Study On The Enhanced Shear Performance Of Deep T-section Concrete Beams Reinforced By Near Surface Mounted CFRP

Recent decades,skyscrapers,underground constructions,bridges and railways are building more and faster in the world benefiting from the techniques of deep T-section beam structures.However,the improvement of the effective bearing capacity of deep T-section beams is still a difficult problem since the load capacity of deep T-beam structures is limited by shear force,which is complex and complicated.With the development of Carbon Fiber Reinforced Polymer technique,a surface mounted CFRP method to solve this problem is then proposed by researchers.They make slots in the concrete protective layer and put CFRP plates or ribs in the slots and then bond them with epoxy resin Adhesive.This method has the advantages of high reinforcement efficiency and of good durability.Though the method is promising for complex structures in civil engineering,researches on the shear capacity of the CFRP strengthened deep T-section beam by this method is relatively less and imperfect.In this paper,finite element method and experiment are used to analyze the shear strength of deep T-beams before and after the strengthening.Based on ANSYS software,the shear capacity and the strain field of the test beam are obtained before the experimental test.Combined with the existing shear capacity of deep T-section beam as well as the bearing capacity theory of the surface mounted CFRP technique,the mechanical properties of the beams before and after the strengthening are studied.And then the data testing and CFRP mounting scheme for experiment are determined.More specifically,the shear failure behaviors of deep T-section beams with two types of working conditions(before and after CFRP reinforcement)are experimentally studied by three-point bending tests.Moreover,the digital image correlation(DIC)technique is adopted to monitor the surface deformation and failure of the beam.The experimental results show that the shear strengths of the deep T-section beam strengthened with CFRP are improved significantly.During the loading process,it is found that the crack speed of the test beam after reinforcement is reduced than that of the reference beam,and so does the maximum slanting crack width.Moreover,the surface stress of the beam after the CFRP reinforcement is reduced.In addition,the surface strain field of the test beam is analyzed by DIC technique.Comparing the experimental results with the finite element model and with the existing theoretical formulae,it is found that the stress field of the finite element simulation is nearly consistent with the theoretical formula,and the shear strain diagram of the finite element simulation is nearly consistent with that of the DIC.Finally,based on the test results and finite element simulation,we modified the existing formula via a correction coefficient for better estimate the reinforcement in engineering practice.