【作者】 盛明强；

【导师】 罗奇峰；

【作者基本信息】 同济大学 ， 防灾减灾工程及防护工程， 2008， 博士

【摘要】 破坏性地震会给国家经济建设和人民生命财产安全造成巨大的危害与损失,故强震作用下结构的抗震分析理论和设计方法一直是地震工程界所关注的重要研究课题,也是目前的研究热点之一。一般的抗震设计主要考虑结构的抗震承载力,而基于性能设计方法采用的性能目标一般和结构最大位移或延性相关,但在地震地面运动作用下结构产生破坏的因素除了最大非线性位移外,大量非线性滞回循环引起的塑性累积破坏也是重要的影响因素。基于能量抗震设计方法具有概念清晰、计算简单的优点,较好地反映地震动强度、频谱特性和强震持续时间对结构破坏的影响。目前能量方法中主要采用滞回耗能值来评估结构的破坏程度,本论文在总结前人研究成果的基础上,通过系统的理论研究和大量的计算,分别求得结构在强震作用下的滞回耗能需求值和能力值,初步建立了基于滞回耗能的抗震性能评价方法,并以钢结构和钢筋混凝土框架为算例进行了设计与复核。论文的主要内容如下:1、以单自由度弹塑性体系振动理论为基础,编制结构的能量反应时程分析Matlab程序;按场地类别和强震持时对302条美国Northridge地震和339条台湾ChiChi地震的水平向地震加速度记录进行分类,由非线性程序计算得到结构的平均滞回耗能需求谱;研究了地震动工程特性和结构动力特性对滞回耗能值的影响,分析结果表明屈服强度系数和刚度折减系数对结构的滞回耗能值影响都较小,滞回耗能峰值和地震动加速度峰值的平方大致成正比。2、由等效输入能谱速度峰值放大因子的不同,可分别得到Vidic-Fajfar和Chai-Fajar模式双折线滞回耗能需求谱的数学表达式;由能量反应时程分析结果,可统计分析建立与场地类别和强震持时相关的滞回耗能谱的简化计算公式。比较分析了由以上三种方法求得到的滞回耗能需求谱曲线,结果表明双折线滞回耗能需求谱计算结果偏保守,尤其当结构周期较大时,和时程计算值的差异性较大。3、由修正的Park-Ang损伤模型和低周疲劳破坏模型可分别推导出对应于结构破坏时的滞回耗能能力值。在滞回耗能能力值的计算公式中,除了相应的经验系数外,单调位移延性系数由结构非线性静力推覆分析得到,循环位移延性系数由结构的强度折减系数得到。4、归纳整理了12种不同的等效体系方案(ESS),求解结构的滞回耗能需求值时可避免做复杂繁琐的多自由度体系(MDOF)非线性时程分析。为分析不同ESS的等效效果,首先采用经验公式或非线性推覆分析方法可求得实际多自由度体系的层剪计算模型,再由自编Matlab程序计算结构MDOF和等效单自由度体系(ESDOF)的能量反应,得到ESS的耗能比值。结果分析表明,场地特征和滞回耗能标准值对ESS的耗能比值有重要的影响,对所有典型地震波的耗能比值做非线性回归分析,便可分别得到与场地a/v值和耗能标准值S_E相关的耗能比值Rh的数学表达式。5、实际多自由度结构对应于不同恢复力模型,本论文分别选用了适合于钢结构、砌体结构和钢筋混凝土结构的双线型、半退化三线型和退化三线型三种恢复力模型,编制相应Matlab计算程序,准确求得对应的滞回耗能需求谱和耗能比值。相比较于双线型模型,三线型模型可考虑刚度退化现象,更真实地反应了钢筋混凝土和砌体结构的受力特性。6、由结构能量平衡思想,建立基于滞回耗能的结构能量反应判别式,从而可判断在强震作用下结构是否发生破坏。修正Park-Ang损伤模型的损伤指数可表征结构的破坏程度,则业主要求的结构性能水平对应于特定的损伤指数,故可得到对应于特定性能目标的结构滞回耗能能力值,从而初步建立考虑滞回耗能的基于性能抗震设计与复核过程。7、为将以上分析成果应用于实际结构的抗震评价与设计中,分别以钢结构和钢筋混凝土框架为例,计算其在强震作用下的滞回耗能需求值和能力值,便可判断结构是否会出现倒塌或预定性能目标,通过二次设计得到合适的构件和钢筋配置等参数。更多还原

【Abstract】 Ruinous earthquake will cause great destruction and damage on the national economy and property, even lead to death. Therefore the seismic analysis and design of structure under strong earthquake is the significant research subject and hotspot on seismic engineering. Normal seismic design mainly considers the carrying capacity of structure. The performance target of performance-based design mostly is concerned with ultimate displacement or ductility. Ultimate displacement contributes to the destruction of buildings basically, so does cumulative damage which is caused by nonlinear hysteretic cycles. Performance-based seismic design procedure possesses several advantages, such as clear in conception and simple in computation, which can preferably represent the influence of earthquake intensity, frequency character and ground motion duration on the structural destruction. At present energy-based design procedure mainly adopt hysteretic energy to evaluate structural damage degree. The dissertation computes hysteretic energy demand and capacity of structures under severe earthquake respectively by the means of sum-up of former research fruits, systemic academic investigation and large numbers of computation. Therefore hysteretic energy-based seismic evaluating procedure is built primarily, and uses steel frame and concrete frame as example in design and check. The main contents of this dissertation are described as follows:1. On the basis of vibrational theory of single degree of freedom elastic-plastic system, a Matlab time-history analysis program is made to compute the structural energy response. 302 Northridge in USA and 339 ChiChi in Taiwan earthquake ground motion records are classified according to soil condition and duration of strong ground motion, and their mean hysteretic energy demand spectra is computed by means of nonlinear program. The result shows that force reduction factor and stiffness reduction factor have little influence on the hysteretic energy values, and peak hysteretic energy is proportional to the square of peak ground motion acceleration approximately.2. The bilinear hysteretic energy demand spectrum mathematical equations of Vidic-Fajfar and Chai-Fajar model are developed because of different velocity peak amplification factor of equivalent seismic input energy spectrum. Through the energy response result of time-history analysis, a simple formulation of hysteretic energy is proposed by means of nonlinear regression analysis, in which site character and duration of strong ground motion are considered. Former three kinds of demand spectrum are compared, and bilinear hysteretic energy demand spectrum is conservative. Especially for large structural period, bilinear hysteretic energy demand values are much larger than the time-history response values.3. The hysteretic energy capacity which corresponds to structural collapse state can be calculated from modified Park-Ang damage model and low-cycles fatigue model. The monotonic displacement ductility factor can be calculated through nonlinear static Push-over, and the cyclic displacement ductility factor can be calculated through the structural force-reduction factor too.4. The structural hysteretic energy demand can be calculated through 12 kinds of different equivalent system scheme(ESS), which can avoid of complicated and time-consuming nonlinear time-history analysis of multi degree of freedom(MDOF) system. In order to analyze equivalent effect of different ESS, the floor-shear model should be built by experiential formulae or nonlinear Push-over firstly. The energy response of MDOF and equivalent single degree of freedom (ESDOF)systems can be computed by self-compiling Matlab programs. Therefore it is convenient to acquire hysteretic energy ratios of ESS. The result indicates that site characters and normal hysteretic energy have significant influence on the hysteretic energy ratios. Consequently the hysteretic energy ratios expressed by site characters(value a/v) and normal hysteretic energy(S_E) can be calculated by means of nonlinear regression analysis of the hysteretic energy ratios produced by typical earthquake waves.5. Real multi degree of freedom structures correspond to different hysteretic models. This dissertation uses bilinear, semi-degraded trilinear and degraded trilinear hysteretic models which can represent the steel frame, brickwork and concrete structures respectively well. By means of Matlab program, corresponding hysteretic energy demand and energy ratio is calculated precisely. Compared to bilinear model, trilinear models can consider stiffness degradation which reflects the mechanical characters of reinforce concrete and brickwork structures more truly.6. Hysteretic energy-based design checking equation is built via energy equilibrium ideology to judge whether the building will collapse. The damage index of modified Park-Ang damage model quantifying structural damage can mark the structural performance target which is required by owners. Then the hysteretic energy capacity can be computed to create the elementary performance-base seismic designing and checking procedure considering hysteretic energy.7. In order to make use of former analysis in the seismic evaluation and design of real structure, steel frame and concrete frame are chosen as examples. Their hysteretic energy demand and capacity values under strong earthquake are calculated to judge whether the collapse or target performance will happen. Via second design we can obtain suitable components and reinforcing steel bar etc.更多还原