摘要
随着我国国民经济的蓬勃发展,各地掀起了兴建跨河、跨海桥梁的热潮。由于桥梁的跨度不断增大,新型桥的出现,施工控制技术日益受到工程界的关注。毋庸置疑,基础是桥梁结构重要的组成部分之一,没有牢固的基础就不能保证桥梁结构的稳定性。基础施工质量的好坏直接影响到结构的可靠性,而施工平台是大型结构基础施工的前奏。
桩间联系是下部桩柱之间用来加强联系,提高稳定性的构件,桩间联系的形式、刚度及位置的设置对施工平台的稳定性有直接影响。本文在实体模型分析前,对相关的基础理论进行了阐述。首先,介绍了目前国内外深水墩施工平台体系的设计研究现状,阐述深水墩施工平台的特点;接着,对两类稳定问题分别进行较细致的论述,探讨了两类稳定问题的有限元求解方式;然后介绍了波浪理论,着重介绍了线性波浪理论、Stokes三阶波理论以及Morison理论。
为了清楚地了解影响施工平台稳定性的因素,研究中采用了多种计算模式:首先,根据施工平台桩间联系的位置,分成三种结构模型;再根据吊机位置的布置,分成六种工况;最后,又采用两种方法分别计算水流力对平台的作用。作者运用ANSYS软件建立了36种计算模式,通过计算,获得了平台的稳定系数,并绘出三组描述桩间联系构件水下深度的位置与稳定系数的关系曲线。根据上述曲线,得到以下结论:桩间联系的位置越靠近下部桩柱的底部,施工平台的稳定系数越大,稳定性越好。当然,桩间联系的位置越低,水下作业的施工难度越高。
计算施工平台的稳定性,是为了满足安全性、适用性和耐久性的要求,设计时应综合考虑设计和施工两方面的因素,使设计与施工相辅相成。
With the flourishing development of the economy in our country, many cross-river and cross-sea bridges are built in many places. Due to the longer span of the bridges and the emergence of new types of bridges, more attention has been paid to the construction control technology in engineering community. Undoubtedly, the foundation is one of the most important parts of the bridge architecture. It is impossible to guarantee the stability of the architecture without well-grounded foundation. So, the quality of the foundation directly affects the reliability of the structure, and construction platform is the prelude of the large architecture’s foundation construction.
The couplings-among-piles are the components which are used to enhance couples among below piles and increase stability. The form, stiffness and positions setting of the coupling-during-piles have direct effect on the stability of the construction platform. This paper expatiates relevant basic theories before the analysis the entity model. Firstly, it introduces the present situation of the researches into the construction platform system of depth pier at home and abroad, and narrates its characteristic. Secondly, this paper discusses two kinds of problems on stability in detail and probes into their FEM solution methods. Thirdly, this paper introduces wave theories with the emphasis on the linear wave theory, Stokes three-order wave theory and Morison theory.
Many calculation models are adopted in this research in order to get a clear picture of the factors that affect the stability of the construction platform. Firstly, three structure models are projected on the basis of the position of the couplings-among-piles of the platform. Secondly, six work conditions are planned according to the arrangement of the cranes. At last, the effect of the wave load on the platform is calculated in two ways. Through software ANSYS, thirty-six calculation models are set up, their stable coefficients are calculated and three groups of curves that describe the relationship of the stable coefficient and the underwater depth of the couplings-among-piles are drawn. On the basis of the above-mentioned curves, the following conclusion can be drawn: the nearer the position of the couplings-among-piles is to the bottom of the piers, the bigger the stable coefficient of the construction platform is, which means that it is more stable. Of course, the lower the position of the couplings-among-piles is, the more difficult is underwater working.
Calculating the stable coefficient of the construction platform is to meet the demand of the security, applicability and durability. Design and construction should be considered integratively during designing in order that they can supple and complement each other.
引文
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