城市桥梁基桩承载性能时间效应试验研究

岩土的流变性质使建（构）筑物基础的承载性能具有时间相关性,对运营期建筑结构的安全性造成较大的影响。为了进一步探讨城市桥梁桩基础承载性能随时间的变化规律,对某桥梁工程的2根试验桩进行了长效荷载试验研究,得出了桩顶沉降和桩身承载性能随时间的变化规律。利用桩基承载性能时空效应新理论对试验结果进行分析拟合,获得真实的桩土力学参数,得到工程桩桩顶沉降随时间变化的解析解。试验成果进一步揭示了桩在长效荷载作用下自然而真实的发展变化规律,为检验验证理论研究成果提供可靠的依据,可用于指导同等条件下工程桩设计和施工时预测桩的工后沉降变化趋势,控制基础稳定性,同时为解决路桥的工后运营期沉降控制提供科学合理的理论依据。     

钢桁梁桥基于模型修正方法的损伤程度识别研究

在钢桁梁桥模型损伤定位的基础上,采用模型修正方法对其损伤程度进行识别,对其中几个关键问题进行了研究分析,得出了一些有用的结论,可作为实际桥梁健康监测的参考依据。     

The Concept and Development of Smart Structures Technologies for Long-span Cable-supported Bridges

This article presents an overview of smart structures technologies in connection with long-span cable-supported bridges. Considering the broad scope of the smart structures technologies, two subareas, namely, structural health monitoring and structural control technologies, and their applications in long-span cable supported bridges, are identified as the focus of this review. It is believed that by, adopting the smart structures technologies, reliable operation and hazard management of long-span bridges can be achieved much more efficiently and can be made economically feasible, especially for bridges located at sites with high risks of severe natural hazardous events, such as those facing the bridges of the Taiwan Strait Crossing project. The feasibility of and practical issues in implementing the smart structures technologies in the design and construction of long-span cable-supported bridges are also discussed here. Considering the time span of the construction of the Taiwan Strait Crossing, some of the innovative technologies with a high potential for future long-span bridge applications, while still at the stage of exploratory research at the time of writing, are also examined as it is believed these technologies might have become prevalent by the completion time of the Taiwan Strait Crossing project.     

乌东德高拱坝极限抗震能力研究

乌东德水电站是金沙江下游河段上4个水电梯级的最上游梯级,大坝为265 m高的双曲拱坝。采用非线性有限元法,将拱坝坝体-坝基作为一个整体系统,在考虑坝体横缝影响及无限地基辐射阻尼影响基础上,模拟坝肩控制性滑块各滑裂面在地震作用下张开、滑移的非线性力学行为,研究设计与校核地震作用下大坝的抗震性能,探讨大坝-坝基整体系统在强震作用下的抗震潜力。研究结果表明：设计地震条件下,坝体仅在拱端应力集中区域拉应力超过抗拉强度,压应力则均满足强度要求,坝肩块体稳定,大坝-坝基体系的整体安全性可以保证;校核地震条件下,坝体应力值略有增加,能够满足不溃坝的设防要求;以大坝-坝基代表性的位移、变形量变化曲线的拐点作为评价极限抗震能力的标准,可知拱坝-坝基体系的抗震超载安全系数为2.7,相应的基岩水平向峰值加速度0.729g,拱坝-坝基体系抗剪参数强度储备安全系数为2.0,乌东德高拱坝具备较强的极限抗震能力。     

Nonlinear earthquake analysis of high arch dam–water–foundation rock systems

A nonlinear finite element model for earthquake response analysis of arch dam–water–foundation rock systems is proposed in this paper. The model includes dynamic dam–water and dam–foundation rock interactions, the opening of contraction joints, the radiation damping of semi‐unbounded foundation rock, the compressibility of impounded water, and the upstream energy propagating along the semi‐unbounded reservoir. Meanwhile, a new equivalent force scheme is suggested to achieve free‐field input in the model. The effects of the earthquake input mechanism, joint opening, water compressibility, and radiation damping on the earthquake response of the Ertan arch dam (240 m high) in China are investigated using the proposed model. The results show that these factors significantly affect the earthquake response of the Ertan arch dam. Such factors should therefore be considered in the earthquake response analysis and earthquake safety evaluation of high arch dams. Copyright © 2011 John Wiley & Sons, Ltd.     

Experimental investigation of spatially varying effect of ground motions on bridge pounding

Pounding between adjacent bridge structures with insufficient separation distance has been identified as one of the primary causes of damage in many major earthquakes. It takes place because the closing relative movement is larger than the structural gap provided between the structures. This relative structural response is controlled not only by the dynamic properties of the participating structures but also by the characteristics of the ground excitations. The consequence of the spatial variation of ground motions has been studied by researchers; however, most of these studies were performed numerically. The objective of the present research is to experimentally evaluate the influence of spatial variation of ground motions on the pounding behaviour of three adjacent bridge segments. The investigation is performed using three shake tables. The input spatially varying ground excitations are simulated based on the New Zealand design spectra for soft soil, shallow soil and strong rock using an empirical coherency loss function. Results confirm that the spatially nonniform ground motions increase the relative displacement of adjacent bridge girders and pounding forces. Copyright © 2012 John Wiley & Sons, Ltd.     

Characterization of rocking shallow foundations using centrifuge model tests

This paper presents new results of centrifuge model tests exploring the behavior of rocking shallow foundations embedded in dry sand, which provides a variety of factors of safety for vertical bearing. The results of slow (quasi‐static) cyclic tests of rocking shear walls and dynamic shaking tests of single‐column rocking bridge models are presented. The moment–rotation and settlement–rotation relationships of rocking footings are investigated. Concrete pads were placed in the ground soil to support some models with the objective of reducing the settlement induced by rocking. The behavior of rocking foundation was shown to be sensitive to the geometric factor of safety with respect to bearing failure, L_f/L_c, where L_f was the footing length, and the L_c was the critical soil‐footing contact length that would be required to support pure axial loading. Settlements were shown to be small if L_f/L_c was reasonably large. Placement of concrete pads under the edges of the footing was shown to be a promising approach to reduce settlements resulting from rocking, if settlements were deemed to be excessive and also had impacts on the energy dissipation and rocking moment capacity. A general discussion of the tradeoffs between energy dissipation and re‐centering of rocking foundations and other devices is included. Copyright © 2011 John Wiley & Sons, Ltd.     

Dynamic interaction of bridge–train system under non‐uniform seismic ground motion

The probability that an earthquake occurs when a train is running over a bridge in earthquake‐prone regions is much higher than before, for high‐speed railway lines are rapidly developed to connect major cities worldwide. This paper presents a finite element method‐based framework for dynamic analysis of coupled bridge–train systems under non‐uniform seismic ground motion, in which rail–wheel interactions and possible separations between wheels and rails are taken into consideration. The governing equations of motion of the coupled bridge–train system are established in an absolute coordinate system. Without considering the decomposition of seismic responses into pseudo‐static and inertia‐dynamic components, the equations of motion of the coupled system are formed in terms of displacement seismic ground motions. The mode superposition method is applied to the bridge structure to make the problem manageable while the Newmark‐β method with an iterative computation scheme is used to find the best solution for the problem concerned. Eight high‐speed trains running over a multi‐span steel truss‐arch bridge subject to earthquakes are taken as a case study. The results from the case study demonstrate that the spatial variation of seismic ground motion affects dynamic responses of the bridge–train system. The ignorance of pseudo‐static component when using acceleration seismic ground motions as input may underestimate seismic responses of the bridge–train system. The probability of separation between wheels and rails becomes higher with increasing train speed. Copyright © 2011 John Wiley & Sons, Ltd.     

铁路连续梁拱组合桥基于摩擦摆支座的减隔震研究

研究了铁路连续梁拱组合体系桥梁的支座减、隔震设计.针对该桥梁的特点提出了摩擦摆支座减、隔震设计的原则与方法;建立全桥计算模型,采用非线性时程分析方法重点分析了摩擦摆支座的减、隔震效果.结果表明,采用摩擦摆支座可以显著地减小结构顺桥向的最大地震弯矩及拱顶变形,横桥向的减、隔震效果受输入地震动的影响很大.     

扩频微波网桥在新疆测震网络中的应用

以频率为2.4 GHz和5.8 GHz设备为例,对扩频微波网桥在新疆测震网络中的应用范围进行阐述;根据实际工作中无线网桥的安装架设经验,对在不同条件、不同环境下可能出现的问题提出相应解决方案.