【作者】 张国发；

【导师】 董石麟； 卓新；

【作者基本信息】 浙江大学 ， 结构工程， 2009， 博士

【摘要】 弦支穹顶结构是由上部单层网壳和下部索杆支承体系构成的大跨预应力杂交结构,由于其造型新颖、结构受力性能优越、施工难度相对较小,得到了国内外工程界的青睐,但在实际工程应用中,在结构设计、施工及使用过程中仍然存在一些问题。为推动该类结构在工程中更好的应用,本文对弦支穹顶结构的预应力水平优化、缺陷状态的预应力调整、施工滑移索的摩擦影响、新型节点设计、模型试验等内容进行了深入的研究。首先,本文建立了弦支穹顶结构预应力优化数学模型,运用NSGA-Ⅱ优化算法,以各圈环索预应力水平为变量,以各圈环索总预应力水平最低、结构水平径向支反力最小、上部单层网壳杆件轴向应力峰值最小为目标函数,考虑结构强度和挠度限制,对弦支穹顶结构的预应力水平进行多目标优化。揭示了随着各圈环索预应力水平的不同组合,结构各目标函数的变化规律,为工程设计决策提供了依据。为解决由于构件制作、施工误差与算法误差等原因造成的弦支穹顶结构处于缺陷状态的问题,本文提出了张力修正法和位移补偿计算法两种预应力分析方法。张力修正法是基于力控制的预应力调整方法,而位移补偿计算法是基于变形控制的预应力修正方法。计算结果表明,对施工期或使用期预应力存在较大误差的结构以实测的拉索预应力值或控制节点坐标为依据,采用本文提出的两种分析方法得到的预应力修正控制值,可有序、简捷、准确的对结构缺陷状态的预应力进行调整,使结构达到设计状态或满足施工精度要求。本文提出了一种基于结构性能分析的弦支穹顶结构缺陷状态预应力调整的方法,先考虑拉索预应力误差、节点位置偏差等结构缺陷状态的误差因素,对结构静力、动力、稳定性能进行敏感性分析,再以敏感性分析的结果为依据,运用层次分析法确定结构误差因素的权重,最后运用遗传算法对结构缺陷状态进行预应力调整优化,得到使结构性能最优的预应力调整方案。为解决模拟考虑摩擦影响的连续索在节点处滑移问题,本文提出了变索原长法,先不考虑结构变形协调,使索在节点处发生滑移,根据力学平衡条件及滑移区段索原长不变的原则可求得每段索滑移平衡后的索原长,把新的索原长代入后再对结构进行变形协调计算,从而完成索段的一次滑移计算。研究结果表明,变索原长法可用于模拟考虑摩擦影响的索滑移问题,且计算方便快捷。本文对考虑施工滑移索摩擦影响的葵花型弦支穹顶结构性能进行了研究,分析了结构静力、动力及稳定性能,并提出了两种新型节点形式。计算结果表明,环索与节点间的摩擦会导致结构环索及斜索张力重分布,致使同圈索力分布不均匀,使部分网壳杆件轴向应力和节点位移增大,对结构的静力性能影响最大,而对动力和稳定性能基本没有影响。最后,以一实际工程为背景,制作了跨度为8m的弦支穹顶结构缩尺模型,并设计、制作了传统节点和新型节点两种节点模型。对采用两种节点形式的结构模型进行了环索张拉成型、满跨加载、半跨加载及环索超张拉试验。试验表明,由于环索与节点间存在摩擦,使得各工况下结构各圈环索和斜索张力分布不均匀;与传统节点相比,采用新型节点的结构环索与节点间的摩擦大幅降低,环索预应力损失较小,预应力传递效率更高。与此同时,通过试验验证了本文提出的变索原长法的正确性。更多还原

【Abstract】 Suspen-dome system is a prestressed long-span spatial hybrid structure,which consists of the topmost single-layer dome and the bottom tensegrity system,and it has been widely applied around the world due to its novel appearance,excellent structure properties and low difficulty of construction.However,there are still some problems in process of tension constrction and actual using.In order to promote the application of this kind of structure to practical engineering, this article carried out deep study on prestress optimization,adjustment on defect state,effect of friction in sliding-cable during tension construction,design of new joints and model experiment in the suspen-dome system.First of all,this paper set up an optimization mathematical model of prestress in suspen-dome structure,taking the prestress level of each hoop cable for variable,the lowest total prestress level of each hoop cable,the minimum value of horizontal radial support reactions,and the minimum peak value of members’ axial stress in the topmost single-layer dome for objective function,Non-dominated Sorting Genetic AlgorithmⅡ(NSGA-Ⅱ) was used to make multi-objective optimization calculation for the prestress level of suspen-dome structure, considering the structural strength and deflection limits.The results revealed the rule that every objective function of the structure varied with the prestress level of every hoop cable,which provides the basis for decision-making in engineering design.In order to solve the prestress adjustment on defect state of the suspen-dome system,this paper proposed two kinds of analysis methods,modified tension method and displacement compensation method.Modified tension method is a precise prestress adjustment method based on force controlling,and the displacement compensation method is a prestress correction method based on deformation controlling.According to the measured prestress values of cables or the coordinate values of controlled nodes of structure with great prestress deviation in construction period or usage period,the results show that the two methods proposed in this paper can be applied to obtain modified prestress controlled values and they also can be used to adjust the prestress on defect state in structure orderly,simply and accurately and make structure meet the requirements of design and construction precision.The method presented in this paper is based on structure behavior analysis to adjust prestress on defect state of the suspen-dome system.First,carry out structural static,dynamic and stability sensitivity analysis considering the structural defect factors such as prestress deviation of cable and node location deflection,then determine the weight of structural defects according to the results of the sensitivity analysis,at last,use the genetic algorithm to adjust and optimize prestress on the defect state of structure in order to obtain the prestress adjusting scheme which will make the structural properties the optimal.The modified original length method proposed in this paper is aim to solve the problem of simulating cable sliding at joint with friction effect.First,allow the cable slid at joint ignoring the structural deformation compatibility.The original length of every cable section can be obtained after sliding balance based on equilibrium equation and the invariability of total original length of those continuous sliding cables.Then,solving the compatibility equation with updated original cable length to get the sliding results and complete one sliding calculation of cable sections.The research results show that the modified original length method can be used in the problem of simulating cable sliding at joint with friction effect,and the calculation is simple and convenient.In this paper,structural performance of sunflower-patterned suspen-dome were studied, taking into account the friction impact of sliding-cable during construction process,the static, dynamic and stability characteristic of structure were analyzed,and two new of joint were proposed.The results show that the friction between hoop cable and joint will cause tension redistribution in hoop and radial cable of structure,led to uneven force distribution of the same hoop cable,increase displacement of some joints and axial stress of some bars in the lattice shell, and static properties of the structure will be obviously affected,but the dynamic and stability characteristic almost will not.Finally,used a practical engineering as reference,a scale model of suspen-dome structure with span of 8m was made,including models of traditional joints and new joints.Structure model adopting both two types of joints was tested in shape forming processing,under full-span load and half-span load,and was excess stretched on hoop cable.The tests showed that the tension of each hoop cable and radial cable distributed unevenly under various working conditions,because of the friction between hoop cable and joints.Compared with the traditional joints,using new joints in structure could make the friction between hoop cable and joints reduce obviously,and friction loss on hoop cable at joints was small.Meantime the moditied original cable length method proposed in this paper was proved correct through the experiment.更多还原