异形截面多腔钢管混凝土巨型分叉柱偏压性能试验研究

Experimental study on eccentric compressive behavior of special-shaped multi-cavity mega-bifurcated concrete filled steel tubular columns

为研究多腔钢管混凝土巨型分叉柱不同构造措施对其压弯性能的影响,以北京中国尊为原型,设计了2个1/10缩尺的分叉柱分叉节点区域模型试件,包括原型分叉柱缩尺试件BEC,以及在试件BEC基础上,将下柱顶部区域的拉结钢筋用竖向钢板替换构成的加强试件SEC-2。通过偏心受压试验,考察试件的破坏形态、沿试件高度的侧向位移分布、竖向荷载-侧向位移曲线及骨架曲线、平截面假定的适用性,分析不同构造措施对分叉柱偏心受压性能的影响。基于纤维模型法,编制构件非线性计算程序,钢材采用理想弹塑性本构模型,核心混凝土分别采用GB 50010—2010《混凝土结构设计规范》本构模型（GB模型）、考虑钢管约束效应的Hu本构模型及Han本构模型。计算结果表明：在钢材本构模型不变的情况下,GB模型与Hu模型计算弯矩-曲率曲线与考虑P-δ效应的弯矩-曲率曲线相差较多。Han本构模型计算曲线与考虑P-δ效应的弯矩-曲率曲线的变化趋势一致。改进Han本构模型近似考虑横隔板和多腔钢管对受压区混凝土的组合约束效应,计算曲线与考虑P-δ效应的弯矩-曲率曲线峰值接近,下降段计算弯矩值略低。

To investigate the influences of different detailings on the behavior of multi-cavity mega-bifurcated concrete filled steel tubular （CFST） beam-columns designed based on the China Zun project in Beijing, two specimens with a 1/10 reduced scale of multi-cell mega-bifurcated CFST beam-columns were designed. Specimen BEC was a standard reduced-scale prototype of the beam-columns, and specimen SEC-2 was that with enhanced flexural rigidity of the lower part compared with specimen BEC. Several factors including failure modes, distribution of deflection along height, vertical load-dlsplacement and skeleton curves, and plane cross-section assumption were examined, and the influence of detailings on the performance of the two specimens were investigated via tests. A nonlinear computer algorithm was developed based on fiber models. The stress-strain relationship of steel was elastic-perfectly plastic model. The models considered for the concrete core included that stipulated in the GB 50010-2010 ＇ Code for design of concrete structures＇ (GB model） as well as the Hu＇ s model and Han＇ s model. Using the elastic-perfectly plastic model for steel, the results show that the GB model and the Hu＇ s model have poor consistency with the moment-curvature curves considering flexure second-order effect （P-8 effect）, but the Han＇ s model has a good agreement with them. To study the composite confinement effect of the diaphragms and multi-cavity steel tube at the compressive zone, the modified Han＇s models were used for computing the moment-curvature curves, where a good agreement with the peak value of the moment-curvature curves considering P-δ effect was achieved, although the predicted moment at the descending stage was slightly lower.