预制装配式楼盖水平地震作用计算方法

Analysis method for horizontal seismic action of precast concrete floors

针对预制装配式楼盖,按照合理的楼盖水平地震作用计算方法进行设计,可保证抗侧力主体结构破坏前楼盖保持水平传力的整体性。利用有限元软件(ETABS)对某5层框架结构模型进行中、大震弹塑性时程分析,并与底部剪力法、ASCE7-10推荐的经验放大法计算值进行对比,发现时程分析所得加速度值比后两种方法计算值偏大,说明用底部剪力法、经验放大法计算楼盖水平地震作用并进行连接设计存在安全隐患。基于ASCE7-16,考虑中美抗震区划及场地类别等差异,提出与中国抗震设计规范协调并考虑高阶振型影响的模态叠加法。针对不同地震烈度,利用提出的计算方法进行算例分析,计算结果表明:楼层加速度放大系数k沿建筑高度分布趋势一致;楼盖中震下实际水平地震作用SEhk中和大震下实际水平地震作用SEhk大分别能满足γEhSEhk中≤Rd/γRE和SEhk大≤Rk,即用所提方法计算楼盖水平地震作用并进行连接设计,楼盖可达到“中震弹性、大震不屈服”的性能目标。

This paper proposes a reasonable method for calculating the horizontal seismic action of precast concrete floors.This method can be used to ensure the integrity of these kinds of floors to transfer the horizontal force caused by earthquakes.Firstly,a typical 5-story frame structure model is built for further analysis.The acceleration values obtained by the elastoplastic time-history analysis are larger than those calculated using the equivalent lateral force(ELF)method or empirical amplification(EA)method which was proposed by ASCE 7-10.Therefore,both the ELF and EA methods underestimate the horizontal acceleration(i.e.,horizontal seismic action)of the floors,which would lead to unsafe design in engineering practice.Secondly,the modal superposition(MS)method is proposed,in which the key parameters specified by ASCE7-16 were employed and modified to coordinate with the requirements of the seismic design codes in China.The MS method is employed for calculating the accelerations of the 5-story model in different seismic intensity areas.Lastly,the analysis results were compared with those obtained from the elastoplastic time-history analysis,which indicates that the amplification coefficients of the floor acceleration(k)have a similar distribution trend along with the building height.Moreover,the precast concrete floors designed using the MS method could meet the seismic performance objective“Keep elastic under moderate earthquake and unyielding under rare earthquake”.