Numerical Simulation Of Extreme Met-ocean Conditions And Stochastic Dynamic Response Of Sea-crossing Bridge Under Typhoons

Typhoon is a destructive depression weather system formed in the tropical or subtropical ocean.The strong wind,huge wave and storm surge during typhoon pose a great threat to the safety of the sea-crossing bridge.China is one of the countries with the most frequent typhoon disasters.Typhoons and their secondary disasters bring a series of problems and challenges to the design of the sea-crossing bridges and disaster mitigation.Driven by the “Maritime Power”and “Transportation Power” strategies and the “One Belt One Road” initiative,a series of issues concerning the sea-crossing bridge under typhoon were investigated from the aspects of the simulation of extreme met-ocean conditions,multidimensional probability model,typhoon wind hazard,stochastic dynamic analysis of structure.Based on a thorough literature review,the following aspects of these problems related to the topic were comprehensively investigated using numerical simulation,mathematical statistics,theoretical derivation,and finite element analysis:(1)Superimposing the Holland model wind field with Jakobsen and Madsen model wind field and CCMP wind field,typhoon wind field was firstly simulated.Then,the typhoon pressure field,wind field,and the TPXO tide model were used to drive the SWAN+ADCIRC wave-current coupling model to simulate the extreme met-ocean conditions in the sea area of the bridge site.The feasibility and accuracy of the numerical model were validated by the measured wind and wave data.Finally,the evolution law of wave height,wave spectrum,and storm surge in the sea area of the bridge site during a typhoon was investigated.(2)The extreme met-ocean conditions of 58 historical typhoons from 1990 to 2018 that influenced the Pingtan Straits Rail-cum-Road bridge site were simulated.Based on the simulated wind and wave dataset,the statistical characteristics of the extreme environmental factors at the Pingtan bridge site were discussed,including wind speed,wave height,wave direction,wind-wave misalignment and mean wave period.The joint probability model of multi-dimensional environmental factors extremum was established by Copula theory,PairCopula model,and other multi-dimensional variable connection methods.The environmental contour and contour surface under a given return period were established by the inverse firstorder reliability method(IFORM).The trivariate joint probability models and the environmental contour surface models of wind and wave including wind-wave misalignment,and mean wave period were established,respectively.(3)To make up for the insufficient extreme value analysis data and the defect of the return period value calculation by extrapolating the probability model,a full-track stochastic model to generate synthetic typhoons was developed,including the effect of spatial heterogeneity.The effects of ocean feedback and environmental vertical wind shear also include in the model.The performance of the developed model was validated by the historical typhoons in many aspects,including the statistics of the key parameters of typhoons along the coastline of China,the characteristics of typhoon track and intensity evolution and distribution,etc.The typhoon wind hazard maps along the China east coast were finally assessed using the developed stochastic model of typhoons.(4)The analysis method of sea-crossing bridge dynamic response during typhoons was developed.Taking Pingtan Straits Rail-cum-Road bridge as an example,the variability of short-term analysis and the extreme load effects were studied.The stochastic dynamic response characteristics of bridges during typhoons were investigated based on a historical typhoon event and the wind-wave environmental contour surface models,respectively.