| Green High Performance Fiber Reinforced Cementitious Composite(GHPFRCC)is a new type of building material that uses high-volume fly ash instead of cement,which has better ductility and higher energy absorption than ordinary concrete.The fire has now become the main factor affecting the safety of the structure.The high temperature effect will lead to the decrease of the mechanical properties of the concrete,which will affect the safety of the concrete structure.In this paper,GHPFRCC was used to strengthen the fire-damaged frame column,and the triaxial compressive performance of GHPFRCC material and the seismic performance of GHPFRCC reinforced fire frame were studied.The main contents include the following:(1)Completing the triaxial compression test after high temperature GHPFRCC.The compressive strength and strain of GHPFRCC test pieces under different high temperature were measured by triaxial compression test.The effects of loading rate,confining pressure and temperature on the triaxial compressive strength,elastic modulus and strain were analyzed.The results show that the compressive strength of the specimen with different mixing ratio and the best mix ratio decreases with the increase of the temperature,and the compressive strength of the specimen with the confining pressure increases with the increase of the temperature.The compressive strength of the specimen is less affected by the confining pressure at 25?and 200?.In this case,the strength of the specimen is mainly provided by the strength of the test piece and the fiber.And at 400?,600? and 800? the compressive strength of the specimen is provided by confining pressure.The loading rate has little effect on the compressive strength of the GHPFRCC specimen.(2)Completing the fire resistance test of the frame columns.The temperature field distribution and fire damage of the column cross section were analyzed by fire test of twoGHPFRCC frame columns and two C30 concrete frame columns.The results showed that the temperature in the middle of the column cross section was 242?,and the temperature at the corner of the column cross section was 358?.For the concrete the number was 388?and456?,respectively.The temperature of the GHPFRCC frame column was lower than the C30,indicating that GHPFRCC has better fire resistance.The reason is that the PVA fibers in the GHPFRCC are melted at 230?,forming fine pores.The water vapor in the column can escape through these pores,effectively maintaining the cross-sectional area of the frame column,forming a protective layer,inhibiting the heat transfer and convection,controlling the temperature rise in the column,keeping the cylinder at a lower temperature.(3)Completing the quasi-static tests of GHPFRCC reinforced fire-damaged frame columns.A GHPFRCC frame column and a C30 frame column were reinforced in four fire barriers.Two reinforced frame columns,two non-reinforced fire-damaged columns,two unventured frame columns(6 in total)were subjected to quasi-static tests.The seismic performance and energy dissipation capacity of these frame columns were analyzed.The failure of the C30 frame column and the non-retrofitted C30 frame column are more serious in the test,and the wide main cracks appear in the column surface.More inclined cracks appear on the side of the column,indicating the crust damage.For the non-retrofitted GHPFRCC frame column and GHPFRCC reinforced frame column less damage,the column cracks are fine cracks and the cracks evenly distributed in the bottom of the column,and the side cracks are mostly horizontal cracks.The bottom of the column was not crushed,and the failure is caused by the hinge forming between the cylinder and the base.The results show that the stiffness of the frame column strengthened by GHPFRCC is better than that of the non-retrofitted frame column.The stiffness loss rate of the GHPFRCC reinforced frame column is lower than that of the fire-damaged frame column.The ultimate load carrying capacity of the GHPFRCC frame column is better than that of the corresponding C30 frame column. |
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