Research On The Bearing Capacity Evaluation And Reinforcement Methods Of Hollow Slab Bridge After Fire Damage

With the continuous expansion of China's highway construction scale,the number of bridge structures is increasing,and the problem of bridge disasters is becoming increasingly prominent.Fire is one of the disasters with the highest frequency and the most serious damage to bridges.When a bridge fire occurs,the high temperature will rapidly reduce the material properties of the bridge structure,resulting in a reduction in the safety of the bridge and a loss of load carrying capacity,which will seriously affect the normal use of the bridge structure.Therefore,how to reasonably evaluate the mechanical properties of the bridge structure after the disaster,and to formulate reasonable reinforcement and repair measures,are critical to the bridge's traffic safety and later operation.Aiming at the disease of Baofu Highway K31+216 Tanshan No.1 medium bridge after the fire,the methods of field investigation,theoretical analysis,and numerical calculation were comprehensively used to systematically analyze and study the selection of bridge structural material parameters before and after the fire,the bearing capacity assessment,the investigation of structural reinforcement methods,and the design and optimization of reinforcement schemes.The main research work are as follow:(1)The principles and characteristics of the reinforcement of old bridges and three commonly used reinforcement methods for hollow slab bridge structures were analyzed and analyzed.Finally,the scope of application of the three reinforcement methods were summarized.(2)Based on the previous research results on the thermal parameters and mechanical properties of concrete and steel bars,the characteristics and laws of reducing the mechanical properties of concrete and steel bars after high temperature were analyzed and summarized.The relevant parameters of the hollow slab model after fire damage were established.(3)With reference to previous simulation results of the temperature field of the hollow slab beam,the law of mechanical performance reduction of the hollow slab bridge after the fire was obtained.Based on the reduction coefficients of the structure size,strength and elastic modulus,the modified model of the hollow slab bridge after fire damage was obtained,and the calculation results were compared with the original bearing capacity.(4)Using Midas numerical simulation simulation and theoretical calculation methods,the effects of increasing the section method,pasting steel plate method,and pasting carbon fiber cloth on the reinforcement of fire-damaged hollow slabs were analyzed from three aspects: bending capacity,deflection,and load-displacement curve.Finally,through comparison between different reinforcement schemes,the respective applicable conditions and schemes suitable for background bridge reinforcement were obtained.