火灾下活性粉末混凝土梁斜截面承载性能研究

Study on Load-Carrying Properties of Inclined Section of Reactive Powder Concrete Beam Under Fire

为探明火灾下活性粉末混凝土(Receative power concrete,RPC)梁斜截面承载性能退化规律,设计制作了六根RPC简支梁试件,开展了恒载下ISO834标准火灾试验,获得了时间-位移曲线、荷载-位移曲线、内部温度变化、裂缝开展、破坏形态、高温爆裂等数据,分析了剪跨比、荷载水平、配箍率、纵筋配筋率对火灾下RPC梁斜截面承载性能的影响规律。结果表明:剪跨比、荷载水平是影响RPC梁斜截面耐火极限的关键因素,剪跨比由2.5增至3.5,荷载水平由0.25增至0.45,RPC梁耐火极限可降低30 min以上;配箍率对RPC梁的斜截面承载力和耐火极限影响显著;纵筋配筋率对RPC梁耐火极限影响甚微。火灾高温、爆裂削弱了RPC梁的斜截面承载性能,爆裂导致内部材料直接受火,加速其力学性能劣化,使梁斜截面承载力降低33.5%以上。该研究可为火灾下RPC梁斜截面承载安全及火灾后加固修复提供参考。

In order to find out the degradation law of the bearing capacity of the inclined section of reactive power concrete(RPC)beams under fire,six RPC simply supported beam specimens were designed and made,and ISO834 standard fire tests were carried out under dead load.Data such as time-displacement curve,load-displacement curve,internal temperature variation,crack development,failure pattern and high temperature bursting were obtained.The influences of shear-span ratio,load level,hoop ratio and longitudinal reinforcement ratio on the bearing performance of RPC beam in oblique section under fire were analyzed.The results show that the shear span ratio and load level are the key factors affecting the fire resistance limit of RPC beam.When the shear span ratio increases from 2.5 to 3.5 and the load level increases from 0.25 to 0.45,the fire resistance limit of RPC beam can be reduced for more than 30 min.The stirrup ratio has a significant effect on the oblique bearing capacity and fire resistance limit of RPC beams.The reinforcement ratio of longitudinal reinforcement has little influence on the fire resistance limit of RPC beams.Fire high temperature and burst weakened the oblique section bearing capacity of RPC beams.The burst caused the internal materials to be directly subjected to fire,which accelerated the deterioration of mechanical properties and reduced the oblique section bearing capacity of beams by more than 33.5%.The research results can provide reference for the bearing safety of oblique section of RPC beam under fire and the reinforcement and repair after fire.