钢筋混凝土板式构件抗扭机理分析

Analysis of reinforced concrete slabs subjected to pure torsion

钢筋混凝土翼板是钢混凝土组合梁的重要组合部分,对组合梁、特别是开口截面组合梁的抗扭贡献很大。对4块钢筋混凝土板式构件进行了纯扭试验。采用变角软化桁架模型,研究了该类构件抵抗纯扭作用的机理。假设纯扭箱梁壁内的剪力流中心线位于有效壁厚中间,并根据有效壁厚定义纵筋和箍筋的配筋率,会低估板式构件的抗扭承载力。假设剪力流中心线与混凝土斜压杆的压应力合力作用线重合,并重新定义相关的配筋率。计算值与试验值吻合良好。在比较已有方法的基础上,回归得到了板式构件极限扭矩公式。

Reinforced concrete flanges are an important component of composite beams, especially for torsional loads. Four reinforced concrete slabs were tested to study their torsional behaviors. The rotating-angle softened truss model underestimated the torsional strength of the test slabs due to the assumption that the shear flow centerline lies in the center of the effective wall thickness. Better results were obtained with the assumption that the shear flow centerline coincides with the centroidal line of the equivalent compression stress block in the concrete struts, and with the new definition of steel ratios. The analytical model accurately predicts not only the torsional strength but also the post-cracking behavior of the specimens. Additionally, a simple design formula has been developed.