摘要
近年来大跨度钢桁架结构以其自身优点广泛地应用在实际工程中。一方面这类结构施工过程复杂,受多种不确定因素的影响；另一方面,传统的结构设计以完整结构为研究对象,而施工是一个非完整结构不断完整的时变过程,加之由于种种因素,施工与设计难免有些脱节,使得按正常使用标准设计的结构内力未必满足施工时的内力要求。凡此种种,都会给实际施工带来了难度和风险。因此有必要对其施工过程进行跟踪模拟分析,及时了解结构的位移和内力在施工期间的变化规律,确保其在整个施工过程中处于可控范围内。
本文以某大跨度钢桁梁桥分段悬臂施工为背景,研究大跨结构施工过程的数值模拟及相关的非线性问题。大跨结构施工过程中的大位移、支座沉降以及各利,结构体系转换等因素使已安装结构和拟安装结构的实际位置和形态不断变化,其施工过程有明显的边界非线性特征。针对传统的“单元生死”方法模拟大跨结构施工出现的缺陷(不能真实的反映拟安装结构安装时的实际位置),论文采用分步建模法,较好地实现了对大跨钢结构桥梁分段施工过程中非线性问题的描述。论文主要内容包括：
(1)介绍施工分析中关键问题和施工数值模拟方法,并着重介绍分步建模法：分步建模法借助了ANSYS的“单元生死”功能,不同的是它是边建模边求解计算；分步建模法考虑了每个工中已安装结构形状和位置变化对拟安装结构位置的影响,其后一工况模型的建立是在前一工况完成的基础上进行的,也就是基于已装结构变形后的状态建立模型求解计算；
(2)针对某大跨度钢桁梁桥施工过程中的边界非线性问题,论文运用分步建模法,模拟了大跨度钢桁梁桥施工全过程的各个关键工况。同时结合现场实测数据对比分析,证明了其方法的合理性,较好地解决了大跨度钢结构分段施工过程中的非线性问题；
(3)对比实际施工方案最终成桥状态和一次性加载方案两者的结构内力分布情况,提出施工优化方案再次模拟计算,并将优化前后的模拟结果与一次性加载方案结果再次进行对比,分析施工过程对成桥结构内力分布状况的影响；
(4)通过上述对比分析,对该工程的施工过程提供建设性意见,并为其它类似工程提供参考。
In recent years, large-span steel-truss structures are more and more widely applied in practical projects for their advantages. On one hand, the construction of this kind of structure is complex, and influenced by many uncertain factors. On the other hand, the traditional structures design research in complete structure but construction is a time-varying process from non complete structure to complete.Meanwhile, the construction and design of the structure inevitably are out of touch sometimes for kinds of reasons and this may make the structural internal force designed according to the normal used standard may not meet the construction requirement. All of these will make the actual construction more difficult. So,it is necessary to make tracking simulation analysis on its construction process, find out the variation of the displacements and internal forces of the structure immediately during the construction period, and ensure the whole construction process in a controllable scope.
This paper uses segmentation cantilever construction in a large-span steel-truss as the research background, and discusses about the construction simulation for the large-span structure and related nonlinear problems in the construction. the whole construction process of the large-span structure is include large displacement, supports settlement as well as a variety of structural systems conversion and other factors which make the actual shape and location of the installed structure and the structure to be installed newly change constantly. All of this make the construction process have boundary nonlinear characteristics. In view of the problem that the results of the traditional method to simulate the construction process with the element birth and death function in ANSYS cannot reflect the actual location of the installed and to be installed structure, this paper uses the step-by-step model method(or named step-by-step model technology) to simulate the whole process of the segmentation cantilever construction of large-span bridge,and solves the nonlinear problem in the construction process very well. The main research includes:
(1)Introducing the key problems in construction mechanical analysis, the construction simulation methods and the Step-by-step model method:this method is base on the element birth and death function of finite element program ANSYS.The different is that it models meanwhile calculates step by step. This method considers the influence of the location changeing of the installed structural on the newly installed structure in each construction step, that is that the newly installed structure in each construction step is built based on the installed structure after deformation.
(2) This paper is in view of the geometry nonlinear problem and boundary nonlinear problem in the process of construction simulation for a large-span structure. With finite element program ANSYS, this paper use the step-by-step model method to simulate the construction process of the large-span steel-truss bridges. Meanwhile, combined with the actual measured data, it proved the rationality of the method and solve the geometry nonlinear problem in the segmentation cantilever construction for the large-span steel structure;
(3)By comparing the design with construction about internal force and linear of bridge model, this paper puts forward the construction optimization scheme and simulation. Then the paper compares the simulation results before and after the optimization again, and analysis the influences that the construction to internal forces and linear of final bridge.
(4)Through the above analysis, the paper provides many constructive suggestions to the process of construction, and provides a reference for the other similar projects.
引文
[1]赵国藩,贡金鑫,赵尚传.工程结构生命全过程可靠度[M].北京：中国铁道出版社,2004.
[2]曹志远.土木工程分析的施工力学与时变力学基础[J].土木工程报,2001,34(3)：41-46.
[3]Choi C K, Kim E D. Multistory frame sunder sequential gravity Loads [J]. Journal of Structural Engineering, ASCE,1985,111(11):2373-2384.
[4]Choi C K, Chung H K, Lee D G, Wilson E L.Simplified building analysis with sequential dead loads-CFM [J]. Journal of Structural Engineering, ASCE,1992,118(4):944-954.
[5]张其林,罗晓群,高振锋,李子旭.大跨钢结构施工过程的数值跟踪和图形模拟[J].同济大学学报,2004,32(10)：1295-1299.
[6]喻永声.考虑施工因素的高层建筑结构性态[J].计算结构力学及应用,1986,3(1)：67-72.
[7]李瑞礼,曹志远.高层建筑结构施工力学分析[J].计算力学学报,1999,16(2)：157-161.
[8]崔晓强,郭彦林,叶可明.大跨度钢结构施工过程的结构分析方法研究[J].工程力学,2006,23(5)：83-88.
[9]方永明,韦承基,戴国莹.高层建筑结构施工模拟分析的剖析[J].上海铁道大学报,1997,18(4)：50-54.
[10]王光远.论时变结构力学[J].土木工程学报,2000,33(6)：105-108.
[11]Tensegrity systems, The State of the Art,International Journal of Space Structures[J], Special Issue on Tensegrity Systems, Vol.7,No.2,1992
[12]Petersen, Jack. Erection and construct ability issues for long-span roofs[J]. Modern Steel Construction.1994,Vol.34, No.2
[13]Meshcherskill I V.Dynamics of a Particle of Variable Mass [J]. PHD Thesis, St Petersburg.1897.
[14]Southwell, R V. An Introduction to the Theory of Elasticity for Engineer and Physicists[M].2nded, Dxdord:Oxford Univ Press,1941.
[15]岳丽娜,陈思甜.钢桁梁桥施工架设方法研究综述[J].公路交通技术,2006.6.
[16]Arutyunyan, N, K. Mathematical model of a dynamically accreted deformable body[M]. Mech of Solids,1990,25(6):80(Part.I);1991,26(1):67(Part.II).
[17]Namov VE.Mechanics of growing deformable soIids A review [J]. J of Eng Mech, 1994, (2):207.
[18]Brown C B, Goodman L E.Gravitation stresses in accreted bodies[J].Proc Royal Soc of London,1963,276(1):571.
[19]李竞.东江大桥钢桁梁合龙参数研究[D].西安：长安大学,2008.
[20]吕国良.三桁刚性悬索桁架桥施工控制研究[D].武汉：武汉理工大学,2009.
[21]颜海建.东江大桥刚性悬索加劲钢桁梁施工技术研究[D].长沙：中南大学,2011.
[22]Z.S.Makowski. Space Structure—A review of Development in last Decades[J]. Space Structure IV, London,1993 vol82:329-346
[23]章惠冬ANSYS单元生死技术软件在结构设计及施工中的应用[J].建筑施工,2008,30(9)：824-826.
[24]K.J.Bathe and H.Ozdemir. Elastic-plastic large deformation static and dynamic analysis [J]. Computer and structures,1976,6:81-92
[25]范重,刘先明,范学伟.国家体育场钢结构施工过程模拟分析[J].建筑结构学报,2007,28(2)：134-143.
[26]刘学军,周岱,黄真.上海新国际博览中心钢结构工程预应力施工技术研究[C].第十届空间结构学术会论文集,2005.
[27]崔晓强,胡玉银.大跨度钢结构施工控制研究[C].第十一届空间结构学术会论文集,2005.
[28]郭彦林,刘学武.钢结构施工力学状态非线性分析方法[J].工程力学,2008,25(10)：19-37.
[29]潘多忠,魏德敏.大跨度结构分步施工模拟方法[J].华南理工大学学报(自然科学版),2010,38(9)
[30]Kharlat V D.Linear theory of creep for a growing body[J].Proc Leiaingrall,1966,49:33.
[31]曹志远.大跨度空间钢结构的施工过程模拟分析及研究[J].时变力学及工程应用.2010
[32]范志良.结构工程科学中若干计算力学问题的研究展望[J].力学进展,1994,24(3)：391-398.
[33]刘西拉.我国结构工程学科应优先发展的领域[J].土木工程学报,1993,26(4)：21-24.
[34]曹志远.近代重大工程分析中的关键力学问题研究[M].上海：上海交通大学出版社,1997.
[35]曹志远.时变元法及其工程应用[J].力学与实践,1999,21(5)：1-4.
[36]胡振东,曹志远.时变元法及其应用[J].固体力学学报,2002,23(1)：104-108.
[37]王光远.论时变力学的拓广[J].工程力学(增刊),1997.
[38]姚金星.土木工程中的时变力学问题[J].荆州师范学院报(自然科报).2000,23(02)：48-50.
[39]王利钧,董旭.大型桥梁施工力学研究[J].武汉理工大学学报,2010,34(5)：949-952.
[40]ANSYS,Inc.Theory Release5.7[S].USA,1998.
[41]潘多忠,魏德敏.大跨度施工力学分析及应用研究[J].华南理工大学学报(自然科学版).
[42]田黎敏,大跨度空间钢结构的施工过程模拟分析及研究[D]，西安：西安建筑科技大学,2010.
[43]曹志远,邹贵平.施工力学分析的时变力学基础[M].现代力学与科技进步,北京：清华大学出版社,1997.320.
[44]Han S,Cho T,Bang M,The sensitivity analysis and safety evaluations of cable stayed bridges based on probabilistic finite element method[J].Korea Struct. Meas. Inst.2007,11(1): 141-154.
[45]Cho Taejun,Kim Tae Soo.Probabilistic risk assessment for the construction phases of bridge construction based on finite element analysis[J].Finite Elements in Analysis and Design,2008,44(5):383-400.
