异形多腔钢管混凝土分叉短柱抗震性能试验及数值计算

Seismic behaviour test and numerical calculation on special-shaped bifurcatedCFT short column with multiple cavities

针对某超高层巨型框架结构中异形截面多腔钢管混凝土(concrete-filled steel tube, CFT)分叉柱,为研究截面加强构造对分叉短柱抗震性能的影响,进行了4个试件在竖向轴压力及水平往复两次的低周反复荷载下的抗震性能试验研究,试件上部为五边形四腔体钢管混凝土双柱肢,下部为八边形十三腔体钢管混凝土单柱肢,以此形成分叉柱;研究的截面构造包括四种:基本构造,钢管钢板整体加厚构造,距中和轴较远的钢管角部钢板内表面贴焊等肢角钢的局部钢板加厚构造,距中和轴较远的钢管腔体内置圆钢管构造。基于试验结果及截面构造特点,进行了数值计算。试验及数值计算结果表明:异形截面多腔钢管混凝土分叉短柱的破坏主要发生在上柱根部分叉截面处,表现为距离中性轴较远处的钢板撕裂以及局部焊缝开裂引起的整块钢板撕裂;内置圆钢管的加强构造承载力提高7.6%、变形能力提高14.4%,综合耗能能力最强,局部钢板加强构造承载力提高9.2%、变形能力下降18.7%,钢管钢板整体加厚构造承载力略有提高、但变形能力下降较多;提出的异形多腔钢管混凝土柱简化建模方法计算效率较高,精度满足工程设计要求。

Focusing on special-shaped bifurcated concrete-filled steel tube(CFT)column with multiple cavities of mega-frame structures in super high-rise buildings,in order to investigate the influence of cross-sectional enhanced structures on the seismic behavior of the bifurcated short column,four specimens subjected to vertical axial load and horizontal twice loaded cyclic loading were tested.The upper part of the specimen includes two pentagonal CFT column branch with four cavities,while the lower part includes one octagonal CFT column branch with 13 cavities.As a result,a bifurcated column was formed.The investigated cross-sectional structures weredivided into four types:basic type,the type that the thickness of the whole tube steel plate is increased,the type that the thickness of local steel plate being far from the neutral axis is increased by welding steel angle,and the type that circular steel tube is encased in the cavities being far from the neutral axis.Based on the test results and the characteristics of section structures,numerical calculation was conducted.The test and simulation results show that for special-shaped bifurcated CFT short column,the failure mostly appears at the root part of the upper column branches on the bifurcated cross section.The main failure exhibits the tear of the steel plate far from the neutral axis and the tear of whole steel plate caused by the crack of local welding seam.The bearing capacity of the enhanced structure of encasing circular steel tube increases by 7.6%,while the deformability increases by 14.4%,and best energy dissipation ability shows.The bearing capacity of the enhanced structure of increasing thickness of local steel tube increases by 9.2%,but the deformability decreases by 18.7%.The bearing capacity of the enhanced structure of increasing thickness of all steel tube little increases,while the deformability significantly decreases.The proposed simplified finite element model for special-shaped bifurcated CFT short column with multiple cavities exhibits well efficiency.And the accuracy can satisfy the demand of engineering design.