Download or read book Computational Modeling of Ground Bridge Seismic Response and Liquefaction Scenarios written by Zhijian Qiu and published by . This book was released on 2020 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Considerable bridge-ground interaction effects are involved in evaluating the consequences of liquefaction-induced deformations. Due to seismic excitation, liquefied soil layers may result in substantial accumulated permanent deformation of sloping ground near the abutments. Ultimately, global response is dictated by the bridge-ground interaction as an integral system. Generally, a holistic assessment of such response requires a highly demanding full three-dimensional (3D) Finite Element (FE) model of the bridge and surrounding ground. As such, in order to capture a number of the salient involved mechanisms, this study focuses on the liquefaction-induced seismic response of integral bridge-ground systems motivated by details of actual existing bridge-ground configurations. In these 3D FE models, realistic multi-layer soil profiles are considered with interbedded liquefiable/non-liquefiable strata. Effect of the resulting liquefaction-induced ground deformation is explored. Attention is given to overall deformation of the bridge structure due to lateral spreading in the vicinity of the abutments. The derived insights indicate a need for such global analysis techniques, when addressing the potential hazard of liquefaction and its consequences. In order to reproduce the salient response characteristics of soils, three plasticity constitutive models were developed and implemented into the employed computational framework OpenSees including: (1) A pressure-dependent sand model with the Lade-Duncan failure criterion as the yield function to provide a more accurate representation of shear response for gravel, sand and silt, incorporating liquefaction effects, (2) A 3D model for simulating the strain softening behavior of soil materials such as sensitive clays, cemented, over-consolidated, very dense, or frozen soils among others, and (3) A practical 3D model for simulating the cyclic softening behavior of soil materials, as might emanate from pore-pressure build-up, among other stiffness and strength degradation mechanisms. An opportunity to investigate liquefaction-induced lateral spreading and its effects on sheet pile was permitted by availability of large sets of experimental data. The underlying mechanisms of ground failure and damage to sheet pile were further explored by FE numerical simulations of a series of experiments as follows: (1) A total of 17 centrifuge tests on a liquefiable sloping ground, and (2) A total of 11 centrifuge tests on a sheet pile retaining wall system supporting liquefiable soils. The overall measurements were reasonably captured by the conducted FE simulations, demonstrating that the employed constitutive models as well as the overall computational framework have the potential to realistically evaluate the performance of ground-structure systems when subjected to seismically-induced liquefaction. Overall, the primary findings may be summarized as: (1) Response is highly dependent on the bridge-ground system as an integral global entity. Connectivity provided by the bridge deck, soil profile variability along the bridge length, and geometric configuration of the slopes are all factors that can significantly influence the outcome, (2) The bridge structure and its foundations may exert a significant restraining effect on lateral ground deformations. Such restraining effects partially stem from the bridge-ground global connectivity characteristics, which can be of considerable influence, (3) Incorporation of strain softening where applicable, is an important consideration for a wide range of ground scenarios involving sensitive clays, cemented, over-consolidated, very dense, or frozen soils among others, and (4) Strength and stiffness degradation due to strain softening mechanisms might play a substantial role in terms of accumulated deformations and its effect on the resulting ground acceleration and extent of permanent displacement.

Download or read book AASHTO Guide Specifications for LRFD Seismic Bridge Design written by and published by AASHTO. This book was released on 2009 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: Covers seismic design for typical bridge types and applies to non-critical and non-essential bridges. Approved as an alternate to the seismic provisions in the AASHTO LRFD Bridge Design Specifications. Differs from the current procedures in the LRFD Specifications in the use of displacement-based design procedures, instead of the traditional force-based "R-Factor" method. Includes detailed guidance and commentary on earthquake resisting elements and systems, global design strategies, demand modeling, capacity calculation, and liquefaction effects. Capacity design procedures underpin the Guide Specifications' methodology; includes prescriptive detailing for plastic hinging regions and design requirements for capacity protection of those elements that should not experience damage.

Download or read book Seismic Response and Performance Based Assessment of Multi Span Bridge Ground Systems written by Abdullah S E S E Almutairi and published by . This book was released on 2019 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: The conducted study is directed towards enhancements in performance assessment of highway bridges under a wide range of earthquake input shaking scenarios. Seismic response of the superstructure is highly influenced by the global bridge-ground characteristics as an integral system. Therefore, nonlinear representation of the bridge deck, columns, abutments, and foundation response are to be integrated within a unified framework. On this basis, a performance-based earthquake engineering (PBEE) framework was extended and utilized to estimate the post-earthquake loss. To facilitate systematic execution of this analysis framework, a graphical user-interface was further developed and employed. For calibration purposes, a Finite Element (FE) model of an existing large heavily instrumented bridge system at Eureka, California (Samoa Channel Bridge) was developed. Calibration was undertaken based on the recorded earthquake response. Numerical simulations of the bridge model under seismic loading conditions were conducted. Simulation results show that the recorded data provide valuable insights to understand the seismic bridge response and to reliably estimate the damage. Using a practice-oriented pushover procedure, the response of a bridge subjected to liquefaction-induced lateral spreading was investigated. The analysis framework and representative results are presented, where the abutment lateral slope displacement is resisted by the entire bridge configuration. Permanent ground deformation induces longitudinal displacement on the abutment and consequently the entire bridge system. As such, the response of the bridge and its pile foundations were investigated and correlated with the imposed lateral spreading displacement. Overall, the novel contributions and findings are summarized as follows: (1) A bridge-ground seismic response computational analysis tool was further developed for routine practical applications; (2) In this tool, a PBEE framework was extended to handle multi-span bridge-ground systems within an integrated simulation environment; (3) Calibrated by recorded earthquake response, a framework was implemented for a representative large instrumented bridge-ground system in California to illustrate the involved response mechanisms and PBEE outcomes; (4) For response under lateral spreading considerations, a global bridge-ground systematic analysis framework was proposed and developed; (5) Patterned after an existing bridge in California, the framework was implemented with parametric studies addressing the procedure assumptions and potential retrofit bridge configurations.

Download or read book Seismic Design and Assessment of Bridges written by Andreas J. Kappos and published by Springer Science & Business Media. This book was released on 2012-04-18 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book focuses on the use of inelastic analysis methods for the seismic assessment and design of bridges, for which the work carried out so far, albeit interesting and useful, is nevertheless clearly less than that for buildings. Although some valuable literature on the subject is currently available, the most advanced inelastic analysis methods that emerged during the last decade are currently found only in the specialised research-oriented literature, such as technical journals and conference proceedings. Hence the key objective of this book is two-fold, first to present all important methods belonging to the aforementioned category in a uniform and sufficient for their understanding and implementation length, and to provide also a critical perspective on them by including selected case-studies wherein more than one methods are applied to a specific bridge and by offering some critical comments on the limitations of the individual methods and on their relative efficiency. The book should be a valuable tool for both researchers and practicing engineers dealing with seismic design and assessment of bridges, by both making the methods and the analytical tools available for their implementation, and by assisting them to select the method that best suits the individual bridge projects that each engineer and/or researcher faces.

Download or read book Introduction to Computational Earthquake Engineering written by Muneo Hori and published by World Scientific. This book was released on 2011 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introduction to Computational Earthquake Engineering covers solid continuum mechanics, finite element method and stochastic modeling comprehensively, with the second and third chapters explaining the numerical simulation of strong ground motion and faulting, respectively. Stochastic modeling is used for uncertain underground structures, and advanced analytical methods for linear and non-linear stochastic models are presented. The verification of these methods by comparing the simulation results with observed data is then presented, and examples of numerical simulations which apply these methods to practical problems are generously provided. Furthermore three advanced topics of computational earthquake engineering are covered, detailing examples of applying computational science technology to earthquake engineering problems.

Download or read book A Data driven Seismic Damage Assessment Framework of Regional Highway Bridges written by Dong Wang and published by . This book was released on 2020 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent earthquake disasters have demonstrated the seismic vulnerability of highway bridge systems. Rapid seismic assessment of regional highway bridges is critical to help reduce severe loss of life and property. However, measurement of the regional scale system performance faces the challenge of dealing with the large uncertainty in structural properties and spatial characteristics. Traditionally, the numerical modeling approaches are established to simulate nonlinear response for each highway bridge across a regional portfolio. This process is largely limited by accuracy of model and computational effort. Especially some key structural component parameters are almost impossible to be retrieved for some ancient bridges. An alternative data-driven framework is developed to predict seismic responses or damage level of bridges using machine learning techniques. The proposed hierarchically structured framework enables a customized application in different scenarios. Firstly, the typical modeling technique for reinforcement concrete highway bridges is introduced using specific elements for different components. However, the modeling procedures are material-level parameter dependent and time consuming. The nonlinear analysis convergence is also a frustrating problem for numerical simulations. Due to these realistic limitations, a simple, fast and robust numerical model which can be developed with only component-level information needs to be adopted. It's shown that the bridge bent representation can be simplified as a single degree of freedom system. The force-displacement relationship of the bridge can be roughly approximated by a bilinear curve. So a simplified 2D bilinear model is adopted for highway bridges throughout the study. Secondly, the statistical distributions for selected bridge input parameters can be derived based on the regional bridge inventory. Then an iterative process by sampling and filtering input parameters can be used to generate as many bridges as possible candidates for a specific region. The proposed bridge models and selected historical ground motions will be utilized to develop a seismic response prediction model using machine learning for instrumented highway bridges. This study investigates the optimal features to represent the highway bridge and ground motion. Different regression models are applied for near-fault motions and far-field motions and similar performance can be achieved, which significantly outperformed the traditional methods. Finally, to predict the seismic response of the non-instrumented highway bridges whose ground motion information is missing, the kriging interpolation model is implemented first. Then graph network is exploited to improve the performance. Different rules are evaluated for constructing an undirected graph for the highway bridges in an active seismic region. Subsequently, the Node2vec model is conducted to extract the embedding for each node and a graph neural network is implemented to predict the seismic response. Furthermore, vast amounts of text description data from online social platforms can be used to help detect the potential severely damaged bridges rapidly once an earthquake happens. A Convolution Neural Network classification model is implemented to evaluate the overall damage level distribution based on the collected text data. GloVe model is used to generate the word vector as its distributed representation.

Download or read book Parametric Study on the Seismic Performance of Typical Highway Bridges in Canada written by Yuling Gao and published by . This book was released on 2015 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: Earthquakes are one of the main natural hazards that have caused devastations to bridges around the world. Given the observations from past earthquakes, substantial analytical and experimental research work related to bridges has been undertaken in Canada and other countries. The analytical research is focussed primarily on the prediction of the seismic performance of existing bridges. It includes bridge-specific investigations which are mainly conducted using deterministic approach, and investigations of bridge portfolios which are based on probabilistic approach. In both cases, nonlinear time-history analyses are extensively used. To conduct analysis on a given bridge, analytical (i.e., computational) model of the bridge is required. It is known that the seismic response predictions depend greatly on the accuracy of the input of the modeling parameters (or components) considered in the bridge model. The objective of this study is to investigate the effects of the uncertainties of a number of modeling parameters on the seismic response of typical highway bridges. The parameters considered include the superstructure mass, concrete compressive strength, yield strength of the reinforcing steel, yield displacement of the bearing, post-yield stiffness of the bearing, plastic hinge length, and damping. For the purpose of examination, two typical reinforced concrete highway bridges located in Montreal were selected. Three-dimensional (3-D) nonlinear model the bridge was developed using SAP2000. The effects of the uncertainty of each parameter mentioned above were investigated by conducting time-history analyses on the bridge model. In total, 15 records from the earthquakes around the world were used in the time-history analysis. The response of the deck displacement, bearing displacement, column displacement, column curvature ductility, and moment at the base of the column was considered to assess the effect of the uncertainty of the modeling parameter on the seismic response of the bridge. Recommendations were made for the use of these modeling parameters on the evaluation of the seismic performance of bridges.

Download or read book Seismic Studies of the San Francisco Oakland Bay Bridge written by and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational simulation plays a central role in the engineering analysis and design of major bridge structures and accurate simulations are essential for the development of earthquake resistant and economical structural designs. This paper describes new methodologies and computational tools which have recently been developed for simulating earthquake ground motions and the seismic response of cable supported bridges. The simulation tools are described and an example application for an important long-span suspension bridge is demonstrated. The application portion of the study has particular focus on the potential damaging effects of long period displacement pulses and permanent ground displacements which can occur when a bridge is located in the near-field of a major earthquake fault.

Download or read book Experimental and Analytical Seismic Studies of a Four span Bridge System with Innovative Materials written by Carlos Alonso Cruz-Noguez and published by . This book was released on 2010 with total page 1524 pages. Available in PDF, EPUB and Kindle. Book excerpt: As part of a multi-university project utilizing the NSF Network for Earthquake Engineering Simulation (NEES), a quarter-scale model of a four-span bridge incorporating plastic hinges with different advanced materials was tested to failure on the three shake table system at the University of Nevada, Reno (UNR). The bridge was the second test model in a series of three 4-span bridges, with the first model being a conventional reinforced-concrete (RC) structure. The purpose of incorporating advanced materials was to improve the seismic performance of the bridge with respect to two damage indicators: (1) column damage and (2) permanent deformations. The goals of the study presented in this document were to (1) evaluate the seismic performance of a 4-span bridge system incorporating SMA/ECC and built-in rubber pad plastic hinges as well as post-tensioned piers, (2) quantify the relative merit of these advanced materials and details compared to each other and to conventional reinforced concrete plastic hinges, (3) determine the influence of abutment-superstructure interaction on the response, (4) examine the ability of available elaborate analytical modeling techniques to model the performance of advanced materials and details, and (5) conduct an extensive parametric study of different variations of the bridge model to study several important issues in bridge earthquake engineering. The bridge model included six columns, each pair of which utilized a different advanced detail at bottom plastic hinges: shape memory alloys (SMA), special engineered cementitious composites (ECC), elastomeric pads embedded into columns, and post-tensioning tendons. The design of the columns, location of the bents, and selection of the loading protocol were based on pre-test analyses conducted using computer program OpenSees. The bridge model was subjected to two-horizontal components of simulated earthquake records of the 1994 Northridge earthquake. Over 340 channels of data were collected. The test results showed the effectiveness of the advanced materials in reducing damage and permanent displacements. The damage was minimal in plastic hinges with SMA/ECC and those with built-in elastomeric pads. Conventional RC plastic hinges were severely damaged due to spalling of concrete and rupture of the longitudinal and transverse reinforcement. Extensive post-test analytical studies were conducted and it was determined that a computational model of the bridge that included bridge-abutment interaction using OpenSees was able to provide satisfactory estimations of key structural parameters such as superstructure displacements and base shears. The analytical model was also used to conduct parametric studies on single-column and bridge-system response under near-fault ground motions. The effects of vertical excitations and transverse shear-keys at the bridge abutments on the superstructure displacement and column drifts were also explored.

Download or read book Seismic Response of Steel Suspension Bridge written by and published by . This book was released on 1996 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Performing accurate, realistic numerical simulations of the seismic response of long-span bridges presents a significant challenge to the fields of earthquake engineering and seismology. Suspension bridges in particular represent some of the largest and most important man-made structures and ensuring the seismic integrity of these mega-structures is contingent on accurate estimations of earthquake ground motions and accurate computational simulations of the structure/foundation system response. A cooperative, multi-year research project between the Univ. of California and LLNL was recently initiated to study engineering and seismological issues essential for simulating the response of major structures. Part of this research project is focused on the response of the long-span bridges with the San Francisco-Oakland Bay Bridge serving as a case study. This paper reports on the status of this multi-disciplinary research project with emphasis on the numerical simulation of the transient seismic response of the Bay Bridge.

Download or read book Three Dimensional Modeling of Ground Pile Systems and Bridge Foundations written by Ning Wang and published by . This book was released on 2015 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: Continued advancements in high-speed computing and increased availability of earthquake strong motion data have been allowing for further progress in the area of soil-structure-interaction (SSI). Efforts in this dissertation are mainly concerned with three-dimensional (3D) computational analyses of pile foundations and bridge-foundation-ground systems. This includes Finite Element (FE) modeling of ground-pile foundation systems, documentation and assessment of recorded bridge strong motion data, and identification of dynamic bridge-foundation system characteristics. Currently, simplified approaches, such as p-y curves or the foundation stiffness matrix representation, are employed mainly when considering Soil-Structure-Interaction. However, there is much interest in more representative modeling techniques in order to improve our assessments of seismic pile foundation response. In an effort to address this challenge, 3D FE numerical investigations are conducted related to the response of piles and pile groups under lateral load. Distribution of loads and moments among the piles within the group is investigated. Effects of permeability and loading rate on lateral pile response are addressed for saturated relatively impervious cohesionless soil condition. Insights concerning the soil-pile interaction mechanisms are obtained based on the conducted analyses of the soil-pile foundation subsystems. Furthermore, numerical studies are conducted of long-span highway bridge-foundation systems under seismic loading conditions. Three-dimensional FE models of two existing bridges at Eureka California (the Samoa Channel Bridge and the Eureka Channel Bridge) are developed. Methodologies combining numerical modeling with insights gained from strong motion sensor records are investigated to capture the essential structure-foundation-ground system-response mechanisms. Focus is placed on the evaluation of dynamic properties and validation of the bridge FE models based on the recorded earthquake response. An optimization tool (SNOPT) is employed to evaluate the bridge foundation lateral stiffness. The studies show that computational modeling, along with analysis of the recorded ground-pile foundation data, provide an effective mechanism for understanding the entire structure-foundation-ground system response. The OpenSees platform and the user-interfaces OpenSeesPL, MSBridge, as well as SNOPT are employed in various sections of the study. In the domain of highly expensive and time consuming foundation design and/or retrofit, major beneficial outcomes can result from adoption of analysis tools which have been calibrated/verified by actual recorded seismic performance data sets.

Download or read book Experimental and Analytical Seismic Studies of a Four span Bridge System with Composite Piers written by Fatemeh Kavianipour and published by . This book was released on 2013 with total page 1350 pages. Available in PDF, EPUB and Kindle. Book excerpt: Funded by the National Science Foundation through the Network for Earthquake Engineering Simulation (NEES) research program, a major multi-university research project has been in progress at the University of Nevada, Reno. This study describes the study of one of the three large-scale bridge models that were tested to failure on three shake tables system. This model was supported on fiber-reinforced polymer (FRP) composite piers implementing accelerated bridge construction (ABC) techniques. The bridge was a quarter scale model of a 4-span bridge with continuous reinforced concrete superstructure and a drop cap, two-column pier design. Each pier utilized different unconventional FRP details. The purpose of using these innovative details was to improve the seismic performance of the bridge. The first pier consisted of cast-in-place concrete-filled glass FRP tubes with ±55 degree fibers. The second pier consisted of two segmental reinforced concrete columns wrapped with layers of unidirectional carbon FRP sheets to provide confinement and shear reinforcement. Only nominal hoops were used to hold the longitudinal reinforcement, as FRP jacket and tube were sufficient in providing confinement and shear required reinforcement. The third pier had the same configuration as that of pier 1 but the columns and footing were precast. The top connections in piers 1 and 3 consisted of pipe-pin joints to facilitate ABC and provide hinge behavior. The objectives of the study presented in this document were to evaluate the biaxial seismic performance of this bridge system incorporating composite piers, investigate the performance of each detail and compared them to each other and to conventional ones, determine the influence of abutment-superstructure interaction on the response, assess the performance of a bridge model incorporating ABC techniques, evaluate sufficiency of analytical modeling of the performance of composite material and details, and to conduct parametric study of different variations of the bridge model to study the effect of several important factors such as near-fault earthquake effects and the variations in the configuration of the bridge model. large-scale 4-span bridge model was designed, constructed, and subjected to simulated earthquake loading on three shake tables. The simulated shake table motions were the modified 1994 Northridge, CA ground motion recorded in Century City and were applied to the bridge model in ten runs with increasing amplitudes. Over 380 channels of data were collected. Compared to conventional reinforced concrete bridges, experimental results showed superior performance under extreme seismic loading even under lateral drift ratios exceeding 9%. Extensive post-test analytical studies were conducted and it was determined that a computational model of the bridge that included bridge-abutment interaction using OpenSees was able to provide satisfactory estimations of key structural response parameters such as superstructure displacements. The analytical model was also used to conduct parametric studies on response of the bridge model and its variations under near-fault excitations. The effects of changing the column section properties were also explored. It was found that concrete-filled FRP tube piers and CFRP wrapped post-tensioned segmental piers reduce residual displacements compared to their conventional reinforced concrete counter parts even under impulsive near-fault motions.

Download or read book Stochastic Modelling and Analysis for Bridges Under Spatially Varying Ground Motions written by Deyi Zhang and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Earthquake is undoubtedly one of the greatest natural disasters that can induce serious structural damage and huge losses of properties and lives. The resulting destructive consequences not only have made structural seismic analysis and design much more important but have impelled the necessity of more realistic representation of ground motions, such as inclusion of ground motion spatial variations in earthquake modelling and seismic analysis and design of structures. Recorded seismic ground motions exhibit spatial variations in their amplitudes and phases, and the spatial variabilities have an important effect on the responses of structures extended in space, such as long span bridges. Because of the multi-parametric nature and the complexity of the problems, the development of specific design provisions on spatial variabilities of ground motions in modern seismic codes has been impeded. Eurocode 8 is currently the only seismic standard worldwide that gives a set of detailed guidelines to explicitly tackle spatial variabilities of ground motions in bridge design, providing both a simplified design scheme and an analytical approach. However, there is gap between the code-specified provisions in Eurocode 8 and the realistic representation of spatially varying ground motions (SVGM) and the corresponding stochastic vibration analysis (SVA) approaches. This study is devoted to bridge this gap on modelling of SVGM and development of SVA approaches for structures extended in space under SVGM. A complete and realistic SVGM representation approach is developed by accounting for the incoherence effect, wave-passage effect, site-response effect, ground motion nonstationarity, tridirectionality, and spectra-compatibility. This effort brings together various aspects regarding rational seismic scenarios determination, comprehensive methods of accounting for varying site effects, conditional modelling of SVGM nonstationarity, and code-specified ground motion spectra-compatibility. A comprehensive, systematic, and efficient SVA methodology is derived for long span structures under tridirectional nonstationary SVGM. An absolute-response-oriented scheme of pseudo-excitation method and an improved high precision direct integration method are proposed to reduce the enormous computational effort of conventional nonstationary SVA. A scheme accounting for tridirectional varying site-response effect is incorporated in the nonstationary SVA scheme systematically. The proposed highly efficient and accurate SVA approach is implemented and verified in a general finite element analysis platform to make it readily applicable in SVA of complex structures. Based on the proposed SVA approach, parametric studies of two practical long span bridges under SVGM are conducted. To account for spatial randomness and variability of soil properties in soil-structure interaction analysis of structures under SVGM, a meshfree-Galerkin approach is proposed within the Karhunen-Loeve expansion scheme for representation of spatial soil properties modelled as a random field. The meshfree shape functions are proposed as a set of basis functions in the Galerkin scheme to solve integral equation of Karhunen-Loeve expansion, with a proposed optimization scheme in treating the compatibility between the target and analytical covariance models. The accuracy and validity of the meshfree-Galerkin scheme are assessed and demonstrated by representation of covariance models for various homogeneous and nonhomogeneous spatial fields. The developed modelling approaches of SVGM and the derived analytical SVA approaches can be applied to provide more refined solutions for quantitatively assessing code-specified design provisions and developing new design provisions. The proposed meshfree-Galerkin approach can be used to account for spatial randomness and variability of soil properties in soil-structure interaction analysis.

Download or read book Parallel Finite Element Modeling of Earthquake Ground Response and Liquefaction written by Jinchi Lu and published by . This book was released on 2006 with total page 359 pages. Available in PDF, EPUB and Kindle. Book excerpt: Parallel computing is gradually becoming a main stream tool in geotechnical simulations. The need for high fidelity and for modeling of fairly large 3-dimensional (3D) spatial configurations is motivating this direction of research. The main objective of this thesis is to develop a state-of-the-art nonlinear parallel finite element program for earthquake ground/structure response and liquefaction simulation. In the developed parallel code, ParCYCLIC, finite elements are employed within an incremental plasticity, coupled solid-fluid formulation. A constitutive model calibrated by physical tests represents the salient characteristics of sand liquefaction and associated accumulation of shear deformations. Key elements of the computational strategy employed in ParCYCLIC include the development of a parallel sparse direct solver, the deployment of an automatic domain decomposer, and the use of the Multilevel Nested Dissection algorithm for ordering of the finite element nodes. Conducted large-scale geotechnical simulations show that ParCYCLIC is efficiently scalable to a large number of processors. Calibrated FE simulations are increasingly providing a reliable environment for modeling liquefaction-induced ground deformation. Effects on foundations and super-structures may be assessed, and associated remediation techniques may be explored, within a unified framework. Current capabilities of such a FE framework are demonstrated via a series of 3-dimensional (3D) simulations. High-fidelity 3D numerical studies using ParCYCLIC are shown to provide more accurate results. Much time and effort is expended today in building an appropriate finite element mesh and associated data files. User-friendly interfaces can significantly alleviate this problem allowing for high efficiency and much increased confidence. Pre- and post processing interfaces are developed to facilitate use of otherwise computational environments with numerous (often vaguely defined) input parameters. User-friendly interfaces are useful not only for simple model simulations on single-processor computers but also for large-scale modeling on a parallel machine.

Download or read book Challenges and Innovations in Geomechanics written by Marco Barla and published by Springer Nature. This book was released on 2021-01-14 with total page 1029 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the latest advances, innovations, and applications in the field of computational geomechanics, as presented by international researchers and engineers at the 16th International Conference of the International Association for Computer Methods and Advances in Geomechanics (IACMAG 2020/21). Contributions include a wide range of topics in geomechanics such as: monitoring and remote sensing, multiphase modelling, reliability and risk analysis, surface structures, deep structures, dams and earth structures, coastal engineering, mining engineering, earthquake and dynamics, soil-atmosphere interaction, ice mechanics, landfills and waste disposal, gas and petroleum engineering, geothermal energy, offshore technology, energy geostructures, geomechanical numerical models and computational rail geotechnics.

Download or read book Methods Computational Platform Verification and Application of Earthquake soil structure interaction Modeling and Simulation written by Nima Tafazzoli and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Seismic response of soil-structure systems has attracted significant attention for a long time. This is quite understandable with the size and the complexity of soil-structure systems. The focus of three important aspects of ESSI modeling could be on consistent following of input seismic energy and a number of energy dissipation mechanisms within the system, numerical techniquesused to simulate dynamics of ESSI, and influence of uncertainty of ESSI simulations. This dissertation is a contribution to development of one such tool called ESSI Simulator. The work is being done on extensive verified and validated suite for EESI Simulator. Verification and validation are important for high fidelity numerical predictions of behavior of complex systems. This simulator uses finite element method as a numerical tool to obtain solutions for large class of engineering problems such as liquefaction, earthquake-soil-structure-interaction, site effect, piles, pile group, probabilistic plasticity, stochastic elastic-plastic FEM, and detailed large scale parallel models. Response of full three-dimensional soil-structure-interaction simulation of complex structures is evaluated under the 3D wave propagation. Domain-Reduction-Method is used for applying the forces as a two-step procedure for dynamic analysis with the goal of reducing the large size computational domain. The issue of damping of the waves at the boundary of the finite element models is studied using different damping patterns. This is used at the layer of elements outside of the Domain-Reduction-Method zone in order to absorb the residual waves coming out of the boundary layer due to structural excitation. Extensive parametric study is done on dynamic soil-structure-interaction of a complex system and results of different cases in terms of soil strength and foundation embedment are compared. High efficiency set of constitutive models in terms of computational time are developed and implemented in ESSI Simulator. Efficiency is done based on simplifying the elastic-plastic stiffness tensor of the constitutive models. Almost in all the soil-structure systems, there are interface zones in contact with each other. These zones can get detached during the loading or can slip on each other. In this dissertation the frictional contact element is implemented in ESSI Simulator. Extended verification has been done on the implemented element. The interest here is the effect of slipping and gap opening at the interface of soil and concrete foundation on the soil-structure system behavior. In fact transferring the loads to structure is defined based on the contact areas which will affect the response of the system. The effect of gap openings and sliding at the interfaces are shown through application examples. In addition, dissipation of the seismic energy due to frictional sliding of the interface zones are studied. Application Programming Interface (API) and Domain Specific Language (DSL) are being developed to increase developer's and user's modeling and simulation capabilities. API describes software services developed by developers that are used by users. A domain-specific language (DSL) is a small language which usually focuses on a particular problem domain in software. In general DSL programs are translated to a common function or library which can be viewed as a tool to hide the details of the programming, and make it easier for the user to deal with the commands.

Download or read book Seismic Modeling Quantifying and Protection of Highway Bridges Considering Shaking and Lateral Spreading written by Yazhou Xie and published by . This book was released on 2017 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation systematically addresses the modeling, quantifying, and protection of highway bridges against earthquake hazards. Firstly, the research substantially improves the p-y spring based simulation method to predict the seismic responses of highway bridges that accounts for various soil-structure interaction effects. Closed-form formulae are provided for the p-y spring input parameters to capture the bridge-embankment interaction effects, based on which an integrated step-by-step modeling procedure is developed. The procedure is applied to simulate the seismic responses of a well instrumented highway overcrossing and validated against the recorded responses during the 1992 Petrolia earthquake. Secondly, the study derives a response modification factor to quantify the relative impact of liquefaction induced lateral spreading with respect to seismic shaking on column drifts for highway bridges. The column drift response under lateral spreading is correlated to the crust layer energy imposed on the pile foundation at bridge piers. Under seismic shaking, the column drift ratio is directly related to the peak ground acceleration. By normalizing the column drift under the lateral spreading to that of under the seismic shaking, the proposed modification factor captures key features of how columns respond under both lateral spreading and seismic shaking, and offers reliable column drift demand predictions. Thirdly, this study investigates the effectiveness and optimal design of seismic protective devices for highway bridges. Component-level fragility functions are developed by using the probabilistic seismic demand analysis. To transparently quantify the bridge performance at the system level, seismic repair cost ratios are derived to combine damage probabilities, damage ratios and replacement costs of critical bridge components. Thereafter, a multi-objective genetic optimization method with the Pareto optimal concept is employed to identify the optimal design parameters of protective devices. Subsequently, the research derives a consistent performance index to facilitate the performance-based design and optimization of seismic protective devices. By converting the system-level repair cost ratio to be a function of median-level engineering demand parameters, a uniform design surface is generated for various protection designs. The derived surface can be easily implemented in the performance-based seismic protection design and optimization without iteratively updating the design goal when a new group of design parameters are considered. The robustness of the proposed method is examined in a case study to identify the optimal protection designs by using a genetic optimization scheme. Lastly, the study derives the seismic demand models for bridge rocking columns with foundation on rigid supports when subject to horizontal near-fault strong motions. The system equations of motion are derived and solved to incorporate the column flexibility and the rocking impact mechanism. By representing the near-fault ground motions with corresponding pulses, dimensional analyses are carried out to regress the closed-form expressions of system's drift and uplift demands. A rigorous validation process is implemented to demonstrate that the proposed models can be used with confidence to predict the seismic demands of the rocking system directly from structural and ground motion characteristics.