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本文对高层建筑的振型作了分析研究,以现行抗震规范为基础,根据高层建筑的特点、实测和工程实算结果的一些数据,引入某些假设,对等截面悬臂杆的弯剪振型作了分析。文中对高振型组合的个数、高振型周期T_i(j=2、3、4、5)与基本周期T_1的比值对振型值的影响,短周期和长周期对“鞭击”效应影响的规律,“鞭击”效应在各类场地土上的反应进行了分析。通过分析得知:影响振动特性的并非只是建筑物的自振周期,而是T_1/R(T_1为建筑物的基本周期,对于Ⅰ、Ⅱ、Ⅲ类场地土,R分别等于0.2、0.3、0.7);就振型系数而论,振型组合个数的增多,在建筑物的中部振型系数反会减小;就地震力计算而言,以考虑四个振型组合为宜;建筑物的周期比减小,将会加大“鞭击”效应;T_1/R=1时,“鞭击”效应不显著,T_1/R=5时,“鞭击”效应达到最大。T_1R再大时,“鞭击”效应反而减小。最后,通过一些简化,提出实用计算法。
In this paper, the vibration mode of high-rise buildings is analyzed and researched. Based on the current seismic code, some assumptions are introduced based on the characteristics of high-rise buildings, actual measurement and actual engineering results, and the bending and shear modes of cantilever beams with equal section are introduced. Analyzed. The effect of the number of high vibration type combinations, the ratio of the high mode period T_i (j=2, 3, 4, 5) and the fundamental period T_1 on the mode value, the short- and long-cycle effects on the “whiplash” effect The law of influence, the “whiplash” effect was analyzed in various types of field soil reactions. Through analysis, it is known that not only the period of vibration of the building but T_1/R (T_1 is the basic cycle of the building), but R, which is equal to 0.2, 0.3, and 0.7, respectively, for class I, II, and III site soils. In terms of mode factor, the increase in the number of mode combinations will reduce the mode shape coefficient in the central part of the building; in terms of seismic force calculation, it is appropriate to consider four mode combinations; The reduction of the cycle ratio will increase the “whiplash” effect; when T_1/R=1, the “whiplash” effect is not significant, and when T_1/R=5, the “whiplash” effect reaches its maximum. When T_1R is greater, the “whiplash” effect decreases. Finally, through some simplifications, a practical calculation method is proposed.