装配整体式预应力钢-混凝土组合梁负弯矩区开裂刚度研究

Cracking stiffness of assembled monolithic steel-prestressed concrete composite beam in negative moment

为量化连续组合梁负弯矩区由于混凝土板开裂而逐渐退出工作导致梁截面的抗弯刚度下降,对4根装配整体式预应力钢-混凝土组合梁、2根装配整体式钢-混凝土组合梁以及2根现浇预应力钢-混凝土组合梁进行静载试验,将试验得到的刚度值与折减刚度法以及采用美国《钢筋混凝土房屋建筑规范》中相关规定计算的刚度进行对比,结果表明:对于装配整体式预应力钢-混凝土组合梁以及现浇预应力钢-混凝土组合梁,由于预应力的存在提高了试件的开裂荷载,减小了混凝土在正常使用荷载作用下的开裂程度,从而导致开裂对其刚度的影响并不明显,采用仅考虑界面滑移的未开裂折减刚度计算值与试验值吻合较好;对于装配整体式钢-混凝土组合梁,美国《钢筋混凝土房屋建筑规范》中的相关规定考虑混凝土受拉刚化效应以及界面滑移效应的刚度计算值与试验结果吻合较好。

In order to quantify the decrease of bending stiffness of the beam section in the negative bending moment region of continuous composite beams when the concrete deck cracks and gradually quiting its work,static load tests were carried out on four assembled monolithic steel-prestressed concrete composite beams, two assembled monolithic steel-concrete composite beams and two steel-cast-in-place prestressed concrete composite beams. The test results of stiffness were compared with calculated value of reduced rigidity method and ‘Building code requirements for reinforced concrete and commentary’. Comparing the calculated values for assembled monolithic steel-prestressed concrete composite beam and steel-cast-in-place-prestressed concrete composite beam, it can be found that the cracking degree of concrete under normal service load is reduced and the influence of cracking on its stiffness is not obvious due to the existence of the prestressed improve the cracking load of specimens. The calculated value of reduced stiffness only considering interface slippage effect before crack agrees well with the test results. For assembled monolithic steel-concrete composite beams, the calculated values of the stiffness taking into account tensile stiffness effect and slippage effect of concrete in ‘Building code requirements for reinforced concrete and commentary’ are in good agreement with the test results.