| At high temperature,the mechanical properties of concrete and steel are degraded,resulting in a decrease in the shear resistance of RC simply supported beams.Shear span ratio is one of the main factors affecting the shear performance of simply supported beams.The shear span ratio will directly affect the fire endurance and residual shear capacity of RC simply supported beams.The shear resistance tests of 9 RC simply supported beams with different shear span ratios at high temperature under fire and after fire were carried out.The research contents are as follows:1)Shear performance test of three full scale reinforced concrete beam with different shear span ratio(1.2,2.0 and 3.4)under the fire were carried out,the beam heating process of steel along the section temperature field distribution,temperature,level and vertical deflection,fire resistance of beam and beam failure pattern were obtained,the different shear span ratio on shear performance of reinforced concrete beam under fire were studied.2)Shear performance test of 6 full scale reinforced concrete beam with different shear span ratio after fire were carried out,the beam deflection curve,residual shear capacity,residual stiffness and failure morphology of the beam are obtained,the effects of different shear span ratios,fire time and cooling methods on the shear resistance of reinforced concrete beams under fire were studied.The results show that the longer the shear span ratio is,the shorter the time for RC beam to reach the fire resistance limits and the larger the failure deflections.On the contrary,the larger the fire resistance limit of RC simply supported beam,the smaller the deflection of failure.The longer the fire duration is,the more obvious the shear capacity of reinforced concrete beams will be weakened and the greater the failure deflection will be.Watering and cooling can greatly reduce the residual shear capacity of RC beam,and the surface concrete of RC beam is seriously cracked.Figure73;Table11;Reference 47... |
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