Spatial structural analysis of main saddle for single tower spatial cable self-anchored suspension bridge

Based on the engineering background of the Jiangxinzhou Bridge in Nanjing, issues related to the spatial main saddle of the self-anchored suspension bridge are studied. The refinement finite element model is established by the secondary development technology based on the platform of the general finite element program, and a reasonable load pattern is used in its spatial structural analysis, by which its path of force transference and stress distribution are obtained. Matched with the spatial main cable, the tangency point correction method is also discussed. The results show that the lateral wall stress of the saddle groove is higher than the stress within the wall due to the role of lateral forces in the finished bridge state; the horizontal volume force of the main cable can generate a gradient distributed vertical extrusion pressure on the saddle clamping device and the main saddle body; the geometric nonlinear effect of the self- anchored suspension bridge cable system in the construction process is significant, which can be reflected in the spatial tangent point position of the main cable with the main saddle changes a lot from free cable to finished cable.

Energy conservation research of dehumidification system for main cable anticorrosion of suspension bridge

The necessity of the main cable anticorrosion for suspension bridge is described, and operating principles and composition of main cable dehumidification system are analyzed. An idea using the waste heat of high temperature outlet air of dehumidification system to heat up regeneration air of rotary-type dehumidifier is put forward in this paper. The concrete scheme is to install a heat exchanger on air-out pipeline of roots blower and air-in pipeline of regeneration electric heater of rotary dehumidifier. Air preheated by the heat exchanger enters regeneration electric heater of rotary-type dehumidifier. Energy conservation of main cable dehumidification system for the Yangtze River highway bridge is calculated, and the results show that energy conservation rate can reach 44 %.

Cable flexural rigidity influence on suspension bridges static properties

In order to figure out the cable flexural rigidity influence on suspension bridges,a contrast model experiment is made:a chain cable model with no flexural rigidity and a wire cable model with some flexural rigidity.And then,four finite element models of a same long-span suspension bridge with different cable element are set up to be analyzed.Both experimental and numerical simulation results show that,with the increase of the span and the decrease of sag-span ratio,the influence of the cable flexural rigidity is significant.The difference of nodes displacement reaches more than 10 cm in construction analysis,which will bring some trouble to the construction.And the difference of the maximum section edge normal stress may reach 15%,which may have an adverse impact onto the bridge.Therefore,considering the cable flexural rigidity is necessary on some analysis of suspension bridges.

Parameters of static response of carbon fiber reinforced polymer(CFRP) suspension cables

The feasibility of longer spans relies on the successful implementation of new high-strength light weight materials such as carbon fiber reinforced polymer(CFRP). First, a dimensionless equilibrium equation and the corresponding compatibility equation are established to develop the cable force equation and cable displacement governing equation for suspension cables, respectively. Subsequently, the inextensible cable case is introduced. The formula of the Irvine parameter is considered and its physical interpretation as well as its relationship with the chord gravity stiffness is presented. The influences on the increment of cable force and displacement by λ2 and load ratio p′ are analyzed, respectively. Based on these assumptions and the analytical formulations, a 2000 m span suspension cable is utilized as an example to verify the proposed formulation and the responses of the relative increment of cable force and cable displacement under symmetrical and asymmetrical loads are studied and presented. In each case, the deflections resulting from elastic elongation or solely due to geometrical displacement are analyzed for the lower elastic modulus CFRP. Finally, in comparison with steel cables, the influences on the cable force equation and the governing displacement equation by span and rise span ratio are analyzed. Moreover, the influences on the static performance of suspension bridge by span and sag ratios are also analyzed. The substantive characteristics of the static performance of super span CFRP suspension bridges are clarified and the superiority and the characteristics of CFRP cable structure are demonstrated analytically.

Study for reasonable value of friction coefficient between main cable and saddle

The value of friction coefficient between the main cable and saddle, relates to not only the anti-slippage stability of three-tower suspension bridge, but also the reasonable stiffness of the middle tower and the magnitude of rigidity of the whole bridge. First, the paper does some comparative studies about the relevant provisions of international norms, and then, summarizes the relevant load test results both at home and abroad. Finally, the paper draws the appropriate anti-slippage safety factor for the most unfavorable load in accordance with international load standards, and discusses the rationality and feasibility of the friction coefficient of 0.2 between main cable and saddle.

Optimization of Dead Load State in Earth-Anchored Cable-Stayed Bridges

In order to determine the reasonable completed dead load state in earth-anchored cable-stayed bridges,a practical method is proposed. The method is based on the rigidly supported continuous beam method and the feasible zone method,emphasizing on the mutual effect between the self-anchored structural parts and the earth-anchored ones. Three cable-stayed bridge models are designed with the main spans of 1 400 m,including a partially earth-anchored cable-stayed bridge,a cable-stayed-suspension bridge and a fully selfanchored cable-stayed bridge,in which the C50 concrete and Q345 steel are adopted. The partially earthanchored cable-stayed bridge and the cable-stayed-suspension bridge secure lower compressive force in the girder than the fully self-anchored cable-stayed bridge by 25 percent at least. The same is for the material consumption of the whole bridge. Furthermore,the anchor volume is more than 20% lower in the partially earthanchored cable-stayed bridge than that in the cable-stayed-suspension bridge. Consequently,the practical span of cable-stayed bridges can be accordingly extended.

Dynamic Analysis of Suspension Bridges and Full Scale Testing

This paper is concerned with the earthquake analysis of suspension bridges, in which the effects of large deflections are taken into account. The first part of the study deals with an iteration scheme for the nonlinear static analysis of suspension bridges by means of tangent stiffness matrices. The concept of tangent stiffness matrix is then introduced in the frequency equation governing the free vibration of the system. At any equilibrium stage, the vibrations are assumed to take place tangent to the curve representing the force-deflection characteristics of the structure. The bridge is idealized as a three dimensional lumped mass system and subjected to three orthogonal components of earthquake ground motion producing horizontal, vertical and torsional oscillations. By this means a realistic appraisal is achieved for torsional response as well as for the other types of vibration. The modal response spectrum technique is applied to evaluate the seismic loading for the combination of these vibrations. Various numerical examples are introduced in order to demonstrate the method of analysis. The procedure described enables the designer to evaluate the nonlinear dynamic response of suspension bridges in a systematic manner.

Stability Study of Cable-Suspended Stewart Platform

The control stability of the end manipulator of a cable-suspended Stewart platform in disturbance was studied by combination of the multi-body system dynamics and control theory and the eigensystem realization algorithm （ERA）. The corresponding closodloop vibration control strategies were suggested based on position prediction with PD （proportional plus derivative ） control. Numerical simulation was made on a scale model to study the vibration control effects of the stewart platform with flexible suspension, including system response to step load, system response to cyclic load, and instability. Then, experiments for Stewart platform with cable suspension were designed to study the actual control effects and validate the validity of numerical simulation. The results show that the experimental results agree with the simulation results well, and the the system has a fairly good control effect to the end manipulator. Therefore, a preliminary conclusion can be made that it is feasible using the Stewart platform as the vibration control platform of the flexible support system, by position prediction of the base platform and PD feedback control law.

Advanced aerostatic analysis of long-span suspension bridges

As the span length of suspension bridges increases, the diameter of cables and thus the wind load acting on them, the nonlinear wind-structure interaction and the wind speed spatial non-uniformity all increase consequently, which may have unnegligible influence on the aerostatic behavior of long-span suspension bridges. In this work, a method of advanced aerostatic analysis is presented firstly by considering the geometric nonlinearity, the nonlinear wind-structures and wind speed spatial non-uniformity. By taking the Runyang Bridge over the Yangtze River as example, effects of the nonlinear wind-structttre interaction, wind speed spatial non-uniformity, and the cable＇s wind load on the aerostatic behavior of the bridge are investigated analytically. The results showed that these factors all have important influence on the aerostatic behavior, and should be considered in the aerostatic analysis of long and particularly super long-span suspension bridges.

Space shape finding FE analysis for suspension bridge based on CR formulation method

The problem of geometric non-linearity simulation for spacial cable system was solved by introducing the truss element based on corotational coordinate (CR) system, cable structure materials and node coordinates and automatic refreshing algorithms for element internal force. And the shape-finding problem for maneuvering profile was solved with the Newton-Raphson based on energy convergence criteria with search function. This has avoided the regular truss element assumption extensively used in traditional methods and catenary elements which have difficulties in practical application because of the complicated formulas. The use of CR formulation has taken into account the stiffness outside the cable plane via a geometric stiffness matrix, realizing the 3D space analysis of a cable bridge and improving the efficiency and precision for the space geometric non-linearity analysis and cable structure, and enabling more precised simulation of geometric form finding and internal force of the large span suspension bridge main cable under construction.

Research on the stiffening girder erection sequence of three-tower suspension bridge

Compared to the conventional two-tower suspension bridge, the three-tower suspension bridge has obviously different characteristics in structural performance because of the extra middle tower and main span. The construction sequence for the stiffening girder is significantly different between the three-tower suspension bridge and the two-tower suspension bridge. The tangential angle of the main cable is one of the controlling factors of the stiffening girder erection stage for a suspension bridge. According to 5 feasible cases for the stiffening girder erection scheme in Taizhou Bridge, the research about the tangential angle in each case mentioned above was made, and some factors that should be taken into account for the erection scheme of stiffening girder were pointed out.

Calculation method on shape finding of self-anchored suspension bridge with spatial cables

Based on the spatial model,a reliable and accurate calculation method on the shape finding of self anchored suspension bridge with spatial cables was studiedin this paper.On the principle that the shape of the main cables between hangers is catenary,the iteration method of calculating the shapes of the spatial main cables under the load of hanger forces was deduced.The reasonable position of the saddle was determined according to the shape and the theoretical joint point of the main cables.The shapes of the main cables at completed cable stage werecalculated based on the unchanging principle of the zero-stress lengths of the main cables.By using a numerical method combining with the finite element method,one self-anchored suspension bridge with spatial cables was analyzed.The zero-stress length of the main cables,the position of the saddle,and the pre-offsetting of the saddle of the self-anchored suspension bridge were given.The reasonable shapes of the main cables at bridge completion stage and completed cable stage were presented.The results show that the shape-finding calculation method is effective and reliable.

四主缆大跨悬索桥抗震性能分析及减震措施优化

以燕矶长江大桥为工程背景,首先,采用动力非线性时程法分析了燕矶长江大桥抗震性能,并研究了设置电涡流-摩擦组合型阻尼器和黏滞阻尼器对大跨悬索桥抗震性能的影响;然后,对附加电涡流-摩擦组合型阻尼器摩擦力、阻尼系数和阻尼指数开展了参数敏感性分析;最后,从耗能角度分析地震作用下电涡流-摩擦组合型阻尼器减震特点.结果表明:在E2地震作用下,桥塔关键截面抗弯能力均大于弯矩需求;在“纵向+竖向”地震作用下梁端纵向位移较大.设置塔梁处纵桥向阻尼器后,可有效降低主桥梁端纵向位移;增大摩擦力、阻尼系数与降低阻尼指数均可提升梁端纵向地震响应的控制效果,但参数变化对桥塔控制截面的地震响应影响较小.阻尼系数较大时,电涡流阻尼主导了电涡流-摩擦组合型阻尼器耗能,相较于黏滞阻尼器,电涡流-摩擦组合型阻尼器对梁端纵向位移控制效果更好.

超长大跨度公铁合建桥梁结构体系研究

新建甬舟铁路西堠门公铁两用大桥连接金塘岛和册子岛,桥位处海域宽2.7 km,最大水深93 m,地形复杂,桥梁设计难度大。为研究超长大跨度公铁合建桥梁合理结构体系,结合地形地质条件,选取主跨1500 m悬索桥、斜拉桥及斜拉悬索协作体系3种桥型方案,对上部结构设计进行详细介绍,并从静力性能、动力性能、经济性能等方面对不同结构体系进行对比分析。研究表明:(1)与斜拉体系相比,协作体系桥可减小30%~50%的主梁内力和60%的桥塔内力,一定程度上解决了加劲梁承受巨大轴压力造成屈曲问题,并有效减小了桥塔规模;(2)与悬索桥相比,协作体系可减小50%的主缆内力,主缆钢丝和锚碇的工程量相应减小,施工难度得以降低,同时协作体系扭转频率更高,降低了结构在较低风速下发生涡激振动的可能性;(3)斜拉悬索协作体系能够充分发挥斜拉结构和悬索结构的组合优势,实现超大跨度的同时具有较大的纵向刚度和竖向刚度,满足铁路行车对结构刚度的要求;(4)对于主跨1500 m级超长大跨度公铁合建桥梁,斜拉悬索协作体系经济性更好。

斜拉桥长大节段组合式主梁悬臂施工技术研究

鲁巴跨海大桥主航道桥为双塔双索面混凝土斜拉桥,大桥主梁为π形混凝土组合式主梁,标准节段长10.2m、宽17.3m、中心高2.5m;主梁斜拉索锚固块及横向横梁为预制装配式构件,边主梁及桥面板为现浇混凝土构件,各主要构件通过横向预应力连为一体。以该桥主梁悬臂施工为工程背景,从质量控制、施工计划、施工成本3个方面对主梁2种施工方案进行对比,最终确定适合本桥主梁施工的挂篮方案,可有效降低临时结构自重对已浇筑节段混凝土产生的附加应力影响,降低工程造价;同时,通过对2~15号主梁节段采用新型桁架式牵索挂篮施工进行专项设计,解决了主梁节段长、自重大、预制装配式构件安装精度要求高、节段施工周期长的难题。

我国建筑索结构的发展与工程实践

索结构已经成为现代大跨度建筑结构的首选体系之一。梳理了七十年以来我国索结构的发展历程,将其分为起步、缓慢发展和快速发展三个阶段,并对每个阶段进行了详细分类和阐述。对建筑索结构中的拉索构件和节点构件进行了归纳和总结,系统地列举了各类构件的主要形式。此外,综述了悬索结构、索膜结构、张弦(弦支)结构及索穹顶结构等典型结构形式的特点、受力机理及代表性工程,进一步展示了索结构在实际工程中的广泛应用和显著优势。这些结构形式不仅体现了索结构的创新性和灵活性,也证明了其在满足大跨度建筑需求方面的卓越性能。在可持续绿色发展的要求下,随着科技的不断进步,索结构在建筑领域的应用前景愈发广阔。我国的索结构将继续在大跨度建筑领域中扮演重要角色,为实现更加高效、环保和创新的建筑设计提供有力支持。

基于工程经济性的公路悬索桥主缆最优垂跨比研究

为寻求工程经济性最优的公路悬索桥主缆垂跨比,以我国近年多座采用混凝土桥塔的单跨公路悬索桥为背景,建立主缆、锚碇、桥塔基础工程量的直接函数模型和桥塔塔身工程量的非线性函数拟合模型,对跨度750~2250 m、单层车道数4~8及双层车道数6+4、垂跨比1/14~1/6共952种布置形式的悬索桥进行大范围关于主缆垂跨比的工程经济性研究,并以2座实桥为算例分析主缆垂跨比对悬索桥静、动力性能及抗风性能的影响。结果表明:主缆垂跨比对悬索桥工程经济性影响显著;悬索桥主缆最优垂跨比与跨度相关,而车道数、加劲梁荷载集度的影响相对较小,涉水和不涉水的差异也不显著;基于工程经济性考虑,跨度750~2250 m的悬索桥主缆最优垂跨比为1/6.5~1/8.5,比经验值增大较多。2座实桥算例分析表明随着垂跨比增加,加劲梁挠度和活载应力有所增加,抗风性能略有提升,建议方案设计阶段加大垂跨比研究范围、对工程经济性和桥梁力学性能进行综合比选。

复合空间索对大跨度铁路悬索桥横向刚度影响的研究

为提升大跨度铁路悬索桥的横向刚度,提出一种由主、副斜拉索组成的复合空间索结构。然后,基于材料有效利用率和静力分析,对复合空间索的直径、主斜拉索在加劲梁和地表的锚点位置、副斜拉索的数量等参数进行了优化。最后,采用风-车-桥耦合振动分析法,基于行车性能得到了桥梁横向挠跨比限值,分析了主、副斜拉索对横向挠跨比限值提升率的影响。结果表明:基于材料有效利用率,主斜拉索与加劲梁的锚点位置宜设在1/4主跨附近,且主斜拉索的地表锚点、加劲梁锚点与桥塔的垂直距离相等时最优,每组复合空间索中副斜拉索设置1根即可;在复合空间索的最优布置形式下,桥梁横向挠跨比可降低14.18%,横向挠跨比限值可提升16.79%。

G3铜陵长江公铁大桥桥塔基础设计

G3铜陵长江公铁大桥主桥为主跨988 m的斜拉-悬索协作体系桥,桥塔采用钢筋混凝土门形结构。3号桥塔基础比选了钻孔桩基础与沉井基础方案,4号桥塔基础比选了钻孔桩基础与地下连续墙基础方案,综合考虑基础受力性能、经济性、施工风险等,均推荐采用钻孔桩基础方案。3号、4号桥塔塔座高4.5 m,承台分别为厚7 m的圆形-哑铃形和矩形-哑铃形结构,基础分别采用68根和64根φ3.0 m钻孔桩,桩长分别为95 m和79 m,按摩擦桩设计。承台系梁采用ANSYS软件进行实体有限元分析,系梁横向受力主筋、竖向抗剪箍筋采用优化分区配置,满足受力要求。

AS法悬索桥锚靴及拉杆锚固可靠性研究

AS法(空中纺线法)施工的悬索桥,主缆各索股钢丝套接锚固在两岸的锚靴上,锚靴通过拉杆将索股力传递给锚固系统。锚靴与主缆钢丝相互作用后锚靴的承载能力、钢丝小曲率弯折后的应力状态、拉杆安装精度对锚固可靠性的影响均需要定性定量的研究以及试验验证。该文以AS法架设主缆悬索桥——阳宝山特大桥为背景,对锚靴及索股进行了6 150 kN设计荷载下拉杆无偏转状态、拉杆相对于锚固垫板在水平向、竖直向和45°向偏转0.5°共4种工况下的试验研究。结果表明:锚靴承载能力满足设计要求,钢丝小曲率弯折后无异常变形和破坏;锚靴及拉杆构造连接可靠,装配性好,构造采用球面垫圈结构可以保证拉杆具备约1°偏心调节能力,为保证锚靴及拉杆构造设计使用要求,建议拉杆与索股轴向安装控制精度保证在0.5°以内。