密实截面组合梁的竖向抗剪强度Ⅰ:受正弯矩作用的组合梁

Vertical shear strength of composite beams with compact steel sections. Part Ⅰ: Composite beams subjected to sagging moment

挖掘混凝土翼板的抗剪潜力,充分利用钢-混凝土组合梁的组合抗剪作用,有利于进一步提高组合梁的经济效益。采用通用有限元程序ABAQUS 6.5,对密实截面组合梁正弯矩区的弯剪强度问题进行研究。分析结果表明,提出的有限元分析方法,特别是钢-混凝土的界面模型,可以准确预测组合梁的弯剪强度,同时对组合梁的变形刚度也可以较准确地模拟。在此基础上,利用有限元方法,对混凝土翼板截面尺寸、剪力连接程度、剪跨比等参数进行计算分析,回归得到考虑剪力连接程度影响的组合梁竖向抗剪强度计算公式。研究发现,在正弯矩区段,组合梁抗剪强度相对于钢梁腹板抗剪名义值的提高,不仅来源于混凝土翼板的抗剪作用,组合作用的贡献也很显著;采用建议的抗剪强度公式,可以不考虑简支组合梁弯矩与剪力的相互影响。

It could yield a more efficient and rational design of steel-concrete composite beams if the contribution of concrete slab and composite action to the vertical shear strength is accounted for.In this paper,a three-dimensional FE model,using the general-purpose finite element software,ABAQUS version 6.5,has been developed to investigate the strength of composite beams with compact steel sections under combined sagging bending and shear.Through analyzing several specimens available in the literature,it may predict the ultimate strength and the entire load-deformation history of composite beams to an acceptable degree of accuracy.This verified model is then employed to study the parameters that influence the shear capacity of composite beams,such as the dimension of concrete slab,the degree of shear connection,the shear span aspect ratio,etc.It is shown that the vertical shear strength of composite beams is higher than that of steel beams,due to the contribution of concrete slab and the composite action.Based on the numerical results,empirical formulae that incorporate the effect of the shear connection degree are proposed to obtain the vertical shear strength of composite beams subjected to sagging moment.It is also found that the interaction between bending and shear strength in a simply-supported composite beam can be neglected when using the proposed formulae.