翼缘非等厚矩形钢管混凝土梁受弯性能研究

Flexural behavior of concrete-filled rectangular steel tube beams with non-identical thickness flanges

为了研究翼缘非等厚矩形钢管混凝土梁的受力性能,进行了7根钢管混凝土梁的四点弯曲试验,试件的变化参数为钢管上、下翼缘厚度和混凝土强度。结果表明,钢管上下翼缘厚度之比越小,承载力极限状态下的截面中性轴越靠下,表明参与工作的混凝土越多,组合截面承载性能越好;当上下翼缘厚度之比约为1/3时,通过提高混凝土的强度能有效增大构件的受弯承载力。采用有限元软件ABAQUS对受弯试验进行了全过程模拟,得到的结果与试验结果吻合。模拟分析还表明,优化后的翼缘非等厚矩形钢管混凝土截面不仅增大了钢管分担的弯矩,同时也增加了混凝土的工作面积,两者共同作用提升了构件的受弯承载力,当含钢率约为0.2时,承载力相较于等壁厚构件可提升15%以上。在平截面假定的基础上推导了翼缘非等厚矩形钢管混凝土组合截面受弯承载力的解析表达式,并探讨了对构件截面的优化问题,特别对含钢率较高的高强混凝土构件,优化截面的承载力提高效果显著。研究结果表明,翼缘非等厚矩形钢管混凝土梁具有良好的承载性能和变形性能。

To study the mechanical behavior of concrete-fflled rectangular steel tube （CFST） beams with differences in flange thickness, four-point bending tests on 7 CFST beams were conducted. The primary parameters of specimens were thickness of top and bottom steel flanges and concrete strength. The results indicate that a smaller top-to-bottom flange thickness ratio leads to a lowered location of the neutral axis under the ultimate state, which means that more concrete contributes to the flexural resistance of the composite cross-section. When the flange thickness ratio is about 1/3, increasing concrete strength can effectively improve the bending capacity of the beams. Finite element program ABAQUS has been used to simulate the whole process of the tests, and the numerical results agree well with test results. Simulation analysis indicates that an optimized thickness ratio can not only increase the moment carried by the steel tube but also increase the working area of the concrete core, both of which improve the bending capacity of the members. When the steel ratio is about O. 2, the bearing capacity of the optimized section can be more than 15% higher than the identical thickness one. An analytical expression for the bending capacity of CFST beams with non-identical thickness flanges was derived based on the plane cross-section assumption, and in addition, the optimization issue of the cross-section was discussed. In particular, for high strength concrete members with a large steel ratio, the optimal section design can improve the bearing capacity remarkably. The research indicates that CFST beams with non- identical thickness flanges have satisfactory bearing and deformation capacity.