连续梁桥减、隔震体系的优化设计

本文根据连续梁桥减、隔震体系设计的特点,建立了桥梁减、隔震体系优化设计公式,实现了应用结构最优化设计理论设计桥梁减、隔震支座动力控制参数,使得桥梁墩、台所受到的地震水平力最小的同时满足小震作用下桥梁结构保持弹性;强震作用下减、隔震支座发生弹塑性变形耗散地震能量的减、隔震设计思想.通过编制的桥梁减、隔震体系优化设计程序,对连续梁桥减、隔震体系优化设计进行了算例分析,得出了一些有用的结论.     

中小跨径板式橡胶支座梁桥横向抗震设计研究

为提高中小跨径板式橡胶支座梁桥在强震作用下的横向抗震性能,在总结汶川震区该类梁桥震害特点和国内外桥梁抗震设计规范中相关抗震设计策略规定的基础上,归纳当前我国板式橡胶支座梁桥横向抗震体系存在的问题,提出适合我国中小跨径板式橡胶支座梁桥的横向抗震设计方法,即允许上、下部结构连接构件牺牲的准隔震设计方法,介绍该抗震设计方法设计思想,给出在两设防水准下结构各部件的性能目标要求。选择一座典型板式橡胶支座简支梁桥为研究对象,基于文中抗震设计方法的设计思想,提出采用新型隔震系统对计算桥例进行准隔震设计。结果表明：通过对横向限位装置力学性能参数的合理设计,通过桥梁结构在强震作用下板式橡胶支座的滑移、横向限位装置的损伤或牺牲,控制上、下部结构间传递的梁体惯性力,保护墩柱和基础等下部结构免遭严重损害,同时能有效控制墩梁相对位移,防止过大的梁体移位导致的交通阻断、甚至落梁。     

Seismic vulnerability assessment of wall pier supported highway bridges using nonlinear pushover analyses

Pushover analyses were conducted to assess the seismic vulnerability of wall pier supported highway bridges on southern Illinois priority emergency routes. Three-dimensional finite element models were developed to reflect typical hammerhead and regular wall pier bridges from a random sample of the bridge inventory. The models incorporated expected nonlinear structural and material behavior of all the bridge components—superstructure, expansion joints, approach embankments and/or abutments, bearings, wall piers, footings and/or pile caps, and pile and/or mat foundations (plus soil effects)—as well as defining failure measures for each component. Both transverse and longitudinal pushover analyses were conducted on ninety wall pier bridge models reflecting the sample population variation in bridge characteristics such as wall pier type, number of piers, skew, type of foundation, concrete reinforcement ratio, bearing type, and wall height. It was found that the population of wall pier bridges studied was generally vulnerable to wall bearing and abutment bearing failures, wall pier ductility failures, and footing shear and/or bending failures, with bridge skew leading to a coupling of the failure mechanisms from the two pushover directions.     

滑动摩擦支座隔震桥梁地震反应分析

多滑面摩擦隔震支座具有刚度和阻尼的自适应性,在基于性能的桥梁抗震设计中有广泛的应用前景。本文以某近海连续梁桥为工程背景,考虑海洋软土条件,应用p-y法模拟桩-土相互作用,通过单摩擦摆（FPS）串联组成多滑动面摩擦摆支座（MFPS）模型,并建立全桥有限元模型。采用反应谱法和快速非线性分析（FNA）两种方法,对设置单滑面摩擦摆支座和多滑面摩擦摆支座的两种不同支座的隔震桥梁体系进行地震响应分析。对比分析两种方法得到的两种隔震桥梁结构的支座滞回性能和墩底剪力等的地震响应规律。研究结果表明,两种支座均具有较好的隔震效果,采用MFPS支座的桥墩的地震响应比FPS支座有所减小,且具有较大位移能力。     

Design of Rupture Strength of Side Blocks in Elevated Steel Girder Bridges with Elastomeric Bearings

Elastomeric rubber bearings with side blocks have been extensively used as a seismic response-control device in steel girder bridges in Japan. In real scenarios, the behavior of the girder bridges with elastomeric bearings are usually complex because of the complex mechanism by which the seismically induced inertia forces at concrete deck transmits to the girder bearings. Therefore, it is important to carry out seismic response analysis of a whole bridge system considering the interaction between different structural components in order to check the performance of the side blocks during an event of severe earthquakes. The objectives of the present study are to develop a detailed three-dimensional finite element (FE) model of an elevated girder bridge system and to propose a design rupture strength for the side blocks. The FE-model is constructed based on an existing plate girder bridge considering the effect of concrete slab, girders, stiffeners, rubber bearing, pier and the damage control by the side blocks. A sequence of seismic response analysis is then performed using four different rupture forces of the side blocks by considering the Level-2 design earthquake, the 1995 Kobe earthquake and the 2016 Kumamoto earthquake. The analytical investigation reveals that the side blocks should be designed to withstand a horizontal force of at least 1200 kN in order to prevent the rupture of the side blocks and to mitigate damage of bridge piers. Moreover, the damage to the critical parts of bridge superstructure can be mitigated by strengthening the side blocks. Based on the analysis results, a retrofit plan to strengthen the side blocks of existing girder bridges is proposed.

     

高墩连续梁桥减震设计研究

采用常规抗震设计方法设计的高墩连续梁桥,无论是滑动支座还是固定支座下的桥墩,在地震作用下的墩底内力和墩顶位移均较大。针对高墩连续梁桥这一特点,本文以某大型跨江桥梁的引桥工程作为分析实例,将目前在建筑结构中研究比较成熟的多种减、隔震技术应用于高墩连续梁桥,对其减震效果进行了探讨。分析结果表明,各减、隔震设计方案均有各自的优势及局限性,需根据桥梁结构的具体要求来选择适当的抗震、减震设计方案。     

极罕遇地震作用下铅芯橡胶隔震支座基础隔震结构抗震性能研究

基础隔震结构在设计地震和罕遇地震作用下具有良好的抗震性能。随着GB 18036—2015《中国地震动参数区划图》引入了极罕遇地震作用，有必要探讨基础隔震结构在极罕遇地震作用下的抗震性能。以两自由度体系(简化模型)和多自由度体系(纤维模型)的铅芯橡胶隔震支座(LRB)基础隔震结构为研究对象，基于弹塑性时程分析的统计结果，分析并比较了设计、罕遇和极罕遇地震作用下上部结构屈服承载力(即降低上部结构抗震设防烈度)和LRB隔震支座力学性能参数对整个LRB基础隔震结构抗震性能的影响。分析结果表明：极罕遇地震作用下，采用降低抗震设防烈度的方式对隔震后的上部结构进行结构设计并不可取；为了保证在极罕遇地震作用下LRB基础隔震结构的上部结构和LRB隔震支座不发生破坏，应尽可能使用大直径和低橡胶剪切模量的LRB隔震支座；如何保证LRB基础隔震结构在设计地震和罕遇地震作用下的性能要求以及在极罕遇地震作用下的安全性能是一个具有挑战性的问题。     

规则型隔震桥梁结构的简化分析方法

由于桥墩的质量与上部结构的质量相比通常是比较小的,各桥墩高度和截面大致相同的连续桥梁可以简化为单自由度体系进行抗震设计.当在桥面大梁与桥墩之间设置隔震橡胶支座时,上述规则型桥梁可以看作串连型双自由度体系.文中根据桥墩的水平刚度远大于橡胶支座的水平刚度和上部结构的质量甚大于桥墩的特点推导了此双自由度体系的自振特性(包括自振周期、振型、地震作用的振型参与系数和振型阻尼比)的简化计算公式.这些公式可以方便地应用于隔震桥梁的抗震设计.此外,文中还分析了这些简化公式的计算精度与双自由度体系质量比和刚度比的关系.精度分析和数字实例的计算结果表明,文中提供的公式具有足够的精度.     

Fragility analysis of track-on steel-plate-girder railway bridges in Korea

More than 40% of the bridges in conventional Korean railway lines are track-on steel-plate-girder (TOSPG) bridges. They are characterized by a superstructure consisting of railway tracks sitting directly on steel plate girders without any ballast system. Most of these bridges have been designed with little or no consideration given to seismic loading. In this paper, seismic fragility curves of TOSPG bridges in Korea are developed. Fragility curves are developed first for the components, by using the probabilistic seismic demand model. The developed component fragility curves show that the bearings are the most vulnerable components of the TOSPG bridges against seismic loading. On the other hand, the piers are much less vulnerable, although they contain no reinforcing bars. This is because the superstructure mass is very light, and therefore horizontal loading transferred from the superstructure to the piers is minimal. A generic damage measure is introduced for measuring the system-level damage of structures out of the component-level damages. The system fragility curves are then developed, using the generic damage measure. Finally, representation of seismic risk in terms of expected seismic losses is demonstrated. This demonstration shows how the fragility analysis is utilized for risk assessment and support in decision-making.     

Uplift of elastomeric bearings in isolated bridges subjected to longitudinal seismic excitations

Bearings are used to isolate bridge substructures from the lateral forces induced by creep, shrinkage and seismic displacements. They are set in one or two support lines parallel to the transverse axis of the pier cap and are typically anchored to the deck and to the pier cap. This detailing makes them susceptible to possible tensile loading. During an earthquake, the longitudinal displacements of the deck induce rotations to the pier caps about a transverse axis, which in turn cause tensile (uplift) and compressive displacements to the bearings. Tensile displacements of bearings, due to the pier rotations, have not been addressed before and questions about the severity of this uplift effect arise, because tensile loading of bearings is strongly related to elastomer cavitation and ruptures. An extended parametric study revealed that bearing uplift may occur in isolated bridges, while uplift effect is more critical for the bearings on shorter piers. Tensile displacements of bearings were found to be significantly increased when the isolators were eccentrically placed with respect to the axis of the pier and when flexible isolators were used for the isolation of the bridge. The results of this study cannot be generalised as bridge response is strongly case-dependent and the approach has limitations, which are related to the modelling approach and to the fact that emphasis was placed on the longitudinal response of bridges.     

基础隔震密肋壁板大开间结构地震反应分析

采用微分型滞回恢复力模型模拟隔震支座的恢复力特性,通过对基础隔震密肋壁板大开间结构动力性能的分析表明,采用隔震技术可以有效降低上部密肋壁板大开间结构的地震反应,使其既达到抗震设防的要求,又满足建筑功能的需要.     

同步顶升更换支座施工方法探讨

橡胶支座作为桥梁的重要传力装置,其架设于墩台上,顶面支承桥梁上部结构,是连接桥梁上、下部的重要结构部件。然而,由于桥梁通车年限的增长、野外环境影响、车流量增多、年久失养以及支座老化等原因,桥梁支座随之出现了开裂、变形、脱空、移位等一系列的问题,并且逐渐丧失了使用功能,更换支座的相关技术及施工因此应运而生。本文基于对四川南充清泉寺嘉陵江特大桥梁工程支座更换施工的分析和实践经验,探讨同步顶升更换支座的施工工艺方法,供同类情形参考。     

基于不同隔震体系的预制拼装桥墩桥梁结构 地震响应分析

为了研究预制拼装桥墩桥梁结构的地震响应,基于OpenSEES有限元分析软件建立墩顶隔震和墩底隔震的预制拼装桥墩连续梁桥分析模型; 通过分析桥梁模型在3组不同强度、不同特性地震动激励下的动力特性、位移、内力、残余位移、预应力筋预应力、接缝压力等参数的变化,对隔震体系的隔震效果进行评估并给出了墩底隔震桥梁的设计建议。结果表明:预制拼装桥墩连续梁桥采用墩顶隔震体系和墩底隔震体系均可以大幅减小桥梁在地震中的位移和内力,延长桥梁自振周期; 采用墩梁固接、墩底隔震的桥梁结构相比于直接采用隔震支座连接墩梁的桥梁结构具有更长的自振周期、更小的震中位移和墩顶残余位移,表现出更好的隔震效果,在大地震中墩底隔震体系隔震优势更加明显; 采用墩底隔震体系的桥梁预制拼装桥墩会有更大的预应力变化、预应力损失和接缝竖向压力,因此隔震支座也应具备更高的性能。     

The response of a 344 m long bridge to non-uniform earthquake ground motions

This paper investigates the influence of wave velocity and the dispersion of waves associated with variations in seismic ground motions, on the inelastic responses of four 344 m long bridges. The bridges were 9 span continuous prestressed concrete box girders supported on sliding bearings, which eventually permitted movement in the longitudinal direction of the bridges, with shear keys that prevented transverse movement. The sub-structure consisted of reinforced concrete circular piers with cross-heads and rigid beams at the abutments. Earthquake motions were applied in the transverse direction for two bridges and for two others, with two expansion joints, the motions were applied longitudinally. The analyses of the latter were carried out to examine expansion gap movements and all analyses were carried out to produce time-history responses of pier drift, pier shear forces and pier curvature demands. The reinforcement in the piers was modelled so that either one base hinge can form or one base hinge with a hinge at the top of the pier. Pier heights varied between 5 m and 11 m or, for one bridge, were of constant height of 11 m. The non-uniform earthquake inputs at supports were generated by using the conditional simulation method with a natural earthquake record specified at one abutment. The response to wave velocities from 100 to 2000 m/s and infinity were studied both without dispersion and with various degrees of dispersion. The El Centro 1940 N–S and Sylmar Northridge 1994 N–S were used as the transverse earthquakes and the E–W components were used longitudinally. The results of these analyses show that non-uniform earthquake ground motions significantly influence the response of long bridges both with and without expansion joints. The responses change significantly with travelling wave velocity and the degree of dispersion and these can be more critical than for uniform inputs. Significant dispersion can generate rotational inertia of the deck and, with the torsional stiffness of the deck, can lead to the formation of top and bottom pier hinges and significantly larger shear forces compared to the normal cantilever design of these types of bridge piers.     

多点激励下桩-土-斜拉桥全模型振动台试验研究

大跨斜拉桥的自振频率和阻尼低以及空间尺度大,其地震响应受桩基础、场地土特性和地震动空间效应的影响较大。然而,由于试验条件和技术所限,目前尚缺乏相关的全模型振动台试验研究。以一座试设计主跨1400m超大跨斜拉桥为原型,设计和制作了一座几何相似比为1/70且包括上部结构、桩基础和场地土等在内的试验模型,通过振动台试验研究了多点激励对桩-土-斜拉桥全模型地震响应的影响及其规律。试验结果表明：纵向多点激励使一侧主塔的纵向位移、一侧主塔和桥墩的纵向桩-土-结构相互作用效果以及主跨一侧竖向位移增大,而另一侧减小;横向多点激励使一侧主塔的横向位移和一侧桥墩的横向桩-土-结构相互作用效果增大,另一侧减小,但使两侧主塔的横向桩-土-结构相互作用效果和主跨两侧横向位移响应均增大;桩-土-结构相互作用对斜拉桥的加速度响应产生不利影响。基于上述结果,大跨斜拉桥的抗震设计或性能评估应考虑多点激励和桩-土-结构相互作用的影响。     

Optimal probabilistic design of seismic dampers for the protection of isolated bridges against near-fault seismic excitations

A probabilistic, simulation-based framework is presented in this paper for risk assessment and optimal design of supplemental dampers for multi-span bridge systems supported on abutments and intermediate piers through isolation bearings. The adopted bridge model explicitly addresses nonlinear characteristics of the isolators and the dampers, the dynamic behavior of the abutments, and the effect of pounding between the neighboring spans against each other as well as against the abutments. Nonlinear dynamic analysis is used to evaluate the bridge performance, and a realistic stochastic ground motion model is presented for describing the time history of future near-fault ground motions and relating their characteristics to the seismic hazard for the structural site. A probabilistic foundation is used to address the various sources of structural and excitation uncertainties and ultimately characterize the seismic risk for the bridge. This risk is given by the expected value of the system response over the adopted probability models. Stochastic simulation is used for evaluating the multi-dimensional integral representing this expected value and for performing the associated optimization when searching for the most favorable damper characteristics. An efficient probabilistic sensitivity analysis is also established for identifying the importance of each of the uncertain model parameters in affecting the overall risk. An illustrative example is presented that considers the design of nonlinear viscous dampers for the protection of a two-span bridge.     

Study on dynamic response of large and small aspect ratio isolated buildings

An experimental study of a large aspect structure, 1:4 scale five‐storey steel frame, is presented. Seismic responses of the test model to the unilateral and bilateral excitations are compared. The effects of aspect ratio on the maximum acceleration, the storey drift of the superstructure, the maximum displacement and the vertical load of the isolation system are investigated. A comparison of the large aspect ratio isolated building with the small aspect ratio isolated building showed significant difference of the effects of aspect ratio subjected to disparate earthquake ground motions. Experimental results reveal that the aspect ratio is an important factor influencing the axial load action on isolators and the tension stress of the lead‐rubber bearings. The superstructure flexibility of the large aspect ratio building‐isolation system and the effects of the axial force variation of the lead‐rubber bearings should be carefully considered for design. Copyright © 2013 John Wiley & Sons, Ltd.     

隔震支座沿曲面布置的隔震结构动力响应及振动台试验研究

针对超设计基准地震作用下隔震层存在过大变形、影响结构安全等问题,基于已提出的一种隔震支座沿曲面布置的隔震结构,通过变形和受力分析建立了简化双自由度动力模型,得到了系统关键动力参数,即公转频率、自转频率及单摆频率等的计算式.进一步给出了结构响应传递函数,明确了结构高宽比、曲面角度、隔震层阻尼比对结构响应的影响规律,并基于...     

基础隔震结构中上部结构与隔震层的刚度比限值研究

以控制结构变形为目标,将上部结构刚度与隔震层刚度的比值定义为隔震刚度比,作为反映上部结构与隔震层协同变形特点的指标。假定上部结构的地震作用沿高度为矩形分布,在一般结构单质点简化方法基础上提出一种隔震结构动力分析的等效简化方法。进一步分析双自由度等效模型的刚度影响和动力特性,以隔震刚度比的形式解释了结构位移需求、位移分配函数以及隔震刚度比对结构抗震性能的影响。基于抗震性能,推导出结构位移需求与周期关系式、临界隔震刚度比表达式、最大和最小隔震刚度比限值表达式。选取不同结构高度、地震烈度、阻尼条件等计算了上部形式为框架、框-剪、剪力墙结构的三类隔震结构在罕遇地震作用下的隔震刚度比限值。结果表明,一般隔震结构的隔震刚度比限值不宜小于4,低多层隔震结构主要由最小隔震刚度比控制,高层隔震结构在特定条件下需要满足最大隔震刚度比限值。计算结果整理成表格可供设计参考。     

梁式桥防止地震碰撞及落梁装置与措施的研究进展

在强烈地震中,桥梁上部结构在伸缩缝处发生的碰撞能够引起上部结构的破坏,并影响到支座、墩身和基底的受力状态,在地震作用下的落梁现象也多有发生。本文综述了国内外在避免地震时桥梁之间的碰撞及防止落梁措施方面的研究进展,并且介绍了几种纵向连接装置的性能。对进一步研究提出了新的思路。