钢-UHPC华夫板组合梁抗剪性能试验研究

Experimental Study on Shear Behaviors of Steel-UHPC Composite Beams with Waffle Slab

为研究钢-UHPC华夫板组合梁在静载作用下的竖向抗剪性能,对4个组合梁试件进行了静力试验,主要变化参数包括华夫板平板厚度、肋的高度、翼板宽度。通过分析试件破坏过程、荷载-跨中挠度曲线、应变分布规律,对不同参数下试件的破坏模式和承载能力进行研究。研究结果表明:试件共有剪切破坏和剪切、弯曲复合破坏2种破坏模式;与普通组合梁不同的是,由于钢纤维的"桥接作用",UHPC翼板剪切开裂后呈现多条剪切裂缝同时开展现象,主裂缝周围出现大量细而密的微小剪切斜裂缝,钢纤维显著提高了组合梁的抗剪承载力和变形能力;华夫板纵、横肋的设计削弱了组合梁的整体工作性能,在几何突变处出现应力集中现象,使得此处率先发生纵向开裂;对比试件SUW1和SUW2,保持华夫板整体高度不变,将肋高占华夫板高度比例从50%提高到67%时,承载力下降了3.2%,但变形能力提高了85.8%;对比试件SUW2和SUW3,保持平板厚度保持不变,将肋的高度从60mm增加到90mm时,承载力提高了22.5%,但变形能力下降了48.6%;对比试件SUW1和SUW4,将翼板宽度提高47.3%时,承载力和变形能力分别提高了19.0%和48.5%;提出综合考虑纵肋与钢纤维影响的钢-UHPC华夫板组合梁抗剪承载力计算公式,理论计算值与试验值吻合良好。

To investigate the shear behaviors of steel-UHPC waffle composite beams,static tests were conducted on four composite beam specimens with main variables such as heights of plates and ribs and width of the slab.The failure process was analyzed,then the load-deflection curves and strain distribution of the specimens,and the failure modes and ultimate shear resistance of the specimens under different parameters were examined.The results show that the specimens fail in shear mode and combined shear and flexure mode.Unlike ordinary composite beams,because of the bridging action of steel fibers,multiple shear cracks are found in the UHPC slab after shear cracking,and a large number of fine and dense micro-shear cracks appear around the critical crack.The steel fibers have a significant effect on improving the shear resistance and deformation capacity of the composite beams.The design of the longitudinal and transverse ribs of the waffle slab weakens the overall working performance of the composite beam,and stress concentration occurs at regions with abrupt geometrical changes;this causes longitudinal cracking to occur first.With a constant total depth of the UHPC waffle slab,increasing the depth of the rib from 50%to 67%of the total depth reduces the ultimate load-carrying capacity of the composite beam by 3.2%,but the deformation capacity increases by 85.8%.With a constant depth of the plate,by increasing the depth of the rib from 60 mm to 90 mm,the ultimate resistance of the composite beam increases by 22.5%,but the deformation capacity reduces by48.6%.An increase of 47.3%of the width of the UHPC slab results in 19.0%and 48.5%increases in shear resistance and deformation capacity,respectively.Considering the contribution of the longitudinal rib and the steel fibers,a formula for the shear resistance of the steel-UHPC waffle composite beam is proposed.The theoretically calculated results agree well with the test results.