| In recent years,with the rapid development of the metallurgical industry,the production process and technology of the residual heat-treated steel bars have made remarkable progress.The production quality is stable and the performance is improved compared with the previous ones.It has been applied in civil engineering fields in developed countries such as Europe and America.FRP rib is a new type of building material with the advantages of light weight,high strength,insulation and corrosion resistance.The experimental study on the bending behavior of the beams with the heat-treated steel bars and the FRP bars is carried out.It is found that the bending mechanical properties of the mixed-reinforced concrete beams are similar to those of ordinary reinforced concrete beams,indicating that the kind of reinforcement is feasible.However,during the test,it is also found that the mixed reinforced concrete beams have the disadvantages of early cracking and faster crack growth.In order to solve these problems,steel fiber is added to the concrete to carry out the experimental study on the bending behavior of the mixed-section steel fiber concrete beam in this paper.The main research contents and conclusions are as follows:(1)The normal section bending test of five residual heat-treated steel and GFRP mixed steel fiber reinforced concrete beams is carried out.It is found that the crack distribution pattern of mixed reinforced concrete beams is similar to that of ordinary steel fiber reinforced concrete beams.And increases with the steel fiber volume fraction,the crack distribution of the beam is more uniform and the number of cracks is reduced.The addition of steel fiber can effectively inhibit the crack initiation of the beam and improve the cracking load and the flexural bearing capacity.Under the condition that the volume of steel fiber is constant,the increase of the proportion of GFRP reinforcement tends to have little effect on the cracking load and ultimate bending moment of the mixed reinforcement beam,but it has obvious inhibitory effect on the crack and deflection development of the hybrid reinforcement beam after the yield of the residual heat reinforcement.(2)Aiming at the reinforcement ratio of the mixed reinforcement steel fiber reinforced concrete beam,the nominal reinforcement ratio according to the elastic modulus conversion and the strength conversion is proposed,and the two boundary failure states of the mixed reinforcement steel fiber reinforced concrete beam are defined,and according to the flat section assumption,the range of reinforcement ratios for the damage of the ribs is derive.(3)Considering the tensile behavior of steel fiber reinforced concrete,the ultimate bending moment and cracking moment formula of the mixed reinforced steel fiber reinforced concrete beam are derived.Based on the calculated theoretical values and the experimental measured values,it is found that the two agree well.(4)Referring to the formula of beam deflection and crack width in "Code for Design of Concrete Structures",and consider the influence of bond-slip between GFRP bars and concrete during the bending process of mixed reinforcement steel fiber reinforced concrete beams,the formula of the average crack spacing,deflection and maximum crack width of mixed reinforcement steel fiber reinforced concrete beams are derived.And compared with the experimental results,the calculated values of the deflection and crack width formulas in the normal use state are in good agreement with the actual values.(5)The finite element model of the five beams is established by ABAQUS simulation software.The deflection and failure modes of the five beams were analyzed by the model calculation results,and the finite element simulation values are compared with the measured values.The results show that the finite element simulation values are close to the measured values,and the established finite element models can better simulate the actual force of the mixed reinforcement beams. |
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