Pushover Analysis Method Considering The Effect Of Higher Modes In Seismic Analysis Of Bridges

In recent years, frequent strong earthquakes brought great casualties and economic losses to human beings. Because of the paramount importance of bridges in traffic system, strong earthquakes not only destroy bridge engineering itself, but also cut off the transport lifeline, which may result in significant difficulty for earthquake relief. Therefore, the seismic design, evaluation and reinforcement of bridge structures are important topics for disaster reduction, which attracts many researchers to dedicate on it. Pushover analysis is a widely used nonlinear static seismic analysis method for earthquake evaluation. Based on this method, this paper focuses on the following aspects:(1) The basic principles, solution steps, lateral load distribution, the capacity spectrum methods of pushover analysis are summarized and described in details. such kind of information is important for present study.(2) plastic hinge element and fiber-based nonlinear beam-column element are studied. Using the finite element analysis software OpenSees, pier models are established based on the two type of elements. Then the load distribution modes of both uniform and inverted triangular on piers are applied in pushover analysis, as to evaluate and compare the load effects of the two piers models. Studies indicate that the fiber-based nonlinear beam element can be more feasible to simulate the response characteristic of the structure.(3) The basic principles, solution steps, and of mode selection of modal pushover analysis are studied, and this method is employed to predict seismic response of the bridge structure considering the effect of higher-order modes. Four kinds of analysis, including the modal pushover analysis, the inverted triangular distribution pushover analysis, the basic-mode pushover analysis and the time history analysis, are performed on a continuous rigid bridge with different height of piers. Studies suggest that modal pushover analysis method is better than the conventional pushover analysis to present more accurate results when bridge piers are super high.(4) The modal pushover analysis is applied to the displacement-based seismic assessment. Then earthquake resistant capacity of a continuous rigid bridge with a 120m-high pier is evaluated under different earthquake intensity, indicating that modal pushover analysis method is applicable to the displacement-based seismic evaluation of bridges.