Research On The Ability Of Deep Water Pile Foudation Of Cross Sea Bridge Against Ship Collision And Its Safety Assessment

Our country had built nearly a hundred River-Crossing Bridges and Sea-CrossingBridges in recent twenty years. Many of them were world-renowned super engineering, butthe ship-bridge collisions took place usually in personnel dead, property lose and injured etc.Which meaned the anti-collision design and measures of bridge had obvious shortcomings innavigable waters. Our country started latly and also not notice the importance of research ofbridge collision avoidance, so the research of anti-collision design theory and calculationmuch dependended on foreign, which form a disproportion with china’s general level ofbridge construction. Combining with the engineering of Pingtan Strait Bridge, the simulatedtest, numerical analysis and theoretical analysis methods to research on the ship collisionprevention ability of bridge piles foundation in deep water was stuied in this paper. Based onthe analysis, the safety assessment of ship bridge collision risk was carry out, the typeselection of anti-collision and the key technology of anti-collision facilities design andconstruction of piles foundation in deep water was put forward. The main results were shownas the following:1. The bridge simulation test of ship collision of Pingtan bridge was carried out to verifythe the accuracy and reasonableness of calculation parameters of the numerical simulationmethods. The results of ship collision test showed that: the natural frequency of pier on theenvironment excitation was close to finite element simulation, the data curves of accelerationand velocity of the numerical simulation and vibration field testing had been showing a strongnonlinear, but the overall trend is consistent between the two curves. The experiment verifiedthe rationality of isotropic strain plasticity model relevant constitutive relations and relatedcalculation parameters of anti collision steel box and marine steel, which provided anexperimental basis.to the crash finite element simulation.2. The results obtained from numerical simulation computation of ship impacting bridgepile foundation showed that：the head-on collision under the lowest navigable water level isthe most adverse conditions of ship bridge collision computing, and At this time the bendingmoment of pile foundation pile foundation is largest. Compared with no anti-collisionfacilities of pile foundation, the maximum impact force, horizontal displacement of pilecaps, maximum bending moment and maximum tension stress of pile foundation reducesignificantly, at the same time depth of ship collision reduce significantly as well withanti-collision facilities of pile foundation.3. The mechanical model of a group pile foundation under of the role of ship collision was established. When the cap was acted by twisting, the calculated of pile internal forces wasproposed.4. The ship collision force was calculated by using the empirical formula method, finiteelement method and dynamic simulation, the AASHTO model was used to calculate the shipcollision probability, and the collision force standard was deduced. The results show that: theresult of dynamic simulation wa the maximum force, and the force value of each pier of themain navigation was34.66MN, while non-navigable was22.14MN; ship collision probabilityof each pier of the main navigation was2.187×10-4, while non-navigable was0.492×10-4; it wasverified that the assumed collision force design standards value of main navigation pier34.5MN and non-navigable transition pier21.5MN t meet the requirements.of specification.5. It was proposed that the anti-collision of deepwater pile foundation of cross-sea bridewas designed with steel sleeve box. Pile caps with Sutable surface elevation could effectivelyreduce the risk of bridge hit by ship and it was recommend that the installation ofanti-collision steel crash box and the pile caps should be constructed synchronously. Thedesign and construction technolygy of anti-collision steel boxed cofferdam and anti-collisionpier was introduced.The research results not only can improve theoretical system of large-scale cross-seacollision deepwater foundation of the bridge, but also have reference value to the design andconstruction techniques.