Shear Resistant Performance Investigation Of Precast Segmental Bridge Columns

The segment concrete of precast segmental bridge column is discontinuous at the joint,which are the weakness of the whole bridge column.But there is little research on the shear behavior of the joints between the columns.Therefore,in this paper,the shear resistance performance of precast segmental bridge column joints was studied,and the research works and conclusions were as follows:(1)Experimental studyFive pairs of bridge column segment joint specimens were designed and fabricated.The experimental parameters included confining stress,section shape,with or without shear keys,key number and geometry.Through the monotonic direct shear tests of the precast segmental bridge column joints,shear force-shear displacement curves and shear strength,strain of outer surface of concrete,failure mechanism and failure mode of the joints were recorded.The results showed that: The failure modes of the specimens with shear keys were the shear keys sheared off and alveolar cracking,and shear keys sheared off one bye one;The failure modes of flat joints were the relative slip and tension cracks;The shear capacity of joints increased with increasing confining stress and the shear key number;The shear capacity of specimens with hollow section was lower than the shear capacity of specimens with solid section.(2)Finite element simulationThe finite element models of ten joint specimens were established by ABAQUS finite element software.The results showed that: The shear force-shear displacement curves of the finite element simulation and actual test results were in good agreement,and the shear capacity were also similar;The stress was mainly concentrated in the shear key parts,and the strain was mainly concentrated at the root of the shear keys;The failure modes of the joints from finite element simulation were consistent with the experiments,and the fracture process of the shear keys could be well represented;At high confining stress,the friction coefficient in the AASHTO specification should be reduced.(3)Theoretical analysisThe fracture rule of the shear keys was summarized,and the fracture mechanism of the shear key was defined,the shear keys always fractured at the root parts.Shear strength formulas of joins were summarized,the experimental data in this paper and three other groups experimental data were used to compare the formulas.Based on Mohr stress circle,the shear strength formula was deduced,and when the diagonal strut model angle was 45o,the results were more accurate.With the linear regression of the experimental data from this paper and three other groups of experimental data,three new formulas for shear strength of dry joints were obtained.Based on the above four groups of data,the new shear strength formulas of dry joints were confirmed.