大跨度异形钢桁架人行桥梁施工技术的探索与实践

以福州城市森林步道工程第1标段跨洪甘路大跨度异形钢桁架人行桥梁为例。该工程钢桁架桥梁为异形构件、桥梁跨度大,吨位重、安装位置特殊,对施工精度要求高。结合工程实践,分析特殊环境条件下,大跨度异形钢桁架人行桥梁施工部署、现场安装的施工方法,探讨解决异形钢桁架跨度大、吨位重的问题,以及在特殊环境下吊装大跨度钢桁架的难题,对今后同类市政桥梁施工具有一定的参考意义。     

某中心大跨度钢桁架施工阶段控制分析研究

某会展中心屋面为大跨度钢桁架结构,结构形式复杂桁架跨度大,施工难度大。根据结构形式特点,采用大型履带吊跨外安装,支撑胎架多段高空原位拼装方法进行屋面钢桁架的安装。介绍了钢结构屋面的施工过程,并采ANSYS软件对钢桁架屋面的施工过程进行计算分析,结果表明单榀桁架在吊装和卸载施工过程中结构应力、变形均能满足安全要求。     

H型钢桁架的结构设计

H型钢桁架是近年来在工业建筑中运用得较为普遍的一种结构形式,相对于传统的角钢桁架而言,更适合于荷载大、跨度大的工业建筑.笔者结合自己工作实践,具体介绍了H型钢桁架的设计过程,通过节点铰接和刚接两种模型的对比,分析了次弯矩对此类桁架内力的影响,并针对H型钢桁架的设计提出了针对性的意见.     

新型预应力组合钢桁架的有限元参数化分析

连云港市某高层建筑结构,由于跨度较大,荷载较大,因此在长跨方向的主梁采用新型预应力钢桁架结构。预应力钢桁架结构上弦为组合梁,主梁跨度方向在下弦圆钢管内布置直线预应力筋,采用SAP2000对其中1榀钢桁架进行有限元参数化分析,研究腹杆截面、混凝土板厚度、预应力筋根数、预应力筋张拉控制应力以及桁架高度的变化对承载力和变形的影响,所得结论可供设计参考。     

某商业中心高空屋盖大跨度重型钢桁架施工技术

汉国城市商业中心大厦在329.4m高的屋盖设置了45m跨度的重型钢桁架。钢桁架结构异形、质量大、跨度大,施工困难。施工中采用了"标准化格构式支撑胎架、架空式底部分配梁、BIM技术模拟预拼装、应力应变监测、有限元分析"等施工技术,高效率、高质量地完成了重型钢桁架的安装。     

重庆来福士广场裙房大跨钢结构安装施工关键技术

重庆来福士广场裙房电影院区域为钢桁架结构,具有跨度大、截面尺寸大、结构体系复杂、空间搭接关系、施工场地复杂等特点。综合考虑后采用大跨度钢桁架分段安装、在分段部位设置临时支撑胎架、高空焊接的施工方法,施工过程中运用有限元软件进行施工全过程模拟分析,从施工顺序、施工荷载影响、临时支撑系统设计与分析等方面解决施工难题,保证结构施工安全与质量。     

大跨度屋面钢桁架提升施工过程分析研究

某新建站房屋面为大跨度钢桁架结构,结构形式较为复杂,跨度大,施工难度也大.根据结构形式特点,钢屋盖结构采取外侧部分吊装和中部部分整体提升相结合的方法进行施工作业.本文采用SAP2000软件对钢桁架屋面进行提升施工仿真模拟,分析施工过程中的索力、结构变形和钢构件应力比等数据,同时对该结构进行不同步提升分析,进而得到杆件的...     

大跨度巨型组合钢桁架整体提升施工技术

天津市滨海新区文化中心(一期)项目文化场馆部分工程地上部分为特大跨度连体结构,结构两侧由4榀双层主桁架+中间支撑组合钢桁架体系连接成整体,组合桁架跨度54 m×宽56 m×高11 m,总质量达3 200 t,桁架安装高度达24 m;通过采用大跨度巨型组合钢桁架整体提升施工技术,解决了大跨度巨型组合钢桁架安装复杂、桁架合龙安装精度要求高、大跨度桁架安装挠度变形大且受温度应力影响较大等问题,降低了施工难度、加快了施工进度、保证了施工质量和安全。     

大跨度异形空间钢桁架安全吊装施工技术

钢桁架具有结构跨度大、异形、施工复杂且常规设备难以完成整体吊装等特点,制定合适的吊装方案是保证钢桁架结构质量和安全的关键。吊装方案的选取需要综合考虑钢桁架吊装过程中结构的应力比和变形、运输难度、高空焊接量、安全性等因素。该文以“中国传感器十大园区”——重庆市传感器特色产业基地暨西部(重庆)科学城北碚园区主出入口大跨度钢结构桁架安装为例,对比分析了各种吊装方案的优缺点。对比发现分三段吊装方案对吊装设备和场地要求低,吊装危险性较低,可实施性较好。在此基础上,结合现场施工环境和工期成本,对大跨度异形钢桁架分段吊装的整体施工流程、施工工艺、技术要点等进行了详细介绍。该工程对大跨度异形钢桁架吊装方案的尝试,为相关复杂工程的吊装方案提供了一定的借鉴。     

螺溪洲大桥方案设计

螺溪洲大桥是一座跨越江西赣江的大型钢桁架景观桥梁,主桥采用跨径布置为(40+70+140+70+40)m的开口式钢桁架结构,中跨上弦杆曲线为二次抛物线,边跨上弦杆为斜直线,上弦无横联或平联。桥梁造型如一座座山峰,层峦叠嶂,结构新颖独特,形成良好的稳定与均衡效果。钢桁架桥梁主体为栓焊结构,采用整体式节点设计,上下弦杆采用箱形截面,桥面系采用正交异性钢桥面结构。常规的钢桁架桥梁存在较多的横联及平联,严重影响桥梁的通透性及景观效果,螺溪洲大桥的开口式钢桁架结构能为此类桥梁设计提供有益参考。     

Optimum design of steel truss arch bridges using a hybrid genetic algorithm

The design of steel truss arch bridges is formulated as an optimization problem. The objective function considered is the weight of the steel truss arch bridge. The objective function is minimized subjected to the design constraints of strength (stress) and serviceability (deflection). An efficient, accurate, and robust algorithm is proposed for optimal design of steel truss arch bridges. The proposed algorithm integrates the concepts of the genetic algorithm (GA) and the finite element method. A real-coded/integer-coded method is used to realistically represent the values of the design variables. Three GA operators consisting of constraint aggregate selection procedure, arithmetic crossover, and non-uniform mutation are proposed. Finite element method is used to compute values of implicit objective functions. A numerical example involving a detailed computational model of a long span steel truss arch bridge with a main span of 552 m is presented to demonstrate the applicability and merits of the proposed method.     

Progressive collapse analysis of steel truss bridges and evaluation of ductility

Deteriorated steel truss bridges have caused catastrophes in the USA and Japan. Progressive collapse analysis is carried out for three continuous steel truss bridge models with a total length of 230.0 m using large deformation and elastic plastic analysis. The analysis is to clarify how the live load intensity and distribution affect ultimate strength and ductility of two steel truss bridge models, Bridge Model A with a span ratio of 1:2:1 and Bridge Model B with a span ratio of 1:1.3:1. Sizes and steel grades of the truss members are determined so that they are within the allowable stress for the design dead and live loads. After the design load is applied, the live load is increased until the bridge model collapses. Although the collapse process differs depending on live load distribution and span length ratio, both steel truss bridge models collapse due to buckling of compression members. When the live load is fully applied in the center span, the span ratio does not affect the ultimate strength which is sufficiently high and the model bridge is safe. When the live load is applied in the side span, the model bridge with a longer side span has higher ultimate strength. When the live load is applied near the intermediate support, the model bridge with a longer center span has higher ultimate strength. As for the ductility factor which is defined by the ultimate load over the yield load, Bridge Model B is in general more ductile than Bridge Model A. This leads to the fact that the center and side span length ratio of Bridge Model B with more commonly used dimensions is rational. This study clarifies the collapse process, buckling strength, and influences of live load distribution and the span ratio on a steel truss bridge.     

PC箱梁与钢桁架组合加劲梁斜拉桥的刚度与稳定分析

探讨预应力混凝土箱梁与钢桁架组合式加劲梁高速铁路斜拉桥的刚度与稳定 ,与无钢桁架PC钢箱梁相比 ,跨径 488m大跨度铁路斜拉桥的活载挠度与跨径之比从 1/4 2 6降低到 1/777,最小整体弹性稳定系数为 11 9。PC钢箱梁与钢桁架组合式加劲梁有效地提高了斜拉桥的刚度和稳定性 ,是大跨度铁路和公铁两用斜拉桥的合理结构形式。     

Model test and numerical analysis of a special joint for a truss bridge

This paper presents a study on the mechanical behaviours of a special joint between a rigid suspension cable and a truss girder in a rigid suspension stiffened steel truss bridge. Both a model test and a numerical finite element analysis (FEA) have been conducted, and relevant information about the models used, loading procedure and test scheme is presented. The model test shows that the maximum stress in the joint is less than the material allowable stress and the maximal stress induced from the secondary moment accounts for about 30% of the total stress. A three-dimensional finite element model is used in the numerical analysis and the results are in very good agreement with those of the model test. This study shows that the design of the special joint is reasonable and the structure safe. It is also expected that the results presented in this paper would be useful as references for future research and design of rigid suspension stiffened steel truss bridges and joints.     

结构健康监测和可靠性评估

对美国最大跨度桁架桥中的主要桁架构件以及整个结构系统的可靠性进行评估。根据构件和系统的可靠性指标,可以采用随机方法评估大跨桥的安全水平。然而,大多数旧的大跨桥是基于允许应力设计的,其可靠性不可能被保证。本研究的可靠性分析基于对恒荷载、活荷载和风载分布的评估。通过收集大量的输入和响应数据,对大桥进行长期结构健康监测。根据外部荷载影响的模式和大小,长期监测数据清楚揭示了不同结构的性能。案例显示,采用传统的分析方法难以确定由于温度引起的结构响应。为探讨温度对结构的影响以及在可靠性评估中考虑长期监测数据的作用,也对温度引起的响应进行分析。研究显示：温度导致的响应对整个系统的可靠性具有明显的影响。     

钢管混凝土在桥梁工程中的应用沿革和现况分析

本文介绍了钢管混凝土结构的特点及其在我国桥梁工程中的应用沿革和现况,统计汇总的跨径100m以上的钢管混凝土拱桥应用情况（跨径200m以上的列表）及其归纳分析,对桥梁工程设计从业人员具有一定的借鉴和参考作用。同时,本文对钢管混凝土在桁式组合拱、桁架桥和斜拉桥中的应用也作了简要的介绍。     

Stress concentration factors of N-joints of concrete-filled tubes subjected to axial loads

The use of concrete filled circular hollow steel section (CFCHS) members in bridge design is a relatively new concept. In the design of recently constructed steel-concrete composite bridges using CFCHS truss girders for the main load carrying structure, the fatigue verification of the tubular spatial truss joints is a main issue. This paper presents a comprehensive study on stress concentration in welded tubular steel N-joints. Finite element analyses are performed in order to derive stress concentration factors (SCFs) from hot-spot stresses for typical three load conditions. The SCF values are presented in the form of equations in terms of the non-dimensional joint parameters. The proposed SCF equation for CFCHS N-joints shows good agreement with the test results on a tubular girder model. The presence of infilled grout in the chord is found to reduce the SCF.     

大跨高位钢桁架转换层结构的实测与分析

浙江省电力调度大楼门厅采用大跨高位钢桁架转换层结构。为消除施工荷载及温度对钢桁架周边结构的影响,施工过程分两阶段进行:第一阶段大跨钢桁架端部混凝土未浇注,钢桁架支座处于可滑动铰支状态;第二阶段,待上部结构封顶后,再将钢桁架端部实行固支。对该钢桁架转换层第一阶段施工全过程的结构应力、位移进行现场试验研究,并将现场实测数据与缩尺模型试验结果进行对比。结果表明:第一施工阶段钢桁架挠度及应力实测值与模型试验值较接近,在温度和施工荷载作用下钢桁架端部产生了一定的水平位移,但其值远小于理想可动铰支模型的计算结果。     

Fatigue evaluation of steel-concrete composite deck in steel truss bridge——A case study

An innovative composite deck system has recently been proposed for improved structural performance. To study the fatigue behavior of a steel-concrete composite bridge deck, we took a newly-constructed rail-cum-road steel truss bridge as a case study. The transverse stress history of the bridge deck near the main truss under the action of a standard fatigue vehicle was calculated using finite element analysis. Due to the fact that fatigue provision remains unavailable in the governing code of highway concrete bridges in China, a preliminary fatigue evaluation was conducted according to the fib Model Code. The results indicate that flexural failure of the bridge deck in the transverse negative bending moment region is the controlling fatigue failure mode. The fatigue life associated with the fatigue fracture of steel reinforcement is 56 years. However, while the top surface of the bridge deck concrete near the truss cracks after just six years, the bridge deck performs with fatigue cracks during most of its design service life. Although fatigue capacity is acceptable under design situations, overloading or understrength may increase its risk of failure. The method presented in this work can be applied to similar bridges for preliminary fatigue assessment.     

#br# 我国钢管混凝土拱桥应用现状与展望

共收集到截止2015年1月的已建和在建的钢管混凝土拱桥413座（跨径不小于50m）。统计分析表明,钢管混凝土拱桥在我国修建的数量不断增多、跨径不断增大。从行业分布来看,在公路、城市桥梁中的应用仍是主体,在铁路尤其是高速铁路中的应用不断增多。在结构体系方面,上承式、中承式、拱梁组合式、飞鸟式和下承式刚架系杆拱5大类,仍为主要应用的桥型,占总数的85%。在截面形式方面,以圆钢管混凝土为基本单元组成的单圆管、哑铃形和桁式是应用的主流。提篮拱被应用于各种桥型,尤其是大跨度铁路桥。无风撑拱主要应用于120m跨径以下的桥梁,且以斜靠拱和拱梁组合桥为主,截面多采用横向刚度较大的形式。拱肋的材料强度不断地提高,钢管以Q345钢为主,混凝土以C40、C50为主。虽然对桥面系强健性的重视在不断提高,然而强健性好的整体式和具有加劲纵梁的悬吊桥面系的应用还不够普及。钢管拱的架设方法仍以支架法、悬臂法和转体法3种为主,其中悬臂拼装法应用最多,适用跨径最大范围也最广。