Experimental Study On Seismic Performance Of Polypropylene Fiber Lithium Slag Concrete Columns Under Thecoupling Of Load And Saline Soil

In saline soil areas,In saline soil area,reinforced concrete structures are susceptible to erosion,which leads to its insufficient durability and degradation of mechanical properties.The hidden danger of reinforced concrete structure in service under strong earthquake is very prominent.As the main force-bearing member of the structure,the seismic performance of concrete columns determines the safety of the overall structure.However,ordinary concrete columns have disadvantages such as poor ductility,low tensile strength,and high brittleness,which is easy to be destroyed under the action of earthquake.In order to better improve the seismic performance of concrete columns corroded by saline soil and provide test data and theoretical basis for the seismic fortification of structures in saline soil area,this paper uses polypropylene fiber(PPF)and lithium slag as reinforcement materials to carry out the experimental study on the seismic performance of polypropylene fiber lithium slag concrete columns(PFRC)under load saline soil environment coupling.Three groups of 11 columns under the coupling of 0 d,90 d and 180 d saline soil erosion and different stress ratio are tested to simulate saline soil environmental erosion under load,and the pseudo-static test is carried out under different axial compression ratios.The test phenomena,hysteretic characteristics and skeleton curve characteristics are analyzed.The influence of test parameters(polypropylene fiber and lithium slag,erosion time,axial compression ratio,stress ratio)on the seismic performance of columns is studied by using ductility,energy consumption,stiffness degradation and other evaluation indexes,and the restoring force model of polypropylene fiber lithium slag concrete column under saline soil erosion is proposed.And the results show that:(1)The energy consumption capacity of PFRC before and after erosion is greater than that of ordinary concrete columns.With the increase of the erosion time of saline soil,the energy consumption capacity of PFRC members gradually decreases.In general,the energy dissipation capacity of PFRC is inverse proportional to the axial compression ratio in the early stage of erosion,and increase with the increase of axial compression ratio in the late stage of erosion.Coupling load has little effect on energy dissipation capacity of PFRC.(2)The ductility of PFRC before and after erosion is better than that of ordinary concrete columns.The ductility of PFRC decreases with the increase of stress ratio.The ductility of PFRC in saline soil is inversely proportional to the axial compression ratio.Under the erosion of saline soil,the ductility of PFRC and ordinary concrete columns decreased.(3)The seismic performance of the specimens mixed with PPF is better.As the axial compression ratio increases,the hysteresis curve of the member in saline soil environment gradually shrinks,the ultimate bearing capacity increases,and the descending section drops sharply.After erosion,the bearing capacity of PFRC is close to that of RC,even greater than RC.The addition of polypropylene fiber and lithium slag can improve the initial stiffness of concrete in saline soil.The initial stiffness of PFRC increases with the increase of axial compression ratio.With the increase of stress ratio,the initial stiffness of PFRC decreases.The initial stiffness of PFRC increases with the increase of erosion days,and the erosion days have little effect on the stiffness degradation rate of PFRC.(4)The addition of polypropylene fiber and lithium slag can improve the crack resistance of concrete in saline soil environment.At the same time,with the increase of stress ratio,the crack resistance capacity of PFRC first increases and then decreases.With the increase of axial compression ratio,the initial crack load of PFRC without erosion increases,and the crack resistance capacity of PFRC decreases with the increase of axial compression ratio.With the increase of erosion days,the anti cracking performance of PFRC and ordinary concrete columns decreases.(5)A three-fold line skeleton curve model is proposed.Compared with the actual test results,it can better reflect the characteristics of the force process at each stage of the component.Through the nonlinear regression analysis,the stiffness degradation law of each stage is obtained.Combined with the hysteretic law,the restoring force model of polypropylene fiber lithium slag concrete column in saline soil environment is established,which provides a reference for its elastic-plastic analysis.