor of R[subscript d] = 3 compared to a conventional frame. Secondly, it allows to control the displacements under the limits of NBCC 2010 (National Building Code of Canada 2010), and even to reduce them in some cases. Therefore, it allows a reduction of sections of beams and columns of conventional frames and it prevents repairing costs of the structure after an earthquake. However, the ultimate limit state behavior of this system, its limitations and safety reserves have not been determined yet. Thus, the overall objective of this project is to determine the different possible failure mechanisms of the system, to set its limits and safety reserves, and to state after some recommendations, how it can be used in the design of new structures. To achieve these objectives, two quasi static tests were performed on two steel frames designed with the new system. Dynamic tests were also conducted to get the viscoelastic properties of the damping material. The first quasi static test revealed an unexpected and premature failure mechanism that pointed out a major flaw in the connections of the braces with the damper. The second test revealed one of the failure mechanisms originally expected where the rubber tears after buckling of the compression brace. The experimental results have shown that the damper is the weak element in the system, and that additional forces can significantly reduce the structural capacity of structures designed with the system. In both cases, the results have shown that the actual design method of the system should be improved. Thus, recommendations for the design of elements of structures designed with this system have been developed, particularly with regard to the rubber and brace connections.
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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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Gardiner, Debra Rachel. "Design Recommendations and Methods for Reinforced Concrete Floor Diaphragms Subjected to Seismic Forces". Thesis, University of Canterbury. Department of Civil and Natural Resources Engineering, 2011. http://hdl.handle.net/10092/6993.
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The magnitudes of seismic forces which develop in floor diaphragms were investigated in this report to enable the development of a desktop floor diaphragm force design method for use in a structural design office. The general distributions of the forces which develop within the floor diaphragm were also investigated.
Two and three dimensional, non-linear numerical integration time history analyses were performed to determine the trends and estimates of inertial and self-strain compatibility transfer forces within floor diaphragms. Sensitivity studies were carried out to determine which simplifying analytical modelling assumptions could be made in the analytical models. It was found that foundation flexibility, shear deformations in walls and the type of plastic hinge model, all affected the magnitudes of forces within floor diaphragms. A range of buildings with different stiffness, strength, height, types of lateral force resisting systems and different locations of the building including different seismic zones and soil types were modelled with the time history analyses method.
The results indicated that the magnitudes of inertial forces were primarily related to higher dynamic modes of the structure and the transfer forces were related to the lower modes of vibration of the structure. It was identified that the maximum magnitudes of inertial and transfer forces do not occur simultaneously. The results also indicated that larger inertial and transfer forces, than those predicted by the Equivalent Static Analysis method, developed in the lower levels of the buildings. From these results a static force floor diaphragm design method was developed. Comparisons were made between both the inertial and transfer floor diaphragm forces obtained from the proposed static method, to values from time history analyses. These comparisons indicated that the floor forces obtained by the proposed method were generally larger than the floor forces obtained by the time history results.
Elastic and inelastic finite element analyses were used to estimate the in-plane distributions of floor diaphragm forces for floor diaphragms with different geometries and lateral force resisting elements. Comparisons were made between the total tension forces obtained from the finite element analyses and Strut and Tie Analysis methods; these comparisons indicated the relative levels of redistribution of internal forces which could induce cracking within the floor. The comparisons indicated that redistribution cracking in the floors could develop around corner columns, re-entrant corners and openings.
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Chiewanichakorn, Methee. "Stability of thin precast concrete wall panels subjected to gravity and seismic forces". Thesis, University of Canterbury. Civil Engineering, 1999. http://hdl.handle.net/10092/10450.
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The stability of thin reinforced concrete cantilever walls with lateral displacement restraint at roof level designed for limited ductility under gravity and in-plane seismic loading is investigated in this project. A large number of innovative designs of very tall and slender reinforced concrete walls have been developed in New Zealand ahead of the design standard in the past five years. In order to understand the actual wall behaviour and obtain the quantitative design verifications, limited experimental work has been performed for the past few years at the University of Canterbury. The test results of the previous experimental work are reviewed.
Four slender precast concrete 1:2.5 scale walls were tested up to failure under reversed cyclic loading regime with increased displacement level. The walls were 3.75 m high, 1m long and 50 mm thick. The aspect and slenderness ratios were 3.75 and 75, respectively. The two main variables investigated were in effect the eccentric axial load ratios and the ratio between the lap splice length of the starter bars and the height to the point of inflection.
Only one of the test units, which had longer lap-splice and imposed eccentric vertical load, was susceptible to lateral buckling failure due to a significant cracking in the lower half of the wall and the excessive out-of-plane displacement. The units with an artificial lap-splice (welded connection) performed well and failed due to loss of strength caused by fracturing of starter bars after being buckled under the effects of reversed cyclic loading. Failure was observed near the welds along an artificial lap splice. Twisting of the walls at the base of the walls was observed in the tests.
A continuum method for the seismic design and assessment of thin precast concrete walls is proposed. The method can be applied to walls of structures designed for the range of elastic to limited ductility response.
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Dekker, Nicholas M. "Dynamic Analysis and Seismic Retrofit of the Point Sur Lighthouse". DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2192.
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The Point Sur Lighthouse is an unreinforced stone masonry building completed in 1889 on the central coast of California. The lighthouse is listed on the National Register of Historic Places and is still an active aid to navigation. The original first-order Fresnel lens was removed from the lantern room and placed in safekeeping due to its high risk of damage in the event of a strong earthquake. The lens has been approved to return to its original setting but the seismic performance of the building must first be assessed in order to ensure the safety of the lens and lighthouse, specifically the out-of-plane behavior of the unreinforced masonry walls, the implementation of possible seismic retrofit schemes, and the effects of the lens’s added weight.
This research focuses on the dynamic behavior of the lighthouse in its current state and the changes in the dynamic behavior each of the proposed seismic retrofit schemes might cause. For the purposes of this research, dynamic behavior is considered as natural frequencies, mode shapes, and related structural properties. The dynamic behavior of the lighthouse was assessed using two main methods: forced vibration testing and finite element computer modeling. Forced vibration testing is a nondestructive testing method that can be used to directly characterize dynamic behavior of a structure, and finite element computer modeling is useful for the design and simulation of dynamic behavior of both new and existing structures. The combination of these two methods on the Point Sur Lighthouse will work to develop and prove state-of-the-art seismic retrofitting techniques.
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Harrison, Stella y Siri Nöjd. "Influence of Foundation Modelling on the Seismic Response of a Concrete Dam". Thesis, KTH, Betongbyggnad, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300448.
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It is of great importance to ensure the structural safety of dams during earthquakes since a failure may cause catastrophic consequences. Conventional computation of the structural response of dams is based on a simplified approach where the foundation is considered as massless. However, recent developments have produced several new analysis methods that consider the foundation mass, modelled with absorbing boundaries and free-field forces. These newer methods are intended to simulate the seismic structural response more accurately, optimize the design and minimise future unnecessary reparations. The aim of the thesis was to investigate the influence of foundation modelling in seismic time history analyses. This was done by comparing the established massless foundation approach to two approaches with foundation mass and free-field forces included; the analytical approach presented by Song et al. (2018) and the direct FE approach by Løkke (2018). Both the efficiency of the seismic wave propagation simulation and the structural response of the dam were of interest, and points on the dam and foundation were studied to accurately compare these modelling approaches. The time history analyses showed that the massless approach corresponded perfectly with the ideal theoretical velocity at the foundation surface when studying only the foundation block, as expected. The analytical and direct FE however, differed slightly from the theoretical value but still gave an accurate representation. Both methods using free-field forces obtained equivalent and realistic structural responses when studying the dam-reservoir-foundation model. The massless method however,strongly overestimated the dam response and was therefore found to not capture the actual behavior of the dam accurately, despite modifications such as increased material damping in the concrete. Additionally, another aim was to analyse the influence of modelling in 2D versus 3D for determining the dynamic characteristics of the dam such as natural frequencies and eigenmodes of the dam. These frequency analyses were made using models with and without foundation mass considered and was compared to experimental data.The massless 3D model was found to be the most effective modelling approach for deriving the dynamic characteristics of the dam since the use of a 3D model was necessary in order to study the behaviour of the whole dam and post-processing was simpler when using the massless model.Det är nödvändigt att säkerställa dammars säkerhet mot jordbävningar i design-processen eftersom ett dammbrott kan få katastrofala konsekvenser. Traditionellt används förenklade beräkningar där dammens strukturella respons beräknas med en berggrund där bergets massa är försummad. Den senaste tiden har flera nya analysmetoder tagits fram, som tar hänsyn till bergets massa och är modellerade med absorberande randvillkor och free-field forces. De nyare metoderna förväntas modellera de seismiska krafterna mer exakt för att optimera designen och minimera onödiga reparationer. Syftet med projektet var att undersöka inverkan från olika metoders sätt att beakta berggrunden vid seismiska analyser. Det utfördes genom att jämföra den etablerade masslösa metoden med två metoder som beaktar bergmassan och free-fieldforces; den analytiska metoden av Song et al. (2018) och Direct FE-metoden av Løkke (2018). Både effektiviteten i den seismiska vågutbredningssimuleringen och dammens strukturella respons var av intresse. Modelleringsmetoderna jämfördes genom att studera punkter på både dammen och berget. När enbart berggrunden studerades med den masslösa metoden så erhölls, som förväntat, god överenstämmelse med den ideala teoretiska hastigheten på bergsytan. De analytiska och Direct FE metoderna skiljde sig marginellt från det teoretiska värdet men gav fortfarande en korrekt hastighet på bergsytan. Vid analys av modeller med dam och reservoar inkluderade, gav metoderna som använde free-field forces ekvivalenta och realistiska strukturella responser. Den masslösa metoden däremot, överskattade kraftigt dammens respons och ansågs därför inte modelleradet verkliga beteendet hos dammen på ett korrekt sätt, trots modifieringar med ökad materialdämpning i betongen. Ett annat syfte var att analysera påverkan av modellering i 2D kontra 3D för att bestämma dammens dynamiska egenskaper, som egenfrekvenser och egenmoder. Dessa frekvensanalyser gjordes med hjälp av modeller som både beaktade och försummade bergets massa, och jämfördes med experimentella data. Den masslösa 3D-modellen visade sig vara den mest effektiva modelleringsmetoden för att erhållade dynamiska egenskaperna hos dammen. Det eftersom en 3D-modell var nödvändig för att studera hela dammens beteende och hantering av utdata var förenklad vid användning av den masslösa modellen.
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Mikhaltsevitch, Vassili Timofeevitch. "Investigations of Elastic Properties of Isotropic and Anisotropic Rocks at Seismic Frequencies Using Forced-Oscillation Experiments". Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/59144.
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The thesis developed and validated an experimental forced-oscillation approach for low-frequency laboratory investigations of the elastic and anelastic properties of the main sedimentary rocks such as sandstones, carbonates and shales. The presented results demonstrate that the forced-oscillation approach is able to adequately quantify elastic and anelastic parameters of sedimentary rocks and can improve the efficiency of the seismic data interpretation and reservoir characterisation.
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葛, 漢彬, Hanbin GE, 豪. 河野, Takeshi KONO, 勉. 宇佐美 y Tsutomu USAMI. "圧縮と曲げを受ける鋼部材セグメントの終局ひずみと鋼アーチ橋の動的耐震照査への応用". 土木学会, 2004. http://hdl.handle.net/2237/8545.
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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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Gao, Guochao. "Contribution to seismic modeling and imaging in the presence of reflector roughness". Thesis, Ecole centrale de Marseille, 2020. http://www.theses.fr/2020ECDM0010.
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En raison de divers processus géologiques et de mouvements crustaux, les interfaces rugueuses existent largement dans la Terre. Une interface rugueuse peut affecter fortement la propagation des ondes sismiques par des changements d'amplitude, de phase, d'angle de diffusion, du contenu en fréquence et même de conversion de type d'onde. Inévitablement, la qualité de l'imagerie sismique ou de l'inversion en est fortement influencée. Malgré les nombreux travaux consacrés à l'interaction des ondes avec des interfaces rugueuses, cette interaction est loin d’être comprise, car il est encore difficile de modéliser la propagation des ondes sismiques dans un tel contexte et par conséquent de reconstruire correctement le sous-sol. Cette thèse étudie l'effet des interfaces rugueuses sur la modélisation et l'imagerie des ondes sismiques et explore le potentiel d'une méthode électromagnétique pour s’affranchir de cet effet et ainsi mieux imager le sous-sol.Nous utilisons une méthode numérique basée sur les éléments finis spectraux, et plus précisément le code SPECFEM2D, qui permet de modéliser la propagation des ondes acoustiques dans le domaine temporel. Tout d'abord, nous considérons un réseau sinusoïdal et illustrons numériquement les conséquences de l'équation de réseau sur les signaux temporels. Ensuite, en utilisant l'analyse f-k, nous montrons le positionnement des différents ordres de diffraction dans le domaine fréquence-nombre d'onde. Après une analyse de sensibilité, nous sélectionnons une configuration appropriée qui permet la séparation des ordres de diffraction à partir d’un shot gather. Enfin, il est montré que la hauteur de rugosité et la longueur de corrélation influencent manifestement l'apparence du champ d'onde diffracté. Cependant, la longueur de corrélation a moins d'effet sur l'énergie des ondes diffractées que la rugosité d'interface.Nous utilisons un schéma d'inversion de forme d'onde complète (FWI) basé sur le logiciel DENISE afin d’étudier l'influence de la hauteur de rugosité et de la longueur de corrélation sur les résultats d'imagerie sismique. Lorsque la hauteur de rugosité augmente jusqu'à atteindre la longueur d'onde dominante ou plus, le bruit aléatoire domine dans les données sismiques, et les résultats FWI se détériorent considérablement, en particulier pour la reconstruction d'un réflecteur horizontal situé sous l'interface rugueuse. En revanche, la longueur de corrélation a un effet beaucoup plus faible sur le bruit aléatoire et la qualité des résultats inversés.Comme démontré dans ce travail, la rugosité de l'interface a un impact majeur sur la propagation et l'imagerie des ondes sismiques. Lorsqu'une interface rugueuse est présente dans le sous-sol, son effet doit être examiné de manière critique dans le cadre de la FWI, afin de reconstruire correctement les réflecteurs éventuellement situés en dessous, puis d'interpréter correctement les images du sous-sol. Dans ce contexte, nous effectuons des tests préliminaires sur l'utilisation d'une méthode d'extinction sélective visant à enlever l'impact de la rugosité sur les champs d'ondes. Les résultats sont prometteurs et montrent le potentiel de la méthode pour une meilleure imagerie. De plus, l'écart type de l'amplitude des données traitées semble pouvoir être utilisé pour évaluer les caractéristiques de l'interface rugueuse, ce qui présenterait également un intérêt important pour les géophysiciens et les géologuesDue to various geological processes and crustal movements, rough interfaces widely exist within the Earth. The rough interface can strongly affect seismic wave propagation, manifested as changes in the amplitude, phase, scattering angle, frequency content, and even the wave-type conversion. Inevitably, the quality of seismic imaging or inversion is also greatly influenced. Despite the numerous works devoted to the interaction of waves with rough interfaces, this interaction remains to be better understood, as it is still quite challenging to model the seismic wave propagation and to properly reconstruct the subsurface. The thesis investigates the effect of rough interfaces on seismic wave modeling and imaging, and explores the potential of an electromagnetic method to remove this effect and to better image the subsurface.We use a spectral-element method, and more specifically the code SPECFEM2D, for modeling acoustic wave propagation in the time domain. First, we consider a sinusoidal grating and illustrate numerically the consequences of the grating equation on the temporal signals. Then, using f-k analysis, we show the location of the different diffraction orders in the frequency-wavenumber domain. After a sensitivity analysis, we select an appropriate configuration that allows for the separation of diffraction orders from a shot gather. Last, both roughness height and correlation length are shown to obviously influence the appearance of the diffracted wavefield. However, the correlation length has less effect on the energy of the diffracted waves than the interface roughness.We adopt a full-waveform inversion (FWI) scheme based on the software package DENISE to study the influence of different roughness heights and correlation lengths on seismic imaging results. When the roughness height increases up to the dominant wavelength or is greater, the random noise dominates in the seismic data, and the FWI results significantly deteriorate, especially for the reconstruction of a horizontal reflector located below the rough interface. In contrast, the correlation length has a much smaller effect on both random noise and quality of the inverted results than the roughness height. As shown here, the interface roughness has a major impact on both seismic wave propagation and imaging. When a rough interface is expected to be present in the subsurface, its effect should be critically considered in FWI, in order to properly reconstruct reflectors possibly located below, and then to properly interpret images of the subsurface. In this context, we perform some preliminary tests on the use of a selective extinction method to remove the impact of the roughness on the wavefields. The results are promising and show the potential of the method for better imaging. In addition, the standard deviation of the amplitude of the processed data may be used to evaluate the characteristics of the rough interface, which is also of interest for geophysicists and geologists
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Michel, Kenan. "Distribution of Lateral Forces on Reinforced Masonry Bracing Elements Considering Inelastic Material Behavior - Deformation-Based Matrix Method -". Technische Universität Dresden, 2021. https://tud.qucosa.de/id/qucosa%3A75156.
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The main goal of CIC-BREL project (Cracked and Inelastic Calculation of BRacing Elements) is to develop an analytical method to distribute horizontal forces on bracing elements, in this case reinforced masonry shear walls, of a building considering the cracked and inelastic state of material.
The moment curvature curve of the wall section is created first depending on the section geometry and material properties of both the masonry units and steel reinforcement. This curve will start with an elastic material behavior, then continue in inelastic material behavior where the masonry crushes and the steel start to yield, until the maximum bending moment M_p is reached. Due to reinforced masonry wall ductility, post maximum capacity is also considered assuming a maximum curvature of 0.1%. From the moment curvature curve, the force displacement curve could be extracted depending on the wall height and wall boundary conditions.
Matrix formulation has been developed for both elastic and damaged stiffness matrix, considering different boundary conditions. Fixed-fixed boundary condition which usually exists at the middle stories or last story with strong top diaphragm, fixed-pinned which is the case of the last story that has a relatively soft top diaphragm, and pinned-fixed in the first story case. Other boundary conditions could be considered depending on the degree of fixation on the wall both ends at the top and the bottom.
The matrix formulation combined with the force-displacement curve which considers different material stages (elastic, inelastic, ductile post peak force) is used to define forces in each bracing element even after elastic behavior. After elastic phase of each wall the stiffness of the element will degrade leading to a less portion of the total lateral force; other elastic walls, i.e., stronger walls, will receive more portion of the total force leading to a redistribution of the total force. This process will be iterated until the total force is distributed on each bracing element depending on the wall section state: elastic, inelastic and ductile post-peak capacity. Flowcharts clearly will show this process. Finally, a Fortran code is developed to show examples using this method.
The developed analytical method will be verified by the results of shake table tests held at the University of California in San Diego, USA. Last test performed in the year 2018 uses T-section reinforced masonry walls, subjected to shakings with increased intensity. The total applied force for each shaking could be defined depending on the structural weight and shaking intensity (acceleration). The damage and displacement at each intensity has been recorded and evaluated. Depending on these test results, the results of the analytically developed method will be compared and evaluated. Total system displacement at different lateral load values has been compared for analytical calculations and shake table tests; furthermore, each wall state at increased load has been compared, good agreement could be noticed.:Acknowledgement 5
1. Introduction 7
1.1. State of the Art 9
1.2. Elastic Formulae 9
1.3. Example, Elastic Calculation 12
1.3.1. Stiffnesses of the System 13
1.3.2. Torsion due to Eccentric Lateral Loading 14
1.3.3. Distribution of the Lateral Load on Wall “j” and Floor “i” 15
2. Force Displacement Curve of RM Shear Wall 19
2.1. Introduction 19
2.2. Cantilever Wall 19
2.2.1. Cantilever Elastic Wall 19
2.2.2. Cantilever Inelastic Wall 21
2.2.3. Cantilever Post-Peak Wall 22
2.3. Fixed-Fixed Wall 23
2.3.1. Fixed-Fixed Elastic Wall 23
2.3.2. Fixed-Fixed Inelastic Wall 24
2.3.3. Fixed-Fixed Post-Peak Wall 26
2.4. Moment – Curvature Analysis 26
2.5. Example, Rectangle Cross Section, Cantilever 29
a) Moment Curvature Curve 29
b) Force Displacement Curve 32
2.6. Example, Rectangle Cross Section, Fixed-Fixed 33
a) Moment Curvature Curve 33
b) Force Displacement Curve 33
2.7. Example, T Cross Section, Cantilever 35
a) Moment Curvature Curve 35
b) Force Displacement Curve 41
2.8. Example, T Cross Section, Fixed-Fixed 43
a) Moment Curvature Curve 43
b) Force Displacement Curve 43
3. Matrix Formulation 47
3.1. Procedure 47
3.2. Structure Discretization 47
3.3. Element, i.e.; Wall, Local Stiffness Matrix 48
3.4. Stiffness Matrix of Fixed-Pinned Beam 52
3.4.1. Elastic 52
3.4.2. Pre-Peak Inelastic 54
3.4.3. Post-Peak Inelastic 55
3.4.4. Normal Force Part in the Stiffness Matrix 56
3.5. Stiffness Matrix of Pinned-Fixed Beam 57
3.5.1. Elastic 57
3.5.2. Post-Peak Inelastic 57
3.6. Stiffness Matrix of Fixed-Fixed Beam 58
3.6.1. Elastic 58
3.6.2. Post-Peak Inelastic 60
3.7. Summary of Stiffness Matrices 61
3.7.1. Fixed-Fixed 61
3.7.2. Fixed-Pinned 62
3.7.3. Pinned-Fixed 63
3.8. Transformation Matrix 63
3.9. Assemble the Structure Stiffness Matrix 65
3.10. Assemble the Structure Nodal Vector 66
3.11. Solve, Get Nodal Displacements and Forces 66
4. Matrix Formulation and Deformation Based Method 69
4.1. Elastic Method in Distributing Lateral Force 69
4.2. Elastic and Inelastic Method in Distributing Lateral Force 70
5. Shake Table Tests 73
5.1. Introduction 73
5.2. Design of Test Structure 73
5.3. Material Properties 75
5.4. Tests and Observations 75
5.4.1. Tests up to Mul-90% 76
5.4.2. Tests with Mul-120% 76
5.4.3. Tests with Mul-133% 76
5.5. Deformations 77
6. Verification 81
6.1. T Cross Section, Dimensions, Reinforcement and Materials 81
6.2. Moment Curvature Curve 82
6.3. Force Displacement Curve 85
6.4. Force Displacement Curve of the Structure 88
7. Conclusions and Suggestions 91
8. References 93
Appendix 1, Timoshenko Beam 95
• Fixed-Fixed 95
• Fixed-Pinned 95
• Pinned-Fixed 96
Appendix 2, Bernoulli Beam 97
• Fixed-Fixed 97
• Fixed-Pinned 97
• Pinned-Fixed 98
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Gilardet, Mathieu. "Étude d’algorithmes de restauration d’images sismiques par optimisation de forme non linéaire et application à la reconstruction sédimentaire". Thesis, Pau, 2013. http://www.theses.fr/2013PAUU3040/document.
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Nous présentons une nouvelle méthode pour la restauration d'images sismiques. Quand on l'observe, une image sismique est le résultat d'un système de dépôt initial qui a été transformé par un ensemble de déformations géologiques successives (flexions, glissement de la faille, etc) qui se sont produites sur une grande période de temps. L'objectif de la restauration sismique consiste à inverser les déformations pour fournir une image résultante qui représente le système de dépôt géologique tel qu'il était dans un état antérieur. Classiquement, ce procédé permet de tester la cohérence des hypothèses d'interprétations formulées par les géophysiciens sur les images initiales. Dans notre contribution, nous fournissons un outil qui permet de générer rapidement des images restaurées et qui aide donc les géophysiciens à reconnaître et identifier les caractéristiques géologiques qui peuvent être très fortement modifiées et donc difficilement identifiables dans l'image observée d'origine. Cette application permet alors d'assister ces géophysiciens pour la formulation d'hypothèses d'interprétation des images sismiques. L'approche que nous introduisons est basée sur un processus de minimisation qui exprime les déformations géologiques en termes de contraintes géométriques. Nous utilisons une approche itérative de Gauss-Newton qui converge rapidement pour résoudre le système. Dans une deuxième partie de notre travail nous montrons différents résultats obtenus dans des cas concrets afin d'illustrer le processus de restauration d'image sismique sur des données réelles et de montrer comment la version restaurée peut être utilisée dans un cadre d'interprétation géologiqueWe present a new method for seismic image restoration. When observed, a seismic image is the result of an initial deposit system that has been transformed by a set of successive geological deformations (folding, fault slip, etc) that occurred over a large period of time. The goal of seismic restoration consists in inverting the deformations to provide a resulting image that depicts the geological deposit system as it was in a previous state. With our contribution, providing a tool that quickly generates restored images helps the geophysicists to recognize geological features that may be too strongly altered in the observed image. The proposed approach is based on a minimization process that expresses geological deformations in terms of geometrical constraints. We use a quickly-converging Gauss-Newton approach to solve the system. We provide results to illustrate the seismic image restoration process on real data and present how the restored version can be used in a geological interpretation framework
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Taffarel, Sabrina. "Metodi speditivi per la valutazione della vulnerabilità sismica del costruito storico: approccio all'incertezza nelle forme di aggregazione complessa a diversa scala". Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3421936.
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The prediction of the impact an earthquake could have on existing buildings requires the knowledge of their dynamic behaviour. The procedure to be adopted for this purpose is quite complex and onerous in terms of costs, time and implementation, especially if the study concerns territorial areas rather than single buildings. The definition of methodologies aimed at respecting the principles of economic sustainability and preserving human life and architectural heritage is of paramount importance to assess seismic vulnerability using available resources.
This work aims at developing useful procedures for uncertainties reduction and reliability assessment of available information, a key phase in the study of aggregate buildings at different scales and particularly of existing masonry structures.
For this purpose, vulnerability studies cannot ignore building knowledge and the consequent achieved level of information, which is closely related to the scale of analysis. The increase of the latter entails the decrease of accuracy and quality (reliability) of available data, which are often uncertain. At the same time, it is not economically viable to fill these gaps using traditional approaches which require the execution of complete on-site surveys. The aims of this research thesis are to maximize the benefits deriving from the analysis of available building information and to give a contribution to the advancement of existing seismic vulnerability approaches, adopting either parametric or probabilistic procedures. Data collection and analysis are implemented in databases and geographic information systems aimed at processing already available data, recorded for different purposes. Procedures for assessing seismic vulnerability on an urban scale are defined adopting mechanical approaches on an analytical basis (fragility curves), in which data uncertainty is overcome through the use of deterministic (parametric) or probabilistic (definition of unknown data from certain ones) approaches. An in-depth analysis at a more detailed scale is also provided: the aim, in this case, is to identify suitable methods to represent the boundary conditions of aggregate building portions to be adopted in seismic analysis in a simplified way. The whole methodological process is then applied to several case studies characterized by different morphology, typology and seismicity (Timisoara (RO) historical centre, small historical centres in L’Aquila province –IT-, listed buildings in Verona, Vicenza and Rovigo provinces –IT-, churches damaged by the 2012 earthquakes in Emilia Romagna and Veneto regions –IT-) selected in order to validate and calibrate the implemented procedures on heterogeneous contexts.La previsione dell’impatto causato da un evento sismico in termini di effetti sulle costruzioni esistenti in una data area richiede la conoscenza del comportamento dinamico che tali strutture possono manifestare. La procedura da adottare risulta particolarmente complessa e ancor più onerosa in termini economici, di tempo e operativi, se lo studio è riferito a interi complessi costruttivi e non a singoli edifici. La definizione di percorsi metodologici che mirino al rispetto del principio di sostenibilità economica, oltre a quello di salvaguardia della vita umana e di preservazione nonché tutela del patrimonio è prerogativa necessaria per uno studio di vulnerabilità sismica adeguato alle risorse disponibili. Il presente lavoro di tesi si pone l’obiettivo di sviluppare procedure utili alla riduzione e gestione dell’incertezza, oltre alla valutazione dell’affidabilità dell’informazione insita nello studio di forme di aggregazione complessa a diversa scala, con particolare riferimento alle costruzioni esistenti in aggregato in muratura. A tal fine, lo studio della vulnerabilità non può prescindere dalla conoscenza del costruito, in cui il livello di informazione è strettamente legato all’estensione della scala di analisi. L’aumento della scala si traduce in una diminuzione nel dettaglio e qualità (attendibilità) dei dati disponibili allo studio, che risultano spesso caratterizzati da incertezza. Al contempo, non è economicamente sostenibile perseguire azioni finalizzate a colmare tali lacune attraverso l’adozione di approcci tradizionali, che richiedano l’esecuzione di completi rilievi in sito. L’elaborato di tesi si propone quindi di trarre il massimo profitto dallo studio e dalla messa a sistema di informazioni sul costruito già disponibili, e al contempo di individuare strategie finalizzate a colmare approcci metodologici lacunosi affrontando lo studio da un punto di vista parametrico o probabilistico. Si persegue quindi l’adozione di procedure di analisi dei dati in forma aggregata e di utilizzo di strumenti informativi geografici e database finalizzate all’analisi di informazioni già a disposizione sul costruito ma raccolte con finalità diverse dallo studio di vulnerabilità su scala territoriale. Viene posta l’attenzione alla definizione di procedure per la valutazione della vulnerabilità su ampia scala che adottino approcci meccanici di tipo analitico attraverso curve di fragilità del costruito, in cui l’attenzione sia posta in primis alla gestione dell’incertezza insita nei dati allo studio, superata attraverso l’utilizzo di approcci deterministici (parametrici) o probabilistici (definizione di dati non noti a partire da altri noti). Un approfondimento ad una scala di maggior dettaglio viene inoltre fornito al fine di individuare idonee modalità di rappresentazione semplificata delle condizioni al contorno nell’analisi sismica di porzioni di edificio in contesto aggregato. L’intero percorso proposto è integrato con applicazioni a casi studio diversi per morfologia, tipologia e sismicità (centro storico di Timisoara –RO-, borghi minori in provincia de L’Aquila, beni tutelati presso le provincie di Verona, Vicenza e Rovigo, chiese colpite dagli eventi sismici del 2012 in Emilia Romagna e Veneto) appositamente selezionati al fine di validare e calibrare le procedure adottate su contesti eterogenei.
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Roberts, Mark Alvin. "Full waveform inversion of walk-away VSP data". Paris, Institut de physique du globe, 2007. http://www.theses.fr/2007GLOB0020.
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Du fait de l’épuisement des réserves de pétrole, l’exploration et la production sont réalisées dans des environnements de plus en plus complexes. Faire de l’imagerie sismique sous le sel allochtone (par exemple dômes de sel) demeure une tâche difficile à cause du fait contraste de vitesse dentre le sel et les sédiments voisins et les structures très complexes produites par les déplacements de sel. Les nappes de sel allochtone couvrent de nombreuses régions potentiellement productives dans l’offshore profond du Golfe du Mexique. Forer la base du sel est une tâche extrêmement difficile en raison des pressions de pore fortement variables que l’on recontre dans les sédiments sous le sel. Des méthodes sismiques pour estimer la vitesse des ondes sismiques peuvent être employées en même temps que des formules empiriques pour prévoir la pression de pore. Cependant, il est souvent impossible de mesures précises depuis la surface, et nous avons donc employé des données VSP (Vertical Seismic Profile) “walk-away” cela implique d’effectuer plusieurs tirs sismique à diverses distances du forage (géneralement avec un dispositif de canons á air) tout en enregistrement les vitesses mesurees par des geophones placés à des profondeurs appropriées dans le forage. Avant cette thèse, les données étaient traitées en utilisant l’information d’amplitude en fonction de l’angle dans un simple approximation 1D ou en utilisant l’information de temps de parcours (également avec une approximation 1D). Dans cette thèse, j’ai effectué une inversion 2D de forme d’onde pour résoudre le problème d’estimation des vitesses. Cela a l’avantage d’inverser simultanément l’ensemble des données (comprenant les ondes transmises, les ondes refléchies et les ondes converties) et la méthode inclut l’information de temps de parcours et d’amplitude. L’inversion a été exécute avec des méthodes locales d’inversion du fait de la taille du problème inverse et de la difficulté du problème direct. Les problèmes liés aux grandes variations de le sensibilité inhérents à l’acquisition de données, ont conduit à un examen de la méthode de Gauss- Newton et à des matrices, de préconditionnement possibles pour la méthode du gradient conjugué. En raison de la nature mal contrainte du problème inverse, une régularisation a été appliquée avec une méthode de préconditionnement innovatrice. La méthodologie a été appliquée à des données réelles et la pression de pore a été prédite en utilisant l’équation bien établie de Eaton. En outre, les structures sous le sel ont été déterminées, confirment ainsi l’efficacité de cette techniqueDepletion of the earth’s hydrocarbon reserves has led to exploration and production in increasingly complex environments. Imaging beneath allochthonous salt (e. G. Salt domes) remains a challenging task for seismic techniques due to the large velocity contrast of the salt with neighbouring sediments and the very complex structures generated by salt movement. Extensive allochthonous salt sheets cover many potentially productive regions in the deep-water Gulf of Mexico. Drilling through the base of salt is an extremely challenging task due to widely varying pore-pressure found in the sediments beneath. Seismic methods to estimate the seismic velocity can be used in conjunction with empirical formula to predict the pore pressure. However, accurate measurements are often not possible from surface reflection seismic data, so walk-away Vertical Seismic Profile (VSP) data has been used. This involves repeatedly firing a seismic source at various distances from the borehole (usually an airgun array) while recording the velocities measured by geophones in the borehole placed at appropriate depths near the base of the salt. Before this thesis, the data had been processed using the amplitude versus angle information in a simple one-dimension approximation or using travel time information (also using a 1D assumption). In this thesis, I have used 2D full waveform inversion to tackle the problem of velocity estimation. This has the advantage of simultaneously inverting the whole dataset (including transmitted waves, reflected waves, converted waves) and the method includes traveltime and amplitude information. The inversion was performed using local inversion methods due to the size of the inverse problem and the cost of the forward problem. Concerns over large sensitivity variations, that are inherent in the data acquisition, have lead to an examination of the Gauss-Newton method and possible preconditioning matrices for the conjugate gradient method. Due to the poorly constrained nature of the inverse problem, a smoothness constraint has been applied with an innovative preconditioning method. The methodology has been applied to real data and the pore pressure has been predicted using the well established Eaton equation. In addition, the sub-salt structure was recovered, further demonstrating the value of this technique
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Diaz, Calderon Alvaro Emilio y Ventocilla Brigitte Carolina Meniz. "Evaluación estructural de reservorios apoyados de concreto armado en Lima Metropolitana considerando la norma ACI 350-06 y las normativas peruanas". Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2019. http://hdl.handle.net/10757/626005.
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En la presente tesis se ha desarrollado la evaluación estructural de cinco reservorios circulares del tipo apoyado, construidos entre los años 1977 y 1997, ubicados en zonas de alto riesgo sísmico en Lima Metropolitana y ubicados en suelos medianamente rígidos, con el objetivo de evidenciar si estas estructuras continúan conservando un diseño sísmico adecuado en base a los requerimientos sísmicos actuales, y por ende si serán capaces de resistir un evento sísmico severo y continuar con el servicio.
Para poder modelar y determinar la respuesta de los se reservorios se empleó el modelo equivalente de Housner, obteniendo así la masa impulsiva y convectiva, modelado en el programa SAP2000 con ayuda de las normas ACI 350.3-06 y E.030. En cuanto a la determinación de las fuerzas resistentes, para poder realizar la evaluación estructural correspondiente, se utilizó la norma peruana E.060-2009 Concreto Armado, con la cual se obtuvo dichas fuerzas y se realizaron las verificaciones estructurales.
Con respecto a los resultados de las verificaciones realizadas, se observó que los reservorios en estudio no mantienen un diseño estructural adecuado en cuanto a las solicitaciones sísmicas actuales. Estas deficiencias se plasman en déficit de refuerzo horizontal por corte en muros, cuantía mínima vertical por corte en muros, refuerzo en la base del muro por momento tangencial, armadura requerida en la viga collarín, y refuerzo en el extremo de la cúpula por tracción radial; por lo que estas estructuras, ante la presencia de un evento sísmico severo, se encuentran expuestas a presentar fallas estructurales.In the present thesis has been carried out the structural assessment of five round ground concrete tanks, built between 1977 and 1997, and located in high seismic risk areas in Lima Metropolitana in moderately rigid soils, with the objective of demonstrating if these structures still preserve an adequate structural design base on the current standards and consequently, if they will be able to withstand a severe seismic event and, hence, continue with their service. In order to model and determine the response of the tanks, the Housner’s rigid equivalent model was used, obtaining this way the impulsive and convective masses, which were modeled in the software SAP2000 with the ACI 350.3-06 standard and the E.030 Peruvian standard. Regarding on the determination of the resistant forces, in order to carry out the corresponding structural evaluation, the Peruvian standard “Concreto Armado E.060” was utilized. With regard to the results of the verifications carried out, it was observed that the reservoirs under study do not maintain an adequate structural design in terms of the current seismic solicitations. These deficiencies are reflected in horizontal reinforcement deficit by shear force on the walls, minimum amount of vertical rebar by shear on the walls, reinforcement in the base of the wall by tangential bending moment, rebar required in the beam by radial tensile force, and rebar in the end of the dome by radial traction; so these structures, in the presence of a severe seismic event, are exposed to structural failures.
Tesis
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Beres, Jan. "Caractérisation de l'anisotropie d'une plate-forme carbonatée karsifiée : approche méthodologique conjointe sismique et électrique". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00880759.
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Les résultats présentés dans ce document portent sur les anisotropies sismique et électrique d'un massif calcaire fracturé dans des galeries parallèles souterraines. Les fractures étant orientées verticalement, leurs propriétés sont approximées par isotropie transverse horizontale (HTI). Plusieurs méthodes d'inversion ont été étudié pour traiter les données sismiques (temps d'arrivée des ondes P et S); et pour traiter les données de résistivité électrique mesuré dans une configuration pôle-pôle (valeur de potentiel mesuré).Pour traiter les données sismiques (quatre campagnes), les méthodes étudiées dans ce document sont: une tomographie isotrope, une approximation de cosinus, une inversion anisotrope basée sur l'algorithme Monte-Carlo pour les paramètres de la matrice de rigidité (de l'isotropie transverse horizontale) et une tomographie anisotrope pour un milieu avec une isotropie transverse inclinée. Toutes les méthodes conduisent à la conclusion qu'il y a effectivement une anisotropie présente dans le massif rocheux et confirment la direction de la vélocité maximale parallèle à la direction de la fracturation. Une forte anisotropie de 15 % est présente dans la zone étudiée.Pour traiter les données électriques (deux campagnes), les méthodes étudiées sont une approximation de cosinus et une inversion anisotrope basée sur l'algorithme Monte-Carlo pour les paramètres de résistivité transversale ρT, de résistivité longitudinale ρL et de l'angle d'orientation du modèle par rapport au système de référence. La présence à 180° de deux maxima de résistivité apparente par rapport à l'azimut de mesure ne peuvent être modélisés par des approches conventionnelles. Une modélisation conceptuelle d'un maillage des fils conducteurs dans un milieu non conducteur a été développé et montre des résultats prometteurs, avec le succès de la modélisation des deux maxima.Des mesures répétées montrent de légères variations de résistivité apparentes et des variations des ondes P. Les variations des ondes S ne sont pas prononcés, ce qui reflète un changement de la saturation en eau. La porosité de 10-15% est estimé à partir des mesures sismiques.
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Janošková, Lenka. "Dynamická analýza konstrukce zatížené seismickým zatížením". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226464.
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In this diploma thesis the seismic load on two different models is solved – the first model is a beam hall and the second model is a multistory building. The calculation of seismic load was performed according to standard ČSN EN 1998-1 (Eurocode 8) using the response spectrum analysis and the method of equivalent static forces (substi-tute load). For the combination of seismic responses in different directions are used SRSS and CQC rules. Models and calculations were solved in a student’s version of program RFEM 4.10 (Ing. Software Dlubal, s.r.o.). The comparison of mentioned methods in each models, also the comparison of combinative rules in calculation and the final evaluation of seismic responses on both of models are the subject of this thesis.
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Wang, Yi. "Imagerie haute résolution des structures lithosphériques par inversion de formes d'ondes P télésismiques courte période". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30018.
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La tomographie sismique permet d'imager l'intérieur de la Terre à partir de l'observation des ondes sismiques faite à la surface. L'inversion de forme d'ondes complètes est une méthode tomographique qui permet d'imager les structures lithosphériques de petite échelle. Cette approche demande des méthodes numériques efficaces et précises pour résoudre l'équation des ondes dans des milieux hétérogènes complexes. En théorie, la limite de résolution que l'on peut atteindre avec cette technique est de l'ordre de grandeur de la plus petite longueur d'onde présente dans le champ d'onde utilisé. Du fait de son coût élevé en temps de calcul, l'inversion de formes d'ondes complètes constituait encore récemment un formidable défi pour le sismologue. Cependant, cette situation est en train d'évoluer rapidement du fait des progrès récents à la fois des moyens de calcul haute performance ainsi que des méthodes numériques, mais aussi des déploiements de réseaux denses à l'échelle régionale. Dans cette thèse, nous nous sommes intéressés à l'imagerie haute résolution des structures lithosphériques sous la chaine des Pyrénées par inversion de formes d'ondes P télésismiques courte période. L'objectif principal est d'apporter des contraintes nouvelles sur le taux de raccourcissement subi par cette chaine de montagnes pendant la convergence alpine. Nous utilisons une méthode de modélisation hybride qui couple une méthode de propagation d'onde globale 1D à une méthode d'éléments spectraux 3D à l'échelle régionale. Cette méthode hybride permet de coupler les champs globaux et régionaux sur les bords du domaine régional 3D. Elle limite les calculs 3D qui sont extrêmement couteux à l'intérieur du domaine régional, ce qui permet de réduire considérablement le temps de calcul. La méthode hybride permet ainsi de modéliser des sismogrammes synthétiques jusqu'à des périodes de l'ordre de la seconde, en prenant en compte toutes les complexités qui peuvent affecter la propagation des ondes dans le domaine régional 3D. A l'aide de cette méthode, il est également possible de calculer par la méthode de l'adjoint les dérivées de Fréchet qui relient les perturbations des formes d'onde observées aux perturbations des paramètres élastiques et de la densité dans le milieu. Ces noyaux de sensibilité sont utilisés pour formuler un problème inverse résolu par un algorithme itératif de type L-BFGS. Nous inversons les données de 5 sources télésismiques enregistrées par deux transects denses déployés au niveau des Pyrénées occidentales et centrales pendant l'expérience PYROPE. Nous avons ainsi obtenu les premières sections haute résolution de vitesses des ondes P et S au travers d'une chaine de montagnes. Les modèles tomographiques apportent des évidences claires en faveur d'un sous charriage de la plaque ibérique sous la plaque européenne. Ils montrent également l'importance de l'héritage et en particulier des structures liées à l'épisode de rifting crétacé dans la structuration de la chaineSeismic tomography allows us to image the Earth's interior based on surface observations of seismic waves. The full waveform inversion (FWI) method has the potential to improve tomographic images for the fine scale structures of the lithosphere. For this reason it receives a lot of attention of seismologists. FWI requires an efficient and precise numerical techniques to solve the elastic wave equation in 3D heterogeneous media. Its resolution potential is limited by the shortest wavelength in the seismic wavefield and the wavefield sampling density. Because of the high computational cost of modeling the propagation of seismic waves in heterogeneous media, FWI remains challenging. However, owing to the progress in high performance computational resources and numerical simulation techniques, as well as the deployment of permanent and temporary broadband arrays in the last two decades, this situation has changed dramatically. In this thesis, we focus on the high resolution imaging of lithospheric structure beneath the Pyrenean range by FWI, to quantify the highly controversial amount of convergence that occurred during the formation of this mountain range. In order to obtain finely resolved tomographic images, we exploit short period teleseismic P waves recorded by dense transects. We use a hybrid method that couples a global wave propagation method in a 1D Earth model to a 3D spectral-element method in a regional domain. A boundary coupling approach is used to match the global and regional wavefields on the boundaries of the regional domain. This hybrid method restricts the costly 3D computations inside the regional domain, which dramatically decreases the computational cost. The hybrid method can model teleseismic wavefields down to 1s period, accounting for all the complexities that may affect the propagation of seismic waves in the 3D regional domain. By using this hybrid method, the sensitivity kernels of the least square waveform misfit function with respect to elastic and density perturbations in the regional domain are computed with the adjoint state method. These waveform sensitivity kernels are used in an iterative L-BFGS algorithm to invert broad-band waveform data recorded by two dense transects deployed during the temporary PYROPE experiment across the Pyrenees mountains. We obtain the first high resolution lithospheric sections of compressional and shear velocities across the Pyrenean orogenic belt. The tomographic models provide clear evidence for the underthrust of the thinned Iberian crust beneath the European plate and for the important role of rift-inherited mantle structures during the formation of the Pyrenees