钢筋桁架双向混凝土板耐火性能及高温承载力分析OA

To investigate the fire resistance of steel-bars truss concrete slabs(STC slabs),fire resistance tests were conducted on a full-scale four-edge simply supported two-way STC slab and a traditional reinforced concrete(RC)slab,to compare their differences in cracking patterns,temperature field,and displacement development.The load-carrying capacities of both slabs at elevated temperatures were computed.Experimental and calculation results show that during the initial fire stage,the internal concrete and reinforcement of the STC slab heat up more slowly and exhibit a smaller temperature gradient than the RC slab,owing to the fire insulation effect of the bottom galvanized steel sheet.Consequently,the vertical displacement growth rate of the STC slab is lower than that of the RC slab.However,after 60 minutes of fire exposure,as the galvanized steel sheet gradually chars and peels off,and the presence of web bars accelerates internal heat transfer,the internal temperature and vertical displacement at the central region of the STC slab approach or even exceed those of the RC slab.By 180 minutes of fire exposure,neither slab reaches its fire resistance limit,resulting from the formation of tensile membrane effects by the reinforcement within the slabs,which enhances their load-carrying capacities at elevated temperatures.Calculation results reveal that the predicted load-carrying capacity at elevated temperatures considering tensile membrane effects is on average 13%-45%higher than that calculated by the classical yield line theory.Furthermore,the load-carrying capacities at elevated temperatures of the STC and RC slabs exhibit no significant difference.