抹灰砌体拱支护结构在地下室工程上的应用

1概述单层地下室一般需要开挖深度在6m以内的基坑。为了平衡基坑壁土体的侧压力，必须设置用型钢、管材或木柱构成的临时支撑。纵横交错的支撑结构将给基坑开挖施工带来困难。受双排桩支护形式的启发，笔者在某综合楼地下室工程应用抹灰砌体拱支护结构替代临时支撑。该结构用混凝土预制块或砖、石材料浆砌成拱板护壁支挡失稳的上体，利用工程桩作为拱脚支座桩和拉锚桩协助拱板受力。这种拱板一支护桩联合挡土支撑结构称抹灰砌体拱支护结构。抹灰砌体拱支护结构是空间支护体系。沿支护结构纵向有拱板、拱脚桩构成的连拱挡土墙，横向有拱脚桩…     

下承式钢箱提篮系杆拱桥拱肋施工关键技术研究

钢拱桥的施工一般分为梁体与拱肋施工两个步骤,而拱肋施工是钢拱桥施工控制的关键环节。文章以左岸大道拱肋施工为例,通过对拱肋节段划分、支架体系设计、拱肋吊装等过程分析,探讨了大节段拱桥拱肋施工要点,可为后续同类结构施工提供参考借鉴。     

实腹式等截面纯压钢拱的平面内弹性屈曲系数

利用有限单元法对静水压力作用下的圆弧钢拱、沿水平轴分布的竖向均布荷载作用下的抛物线钢拱、沿拱轴线分布的竖向均布荷载作用下的悬链线拱的平面内弹性屈曲进行研究,考虑了屈曲前变形、剪切变形及长细比的影响。得到了三铰拱、两铰拱、固定拱的弹性屈曲系数的数值解。对数值解与传统的经典解进行了对比分析,数值解具有更高的精度。计算结果表明,长细比大约在20~50的范围内时,经典解具有很大的误差,用屈曲系数经典解得到的计算长度系数来进行这类纯压拱的平面内稳定性设计将非常不安全。     

碳纤维加固的“反拱预应力技术”及其提高钢结构承载能力的分析

介绍碳纤维加固钢结构的“反拱预应力技术” ,并在考虑结构状态变化的基础上 ,给出了利用碳纤维加固的“反拱预应力技术”加强钢结构后结构正截面上的应力与应变分布的解析解 ,在理论推导上说明了该技术可以提高钢结构的承载力。     

木拱桥结构形式及中国编木拱技术研究价值

木拱桥在桥梁史中占有重要的地位,文章主要对其发展历史和结构形式,特别是我国的编木拱桥进行了探讨。木拱桥拱肋结构形式可分为木肋、木桁肋、编木拱和其它4种。其中,木肋和木桁肋主要分布在欧洲,而编木拱仅在中国建有并大量留存。同时,肋拱和桁拱在其他材料拱桥中也有大量的应用,并不是木拱的特有形式,而中国编木拱结构形式在其他材料拱桥中并未见到。同时,编木拱相关试验结果与理论分析表明,其结构受力特点与现有结构力学分析结果存在较大差异,并不属于一般的二维平面或三维空间杆系结构。因此,开展编木拱的力学计算方法研究,对于发展结构力学理论也具有重要的理论意义。     

钢筋混凝土拱板屋架预应力施工工艺

最近几年,许多地方正在大量修建粮食储备库。粮食储备库由于保温隔热、防水、防蛀要求高,结构跨度大,通常采用钢筋混凝土拱板屋盖。钢筋混凝土拱板屋盖由钢筋混凝土拱板屋架组成,根据工程实际需要,一般取拱板屋架的跨度为21m、24m,宽度为1．1m、1．2m。为减小拱板屋架的挠度,提高其抗裂度等结构性能,需要对拱板屋架的下弦反槽板采用先张法预应力施工。因此,预应力施工工艺的合适与否是保证拱板屋架施工成功的关键。     

钢箱梁反变形的有限元分析计算与研究

介绍国内外钢结构制造线性控制的一般方法,对展览厅钢箱梁结构预拱模型采用ANSYS有限元软件进行受力分析,计算钢箱梁结构受到自重后的变形情况并拟合出多项式曲线,为结构预拱设计提供依据。     

拱形张弦拱的结构分析与静力性能研究

本文提出平面张弦结构的一种新形式,其下弦索上凹,上弦拱与下弦索之间用竖向拉杆连接,并命名为"拱形张弦拱"。建立索与拱的变形协调方程,导出索力增量与位移关系,用连续化方法给出拱形张弦拱的整体平衡微分方程,采用伽辽金法求得解析解,并与模型试验、非线性有限元分析进行分析比较,证明本文提出的理论公式计算方便、直观精确,可用于拱形张弦拱的分析与计算。对拱形张弦拱的静力性能进行了讨论,包括结构的线性性能、上弦拱的弯曲刚度贡献、挠度与支座水平位移、预应力对结构的影响等方面,对该结构的研究与工程应用有较好的指导意义。     

大跨度双拱架多层工业建筑结构的施工

大跨度双拱架多层建筑结构体系不仅在设计上合理,而且在建筑施工上也比其它结构体系更适宜于工业化。因为在这种结构体系中,除了拱肋、系杆、承重架需在现场制作外,其余构件均可实现工厂化生产,一俟拱架施工完成即可在现场采用机械提升并安装其它构件,所以“双拱架”结构的建造程序,就是按照建筑装配化的施工方式进行的。一般情况下,大跨度双拱架建筑的主体结构施工主要有以下几大部分工作:现浇基础承重架,生产预制构件,拱架拼装浇侧,预应力张拉,吊装。此外,尚有构件间的接头处理,二次浇捣混凝土及楼(屋)面整浇层等。施工程序当基础工程结束后立即进行承重架施工与此同时预制构件拱架各部件和次梁、楼屋面板等,甚至可提前委托预制场加工,这样分线施工可以加快工程进度(见图1施工工艺流程图)。     

大跨度拱壳结构的发展与应用

从砖石拱结构,到后来的薄壳结构,再到大跨度的混凝土拱壳结构,很多工程往往结合采用清水混凝土结构,使拱壳结构的应用得到较全面的发展。大跨度清水混凝土拱壳结构在工程应用上有很多优势,在具体施工上也有很多技术难点,通过克服这些技术难点可以使拱壳结构得到更好的应用。     

悬臂桩桩间有效卸荷区研究

根据悬臂桩的传力特征,研究了其桩间土拱效应的形成机理。按其在空间坐标系的位置,将桩间土拱分为水平拱、竖向拱及临空面拱,指出水平拱效应对卸荷区分布规律起主控作用,继而定义了有效卸荷区范围。从分析桩间土拱效应破坏模式入手,结合岩土强度理论及土拱静力平衡原理,建立了考虑桩间土自重应力及滑坡推力的卸荷区计算模型。基于该模型对滑体强度与临界高度及卸荷区矢高的关系作了一定研究,探讨了几种典型桩背土压力分布模式对卸荷区分布范围的影响。最后采用一工程实例对该模型进行验证。     

Non-linear thermoelastic analysis of steel arch members subjected to fire

This paper addresses the non-linear thermoelastic behaviour of steel arches acted on by a sustained uniformly distributed load, when subjected to elevated temperatures as caused by fire. The steel arch is restrained at its two ends by elastic translational springs in both the horizontal and vertical directions, as well as by counterpart elastic rotational springs, which simulate a generic semi-rigid connection, or restraint by other members in a frame, or when the arch acts as a large-span roofing element supported and restrained by columns. The study is restricted to the thermoelastic structural response of the steel material and therefore the high-temperature effects of catenary action and yielding are not considered; however the important effect of the second order term in the strain–displacement relationship is included. In order to model structural response of an elastically supported steel arch under thermal loading, an alternative geometric formulation is needed since the tangential and radial deflections and rotations as well as the axial compressive force in the member are substantial at the early stage of the fire. The formulation presented in this paper takes into account the degradation of the stiffness of the steel arch prior to yielding at elevated temperatures and it is argued that there are many situations for which analyses of a real fire situation in the thermoelastic range are valid. It is shown that the proposed model agrees well with independent solutions obtained using finite element analyses. The proposed model has significant potential for use in the analysis of restrained steel arches subjected to uniformly distributed load at elevated temperatures, such as large-span roofs and can provide a foundation for codified procedures in design.     

Out-of-plane elastic buckling load and strength design of space truss arch with a rectangular section

The out-of-plane stability of the two-hinged space truss circular arch with a rectangular section is theoretically and numerically investigated in this paper. Firstly, the flexural stiffness and torsional stiffness of space truss arches are deduced. The calculation formula of out-of-plane elastic buckling loads of the space truss arch is derived based on the classical solution of out-of-plane flexural-torsional buckling loads of the solid web arch. However, since the classical solution cannot be used for the calculation of the arch with a small rise-span ratio, the formula for out-of-plane elastic buckling loads of space truss arches subjected to end bending moments is modified. Numerical research of the out-of-plane stability of space truss arches under different load cases shows that the theoretical formula proposed in this paper has good accuracy. Secondly, the design formulas to predict the out-of-plane elastoplastic stability strength of space truss arches subjected to the end bending moment and radial uniform load are presented through introducing a normalized slenderness ratio. By assuming that all components of space truss circular arches bear only axial force, the design formulas to prevent the local buckling of chord and transverse tubes are deduced. Finally, the bearing capacity design equations of space truss arches are proposed under vertical uniform load.     

Buckling of monosymmetric arches under point loads

A finite element procedure is described for analysing the flexural-torsional buckling of arches of monosymmetric cross-section. First an inplane analysis is performed to obtain the distributions of axial force and bending moment in the arch. These are then substituted into the buckling equation for monosymmetric arches, and the resulting eigenvalue problem is solved numerically. Higher order quintic shape functions are used to describe the element displacement fields. The effects of the distances from the arch shear centre axis of point and uniformly distributed loads are also included in the analysis.

Flexural-torsional buckling tests on circular aluminium arches of monosymmetric I-section are also described. The test results for arches subjected to central concentrated point loads are compared with the finite element theory.     

Inelastic buckling and strengths of steel I-section arches with central torsional restraints

The elastic flexural–torsional buckling behaviour of arches with a central elastic torsional restraint has been reported elsewhere by the authors, and it was found that a central elastic torsional restraint restricts the buckling shape of an elastic arch and increases its elastic buckling resistance. However, both the inelastic buckling and strength of arches with a central elastic torsional restraint have hitherto not been investigated. It is not known whether the threshold stiffness for elastic buckling can be applied to arches which buckle inelastically, nor is it known how to determine the strength of steel arches with a central elastic torsional restraint. This paper modifies a finite element model for the nonlinear inelastic flexural–torsional analysis of steel I-section arches by including the effects of elastic restraints, and uses it to investigate the influence of central elastic torsional restraints on the inelastic flexural–torsional buckling and strength of steel I-section arches. It is found that a central elastic torsional restraint increases the strength of steel arches, but that the increase in strength decreases as the modified slenderness of the arches decreases. The threshold value of the stiffness of a central elastic torsional restraint at which the inelastic strength of an arch is equal to that of the corresponding arch with a rigid restraint is related to both the modified slenderness and included angle of the arch. For an arch with a low modified slenderness and with a small included angle which buckles inelastically, the threshold restraint stiffness is much smaller than that for an arch which buckles elastically. Design formulae for the strengths of steel I-section arches in uniform bending and in uniform compression with a central elastic torsional restraint are proposed. Comparisons with finite element results show that the proposed formulae provide good predictions for the strength of thin-walled steel I-section arches with a central elastic torsional restraint.     

拱桥的平面内屈曲性能研究

对系杆拱桥进行有限元建模,分析拱的平面内屈曲长度系数,并将其与EC3中推荐的数值进行比较。首先简要介绍了EC3中针对拱的平面内屈曲性能提出的分析方法。随后说明了系杆拱桥的模型、桥梁特性和计算方法,并进行了参数分析。同时也对拉索损坏的情况进行了讨论。最后归纳了研究结论。     

Flexural-torsional buckling of shallow arches with open thin-walled section under uniform radial loads

An arch with an open thin-walled section that is subjected to a radial load uniformly distributed around the arch axis may suddenly buckle out of its plane of loading and fail in a flexural-torsional buckling mode. The classical flexural-torsional buckling load for an arch with an open thin-walled section under a uniform radial load has been obtained by a number of researchers, based on the consideration that the uniform radial load produces a uniform axial compressive force without in-plane bending prior to the occurrence of flexural-torsional buckling. This assumption is correct for deep arches. However, the uniform radial load may produce substantial bending actions in shallow arches prior to flexural-torsional buckling, and so the classical buckling analysis based on the assumption of uniform axial compression may produce incorrect flexural-torsional buckling loads for shallow arches. This paper investigates the flexural-torsional buckling of shallow arches with an open thin-walled section that are subjected to a radial load uniformly distributed around the arch axis. It is found that shallow arches under a uniform radial load are subjected to combined in-plane compressive and bending actions prior to flexural-torsional buckling, and that using the classical buckling solution for circular arches under uniform compression produces incorrect buckling loads for shallow arches. A rational finite element model is developed for the flexural-torsional buckling and postbuckling analysis of shallow arches with an open thin-walled section, which allows the buckling loads to be obtained correctly.     

绵阳新体育馆屋盖结构设计

绵阳新体育馆是为举办2005年第十三届世界拳击锦标赛建设的主体育馆。体育馆屋盖结构采用四个立体拱架作为主要受力体系,包括两个单跨165m的中拱和两个三跨165m的边拱,拱架之间采用桁架联系和支承屋面。整个结构支承在拱脚和边拱中间部分,共8个支座。主要介绍了绵阳新体育馆的结构体系、拱架曲线、钢结构的分析和设计以及支座基础等各方面内容。经验可供同类工程参考。     

拱脚带水平约束弹簧的车辐拱平面内稳定性能

针对非落地拱承受竖向荷载作用时拱脚水平约束刚度不足会产生水平位移,导致拱脚的受力性能和承载能力发生较大变化的问题,采用ANSYS有限元软件建立拱脚带水平约束弹簧的模无索拱和车辐拱有限元模型。采用数值分析方法分别对无索拱和车辐拱在全跨竖向均布荷载和半跨竖向均布荷载进行一阶弹性和弹塑性分析,研究其拱脚水平弹簧刚度幅值变化对车辐拱受力性能的影响,包括拱脚水平推力和位移的变化、沿拱轴线内力变化和分布以及平面内稳定承载性能等。结果表明:车辐拱中的拉索可以有效约束拱脚的水平位移和减小水平推力,显著提高拱整体刚度和稳定承载力; 车辐拱中的拉索可以有效限制拱脚弹簧刚度幅值的下降对车辐拱内力分布及稳定承载性能的影响; 研究成果为非落地车辐拱及拱脚支承构件的设计提供了依据。