【作者】 尹犟；

【导师】 易伟建；

【作者基本信息】 湖南大学 ， 结构工程， 2011， 博士

【摘要】 基于性能抗震工程PBSE理论是21世纪国际地震工程界的重要课题,而准确有效地评估结构在地震作用下的最大反应(地震需求)则是其关键所在。围绕混凝土结构的地震需求估计方法,本文进行了以下几个方面的研究工作:1.在对常规Pushover分析方法的精度以及适用范围进行详细分析的基础上,考虑模态Pushover分析和自适应Pushover分析当中一些值得借鉴的思想,对常规Pushover分析方法提出改进,建议了两种修正的Pushover分析方法。修正方法Ⅰ考虑了结构屈服后振动特性的改变,推覆分析过程中根据结构的屈服振型对其屈服后的形状向量及水平荷载模式进行修正,减小了Pushover方法对结构楼层及层间位移的估计误差。修正方法Ⅱ在修正方法Ⅰ的基础上,考虑多阶振型的组合效应,进一步提高了其估计精度。对于以整体机制失效的框架,修正方法Ⅱ的估计误差约为5%左右;而对于以局部机制失效的框架,该方法的估计误差也能控制在10%左右的范围。2.收集30组双分量近场地震加速度记录,分别计算其水平及竖向分量的加速度反应均值谱,发现近场地震的确具有明显高于远场地震的竖向效应。对6层和10层框架结构算例按是(否)考虑竖向效应两种情况进行动力时程分析,分析结果表明,近场地震竖向效应对结构的楼层和层间位移需求具有明显的增大作用。合理考虑近场地震竖向效应对结构水平方向位移需求的影响,对传统Pushover分析方法提出了改进,改进后的方法首先按一定方式在结构的每一个集中质量处施加竖向地震力,然后对结构进行水平方向的Pushover分析。采用4种Pushover分析方法估计了两个框架结构算例的楼层及层间位移需求,并根据时程分析统计结果对4种方法的准确性进行了评估。3.基于Pushover理论的基本假定,推导了多自由度体系结构与其等效单自由度体系之间的能量转换关系,建议了一种估计多自由度体系结构变形能及地震耗能的近似方法。在此基础上,借鉴混凝土构件损伤性能评估的基本思想,提出一种评价混凝土结构整体抗震性能的简化方法。该方法综合考虑结构的最大变形及地震耗能对其整体抗震性能的影响,基于Park-Ang损伤模型计算结构的整体损伤指数,并据此对其整体抗震性能进行综合评估。算例分析表明,简化方法估计所得结构地震耗能与时程分析结果较为接近,且估计结果偏于安全。4.分析了基本不确定因素通过结构体系进行传递,并使结构的地震需求参数也出现不确定性的过程。探讨了将FOSM法、Tornado图形法和直接统计法应用于敏感性分析的优势和局限性。以一个典型混凝土框架结构为例,综合运用一次二阶矩方法、Tornado图表法和直接统计法,估计了4种结构地震需求参数对于一系列基本不确定因素的敏感度,进而对基本不确定因素的重要性进行了排序。分析结果表明,结构的地震需求对地震动的强度和特征最为敏感。5.提出一种新的地震动随机模型,并根据不同的场地类别和设计地震分组,参照现行抗震规范谱对地震动随机模型中的参数进行了标定。从新的地震随机动模型出发,基于概率可靠度理论确定了结构弹性及弹塑性位移需求的概率分布函数,并以此为基础建立了结构的概率弹性及弹塑性位移需求谱。结合本文理论和Pushover分析方法,建议了结构随机地震反应分析和概率地震需求分析的简化方法,建议方法与和数值方法的分析结果比较接近,但计算工作量大大小于以大量动力时程分析为基础的数值方法。更多还原

【Abstract】 Performance-based seismic engineering (PBSE) is a very important research project in the field of international earthquake engineering, and estimating the maximum response of structures under seismic action accurately and efficiently is the key point of PBSE exactly. Focused on the structural seismic demand estimation method, this dissertation involves the following work:1. The estimation precision and the application range of the ordinary Pushover Analysis Method are discussed in detail. Using some recommendable idea of Model Pushover Analysis and Adaptive Pushover Analysis for reference, two kinds of Modified Pushover Analysis Method (MPAM) are proposed based on ordinary pushover analysis procedures. Considering the structural vibration characteristics after yielding, MPAMⅠcorrect the lateral loading pattern and the shape vector according to the yielding mode during Pushover Analysis procedures, hence the estimation error of floor displacement and the inter-story drift is reduced significantly. Compared to MPAMⅠ, MPAMⅡconsider the effect of Hmodal combination H, its estimation precision is Improved further more. For the frame damaged with integral mode , the estimation error of MPAMⅡis about 5%, For the frame damaged with local mode , the estimation error of MPAMⅡis about 10%.2. Based on 30 sets of two-component acceleration records of near-fault earthquake, the mean acceleration response spectrums are calculated in horizontal and vertical direction, the results shows that, compared to the far-fault earthquake, the near-fault earthquake really have much higher vertical effect. Using each set of near-fault acceleration records, a set of dynamic time-history analyses is carried out to determine the displacement responses of 6 story and 10 story frames, the results show that the vertical effect of near-fault earthquake will remarkably amplify the floor displacement and the inter-story drift demands of frame structures. Therefore, considering the vertical effect of near-fault earthquake properly, the modified pushover analysis procedures are proposed in this paper. According to the modified pushover method, the vertical seismic force should be loaded on every lumped mass of multi-degree-of-freedom structures at first, after that the pushover analysis in horizontal direction could be carried out as ordinary. To evaluate the accuracy of the modified and unmodified method, the floor displacement and the story drift demands of six story and ten story frames are estimated using 4 kinds of Pushover Analysis Methods, and compared with the results obtained from the dynamic time-history analysis.3. On the basis of the basic assumptions of pushover theory, the approximate relationship for converting the energy between the MDOF system structure and its equivalent SDOF system is deduced, and an approximate method is suggested to estimate the deformation energy and hysteretic energy of multi-degree-of-freedom system. In light of the idea of seismic damage evaluation of concrete members, a simplified approach is proposed to evaluate the overall seismic performance of concrete structures. The simplified approach synthetically considers the influences of maximum deformation and energy dissipation of structures, and evaluates the overall seismic performance of structures according to structural damage index calculated by Park-Ang damage model. The numerical example indicates that the results of simplified method are very close to the results obtained from time-history analysis, and are safe to some extent.4. The uncertainty generation of earthquake demand parameters caused by a series of basic uncertain factors is analyzed. At the same time, the Hadvantages H and limitations of FOSM method, Tornado Diagram method and Mathematical Statistics method are discussed for the purpose of sensitivity analysis. Illustrated by the case of a frame structure, the sensitivity of four kinds of earthquake demand parameters to a series of basic uncertain factors are estimated using three kinds of methods mentioned above, and the basic uncertain factors are arranged in important order. The result shows that the uncertainty of earthquake demand parameters is most sensitive to the intensity and the profile of ground motion.5. A new seismic random model is proposed, and the model parameters are determined according to different site classifications and design earthquake effects specified in current seismic code. In terms of the new seismic random model, the probabilistic distribution of structural elastic and elastic-plastic displacement demand is deduced based on reliability theory, and the elastic and elastic-plastic displacement spectrum are established. Integrating the theory in this paper and the pushover analysis procedure, the simplified methods for random seismic response analysis and the probabilistic seismic demand analysis are suggested, moreover on the basis of the SDOF and MDOF system case ,the numerical verification are carried out for validating the accuracy of simplified methods. The calculating results of simplified method are very close to which of the numerical method, while the working amount of simplified method is much less than which of the numerical method.更多还原