斜交角对公路连续斜交梁桥地震反应的影响分析

以标准跨径的两跨公路连续混凝土斜交桥为研究对象,建立动力有限元计算模型,分别进行了常遇地震影响下的反应谱分析和罕遇地震影响下的非线性时程分析,探讨了斜交角变化对连续斜交桥地震反应的影响,并得到了影响规律。     

超长联大跨度连续梁桥地震响应与阻尼器布置

联长超过千米级的大跨度连续梁桥目前修建数量不多。由于上部结构体量大,为降低混凝土收缩徐变等因素下的结构次内力,联内顺桥向通常仅设置一个制动墩,导致地震时该墩效应显著,难以满足抗震要求。在采用阻尼器降低地震效应的前提下,以吉利黄河特大桥在纵横向地震下作地震响应分析,采用时程分析法,研究阻尼器设置以及阻尼器不同布置方案下的地震效应和减震效果。结果表明,单独的纵向阻尼器设置较难适应超长联桥梁的抗震要求;联合横、纵双向合理布设阻尼装置可显著提高超长联结构的抗震性能。最后,探讨超长联连续梁桥阻尼器布置特点和位置优化。     

以位移为基础的连续梁桥抗震设计

以4跨连续直桥为背景,在地震作用下,其横桥向的弹塑性位移需求和弹性位移需求分别由非线性时程分析方法和弹性反应谱分析方法计算得到;然后采用参数统计分析方法对弹塑性位移需求和弹性位移需求的比值进行了研究。结果表明,对于主要振型周期相对较长的桥梁,其弹塑性位移需求与弹性位移需求接近,可采用相对简单的弹性分析方法(如弹性反应谱分析)得到的位移需求,近似代表地震作用下结构的弹塑性位移需求,进而简化了连续梁桥基于位移的抗震设计。     

地震作用下城市高架连续梁桥碰撞单元刚度参数分析

本文基于Kelvin碰撞单元建立3联城市高架连续梁桥地震碰撞分析模型,采用非线性时程方法对碰撞单元刚度的取值进行了参数分析。分析结果表明:当碰撞单元刚度较小时,相邻梁体间的碰撞力受碰撞单元刚度影响较大,单元刚度取值对于相邻联梁体最大相对位移影响不大;而当碰撞单元刚度大于1联梁体的2倍轴向刚度时,碰撞力和位移的计算结果随碰撞单元刚度的增加变化不超过10%。     

扩建改造混凝土连续梁桥结构地震响应特性分析

随着扩建改造桥梁的逐渐增多及地震对桥梁结构危害严重性的增加,扩建改造桥梁的抗震性能越来越引起人们的关注。以京沪高速上的新徐海公路分离式立交桥为依托工程,分别对主梁连接、盖梁分离和主梁、盖梁都连接两种扩建方式桥梁的地震响应进行对比分析。结果表明:扩建改造后桥梁的自振周期略小于原桥,并伴随比原桥明显的主梁扭转;地震反应总体上小于原桥,并且主盖梁均连接的方案基本小于只有主梁连接的方案,更能降低地震反应;扩建改造后桥梁横向地震反应相对较复杂,并且不同的扩建改造方案对支座的影响比对桥墩的影响要小;扩建改造部分桥梁对原桥的影响程度与原桥本身的结构形式及连接方式具有较大的关系。     

三跨简支斜交桥地震响应分析

以某三跨简支斜交小箱梁桥为工程背景,采用梁格法建立模型,用反应谱法分析研究斜度和地震输入角度对结构地震响应的影响,对斜交桥的设计具有一定的指导意义。     

多跨长联连续梁桥考虑行波和碰撞效应的位移响应研究

为了揭示在行波效应作用下伸缩缝处的碰撞现象对多跨长联连续梁桥纵向地震位移响应的影响,以某7跨长联连续桥为工程背景,采用SAP2000建立非线性分析模型,按绝对位移法模拟行波效应,按接触单元法模拟碰撞效应,对背景桥例进行了关键参数对比分析,并针对性地提出了抗震策略,开展了减碰效果分析.研究表明:行波效应会大幅增大主、引桥...     

连续梁桥基于位移的抗震设计

在强震作用下,结构的位移比力更能直接反映结构的破坏状态。因此近年来,基于位移的抗震设计方法受到越来越多的重视与发展。该设计方法要求把多自由度结构转换为等效的单自由度模型(包括等效的刚度、等效阻尼及等效延性等)才能进行抗震设计。本文以连续梁桥为例,基于所建议的位移形状函数,推导了位移形状函数与桥梁跨度及刚度(墩高)的关系;在此基础上,提出了多自由度连续梁桥的等效单自由度模型,并以对称和不对称的连续梁桥为例,分别给出了基于位移的抗震设计步骤。由于设计步骤中考虑了塑性铰的屈服机制,可以看出对此两种结构其设计步骤本质上是相同的,且不需要迭代。     

连续梁桥合龙顺序仿真研究

以某连续梁桥为例,建立了有限元模型,分析了三种合龙顺序下桥梁的内力,对三种合龙顺序下各施工阶段内力进行了对比,并且探讨了不同合龙顺序对主梁线型的影响,确定了先边跨后中跨为最佳合龙顺序,为连续梁桥提供施工和监控的参考价值。     

行波激励下多跨连续梁桥地震反应分析

多跨连续梁桥纵向延伸长度比较长,进行地震反应分析时应考虑地震波有限波速传播所引起的行波效应.以某长江大桥南引桥为例,推导了行波输入时结构的运动方程,并对其进行行波激励下地震反应的数值模拟,将结果与一致激励的结果比较,分析行波效应对于此类桥梁影响的规律性以及影响行波效应的因素.     

高墩连续梁桥抗震性能优化

在分析某高墩连续梁桥常规约束体系抗震性能的基础上,探讨了优化该连续梁桥抗震性能的设计方案,提出了板式橡胶支座、滑板支座加纵横向限位器的结构约束体系,显著提升了桥梁结构的抗震性能。     

Influence of ground motion characteristics on seismic response of skewed bridges

Skewed bridges are bridges with longitudinal axes at an angle to the abutments. They are more susceptible to damage during seismic events due to in-plane rotations of the girders induced, especially when pounding occurs. Most current design standards do not consider many factors that could significantly affect the response of skewed bridges, such as the skew angle and effect of the supporting soil. A bridge-abutment model with 0°, 30°, and 45° skew angles were subjected to shake table tests. Ground motions were simulated based on the New Zealand design spectra for Class C and E soil conditions. The effects of the different characteristics of ground motions on the seismic response of skewed bridges considering presence of pounding and the supporting soil were investigated. The results were also used to evaluate the recommendation of girder seat lengths specified in design specifications, e.g. the New Zealand Transport Agency (NZTA) Bridge Manual. It was found that the NZTA recommendation for seat length could potentially significantly underestimate the out-of-plane movements of the girders. In the worst case, the displacement of the skewed bridge was up to 3.48 times that of the straight bridge – much larger than the recommended value of 1.25 times.     

考虑行波效应的大跨度连续刚构桥地震响应分析

为研究大跨度连续刚构桥地震响应特性,基于考虑行波效应的多点激励时程分析方法,以涪江三桥为研究对象,应用ANSYS有限元软件对其进行了地震响应分析,并与一致地震激励下的计算结果进行了比较。研究结果表明,行波效应对该类连续刚构桥桥墩的抗震设计是有利的,对主梁则会产生不利影响。     

大跨度斜拉桥的地震响应分析

以某大跨度斜拉桥为背景,利用大型通用有限元分析软件ANSYS建立了计算仿真模型,采用分块Lanczos法得到了该斜拉桥结构的自振特性。在频域地震作用下,分别采用反应谱法和动力时程分析法对该斜拉桥在纵+竖向、横+竖向、纵+横+竖向激励作用下的地震响应进行了对比分析。分析结果表明:纵向地震激励对结构响应影响较为明显;由反应谱法计算得出的结果较动力时程分析法偏大,在弹性阶段反应谱分析结果是比较保守安全的。     

邻梁碰撞对隔震连续梁桥地震反应的影响

采用非线性时程分析方法,模拟了粤东高烈度地区两联隔震连续梁桥结构地震动反应,并通过接触单元法Kelvin模型模拟邻梁的碰撞效应,探讨了邻梁碰撞对隔震连续梁桥地震反应的影响,结果表明:地震作用下,主梁过大的相对位移导致了邻梁间的多次碰撞且碰撞力非常大,可能引起梁端的局部破坏;碰撞减小了主梁的位移,但幅度不大,明显减小了邻梁间的相对位移;碰撞作用增大了右联连续梁桥中间墩的地震反应,减小了其他墩的地震反应。     

公路隧道地震响应下的位移分析

对宝天高速公路段甘泉隧道进行了地震响应分析，通过动力有限元方法确定了公路隧道的残余变形量，将各个时刻重复通过计算所确定的残余位移累加得到了地震作用后公路隧道的永久变形量，通过分析永久变形量确定了公路隧道地震响应稳定性。     

斜交T梁桥受力性能分析

斜交梁桥和常规正交梁桥的结构有所差异,在斜交支承条件下,斜交T梁桥结构特殊的受力性表现为:由于弯扭耦合作用,在两端支座处有较大的负弯矩产生,而且支座处的支承反力分布不均。为了研究斜交T梁桥的受力特性,采用Midas civil2015有限元软件进行模拟,分析了在不同斜交角和宽跨比影响下正交与斜交T梁桥的受力性能。结果表明:随着斜交角和宽跨比的改变,斜交T梁桥的受力特性逐渐发生改变,即斜交T梁的最大弯矩随着斜交角和宽跨比的增大往钝角方逐渐偏移,且当斜交角为60°时弯矩偏移最大;梁端钝角处的支反力随着斜交角度的增大而增大,相对0°时最大增加10%,梁端锐角处产生的支反力随着交角的增大而减小,相对0°时最大减小9%。研究成果可为斜交T梁桥的设计提供参考。     

Seismic response analysis of skew bridges with pounding deck-abutment joints

In this paper the seismic response of short skew bridges with deck-abutment pounding joints is revisited. The permanent deck rotations and transverse displacements of such bridges after the recent earthquake in Chile created an incentive to revisit their non-conventional behaviour. A novel non-smooth rigid body approach is proposed to analyze the seismic response of pounding skew bridges which involves oblique frictional multi-contact phenomena. The coupling of the response, due to contact, is analysed in depth. It is shown that the tendency of skew bridges to exhibit transverse displacements and/or rotate (and hence unseat) after deck-abutment collisions is not a factor of the skew angle alone, but rather of the plan geometry plus friction. This is expressed with proposed dimensionless criteria. The study also unveils that the coupling is more pronounced in the low range of the frequency spectrum (short-period excitations/flexible structures) and presents novel dimensionless response spectra for the transverse displacements and rotations, triggered by oblique contact in a skew bridge subsystem. Despite the complexity of the response, the proposed spectra highlight a clear pattern. The dimensionless rotations, arising from contact, decline as the ratio of the structural versus excitation frequency increases and become practically negligible in the upper range of the frequency spectrum. Finally, a pilot application to a typical skew bridge is presented.     

Seismic fragility analysis of reinforced concrete continuous span bridges with irregular configuration

A set of fragility curves of a class of reinforced concrete bridges with different degrees of irregularity has been generated. Eighteen bridge configurations have been identified, from regular to so-called highly irregular models. The geometric irregularity in this class of bridges is assumed to vary with the height of the piers. Using non-linear analytical models and an appropriate suite of 60 ground motions, analytical fragility curves have been generated for the individual piers of each of these 18 bridge models. Discussions have been made about the imposition of the displacement ductility demand of the piers versus the earthquake intensity as well as the bridge regularity. Comparison of the fragility curves shows that the most vulnerable bridges are the irregular bridges and high damage probability is expected for the short piers of this class of bridges. It was found that the fragility curves may be used for categorisation of regular and irregular bridges.     

Fragility of skewed bridges under orthogonal seismic ground motions

The paper evaluates seismic fragility characteristics of skewed bridges under simultaneous action of orthogonal ground motion components. The effect of skew angle on bridge seismic fragility characteristics is investigated through nonlinear time-history analyses of Painter Street Overpass, a 38.5° skewed bridge located in Rio Dell, CA, and six representative bridges with skew angles varying between 0° and 50°. Ground motion incident angle is varied from 0° to 180° to investigate the effect of the direction of ground motion incidence on bridge seismic performance. Bridge seismic response is used to generate fragility curves and contours plots that quantify the sensitivity of bridge fragility characteristics on skew angle and incident angle. For any value of incident angle, bridge seismic vulnerability increases with an increase in skew angle; however, no such general trend is found to describe the effect of incident angle on bridge fragility characteristics. Results show that the variation of maximum rotation of bridge columns for an earthquake does not follow any particular trend with the change in skew angle and incident angle. Analysis-based fragility curves are further compared with empirical fragility curves generated using real-life seismic damage data of skewed bridges and a reasonable agreement is observed between these two.