Analysis Of Crack Propagation Process Of Reinforced Concrete Beam Considering Bond-slip Between Steel Bar And Concrete

As is known to all,reinforced concrete members are widely used in buildings nowadays.In the process of use,the members are all working with cracks.Taking the simplest three-point bending beam as an example,the previous calculation of ultimate load was based on the plane section assumption and solved the force balance equqtion.But the reality is that it doesn't satisfy the plane section assumption in the mid-span.On the base of previous studies,this thesis focuses on the analysis of fracture process of reinforced concrete beam with precast crack in mid-span.Considering the bond-slip between steel bar and concrete and taking that the net stress intensity factor was zero as the contral equation,combining the deformation coordination,this paper establish a new theoretical calculation model.The local bond-slip model is triliner.It can get the P-CMOD curves to use Matlab to program calculation.And the theoretical curves fit well with the experimental curves.Acording to the P-CMOD curves,we can knew that there are four stages of beam fracture.Firstly,the load increase.Secondly,the load increase to the first peak and begin to decrease.Then,with the expansion of the crack,the load increase again and it will increase to the second peak load.Finally,the load decrease slowly.Use the theoretical calculation model in this paper to analyze the different influence of various factors on the peak load.At the beginning of loading,the bearing capacity of the beam is mainly affected by the performance of concrete.In the late loading period,the bearing capacity of the beam is mainly affected by the performance of reinforcement.The first peak load will increase by increasing the height of beam,the strength grade of concrete and the radius of reinforcement.And it will decrease by increasing the initial crack-height ratio and the cover depth.The second peak load will increase by increasing the height of beam and the radius of reinforcement,and decrease by increasing the cover depth.Calculate and analyze the crack growth resistance of reinforced concrete beams.K_inini has little effect on K_R.At the beginning of loading,the cohesive force has more effect on K_R.And in the late loading period,the steel tensile has more effect on K_R.