基于多目标性能的高强钢组合K形偏心支撑框架塑性设计方法研究

Plastic design method for high-strength steel composite K-eccentrically braced frames based on multi-objective performance

高强钢组合K形偏心支撑框架结构(K-HSS-EBFs)作为一种典型的双重抗侧力体系,可以实现结构抗震设计中多道设防的目标。针对传统K-HSS-EBFs性能设计方法中无法考虑多水准抗震设防目标以及支撑-框架体系剪力分配的问题,对基于多目标性能的K-HSS-EBFs塑性设计方法进行修正。通过考虑结构后屈服刚度变化得到K-HSS-EBFs的三折线能力曲线,采用能量平衡原理计算支撑-框架体系在不同性能目标下的弹性和弹塑性剪力分配,从而对结构进行弹塑性设计。采用修正的设计方法设计了一个6层的K-HSS-EBFs结构算例,建立OpenSees有限元模型,选取20条地震波对其进行不同强度地震作用下的弹塑性时程分析。结果表明:采用所提设计方法设计的K-HSS-EBFs实现了结构预期的破坏模式以及不同强度地震作用下的位移延性需求和剪力分布模式;从多遇地震到罕遇地震,算例模型中框架跨所承担的基底剪力占比由29%提高到44%,满足GB 50011—2010《建筑抗震设计规范》中对于多道设防体系内力重分布后的结构总基底剪力分配要求。

High-strength steel composite K-eccentrically braced frames(K-HSS-EBFs),as a typical double lateral force resisting system,can achieve the aim of multi-stage fortification in seismic design.Considering that the performance design method for traditional K-HSS-EBFs cannot achieve the multi-stage seismic fortification objectives,and the issue related to the shear distribution of brace-frame system,a modified K-HSS-EBFs plastic design method based on multi-objective performance was proposed.The trilinear capacity curve of K-HSS-EBFs was obtained by considering the change of yield stiffness of the structure.The energy balance principle was used to calculate the elastic and elastic-plastic shear distribution of the braced-frame system under different performance objectives,so as to carry out the elastic-plastic design of the K-HSS-EBFs.A 6-story K-HSS-EBF structure was designed using the modified design method.20 seismic waves were selected to analyze the elastic-plastic time history of the finite element model established in OpenSees.The results show that the K-HSS-EBFs designed by the proposed design method can achieve the expected failure mode and the displacement ductility demand and shear distribution mode under different seismic intensities.From frequent to rare intensity earthquakes,the proportion of the base shear resisted by the frame span in the model is increased from 29%to 44%,which meets the multi-stage fortification requirements stipulated in GB 50011—2010 regarding the distribution of the total base shear of the structure after internal force redistribution.