Experimental Study On Shear Performance Of Steel Beams Wrapped By Reinforced Reactive Powder Concrete Under Load

The reinforcement method of steel beam wrapped by reinforced Reactive Powder Concrete（RPC）while under load is a new and practical strengthening technique for layouting reinforcement and pouring RPC under the condition of steel beam holding load.The reinforcement technology basically does not affect the normal production and life during construction,can effectively solve the problem of poor fire resistance and corrosion resistance of steel beam,and significantly improve the stiffness,bearing capacity and energy dissipation performance of steel beam.At present,there is no precedent for the study of the shear strength of steel beam warpped by reinforced RPC under secondary load,and there is a lack of relevant theory and a more accurate formula for calculating the bearing capacity.In this paper,a comprehensive and systematic study is made on the shear performance of the reinforced composite members by means of experimental study,theoretical analysis and finite element simulation:（1）Experimental study.Static shearing tests were conducted on five full-scale steel beams wrapped by RPC and one comparative steel beam.Then,the effect of wrapped RPC on the bearing capacity under secondary load and the rigidity of the steel beam was researched.Finally,the influence of shear span-to-depth ratio,initial load,and steel ratio on the enhancement effect was analyzed.Based on the test results the shear bearing capacity,failure mode,deflection and strain were analyzed to explain the failure mechanism,which provided the experimental and theoretical basis for the subsequent establishment of shear formula.The results showed that the maximum increase times of the shear bearing capacity of reinfoeced beam reached 2.8,section stiffness is improved significantly,and the enhancement effect is significant.The enhancement effect of wrapped RPC is better for sections with larger steel ration.（2）Calculation of shear strength.The three relevant current codes and regulations in China are calculated by using the measured values of specimen materials,meanwhile,the calculation errors are analyzed.Considering the tensile strength of steel fiber at the inclined crack and the reduction of RPC compressive strength,the formulas for calculating shear capacity of the reinforced beams oblique section with the simple strength superposition method and the truss-arch model with or without considering the strength of RPC constraint in different areas are presented based on the test data and the analysis results.The calculated results are in good agreement with the test data,which can provide a theoretical basis for reinforcement engineering.In order to popularize the reinforcement technology,the reinforcement technology of reinforced RPC with shear reinforced independent steel beam and steel beam with floor slab on top are presented respectively.（3）Simulation analysis.Using the software of ABAQUS to simulate and analyze specimens,the shear reinforcement model was established by using the technique of birth-death element considering the initial load of section steel.Then,the post-processing results were mutually verified with the test results from the load-deflection curves,cracks damage,stress distribution and ultimate bearing capacity.On the whole,the model was established reasonably and could effectively simulate the mechanical properties of the reinforced beam.Finally,based on the reinforcement model,steel ration of the section steel web,initial load and shear span-to-depth ratio were extended to analyze.The analysis results verified the influence of parameters on the shear performance of the specimens and put forward corresponding reinforcement suggestions.