| With the development of high-rise buildings and the in-depth study of new materials in recent years,the Steel Reinforced Concrete and Reactive Powder Concrete have attracted the attention of scholars.Reactive powder concrete(RPC)instead of ordinary concrete in steel reinforced concrete structure,not only inherits the form of steel reinforced concrete structure perfect advantages of high bearing capacity,stiffness big,good seismic performance,also can further improve its corrosion resistance performance,reduce component cross section size,prolong the service life of components,improve the economic benefit.Therefore,SRRPC has a good application and development prospect.Nowadays,scholars have done many research on the properties of steel reinforced concrete composite structures at and after high temperature.The reaction and failure mechanism of steel reinforced concrete composite structures under high temperature conditions are revealed and many important results are obtained.In spite of this,the research on SRRPC structure at home and abroad is still at the stage of room temperature,and there is no relevant literature to study its performance at high temperature.Under the same fire condition,due to its high steel content,the reactive steel concrete is more seriously damaged than other structural members.Therefore,it is very valuable to study the high temperature performance of SRRPC.Based on the experiments of seven steel reinforced reactive powder concrete specimens at different temperatures(20?-600?),The influence factors of bond performance at high temperature,the relation curve of load and slip during the test,and the experimental phenomena and failure forms of SRRPC specimens at high temperature were investigated.It provides theoretical support for the development of fire resistance design theory of steel reinforced reactive powder concrete structures under fire and the basis for fire damage assessment.Through the analysis of SRRPC push-out test results at high temperature and theoretical derivation,it can be known that the section failure pattern of SRRPC specimen at the loading end and the free end is basically the same,and the crack pattern is mainly inclined crack at 45° at the flange of the section steel,and horizontal crack at the flange of the section steel.With the increase of temperature,the crack direction changes from horizontal to 45°.In the temperaturerising test,the temperature growth trend of all test points is basically the same,the temperature curve is in the shape of "S",and the temperature of all test points finally tends to be the same.Some high-temperature specimens,such as SRRPC-5?SRRPC-7 specimens,burst at high temperature,which accelerated the temperature growth rate of some measuring points significantly.The load-slip curve of SRRPC is given,which is divided into five stages according to the changing trend: the static stage,the rising stage,the turning stage,the falling stage and the horizontal stage.With the increase of temperature,the static segment in the load-slip curve disappears and the range of the descending segment gradually decreases.The influence of high temperature on bond slip mechanism is analyzed,the proportion of friction in bonding force increases with the increase of temperature,and the formula for calculating the proportion of friction at high temperature is given.With the increase of temperature,the ultimate bonding load and residual bonding load gradually decrease,and the decline rate of load is faster before 300°C,and slows down significantly between 300°C.Compared with the normal temperature specimens,the ultimate bonding load of the specimens under high temperature was reduced by 18.59%,35.59%,71.90%,81.18%,84.64% and 92.2%,respectively.The residual bond loads were reduced by 14.97%,31.43%,67.24%,75.07%,77.25% and 87.62%,respectively.With temperature increasing,the slip of the ultimate bonding load increased gradually.Based on the data fitting,the ultimate bonding load,the slip of the ultimate bonding load and the calculation formula of the residual bonding load are given.Based on whether there is a stationary section or not,the ?-S curves were divided into two categories,and the model sketch of different curves and the bond-slip constitutive equation of SRRPC at high temperature were given.The calculated values of the constitutive equation were compared with the experimental values,and the curves were in good agreement,which could better reflect the bond slip curve morphology characteristics of the steel reactive powder concrete column at high temperature,and had guiding significance for the fire-resistant design of the steel reinforced reactive powder concrete column.In this paper,ABAQUS software was also used to simulate the push-out test at high temperature.The establishment m1 ethod of bond slip model of steel reinforced reactive powder concrete specimen and the establishment process of spring unit in ABAQUS are introduced,the meshing method and the spring distribution diagram are given.The simulated P-S curve is in good agreement with the test P-S curve,which attests the availability of the model.The simulated results can also be used to verify the experimental results.The stress nephograms of section steel at different moments before the ultimate binding load are given,and the bonding process of reactive powder concrete of section steel is analyzed in combination with the change of spring element in the stress nephogram. |
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