混杂纤维活性粉末混凝土梁抗剪性能试验研究  

Experimental research on the shear behaviors of hybrid fiber reinforced RPC beams

作　　者：邓宗才[1] 陈春生[2] 陈兴伟[2] 

机构地区：[1]北京工业大学工程抗震与结构诊治北京市重点实验室,北京100124 [2]河北钢铁股份有限公司唐山分公司,河北唐山063016

出　　处：《土木工程学报》2015年第5期51-60,共10页China Civil Engineering Journal

基　　金：国家自然科学基金(51378032);教育部博士点基金(20131103110017);北京市自然科学基金(8142005)

摘　　要：为了研究高强钢筋混杂纤维增强活性粉末混凝土(Hybrid Fiber Reinforced Reactive Powder Concrete,HFRPC)抗剪性能,进行12根HFRPC梁抗剪试验,变化参数包括:剪跨比、配箍率、箍筋强度、箍筋放置角度和纤维掺量等。试验结果表明:混杂纤维显著改善了RPC梁的抗剪变形能力,使梁由脆性剪切破坏变为延性破坏,粗聚烯烃纤维有效阻止了临界斜裂缝的扩展,峰值荷载后承载力下降缓慢,梁斜裂缝条数增多、宽度减小;剪跨比为3.5时,发生了以斜拉破坏为主的剪切破坏;剪跨比增加,承载力下降;高强箍筋屈服,配箍率由0.42%提高到0.64%时,剪跨比为1.5、2.5和3.5,抗剪承载力分别提高22.1%、7.1%和8.1%,再增加配箍率对抗剪承载力的增强作用不大;钢纤维体积率由1%提高到2%,抗剪承载力约提高17.0%。采用现有规范计算梁的抗剪承载力会导致过于保守;法国规范是针对RPC建立的公式,但离散系数大,斜拉破坏时计算值偏不安全。首次提出了剪切韧性指数的概念,以表征混杂纤维增强RPC梁的剪切变形能力和韧性;基于塑性理论,在抗剪承载力公式中首次引入塑性剪切系数,以考虑混杂纤维阻裂、桥联作用和剪跨比对剪切承载力和变形的影响,理论计算值与试验值吻合良好。12 specimens were prepared to investigate the shear performance of Hybrid Fiber Reinforced Reactive Powder Concrete( HFRPC) beams.Variation parameters include:the shear span ratio,reinforcement ratio,stirrup strength,stirrup placement angle and fiber volume.The test results show that:hybrid fibers can significantly improve the RPC beam's shear deformation capacity,turning beam shear failure mode from brittle shear failure to ductile failure.Macro polyolefin fibers can effectively inhibit extension of critical diagonal cracks,slow down the decrease rate of post-peak bearing capacity,increase the number of diagonal cracks,and reduce crack width.When the shear span to effective section height ratio was 3.5,the beams mainly exhibited diagonal tension shear failure.When shear span ratio increased,the bearing capacity decreased,and the high-strength stirrups yielded.When stirrup ratio was increased from0.42% to 0.64%,and the shear span ratio was 1.5,2.5 and 3.5,the shear capacity increased by 22.1%,7.1% and8.1% respectively.Further increasing stirrup ratio for beams with shear compression failure had little effect on the bearing capacity.When steel fiber volume fraction was increased from 1% to 2%,the shear capacity was augmented by about 17%.Existing codes for the calculation of shear capacity of beams give too conservative values.Calculated value obtained using the French specifications for RPC shear formula is not safe for diagonal tension failure beams,and coefficient of variation is large.This paper puts forward the concept of shear toughness index to characterize HFRPC beam shear deformation capacity and toughness.The classical plasticity theory is for the first time modified by introducing plastic shear coefficient into the bearing capacity formula,taking into account the influence of fiber crack resistance,bridging effect and shear span ratio on the shear capacity and diagonal cracks propagation.The theoreticalcalculation results agree well with the test results.

关 键 词：混杂纤维 活性粉末混凝土 抗剪承载力 HRB500 剪跨比 剪切变形 

分 类 号：TU528.572[建筑科学—建筑技术科学]