Seismic response of skewed RC box-girder bridges

It is critical to ensure the functionality of highway bridges after earthquakes to provide access to important facilities. Since the 1971 San Fernando earthquake, there has been a better understanding of the seismic performance of bridges. Nonetheless, there are no detailed guidelines addressing the performance of skewed highway bridges. Several parameters affect the response of skewed highway bridges under both service and seismic loads which makes their behavior complex. Therefore, there is a need for more research to study the effect of skew angle and other related factors on the performance of highway bridges. This paper examines the seismic performance of a three-span continuous concrete box girder bridge with skew angles from 0 to 60 degrees, analytically. Finite element （FE） and simplified beam-stick （BS） models of the bridge were developed using SAP2000. Different types of analysis were considered on both models such as： nonlinear static pushover, and linear and nonlinear time history analyses. A comparison was conducted between FE and BS, different skew angles, abutment support conditions, and time history and pushover analysis. It is shown that the BS model has the capability to capture the coupling due to skew and the significant modes for moderate skew angles. Boundary conditions and pushover load profile are determined to have a major effect on pushover analysis. Pushover analysis may be used to predict the maximum deformation and hinge formation adequately.     

Structural condition assessment of long-span suspension bridges using long-term monitoring data

<正>This paper focuses on developing an online structural condition assessment technique using long-term monitoring data measured by a structural health monitoring system.The seasonal correlations of frequency-temperature and beam-end displacement-temperature for the Runyang Suspension Bridge are performed,first.Then,a statistical modeling technique using a six-order polynomial is further applied to formulate the correlations of frequency-temperature and displacement-temperature,from which abnormal changes of measured frequencies and displacements are detected using the mean value control chart.Analysis results show that modal frequencies of higher vibration modes and displacements have remarkable seasonal correlations with the environmental temperature and the proposed method exhibits a good capability for detecting the micro damage-induced changes of modal frequencies and displacements.The results demonstrate that the proposed method can effectively eliminate temperature complications from frequency and displacement time series and is well suited for online condition monitoring of long-span suspension bridges.     

高墩梁桥地震响应分析

本文将对两座高墩桥梁的地震响应进行分析,一座是连续-刚构组合梁桥,另一座是刚构桥。这两种是高墩桥梁普遍采用的桥型,对其进行详细的动力分析对此类桥梁的抗震设计具有一定的指导作用。针对这两种桥梁结构,本文首先分析直接影响结构动力响应的自振特性,从中总结高墩桥梁的特点,然后采用反应谱法、时程分析法分析结构地震响应,并对其结果进行比较,同时讨论桩-土相互作用对高墩桥梁地震响应的影响。     

结构参数对双链式悬索桥地震响应的影响

以某双链式悬索桥为工程背景,建立了空间有限元计算模型.运用几何非线性时程分析方法,分析并探讨了不同垂跨比、阻尼比,塔桥不同连接方式和双链位置对双链式悬索桥地震响应的影响.分析表明,竖向地震动分量使桥塔轴力迅速增大,加劲梁采用钢筋混凝土边梁可有效减小地震响应;塔梁间采用简支连接方案其抗震性能比固定支座连接方案、滑动支座连接方案要好;双链式悬索桥横向抗震性能优于单链式悬索桥.对双链式悬索桥抗震性能的研究,为此类悬索结构的设计选型,乃至减震、隔震及抗震加固提供了参考.     

高烈度区连续梁桥的减震设计方法研究

本文以高烈度区的某三跨连续梁桥为例，分别采用基础隔震和消能减震两种措施进行结构的减震分析；针对隔震结构减震效果好但主梁位移过大的特点，提出了在采用铅芯橡胶隔震支座的同时设置粘滞阻尼器的减震方案，其非线性时程分析结果表明，该方案能有效地降低结构的地震反应，可供工程实践参考。     

长春光大银行主体钢结构在罕遇地震作用下的时程反应分析

分别采用基于塑性铰法的空间梁柱单元分析程序和简化的DRAIN-20分析程序,对其主体巨型钢框架结构进行了考虑双重非线性的罕遇地震作用下的时程反应分析。分析中使用了三条典型地震波和一条当地人工地震波,分别得到了顶层位移和加速度时程曲线、层间位移包络值和塑性铰出现的位置与先后顺序。分析结果表明结构在体系设计上是合理的和在大震作用下具有足够的安全度。     

独塔自锚式悬索桥纵向设置黏滞阻尼器参数分析

以鼓山大桥为工程背景,研究黏滞阻尼器对该桥抗震性能的影响。利用非线性动力时程分析的方法讨论了黏滞阻尼器参数C及ξ的不同组合对该桥塔底、墩底、梁端及塔顶等关键部分内力及变形的影响规律。综合考虑桥梁结构各个关键部位的反应情况,得出该桥的拟安装阻尼器的最优参数约为C=1500kN／（m&#183;s）^0.3,ξ=0．30左右。分析结果表明：在纵桥向设置适当参数的阻尼器可有效减小纵桥向位移的同时改善关键构件受力。     

澳门澳凼第三大桥斜拉桥地震反应分析

结合一座澳门澳凼第三大桥斜拉桥的工程设计实例,采用大型有限元分析程序ANSYS,选取空间BEAM188、BEAM4及SHELL63单元建立动力计算模型,对比研究了主塔墩底在假定固结和考虑桩土共同工作这两种边界约束处理方式下的动力特性;并选取三条地震波在桥的纵、横向分别进行桥梁地震作用下的时程分析,给出了主梁和中塔的内力、位移及时程响应。     

军山斜拉桥非线性时域抖振分析

武汉军山大桥是跨越长江的中跨跨径很大的斜拉桥,在脉动风作用下,其线性抖振响应较大,动力放大系数基本上大于2.为了比较该桥非线性抖振响应与线性抖振响应的差别,本文根据某地短期的实际风速时程记录资料,在一定的概率下,对该地区100年一遇的极值风速时程进行抖振分析比较.计算结果表明,对于该桥说来非线性影响不是很明显.     

大型双槽渡槽地震反应分析

为了得到比较精确的大型双槽渡槽结构的地震反应,根据渡槽结构复杂、影响动力因素较多等特点,采用8结点空间块体单元对渡槽槽身和槽墩进行有限元离散,分别用耦合自由度和多个弹簧单元分别模拟渡槽槽身横向拉杆、加劲肋和盆式橡胶支座,建立了大型双槽渡槽结构地层反应分析的有限元模型,计算了南水北调水利工程中的双洎河大型双槽渡槽的振动特性,并分别用反应谱法和时程分析法对该渡槽进行了地震反应分析,计算结果可为该渡槽的抗震设计提供参考。     

油气集输悬索管桥动特性及地震非线性时程反应分析

悬索管桥具有比传统悬索路桥柔性大、阻尼低、频谱不均匀、自重轻、横向刚度小等的典型特性,动力学行为复杂,更容易引起结构失效和破坏。文中以漾濞江油气集输悬索管桥为研究对象,基于Midas软件建立了地震载荷条件下的悬索管桥有限元模型,开展了悬索管桥的地震响应、抗震性能数值模拟研究,揭示了管桥体系的危险区域和可能存在的破坏形式,发现：合理设置吊杆和拉索分布密度,对悬索桥自身的抗震有利。根据相似原理,搭建了漾濞江悬索管桥的室内实验系统,探究悬索桥动力特性及结构参数对动力特性的影响规律,验证了数值模拟正确性,为漾濞江油气集输悬索管桥的抗震性能设计提供理论指导。     

Probabilistic seismic response and reliability assessment of isolated bridges

Bridge seismic isolation strategy is based on the reduction of shear forces transmitted from the superstructure to the piers by two means: shifting natural period and earthquake input energy reduction by dissipation concentrated in protection devices. In this paper, a stochastic analysis of a simple isolated bridge model for different bridge and device parameters is conducted to assess the efficiency of this seismic protection strategy. To achieve this aim, a simple nonlinear softening constitutive law is adopted to model a wide range of isolation devices, characterized by only three essential mechanical parameters. As a consequence of the random nature of seismic motion, a probabilistic analysis is carried out and the time modulated Kanai-Tajimi stochastic process is adopted to represent the seismic action. The response covariance in the state space is obtained by solving the Lyapunov equation for a stochastic linearized system. After a sensitivity analysis, the failure probability referred to extreme displacement and the mean value of dissipated energy are assessed by using the introduced stochastic indices of seismic bridge protection efficiency. A parametric analysis for protective devices with different mechanical parameters is developed for a proper selection of parameters of isolation devices under different situations.     

大型渡槽结构非线性地震响应分析

运用渡槽薄壁结构弹塑性动力分析模型,开展了渡槽非线性地震响应分析计算。该渡槽薄壁结构弹塑性动力分析模型集渡槽薄壁结构线弹性模型和非线性多弹簧模型为一体,应用多弹簧等效关系模拟结构塑性铰区的非线性滞回特性。经结构线弹性和非线性地震响应比较,结果表明两者存在差异,开展大型渡槽结构非线性地震响应分析是很有必要的。     

多年冻土区桥梁的地震反应

首先研究了冻土区桥梁的抗震计算方法,对波动法和惯性力法的计算结果进行厂对比分析。对比结果表明惯性力法的计算结果偏大,但当基岩的剪切波速很大时,两种方法的结果接近。然后,采用波动法对季节性冻土区和多年冻土区桥梁结构进行了地震反应分析,研究了冻土层的变化对桥梁结构地震反应的影响,得到了不同冻土厚度、不同墩高时桥墩地震内力分布的规律。计算结果表明,冻土层的存在对桥梁的地震反应具有显著影响,桥墩的地震反应在冬夏两季具有显著区别。     

多点激励下大跨度斜拉桥地震反应分析

大跨斜拉桥是交通运输的枢纽工程,一旦在地震中遭到破坏,将会造成巨大的直接和间接经济损失.由于大跨斜拉桥的跨度大,在地震中地震波到达不同桥墩的时间存在差异,这会对大跨斜拉桥的地震反应产生很大影响.因此,对大跨斜拉桥在多点输入下的反应开展研究,对进行正确有效的抗震设计,确保其抗震安全性具有非常重要的意义.本文分析了多点激励下大跨度斜拉桥的地震反应,并与一致激励下大跨度斜拉桥的地震反应进行了对比,研究了多点激励对大跨度斜拉桥地震反应的影响.     

Earthquake performance assessment and retrofit investigations of two suspension bridges in Istanbul

This paper presents the results from earthquake performance assessment and retrofit investigations for Fatih Sultan Mehmet and Bosporus suspension bridges, with main span lengths of 1090 and 1074 m in Istanbul. In the first part of the study, sophisticated three-dimensional finite element model of two suspension bridges were developed and the results of the free vibration analysis were presented. The models contain detailed structural components of the bridges and geometric non-linearity with cable sagging and stress stiffening, cumber of the deck and set-back of the towers. These components affect the natural frequencies and the corresponding mode shapes of the bridges. In the second part of the study, the seismic performance evaluation of two suspension bridges was undertaken. For performance assessments, non-linear 3-D finite-element time history analysis of with multi-support scenario earthquake excitation was used. Displacements and stresses at critical points of the bridges were investigated. Their earthquake performance under the action of scenario earthquake (site-specific ground motion that would result from the Mw=7.5 scenario earthquake on the Main Marmara Fault) were estimated and comparison with actual design data were also presented. Although both suspension bridges were originally designed for much lower earthquake loads they exhibited satisfactory performance. Finally, suggestions for retrofit need were made and retrofit design with hysteretic dampers for the Bosporus suspension bridge was calculated.     

钢-混凝土叠合梁自锚式悬索桥动力特性测试分析

针对钢-混凝土叠合梁自锚式悬索桥的结构特点,在总结以往大跨径桥梁有限元模型的基础上,采用组合有限元法以梁、板、杆、索单元建立邵阳市桂花大桥三维有限元模型,计算分析获得结构的主要频率和振型。通过现场测试获得大桥环境激励和行车激励作用下的响应时程,分析得到结构的主要频率、振型和阻尼比,引入模态置信因子对计算模态信息和实测模态信息进行比较分析,以验证数值模型和实测结果的准确性。研究结果可为全面了解钢-混凝土叠合梁自锚式悬索桥的动力特性、准确预测结构的动力响应以及类似桥梁的抗震、抗风设计提供重要依据。     

长联大跨摩擦摆支座隔震连续梁桥多维地震反应分析

结合长联大跨连续梁桥的特点,以1座(65+123+156+123+10×90+55)m长联大跨摩擦摆支座隔震连续梁桥为背景,建立了全桥三维有限元模型,运用非线性时程分析法,分析了地震动输入模式、地震动强度、摩擦摆支座参数对该桥内力、位移和能量响应的影响。研究结果表明:(1)长联大跨连续梁桥布置摩擦摆支座,可有效延滞固定墩顶有效主梁质量效应,实现全桥协同抗震。大部分地震能量可通过支座滞回耗能散耗,大幅降低了该桥固定墩地震能量耗散需求。(2)长联大跨连续梁桥减隔震设计中,建议采用水平单向+竖向地震组合进行内力设计,采用三向地震组合进行位移设计。(3)强震作用下,支座摩擦因数取0.029~0.034时该桥隔震性能最优。     

城市独柱墩桥梁结构体系非线性抗震研究

针对城市桥梁采用的独柱墩连续梁桥具有的缺点,提出了采用两跨T形刚构桥梁的结构形式。利用非线性时程分析方法,考虑钢筋混凝土桥墩材料的非线性,对两种桥梁结构在纵向地震动作用下的非线性地震反应行为进行了分析,得到了两种桥梁结构桥墩的弯矩、剪力、位移以及塑性铰转角时程。结果表明,在同一地震动作用下,T形刚构桥墩所受弯矩小于连续梁,所受剪力大于连续梁,桥墩塑性铰的转角远小于连续梁。因此,在同等损伤程度和保证桥墩抗剪能力的情况下,T形刚构比连续梁能够承受更强的地震。     

多维地震输入下曲线匝道桥梁伸缩缝碰撞响应

针对曲线匝道桥梁伸缩缝地震碰撞破坏现象,依托某市多层互通式立交体系中一座独立、单支、多联、曲线、箱梁匝道桥,用Kelvin接触单元模拟了伸缩缝处地震和碰撞效应,建立了全桥空间动力分析模型。利用非线性时程分析法,分别输入单维(X方向、Y方向)和多维共8种地震动工况,分析了曲线匝道桥梁伸缩缝的地震碰撞响应差异。结果表明:曲线匝道桥梁由于曲率的影响,不同方向地震动响应存在耦合效应,其伸缩缝碰撞响应的最不利值应考虑多维地震输入工况,并用碰撞力和碰撞位移双指标控制伸缩缝的地震碰撞响应。