Influence Of Initial Stress On Bearing Capacity Of Increasing Concrete Arch Ring

With the continuous increase of traffic volume and the low standard of design load,the bridge diseases are increasing.Therefore,there are more and more bridges with insufficient bearing capacity.Masonry arch bridge is one of them.The reinforcement of arch ring by enlarging section method has also become a common reinforcement method.Although there are studies on the bearing capacity of arch bridge after reinforcement,there are still insufficient studies on the calculation of the bearing capacity of arch ring reinforced by enlarging section method.In this paper,the arch ring reinforced by enlarging section method is taken as the research object,and the influence of different initial stresses on the bearing capacity of the arch ring reinforced by enlarging section method is studied by combining theoretical analysis,model test and numerical simulation.(1)The calculation method of compressive bearing capacity of reinforced arch ring based on internal force distribution and limit state was proposed,and the four-stage stress analysis model of arch ring in unilateral reinforcement was constructed.Taking the equivalent elastic modulus of old and new concrete after increasing section as the breakthrough point,the calculation formula of compressive bearing capacity of arch ring with increased cross-section based on internal force distribution and limit state was presented.(2)The compression test of short concrete columns was carried out by unilateral reinforcement method.The compression tests of 18 short columns with unilateral increased cross-section under different initial stresses were carried out.The breakdown phenomenon and stress characteristics of reinforced columns with enlarged section under different initial stresses showed that the failure of specimens under different initial stresses was mainly caused by the formation of longitudinal transverse crack.Compared with the one-time casting specimens,the ultimate bearing capacity of reinforced short concrete columns decreases with the increase of initial stress,but the decrease slowed down when the initial stress level exceeded 0.4.(3)The numerical analysis of bearing capacity of reinforced columns with increased cross-section under different initial stresses was performed.The temperature difference method was used to simulate the initial stress state,and the finite element model of concrete reinforced columns under different initial stresses was established.The parameter expansion of the axial and eccentric loading of the model was realized.The finite element simulation value was compared with the test value and the theoretical value.The analysis show that the average error between the theoretical value and the finite element value under axial compression is about 5 %.When the initial stress level exceeds0.7,the bearing capacity of the composite section will decrease with the increase of the initial stress level.The average error between the theoretical value and the finite element value under eccentric compression is about 3 %,which verifies the correctness of the calculation formula for the bearing capacity of the composite section of the reinforced arch ring in this paper.The research results of this paper have a reference for the calculation of bearing capacity of masonry arch bridge after arch ring reinforcement.