The Dynamic Analysis Of Vessel-Bridge Collision And The Reliabity Of Bridge Structures Subjected To Vessel Collison

The bridges crossing coastal or inland waterways are exposed to the hazard of being damaged or destructed in an event of vessel collision. The impact load by vessel collision has been an important risk which cannot be negligible for the life cycle performance of bridge structure during the planning, design and operation. Based on the productive work from previous related literatures, this dissertation aims at conducting the analysis of the vessel-bridge collision by both theoretical derivation and numerical calculation, and the reliability of bridge structures is also investigated under vessel collision actions. The major work are summarized as follows:(1) A comprehensive review is made on the vessel collision accidents, the theoretical and experimental research progress of vessel-bridge collision in both domestic and overseas area. The characteristic of vessel-bridge collision research is stated and compared with the current dynamic analysis problems, such as wind-resistance and seismic analysis of bridges. The practical significance of vessel-bridge collision research is also clarified.(2) The provisions in the advanced AASHTO specifications and Eurocode are presented in detail on the vessel-bridge impact load, and also the related vessel impact force specification are introduced in the China railway and highway bridge design code. The differences among these provisions in US, Europe and China are discussed and three vessel-bridge collision analysis approaches, i.e., coupled dynamic analysis method, simplified impact force method and response spectra analysis method, are summarized and their merits and limitations to calculate the bridge impact responses are also discussed.(3) According to the vessel classification of AASHTO specifications, the barge and cargo ship are taken as representative vessels in the inland river and sea area respectively, which have obvious distinction in the outer configurations and inner components layouts of vessel bow part. Their differences are compared on these several aspects, such as the impact force time histories, the progressive deformation of vessel bows, the deformation-impact force relationship and the induced bridge dynamic responses. The peak impact forces by these two sorts of vessels are also contrasted with the equivalent impact loads by the current codes.(4) Based on the extensive simulation results and the conservation principles of kinetic energy and linear momentum, the simplified barge impact load model are proposed for both elastic and inelastic collisions. The simplified force models take into account the influences of barge impact velocity, barge loading tonnage and pier size. The proposed force models are validated through comparisons on the impact force time histories and response spectra with FE results and proposed force model in the related literature. The feasibility is also demonstrated for employing the impact force time history to conduct the vessel-bridge collision analysis and get the bridge responses. The effect of the key points in the impact force model are also discussed on the bridge responses. The supplementary derivation is made to determine the inland ship impact load time history in the Eurocode.(5) The modal participation coefficients for bridge pier top displacement and base shear force and bending moment are derived which are applicable for vessel-bridge collision analysis by basic theory of structural dynamics. The differences of bridge dynamic analysis are recognized whether under vessel collision or wind and earthquake action. The contribution of each mode to the concerned responses is investigated and the proportion of superstructure modal mass to the total modal mass is discussed as well within each mode. The simplified single pier with two added DOFs model is proposed for the vessel collision analysis with girder bridge, and also the rationality is explained for adopting a single tower to conduct collision analysis with cable stayed bridge. According to the characteristic of bridge modal responses by vessel collision, a new modal combination rule SRPC (square-root-of-partial-combination) is proposed which is more applicable for quantifying the maximum responses due to barge impact load. The equivalent cap stiffness is adopted as a simplified way to consider the soil-pile interaction and implemented in the vessel-bridge collision analysis. The effect of soil-pile interaction is also discussed on both the impact force and bridge responses.(6) Based on the simplified impact force time history of barge and ship collision, the model and framework is established for bridge structure reliability analysis under vessel collision, which the reduction effect of peak impact force varying with the impact angle is also considered in the analysis process. The vessel-bridge collision stochastic dynamic analysis program (VBCSDAP) is made to conduct the reliability of bridge under vessel collision events. With the employment of the proposed bridge reliability analysis program VBCSDAP, the failure probability of a cable stayed bridge span navigable waterways is investigated and estimated subjected to the vessel collision risk. According to the results by the proposed reliability method, the vulnerable position of bridge substructure is confirmed and explained, the damaged mode and its characteristic are also discussed at last.