| The coupling beam has the function of connecting the wall limbs on both sides,increasing the structural stiffness and dissipating the seismic energy,has important significance for aseismic,but ordinary even beam deformation and energy dissipation ability is poorer,scholars at home and abroad to improve the seismic performance of coupling beam a large amount of experimental study and theoretical analysis,the study included to improve the seismic behavior of coupling beam method and test and theoretical analysis of the stress mechanism of coupling beam.As a new type of green material,fiber reinforced concrete has the characteristics of high strength,good ductility and strong energy dissipation capacity,which can significantly improve the ductility and energy dissipation capacity of the structure.In this paper,based on the previous research on FRC material properties,in order to improve the seismic performance of small-span high-ratio composite beams,the SPHFC small-span high-ratio composite beams were designed and fabricated by using Steel-polyvinyl Alcohol Hybird Fiber Concrete(SPHFC)as the matrix material,the pseudo-static experiment was carried out,and the numerical calculation and theoretical analysis were combinedand.The influence of fiber reinforced concrete strength and section width on the seismic performance of coupled beams is studied.The main research contents and results are as follows:(1)The quasi-static tests were carried out on four coupling beams with small span-to-depth ratio,including three SPHFC coupling beams and one ordinary concrete coupling beam.The influence of SPHFC material strength and beam section width on the seismic performance of SPHFC coupling beam is analyzed from the failure phenomenon,shear bearing capacity,displacement ductility coefficient,energy dissipation capacity,shear compression ratio limit,bearing capacity degradation,stiffness degradation and reinforcement strain.The results show that using SPHFC as the matrix material can effectively improve the shear capacity,ductility and energy dissipation capacity of the beam,and make the beam transition from shear failure to bending failure.As the compressive strength of the SPHFC cube increases from88.9MPa to 132.3MPa,the shear capacity of the coupling beam increases by 6.5%,the displacement ductility coefficient and energy dissipation capacity decrease by 3% and6.2%,respectively.When the width of the section increases from 120 mm to 150 mm,the shear capacity of the beam increases by 10.9%,the ductility coefficient decreases by21.8%,the energy consumption capacity was increased by 52.45%.Compared with CB-7 using FRC(Fiber Reinforced Concrete),the CB-2 using SPHFC in this paper can more effectively improve the ductility and energy dissipation capacity of coupling beam with small span-to-depth ratio,and the descending end of the skeleton curve of the SPHFC beam is more gentle than that of the FRC beam,so it can bear the load smoothly.(2)The finite element model was established to analyze the SPHFC coupling beam with small span-to-depth ratio,Firstly,the validity of the model was verified,and then the effects of different span-to-depth ratio,stirrup ratio and longitudinal reinforcement ratio on the performance of the connected beams were studied.The analysis shows that with the increase of the span-to-depth ratio from 1.0 to 1.5,2.0 and2.5,the ductility of the beam increases by 21.7%,38.1% and 47.2%,and the ultimate displacement increases by 15.5mm,17.44 mm and 21.17 mm,respectively,while the peak load decreases by 16.0%,25.1% and 35.8%.When the hoop ratio increases from0.42% to 0.56%,0.84%,1.12% and 1.68%,the peak load increases by 6.1%,16.4%,22.1% and 30.1%,respectively,the ductility coefficient increases by 26.0%,41.1%,53.9% and 62.8%,respectively,and the failure displacement increases by 4.13 mm,13.69 mm,16.97 mm and 20.43 mm.The increase of the ratio of longitudinal reinforcement has little effect on the bearing capacity and ductility.In addition,it is proposed that the inclined stirrups should be arranged in the beam to enhance the shear capacity of the beam.Through the finite element simulation,it can be concluded that the reasonable arrangement of the inclined stirrups can improve the shear capacity,ductility and failure displacement of the beam.(3)Based on China’s "Code for Design of Concrete Structures"(GB50010-2010),the shear capacity of the continuous beam in this paper is calculated and the calculated value is in good agreement with the test value.The correct path of force transmission should be selected to improve the accuracy of calculation when using the tension-compression bar model recommended by ACI 318-19 to calculate the bearing capacity.Multiple regression method is used to calculate the test values of the shear capacity of 36 common reinforced fiber reinforced concrete beams with small span-to-depth ratio,and formula for calculating the shear capacity are established. |
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