Download or read book Performance based Seismic Assessment of Skewed Bridges with and Without Considering Soil structure Interaction Effects for Various Site Classes written by Abdoulreza Ghotbi and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: This study aims to investigate the behavior of skewed and straight highway overpass bridges both with and without taking into account the effects of Soil-Structure Interaction (SSI) due to near-fault ground motions. Both deterministic (i.e., pushover and nonlinear dynamic analyses) and probabilistic approaches were utilized. A set of response sensitivity analyses was performed considering various skew angles, column elements, and soil properties for bridge considered both as fixed-base and SSI models. It has been observed that as the skew angle increased, the bridge responded more severely to the ground motion. For instance, the deck rotation and shear-keys displacement increased with an increase in the skew angle. A modal pushover analysis was also performed in conjunction with the nonlinear dynamic analysis. It has been found that combining the bridge responses for various modes of vibration resulted in a relatively accurate seismic response compared to the nonlinear dynamic analysis while saving time and analysis cost, to a great extent. A probabilistic analysis was also performed considering record-to-record variability in ground motion, and a set of probabilistic seismic demand and fragility plots was generated. The effects of change in the skew angle and also SSI were studied to see various bridge responses. The damage probability increased especially with respect to deck rotation as the skew angle increased. The SSI had a decreasing effect on the overall response of the bridge with pile foundation.
Download or read book Seismic Performance of Soil Foundation Structure Systems written by Nawawi Chouw and published by CRC Press. This book was released on 2017-08-25 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seismic Performance of Soil-Foundation-Structure Systems presents invited papers presented at the international workshop (University of Auckland, New Zealand, 21-22 November 2016). This international workshop brought together outstanding work in earthquake engineering that embraces a holistic consideration of soilfoundation-structure systems. For example, the diversity of papers in this volume is represented by contributions from the fields of shallow foundation in liquefiable soil, spatially distributed lifelines, bridges, clustered structures (see photo on front cover), sea floor seismic motion, multi-axial ground excitation, deep foundations, soil-foundation-structurefluid interaction, liquefaction-induced settlement and uplift with SFSI. A fundamental knowledge gap is manifested by the isolated manner geotechnical and structural engineers work. A holistic consideration of soil-foundation-structures systems is only possible if civil engineers work collaboratively to the mutual benefit of all disciplines. Another gap occurs by the retarded application of up-to-date research findings in engineering design practices. Seismic Performance of Soil-Foundation-Structure Systems is the outcome from the recognized need to close this gap, since it has been observed that a considerable delay exists between published research findings and application of the principles revealed by the research. Seismic Performance of Soil-Foundation-Structure Systems will be helpful in developing more understanding of the complex nature of responses these systems present under strong earthquakes, and will assist engineers in closing the gaps identified above.
Download or read book Performance based Seismic Assessment of Skewed Bridges written by Peyman Kavianijopari and published by . This book was released on 2011 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study focuses on identifying, both qualitatively and quantitatively, the seismic behavior of reinforced concrete bridges with seat-type abutments under earthquake loading, especially with respect to abutment skew angle. To that end, the study proposes novel methodologies for modeling skew-angled seat-type abutments and for seismic response assessment of structures whose response is characterized as "multi-phased." The proposed methodologies are applied to a comprehensive database of bridges with combinations of a variety of bridge geometric properties, including: (1) number of spans; (2) number of columns per bent; (3) column-bent height; (4) span arrangement; and (5) abutment skew angle. An extensive nonlinear response history analysis was conducted using three sets of ground motions representing records for rock sites and soil sites, as well as others that contained pronounced velocity pulses, denoted as "pulse-like." We demonstrate that demand parameters for skew-abutment bridges, such as deck rotation, abutment unseating, and column drift ratio, are higher than those for straight bridges. By investigating the sensitivity of various response parameters to variations in bridge geometry and ground motion characteristics, we show that bridges with larger abutment skew angles bear a higher probability of collapse due to excessive rotation, and that shear keys can play a major role in reducing deck rotations and thus the probability of collapse. We further show that resultant peak ground velocity (PGVres) is the most efficient ground motion intensity measure (IM) compared to many other IMs. In view of the skewed bridges' explicit changes in demand parameter behavior due to shear key failure, we propose a probabilistic-based approach for multi-phase structural response assessment. This method, denoted as "Multi-Phase Probabilistic Assessment of Structural Response to Seismic Excitations," or M-PARS, provides a probabilistic framework for computing the complementary probability distribution function of an engineering demand parameter given the ground motion intensity measure, G(EDP\IM).
Download or read book Performance based Seismic Assessment of Skewed Bridges written by Peyman Kaviani and published by . This book was released on 2014 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Investigation of the Effectiveness of Existing Bridge Design Methodology in Providing Adequate Structural Resistance to Seismic Disturbances written by Ma-chi Chen and published by . This book was released on 1977 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Four different mathematical model elements are incorporated into the three dimensional computer program which possess the capability of performing linear or nonlinear-time-history dynamic response analysis. Solid finite element modelling is used for the backfill soils and the abutment walls. The bridge deck, pier columns and pier caps are modelled using prismatic beam elements. A frictional element is used to model the discontinuous behavior at the interfaces of the backfill soils and abutments. Boundary elements provide foundation flexibility at the base of columns supported on either piles or spread footings. In the nonlinear mathematical model the effects of separation, impact and slippage at the interfaces between the abutment walls and the backfill soils are taken into consideration. Computational efficiency is achieved through the use of mathematical techniques including matrix reduction procedures, interaction procedures and variable time steps. A number of analytical solutions are carried out considering a skewed three-span bridge with backfill soils. Different mathematical models are used to study the parameters which may influence the seismic response of the bridge.
Download or read book Seismic Analysis of Intake outlet Tower and Bridge Systems Considering the Multiple Support Excitation and Soil structure Interaction Effects written by Aidcer L. Vidot Vega and published by . This book was released on 2004 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book Seismic Analysis of Integral Abutment Bridges Considering Soil Structure Interaction written by Reza Vasheghani Farahani and published by . This book was released on 2010 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Integral abutment bridges are jointless bridges in which the deck is continuous and connected monolithically with the abutment walls supported typically by a single row of piles. This thesis focuses on the effects of two major parameters on the seismic behavior of an integral abutment bridge in Tennessee by considering soil-structure interaction around the piles and in back of the abutments: (1) clay stiffness (medium vs. hard) around the piles, and (2) level of sand compaction (loose vs. dense) of the abutment wall backfilling. Modal and nonlinear time history analyses are performed on a three dimensional detailed bridge model using the commercial software SAP2000, which clearly show that (1) compacting the backfilling of the abutment wall will increase the bridge dominant longitudinal natural frequency considerably more than increasing the clay stiffness around the piles; (2) the maximum deflection and bending moment in the piles under seismic loading will happen at the pile-abutment interface; (3) under seismic loading, densely-compacted backfilling of the abutment wall is generally recommended since it will reduce the pile deflection, the abutment displacement, the moments in the steel girder, and particularly the pile moments; (4) under seismic loading, when the piles are located in firmer clay, although the pile deflection, the abutment displacement, and the maximum girder moment at the pier and the mid-span will decrease, the maximum pile moment and the maximum girder moment at the abutment will increase.
Download or read book Performance based Seismic Bridge Design written by M. Lee Marsh and published by Transportation Research Board. This book was released on 2013 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: "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.
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 Uncertainty Treatment in Performance Based Seismic Assessment of Typical Bridge Classes in United States written by Mohammad Mehdizadeh and published by . This book was released on 2014 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bridge networks are expensive and complex infrastructures and are essential components of today's transportation systems. Despite the advancement in computer aided modeling and increasing the computational power which is increasing the accessibility for developing the fragility curves of bridges, the complexity of the problem and uncertainties involved in fragility analysis of the bridge structures in addition to difficulties in validating the results obtained from the analysis requires precaution in utilization of the results as a decision making tool. The main focus of this research is to address, study and treatment of uncertainties incorporated in various steps of performance based assessments (PBA) of the bridge structures. In this research the uncertainties is divided into three main categories. First, the uncertainties that come from ground motions time and frequency content alteration because of scarcity of the recorded ground motions in the database. Second, uncertainties associated in the modeling and simulation procedure of PBA, and third uncertainties originated from simplistic approach and methods utilized in the conventional procedure of PBA of the structures. Legitimacy of the scaling of ground motions is studied using the response of several simple nonlinear systems to amplitude scaled ground motions suites. Bias in the response obtained compared to unscaled records for both as recorded and synthetic ground motions. Results from this section of the research show the amount of the bias is considerable and can significantly affect the outcome of PBA. The origin of the bias is investigated and consequently a new metric is proposed to predict the bias induced by ground motion scaling without nonlinear analysis.
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 Evaluation of Base Isolation and Soil Structure Interaction Effects on the Seismic Response of Bridges written by Wentao Dai and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A continuous formulation to calculate the dynamic stiffness matrix of structural members with distributed masses is presented in detail and verified with some simple examples. The dynamic model of a specific bridge (the Marga-Marga bridge in Chile) was developed using this formulation, and the model was then used to obtain the transfer functions of the motions at different points of the bridge due to seismic excitation. The model included rubber pads, used for base isolation, as additional members. The transfer functions were obtained with and without rubber pads to investigate their effect. The dynamic stiffness of complete pile foundations was calculated by a semi-analytical solution with Poulos' assumption. General observations on group effects under various conditions were obtained from the result of these studies. The dynamic stiffness of the pile foundations for the Marga-Marga bridge was then obtained and used to study the soil structure interaction effects on the seismic response of the bridge. Records obtained during a real earthquake were examined and interpreted in light of the results from all these analyses. Finally, conclusions and recommendations on future studies are presented.
Download or read book Seismic Analysis of the RC Integral Bridges Using Performance based Design Approach Including Soil Structure Interaction written by Kianosh Ashkani Zadeh and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Ground Motion Spatial Variations and Random Site Conditions on Seismic Responses of Bridge Structures written by Kaiming Bi and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: [Truncated abstract] The research carried out in this thesis concentrates on the modelling of spatial variation of seismic ground motions, and its effect on bridge structural responses. This effort brings together various aspects regarding the modelling of seismic ground motion spatial variations caused by incoherence effect, wave passage effect and local site effect, bridge structure modelling with soil-structure interaction (SSI) effect, and dynamic response modelling of pounding between different components of adjacent bridge structures. Previous studies on structural responses to spatial ground motions usually assumed homogeneous flat site conditions. It is thus reasonable to assume that the ground motion power spectral densities at various locations of the site are the same. The only variations between spatial ground motions are the loss of coherency and time delay. For a structure located on a canyon site or site of varying conditions, local site effect will amplify and filter the incoming waves and thus further alter the ground motion spatial variations. In the first part of this thesis (Chapters 2-4), a stochastic method is adopted and further developed to study the seismic responses of bridge structures located on a canyon site. In this approach, the spatially varying ground motions are modelled in two steps. Firstly, the base rock motions are assumed to have the same intensity and are modelled with a filtered Tajimi- Kanai power spectral density function and an empirical spatial ground motion coherency loss function. Then, power spectral density function of ground motion on surface of the canyon site is derived by considering the site amplification effect based on the onedimensional seismic wave propagation theory. The structural responses are formulated in the frequency domain, and mean peak responses are estimated by the standard random vibration method. The dynamic, quasi-static and total responses of a frame structure (Chapter 2) and the minimum separation distances between an abutment and the adjacent bridge deck and between two adjacent bridge decks required in the modular expansion joint (MEJ) design to preclude pounding during strong ground motion shaking are studied (Chapter 3). The influence of SSI is also examined (in Chapter 4) by modelling the soil surrounding the pile foundation as frequency-dependent springs and dashpots in the horizontal and rotational directions. A method is proposed to simulate the spatially varying earthquake ground motion time histories at a canyon site with different soil conditions. This method takes into consideration the local site effect on ground motion amplification and spatial variations. The base rock motions are modelled by a filtered Tajimi-Kanai power spectral density function or a stochastic ground motion attenuation model, and the spatial variations of seismic waves on the base rock are depicted by a coherency loss function. The power spectral density functions on the ground surfaces are derived by considering seismic wave propagations through the local site by assuming the base rock motions consisting of outof- plane SH wave and in-plane combined P and SV waves with an incident angle to the site. The spectral representation method is used to simulate the multi-component spatially varying earthquake ground motions...
Download or read book Evaluation of Soil structure Interaction Effects in the Dynamic Response of Instrumented Bridges Based on Seismic Records written by Miguel Fraino and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Seismic Assessment and Retrofit of Existing Multi column Bent Bridges written by Cole C. McDaniel and published by . This book was released on 2006 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this research was to assess the seismic vulnerability of typical pre-1975 WSDOT prestressed concrete multi-column bent bridges. Additional objectives included determining the influence of soil-structure-interaction on the bridge assessment and evaluating the effects of non-traditional retrofit schemes on the global response of the bridges. Overall this research highlighted the vulnerability of non-monolithic bridge decks and shear-dominating bridge columns in pre-1975 WSDOT prestressed concrete multi-column bent bridges as well as the importance of including soil-structure-interaction, calibrating the force/displacement characterization of the columns to experimental test data and detailed modeling of the bridges such as expansion joint/girder interaction. In the end, the seismic assessment of bridges is a cost/efficiency issue. Each bridge is different, therefore, investing in improved analyses up front will enable an efficient use of the limited funds for bridge improvement, resulting in a significant savings overall.
