Experimental Study On Ductility Performance Of Reinforced Concrete Beams With 500MPa Steel Bars

The current national standards has promote 500 MPa high-strength steel bas as the priority bar used in constructions, but it is not widespread in practical engineering applications actually, the contractors will only consider 500 MPa high strength bar only when it was a relatively large key project, especially in the local province, which was less. Therefore, it is very necessary to study the mechanical properties of the500MPa-reiforced concrete structures. Some domestic experts and scholars have made some relevant experimental study, but most of the studies were on the performance during normal use, studies on the destruction stage of the concrete structures are relatively lacked. Based on this, this paper carried out an experimental study on the ductility of HRB500-reiforced concrete beams.In this study, a total of six reinforced concrete beams were designed and made to conduct bending failure experiment under uniaxial two-point monotonic loading, in which four beams were configuration with HRB500 steel bars while two beams were configuration with HRB400 steel bars. The section dimension of the specimens is250mm×400mm, and length is 2700 mm while the clear span is 2400 mm with 25 mm concrete cover thickness. The main changing parameters are: the strength of concrete 、 the strength of longitudinal reinforcement and the ratio of longitudinal reinforcement. The concrete strength was divided into two labels: C50 and C70, the ratio of the longitudinal reinforcement is divided into two kinds: 0.982% and 1.473%.The result of the cracking load, plane-section assumption, middle span load-displacement curve, normal section strength were taken into consideration. And the paper also carried out the comparison and analysis of the curvature ductility factor,displacement ductility factor and plastic rotation ability.It is shown from the experimental results that the mechanical performance and failure forms of HRB500 reinforced concrete beams are in common with HRB400 reinforced concrete beams, and they all obey the plane cross-section assumption. The specimens’ flexural bearing capacity increases as the increase of the tensionallongitudinal reinforcement and concrete strength in the case of the same longitudinal reinforcement ratio. Based on the calculation result of the curvature ductility factor,displacement ductility factor and plastic rotation ability, it was found that the ductility coefficient did not increase significantly as the increase of the longitudinal reinforcement strength while the concrete and longitudinal reinforcement strength are the same. But the increase of longitudinal reinforcement strength will improve the flexural bearing capacity to some extent and ensure the component has a certain ductility while the concrete strength and longitudinal strength don’t change, which means using high strength reinforcement is conductive to save material and cost.