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Towards multiple hazard resilient bridges:a methodology for modeling frequent and infrequent time-varying loads Part I,comprehensive reliability and partial failure probabilities

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Earthquake Engineering and Engineering Vibration 2012年第3期11卷 293-301页

作者： Zach Liang george c.lee Department of Mechanical and Aerospace Engineering University at Buffalo Department of civil Structural and Environmental EngineeringUniversity at Buffalo

The current AASHTO load and resistance factor design （LRFD） guidelines are formulated based on bridge reliability, which interprets traditional design safety factors into more rigorously deduced factors based on the theory of probability. This is a major advancement in bridge design specifications. However, LRFD is only calibrated for dead and live loads. In cases when extreme loads are significant, they need to be individually assessed. combining regular loads with extreme loads has been a major challenge, mainly because the extreme loads are time variables and cannot be directly combined with time invariant loads to formulate the probability of structural failure. To overcome these difficulties, this paper suggests a methodology of comprehensive reliability, by introducing the concept of partial failure probability to separate the loads so that each individual load combination under a certain condition can be approximated as time invariant. Based on these conditions, the extreme loads （also referred to as multiple hazard or MH loads） can be broken down into single effects. In Part II of this paper, a further breakdown of these conditional occurrence probabilities into pure conditions is discussed by using a live truck and earthquake loads on a bridge as an example. There are three major steps in establishing load factors from MH load distributions：（1） formulate the failure probabilities; （2） normalize various load distributions; and （3） establish design limit state equations. This paper describes the formulation of the failure probabilities of single and combined loads.

关键词： multiple hazards bridge probability-based design comprehensive reliability partial failure probability

Towards establishing practical multi-hazard bridge design limit states

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Earthquake Engineering and Engineering Vibration 2013年第3期12卷 333-340页

作者： Zach Liang george c.lee Department of Mechanical and Aerospace Engineering Unidersity at Buffalo Depart of civil Structural and Environmental Engineering University at Buffalo

In the U.S., the current Load and Resistance Factor Design （LRFD） Specifications for highway bridges is a reliability-based formulation that considers failure probabilities of bridge components due to the actions of typical dead load and frequent vehicular loads. Various extreme load effects, such as earthquake and vessel collision, are on the same reliability-based platform. Since these extreme loads are time variables, combining them with not considered frequent. non- extreme loads is a significant challenge. The number of design limit state equations based on these failure probabilities can be unrealistically large and unnecessary from the view point of practical applications. Based on the opinion of AASHTO State Bridge Engineers, many load combinations are insignificant in their states. This paper describes the formulation of a criterion to include only the necessary load combinations to establish the design limit states. This criterion is established by examining the total failure probabilities for all possible time-invariant and time varying load combinations and breaking them down into partial terms. Then, important load combinations can be readily determined quantitatively,

关键词： multi-hazards load and resistance factor design re.liability based bridge design specifications design limit state equations

On similitude law of sub-systems

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Earthquake Engineering and Engineering Vibration 2006年第1期5卷 133-142页

作者： Zach Liang george c.lee Department of civil Structural and Environmental Engineering University at BuffaloState University of New YorkBuffaloNew YorkUSA Multidisciplinary center for Earthquake Engineering Research University at BuffaloState University of New YorkBuffaloNew YorkUSA

Based on Buckingham＇s π-Theorem, dimensional analysis has achieved considerable success over the past near-century. Model testing has long been a powerful tool in both scientific studies and engineering applications. However, the prototype objects are becoming more and more complicated nowadays, and many of the prototype systems can contain several sub-systems. The conventional theories on model-prototype similarity and dimensional analysis have only limited application since the π-Theorem itself does not distinguish between the original system and subsystems. This is particularly true in the field of structural dynamics, where the structure is often modeled as a multi-degree-of-freedom system. In this paper, we attempt to show that, if a system can be decoupled into several nontrivial subsystems, then, in each subsystem, the number of π-terms will be reduced and therefore simplify the model testing. On the other hand, if a system cannot be decoupled into subsystems, then using model testing with reduced π-term analysis, both experimentally and theoretically, may introduce severe errors.

关键词： similitude law Buckingham's π-theorem model testing sub-systems

Principal axes of M-DOF structures Part I:Static loading

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Earthquake Engineering and Engineering Vibration 2002年第2期1卷 293-302页

作者： Zack Liang george c.lee Department of civil Structural and Environmental EngineeringUniversity.at BuffaloState University.of New YorkBuffaloNew YorkUSA Multidisciplinary center for Earthquake Engineering Research University at BuffaloState University of New YorkBuffaloNew YorkUSA

This paper is the first in a two-part series that discusses the principal axes of M-DOF structures subjected to static and dynamic loads. The primary purpose of this series is to understand the magnitude of the dynamic response of structures to enable better design of structures and control modification devices/systems. Under idealized design conditions, the structural responses are obtained by using single direction input ground motions in the direction of the intended control devices/systems, and by assuming that the responses of the structure is decoupleable in three mutually perpendicular directions. This standard practice has been applied to both new and retrofitted structures using various seismic protective systems. Very limited information is available on the effects of neglecting the impact of directional couplings (cross effects - of which torsion is a component) of the dynamic response of structures. In order to quantify such effects, it is necessary to examine the principal axes of structures under both static and dynamic loading. This first paper deals with quantitative definitions of principal axes and “cross effects” of three-dimensional structures under static load by using linear algebra. It shows theoretically that, for three-dimensional structures, such principal axes rarely exist. Under static loading conditions, the cross effect is typically small and negligible from the viewpoint of engineering applications. However, it provides the theoretical base for subsequent quantification of the response couplings under dynamic loads, which is reported in part II of this series.

关键词： principal axes of M-DOF structures structural response couplings cross effect theoretical base

cyclic performance and simplified pushover analyses of precast segmental concrete bridge columns with circular section

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Earthquake Engineering and Engineering Vibration 2016年第2期15卷 297-312页

作者： Bu Zhanyu Guo Jian Zheng Rongyue Song Jianwei george c.lee Faculty of Architectural Civil Engineering and Environment Ningbo University college of civil Engineering and Architecture Zhejiang University of Technology Department of civil Structural and Environmental Engineering University at Buffalo

In recent years, precast segmental concrete bridge columns became prevalent because of the benefits of accelerated construction, low environmental impact, high quality and low life cycle costs. The lack of a detailed configuration and appropriate design procedure to ensure a comparable performance with monolithic construction has impeded this structural system from being widely used in areas of high seismicity. In this study, precast segmental bridge column cyclic loading tests were conducted to investigate the performance of unbonded post-tensioned segmental bridge columns. One monolithic and two precast segmental columns were tested. The preeast segmental column exhibited minor damage and small residual displacement after the maximum 7% cyclic drift; energy dissipation （ED） can be enhanced byadding ED bars. The experimental results were modeled by a simplified pushover method （SPOM）, as well as a fiber model （FIBM） finite element method. Forty-five cases of columns with different aspect ratios, axial load ratios and ED bar ratios were analyzed with the SPOM and FIBM, respectively. Using these parametric results, a simplified design method was suggested by regressive analysis. Satisfactory correlation was found between the experimental results and the simplified design method for preeast segmental columns with different design parameters.

关键词： precast concrete segmental column simplified pushover fiber model

Highway bridge seismic design:summary of FHWA/McEER project on seismic vulnerability of new highway construction

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Earthquake Engineering and Engineering Vibration 2002年第1期1卷 10-19页

作者： Ian M.Friedland Ian G.Buckle george c.lee Applied Technology council 1300 Pennsylvania Ave NWSuite 700Washington D.C.20004USA Associate Director for Development Department of civil Engineering University of Nevada-RenoMail Stop 258RenoNevada89557USA Professor Multidisciplinary center for Earthquake Engineering Research.University at Buffalo.Red Jacket Quadrangle.Buffalo.New York 14260.USA Samuel P.Capen Professor

The Federal Highway Administration (FHWA) sponsored a large,multi-year project conducted by the Multidisciplinary center for Earthquake Engineering Research (McEER) titled'Seismic Vulnerability of New Highway construction'(McEER Project 112),which was completed in *** coordinated the work of many researchers,who performed studies on the seismic design and vulnerability analysis of highway bridges,tunnels,and retaining structures. Extensive research was conducted to provide revisions and improvements to current design and detailing approaches and national design specifications for highway *** program included both analytical and experimental studies,and addressed seismic hazard exposure and ground motion input for the *** system;foundation design and soil behavior: structural importance,analysis,and response:structural design issues and details;and structural design criteria.

关键词： Seismic design specifications bridges seismic hazard exposure ground motion input structural response analysis foundation design soil behavior

Dynamic responses under the excitation of pulse sequences

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Earthquake Engineering and Engineering Vibration 2004年第2期3卷 157-169页

作者：戴君武 Mai Tong george c.lee 齐霄斋白文婷 Institute of Engineering Mechanics China Earthquake Administration.Harbin 150080China Professor Multidisciplinary center for Earthquake Engineering Research University at BuffaloBuffaloNY14261USA Senior Research Scientist Multidisciplinary center for Earthquake Engineering Research University at BuffaloBuffaloNY14261USA Professor Institute of Engineering Mechanics China Earthquake Administration.Harbin 150080China Master student

This paper studies the dynamic responses of SDOF system under pulse-dominant *** purpose of the study is to prepare for scrutiny of some near-field pulse-dominantground motions and their potential to cause structural *** the single pulse dynamics,we consider the effect of pulse *** kind of excitation was particularly obvious in some of previous earthquakes such as Northridge (1994) and chi-chi (1995).Based on the duration, peak and rise and decay era of the main pulse as well as its relationship with the predecessor and successor pulses,we propose a classification for the pulse *** studies have been canied out for acceleration,velocity and displacement response spectra of the main pulse with either a predecessor or a successor *** analysis also includes general response behaviors in different fundamental period segments and special aspects of response at certain points (e.g.,the corresponding peak points).

关键词： pulse sequences near-field ground motions triangle pulse representation chi-chi earthquake response spectra

Force-based and displacement-based reliability assessment approaches for highway bridges under multiple hazard actions

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Journal of Traffic and Transportation Engineering(English Edition) 2015年第4期2卷 223-232页

作者： chao Huang Jerry J.Shen Mi Zhou george c.lee Department of civil Structural and Environmental Engineering University at Buffalo Genex Systems/TFHRc 6300 Georgetown Pike Mc Lean 22101 USA National Engineering and Research center for Highways in Mountain Area Key Laboratory for Old Bridge Detection and Reinforcement Technology of Ministry of Transportation Chang'an University

The strength limit state of American Association of State Highway and Transportation Officials （AASHTO） Load and Resistance Factor Design （LRFD） Bridge Design Spec/fications is developed based on the failure probabilities of the combination of non-extreme loads. The proposed design limit state equation （DLSE） has been fully calibrated for dead load and live load by using the reliability-based approach. On the other hand, most of DLSEs in other limit states, including the extreme events i and li, have not been developed and calibrated though taking certain probability-based concepts into account. This paper presents an assessment procedure of highway bridge reliabilities under the limit state of extreme event i, i. e,, the combination of dead load, live load and earthquake load. A force-based approach and a displacement-based approach are proposed and implemented on a set of nine simplL^ed bridge models. Results show that the displacement-based approach comes up with more convergent and accurate reliabilities for selected models, which can be applied to other hazards.

关键词： BridgeReliability assessmentMultiple hazardsLoadResistance

基于Ferry Borges理论的地震与重卡车作用下桥梁内力的组合问题

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地震工程与工程振动 2011年第6期31卷 18-23页

作者：孙得璋孙柏涛 george c.lee 中国地震局工程力学研究所黑龙江哈尔滨150080 纽约州立大学布法罗分校纽约14260

目前的AASHTO LRFD桥梁规范主要考虑重力荷载和卡车等活荷载的组合情况,而没有在概率基础上考虑地震等极端荷载的组合问题。包括LRFD在内的很多桥梁抗震规范都是主要考虑地震的作用,甚至设计时不考虑其他荷载的作用,LRFD设计指导手册中... 详细信息

目前的AASHTO LRFD桥梁规范主要考虑重力荷载和卡车等活荷载的组合情况,而没有在概率基础上考虑地震等极端荷载的组合问题。包括LRFD在内的很多桥梁抗震规范都是主要考虑地震的作用,甚至设计时不考虑其他荷载的作用,LRFD设计指导手册中在考虑地震等极端荷载时,也只是提到在特殊情况和桥梁比较长的情况下再考虑卡车的作用,而且,也比较模糊。文中在考虑地震荷载与卡车荷载时将其视为2种随机过程函数,并分析其各自的荷载特点。结合最近一些年USGS收集的极端荷载数据,文中认为桥梁设计(考虑地震和重卡车设计)时应该综合考虑地震和重卡车的影响,对它们进行荷载组合。接着,文中简单回顾了几种荷载组合方法,对比之后,认为FerryBorges(也称Ferry Borges-castanheta模型)模型考虑了荷载的持时因素与荷载发生概率,虽然也对荷载做了极大的简化,但很好地解释了随机过程转化成随机变量以及与其他随机变量组合的复杂问题。最后,本文以美国西雅图地区的一桥梁为研究对象进行了算例分析。

关键词： LRFD 极端荷载随机过程荷载组合地震与重卡车 Ferry Borges 桥梁设计