带混凝土翼板的圆管上翼缘钢-混凝土组合梁抗弯性能

考虑不同加载方式与下翼缘宽度, 对3根带混凝土翼板的圆管翼缘钢-混凝土组合梁进行抗弯性能试验, 分析了试验梁的抗弯承载性能与破坏形态; 基于试验梁的抗弯特征, 推导了组合梁屈服弯矩和极限弯矩简化计算公式。研究结果表明: 试验梁均发生典型的塑性弯曲破坏, 稳定性良好; 达到极限承载力时, 梁端处上翼缘钢管与混凝土翼板相对滑移均小于0.43 mm, 试验梁体现了良好的协同工作性能; 随下翼缘宽度的增加, 试验梁刚度与承载力增大, 对于下翼缘宽度分别为150、260、300 mm的试验梁, 其屈服弯矩的比值为1∶1.44∶1.55, 极限承载力的比值为1∶1.31∶1.40;随着试验梁承受弯矩的增大, 当中性轴上升至混凝土翼板时, 钢管混凝土处于受拉状态, 可不考虑钢管与内填混凝土的套箍效应, 而当塑性中性轴位于上翼缘钢管混凝土内时, 可不计入该套箍作用对极限抗弯承载力的影响, 但其可促进延性的继续发展; 试验梁的位移延性系数均大于3.35, 延性较好; 屈服弯矩、极限弯矩理论计算值与试验值的比值分别为1.02~1.04、0.96~1.03, 吻合良好, 因此, 所出提出的简化理论计算公式简单、可靠。 

Bending performance of circle tubular up-flange steel and concrete composite girder with concrete flange

The different loading methods and widths of bottom flange were considered, the bending behavior experiments were conducted for 3 circle tubular up-flange steel and concrete composite girders with concrete flange, and their bending performances and failure modes were analyzed. Based on the bending characteristics of test girders, the simplified formulas of yielding moment and ultimate moment of composite girder were derived. Research result shows that all test girders fail in typically plastic bending mode and have satisfied stability. When attaining the ultimate capacity, the measured slips between the upper flange steel tube and concrete flange are no more than 0.43 mm at the beam ends, which shows the excellent overall working ability for the test beams. The stiffness and bending capacity of test girder increase with increasing the width of bottom flange. The width of bottom flange is 150, 260, and 300 mm, respectively, the corresponding ratio of yield moments is 1∶ 1.44∶ 1.55, and the ratio of ultimate bending capacities is 1∶ 1.31∶ 1.40. With the bending moment of test girder increasing, when the plastic neutral axis rises to the concrete flange, the concrete filled steel tubular flange is in tension, and the confinement effect between the steel tube and inner filled concrete may be neglected. When the plastic neutral axis locates in the up-flange concrete filled steel tube, the confinement effect between the steel tube and inner filled concrete may be neglected in the calculation of ultimate bending capacity, but it may enhance the ductility of test girder. The displacement ductility coefficients of test girders are all greater than 3.35, therefore, the test girders have good ductility. The ratios of theoretical to experimental values of yield bending moment and ultimate bending moment are between 1.02 and 1.04, and between 0.96 and 1.03, respectively, which shows good agreement between the theoretical calculation results and test results. Thus, the simplified theoretical formulas are simple and reliable.