【作者】 刘强；

【导师】 秦顺全；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2020， 硕士

【摘要】 21世纪以来,为加快对海洋开发的步伐和促进沿海地区经济快速发展,我国先后多座跨海特大型桥梁已建成或正在规划。海上施工栈桥作为一种可以在海洋上快速化装配的施工辅助设施,在我国跨海桥梁建设中得到广泛应用。与陆地环境不同,海洋环境极其复杂恶劣,这也使得修建于其中的海上施工栈桥不可避免地遭受各种恶劣的自然作用,其中,极端波浪和海流是造成海上施工栈桥破坏的关键因素,给海上施工栈桥的正常服役带来了严峻挑战。本文在归纳与梳理现有文献的基础上,以平潭海峡公铁两用大桥海上施工栈桥为工程背景,采用数值模拟结合理论推导的研究手段,对其在波流作用下的承载性能以及可靠度相关问题展开了系列研究与分析。主要研究内容与结论包括:(1)提出了波流作用下海上施工栈桥承载性能评估方法,并以平潭海峡公铁两用大桥所使用的海上施工栈桥为例,详细给出了该方法的实现流程,并研究了极端波流作用下海上施工栈桥的倒塌失效机制。研究结果表明,本文方法可同时考虑波高、流速变化对结构侧向力分布的影响,能反映结构在不同波流荷载作用下的响应信息,为服役海上施工栈桥全尺度荷载强度下的安全评估提供数据支持;损伤临界线可更为直观衡量海上施工栈桥的承载性能;海上施工栈桥的薄弱部位位于钢管桩底部及支撑框架下横撑与钢管桩相交节点的附近钢管桩单元处。(2)基于波流作用下海上施工栈桥承载性能评估方法,系统地研究了环境腐蚀、海洋附着物、钢管桩长度三个因素对海上施工栈桥承载性能的影响规律,建立了腐蚀时间、海洋附着物厚度、钢管桩长度与海上施工栈桥极限承载能力之间的数学关系。研究结果表明,随着腐蚀时间的增长,海上施工栈桥极限承载能力均先缓慢减小,随后迅速减小,最后趋于稳定;随着海洋附着物厚度或者钢管桩长度的增大,海上施工栈桥极限承载能力均呈近似线性减小的趋势,且以上三种影响因素并不改变结构的倒塌失效机制;借助于本文所提出的数学公式可快速获取考虑以上因素影响下海上施工栈桥的承载性能。(3)基于最优线性无偏估计的Kriging模型,并结合良好空间填充性的拉丁超立方抽样技术,提出了一种海上施工栈桥可靠度分析方法,基于该方法求解了海上施工栈桥的可靠度指标,并将该方法的计算结果及分析时间和Monte Carlo法、拉丁超立方法进行对比;同时采用本文方法并结合所提出的数学公式研究了环境腐蚀、海洋附着物、钢管桩长度对海上施工栈桥可靠度的影响规律。研究结果表明,相比于Monte Carlo法和拉丁超立方法,基于Kriging模型的海上施工栈桥可靠度分析方法能以更少的计算量得到海上施工栈桥较为准确的可靠度指标,可作为海上施工栈桥可靠度分析的有力手段;随着腐蚀时间的增长,海上施工栈桥的可靠度指标先缓慢减小,随后迅速减小最后趋于平稳状态;随着海洋附着物厚度的增大或者钢管桩长度的增大,海上施工栈桥的可靠度指标呈线性减小趋势。更多还原

【Abstract】 To speed up marine development and promote the rapid economic development of coastal areas,many sea-crossing bridges have been built or are being planned in China since the 21 st century.As a kind of construction auxiliary facility that can be assembled quickly in the ocean,offshore construction trestle has been widely used in the construction of sea-crossing bridges.Different from the land environment,the marine environment is extremely complex and harsh,which makes offshore construction trestle suffer from various adverse natural hazards inevitably.Among them,extreme waves and currents are the critical factors for the destruction of offshore construction trestles,which poses serious challenges to the serviceability of offshore construction trestles.Based on a thorough analysis of the existing problems in the literature,this thesis takes the offshore construction trestle of Pingtan Straits Rail-cum-Road Bridge as the research object,and the bearing performance and reliability of offshore construction trestle under wave and current loads are studied systematically by numerical simulation and theoretical derivation.The main works and conclusions are listed as follows:(1)An evaluation method of bearing performance of offshore construction trestle under wave and current loads is proposed.To show how to implement this method in detail,the bearing performance of the offshore construction trestle of Pingtan Straits Rail-cum-Road Bridge is studied using the proposed evaluation method,and the collapse mechanism of the trestle is clarified additionally.The results show that this method can consider the influence of wave height and current speed on the lateral force distribution of the trestle simultaneously,can reflect the response information of the trestle under different wave and current loads,and provide data support for the safety assessment of the trestle under full-scale load intensity.Damage critical lines can more intuitively measure the bearing performance of offshore construction trestle.The weak parts of the trestle locate at the bottom of steel pipe pile piles and the adjacent elements of the joints between crossing braces and steel pipe piles under supporting frames.(2)Based on the evaluation method proposed above,the influences of environmental corrosion,marine growth and the length of steel pipe pile on the bearing performance of trestle are investigated systematically,and the mathematical formulas between the corrosion time,thickness of marine growth,length of steel pipe pile and ultimate bearing capacities of trestle are established,respectively.The results show that,with the increase of corrosion time,the ultimate bearing capacities of the trestle first slowly decreases,then rapidly decreases,and finally tends to be stable.With the increase of the thickness of marine growth or the length of steel pipe piles,the ultimate bearing capacities of the trestle almost decreases linearly,and the above three factors do not change the failure process of the trestle.The bearing performance of the trestle considering the influences of the above factors can be obtained quickly with the mathematical formulas proposed in this paper.(3)Based on Kriging model of optimal linear unbiased estimation and Latin hypercube sampling technology with good space-filling,a reliability analysis method for offshore construction trestle is proposed.The reliability index of offshore construction trestle is solved using this method,and the reliability results and calculation time of this method are compared with those of Monte Carlo and Latin hypercube sampling methods.Moreover,the influences of environmental corrosion,marine growth,and length of steel pipe pile on the reliability of trestle are studied by this method with the mathematical formulas proposed above.The results show that compared with Monte Carlo and Latin hypercube sampling methods,the proposed method can provide an almost accurate reliability index of trestle with less calculation,which is a powerful method for reliability analysis of offshore construction trestle.With the increase of corrosion time,the reliability index of trestle decreases slowly first,then decreases rapidly and finally tends to be stable,and with the increase of the thickness of marine growth or length of steel pipe pile,the reliability index of trestle decreases linearly.更多还原