【作者】 王望；

【导师】 康锐；

【作者基本信息】 西南交通大学 ， 建筑与土木工程（专业学位）， 2022， 硕士

【摘要】 随着我国“海洋强国”、“一带一路”战略的推进,跨海大桥建设在服务国家重大战略的过程中凸显出重要作用,成为交通强国目标实现的重要组成部分。全球气候变暖加剧,如强风,大浪等极端气候现象出现的频率和强度均可能加大,这对海岸和近海结构的安全性来说是不利的。跨海大桥往往具有主跨轻柔,阻尼小,刚度小的特点,风和浪是其经受的主要荷载,为了研究风—浪对桥梁动力响应的影响,本文梳理相关文献,从建立风—浪联合分布模型、建立风—浪—桥耦合分析系统和进行桥梁有限元分析几个方面开展了研究,主要的研究工作包括:(1)建立风—浪联合分布模型。为了分析风浪要素之间的相关关系,本文基于我国东海的连云港海洋观测站实测风浪数据和Copula理论,建立了风浪要素中风速、波高、波浪周期、风向和波向五维随机变量的联合概率分布模型。首先,采用极大似然法确定各风浪要素边缘分布模型参数,通过AIC信息准则和均方根误差RMSE进行拟合优度评价,由此来建立风浪要素的边缘分布。其次,采用基于残差和贝叶斯框架的高斯似然函数来估计二维Copula函数的参数,结合AIC信息准则进行拟合优度评价并确定最优Copula函数,绘制了最优联合分布概率密度图,并与二维频率直方图进行对比评价模型拟合效果。最后,采用Vine Copula函数建立多维联合概率模型并结合AIC值评价其拟合优度。(2)建立了风—浪—桥耦合分析系统。以某跨海大桥为工程背景,介绍了大桥的工程概况,基于ANSYS有限元软件建立了桥梁的有限元模型,对跨海大桥成桥状态进行模态分析。通过合理简化将桥梁三维风场简化为主梁的一维风场和桥塔一维风场,选用了谐波合成法生成脉动风,并通过MATLAB语言编制程序实现;采用准定常抖振力模型计算主梁的抖振力;分别基于线性波理论和随机波理论模拟波浪场,结合桥梁基础形式选用小尺度墩柱波浪力计算理论,通过MATLAB编制程序实现波浪模拟和波浪力时程计算;将风—浪荷载作为激励,建立风—浪—桥耦合动力方程。(3)基于桥梁有限元模型和风—浪—桥耦合分析系统进行桥梁的动力响应分析。首先计算在风单独作用下桥梁的动力响应,计算了主梁在三个方向的振动位移均方根、主梁中跨跨中三个方向的位移时程,绘制了不同时刻主梁的振动形态,并根据求得的位移时程进行频谱分析,由此来分析主梁的振动情况。其次,根据桥址区水文资料确定波浪荷载工况,分别计算线性波和随机波作用下跨海大桥的动力响应,对比分析两种波浪理论的差异,对于线性波还分析了不同波高、波浪周期条件下桥梁横桥向位移响应的规律。最后,分别分析了线性波、随机波与风联合作用下桥梁的动力响应,并与单风、单浪情况进行对比分析。研究结果表明:本文建立的风—浪联合分布模型能较好地刻画风浪要素之间的联合概率分布,对于风浪荷载的合理确定具有一定积极意义;风—浪联合作用下,跨海大桥的动力响应存在耦合效应,并非单风单浪的简单叠加,风、浪荷载对主梁的横向振动均有较大贡献,而竖向振动主要是风荷载贡献较大,波浪荷载影响较小。更多还原

【Abstract】 With the promotion of China’s “Building an ocean power” and “Belt and Road Initiative” strategy,the construction of cross-sea bridge plays an important role in serving the national major strategy and becomes an important part of the realization of a transportation power.With the aggravation of global climate warming,the probabilities and load intensities of extreme weather phenomenon are gradually increasing,which could threaten the safety of coastal and offshore infrastructures.The cross-sea bridge is characterized by large span and samll stiffness which suffers from frequent wind and wave load.For the sake of researching the effects of combined wind and wave loads on the dynamic response of sea-crossing bridges,this text sorts the correlative literature and conducts researches from the establishment of the wind-wave joint distribution model,the establishment of the wind-wave-bridge coupling analysis system and the finite element analysis of the bridge.The major research work includes:(1)The establishment of wind wave joint distribution model.In order to analyze the correlation between wind and wave elements,based on the measured wind wave data from Lianyungang Ocean Observation Station in the East China Sea and Vine Copula theory,a joint probability distribution model of wind speed,wave height,wave period,wind direction and wave direction is established.Firstly,the marginal probability distributions of wind and wave data are determined,in which the AIC criteria and RMSE are employed to select the optimal probability distribution model and the maximum likelihood method is used to obtain the model parameters.Subsequently,the optimal two-dimensional Copula function for wind and wave data is determined through using the AIC criteria,and the model parameters are fitted with a Bayesian framework with a residual-based Gaussian likelihood function.To illustrate the goodness of fit,the binary frequency histogram of the original wind and wave data is compared with the proposed two-dimensional optimal joint distribution probability density function.Finally,the multi-dimensional joint probability distribution model of wind and wave data is established with the Vine Copula function based on the AIC criteria.(2)A wind-wave-bridge coupling analysis system is established.In the engineering background of a sea-crossing bridge,this thesis introduces the project profile of the bridge.Based on ANSYS software,the finite element model of the bridge is established and its natural vibration characteristics are analyzed.The three-dimensional wind field of the bridge is simplified into one-dimensional wind field of the main beam and one-dimensional wind field of the bridge tower by reasonable simplification.The harmonic synthesis method is used to simulate the fluctuant wind field,and the fluctuant wind simulation program is programmed based on MATLAB.The buffeting force of girder is calculated based on the quasi-steady buffeting force model.Wave field is simulated based on linear wave theory and random wave theory respectively,and wave force calculation theory of small scale pier is adopted in combination with bridge foundation form.The wave simulation and wave force time history calculation are realized by MATLAB programming.The wind-wave load is used as excitation to establish the wind-wave-bridge coupling dynamic equation,and then the wind-wave-bridge coupling analysis system is established.(3)The dynamic response of the bridge is analyzed based on the bridge finite element model and the wind-wave-bridge coupling analysis system.Firstly,the responses resulted from fluctuant wind lonely is calculated: the root mean square of vibration displacement of the deck in three directions and the displacement time history of the three directions in the span of the main beam are calculated,and the vibration patterns of the main beam at different moments are plotted.According to the obtained displacement time history,the frequency spectrum analysis is carried out to analyze the vibration of the main beam.Secondly,wave load conditions are determined according to the hydrologic data of bridge site.The linear wave theory and random wave theory are used to calculate the dynamic response of the bridge under wave action respectively and the differences between the two wave theories are compared and analyzed.For linear wave,the transverse displacement response of bridge under different wave height and wave period is analyzed.Finally,the dynamic responses of the bridge under the combined action of wave and wind are analyzed,and the dynamic responses of the bridge are compared with those of single wind and single wave.The results show that: the joint distribution model of wind and wave can describe the joint probability distribution of wind and wave elements well,which is of positive significance to determine the reasonable wind and wave load.Under the combined action of wind and wave,the dynamic response of the bridge has coupling effect,rather than simple composition of wind and wave.Both wind and wave loads contribute greatly to the transverse vibration of the girder.The vertical vibration is mainly contributed by the wind load while the wave load has little effect.更多还原