箍筋约束再生混凝土力学行为分析

Analysis on mechanic behavior of recycled aggregate concrete confined with stirrups

通过箍筋约束再生混凝土方形截面短柱动态力学性能试验,获取动态单调荷载下约束再生混凝土单轴受压应力-应变关系全曲线;不同箍筋约束和应变率下,约束再生混凝土应力-应变关系曲线的上升段基本一致,而下降段差异较为明显,随着体积配箍率的提高,下降段曲线明显随之趋于平缓,随着应变率的提高,下降段曲线随之变陡。在外荷载作用下,当箍筋约束再生混凝土达到峰值应力时,箍筋应力仍低于屈服强度;再生混凝土通过箍筋约束后,很大程度上解决了再生混凝土延性比普通混凝土延性较低的问题。随着箍筋约束效应或应变率的增加,受压峰值应力均随之增加。根据应力-应变曲线特征点参数变化规律,初步提出约束再生混凝土受压峰值应力动态约束因子模型。随着体积配箍率的提高或箍筋间距的减小,箍筋约束效应对动态约束因子的贡献均随之增加。

Based on dynamic mechanical experimental tests of recycled aggregate concrete(RAC)short columns with square cross section confined by transverse hoops,the uniaxial compressive strain-strain complete curves of confined recycled aggregate concrete(CRAC)under dynamic monotonic loading conditions were obtained.It is found that,for the uniaxial compressive strain-stress complete curves of CRAC,the ascending portions of the curve are basically consistent with each other under various hoop reinforcement confinements or strain rates.However,the descending branches exhibit obvious differences.With the increase of the volume stirrup ratio,the descending branch changes obviously in a flattening trend.However,with the increase of the strain rate,the descending branch changes in a steepening trend.Under the action of the external loads,while the stress of CRAC approaches the compression strength,the stress of the transvers hoop reinforcement has not reached the yield strength.Through the confinement of the transvers reinforcement,the ductility of RAC,which is slightly lower than that of natural aggregate concrete(NAC),is significantly improved.With increasing amplitude of strain rate or the improvement of the confinement,the compressive peak stress of CRAC is increased.According to the changing law of the characteristic parameters related to the stress-strain curve,the models of dynamic confining increase factor(DCIF)for the compressive peak stress of CRAC is initially proposed.With the increase of the volume stirrup ratio or the decrease of the spacing of the hoop,the contribution of the confinement of transverse hoop reinforcement to DCIF increases.