Experimental Study And Numerical Simulation Of Mechanical Properties Of Cables Under/after High Temperature

Generally,cable structures are crowded buildings,as a high incidence of building fire occurs.Cable is a common structural component of cable structures.It is of great significance to study the mechanical properties of cable components under high temperature and after high temperature,and provide scientific basis for the fire resistance design of cable structures.In this paper,the research of mechanical properties of high strength steel wire,seven-wires steel strand and cable anchor joint under high temperature and after high temperature were carried out,and the performance of steel strand was simulated by using finite element method.For steel strand and high strength steel wire: the tensile test under three conditions was completed,including under high temperature,after high temperature with/without load.The constitutive relation curves and mechanical properties of high-strength steel wire and steel strand were obtained,and the law of material performance at high temperature was fitted;The creep test of steel wire and steel strand under high temperature was completed,the creep relation curves of steel wire and steel strand were obtained,the creep behavior under high temperature was fitted.The stress distribution of the steel strand was obtained by finite element simulation,and the tensile and creep properties of simulation were compared with the test results.For hot cast anchor joints,the tensile test under high temperature was completed,the curve of tensile property and bearing capacity of cables and joints were obtained,and the law of the whole cable component under high temperature was obtained.These main conclusions were obtained by experiment and analysis:(1)The strength under high temperature of high-strength steel cables started to decreased at 300℃,the strength at 400℃ was about 50% of ordinary strength.And the strength was less than 10% of ordinary strength at 600 degrees,which can be considered as already lose the bearing capacity.The strength after high temperature that over 400℃ began to reduce,and the strength after 700℃ decreased to the minimum value,which is about 30% of ordinary strength.And the degree OF strength reduction increased with the increase of heating time.(2)When the temperature is above 300℃,steel strands occurred obvious creep phenomenon.However,when the temperature is low,the creep deformation would be obvious only when the stress ratio was large.The creep strains at each temperature were power function relations with both the stress ratio and the creep time.(3)Because of the lower melting temperature of casting material,hot cast anchor joint cannot provide reliable anchorage at high temperature.The joint will destroy earlier than the cable and cannot give full play to the bearing capacity of cable material.