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Bridge piers are designed to withstand not only axial loads of superstructures and passing vehicles but also out-of-plane loads such as earthquake excitations and vessel impact loads. Vessel impact on bridge piers can lead to substantial damages or even collapse of bridge structures. An increasing number of vessel collision accidents have been reported in the past decade. A lot of researches have been conducted for predicting barge impact loads and calculating structural responses. However, in practice it is not possible to design bridge structures to resist all levels of barge impact loads. Moreover, with an increasing traffic volume and vessel payload in some waterways, the bridge piers designed according to previous specifications might not be sufficient to resist the current vessel impact loads. Therefore, strengthening existing bridge piers are sometimes necessary for protecting structures from barge impact. Carbon fiber reinforced polymer (CFRP) has been widely used in strengthening reinforced concrete structures under impulsive loadings. It is an effective material which has been proven to be able to increase the flexural strength of structures. In this study, CFRP composites are used to strengthen reinforced concrete piers against barge impact loads. Pendulum impact tests are conducted on scaled pier models. Impact force and pier response with and without CFRP strengthening are compared. The effectiveness of using CFRP strengthening the pier model is observed. In addition, numerical models of the bridge piers are developed and calibrated with experimental results. Parametric simulations of barge impacting on piers with or without CFRP strengthening are carried out. The results show that compared with unstrengthened pier, CFRP composite strengthened bridge pier has a higher impact resistance capacity and hence endures less structural damage under the same barge impact load. The effectiveness of CFRP strengthening with different CFRP thickness, CFRP strength and bond strength between the pier and the CFRP composite are also discussed.

Bridge piers are often designed to resist barge impact loads according to empirical equations given in various design codes based primarily on equivalent static analyses. Although these analyses can give useful guidance in design practice, they neglect dynamic effects which can have significant influence on barge-bridge structure interactions. It is necessary to develop an efficient and accurate method that takes into consideration of dynamic effect, material nonlinearity and structural damage in predicting impact loads and structural responses. In this study, empirical equations based on intensive numerical simulation results proposed in a previous study are used to estimate dynamic impact loads on bridge piers. The bridge structure is simplified as a nonlinear single degree of freedom system to calculate its dynamic response. As compared to detailed finite element simulation, this simplified approach is straightforward and gives reasonably accurate prediction of bridge responses. It can be used in the preliminary analysis and design of bridge structures against barge impact.

The Norwegian Public Roads Administration is running a project “Ferry Free Coastal Route E39” to replace existing ferry crossings by bridges across eight fjords in western Norway. Since most of the fjords are wide and deep, construction of traditional bridges with fixed foundations is not possible. Therefore, floating bridge concepts are proposed for the fjord-crossing project. Since the floating foundations of the bridges are close to the water surface, the concern of accidental ship collisions is raised. Considering the displacement and speed of the passing ships and the significant compliance of the bridge, interaction between the bridge and the ship can be significant should a collision occur. Many studies have been conducted on ship collision with bridge structures with a special focus on bridge piers. However, the research on ship collision with bridge girders is quite limited. The purpose of this study is to investigate the collision response of a floating bridge for ship–girder collision events. Both the local structural damage and the global dynamic response of the bridge are assessed. Local structural deformation and damage are first investigated by numerical simulations with detailed finite element (FE) models in ls-dyna. Subsequently, the bridge global response to the collision loads is analyzed in usfos using the force–deformation curves from the local analysis. By combining the local and global analysis results, a comprehensive overview of the bridge response during ship–girder collisions can be obtained.

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Numerical investigations of the dynamic response of a floating bridge under environmental loadings Floating bridges across wide and deep fjords are subjected to the environmental wind and wave loadings. The dynamic response of the bridges under such loadings is an important aspect, which should be carefully investigated in the design process. In this study, a floating bridge concept, which consists of two cable-stayed spans and nineteen continuous spans, is selected. A finite element model of the bridge is established using the software USFOS. An eigenvalue analysis is first conducted to obtain the natural periods and vibration modes of the bridge. It is found that the period of the first mode is typically in the order of one minute or more. This implies that the amplified response effect should also be evaluated for the second-order wave load in addition to the first-order wave load. By performing a nonlinear time domain dynamic analysis, the bridge dynamic responses from wind and wave loadings are obtained. The effects of the wind load, first-order and second-order wave loads are studied considering different load combinations. Structural responses including girder displacements, accelerations and moments are investigated for each load combination.