Research On Mechanical Performance And Design Method Of Reinforced Concrete Structure Strengthened With High Strength Steel Strip

The transverse reinforcement exerted on concrete components can effectively enhance the ultimate compressive strength and ultimate deformation capacity of concrete and improve the bearing capacity and deformation performance of components.Therefore,the reinforcement technology with high strength steel strips is proposed,and a series of experimental studies and theoretical analysis have been completed including beams,columns and joints in this study.The main contents and results are as follows:(1)Fifty-four specimens of cylindrical columns and square columns were tested under axial compression.The effect of steel strip spacing and layer number on the bearing capacity and deformation capacity were investigated.Experimental results show that the concrete column specimens with high strength steel strips can effectively improve the bearing capacity under axial compression.Not only the bearing capacity of columns under axial compression can be improved,but also the deformation capacity can be improved as well.Based on the experimental results,the mechanism of the concrete column with high strength steel strips are discussed.The ultimate strength model of cylinder concrete column and the equations for the bearing capacity calculation of square concrete columns with high strength steel strips under axial compression are proposed.(2)Ten specimens of reinforced short columns were tested under low cyclic loading.The effects of strip spacing,layer number and shear span ratio on bearingcapacity and deformation capacity were investigated.Experimental results show that the development of cracks in reinforced components becomes slow.Once the peak load is reached,cracks keep developing and less concrete is spalling due to the reinforcement of steel strips,and the load decreases slowly.Eventually,the bearing capacity of the reinforced specimens increases by about 20%-30%.The ductility coefficient increases by 30%-80%.The displacement angle of the reinforced specimens exceeds the requirement of 1/50.Based on the experimental study,the shear mechanism of the short concrete column with high strength steel strip is analyzed.The restraint influence coefficient of high strength steel strip on concrete strength is introduced,and the equations for the shear capacity calculation of concrete short columns with high strength steel stripe are proposed.(3)Four specimens of reinforced frame columns with high axial compression ratio were tested under low cyclic loading.The effects of steel strip spacing and axial compression ratio on bearing capacity and deformation capacity were investigated.Experimental results show that the cracking of the reinforced specimens is delayed and the cracks are developed thoroughly.The concrete material properties are fully used and the deformation capacity of the component is greatly improved.Compared with the unreinforced specimens,the load-displacement hysteresis curve shape is full.At the peak load,the skeleton curve for the reinforced specimens decreases slowly.Under the same axial compression ratio,the ductility coefficient of specimens JGC2 and JGC4 increased by 107.79% and 122.51% respectively.Under the higher axial compression ratio,the ductility coefficient of specimen JGC3 increases by about 32.9%.Based on the experimental study,the regression analysis and theoretical analysis were carried out on the experiment data,and a three-line restoring force model of reinforced frame column with high strength steel belt was presented.(4)Shear tests were carried out on seven specimens of reinforced beams.The effects of steel strip spacing and layer number and shear span ratio on the bearing capacity and deformation capacity were investigated.Experimental results show that several main oblique cracks are formed in the bending and shearing sections of the reinforced specimens.Additionally,more cracks are observed,which leads to the shear failure and diagonal compression failure ultimately.The ultimate bearing capacity isincreased by 50%~90% and the deformation capacity is increased by 70%~170%.Based on the experimental study,the shear mechanism of reinforced concrete beams with high strength steel strips is discussed further.The equations for the shear capacity calculation of reinforced concrete beams with high strength steel strips are proposed.(5)Nine specimens of concrete joints with pre-stressed steel strip,bonded steel and steel strip-bonded steel combination were tested under low cyclic loading.The effects of axial compression ratio,steel strip spacing,layer number and different reinforcement methods on bearing capacity and deformation capacity were investigated.Experimental results show that the shear failure modes of the core zone of the reinforced specimens with high strength steel strips are improved effectively.The bearing capacity is increased by 3.1%~11.4% and the ductility coefficient is increased by 4.7%~21%.The shear bearing capacity and initial stiffness of the joints can be effectively improved by the corner bonded steel reinforcement.Based on the experimental study,the shear mechanism of reinforced concrete joints with high strength steel strips is discussed further,the equations for the shear capacity calculation of reinforced concrete beam-column joints with high strength steel band-bonded steel combination is proposed.(6)Seven specimens of high-strength concrete joints with high strength steel strips were tested under low cyclic loading.The effects of the spacing at the end of beams,layer number of steel strips,the spacing of steel strips in the core area,the location of reinforcement of high strength steel strips and the type of joints on the failure modes and deformation capacity of the joints were investigated.Experimental results show that the failure mode of reinforced specimens is changed from joint shear failure to beam-end bending failure.The ductility coefficient of reinforced specimens is increased by about 3.1%~22.2%.The seismic performance is improved greatly and the energy dissipation is increased.The degradation of strength and stiffness is improved greatly.The maximum shear Angle of the reinforced specimens decreased obviously,and The maximum reduction of specimen JG-JQ1 was 45.90%,and the factors affecting the maximum shear angle of the reinforced specimen joints are analyzed.