Traffic Capacity Assessment of the Urban Elevated Bridge after Near-Field Explosion Based on the Response Surface Method

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.

Damage-Involved Structural Pounding in Bridges under Seismic Excitation

During severe earthquakes, pounding between adjacent superstructure segments of highway elevated bridges was often observed. It is usually caused by the seismic wave propagation effect and may lead to significant damage. The aim of the present paper is to show the results of the numerical analysis focused on damage-involved pounding between neighbouring decks of an elevated bridge under seismic excitation. The analysis was carried out using a lumped mass structural model with every deck element discretized as a SDOF system. Pounding was simulated by the use of impact elements which become active when contact is detected. The linear viscoelastic model of collision was applied allowing for dissipation of energy due to damage at the contact points of colliding deck elements. The results show that pounding may substantially modify the behaviour of the analysed elevated bridge. It may increase the structural response or play a positive role, and the response depends on pattern of collisions between deck elements. The results also indicate that a number of impacts for a small in-between gap size is large, whereas the value of peak pounding force is low. On the other hand, the pounding force time history for large gap values shows only a few collisions, but the value of peak pounding force is substantially large, what may intensify structural damage.

Pounding Between Superstructure Segments in Multi-Supported Elevated Bridge with Three-Span Continuous Deck Under 3D Non-Uniform Earthquake Excitation

Reports after severe ground motions show that the earthquake-induced structural pounding may lead to significant damage in elevated bridges. The aim of this paper is to analyze pounding between superstructure segments of a highway elevated bridge with three-span continuous deck under 3D non-uniform earthquake excitation, which is induced by spatial seismic effects related to the propagation of seismic wave. The conditional stochastic approach has been applied to generate the earthquake records for different support locations along the structure. The analysis has been conducted with the help of FEM taking into account the influence of rotation of superstructure segments due to corner collisions. The detailed non-linear strain-rate-dependent model has been applied to simulate the behavior of bearings under earthquake excitation. The results of the study confirm that pounding has considerable influence on the behavior of the analyzed bridge and may lead to the substantial increase in the structural response. They show that the structural response depends much on the gap size between adjacent superstructure segments. Moreover, the results clearly indicate that the incorporation of the non-uniform earthquake excitation may lead to considerable changes in the structural behavior. The application of the method of conditional stochastic modeling for generation of earthquake records has also been proved to be useful for practical purposes of modeling the spatial seismic effects for long multi-supported elevated bridges.

Shear Stress Distribution and Deflection of Preflex I-Girder with Corrugated Steel Web

A new type of preflex I-girder with corrugated steel web has been proposed to provide better solution for urban elevated bridge. The purpose of this study is to explore shear stress distribution and deflection of such preflex I-girder. Shear stress distribution in section of steel-concrete composite girder was analyzed by shearing stress integral equation and piecewise function, and a quarter-scale preflex I-girder with corrugated steel web was fabricated and tested. Experimental and analytical results show that the shear stiffness is only depends on corrugated steel web, and the shear stress is uniformly distributed along the height of corrugated web. It is found that the proposed shear stress equation is consistent with the experimental result and the deflection integral equation is agreed well with the FEA result. The result suggests that the shear deflection is as larger as 25.8% of the total deflection, and should take shearing deflection into consideration.

Study on the Structural Dynamics of the Elevated Station in Rail Transportation

As the number of the urban population attains a continuous increasing these years, the carrying load of all kinds of transportation lines in society changes into heavier as well. For the purpose of fulfilling the services demands of the rail transportation, the elevated station has turned into a new type of transportation structure, and exercises a critical role in the reduction of the social transportation pressure. The elevated station is a body integrated by both the rail transportation and the elevated bridge, and is much stronger than the traditional structural model in the aspects of the carrying load and structure performance. In accordance with this point, the author emphatically analyzes the structural dynamics of the elevated station in rail transportation in this paper, with the purpose of bringing the using performance of the elevated station into better play.