Abstract
The traffic capacity of the urban elevated bridge is assessed after it is attacked by a near-field explosion, using the residual bearing capacity of the damaged pier as the assessment index. First, the finite element model of a reinforced concrete slab under near-field explosion is established by ANSYS/LS-DYNA software and compared with the experimental results, which verifies the effectiveness of the ALE (arbitrary Lagrangian–Eulerian) algorithm and the accuracy of the mesh size and material properties. Then, an “explosive-air-pier” coupling analysis model is constructed using the finite element method, and the damage of the reinforced concrete pier under three types of car bombs is evaluated. Furthermore, a response surface model for the residual bearing capacity of the pier is utilized to calculate the failure probabilities of various damage levels of the pier under the three types of car bombs and to assess the traffic capacity of the bridge after near-field explosion. The established assessment method can be used to predict the probability of bridge structural damage at various levels under different types of car bombs and to provide a reference for exploring a probability-based safety assessment method of post-explosion bridges.
Highlights
Duwadi and Chase [1] from the Federal Highway Administration (FHWA) pointed out that the bridge is vulnerable to physical, biological, chemical, and radiological attacks in addition to natural hazards
For the bridge after the attack of 2# car bomb (M 500 kg, H 0.8 m), when the explosion distance R is less than 1.24 m, the traffic indicator TA is less than 0.5, so the traffic on the bridge should be prohibited; when R is greater than 1.24 m and less than 3.06 m, TA is between 0.75 and 0.5, so 50% of the original traffic rate is allowed; when R is greater than 3.06 m, TA is bigger than 0.75, so there is no influence on bridge capacity, and original traffic rate is feasible. erefore, the potential hazard distance of 2# car bomb is 1.24 m
By using the residual bearing capacity of the damaged pier as the assessment index, a method for assessing the traffic capacity of the urban elevated bridge after near-field explosion based on the response surface method is proposed. e main conclusions are as follows: (1) e damage index of the pier after near-field explosion is closely related to TNT equivalent mass and explosion distance: the greater the TNT equivalent mass of the bomb and the shorter the explosion distance are, the more seriously the pier is damaged. e pier’s damage is obvious under the minibus carrying medium bomb (500 kg TNT equivalent mass) and the cargo carrying big bomb (1000 kg TNT equivalent mass)
Summary
Duwadi and Chase [1] from the Federal Highway Administration (FHWA) pointed out that the bridge is vulnerable to physical, biological, chemical, and radiological attacks in addition to natural hazards. As one of the main load-bearing parts of the bridge structure, once a pier is attacked by a near-field explosion and has a severe damage, the internal forces of the structural system will be redistributed, which may lead to the collapse of the bridge. Many researchers such as Hwang et al [4] and Shinozuka et al [5] directly equated the bridge structure’s damage level with the pier. A method to assess the traffic capacity of an urban elevated bridge after near-field explosion based on the response surface method is proposed, which can predict the probability of various levels of damage to the bridge under different types of car bombs, to provide a reference for exploring a probability-based method on evaluating the safety of the bridge after explosions
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