Simulation Study On Cantilever Pushing Construction Of Coastal Steel Trestle Bridge

Trestle engineering plays an important role in the development of marine economy.However,the current use of trestle construction is not only unable to meet the increasing demand for use,but the construction speed is slow,which is not conducive to the development of marine resources and marine environmental protection.Based on this,this thesis studies the construction technology of cantilever push for offshore steel trestle bridge,which can improve the construction quality of marine engineering.Combined with actual engineering cases,the technical problems in the cantilever push construction process were analyzed.A wave-current coupling numerical model was established,and the time-history response of steel pipe piles under the action of waves and currents was obtained.A multi-scale finite element model of construction considering contact was established.Based on this,the cantilever jacking construction scheme was optimized,and the feasibility and safety of jacking construction were proved.The main contents of the paper are as follows:1.The current development status of marine engineering and the existing research results were summarized.The existing offshore trestle construction methods in depth was analyzed,the purpose and significance of the research on the cantilever jacking construction method was clarified.(Chapter 1)2.The technical methods and technical problems of cantilever pushing construction were explained.Combined with the actual offshore steel trestle project,the construction process was introduced.During the cantilever pushing process,the response of the steel pipe pile to the ocean load,the feasibility of pushing and the construction safety were pointed out that need to be studied.(Chapter 2)3.The coupled load of wave and current on steel trestle group piles under marine environment was studied.Based on the numerical wave-making method,a numerical simulation of the wave-current coupled load under complex sea conditions was carried out,and the theoretical formula of the code was compared with the numerical method to obtain the wave-current coupled load on a single pile.The results show that the theoretical calculation value is in good agreement with the simulation result.The feasibility of the method was verified.The time-history response of the steel trestle steel pipe pile in the cantilever jacking construction under the wave-current coupled load was obtained.(Chapter 3)4.The optimization method of the construction plan for the cantilever jacking construction was proposed.A multi-scale model of jacking construction considering contact nonlinearity was established,and the jacking effects under different soil constraints were compared.It was found that the construction is highly sensitive to the soil constraints.The stronger the soil constraints,the better the stability of the cantilever jacking construction.Based on this,an optimization plan for the construction process was proposed,that is,to improve the stability of construction by setting up wire rope connections between the piles.The analysis results showed that after optimization,the difference in the lateral displacement of the pile leg pushing construction under different bottom constraints and bottom embedded constraints is controlled within 20%,avoiding the occurrence of "rail jams";the maximum stress value difference of bridge members is controlled within 10%.In addition,a pile-sinking control optimization method was proposed.By studying the settlement and jacking control state during the pile-sinking construction process,the maximum settlement and jacking limits of each pile-sinking construction condition were obtained,so as to guide the construction and reduce the workload of construction adjustments,speed up the construction speed.(Chapter 4)5.The feasibility and safety of construction jacking were evaluated.According to the finite element calculation results of the multi-scale nonlinear model of the jacking construction,the structural response of the steel trestle bridge during the construction process was analyzed;the local refined model was established to study the stress state of the key nodes.The results showed that the supporting reaction force does not exceed 5800 k N during the pushing process of the steel pipe pile,which meets the bearing capacity requirements of the steel pipe pile;the maximum lateral offset of the pile leg is 119 mm,and "rail jams" does not occur under the most unfavorable conditions,the bridge can be pushed smoothly;the required maximum pushing force is 532 k N;after the construction is completed,the maximum deflection ratio of the bridge is 1/3703;during the construction process,the components of the trestle bridge do not yield,and the key joints have sufficient safety reserves,which shows that the construction technology meets the safety control conditions.(chapter 5)...