机车动荷载作用下多年冻土区铁路路基动力响应的试验研究

青藏铁路穿越多年冻土区因地温和含冰量的不同而采取了不同的路基结构形式,以减小或避免气温和工程扰动对其下部多年冻土的影响。为了把握多年列车振动荷载作用下多年冻土区不同结构路基的动力响应特征,对青藏铁路北麓河段典型结构路基进行了实时强震动测试,得到了多年冻土区铁路路基的振动加速度衰减规律,对于研究机车动荷载对青藏铁路多年冻土区路基变形的定量影响规律,保障青藏铁路安全运营具有重要的科学意义。     

曲线箱梁桥的动力特性参数分析

结合某城市一座立交工程匝道高架曲线箱梁桥的工程实例,采用大型有限元分析程序ANSYS,选取空间梁单元建立动力计算模型,研究了在跨度相同的条件下,曲率半径与角度比值对曲线梁桥动力特性和地震反应的影响.分析结果表明:曲率半径与角度比值是影响动力特性的一个重要参数.且对曲线梁桥的切向刚度、径向刚度和地震反应有较大的影响.     

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。     

Effect of vehicle bridge interaction on seismic response and fragility of bridges

This study focuses on understanding and evaluating the effect of vehicle bridge interaction (VBI) on the response and fragility of bridges subjected to earthquakes. A comprehensive study on the effect of VBI on bridge seismic performance is conducted, providing metamodels for seismic response and fragility estimates for bridges in the presence of various types of vehicles. For this purpose, the performance of multispan simply supported concrete girder bridges with varying design and geometric parameters is assessed with 3 different types of stationary trucks placed atop them. To delineate the effects of VBI and additional truck mass, the trucks are modeled in 2 different ways—with additional masses and suspension springs (ie, with VBI) and using additional masses only (without VBI). The results provide insight on VBI effects, such as the fact that when bridge and vehicle mode shapes are in‐phase, the component responses increase and vice versa; additionally, the presence of a heavy axle near a bent increases component responses. Sensitivity analyses are also performed to determine the bridge parameters that significantly alter the component responses in the presence of vehicles. Furthermore, differences in component responses and fragilities highlight that modeling vehicles with additional masses alone is not sufficient to model the effect of truck presence on the seismic response of bridges. Finally, this study concludes that depending on the characteristics of the bridge and the vehicle, presence of a vehicle atop the bridge during an earthquake may be either beneficial or detrimental to bridge performance.     

大跨度斜拉管线桥地震反应分析

首先利用Newmark-β法和修正的Newton-Raphson法，提出并推导了一种求解几何非线性地震反应方程的方法。利用该方法对大跨度斜拉管线桥进行了线性和非线性地震响应分析。通过结果比较，得出一些有意义的结论：几何非线性效应对斜拉管线桥的地震反应分析影响很大，在分析中不能忽略，尤其是恒载初始内力。     

曲线桥地震响应分析

曲线桥是现代交通中的一种重要桥型。与直线桥相比,曲线桥的自由振动与地震响应有着其自身的特点。文中运用有限元法,对曲线桥与直线桥的自振特性与地震响应作了对比分析。分析结果表明,曲线桥的以扭转为主的自振频率比直线桥高。在地震作用下,曲线桥上部结构的内力与直线桥相差不大;曲线桥竖向支座反力比直线桥小;曲线桥水平支座剪力比直线桥大。因此,在对曲线桥进行抗震设计时,上部结构可按直线桥进行设计,但应该准确计算其水平支座反力,并采取适当的支座抗剪措施。     

考虑竖向地震作用的拱式廊桥的地震响应分析

本文以某大型商业拱式廊桥工程实例为依托,利用有限元软件分别建立了整桥模型和不考虑上部建筑结构的桥梁模型以及不考虑下部桥梁结构的建筑模型,并计算了各自的自振动力特性,在此基础上通过反应谱方法分析了同时考虑水平地震作用和竖向地震作用的廊桥主拱圈和上部建筑结构柱的地震响应以及不同模型计算结果的差异,以此研究桥梁结构与建筑结构的耦合作用,为廊桥的抗震设计或分析提供一定的参考依据。     

基础非线性对桥墩地震反应的影响

在桩基础桥墩滞回特性的模型试验基础上,提出了用Clough模型模拟基础(地基)的恢复力特性。桥墩采用Takeda恢复力模型。用强震记录与人工合成地震动作为输入对铁路简支梁桥进行了非线性地震反应分析,讨论了不同地震动输入及不同地震强度时基础非线性对桥梁地震反应的影响。研究结果表明,考虑基础的非线性一般会使墩顶位移增大,而墩底的曲率明显减小,且随着地震动强度的增加,基础的非线性影响更加明显。     

淳安南浦大桥抗震性能研究

浙江淳安南浦大桥跨径大(308m),宽跨比小(1／19．81),该桥的面外刚度小于面内刚度。采用反应谱方法对该桥进行抗震性能的分析,结果表明该桥在地震荷载作用下的结构内力大于车辆荷载作用下的内力。     

哪吒大桥地震响应分析

建立了哪吒大桥———钢桁加劲梁悬索桥的三维有限元计算模型,对该桥进行了振动特性和地震响应研究,对比分析了一致激励下和考虑局部场地效应、行波效应非一致激励下的桥梁地震时程响应的差异。计算结果表明,由于悬索桥的钢桁加劲梁采用半飘浮体系,纵向约束较弱,桥梁第1阶振型为钢桁加劲梁的纵飘;各阶振型的频率呈现出密集分布的形态;考虑地震波传播速度产生的行波效应的影响,桥梁的地震响应与一致激励下的地震响应有一定差异;局部场地效应对哪吒大桥的地震响应影响较大,特别是对大缆应力及结构变形影响很大;哪吒大桥在7度设防(地震波峰值加速度不超过0.15g)时,大桥的抗震安全性是可以得到保证的。     

大跨度斜拉桥地震响应非线性时程分析

以有限元分析理论为基础,结合某大跨度斜拉桥工程实例,利用ANSYS软件建立有限元模型,通过修正后的El Centro波分别考虑横向、竖向及纵向输入,采用时程分析方法对其进行地震反应分析.计算分析表明:考虑几何非线性后,结构的内力和位移响应明显增大,且对主梁和索塔内力与位移的影响程度及规律也不尽相同,须区别对待分析.同时表明该桥抗震性能良好,地震荷载不控制设计.由此得出结论,对于斜拉桥这类柔性体系, 不可忽视结构几何非线性的影响.     

飘浮体系斜拉桥纵向抗震计算的单塔模型

通过全桥模型计算结果与单塔模型计算结果的对比,讨论了集中质量在塔上锚固区处堆聚位置,定义了一个结构动力特性和结构地震反应的修正系数,提出了飘浮体系斜拉桥塔纵桥向地震反应计算的单塔模型。多个工程实例的分析结果表明,采用单塔模型的典型误差在15%左右,精度可以满足工程抗震设计的要求,使桥塔的抗震计算得到简化。     

钢管拱桥在大地震作用下的非线性反应分析

钢管拱肋填充混凝土后，质量体系相对刚度体系的作用将大幅增加，特别是在大地震作用下的横向反应显著增大。拱肋内部不填充混凝土，能够减小横向地震作用，同时可以减轻下部结构的负担。因此，本文提出了圆形钢管拱肋的材料非线性性能的评价方法，并以上承式钢管拱桥为例，探讨了钢管拱桥在大地震作用下的非线性反应性能。     

设置负刚度装置的大跨长联连续梁桥地震反应分析

为完善大跨长联连续梁桥的减震和隔震技术,提出将负刚度装置引入某带有摩擦摆支座隔震的大跨长联连续梁桥中组成新型减震和隔震系统。基于CSIBridge软件建立全桥有限元模型,负刚度装置采用弹性多段线模拟,摩擦摆支座采用双线性恢复力模型,输入7条地震波进行了非线性时程分析,考查了新型减震和隔震系统下桥梁结构的地震反应,探究了负刚度系统对大跨长联隔震连续梁桥地震反应的影响。研究结果表明：在大跨长联隔震连续梁桥上布置负刚度装置后,梁体加速度及支座位移可被有效降低,近场地震动下的墩底内力也有明显减小。负刚度装置可有效提高大跨长联摩擦摆支座连续梁桥的抗震性能,负刚度装置也适用于大跨长联隔震连续梁桥。     

大跨度连续刚架-拱组合结构桥梁的纵向地震响应研究

以广州新光大桥为例，建立了空间杆系模型，利用动态时程分析方法，详细分析了大跨度连续刚架-拱组合结构桥梁在纵桥向地震一致激励和行波效应作用下的地震响应。研究表明除边墩外，行波效应对拱肋上、下弦杆以及V型刚架斜腿地震内力响应均有较大影响；随着剪切波速的增加主拱顶相对拱脚的最大纵向位移呈递减趋势，而边拱顶相对拱脚的最大纵向位移基本不受剪切波速的影响。     

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。     

Seismic response of a cable‐stayed bridge deck under multi‐component non‐stationary random ground motion

A Markov method of analysis is presented for obtaining the seismic response of cable‐stayed bridges to non‐stationary random ground motion. A uniformly modulated non‐stationary model of the random ground motion is assumed which is specified by the evolutionary r.m.s. ground acceleration. Both vertical and horizontal components of the motion are considered to act simultaneously at the bridge supports. The analysis duly takes into account the angle of incidence of the earthquake, the spatial correlation of ground motion and the quasi‐static excitation. A cable‐stayed bridge is analysed under a set of parametric variations in order to study the non‐stationary response of the bridge. The results of the numerical study indicate that (i) frequency domain spectral analysis with peak r.m.s. acceleration as input could provide more r.m.s. response than the peak r.m.s. response obtained by the non‐stationary analysis; (ii) the longitudinal component of the ground motion significantly influences the vertical vibration of the bridge; and (iii) the angle of incidence of the earthquake has considerable influence on the deck response. Copyright © 2003 John Wiley & Sons, Ltd.     

Effect of stiffness variability on the response of isolated structures

Results are presented of an investigation, the objective of which was to determine the relationship between the stiffness variability of the bearings of an isolation system and the response variability of the structure. The system is modeled as a rigid, rectangular structure that is free to translate and rotate. The isolation system consists of N isolation bearings arranged in a rectangular pattern, each with a stiffness k_i that is an independent, normally distributed, random variable. Response spectrum analysis is used to obtain the analytical solution for the structure response. Approximate closed‐form expressions are obtained for the variance of the centreline displacement, rotation, corner displacement and base shear, that are in terms of the variability of the isolator stiffness, aspect ratio of the structure, and the number and layout of isolation bearings. Results show that the standard deviation of the centreline displacement and base shear decrease with increasing number of isolation bearings, and are independent of the aspect ratio and layout of isolators, and in all cases are less than 1/4 the standard deviation of the isolator stiffness. The standard deviation of the corner displacement is a function of all of the system parameters, and is bounded below by the standard deviation of the centreline displacement and above by the standard deviation of a bar aligned perpendicular to the direction of ground motion with m isolation bearings distributed along the length. The approximate expressions are shown to be in good agreement with the results of Monte Carlo simulations. The results should be of use to designers of isolated structures and manufacturers of isolation systems, in assessing the significance of stiffness variability on the response of the isolated structure. Copyright © 2000 John Wiley & Sons, Ltd.     

波形钢腹板混凝土箱拱地震响应分析

采用时程分析法,对三向地震动作用下的波形钢腹板混凝土箱拱新型结构的地震特性进行分析,通过与混凝土腹板的混凝土箱拱动力特性和地震响应特点的对比,得出该新型拱圈结构具有较优越的抗震性能。同时,把三向地震作用的结果与在两个主方向(纵桥向和横桥向)同时施加地震动的计算结果进行比较,得到竖向地震动对波形板箱拱地震响应的影响程度。