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| Author | : Yili Huo |
| Publisher | : |
| Total Pages | : 650 |
| Release | : 2011 |
| Genre | : |
| ISBN | : |
| Author | : Seyyed Nima Mahmoudi |
| Publisher | : |
| Total Pages | : |
| Release | : 2015 |
| Genre | : |
| ISBN | : |
"Fragility curves are useful tools for reliability evaluation of structures as well as for identifying the most vulnerable components. This study focuses on the seismic fragility analysis of highway bridges. Two main approaches are used for this purpose: component-based and system-based fragility analyses. The seismic vulnerability of two existing bridges located in Montreal are assessed as case studies.The main goal of this study is to develop reliable seismic fragility curves for highway bridge structures considering all significant uncertainties involved. Uncertainties include those associated with modelling structural behavior, seismic inputs and definition of component capacities. The procedures are implemented for the fragility assessment of two existing bridges as case studies. For this purpose, deterioration due to corrosion of reinforcing steel and its effects on structural behavior are included, as well as validation of the Finite Element Model using dynamic properties obtained from ambient noise measurements. Proposed methods for the selection of appropriate set of ground motion records, the type of model analysis and probabilistic modeling of component capacities are presented and illustrated for the two case studies.Two stochastic methods are proposed for validating the Finite Element Model of a bridge. The first method is based on classical hypothesis testing procedures while the second uses a Bayesian updating approach. The stochastic methods are also used to update the input parameters, detect probable major damage in the bridges and determine the confidence interval on model responses as a function of laboratory test data and field observations.In order to limit the uncertainties involved in seismic inputs, a state-of-the-art ground motion record selection procedure based on Conditional Mean Spectrum (CMS) is used. Incremental Dynamic Analysis (IDA) is performed to evaluate the record to record variability in seismic responses and to capture the nonlinearity in structural component behaviors.The first part of the thesis describes the application of component-based fragility analysis for the seismic vulnerability assessment of highway bridge structures. IDA is performed on the validated Finite Element model of the structure using an appropriate set of ground motion records. The results are used for estimating the relationships between ground motion intensity measures and component demands. A Joint Probabilistic Seismic Demand Model (JPSDM) is fitted to the results in order to develop component and system fragility curves of the structure.Since the component based fragility analysis of complex structures comprising a large number of components requires enormous computational efforts, in the second part of this study, a system-based approach for developing seismic system fragility curves is proposed which uses Support Vector Machines (SVM). SVM is a state-of-the-art machine learning technique which is used to discover patterns in highly dimensional and complex data sets. In this application, SVM is used to determine the relationship between ground motion intensity measures and peak structural responses. Seismic fragility curves are developed using Probabilistic SVM (PSVM). Finally, the efficiency of the proposed PSVM method for its application to vector-valued ground motion Intensity Measures (IM) as well as traditional single-valued IM are investigated." --
| Author | : Reihaneh Sarraf Shirazi |
| Publisher | : |
| Total Pages | : 642 |
| Release | : 2015 |
| Genre | : Electronic books |
| ISBN | : |
Curved bridges are constructed to conform to geometric constraints resulting from traffic and structural restrictions. They are different from their straight counterparts since the response coupling in the longitudinal and transverse directions and rotation of the superstructure may lead to significantly different seismic response. Observations from past earthquakes highlighted the seismic vulnerability of these bridges due to this coupled response. The consequence of bridge damage on the performance of transportation system is commonly assessed through Seismic Risk Assessment (SRA) of lifeline systems. Thus, seismic fragility curves are essential input to SRA to estimate damage to highway bridges and consequently to the network. The literature review shows shortcomings in fragility studies on the effect of horizontal curvature of bridges, specifically concrete box-girder bridges. This study aims to fill in the gap on the current state-of-the-knowledge in the seismic response and vulnerability of curved concrete box-girder bridges. Since this bridge type is common in California, the modern details adopted by CALTRANS along with the current seismic design considerations from SDC (2013) are used to select the representative benchmark bridges. To incorporate the uncertainty in geometrical, structural, and material properties of bridges into the analytical models, five sets of statistical bridge samples (each includes 160 bridges) with various subtended angles are developed. These bridge models are subjected to four sets of ground motions representing different site soil conditions and spectral characteristics. A total of 800 response history analyses are performed and the results are used to develop analytical component and system fragility functions for a range of subtended angles. A comprehensive study on the effect of horizontal curvature on the bridge dynamic characteristics and component seismic response is conducted. The median of system (bridge) fragility curves are proposed as a function of the subtended angle for each ground motion set. These functions can be used as input into SRA tools. The fragility analysis shows that the seismic vulnerability of bridges depends on the soil condition of the site and ground motion characteristics as well as the horizontal curvature of the bridge. Columns are found to have the most significant contribution to the system fragility curves. The analyses confirm that the current seismic details including PTFE/spherical bearings and isolated shear keys, suggested by CALTRANS, achieve the objectives of capacity-protected design of piles. Since the dynamic characteristics of bridges are sensitive to the curvature, curved bridges with subtended angles greater than 30 degrees require explicit modeling of curved geometry. In curved bridges, the coupling of transverse and longitudinal modes reduces the dominance of the fundamental mode in the bridge response and leads to the contribution of higher modes. The statistical evaluation of structural demands indicates that the curvature and the torsion demands on columns are amplified in curved bridges.
| Author | : M. Lee Marsh |
| Publisher | : Transportation Research Board |
| Total Pages | : 138 |
| Release | : 2013 |
| Genre | : Technology & Engineering |
| ISBN | : 0309223806 |
"TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 440, Performance-Based Seismic Bridge Design (PBSD) summarizes the current state of knowledge and practice for PBSD. PBSD is the process that links decision making for facility design with seismic input, facility response, and potential facility damage. The goal of PBSD is to provide decision makers and stakeholders with data that will enable them to allocate resources for construction based on levels of desired seismic performance"--Publisher's description.
| Author | : Andreas J Kappos |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 233 |
| Release | : 2012-04-17 |
| Genre | : Technology & Engineering |
| ISBN | : 9400739435 |
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.
| Author | : Dong Wang |
| Publisher | : |
| Total Pages | : 116 |
| Release | : 2020 |
| Genre | : |
| ISBN | : |
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.
| Author | : Masanobu Shinozuka |
| Publisher | : |
| Total Pages | : 200 |
| Release | : 2007 |
| Genre | : Concrete bridges |
| ISBN | : |
| Author | : Karthik Narayan Ramanathan |
| Publisher | : |
| Total Pages | : |
| Release | : 2012 |
| Genre | : Bridges |
| ISBN | : |
Quantitative and qualitative assessment of the seismic risk to highway bridges is crucial in pre-earthquake planning, and post-earthquake response of transportation systems. Such assessments provide valuable knowledge about a number of principal effects of earthquakes such as traffic disruption of the overall highway system, impact on the regions' economy and post-earthquake response and recovery, and more recently serve as measures to quantify resilience. Unlike previous work, this study captures unique bridge design attributes specific to California bridge classes along with their evolution over three significant design eras, separated by the historic 1971 San Fernando and 1989 Loma Prieta earthquakes (these events affected changes in bridge seismic design philosophy). This research developed next-generation fragility curves for four multispan concrete bridge classes by synthesizing new knowledge and emerging modeling capabilities, and by closely coordinating new and ongoing national research initiatives with expertise from bridge designers. A multi-phase framework was developed for generating fragility curves, which provides decision makers with essential tools for emergency response, design, planning, policy support, and maximizing investments in bridge retrofit. This framework encompasses generational changes in bridge design and construction details. Parameterized high-fidelity three-dimensional nonlinear analytical models are developed for the portfolios of bridge classes within different design eras. These models incorporate a wide range of geometric and material uncertainties, and their responses are characterized under seismic loadings. Fragility curves were then developed considering the vulnerability of multiple components and thereby help to quantify the performance of highway bridge networks and to study the impact of seismic design principles on the performance within a bridge class. This not only leads to the development of fragility relations that are unique and better suited for bridges in California, but also leads to the creation of better bridge classes and sub-bins that have more consistent performance characteristics than those currently provided by the National Bridge Inventory. Another important feature of this research is associated with the development of damage state definitions and grouping of bridge components in a way that they have similar consequences in terms of repair and traffic implications following a seismic event. These definitions are in alignment with the California Department of Transportation's design and operational experience, thereby enabling better performance assessment, emergency response, and management in the aftermath of a seismic event. The fragility curves developed as a part of this research will be employed in ShakeCast, a web-based post-earthquake situational awareness application that automatically retrieves earthquake shaking data and generates potential damage assessment notifications for emergency managers and responders.
| Author | : M. J. N. Priestley |
| Publisher | : John Wiley & Sons |
| Total Pages | : 704 |
| Release | : 1996-04-12 |
| Genre | : Technology & Engineering |
| ISBN | : 9780471579984 |
Because of their structural simplicity, bridges tend to beparticularly vulnerable to damage and even collapse when subjectedto earthquakes or other forms of seismic activity. Recentearthquakes, such as the ones in Kobe, Japan, and Oakland,California, have led to a heightened awareness of seismic risk andhave revolutionized bridge design and retrofit philosophies. In Seismic Design and Retrofit of Bridges, three of the world's topauthorities on the subject have collaborated to produce the mostexhaustive reference on seismic bridge design currently available.Following a detailed examination of the seismic effects of actualearthquakes on local area bridges, the authors demonstrate designstrategies that will make these and similar structures optimallyresistant to the damaging effects of future seismicdisturbances. Relying heavily on worldwide research associated with recentquakes, Seismic Design and Retrofit of Bridges begins with anin-depth treatment of seismic design philosophy as it applies tobridges. The authors then describe the various geotechnicalconsiderations specific to bridge design, such as soil-structureinteraction and traveling wave effects. Subsequent chapters coverconceptual and actual design of various bridge superstructures, andmodeling and analysis of these structures. As the basis for their design strategies, the authors' focus is onthe widely accepted capacity design approach, in which particularlyvulnerable locations of potentially inelastic flexural deformationare identified and strengthened to accommodate a greater degree ofstress. The text illustrates how accurate application of thecapacity design philosophy to the design of new bridges results instructures that can be expected to survive most earthquakes withonly minor, repairable damage. Because the majority of today's bridges were built before thecapacity design approach was understood, the authors also devoteseveral chapters to the seismic assessment of existing bridges,with the aim of designing and implementing retrofit measures toprotect them against the damaging effects of future earthquakes.These retrofitting techniques, though not considered appropriate inthe design of new bridges, are given considerable emphasis, sincethey currently offer the best solution for the preservation ofthese vital and often historically valued thoroughfares. Practical and applications-oriented, Seismic Design and Retrofit ofBridges is enhanced with over 300 photos and line drawings toillustrate key concepts and detailed design procedures. As the onlytext currently available on the vital topic of seismic bridgedesign, it provides an indispensable reference for civil,structural, and geotechnical engineers, as well as students inrelated engineering courses. A state-of-the-art text on earthquake-proof design and retrofit ofbridges Seismic Design and Retrofit of Bridges fills the urgent need for acomprehensive and up-to-date text on seismic-ally resistant bridgedesign. The authors, all recognized leaders in the field,systematically cover all aspects of bridge design related toseismic resistance for both new and existing bridges. * A complete overview of current design philosophy for bridges,with related seismic and geotechnical considerations * Coverage of conceptual design constraints and their relationshipto current design alternatives * Modeling and analysis of bridge structures * An exhaustive look at common building materials and theirresponse to seismic activity * A hands-on approach to the capacity design process * Use of isolation and dissipation devices in bridge design * Important coverage of seismic assessment and retrofit design ofexisting bridges
| Author | : Bryant G. Nielson |
| Publisher | : |
| Total Pages | : |
| Release | : 2005 |
| Genre | : Bridges |
| ISBN | : |
Historical seismic events such as the San Fernando earthquake of 1971 and the Loma Prieta earthquake of 1989 did much to highlight the vulnerabilities in many existing highway bridges. However, it was not until 1990 that this awareness extended to the moderate seismic regions such as the Central and Southeastern United States (CSUS). This relatively long neglect of seismic issues pertaining to bridges in these moderate seismic zones has resulted in a portfolio of existing bridges with seismic deficiencies which must be assessed and addressed. An emerging decision tool, whose use is becoming ever increasingly popular in the assessment of this seismic risk, is that of seismic fragility curves. Fragility curves are conditional probability statements which give the probability of a bridge reaching or exceeding a particular damage level for an earthquake of a given intensity level. As much research has been devoted to the implementation of fragility curves in risk assessment packages, a great need has arisen for bridge fragility curves which are reliable, particularly for those in moderate seismic zones. The purpose of this study is to use analytical methods to generate fragility curves for nine bridge classes which are most common to the CSUS. This is accomplished by first considering the existing bridge inventory and assessing typical characteristics and details from which detailed 3-D analytical models are created. The bridges are subjected to a suite of synthetic ground motions which were developed explicitly for the region. Probabilistic seismic demand models (PSDM) are then generated using these analyses. From these PSD models, fragility curves are generated by considering specific levels of damage which may be of interest. The fragility curves show that the most vulnerable of all the bridge nine bridge classes considered are those utilizing steel girders. Concrete girder bridges appear to be the next most vulnerable followed by single span bridges of all types. Various sources of uncertainty are considered and tracked throughout this study, which allows for their direct implementation into existing seismic risk assessment packages.
