钢纤维高强混凝土牛腿受剪性能试验研究

Experimental study on shear behavior of high-strength steel fiber reinforced concrete corbel

通过集中竖向荷载作用下9根剪跨比为0.2~0.4、钢纤维体积掺量为0~1.5%钢纤维高强混凝土双面支撑牛腿的受剪性能试验,研究剪跨比、纵筋配筋率、箍筋配筋率、钢纤维掺量对牛腿试件开裂荷载、极限荷载及破坏形态的影响。采用我国GB 50010-2010《混凝土结构设计规范》中牛腿承载力计算方法对9根试件进行计算,并与采用拉压杆模型的规范ACI 318-14、EN 1992-1-1:2004和CSA A23.3-04的计算结果进行对比分析。研究结果表明:小剪跨比混凝土牛腿主要发生斜压破坏和斜剪破坏两种典型破坏形态,随剪跨比增大,牛腿承载力显著减小;提高钢纤维体积掺量,有助于提高牛腿开裂荷载和延性;随着纵向配筋率的提高,牛腿承载力显著提高;提高箍筋配筋率有利于提高牛腿开裂荷载和受剪承载力。由于牛腿同时承受正应力和剪应力的作用,属于复杂受力状态,采用拉压杆模型计算牛腿承载力具有清晰的力学概念,但计算结果较为保守,各参数取值尚需进一步研究;而GB 50010-2010中采用经验公式计算牛腿的受剪承载力,与试验结果较为接近。

Nine double support corbels made of high-strength steel fiber-reinforced concrete( HSSFRC) were tested under concentrated vertical loading to investigate their shear behavior. The specimens were tested with the shear spandepth radio ranging from 0. 2 to 0. 4 and the steel fiber volume ratio ranging from 0% to 1. 5%. The failure process,load-deflection curves and the failure mode were analyzed. The shear behavior of the nine specimens were calculated using the GB 50010-2010 ‘Code for design of concrete structures’,and then the calculation results were compared with the predictions based on the ACI 318-14 code,the EN 1992-1-1: 2004 code and the CSA A23. 3-04 code,in which the strut-and-tie model was adopted. The results show that there are two typical failure patterns for corbel specimens made of high-strength concrete,that is,diagonal compression failure and diagonal shear failure. With the increase of shear span-depth ratio,the ultimate shear load of specimens decreased significantly. With the increase of steel fiber volume ratio,the cracking load and ductility of corbel were improved. With the increase of the longitudinal reinforcement ratio,the bearing capacity of the corbel increased remarkably,and with the increase of the stirrups ratio,the cracking load and the shear bearing capacity of the corbel were improved. Corbels are subjected to combined normal stresses and shear stresses. The strut-and-tie model is based on a clear concept of mechanics for the calculation of bearing capacity,but the results are relatively conservative,and the selection of parameter values needs further research. The code in China( GB 50010-2010) adopts an empirical formula for the shear strength of corbels,which provides relatively close predictions of the test results.