体育场膜结构挑篷设计分析

膜结构在体育场屋顶或者看台挑篷中有着广泛的应用。由于膜结构在风荷载作用下有向上掀的倾向 ,再加上张力膜需要提供预应力 ,给膜支撑结构设计带来了很多特殊性。以杭州下沙的某体育场膜结构挑篷设计、分析为依托 ,探讨几种方案的优劣 ,为今后进一步研究和设计提供了有益的结论。     

Ultimate strength of large scale reinforced concrete thin shell structures

This paper presents ultimate behavior of large scale reinforced concrete shell structures: hyperbolic cooling tower shell and hyperbolic paraboloid (HP) saddle shell. Both geometrical and material nonlinearities were considered in the analysis. To investigate the influence of concrete tension cracks on the structural behavior, the smeared crack model having the capability of representing double crack and crack rotation was used in the analysis. The biaxial stress state in shells is represented by the improved work-hardening plasticity concrete model, where the ductility increase phenomenon can be depicted. The load-displacement relationship, stress fields, occurrence and propagation of cracks in concrete and steel yield patterns are presented. Due to the factors such as modification in plasticity model, stiffness contribution in the doubly cracked elements, the model predicts a more ductile behavior than the results reported in the current literature. The failure of cooling tower shell seems to occur due to local yielding of meridional reinforcement in the windward meridian. In the case of HP saddle shell, structural instability occurs due to severe tension cracks in the shell part before yielding of reinforcement could occur.     

Data Parallel Neural Dynamics Model for Integrated Design of Large Steel Structures

We have two objectives in creating novel design theories and computational models: automation and optimization. These two aspects are particularly important in design of complex and large engineering structures. In this article, a robust data parallel neural dynamics model is presented for discrete optimization of large steel structures based on the AISC ASD or LRFD specifications. The computational model has been implemented on a CM–5 supercomputer and applied to integrated minimum–weight design of two steel high–rise building structures. The largest example is a 144–story modified tube–in–tube super–high–rise building structure with 20,096 members. Optimization of such a large structure subjected to the highly nonlinear constraints of actual design codes, such as the AISC LRFD code, where nonlinear second–order effects have to be taken into account, has never been attempted before. The computational model developed in this research finds the minimum–weight design for this very large structure subjected to multiple dead, live, and wind loadings in three different directions automatically. This research demonstrates how a new level in design automation is achieved through the ingenious use of a novel computational paradigm and new high–performance computer architecture.     

Rational design method for bituminous pavements reinforced by geogrid

Geosynthetics have been a reinforced solution for pavement structures for more than 80 years and could be effective in extending its service life. There is a lack of consolidated design methods for pavement with this reinforcement. Therefore, this work aims at proposing a new rational design approach for reinforced structures based on the French design method. In this approach, the geogrid contribution was included by improving the fatigue and rutting properties of some layers, using coefficients named k_maj and k_{maj_Z}. Three hypotheses were considered concerning the condition of an old bituminous layer remaining from rehabilitation works. The first one considered this layer in healthy condition to simulate a new reinforced structure. The second one considered it as cracked and the third one as disintegrated to simulate the design for rehabilitation. Two placement positions and two geogrid-interface conditions (bonded and not bonded) were analyzed. The results indicated that the geogrid was most effective in a completely deteriorated structure and it should be placed in the lowest possible position in the bound layers. This method can be used for any geogrid position within the structure. Lastly, the reinforcement by geogrid allows a reduction of the thickness of the layer above it.     

土工布加筋基础的一维非线性模型(英文)

本文推导出一个代表软土双曲线弹簧支撑的土工布加筋基础一维非线性模型。该模型的数学形式是两个非线性二阶常微分方程组。给出了解常微分方程组的迭代格式，并着重讨论了非线性弹簧参数对加筋基础的沉降和土工布拉力的影响。     

改进的复形法与索承网壳结构的索力优化

根据索承网壳结构受力特点 ,从适合工程应用的角度出发 ,提出双控目标函数满意度法 ,建立索力优化的数学模型 ,采用改进的复形法研究了选定截面情况下的索力优化 ,并附有算例 ,对其结构设计以及工程应用有一定参考价值。该法可供索拱结构、张弦梁结构等空间杂交索结构体系的索力优化借鉴。     

点支式玻璃幕墙张拉索杆支承体系自振特性参数分析

张拉索杆结构是点支式玻璃幕墙最常见的支承体系之一,属于一种柔性结构,对外荷载的作用比较敏感。建立了点支式玻璃幕墙张拉索杆支承体系的非线性动力特性分析的有限元模型,分析了该结构的自振频率与各阶振型,并进一步研究了初始预拉力、拉索截面面积、撑杆截面面积和撑杆长度几个主要的设计参数以及玻璃质量变化对该结构的自振频率的影响。     

烟台体育中心体育场罩棚结构设计

烟台体育中心体育场罩棚跨度45m,由两片月牙造型的空间结构组成,采用骨架和张拉结合的膜结构,主受力结构由带大型拉压杆的立体桁架和跨度284m的拱架组成。结构的杆件选用圆钢管,节点为相贯焊接节点,膜材选用PVC材料。结合具体的结构设计,详细介绍了罩棚的结构体系;分析了结构的静力性能、动力特性以及温度对结构的影响。对结构稳定的研究结果表明结构稳定满足规范要求,不会发生整体屈曲。介绍了结构优化和节点设计的基本内容。     

大跨度钢桁架-混凝土组合楼盖整体模型试验研究

通过对一种新型的45m大跨度钢桁架-混凝土组合楼盖进行缩尺比为1∶9的整体模型试验,检测了该组合楼盖的受力变形性能及钢桁架与混凝土的共同工作情况,进而验证所用计算方法的可靠性;通过实测模型结构的强度、刚度指标,结合理论分析结果揭示实际工程具有足够的安全度。试验结果和理论分析的对比证明了此种大跨度钢桁架-混凝土组合楼盖能够充分发挥钢材受拉和混凝土受压的优点,具有良好的受力性能,特别适用于重荷载、大跨度、小结构高度的楼盖结构。     

设计阶段建筑结构系统造价的优化分析

通过对建筑结构系统分析,说明了设计建筑结构的基本原则和计算建筑结构造价的基本方法,建立了建筑结构系统经济优化的通用模型。结合常见的钢筋混凝土结构,具体分析了优化模型在钢筋混凝土结构设计阶段的应用。通过编译计算机程序,可以较方便地求解最佳结构设计方案。文中以某四层双跨框架结构为例,对比分析了该框架结构的初始方案与优化方案,发展经优化后的方案造价比初始方案造价节省了２．９％,经济效果比较明显。     

Dynamic response of tension leg platforms with axisymmetric members

In the design of a tension leg platform (TLP), variation in tether tension should be minimized to inhibit fatigue failure. A stable platform must be maintained with small motions, the tension legs serving to inhibit roll, pitch, and heave in shallower waters. In deep water, however, the tether elongations may lead to significant values of these motions. TLPs are extremely compliant systems when horizontal plane motions are considered. The legs provide nonlinear restoring forces because of the interactions of the prestress with the surge and sway motions. For fixed structures, and for complaint TLPs having characteristic member dimensions no longer negligible compared to the incident wavelength, the Morison equation assumption is no longer valid, and a diffraction theory is needed to account for the additional pressure field developed.In the case of a TLP, the wave-induced motion of the floating structure creates an additional reaction force on the structure. The wave-induced pressure forces are linearly decomposed into two components: a diffraction force on a fixed structure, and a reaction force on an oscillating structure in otherwise still water.Numerical algorithms have been developed from a Green's function solution for fixed structures of arbitrary shape. Numerical computations can be significantly improved for axisymmetric bodies by using an eigenfunction expansion of the Green's function. A numerical algorithm is presented that computes the wave-induced forces and moments on the large members of a TLP using an axisymmetric Green's function, and an option of using the relative motion Morison equation for selected members.     

Pseudodynamic testing and nonlinear substructuring of damaging structures under earthquake loading

Pseudodynamic or PSD testing with substructuring technique is a highly relevant approach to capture the dynamic failure mechanisms of a structure. It allows one to realistically test a structure subject to an earthquake with accessible experimental equipment. We propose in this paper to apply such a PSD testing with substructuring to damaging structures, where the nonlinear behaviour is represented by an advanced damage model: an anisotropic damage model, initially proposed for monotonic applications, is upgraded in order to asses cyclic and seismic loading. The keypoint is the macroscopic representation of the microcrack closure (the cracks generated in tension close in compression) and its effect on stiffness recovery. The chain–PSD testing/advanced damage model/experimental measure setup based on image correlations–is successfully used for the study of the failure of a reinforced concrete frame structure.     

预应力拉杆式张弦梁性能和施工工艺研究

在张弦梁中用预应力拉杆代替拉索,其结构性能发生变化;通过分析比较得出预应力拉杆式张弦梁的性能特点和设计中应当注意的事项。结合工程实际介绍拉杆式预应力张弦梁在安装、张拉和成形时应当注意的问题。     

南京市某高层商住楼框支剪力墙结构设计

介绍了某高层商住楼框支剪力墙结构的设计,包括结构概念设计、结构三维整体分析,弹性动力时程分析、转换层有限元分析。指出这类结构体系的设计应从概念设计出发,制定合理的方案,通过正确的模型计算,找出结构薄弱部位,予以加强。文中同时指出,框支剪力墙转换梁不一定是偏心受拉构件。     

轴旋转结构大钢模板的设计及现场测试分析

模板体系是新浇混凝土成型用的模型,在混凝土结构施工中起着重要作用。目前,轴旋转曲面结构混凝土浇注过程中,模板体系均采用传统的模板配合脚手架的施工工艺,模板自身不能承受环向力作用,施工难度大、安全隐患多。针对现有轴旋转结构模板体系设计存在的不足,对大钢模板进行改进,并结合有限元分析,设计出能承受一定环向力的大钢模板;以某轴旋转结构为例,基于对该结构大钢模板施工中的应力测试,分析大钢模板在施工作用下内力的分布和变化规律。实测结果表明,该模板的设计是合理的。     

索膜结构风振响应中的气弹耦合效应研究

大跨度张力结构(以索膜结构为代表)的风振性能研究一直是结构风工程领域的热点问题之一,特别是涉及到对风-结构的气弹耦合效应估算时,因其具有较大的理论难度,至今尚未得到较好解决。本文首先对索膜结构风振分析问题的特点和一些主要研究方法进行了评述,然后着重介绍了目前在考虑气弹耦合效应时的索膜结构风振性能研究进展情况,最后对进一步的研究工作提出了展望。研究表明,大跨度张拉结构与风的动力耦合作用与桥梁和高层结构相比并不完全相同,而是具有明显的自身特点,这对于今后的研究方向和研究重点具有重要的指导意义。     

Reliability based determination of material partial safety factors for cast iron beams in jack arched construction exposed to standard and natural fires

Cast iron beams were extensively used in many 19th century structures, especially in fireproof flooring systems (such as jack arch). Many such structures are still in use today and it is important that they fulfil the current requirements of fire resistance when there is a change of use. These structures are out of scope of modern design codes and old design codes do not provide guidance for fire resistance design. Furthermore, cast iron is a brittle material weak in tension, and there are many uncertainties in its mechanical properties at ambient and elevated temperatures due to material flaws. It is necessary to quantify the probability of structural failure and to introduce safety factors to reduce the probability of structural failure in fire to an acceptable level. This paper presents the results of a detailed study whose purpose is to derive appropriate safety factors to achieve different levels of reliability, for fire safety design of cast iron beams. In this study, a fibre analysis method has been used to calculate the moment capacity of four different types of cast iron cross section. Using randomized stress-strain-temperature relationships, based on variability of the different governing parameters (under tension: maximum stress, 0.2% proof stress, corresponding strains at maximum stress (strength) and failure; under compression: Young's modulus, proportional limit, 0.2% proof stress and the maximum stress), the probability distribution of moment capacity has been calculated. Based on the criterion of cast iron beam failure not exceeding probabilities of 10⁻¹, 10⁻² and 10⁻³, material safety factors of 1.5, 3.0 and 5.0 respectively have been obtained.     

葵花三撑杆Ⅱ型索穹顶结构预应力态确定、参数分析及试设计

提出一种新型葵花三撑杆Ⅱ型索穹顶的结构构形,该结构不沿用Fuller"拉索海洋与压杆孤岛"传统意义上张拉整体构想,而是在下弦节点处采用了3根撑杆交汇的布置方案(Ⅱ型),可使一道环索管辖两圈脊索,上弦网格数不变时斜索和环索可减少一半,提高张拉施工便易性,并改善局部及整体结构的稳定性.根据节点平衡方程,推导了葵花三撑杆Ⅱ型...     

某大型双曲冷却塔风荷载作用效应有限元计算

运用三维有限元方法,对某超大型双曲冷却塔进行了模态和风荷载作用效应计算,分析了冷却塔的动力特性,计算了结构在风荷载作用下的应力和变形情况,研究结果可为类似工程提供参考。     

弦支双曲扁网壳结构的鲁棒构型分析及试验研究

针对不良拓扑布置导致的结构鲁棒性不佳问题，以系统传递函数的H₂范数为基础，建立结构鲁棒性定量评价指标和鲁棒构型求解方法。以单元相对密度为设计变量，采用变密度模型描述材料的刚度，将结构的鲁棒设计转化为连续体拓扑优化，并对大爆炸算法进行二级搜索的改进，进而求解连续体拓扑优化模型。以四点支承的弦支双曲扁网壳结构为例，分析不同荷载作用下的鲁棒构型，探索不同参数的大爆炸算法优化效果，通过静力试验和冲击试验，对优化后模型和未优化模型进行对比分析。结果表明，二级搜索的大爆炸算法可以有效地应用于弦支结构的鲁棒设计中，改进的大爆炸算法加快了收敛速度，依据鲁棒构型进行杆件布置，可显著提高结构的力学性能和抗干扰能力。