The Functional Study Of Rotary Anti-Ship-Collision Facility

When the water level reaches a certain height,there is a high risk that the main arch ring of a arch bridge can be struck by ships or other flotages.Because a main arch of an arch bridge owns a low capacity of resistance as well as a special constructional form,it’s not feasible to protect it with integrated anti-ship-collision system.In consideration of the special constructional form of arch bridge,this thesis comes up with a detached anti-ship-collision protective plan based on the status quo mentioned above.After designation to the boxed cofferdam’s form of detached anti-ship-collision system,selection to the material of the guide post and the form of cross section ploy,the author decides to adopt the finite element analysis software of LS-DYNA to optimize the function of this anti-ship-collision facility.This thesis mainly accomplishes the following work.Firstly,the author calculates the ultimate anti-curve bearing capacity of steel pipe-encased concrete with the length of 2.5 meters and reinforced concrete by using Midas Civil and Ucfyber software.Meanwhile,the author also used the software to calculate the structural resistant capacity of triangular cross-sections and quadrangle cross-sections.The final calculation finds that the steel pipe-encased concrete pile possesses higher carrying capacity compared with reinforced concrete pile.The structural resistant capacities of triangular cross-sections and quadrangle cross-sections are 29.5 MN and 42.1 MN respectively.Both of them meet the demand of anti-ship-collision resistance.Taking all kinds of factors into consideration,the author in the end chooses the steel pipe-encased concrete as the guide post material in antiship-collision system and the form is triangular cross-section.Secondly,the author adopts the finite element analysis software of LS-DYNA to simulate the anti-collision boxed cofferdams with three different materials.In the design or simulous analysis,the author uses the ships with their weight of 3000 DWT,2000 DWT,1000DWT to run into the three forms of anti-collision boxed cofferdam at the speed of 4m/s,3m/s and 2m/s respectively and the respective angle is 0,15,30.The final result reveals that the ultimate reduction rates of composite boxed cofferdam,steel-composite boxed cofferdam and steel boxed cofferdam are 47.3%,39.8% and22.6% respectively.In addition,the steel boxed cofferdam and the the steel-composite boxed cofferdam are damaged a little.By contrast,the composite boxed cofferdam isalmost ruined.At last,the steel-composite material boxed cofferdam is selected as the guide post material form in anti-collision system.Thirdly,this thesis optimizes steel composite material by using numerical simulation.The author analyzes the data by changing the inner stiffening rib of the boxed cofferdam,thickness of the panels.Then,the vertical distance of the inner stiffening rib of the boxed cofferdam and the thickness of the panel are 0.8m,0.8m and8 mm respectively.Under this condition,the total absorbed capacity of the boxed cofferdam is 11.6MJ with the rate of 33.1% and the absorbed capacity of each panel is quite even.The ultimate hit force is 9.2 MN and the reduction rate is 50.5%.The damage distance of the boxed cofferdam is 1.42 m which meets the demand of the optimal anti-collision function.Fourthly,the author designs six kinds of boxed cofferdams by changing the steel constructional thickness of steel composite boxed cofferdam and the thickness of the composite material’s fender.when the numerical simulation reaches a result that the thickness of the fender is 1.2m,the ultimate ship-hit force is 9.96 MN with the reduction rate of 46.9% and constructional cost of 1840 thousand RMB.This is the most reasonable form.