Research On Blast-Resistant Performance Assessment And Protective Measures For Urban Elevated Bridges

Since the reform and opening up, as an important part of infrastructure, the transportation system is developing particularly fast. The vigorous development of urban elevated bridges and expressway is greatly improving the transportation capacity and reducing urban traffic pressure. However, terrorist attacks or accidental incidents can cause damage to the bridge. Explosion in a special position may cause huge damage to the overall structure of the bridge, and lead to traffic congestion or even severe personnel casualty and economical loss at the same time. Although researches on blast-resistant building structure have made abundant achievements at home and abroad, related studies on urban elevated bridges subjected to blast loads are obviously insufficient. Therefore, it has important practical significance to research on blast-resistant performance assessment and protective measures for urban elevated bridges and provide a reference for comprehensive protection and blast-resistant design of urban elevated bridges. The main contents are as follows:1、Based on numerical simulation, an analysis method for dynamitic response and collapse process of urban elevated bridges subjected to blast loads is proposed. First of all, the explosion risk source of urban bridges is analyzed and the blast loads that urban elevated bridges may suffer are determined. Then, the finite element models of a bridge, dynamite and air are established by ANSYS/LS-DYNA software. By changing the position and quantity of dynamite, their effects on the response of displacement and the Von-Mises stress distribution around the middle of the bridge are investigated, and then the failure state and collapse process of the bridge are analyzed. Finally, by taking a three-span ramp bridge as example, the analysis process of the proposed method in this thesis is described in details.2、Reference explosion protection criterion of building structures,initially establish explosion protection criterion of urban elevated bridges. Reference the related provisions and the structural characteristics of urban elevated bridges, an blast-resistant performance assessment method is proposed. First of all, the blast precautionary grade for urban elevated bridges is defined by combining the above-mentioned two concepts,i.e.,the blast precautionary intensity and the blast precautionary goal.The explosion risk level of urban elevated bridges is derived through risk analysis.Then, the explosion protection criterion is defined for bridge structures according to different explosion risk levels.Finally, numerical simulation method is used to get the damage degree of the bridge under explosion loads, which can verify whether the bridge achieves the explosion protection criterion to assess the blast-resistant performance of the bridge.3、For the urban elevated bridges that do not meet the blast-resistant performance requirements, measures applicable to urban elevated bridges subjected to blast loads are proposed. Based on the structural characteristics and blast-resistant protective requirements of urban elevated bridges, the blast-resistant protective measures of urban elevated bridges are divided into blast-resistant safety measures and blast-resistant structural measures.