Damage And Safety Evaluation Of Continuous Rigid Frame Bridge Under Blast Loading

In the national infrastructure,bridges are regarded as the "lifeline" of land transportation.Continuous rigid frame bridges are widely used because of their strong spanning ability and high degree of construction standardization.In recent years,explosions caused by terrorist attacks and traffic accidents have seriously threatened the safety of bridges during the operational cycle.Therefore,it is of great significance to study the mechanical properties and safety evaluation of bridges after being subjected to explosive loads.Based on the theory of residual bearing capacity of bridge structures,the dynamic response,damage mechanism and failure modes of continuous rigid frame bridge under blast loading are studied.The damage index T based on the control section area is proposed,and a rapid evaluation method is established to realize the effect on the explosion load.The rapid evaluation of bridge safety and its application to engineering practice to verify the feasibility of this evaluation method.The specific conclusions are as follows:1)Using LS-DYNA finite element analysis software,by analyzing the damage law of the bridge when the blast load is located in the span of the continuous rigid frame bridge and the 1/4 span;the maximum displacement and acceleration peak of the bridge body are 1 The displacement of the/4 span is 1.35?1.43 times.When the explosion load acts on the span,the displacement of the continuous rigid frame bridge is large and the damage effect is significant.2)Study the proportional distance R(m/kg 1/3),R=r/(?)W(r is the distance between the source and the bridge,and W is the TNT equivalent of the explosion load),respectively,when the beam is strained at 0.26,0.32,and 0.44.The results show that the peak strain of the roof decreases with the increase of the proportional distance.The maximum and minimum strain peaks are 1.9 mm and 0.2 mm respectively.The ratio of the proportional distance increment to the top plate strain increment is analyzed.The proportional distance is found on the top plate under blast loading.The variation of the equivalent stress cloud diagram of the failure process of the continuous rigid frame bridge is analyzed.It is found that the damage of the bridge is caused by the micro crack of the reinforced concrete,and the crack accumulates.The failure process of the explosion shock wave is extended from the roof of the box girder to the flange plate and the abdomen.The plate is applied to the bottom plate.When the explosion load is close to the bridge and the equivalent is small,it is easy to cause local damage,and the damage degree of the explosion surface of the bridge is much higher than other positions.4)Based on the theory of residual bearing capacity of bridge structure,considering the overall structure and local components of the bridge,the damage degree of the bridge after the explosion load is divided into four levels of damage,namely slight,medium,severe and complete,is proposed by the control sectional area.The damage index T establishes a rapid evaluation method,which realizes the rapid evaluation of the bridge safety level after the explosion load,and verifies the feasibility of the evaluation index through engineering application.