Seismic Performance Analysis Of Green High-performance Fiber-reinforced Cementitious Composites Reinforced Frame Structure

Green High-performance Fiber-reinforced Cementitious Composites is a new type of environmental protection material,which is based on the Engineering Cementitious Composites and blended with fly ash to replace cement.Compared with concrete,GHPFRCC has higher tensile strength,toughness and compactness.The seismic performance of the frame structure strengthened by GHPFRCC was studied by experiment and finite element analysis.The main contents were as follows:?1?Two frames were designed,one frame was made of conventional concrete,the other had GHPFRCC joints.Each frame was tested under the low cycle load.These seismic damaged frames were strengthened by GHPFRCC and tested under the low cycle load again to study the effect of GHPFRCC on seismic damaged frames.?2?Based on OpenSees,the effects of material constitution,joint model and bar slip on simulation results were studied to find the optimal modeling.The whole process of the first test of two frames and the second test after reinforcement were simulated.On this basis,the influence of axial compression ratio,beam column linear stiffness ratio and GHPFRCC pouring position on the seismic performance of the frame were studied.The influence of axial compression ratio,reinforcement length and loading times on the seismic performance of the repaired frame were studied as well.?3?PKPM was used for the structural design of 6-story frame.PGA was selected as the ground motion intensity and?_max was selected as the structural damage index.IDA analysis method was used to study the seismic fragility on conventional concrete frame,frame with three-bay GHPFRCC joints and frame with six-bay GHPFRCC joints.Through the experiments and finite element analysis,the main conclusions were as follows:?1?The joint core area of GHPFRCC frame showed the characteristics of fine cracking.The ultimate displacement of GHPFRCC frame were higher than C30 frame.Frame with GHPFRCC joints can impactful improve the seismic behavior of conventional concrete frame.?2?GHPFRCC was used to strengthen the seismic damaged frame,which improved the plastic deformation ability and ductility.The initial stiffness of the strengthened frame was smaller than the original frame.The damage of frame stiffness caused by the first earthquake was very serious.?3?Both the flexible joint and the rigid joint can simulate the hysteretic behavior of the frame under the low cycle repeated load.The simulation results of hysteretic reinforcement model was better than Reinforcing steel model and Steel02 model.The initial stiffness ratio of the hysteretic curve obtained by considering the slip ratio of the longitudinal bar at the bottom of the column was small and the stiffness degradation had better tally with the test result.?4?Under the same axial compression ratio,the maximum bearing capacity and ultimate displacement of GHPFRCC frame were greater than C30 frame.It's suggested that the axial compression ratio of C30 frame should be controlled below 0.5 and GHPFRCC frame should be controlled below 0.7.With the decrease of the linear stiffness ratio of beams and columns,the initial stiffness of the frame became smaller and the stiffness degradation was gradually slow.Pouring GHPFRCC at the bottom of the column can not only improve ultimate displacement of the frame,but also improve the energy dissipation of the frame.?5?The Park-Ang damage model was used to assess damage of the frame.And then the material properties of the damaged frame was reduced,which can better reflect the damage of the structure.Under the same axial compression ratio,the ultimate displacement of the strengthened frame was smaller than the original frame.With the increase of the length of GHPFRCC,the maximum bearing capacity and deformation capacity were increased.It's suggested that the length of GHPFRCC should be within 1-2 times of the section height.?6?Compared with C30 frame,the auto-oscillation period of GHPFRCC frame was increased.The failure probability of GHPFRCC frame was lower than C30 frame.It's suggested that GHPFRCC should be poured in the joint core area of the lower three floors of the frame to improve the seismic performance of the concrete frame.