Experimental Study On The Fire Resistance Performance Of Steel Reinforced RPC Columns With Different Axial Compressive Ratios

Reactive powder concrete(RPC)is a new building material with super high strength,high toughness and low permeability.Reactive powder concrete(RPC)combined with section steel can not only make the structure give full play to the seismic performance of section steel,but also inherit the ultra-high compressive strength of RPC.Therefore,steel shaped reactive powder concrete structure has become the focus of research in recent years.However,fire occurred frequently in recent years,and fire affected area of SRC structure is large.In order to reduce economic loss and protect people’s personal and property safety,it is necessary to study the fire resistance design of this kind of structure.At present,there are many researches on the fire resistance of SRC structures,the material properties of RPC structures and the finite element simulation of RPC structures at high temperature,but the fire resistance of SRC structures has not been reported.Therefore,5 specimens were designed in this paper to study the fire resistance of shaped steel and RPC columns with different axial compression ratios(0.2,0.3,0.4,0.5,0.6),and the following conclusions were drawn:(1)The surface of the steel reinforced reactive powder concrete(SRRPC)columns were grayish white after fire,and the grayish white becomes more obvious with the increase of fire resisting time.Cracks of all specimens were mainly short vertically.The larger the axial compression ratio,the denser the distribution of cracks.At the same time,the smaller the axial compression ratio,the longer the fire time,the more obvious the concrete burst phenomenon,and the larger the burst area.The cracking degree also increases with the increase of axial compression ratio.(2)It can be seen from the comparison of the temperature field measured by the tests of all specimens that the temperature field variation trend of SRRPC columns with different axial compression ratios were basically the same: with the increase of heating time,the heating rate was slow in the first 50 min or so,and it speeds up when the temperature exceeds 50 min.All specimens conform to the rule that the closer to the concrete surface,the higher the temperature.(3)The axial displacement curves of columns with different axial pressure ratios varied with temperature rising time.The specimens(C1 and C2)with relatively small axial compression have expansion displacement during the heating process,that is,in the early stage of the test,the axial displacement increased negatively.When the displacement expanded to the maximum,it began to increase slowly and positively,and the specimen began to be compressed.After the displacement increases to 0,the axial displacement gradually increases with the increasing of heating time,until the specimen reached the failure standard or lose the bearing capacity.However,for specimens with relatively large axial compression(C3,C4 and C5),there is no expansion displacement stage,that is,after the start of the test,the displacement is maintained at zero for a period of time,and then the displacement increases positively with the increase of heating time,until the specimen reaches the failure standard or loses the bearing capacity.This is because the active powder concrete expands in heat and contracts in cold.When the concrete is heated,the concrete will expand.When the axial pressure is less than the expansive force of concrete,the specimen will have an expansive displacement.When the axial pressure is greater than the expansive force of concrete,the specimen will not have the expansive displacement.Compared with five specimens with axial displacement curve,when the axial displacement is larger than 0,observed that with the increase of axial compression ratio,specimen under pressure,the faster the rate of axial displacement.(4)The fire resistance of SRRPC columns with different axial compression ratios were different.With the increase of axial compression ratio,the fire resistance of SRC columns decreased gradually.(5)Compared with the actual temperature field,the temperature field of SRRPC columns obtained by ABAQUS numerical simulation were in good agreement.The simulated axial displacement curve was roughly similar to the actual displacement curve.ABAQUS numerical simulation can better reflect the fire resistance of SRRPC columns.