变轴力下钢筋混凝土柱的抗震性能分析

ANALYSIS OF EARTHQUAKE-RESISTANT BEHAVIORS OF RC COLUMNS UNDER VARIABLE AXIAL LOADS

准确预测地震作用下钢筋混凝土(RC)柱的受力特性,对评估混凝土结构的抗震性能具有重要意义。地震作用下,混凝土结构中的RC柱除承受水平荷载外,还由于地震作用引起的倾覆力矩影响承受变轴力作用。因此,往复荷载下RC柱受力及变形特性的研究应该考虑变轴力的影响。首先通过恒轴力和变轴力下RC柱滞回性能的模拟,验证了本研究基于纤维模型程序开发的数值分析模型的准确性。然后,利用该数值模型和分析程序,对一RC柱进行了不同变轴力模式下滞回性能的分析研究。分析结果表明,轴力的变化对RC柱的滞回性能有很大影响。由于非耦合型变轴力变化过程的随机性,为便于变轴力下RC柱的抗震性能分析和试验研究,提出了等代定轴力的概念及其确定方法。

Precise prediction for the hysteretic behaviors of reinforced concrete （RC） column under seismic load is important to assess the aseismic performance of RC structures. Due to the overturning moment in the earthquakes, besides being subjected to seismic lateral forces, RC columns also experience variable axial loads. Therefore the influence of variable axial forces must be taken into account when to study the hysteretic behaviors of RC columns under cyclic loads. A numerical analysis model based on a fiber model program has been validated firstly through the rational hysteretie simulations of two RC columns under various patterns of axial loads, Then a frame column has been simulated under various patterns of variable axial loads by numerical method. The analytical results indicate that the variety of axial loads has considerable effect on the hysteretic behaviors of RC columns. Because of the randomness of axial loads and to facilitate canting on experimental researches and analyzing earthquake-resistant behaviors of RC structures, a equivalent fixed axial load method is put forward to determine the seismic behaviors of RC columns in structures under earthquake.