梁桁体系组合梁静力性能试验研究及有限元分析

Experimental study and finite element analysis on static behavior of composite beam with hybrid full web and truss system

梁桁体系组合梁是一种新型钢-混凝土组合结构,通过对其结构的静力试验研究,分析了其沿截面高度纵向应变、混凝土翼板纵向应变、钢梁腹板应变、腹杆轴向应变随荷载的发展变化及跨中截面挠度变化规律和破坏机理。试验结果表明:组合梁从开始受荷到最终破坏整个过程经历弹性、弹塑性及破坏3个受力阶段,其破坏模式为典型的弯曲破坏;混凝土顶板剪力滞效应较明显,沿截面高度纵向应变发展仍符合平截面假定,在纯弯段内中和轴有明显上移趋势,桁架腹杆为压弯杆件或拉弯杆件;屈服荷载时挠跨比为1/418,极限荷载时挠跨比达到1/54,整体上体现出其具有良好的变形和延性能力。采用ABAQUS软件对与试验梁同尺寸的模型进行有限元分析,验证了试验结果的正确性及有限元模型的合理性;对比分析无倾斜桁架的同尺寸模型,得到梁桁体系组合梁极限承载力相对于无倾斜桁架组合梁提高了20%左右。

The composite beam with hybrid full web and truss system is a new type of steel-concrete composite structure.Through the static experimental study on the structure,the developments of the longitudinal strain along section height,longitudinal strain of concrete flange plate,steel beam web plate strain,web member axial strain with the change of the load were analyzed. And the deflection change as well as failure mechanism of mid-span section were analyzed. The experimental results reveal that the composite beam experiences three different mechanical stages in the whole process from initial loading to final failure,including elastic stage,elastic-plastic stage and failure stage. The beam features the typical flexural failure mode. The shear-lag effect on concrete roof plate is obvious,and the longitudinal strain distribution along the depth of cross-section obeys the plain section assumption. The neutral axis in the pure bending section has a significant upper shift tendency,and the web member of truss is compression bending bar or stretch bending bar. The ratio of the deflection to span is 1 /418 while achieving yield load,and this ratio is 1 /54 while reaching the ultimate load. The overall structure performs well in deformation and ductility. The beam model with identical size of the test beam was built based on ABAQUS nonlinear finite element software to prove the correctness of experimental results and the reasonability of finite element model. The aclinic truss model with the same size of the test one was analyzed and compared with the model to conclude that the ultimate bearing capacity of composite beam with hybrid full web and truss system increases by about 20%compared with composite beam with aclinic truss.