钢筋混凝土结构抗震性能分析方法

到2008年我国《建筑结构抗震规范》(GBJ11-89)实施近20年,新抗震规范(GB50011-2001)实施也有7年时间,我国四川汶川大地震,造成了巨大的人员伤亡、房屋倒塌和经济损失,这些房子大部分是89规范实施后建造的,发生这么大规模的倒塌需要我们对现行抗震设计理论、抗震设计方法和结构构造措施等进行反思,对其进行深入研究,以保证这些结构适用性的前提下,加强强震作用下的结构安全性和可靠性。为此本文基于结构的能量反应研究了结构抗震性能分析方法,基于滞回能统计特征研究了结构动力可靠度,以及通过基于随机有限元方法对结构的体系可靠度进行分析主要研究内容如下:1推导了弹性及弹塑性单自由度体系能量反应方法以及能量谱计算方法,分析了地震动特性和结构特性对能量反应的影响规律,每类场地选取40条地震波计算了能量谱,并回归了三段式能量谱简化计算公式。2推导了简化层模型多自由体系能量反应的振型分解法和能量反应时程计算方法,研究了弹塑性体系的滞回能的层间分布规律。利用MSC.MARC建立了精细有限元模型,推导了精细有限元模型能量计算,研究了框架结构和框架剪力墙结构的能量反应规律和塑性变形能的分布规律。提出了杆系构件的塑性区长度和平面构件的塑性区面积来衡量构件塑性发展程度。3通过总结现行抗震设计方法和结构抗震性能分析方法的不足,提出了基于能量的抗震性能分析方法,该方法利用塑性变形能在结构间的分布研究结构耗能机制,利用塑性区来定位结构的破坏位置,结合材料损伤分析来衡量破坏程度,并利用了某超高层结构验证了该方法的可行性。4将多自由度体系等效为单自由度体系,利用等效线性化方法计算平稳地震动作用下结构滞变能的随机反应特征,然后基于Markov假设来求解结构的动力可靠度,虽然可以通过这种基于结构滞回能反应来计算结构动力可靠度,但是由于计算过程中存在过多的简化和等效,其精度难以保证。5随机有限元方法是结构可靠度分析的较为精确的方法,具有重要的工程意义,利用前后处理软件GID结合TCL语言及TK图形库对随机有限元软件Opensees进行了可视化处理,形成了随机有限元可靠度分析模块,并利用此软件进行精细有限元模型的可靠度和各随机变量灵敏度分析,提出了利用重要随机变量进行结构可靠度分析的方法。6设计了一系列层数的“强柱弱梁”和“强梁弱柱”两种破坏模式的框架结构模型,建立了基于纤维单元的精细随机有限元模型,模型考虑了混凝土和钢筋对结构的贡献。进行结构体系可靠度分析,“强柱弱梁”体系的可靠性要大于“强梁弱柱”体系的可靠性,提出了基于结构可靠性分析的破坏模式优选方法。
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Even thought 20 years had been passed from Seimic Resistant Code for Building (GBJ11-89) and 7 years for the new version (GB50011-2001) pressed until Wenchuan earthquake in 2008. A great number of death and enjured and eccnomic losses had been coused for the collapse of building. Most of the destroyed buildings are built after 1989 and the collapse reminds us to examine the now used seismic design method and the constructions. We need to do further research on the area before the new version code press. Normally there will be several different structure schemes with different destroyed type. How to select the more reliable scheme has big value. In this dissertation some problems about structural seismic resistant analysis and reliblity based failure mode selective preference will be considered as follows:1 The calculation formula of energy response and energy spectra for elastic and plastic SDOF system had been evaluated. The influence regulation of earthquake factors and structural factors had been studied. 40 earthquake records had been chosen for each site for energy sepectra calculation and a simplified formula had been presented.2 The mode superstation meth and time history caculation of energy response for the simplified storey MDOF system had been evalued and based on that the hystecric energy destrucbution in storeys had been studied. MSC.MARC had been used to establish accurate FEM model and the energy response had been evaluated. The gross energy response and distribution of plastic deformation of reinforced concrete frame and frame-shear wall structure had been studied. The length of plastic area for one dimension members such as beams or columns and the area of plastic area for two dimension members such as shear walls and slabs had been presented for measure the extent of plastic.3 The limitation of the now used seismic resistant method and seismic performance analysis method had been summaried. According to the hysteric test of beams, columns and shear walls, the limitation of the plastic area of the members had been suggested. And joint together with the damage index of material, a new method that energy based seismic analysis method had been presented. The application on a complex tall building of this method verified its feasibility.4 To simplify the MDOF system to SDOF system and applify the equavelent linear method to calculate the scholastic response of hysteric energy response under stable earthquake excitation and then sovle the dynamic reliability basen on the Markov assumpution. Although it can be used to calculate the dynamic reliability based on the hysteric energy response, it is not a accrate way for its simplification and equivalence.5 The stochastic finite element method is valuble for its accuracy in structural system reliability analysis. Visilization programme GID is used with script language TCL and graphics library TK to develop the stochastic finite element method software Opensees. A module is added to GID is called OSReliablility to analysis structural system reliability and sensitivity of stochastic variables with accrate FEM model. A reliablility analysis method with important schositc variables had been approved.6 Two failure mode“columns stronger than beams”and“beams stronger than columns”for frame structures had been designed and the accurate schositic FEM model which consider the concrete and rebar seprately had been established by OSReiliability. By the system reliability analysis we know that the reliability of“columns stronger than beams”is lager than“beams stronger than columns”. Based on which, a method to select a better failure mode with system reliability analysis had been approved.