【作者】 雷鑫；

【导师】 傅剑平； 白绍良；

【作者基本信息】 重庆大学 ， 防灾减灾工程及防护工程， 2010， 硕士

【摘要】 到目前为止,世界各国规范抗震设计方法仍然是基于R-μ基本原则,对结构所形成的塑性铰机构(延性能力)和强地震动作用下的位移进行有效控制,以保证结构在强地震动作用下的低倒塌概率的基本设计方法。各国研究者已对单自由度体系的R-μ-T规律作出了较为广泛的研究,得出的结论较为一致。但是,从各研究者采用“从R到μ”研究方法来看,对于新建和既有结构的评估的适用性不强,而且各研究者采用的滞回模型参数与实际结构的滞回特征存在较大出入。虽然,有些研究者也讨论过滞回模型对R-μ-T规律结果的影响,但是所用的滞回模型也仅仅是停留在理论上的模型,并没有考虑实际结构的力学特征。从目前各设计方法中可以看出,大震下的位移控制是目前结构实现的“大震不倒”性态目标的最有效的方式,基于此,各国国家规范和指导性文件都对大震下的结构的位移作出了较为严格的控制。国内外众多研究者针对结构的位移作出过较多研究,大多研究者都集中在结构的响应上,对位移的影响因素的研究较少。尤其是如何方便有效地对多自由度体系在多波输入下的位移反应规律进行识别的研究得更少。基于上述的研究大背景,本文主要对以下内容展开分析:①对单自由度体系R-μ-T规律的已有研究成果进行学习和理解,采用与以往研究手段不同的方法对已有的R-μ-T规律进行计算和验证;②采用更贴近实际钢筋混凝土结构的滞回模型,研究不同滞回模型对单自由度体系R-μ-T规律的影响;③针对单自由度体系的位移特征,采用不同的地面运动输入,分析影响单自由度体系弹性位移与非弹性位移比大小的主要因素;④针对现行规范中对近断层地面运动的考虑不足,采用所收集的近断层脉冲型地面运动,分析近断层脉冲型地面运动对结构反应的影响;⑤设计出周期不同的三榀框架,并将其等效为单自由度体系,考虑单、多自由度体系在多波输入下的位移反应规律,初步验证单自由度体系的位移反应规律在多自由度体系中的适用性。从上述研究工作中,本文可以初步得出以下结论:①短周期结构的延性需求普遍偏大,在地震力折减系数R较大时(R>2),几乎都超过混凝土结构的延性能力,这一点值得设计人员注意;②大多数情况下,实际三折线模型的延性需求都小于两折线模型,且小的幅度随着自振周期和地震力折减系数的增加而增大。当周期很长时,三折线模型计算得出的延性需求已经趋近于1.0,甚至小于1.0。因此,可以认为,Borzi和Elnashai得出的滞回模型对单自由度体系R-μ-T规律影响不大的结论是不合适的。在实际结构非弹性反应分析中,应考虑采用反映混凝土结构实际滞回特征的滞回模型,以获得更为真实的分析结果。③弹性位移反应谱的形状和谱值受震级和断层距的影响较大,震级越大,弹性反应谱的峰值越大,位移放大系数也越大,相应的峰值点周期也越长;弹性位移反应谱谱值随着断层距的增大而减小,但是位移放大系数随着断层距的增大而增大。④震级对结构的非弹性位移影响较为明显,尤其是当震级较大且地震力折减系数较大时,对中等周期结构的非弹性位移影响最明显,而断层距对结构的位移影响相对较弱。⑤近断层脉冲型地震动对结构的弹性和非弹性反应都影响显著,脉冲型地面运动会增大中长周期结构的强度、位移及延性需求。⑥单自由度体系的位移反应规律在多自由度体系中基本适用,即使单自由度体系位移反应较大的地面运动在多自由度体系中的位移也较大,可以借鉴单自由度体系的位移反应来近似估计多自由度体系的位移。更多还原

【Abstract】 Up to now, the main method for seismic design of most national codes is still based on R-μrelationship, which is, to ensure low probability of collapse, the designer makes effectively controls on both the plastic mechanism (ductility capacity) and displacement under rare earthquakes.There are plenty of existed researches on R-μ-T relationship of single-degree-of-freedom system (SDOF), and the conclusions are consistent. However, the“fromμto R”study methods, the researchers took, are not applicable enough for evaluating the existed buildings and the newly built, the hysteretic models in these studies are inconsistence with the real structures. Some researchers had discussed about the effects of hysteretic models on R-μ-T relationship, however, all the hysteretic models are just theoretical, not considering much about the true mechanical characteristics of the structures.In many national design methods, control on displacement under rare earthquakes is the most effective method to ensure“non-collapse uder rare earthquake”of structure. As a result, strict controls on displacement of structure under rare earthquakes are appeared in the national codes and guidance documents. There are many researches on the displacement of the structure, most of them focus on the structural response, but few concern about the influence factors. There are even less researches on how to conveniently identify displacement response rules for multi-degree-of-freedom (MDOF) under multi earthquakes.Based on this background, this dissertation does analysis such as follow:①Study the existed research results of R-μ-T relationship of SDOF, calculate and testimony the existed R-μ-T relationship with a totally different research technique;②Choose the hysteretic models which are closer to the reinforced concrete structures, and also study the effects of hysteretic model on R-μ-T relationship for SDOF system;③With considering the characteristics of SDOF system, take different earthquakes to analyze the main factors influence the displacement ratio of linear SDOF system to non-linear;④To make up the deficiency of lack considering the near-fault ground movement in the present national code, a series of near-fault pulse ground movements are collected to analyze its influence to the response of structure;⑤Design three moment frames with different periods, and make equivalent SDOF systems for them, analyze the displacement response rules of the SDOF systems and MDOF systems under multi earthquake waves, initially prove the applicability of displacement rule for SDOF system in MDOF system.This dissertation gets the initial conclusions from the analysis above, which includes:①The ductility demands of short period structures are generally big, when the earthquake reduction coefficient R is a large number (R>2), almost all the demands of short period concrete structures exceed their abilities. So, the author advices the designers pay attention to it, and earthquake reduction coefficient R may be as small as possible when designing;②Generally, the ductility demands of tri-linear models are smaller than bilinear models, and the range is getting larger at the period gets long or R gets large. For the relatively long period structure, the ductility demands of tri-linear model are close to 1.0, or even smaller than 1.0. Hence, this dissertation supposes the result of Borzi and Elnashai which indicates the hysteretic models have no influence on the R-μ-T relationship is improper. In the inelastic analysis of real structures, to get the more appropriate results, it should take hysteretic models which could reflect the real hysteretic characteristics of the structures;③The shapes and values of elastic displacement response spectrum are influenced by the magnitude and the fault distance, a bigger peak value of elastic response spectrum would be achieved when the magnitude is larger; The period correspond to the peak point is longer when the magnitude is larger; The values of elastic displacement response spectrum are smaller and the displacement amplification coefficient is larger with remoter fault distance;④The effects of magnitude on the inelastic displacement are significant, special at a larger R, it is most significant for the middle period structures. On the contrary, the fault distance influence little to the displacement;⑤The near fault pulse earthquakes significantly influence both linear and inelastic response of structures. The pulse global movements would magnify the strength, displacement and the ductility demand of middle or long period structures;⑥The displacement rule for SDOF system is basically applicable in MDOF system. The designer could approximate evaluate the displacement of MDOF system by checking the displacement response of the equivalent SDOF system.更多还原