Seismic response of the long-span steel truss arch bridge with the thrust under multidimensional excitation

Purpose–Under different ground motion excitation modes,the spatial coupling effect of seismic response for the arch bridge with thrust,seismic weak parts and the internal force components of the control section of main arch ribs are analyzed.Design/methodology/approach–Taking a 490 m deck type railway steel truss arch bridge as the background,the dynamic calculation model of the whole bridge was established by SAP2000 software.The seismic response analyses under one-,two-and three-dimension(1D,2D and 3D)uniform ground motion excitations were carried out.Findings–For the steel truss arch bridge composed of multiple arch ribs,any single direction ground motion excitation will cause large axial force in the chord of arch rib.The axial force caused by transverse and vertical ground motion excitation in the chord of arch crown area is 1.4–3.6 times of the corresponding axial force under longitudinal seismic excitation.The in-plane bending moment caused by the lower chord at the vault is 4.2–5.5 times of the corresponding bending moment under the longitudinal seismic excitation.For the bottom chord of arch rib,the arch foot is the weak part of earthquake resistance,but for the upper chord of arch rib,the arch foot,arch crown and the intersection of column and upper chord can all be the potential earthquake-resistant weak parts.The normal stress of the bottom chord of the arch rib under multidimensional excitation is mainly caused by the axial force,but the normal stress of the upper chord of the arch rib is caused by the axial force,in-plane and out of plane bending moment.Originality/value–The research provides specific suggestions for ground motion excitation mode and also provides reference information for the earthquake-resistant weak part and seismic design of long-span deck type railway steel truss arch bridges.

Defect Inspection Technology for Steel Truss Suspension Bridges

Steel truss suspension bridges are prone to developing defects after prolonged use.These defects may include corrosion of the main cable or the steel truss.To ensure the normal and safe functioning of the suspension bridge,it is necessary to inspect for defects promptly,understand the cause of the defect,and locate it through the use of inspection technology.By promptly addressing defects,the suspension bridge’s safety can be ensured.The author has analyzed the common defects and causes of steel truss suspension bridges and proposed specific inspection technologies.This research is intended to aid in the timely discovery of steel truss suspension bridge defects.

Mechanic Analysis of the Key Node in Steel Truss Bridge

Steel truss bridges are frequently used in bridge engineering because of their good ability of spanning capacity, construction and light self-weight. Main trusses are the critical component of steel truss bridge and the main truss are made of truss members linked by integral joints. This paper presents the mechanic performance of key joints, and the codified design of joints in steel truss girders according to the latest European norms. The results showed that the fatigue resistance of welded joints evaluation is necessary to predict, detect, and repair the crack in time for the safety service life of the bridge. The stresses of integral joint are greater than that of truss members;the stresses in the center area of the integral joint are greater than the stress at the edge.

Experimental research on ultimate bearing capacity of N-joints of grouted square steel tube trusses

Cave-in failure is apt to occur in joints of trusses made of square hollow sections. In order to turn the failure mode into a strength failure mode of joint members, the idea is proposed that the chord of the truss is grouted to increase the cave-in beating capacity of a hollow tube chord. An experiment of eight specimens of N- joints made of grout-filled square steel tubes is performed. Based on the experimental study, the geometrical parameters of specimens are analyzed, and the effects of the confinement index ε, the spacing between the two web members g and the ratio of side length of the vertical web member to that of the chord β on the behavior of specimens are investigated through simulation analysis by simulation analyses, the mechanical properties and the failure an ANSYS program. Based on the test results and modes of this kind of joints are analyzed and the formulae to predict the ultimate bearing capacities corresponding to different failure modes are developed. The ultimate bearing capacity of compressive N-joints is calculated in accordance with the cave-in failure mode of a chord member; the ultimate bearing capacity of tension N-joints is calculated in accordance with the punchingshear failure mode; the ultimate bearing capacity of a chord member is calculated in accordance with the shear failure mode in normal sections.

Research on seismic performance of shear walls with concrete filled steel tube columns and concealed steel trusses

In order to further improve the seismic performance of RC shear walls, a new composite shear wall with concrete filled steel tube （CFT） columns and concealed steel trusses is proposed. This new shear wall is a double composite shear wall; the first composite being the use of three different force systems, CFT, steel truss and shear wall, and the second the use of two different materials, steel and concrete. Three 1/5 scaled experimental specimens： a traditional RC shear wall, a shear wall with CFT columns, and a shear wall with CFT columns and concealed steel trusses, were tested under cyclic loading and the seismic performance indices of the shear walls were comparatively analyzed. Based on the data from these experiments, a thorough elastic-plastic finite element analysis and parametric analysis of the new shear walls were carried out using ABAQUS software. The finite element results of deformation, stress distribution, and the evolution of cracks in each phase were compared with the experimental results and showed good agreement. A mechanical model was also established for calculating the load-carrying capacity of the new composite shear walls. The results show that this new type of shear wall has improved seismic performance over the other two types of shear wails tested.

Bending behaviour of lightweight aggregate concrete-filled steel tube spatial truss beam

A lightweight aggregate concrete-filled steel tube(LACFST) spatial truss beam was tested under bending load. The performance was studied by the analysis of the beam deflection and strains in its chords and webs. According to the test results, several assumptions were made to deduce the bearing capacity calculation method based on the force balance of the whole section. An optimal dimension relationship for the truss beam chords was proposed and verified by finite element analysis. Results show that the LACFST spatial truss beam failed after excessive deflection. The strain distribution agreed with Bernoulli-Euler theoretical prediction. The truss beam flexural bearing capacity calculation results matched test evidence with only a 3% difference between the two. Finite element analyses with different chord dimensions show that the ultimate bearing capacity increases as the chord dimensions increase when the chords have a diameter smaller than optimal one; otherwise, it remains almost unchanged as the chord dimensions increase.

Experimental research on mechanical properties of prestressed truss concrete composite beam encased with circular steel tube

Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of the tensile steel tube is 0.252 during the using stage,and the average crack space of beams depends on the ratio of the sum of the bottom chord steel tube's outside diameter and the secondary bottom chord steel tube's section area to the effective tensile concrete area. The coefficient of uneven crack distribution is 1.68 and the formula for the calculation of crack width is established. Test results indicate that the ultimate stress increment of unbonded tendon in the beams decreases in linearity with the increase of the composite reinforcement index β0. The pure bending region of beams accords with the plane section assumption from loading to failure. The calculation formula of ultimate stress increment of the unbonded tendon and the method to calculate the bearing capacity of normal section of beams have been presented. Besides,the method to calculate the stiffness of this sort of beams is brought forward as well.

Structural behaviors of steel roof truss exposed to pool fire

Experimental research was conducted to study the structural behaviors of a steel roof truss model without fire-proof coating under pool fire conditions. The data of temperature distribution and displacements of typical members were obtained. It is found that the temperature distribution of environment inside the structure, which is found to be in accordance with the multi-zone model with height, has a decisive effect on the tempera^tre evolution of steel members. Besides, it can also be observed that due to the restriction and coordination among the truss members in the localized fire, the maximum relative deflection, which occurs at the mid-span of the top chord, is relatively slight and has not exceeded 1 mm under experimental conditions. On the other hand, the column experiences a notable thermal expansion during the test. Then, a finite element model is presented and validated by the test results.

Experimental Study on Seismic Performance of Tall Building with Steel Transfer Trusses Located at a Higher Level

Based on a shaking table experiment of 1 :25 scale frame-shearwall structure model with steel transfer trusses,the dynamic characteristics,seismic responses in elastic and elastic-plastic phases with de- structive forms of the structure were studied.It was observed that cracks were developed with earthquake wave acceleration increasing,but no severe crack was developed in the structure during the experiment.In the seismic responses caused by artificial wave,site wave and E1 Centro wave,that caused by the artificial wave is the most intense one.Displacement angle between steel transfer trusses is large,which means the transfer stories might be weak.However,the seismic performance of the steel transfer trusses is good and the overall structure can satisfy seismic fortification requirements in the region of intensity 6.

Analysis on the Structural Type of Large-span Steel Truss Bridge Spe­cially Designed for Cables

When the installation of cables and pipelines needs to go across rivers,bridges are usually adopted to support the cables and pipelines for crossing the rivers.The measure can make full use of the space resources and have no effect on the flow pattern of rivers.For this reason,analysis on the structural-type design of a large-span steel truss bridge specially used for cables has been performed.The numerical results indicate that the stayed-cable bridge with steel truss beam and concrete main tower has better performance and improved structural type caparisoned with that of the beam and arch bridges,and the construction of the major beam can be without the temporary support.

高速铁路大跨度钢桁架桥接触网腕臂安装技术研究

高速铁路大跨度钢桁架桥纵向伸缩量大且变位复杂,是影响接触网腕臂偏移等系统能否正常、安全运行的重要因素,如何解决接触网腕臂安装、偏移调整与钢梁伸缩之间的协同配合,目前国内在此方面鲜有研究。通过阐述受导线伸缩影响的腕臂偏移机理和大跨度钢桁架桥梁体纵向伸缩机理,分析在不同接触网锚段布置方式下大跨度钢桁架桥梁体伸缩对腕臂偏移的影响,并采用逐工点分析法总结不同工况下钢梁伸缩与导线伸缩对腕臂偏移影响的相互关系,揭示了接触网腕臂安装曲线在导线伸缩及钢梁伸缩共同作用下的计算方法。结合典型案例计算分析,建议采用不同钢梁跨度下的推荐锚段布置方式能有效降低腕臂偏移量,并提出应重点关注伸缩缝两侧锚段腕臂偏移问题、腕臂偏移为叠加关系时缩小半锚长度、钢梁跨度大于720 m时应重点计算伸缩缝两侧双腕臂间距等优化事项。研究内容及计算公式可为系统性解决高速铁路大跨度钢桁架桥接触网腕臂偏移设计、施工及运营维护等技术难题提供理论支持。

大跨度钢桁架结构卸载模拟及监测技术研究

以江苏省盐城黄淮湿地博物馆钢桁架结构卸载施工为背景,旨在通过有限元技术及基于多传感器融合的现场监测技术研究大跨度桁架结构卸载施工关键技术。研究结果表明:有限元计算结果能够获取卸载施工过程中的关键要素,为后续监测方案的设计提供参考。后续的监测结果表明,有限元方法对位移的计算结果可靠性要高于应力,与实际情况更加接近;基于多传感器融合的监测方法能够提高监测结果的准确性和远程监控效果,为桁架结构的安全性和可靠性提供了有力支撑。研究结果可为大跨度钢结构建筑的施工提供参考。

大跨度钢桁梁桥智能建造技术应用的可行性研究

大跨度钢桁梁桥的构件制造及拼装复杂,采用场内预制组装仍需消耗大量的人力、财力及工期。因此,本文采用BIM桥梁建模、三维激光扫描和虚拟预拼装技术,进行了基于BIM技术的施工方案模拟的可行性研究和基于BIM技术与三维激光扫描方法结合的构件加工质量检测研究,并在此基础上进行了基于BIM技术与三维激光扫描方法结合的虚拟拼装技术研究,探索了大跨度钢桁梁桥智能建造技术应用于指导工程实施的可行性。

公铁合建斜拉桥钢桁-混凝土板组合梁受力特性

以某主跨808 m的公铁合建新型钢桁-混凝土板组合梁斜拉桥为背景,采用ANSYS软件建立局部组合梁细化的全桥多尺度有限元模型,分析其在不同工况下双层组合梁的受力传力特性和混凝土桥面板荷载分配比,并讨论混凝土桥面板厚度t_(b)、横梁刚度变化系数λ_(K)和钢与混凝土弹性模量比λ_(E)对组合梁受力传力的影响规律。结果表明:最不利组合工况下,钢桁架最不利Von Mises应力为183.6 MPa,混凝土桥面板最大拉应力为5.3 MPa,均满足结构受力要求;沿纵向路径,钢桁架和混凝土桥面应力在节间横梁间均呈“波形”分布;上下层混凝土桥面板顶、底面应力沿横向近似呈“W”和“M”状分布,表明桥面板承受一定沿横向不均匀分布弯矩;公路及铁路混凝土桥面最大剪力滞系数分别为1.45、1.36,更宽的公路混凝土桥面剪力滞效应更显著;公路及铁路混凝土桥面分别承担上、下层结构57.46%~79.99%和33.21%~62.81%的轴向荷载,为组合梁的主要传力构件;混凝土桥面板的应力随t_(b)及λ_(K)的增大而增大,随λ_(E)的增大而逐渐减小;混凝土桥面每层平均荷载分配比ξ与t_(b)成正比,与λ_(K)及λ_(E)成反比;当t_(b)、λ_(K)和λ_(E)参数的取值范围分别为0.8~1.4、0.4~1.6以及4~10时,组合梁混凝土桥面应力及荷载分配比ξ较为合理。

天津空客A330宽体机厂房焊接加固过程结构性能监测与分析

大跨度钢桁架加固方法多采用焊接加固增大截面法.针对大跨度钢桁架屋盖整体结构的负载焊接加固,以天津空客A321(A330宽体机厂房)屋盖为例,采用4片角钢,分肢与原H型钢的翼缘、腹板分别焊接的加固方式,设计了合理的焊接加固方案与监测方案,对结构关键构件在焊接加固过程中的应力、应变进行监测.以监测数据为依据,研究分析焊接加固过程中型钢与加固角钢的应力响应规律,验证钢桁架梁采用角钢焊接加固的传力有效性,判断焊接热输入的影响范围.结果表明:在负载焊接加固的过程中,局部高温热影响区引起应力重分布,加固角钢的存在对原有型钢构件起到了相应的承担作用,焊接加固过程中结构的安全性可以得到保证.此外,焊接加固时,通过监测相邻杆件的应力和应变,分析表明焊接热影响的范围在两个节间范围内,且带来的应力响应较小.

叠加空腹桁架的钢-钢骨混凝土组合转换桁架设计分析与监测

针对某上弦为钢骨构件、腹杆及下弦为型钢的钢-钢骨混凝土组合转换桁架结构,采用PKPM软件对组合转换桁架和其上空腹桁架进行了多个整体模型的弹性对比分析及静力推覆分析。结果表明,施工模拟方式、楼面板刚度模拟方式、混凝土空腹桁架构件徐变、中大震下出铰情况对转换桁架和空腹桁架分担的转换荷载计算值均有较大影响,相关因素应予包络、准确地考虑。对多个子结构组合而成的结构体系,应明晰各子结构在整体中发挥的作用,以及各子结构在相关因素变动情况下的定量变化情况,以保证各子结构性能稳定性和整体结构的安全。工程施工阶段监测表明,叠加空腹桁架的组合转换桁架结构变形及构件应变基本与设计预期相符,转换结构安全合理。

某在役铆接钢桁梁桥关键构件疲劳性能研究

精准评估现役钢桥的疲劳寿命对于桥梁结构的安全运营至关重要。该文以某在役铆接钢桁梁桥为研究对象,在对桥梁结构进行计算分析明确各构件的受力特点的基础上,针对原桥典型构件以及关键节点开展系列疲劳性能研究。数值计算结果表明,城B荷载作用下原桥典型构件以及关键节点均具有良好抗疲劳性能,疲劳寿命循环次数均大于200万次。

钢桁架在冲击荷载作用下的动态响应研究

圆钢管桁架在土木工程和海洋工程领域应用较多,除了承受竖向荷载外,还易遭受冲击偶然荷载作用。以偏心质量下抵抗冲击荷载的钢桁架为研究对象,利用LS-DYNA软件建立了节点冲击有限元模型。从破坏特征、冲击响应和耗能能力等方面研究了其抗冲击能力,对冲击次数、冲击速度和钢材屈服强度进行了参数分析,最后基于有限元模拟结果,提出了主管凹陷变形与转角之间的表达式。结果表明:经历多次摆锤冲击后,主管发生严重的凹陷变形,刚度显著降低;冲击速度达到3.0 m·s^(-1)时,冲击力峰值提高了84.8%,冲击区域支管节点发生挤压弯曲破坏,主管凹陷变形是主要的耗能机制。有限元模拟结果可为提高实际钢桁架的抗冲击性能提供参考。

阿里巴巴上海总部类巨型框架超限结构设计

阿里巴巴上海总部大厦采用了类巨型框架结构体系,主要结构构件均采用了钢结构。系统介绍了塔楼超限结构设计的概况,并针对本项目类巨型框架的结构特点和难点进行了阐述。针对塔楼整体结构的不规则性,提出了结构设计的抗震性能目标和抗震加强措施。结构的整体分析结果表明,结构整体指标和抗震性能均能满足既定的设计要求。对特殊及关键的结构部位进行了计算和分析,确保了构件和节点的可靠性及其在整体结构中关键作用。

大跨度公铁合建斜拉桥钢混板-桁组合梁关键节点空间受力特性

针对大跨度公铁合建斜拉桥—主跨808 m洪奇沥特大桥新型钢混板-桁组合梁的关键节点—辅助墩顶钢混节点,采用ANSYS软件建立钢桁-混凝土板组合梁部分节段细化的全桥多尺度有限元模型,分析边跨组合梁节点在受力最不利工况下的受力规律及传力特性,并讨论下弦杆等杆件截面等结构参数变化对节点受力、传力的影响规律。结果表明:最不利组合工况下,边跨组合梁辅助墩顶钢混节点处钢结构最不利Mises应力为265.9 MPa,混凝土局部最大名义拉应力为9.2 MPa,导致局部开裂而受力转移至钢结构;在辅助墩顶局部负弯矩影响下,内外节点板处应力总体呈“倒V”形分布,混凝土顶面及底面分别呈“鞍形”及“倒鞍”形分布;节点处下弦杆(含管内混凝土)、竖杆分别传递77.86%和40.15%荷载,为纵向、竖向主要传力构件;混凝土桥面厚度变化对自身应力影响明显,其厚度和下弦杆截面面积对纵向传力比影响大,竖杆截面面积对自身竖向传力影响相对明显;混凝土厚度及下弦杆、斜腹杆、竖杆截面为节点受力、传力的主要影响因素,其系数在0.8~1.1时,组合梁关键节点各构件应力及传力比均较为合理。