Shear Performance Of HRB500 Reinforcement Reactive Powder Concrete Beam

Reactive powder concrete(RPC)was a kind of ultra high performance cement-based composite material invented by Bouygues laboratory in France at the end of last century.In design of reinforced RPC component,the mechanical properties of reinforcement should be improved to give full play to the performance of RPC.HRB500 grade reinforcement had higher strength.In order to give full play to the materials,RPC and HRB500 grade reinforcement were combined together.It had great practical significance to research the performance of their joint work.To study the shear capacity of RPC beams with HRB500 reinforcement which worked on concentrated load,fourteen HRB500 reinforced RPC beams were tested.The influence of shear span ratio,steel fiber content,stirrup ratio,reinforcement ratio and reinforcement strength was considered.By observing experimental phenomena and analyzing test data,the influence of these factors on cracking load,shear capacity and shear ductility was obtained.The shear mechanism of RPC beam and the matching of two kinds of materials in the joint work of shear resistance were discussed.The theoretical model of the ultimate capacity and the calculation formula for the engineering application were derived.And established the analysis model of the whole process of section work.The main research results were as follows:(1)Fourteen HRB500 reinforcement RPC beams with different shear span ratio,steel fiber volume ratio,stirrup ratio,reinforcement ratio and reinforcement strength were fabricated and tested.The crack development and the failure mode were observed.Results show:The bridging effect of steel fiber can effectively hinder the development of cracks and increase the cracking load and shear ductility.There is no match between HRB500 reinforcement and RPC without steel fiber.The reduction of the shear capacity is much greater than the decrease of the material strength.When stirrup ratio is not high,there is a main inclined crack from the support point to the loading point.In other words,before the failure of the component,the shear crack has been extended near the loading point,and there is no compression zone at the end of the test beam.Otherwise,there is no obvious main inclined crack.It distributes dispersion.Because of the high strength properties of RPC,the influence of the shear span ratio on the failure state is different with the ordinary concrete beam.When the shear span ratio of the beam is 1.51,it shows the characteristics of baroclinic failure and When the shear span ratio of the beam is 3.02,it still shows the characteristics of shear compression failure.(2)The experimental data of reinforcement strain,stirrup strain,RPC strain and deflection were analyse.The effects on cracking load,ultimate load and shear ductility were obtained.The shear mechanism of reinforced RPC beam was analysed.Results show:Among the various influencing factors,shear span ratio has a great influence on the ultimate capacity,the inclination angle of the main inclined crack and the failure mode.Stirrup ratio has a great influence on the distribution of oblique cracks.Steel fiber content has the most obvious influence on the ductility of the test beam.The shear capacity decreases with the increase of shear span ratio,and increases with the increase of stirrup ratio,steel fiber volume ratio,reinforcement ratio and reinforcement strength.When the volume ratio of steel fiber is increased from 0 to 2%and the stirrup ratio is increased from 0.25%to 0.75%,the ductility of the beam can be improved obviously.Steel fiber can only partially replace stirrups.The main components of the flexural shear capacity of RPC beam include the vertical component of the steel fiber "tractive force",the shear capacity of the stirrup,the shear capacity of RPC at the top of the inclined crack,and the bolt action of the reinforcement.In the limit state,the first,two factors contribute most to the shear capacity,and the latter two are affected by the shear span ratio and the stirrup ratio.(3)Based on plasticity theory,the shear capacity calculation model of reinforced RPC beam was established.Simplified formulas for engineering design were given.It was compared with the current domestic and international norms to find the applicability of the formula.Results show:Based on the plasticity theory,the contribution of steel fiber to the material can be well considered.It is assumed that the plastic hinge line is the connection of the bearing to the loading point to the components with moderate shear span ratio and low stirrup ratio.The plastic coefficient is considered as a combination of the plastic properties of the material and the effect of the pin reinforcement.A large number of experimental data are needed for further regression analysis.It can influence the trend of the calculation result.RPC beams need to draw on the applicability of formulas in current codes.(4)Based on MCFT,the analysis model of the reinforced RPC beam subjected to bending shear was established.The variation law of the average stress and strain of the beam with the shear force was calculated and the ultimate capacity was obtained and compared with the experimental results.Based on this,the whole experiment was analysed.Results show:The analytical model based on MCFT can well simulate the process that the RPC beam works on bending and shearing.RPC has no coarse aggregate but contains steel fibers.In calculating the balance of forces across cracks,the joint action between the cracks in the cracks is replaced by the traction of steel fibers.RPC tension constitutive relations play an important effect on the precision of calculation.It can not only affect the prediction of cracking load value,but also explain the cause of cracking theoretically.It can also estimate the average tensile stress remaining at the time of failure and create conditions for a more accurate prediction of its ductility.