【作者】 全伟；

【导师】 李宏男；

【作者基本信息】 大连理工大学 ， 结构工程， 2008， 博士

【摘要】 理论研究和震害经验都表明,地震是复杂的多维多点运动。多维指的是地震动包括三个平动和三个转动分量;多点,又称为非一致激励或者地震地面运动的空间变化等,指的是结构各支承如果相距较远,所承受的地震地面运动一般是不同的,包括行波效应、部分相干效应和局部场地土效应等。对于大跨桥梁,研究其在多维多点地震作用下的反应特性具有重要的现实意义。本文对多维多点地震动输入,曲线桥多维地震反应分析,多维多点反应谱法及大跨斜拉桥地震反应特性,高墩大跨曲线连续刚构桥多维多点地震敏感参数分析以及多维多点地震动对减、隔震桥梁的影响分析等五个方面进行了研究,完成了以下主要研究内容:(1)提出一种基于小波变换的拟合规范反应谱的多维地震动模拟算法。该方法基于已有的三维实际地震动利用小波变换修正拟合反应谱得到三维人造地震动时程曲线。求解过程中引入快速小波变换法,大大减少了计算量。另外,研究了多维多点的随机模型,针对以往研究中未考虑多点地震动不同点不同地震动分量之间相干性的问题,利用SMART-I台阵的地震记录,分析了其相干函数的值的范围,研究表明:不同点不同地震动分量之间的相干性较弱,随频率的变化趋势不明显,可假定为常数。最后,给出了多维多点人工地震动时程记录模拟的方法。(2)针对曲线桥这种不规则结构,研究了其在单维以及多维地震时程反应分析时的主方向问题,推导给出了多维地震时程分析主方向的求解公式。利用本文方法,仅通过两次时程分析就可以很方便的求得单维和双向地震动作用下曲线桥地震反应的主方向,大大减少了计算量。最后,对比分析了SUM法、SRSS法以及百分比准则等组合方法的准确性。研究结果表明,采用各种组合方法不一定能得到保守的结果,建议对关键部位的内力和位移沿最不利角度输入进行计算。(3)将Kiureghian给出的MSRS多点反应谱方法推广至多维多点领域,利用MATLAB编写了大跨桥梁多维多点反应谱法的程序,研究了大跨斜拉桥在多维多点地震作用下的反应特性。研究结果表明,竖向多点地震反应分析对斜拉桥放大作用最大,纵向多点地震反应分析次之,横向多点地震反应分析影响最小;相比行波效应的影响,部分相干效应的影响较小,初步设计时可不考虑;另外,拟静力效应对桥梁内力影响有限:不考虑同一点和不同点不同分量之间的相干性对斜拉桥可能造成不安全的估计。由此给出了斜拉桥考虑多维多点地震反应的简化方法。最后,提出利用遗传算法求出多维多点反应谱法参数变化时的最大值,用于抗震设计以保证结构的安全。(4)对高墩大跨径曲线连续刚构桥和高墩大跨径直线连续刚构桥在多维多点地震激励下的响应特征进行对比研究,分析了由于“弯”对刚构桥抗震性能带来的影响:然后深入研究了横系梁的设置、桥墩高度、桥梁跨数等敏感参数对桥梁抗震性能的影响。研究表明:“弯”的效应可放大主梁的地震响应,而对主墩地震响应影响较小;在满足稳定性的条件下不设系梁或者少设系梁对地震响应有利;桥墩越高对地震响应一般更有利;跨数增加对桥梁主墩地震响应并不敏感:多维多点地震效应可减小主墩的地震响应,而较大的放大主梁的地震响应。(5)利用SIMULINK仿真工具箱建立了桥梁在多维多点地震激励下的减震控制分析模型。研究了曲线桥在多维多点地震激励下的半主动控制分析,重点探讨了多维多点地震激励以及地震输入的不同角度对结构减震效果的影响规律。研究结果表明,多维多点地震激励对结构的减震效果影响显著,可能显著降低桥梁的预期减震率。激励角度和多点激励效应是相互耦合的。建议在确定半主动控制系统的参数时,应考虑多维多点地震激励的影响,并在激励角度沿着曲线桥弦向方向输入时进行设计,以保证结构的控震效果。此外,利用非线性时程分析法对铅芯橡胶支座隔震桥梁在多点地震激励下的反应规律进行了探索。研究了行波效应、部分相干效应以及局部场地土效应对体系的影响规律。研究表明,采用传统的一致激励假设,可能低估桥梁的响应;三种影响因素中,局部场地土条件的差异影响最大,行波效应次之,部分相干效应的影响最小。更多还原

【Abstract】 Both theoretical research and earthquake damage analysis indicate that earthquake excitations are complex multi-component and multi-support movements. Multi-component refers to the six components of earthquake including three transiational components and three rotational components. Multi-support, also known as non-uniform excitation or spatially variability of earthquake, refers to the different excitations of different supports of the structures. It includes three aspects: wave passage effect, incoherence effect and local site effect. As to large-span bridges, it is significant to analyze the seismic performance under multi-component and multi-support excitations. The five aspects of work done in this thesis are listed as follows.(1) A wavelet-based procedure is proposed to generate artificial multi-dimensional accelerograms whose response spectra are compatible with three-dimensional target spectra. Through wavelet transform, the recorded time histories are scaled to match the target response spectra. Fast wavelet transform method are introduced to improve calculation efficiency. Then, random multi-component and multi-support model is established. The coherency between different components of different supports is analyzed using the SMART-I array accelerogram records. The results show that the coherency between different components of different supports is low, and can be assumed as a constant independent of frequency. Finally, the method to generate multi-component multi-support artificial time histories is given.(2) As to curved bridge, the method to determine the critical angle in time history analysis is investigated. The formula to decide the angle is proposed. Through two individual time history analysis, the unfavourable direction of one dimensional and two-dimensional earthquake can be determined. Then, the combination rules for orthogonal effects of time history analysis, such as the SUM rule, 100/30,100/40 percentage rules and the SRSS rule are also examined. The results show that these combination rules can’t guarantee conservative results. And the paired acceleration time histories along the critical angle should be used in the analysis.(3) According to the MSRS method proposed by Kiureghian, the MATLAB program of seismic response under multi-component and multi-support excitation is established. The seismic performance of large-span cable-stayed bridge under multi-component and multi-support excitations is studied. The results show that: the amplification effect of vertical multi-support excitation is the largest, and longitudinal multi-support excitation takes second place. Transverse multi-support excitation has smallest effect on the bridge. As to wave passage effect, incoherence effect can be omitted. Pseudo-static effect has very limit effect on the total response. The coherency between different components of different and same supports should be considered in order to guarantee the safety of the bridge. Simple calculation method is recommended to account for the multi-component and multi-support effect. Finally, the method using genetic algorithm is proposed to find the maximum value of multi-component and multi-support response spectrum method.(4) The dynamic characteristics of large-span curved and linear continuous rigid frame bridge with high pier under multi-component and multi-support earthquake are compared. The influence of ’curve’ to the seismic performance of the bridge type is discussed. Then, curvature, the setup of straining beam, the height of pier and the span number of the bridge to the seismic response of the bridge type are also analyzed. The results indicate that: the influence of ’curve’ can amplify the seismic response of main girder, and has little effect on the seismic response of piers; the setup of straining beam can amplify the response of the bridge; Increasing the height of the bridge can decrease the seismic response of bridge; span number is not sensitive to the seismic response of the bridge piers; the effect of multi-component and multi-support can decrease the response of the pier and increase the response of the beam.(5) Semi-active control model of bridge under multi-component and multi-support earthquake is established using SIMULINK toolbox. The semi-active analysis of curved bridge under multi-component and multi-support excitation is studied. The emphasis is placed on influence of multi-component and multi-support and the excitation angle to the mitigation rate. The results indicate that the mitigation rate can be decreased by multi-component multi-support effect of earthquake, and the effect of excitation angle and multi-support excitation are coupled. In addition, based on the model of LRB isolated bridge established, the influence of spatially ground motion on the longitudinal seismic response of the system is studied using nonlinear time history analysis. The influence of wave passage effect, incoherence effect and local site effect are studied. The results indicate that the seismic response can be underestimated using the traditional assumption of uniform excitation. And the local site effect has largest detrimental influence on the bridge; wave passage effect takes the second place; incoherence effect takes the least.更多还原