| Reactive powder concrete(RPC)is a new building material with ultra-high strength and excellent durability,which has a broad application prospect in Bridges,construction projects and protective engineering.The bearing mechanism of RPC beam on inclined section is different from that of ordinary concrete because RPC component has no coarse aggregate and fibers are distributed in random direction.Under fire,the internal material of RPC beam deteriorates,and the stress state of flexo-shear section is complex,which is easy to occur thermal-mechanical coupling burst.At the same temperature,the thermal conductivity of RPC is about 0.8 W/(m·K)higher than that of ordinary concrete,which accelerates the attenuation of inclined section resistance.In view of the safety risk of RPC beam under inclined section load in fire,the damage assessment method of PRC beam after fire is not clear.This thesis adopts the method of experimental research to carry out the bearing performance test of RPC beam on the inclined section under fire action.The research results can provide reference for the bearing safety of RPC beam on the inclined section under fire and the reinforcement and repair after fire.This thesis mainly carried out the following work:1.In order to find out the law of bearing performance degradation of RPC beam at inclined section under fire,6 specimens of RPC beam with simple support were designed and produced.First,ISO834 standard fire test under constant load was carried out,and data such as time-displacement curve,load-displacement curve,internal temperature change,crack development,failure pattern and high temperature burst were obtained.The influences of shear span ratio,load level,stirrup ratio and longitudinal reinforcement ratio on the bearing performance of RPC beam under fire were analyzed.The results show that the shear span ratio and load level are the key factors affecting the fire resistance of RPC beam in inclined section.When the shear span ratio increases from 2.5 to 3.5 and the load level increases from 0.25 to0.45,the fire resistance of RPC beam can be reduced for more than 30 minutes.The hoop ratio has a significant effect on the bearing capacity and fire resistance of RPC beam.The ratio of longitudinal reinforcement has little effect on the fire resistance of RPC beam.Fire high temperature and burst weakened the bearing performance of RPC beam’s inclined section.The burst caused the internal materials to be directly exposed to fire and accelerated the deterioration of mechanical properties,which reduced the bearing capacity of the beam’s inclined section by more than 33.5%.2.Shear tests were carried out on specimens damaged by fire at normal temperature,and data such as load-displacement curve,crack development and failure pattern of specimens were obtained.The effects of fire time,shear span ratio,stirrup ratio and longitudinal reinforcement ratio on the residual bearing performance of RPC beam at oblique section after fire were compared and analyzed.The results show that the vertical deformation of RPC beam can be divided into three stages: elastic stage,elastoplastic stage and shear failure stage.The fire time and shear span ratio are the main factors affecting the residual shear capacity of RPC beam after fire.When the fire time was increased by 30 min,the shear span ratio increased from 2.5 to 3.5,and the maximum reduction of the remaining shear capacity of RPC beam after fire was 38.4%.In a certain range,with the decrease of stirrup ratio,the reduction of residual shear capacity of specimens after fire is greater,and the reduction of RPC beams without abdominal reinforcement is greater than that of RPC beams with abdominal reinforcement.With the increase of reinforcement ratio of longitudinal reinforcement,the residual shear capacity of RPC beam after fire increases,and the deflection at the loading point decreases. |
