【作者】 李世翠；

【导师】 刘鸣；

【作者基本信息】 长安大学 ， 结构工程， 2007， 硕士

【摘要】 建筑抗震设计中,结构越高,其基本周期越长,高振型中的长周期振型所占的比率也越大,容易和地震波中的长周期分量发生类共振,所以高振型的影响越显著。因此,在高层建筑抗震设计中考虑高振型的影响,更准确的反映结构在地震作用下的反应势在必行。首先,本文针对振型数选取的研究现状,提出了国内外现有算法的不足,对比了关于振型的几个概念,并对适用范围、计算方法、简化计算模型、振型的选取原则作出了展望。其次,本文通了解50年代后UC Berkeley的结构动力学以及ETABS和SAP程序的开发历史,探究了现有程序里有效质量法。得出质量参与系数是基于基底剪力等效,提出应该增加其他等效原则下的系数(基于位移的等效系数)加以限制更加有必要。再次,本文从振型分解反应谱理论出发探讨了多自由度体系的振型组合法则,指出平方和平方根法(SRSS法)往往比完全二次振型组合法(CQC法)高估计算结果。文中通过对比有效质量与地震力,得出了两者之间隐含的关系。另外,本文对理想框架模型进行了ETABS动力反应谱分析,通过不同烈度、场地、振型数、层数的分析对比,得出他们与振型的选取无关,只会影响响应的值。楼层力、位移随着地震烈度和场地类别的升高而增大,刚度稍有降低;对于平面及竖向布置均比较复杂的结构,各阶振型对基底剪力的贡献并不是随振型序递增而单调递减,对于不同的激励方向,达到要求所需的振型组合数不同。最后,本文对振型选取的影响因素和选取法则作了总结和建议。指出:振型参与系数由结构的振型和外部激励共同决定,质量参与系数与振型参与系数和质量有关,其与烈度、场地无关;选取振型时应该遵循的原则是:试算振型数增加时,底部剪力和顶端位移的误差控制在5%之内的情况下,累计质量参与系数应该大于90%,对于不规则结构,动力荷载参与系数还应大于95%。更多还原

【Abstract】 In the construction seismic design, along with the building’s height increasing, its basic period will be more longer, the long period mode has a big ratio in the higher modes, which will occur analogy sympathetic vibration easy with the long period component in the seismic wave, therefore the influence of higher modes of vibration is more remarkable .So it is important to considering the influence of higher modes of vibration to reflect the responses under the seismic more exactly.Firstly, in this paper, according to present research situation of the reasonable mode number decision, the existing algorithms insufficiency in the domestic and foreign has been pointed out, some concepts of the mode have been contrasted, and also a forecast of the applicable scope, computational method, simplification calculation model, and the mode selection principle has been made.Secondly, by the investigation of structure dynamics research results of UC Berkeley from1950 to 1990, as well as the procedure development history of the ETABS and SAP, the origin and mechanism of the theory of the effective mass method has been delved .Obtained that the modal participating mass ratio is equivalent to the base shear,It is necessary to increase other coefficient (which based on displacement equivalent).Thirdly, the modal combination principle of the multi- degrees of freedom system is discussed in mode-superposition response spectrum method, It is shown that the SRSS law often overestimated the result compared to CQC. From the contrasting of effective mass with seismic load, the connotative relationship between them has been obtained.Moreover, the dynamic response spectrum analysis of an ideal frame model has been carried on by ETABS, with the contrasting of different seismic fortification intensity, site, mode number and layer analysis, conclusion of mode decision having nothing to do with them could be gained, which could only affect the response value. The story shear and displacements increase along with the seismic fortification intensity and site increasing, the story stiffness has been reduced slightly; Regarding to the complex structure, the contribution to the base shear of each mode is not descending along with mode number increasing, the modal combination number is different with different inspirit direction.Finally, some summaries and the suggestions have been made to the influence factor and the decision principle of mode decision. It is pointed out that the mode participation ratio was decided by the mode and exterior inspirit, the modal participating mass ratio is related with modal participation ratio and mass, but not with seismic fortification intensity and site .The decision principle is: the sum of modal participating mass ratio should exceed 90 percent, when the number of mode has a bigger increase, the base shear and top displacement should not has a big increase, the error should be assure below 5 percent, to the irregular structure, the dynamic load participation ratio should be exceed 95 percent.更多还原