Characteristics Comparison and Case Study of Traditional Anti-Slip Saddles and Innovative Rolling Saddles in Highway Long-Span Bridges
公路大跨度桥梁传统防滑鞍与创新滚动鞍的特性比较及案例分析

Abstract 抽象

The cable saddle structure is the main support component for long-span bridges to transmit cable force, which is of great significance for the structural force system. Nowadays, the main cable saddle structures used in long-span bridges are mainly traditional anti-slip saddles and innovative rolling saddles. To clarify the characteristics of the saddles in long-span bridges, the design principles, mechanical properties, and casting process of these two types of saddle structures were researched. A rolling saddle in a bridge project was taken as an example and its mechanical situation in the roller area was investigated. The results showed that the stress concentration phenomenon is prone to occurring in the rolling saddle because of the line contact in the contact area and the rolling saddle is mainly subjected to vertical force. Thus, attention should be paid to the von Mises stress in the contact area between the saddle base and the roller shaft, the lower surfaces of both ends of the roller shaft, and the top surface of the tower, to avoid material damage. Furthermore, the casting process of the anti-slip saddle structure is mature, but also faced with problems due to the welding of thick plates, and urgently needs to be improved and upgraded. The rolling saddle is used with the all-welded casting process, but its technology is relatively immature and the requirements for the roller shaft material performance are strict. The research results can provide a reference for the selection and design of the saddle structure in long-span bridges.
索鞍结构是大跨度桥梁传递索力的主要支撑构件，对结构力系统具有重要意义。如今，大跨度桥梁采用的主要索鞍结构主要是传统的防滑鞍座和创新的滚动鞍座。为明确大跨度桥梁鞍座的特点，研究了两类鞍座结构的设计原理、力学性能和铸造工艺。以某桥梁工程中的滚动鞍座为例，研究了其在滚轮区域的机械情况。结果表明：由于接触区存在线接触，滚动鞍座容易发生应力集中现象，滚动鞍座主要受垂直力作用;因此，应注意鞍座与滚子轴接触区域、滚子轴两端下表面和塔顶表面的冯·米塞斯应力，以免造成材料损坏。此外，防滑鞍座结构的铸造工艺已经成熟，但也面临着厚板焊接带来的问题，亟待改进和升级。滚动鞍座采用全焊接铸造工艺，但其技术相对不成熟，对滚子轴材料性能要求严格。研究结果可为大跨度桥梁鞍座结构的选择和设计提供参考。

1. Introduction 1. 引言

Large-span bridges have been widely adopted because of their great crossing ability [1,2,3]. The saddle structure is an important part of a large-span suspension bridge as it helps to realize the large span and crossing function [4,5]. It is used as the main support component for the suspension cable or diagonal cable to pass through the top of the tower and transfer the cable force. It plays an important role in reasonably reducing the maximum bending moment at the bottom of the tower, effectively adjusting the load-carrying capacity of the tower and the scale of the foundation, as well as equalizing the cable force of the main cable [6]. At present, the main saddle structure used in large-span bridges can be divided into an anti-slip saddle and a rolling saddle. The anti-slip saddle is generally set up as an anti-slip device in the saddle balance system, to avoid the slip phenomenon in a suspension cable or cable-stayed cable during the bridge operation process [7]. The rolling saddle is optimized and designed based on the anti-slip saddle structure. A row of rollers is set below the saddle base, which changes the original form of friction from sliding friction to rolling friction, and leads to the automatic equalization of the cable system [8].
大跨度桥梁因其强大的穿越能力而被广泛采用[1,2,3]。鞍座结构是大跨度悬索桥的重要组成部分，有助于实现大跨度和交叉功能[4,5]。它用作悬索或斜索穿过塔顶并传递索力的主要支撑部件。它在合理降低塔底最大弯矩，有效调节塔架承载能力和基础规模，均衡主索的索力方面起着重要作用[6]。目前，大跨度桥梁采用的主要鞍座结构可分为防滑鞍座和滚动鞍座。防滑鞍座一般设置在鞍座平衡系统中作为防滑装置，以避免悬索或斜拉索在桥梁作业过程中出现滑移现象[7]。滚动鞍座基于防滑鞍座结构进行优化设计。鞍座底座下方设置了一排滚轮，将原来的摩擦形式从滑动摩擦变为滚动摩擦，导致电缆系统的自动均衡[8]。

To date, many researchers have carried out several in-depth studies and research on the anti-slip function of the cable saddle [9,10,11,12]. Ye et al. [13] proposed a combination of horizontal and vertical friction plates in the saddle groove and investigated the anti-slip problem between the saddle and the main cable in the main tower saddle of the Wenzhou Oujiang Beikou Bridge in China. Chang et al. [14] set polytetrafluoroethylene (PTFE) slip plates on the lower part of the tower saddle body on both sides of the Jinan Phoenix Yellow River Bridge and the top fixed joint of the cable tower to reduce the top thrust friction resistance. They were also lubricated to adapt to the relative positional difference generated in the construction process. In the test study of the friction coefficient between the main cable and the cable saddle, the field bridge test values of the friction coefficient of the George Washington and Forth Road bridges in America are 0.3 [15]. The test result of the Delaware River bridge is between 0.19 and 0.21. The test value of the Kanmon bridge in Japan is between 0.15 and 0.21. The test value of the Honshu–Shikoku bridge is between 0.16 and 0.44 [16]. Researchers at Southwest Jiaotong University tested the friction coefficients between different numbers of strand bundles and test saddles through model tests, and the friction coefficients of ordinary saddles and those setting vertical friction plates were found to be 0.473 and 0.552, respectively [17].
迄今为止，许多研究人员对电缆鞍座的防滑功能进行了多次深入的研究和研究[9,10,11,12]。Ye等[ 13]提出了鞍槽中水平和垂直摩擦板的组合，研究了温州瓯江北口大桥主塔鞍座与主索之间的防滑问题。Chang等[ 14]在济南凤凰黄河大桥两侧塔鞍体下部和电缆塔顶部固定接头处设置聚四氟乙烯（PTFE）滑板，以降低顶部推力摩擦阻力。它们还经过润滑，以适应施工过程中产生的相对位置差。在主索与索鞍摩擦系数试验研究中，美国乔治华盛顿桥和福斯路桥摩擦系数的场桥试验值为0.3[15]。特拉华河大桥的测试结果在0.19和0.21之间。日本关门桥的测试值在0.15到0.21之间。本州四国大桥的试验值在0.16-0.44之间[16]。西南交通大学的研究人员通过模型测试测试了不同数量的股束和测试鞍座之间的摩擦系数，发现普通鞍座和设置垂直摩擦板的摩擦系数分别为0.473和0.552[17]。

For research into a new rolling saddle, Teng et al. [18] analyzed its internal force in Wanxin Bridge, and the results showed that the wall thickness of the saddle should not be too large, and especially the radius of the inner tangent circle of the saddle groove part should not be too large. In the outdoor test simulation of the main bridge of the Jinshajiang River Bridge over Tiger Leaping Valley, it is confirmed that in the case of unbalanced cable force, the saddle can be rolled using the roller shaft to achieve the adjustment of the two ends of the cable force [19]. The cable force system tends to be balanced through the bias load test of the saddle structure. To ensure the anti-slip safety of the main cable in the main saddle of a long-span suspension bridge, contact and slip behaviors of the main cable of a long-span suspension bridge were investigated [20].
针对新型滚动鞍座的研究，Teng等[18]分析了万新桥的内力，结果表明鞍座壁厚不宜过大，尤其是鞍槽部分内切圆半径不宜过大。在虎跳谷金沙江大桥主桥户外试验模拟中证实，在索力不平衡的情况下，鞍座可利用滚轮轴滚动，实现索力两端的调整[19]。通过鞍座结构的偏置载荷试验，拉索受力系统趋于平衡。为保证大跨度悬索桥主鞍主索的防滑安全性，研究了大跨度悬索桥主索的接触和滑移行为[20]。

From the above research, it can be seen that there are differences between the slip-resistant saddle structure and rolling saddle structure in many aspects, which has an important impact on the structural force system and service performance of large-span bridges. In order to clarify the characteristics of different saddle structures for long-span bridges, this paper analyzes the anti-slip saddle from the three aspects of design principles, mechanical characteristics, and the casting process, so as to provide references for the selection and design of saddle structures for highway long-span bridges.
从以上研究可以看出，防滑鞍座结构与滚动鞍座结构在许多方面存在差异，这对大跨度桥梁的结构受力体系和服务性能具有重要影响。为明确大跨度桥梁不同桥座结构的特点，本文从设计原理、力学特性、铸造工艺三个方面对防滑桥座进行了分析，以期为公路大跨度桥梁鞍座结构的选择和设计提供参考。

2. Design Principles 2. 设计原则

2.1. Anti-Slip Saddle 2.1. 防滑鞍座

Taking a large-span main bridge anti-slip cable saddle as an example, the saddle adopts a cast-welded structure, the center tower saddle is directly connected to the top of the tower, and the PTFE anti-slip plate is set under the tower saddle body, as shown in Figure 1.
以大跨度主桥防滑索鞍为例，鞍座采用铸焊结构，中心塔鞍直接与塔顶连接，塔鞍体下方设置聚四氟乙烯防滑板，如图1所示。

Figure 1. Structural design sketch of an anti-slip saddle in the center tower of a bridge.
图 1.桥梁中心塔防滑鞍座的结构设计草图。

For the anti-slip device in the anti-slip saddle, three technical solutions are proposed in the design of this bridge. Among them, the radial direction of the horizontal friction plate can freely transfer the pressure and constrain it along the bridge. The shear pin transfers the friction between the main cable strand and the friction plate directly to the side wall of the saddle groove, while the force between the lower part of the saddle groove and the side wall is the same as that of the ordinary cable saddle. The lateral friction force of the strand can also be used to improve the anti-slip characteristics of the saddle by replacing the ordinary spacer of the saddle with a vertical friction plate. As the height of the strand increases, the friction created by the lateral pressure on the sidewalls of the saddle groove rises gradually, which can be used to minimize the slipping phenomenon of the strand. In the above two cases, the horizontal friction plate can easily cause the strand to generate a stratified slip phenomenon. Thus, the vertical friction plate can be added on the basis of the original horizontal friction plate. The space for setting up the friction plate can be obtained by varying the vertical and lateral positions of the strand, so as to improve the anti-slip performance of the saddle.
针对防滑鞍座中的防滑装置，在该桥的设计中提出了三种技术方案。其中，水平摩擦片的径向方向可以自由传递压力并沿桥板进行约束。剪切销将主索股与摩擦片之间的摩擦直接传递到鞍槽的侧壁，而鞍槽下部与侧壁之间的力与普通电缆鞍座的力相同。钢绞线的侧向摩擦力也可用于提高鞍座的防滑特性，方法是用垂直摩擦片代替鞍座的普通垫片。随着钢绞线高度的增加，鞍形槽侧壁上的侧向压力产生的摩擦力逐渐增加，可用于最大限度地减少钢绞线的打滑现象。在上述两种情况下，水平摩擦片很容易导致股产生分层滑移现象。因此，可以在原有水平摩擦片的基础上增加垂直摩擦片。通过改变股线的垂直和横向位置，可以获得设置摩擦片的空间，从而提高鞍座的防滑性能。

2.2. Rolling Saddle 2.2. 滚动鞍座

Examples of the application of rolling saddles in China are mainly found in the Dongming Yellow River Bridge Rehabilitation Project. As the core technology of the new steel wire cable suspension system in this project, the architectural design of the rolling saddle must comply with the following conditions: (1) Safe and reliable overall structural design; (2) The rollers of the saddle must have good mechanical properties, including smaller friction and larger surface hardness.
滚鞍在我国的应用实例主要见于东明黄河大桥修复工程。作为本项目新型钢丝缆悬索系统的核心技术，滚动鞍座的建筑设计必须符合以下条件：（1）整体结构设计安全可靠;（2）鞍座的滚子必须具有良好的机械性能，包括摩擦力较小，表面硬度较大。

A rolling saddle is mainly composed of a saddle cover, the saddle body, a roller shaft assembly, a saddle bottom plate, a cable, and other basic structures, as shown in Figure 2. Its sliding part is composed of the lower and upper planes of the saddle body, a sliding plate, and the roller shaft assembly. The axial pressure of the cable is transmitted to the base of the saddle through the base plate of the saddle, which mainly consists of the base plate, limit plate, and a block at both ends. The limit plate and block are used to control the sliding of the rolling saddle in the direction of the bridge and realize the automatic equalization of the cable force. However, because of the installation of roller components, rolling failure and other problems are prone to occur, resulting in the insufficient stability of structural performance.
滚动鞍座主要由鞍座罩、鞍座体、滚轮轴总成、鞍座底板、电缆等基本结构组成，如图2所示。其滑动部分由鞍体的上下平面、滑板和滚子轴总成组成。电缆的轴向压力通过鞍座的底板传递到鞍座的底座，鞍座的底板主要由底板、限位板和两端的块组成。限位板和块用于控制滚动鞍座在桥梁方向上的滑动，实现索力的自动均衡。但是，由于辊子部件的安装，容易发生轧制失效等问题，导致结构性能稳定性不足。

Figure 2. Structural design of a rolling saddle in the center tower of a bridge.
图2.桥梁中心塔中滚动鞍座的结构设计。

3. Mechanical Characteristics
3. 机械特性

3.1. Anti-Slip Saddle 3.1. 防滑鞍座

The cable saddle transmits the cable force at the tower. Due to the curved shape, the saddle is subjected to contact stresses from the cable and transmitted to the tower. The inside of the saddle groove is also subjected to friction in contact with the cable, as shown in Figure 3. Gradually, the unbalanced horizontal force at the top of the tower increases, material loss and structural wear inside the saddle occurs, and the tie rope slips. The cable saddle is not rigidly connected to the cable tower, but is lubricated by a PTFE slip sheet to accommodate the slip phenomenon. A face contact is formed between the saddle and the top of the towers, and there is no significant stress concentration in the contact zone.
电缆鞍座在塔架上传递电缆力。由于弯曲的形状，鞍座受到来自电缆的接触应力并传递到塔架。鞍槽内部在与电缆接触时也会受到摩擦，如图 3 所示。渐渐地，塔顶的不平衡水平力增加，鞍座内部发生材料损失和结构磨损，拉绳打滑。电缆鞍座没有刚性地连接到电缆塔上，而是通过PTFE滑片润滑，以适应滑移现象。鞍座与塔顶之间形成面接触，接触区没有明显的应力集中。

Figure 3. Schematic diagram of main cable axial force transfer in an anti-slip saddle.
图3.防滑鞍座中主缆轴向力传递示意图。

3.2. Rolling Saddle 3.2. 滚动鞍座

Unlike an anti-slip saddle, a rolling saddle is in contact with the top of the towers through roller shafts, as shown in Figure 4. The contact pressure between the saddle and the main cable is transferred to the bottom of the saddle and to the top of the tower via the roller shaft. The friction between the roller shaft and the bottom of the saddle and the top of the tower is rolling friction. Thus, the saddle only provides vertical forces, and the adverse effects due to the rise and fall in the overall temperature can be eliminated by lateral rolling. The roller shaft and the upper and lower plates form a line contact, and there is a significant stress concentration in the contact area, which results in a relatively large structural deformation and material yielding.
与防滑鞍座不同，滚动鞍座通过滚轮轴与塔顶接触，如图 4 所示。鞍座和主电缆之间的接触压力通过滚子轴传递到鞍座底部和塔架顶部。滚子轴与鞍座底部与塔顶之间的摩擦是滚动摩擦。因此，鞍座仅提供垂直力，并且可以通过横向滚动来消除由于整体温度的上升和下降而产生的不利影响。滚子轴与上下板形成直线接触，接触区应力集中明显，导致结构变形和材料屈服较大。

Figure 4. Schematic diagram of contact force on a roller shaft.
图4.滚子轴上的接触力示意图。

It can be seen that with the increase of the unbalanced force of the cable saddle, especially in high-tower suspension bridges, the bending moment in the tower body and bottom will consequently increase, which would further jeopardize the safety of the bridge. The rolling saddle, as a self-balancing system, adopts a smaller friction coefficient of the multi-row rollers and changes the original sliding friction into rolling friction. Thus, the self-balancing in the two sides of the main cable horizontal force and saddle rolling friction force can be achieved even under the temperature, vehicle load, and other common load. It can prolong the service life of the saddle and maintain the stability of the cable-stayed tower. However, the stresses in the upper and lower contact areas of the roller shaft are more concentrated, which makes it prone to problems such as roller shaft failure and reduces the stability of the self-balancing system structure.
可以看出，随着索鞍不平衡力的增加，特别是在高塔悬索桥中，塔体和底部的弯矩会随之增加，这将进一步危及桥梁的安全。滚动鞍座作为一种自平衡系统，采用多排滚轮的摩擦系数较小，将原来的滑动摩擦力转变为滚动摩擦力。因此，即使在温度、车辆载荷等共同载荷下，也能实现主缆两侧水平力和鞍座滚动摩擦力的自平衡。它可以延长鞍座的使用寿命，保持斜拉塔的稳定性。但滚子轴上下接触区的应力较为集中，容易出现滚子轴故障等问题，降低了自平衡系统结构的稳定性。

4. Casting Process 4.铸造工艺

4.1. Anti-Slip Saddle 4.1. 防滑鞍座

A saddle is characterized by its complex structure, large volume, and heavy weight. The most common types can be divided into cast and welded, all-cast, all-welded and combined saddles [21,22,23]. A large saddle often utilizes a cast and welded structure design. It fully absorbs the advantages of all-cast and all-welded saddles. It has many engineering examples and its process is relatively mature. As a large structural device, the upper part of a cast and welded saddle often uses steel casting. The lower part often uses a number of thick welding steel plates. The number of welds is larger, which also causes welding difficulties in the main saddle. The main difficulties are as follows: (1) the saddle head and seat steel plate after welding is prone to producing cold cracks; (2) small casting spacing is prone to welding operation difficulties; (3) thick plate welding causes increases structural rigidity and the stress concentration phenomenon, and laminar tearing is more likely after welding.
鞍座的特点是结构复杂、体积大、重量重。最常见的类型可分为铸造和焊接、全铸、全焊接和组合鞍座[21,22,23]。大型鞍座通常采用铸造和焊接结构设计。它充分吸收了全铸和全焊接鞍座的优点。它有很多工程实例，其工艺也比较成熟。作为一种大型结构装置，铸焊鞍座的上部常采用钢铸件。下部常使用多块厚焊接钢板。焊缝数量较多，这也造成主鞍座的焊接困难。主要难点如下：（1）鞍头和座钢板焊接后容易产生冷裂纹;（2）铸件间距小，容易出现焊接操作困难;（3）厚板焊接引起结构刚度增加和应力集中现象，焊接后更容易发生层流撕裂。

4.2. Rolling Saddle 4.2. 滚动鞍座

Taking the Zhanggao River Crossing South Channel Bridge as an example, its bridge cable force and the number of rope strands are large. The larger lattice and cavity size of the saddle body provide a convenient welding condition. The mechanical and physical properties of the castings are excellent, but some problems occur after molding, such as loose organization, coarse crystals, and internal porosity. A thick casting plate leads to larger molding quality and weakened mechanical properties. Therefore, from the point of view of engineering quantity, construction, and structural performance, an all-welded cable saddle design is adopted in the Zhanggao River Crossing South Channel Bridge.
以漳高江跨南海峡大桥为例，其桥梁索力和绳股数量较大。鞍座体较大的晶格和型腔尺寸提供了方便的焊接条件。铸件的机械和物理性能优良，但成型后会出现一些问题，如组织松散、晶体粗大、内部气孔多等。厚铸板会导致更高的成型质量和较弱的机械性能。因此，从工程量、施工、结构性能等方面考虑，张高横江南通道大桥采用全焊接索鞍设计。

Since there is a line contact between the roller shafts and upper and lower plates, it is prone to causing stress concentration in the contact area. Thus, the contact material should be equipped with a significant ability to withstand large contact stress. In the structure design of the rolling cable saddle of the Dongming Yellow River Bridge in China, the overall casting of the saddle body adopts ZG270-480H carbon steel. The bottom surface is inlaid with a 40Cr alloy structural steel sliding plate. The measurement of tempering treatment combined with surface high-frequency quenching is adopted to improve its mechanical properties.
由于滚子轴与上下板之间存在直线接触，因此容易在接触区域引起应力集中。因此，接触材料应具有承受大接触应力的显着能力。在我国东明黄河大桥滚动缆索鞍座结构设计中，鞍体整体铸造采用ZG270-480H碳钢。底面镶嵌40Cr合金结构钢滑板。采用回火处理结合表面高频淬火的测量，提高其力学性能。

It can be seen that the roller shaft is in line contact with the saddle bottom surface and tower top surface. Stress concentration is generated in the contact area, which requires high pressure-bearing properties of the roller shaft material. A thick and large cast plate leads to larger molding quality and weak mechanical properties. Thus, the rolling saddle uses the all-welded saddle design, but faces process difficulties due to immature technology.
可以看出，滚子轴与鞍座底面和塔顶面直线接触。在接触区域产生应力集中，这要求滚子轴材料具有高承压性能。厚而大的铸板会导致更高的成型质量和较弱的机械性能。因此，滚动鞍座采用全焊接鞍座设计，但由于技术不成熟而面临工艺困难。

5. Case Study 5. 案例研究

Taking the rolling saddle of the Zhanggao River Crossing South Channel Bridge as an example, its mechanical situation in the roller area was investigated. Its different components are constructed, including a cable trough, saddle ribs, saddle base and rollers, as displayed in Figure 5. The length and diameter of the roller are 3500 mm and 800 mm, respectively. The length, width, and thickness are 18,000 mm, 4600 mm, and 1000 mm, respectively. The width of the saddle rib is 120 mm. In this paper, the computational analysis of the part of the saddle, the roller and the top surface of the tower was carried out. The middle longitudinal ribs were symmetrically restrained, and the upper and lower surfaces of the roller were in linear contact with the bottom surface of the saddle and the top surface of the tower, respectively. Under vertical pressure, fixed constraints in all directions were set between the saddle and the grill, fixed constraints in the transverse and longitudinal directions were set on both sides of the upper part of the saddle, transverse fixed constraints were set on the base of the saddle and the rollers, and full fixed constraints were set on the top surface part of the cable tower.
以张高江跨南通道大桥的滚鞍为例，考察了其在滚轮区的力学情况。其不同的组件结构包括电缆槽、鞍肋、鞍座底座和滚轮，如图 5 所示。滚筒的长度和直径分别为 3500 毫米和 800 毫米。长、宽、厚分别为 18,000 mm、4600 mm 和 1000 mm。鞍肋的宽度为120毫米。本文对鞍座、滚轮和塔顶面部分进行了计算分析。中间纵肋对称约束，滚轮上下表面分别与鞍座底面和塔顶面直线接触。在垂直压力下，在鞍座和格栅之间设置所有方向的固定约束，在鞍座上部两侧设置横向和纵向的固定约束，在鞍座和滚轮的底座上设置横向固定约束，在电缆塔的顶面部分设置完全固定约束。

Figure 5. Different components of the typical rolling saddle: (A) cable trough; (B) saddle ribs; (C) saddle base; (D) rollers.
图5.典型滚动鞍座的不同组件：（A）电缆槽;（二）马鞍肋;（三）鞍座座;（四）滚筒。

The loading method chosen was the direct face force method. The rib plates are L₁, L₂, …, L₉, L₁₀ from the left, where L₁₀ is the center rib plate, and the rib plates are loaded symmetrically. Table 1 shows the centripetal pressure of each column of cable strands.
选择的加载方法是直接面力法。肋板从左起为L ₁ 、L ₂ 、...、L ₉ 、L，L ₁₀ ，其中L ₁₀ 为中心肋板，肋板对称加载。表1显示了每列电缆绞线的向心压力。

Table 1. Centripetal pressure of each column of cable strands.

Rib Plate	L1	L2	L3	L4	L5	L6	L7	L8	L9	L10
Centripetal pressure (MPa)	23.67	26.35	29.04	31.74	34.45	37.17	39.90	42.64	45.40	48.16

The whole model rolling saddle and cable tower is established and its Mises stress is calculated, as shown in Figure 6. Because the stress situation around the rollers is the main focus, the Mises stress in both sides of the rollers are further investigated. Its distribution is exhibited in Figure 7. The stress of each roller along the transverse direction is extracted, as shown in Figure 8 and Figure 9.
建立整个模型滚动鞍座和电缆塔，并计算其Mises应力，如图6所示。由于滚子周围的应力情况是主要关注点，因此进一步研究了滚子两侧的Mises应力。其分布如图 7 所示。提取每个滚子沿横向方向的应力，如图 8 和图 9 所示。

Figure 6. Whole model rolling saddle and cable tower and its von Mises stress distribution.
图6.整个模型滚动鞍座和电缆塔及其冯·米塞斯应力分布。

Figure 7. Mises stress in the surface of the rollers: (A) upper surface; (B) lower surface.
图7.辊子表面的米塞斯应力：（A）上表面;（二）下表面。

Figure 8. Mises stress distribution in the upper surface of the rollers: (A) Roller 1~3; (B) Roller 4~6; (C) Roller 7~9.
图8.辊子上表面的米塞斯应力分布：（A）辊子1~3;（B） 滚筒4~6;（C） 滚筒 7~9。

Figure 9. Von Mises stress distribution in the lower surface of the rollers: (A) Roller 1~3; (B) Roller 4~6; (C) Roller 7~9.
图 9.滚子下表面的Von Mises应力分布：（A）滚子1~3;（B） 滚筒4~6;（C） 滚筒 7~9。

It can be seen that the maximum von Mises stress mainly occurs in the contact area of the base of the rope saddle and the roller shaft, which is 1078 MPa. The maximum von Mises stress in the upper structure of the rope saddle is 232 MPa, which occurs at the bottom of the saddle groove. For the Q345 steel, yield damage does not generally occur. The maximum von Mises stress of the roller shaft is 773 MPa, which appears at the ends of the lower surface of the roller shaft. The maximum von Mises stress on the top surface of the tower is 885 MPa, which occurs at both ends of the contact area with the roller shaft. Attention should be paid to the Von Mises stress in the contact area between the saddle base and the roller shaft, the lower surfaces of both ends of the roller shaft, and the top surface of the tower, to avoid material damage.
可以看出，最大冯米塞斯应力主要发生在绳鞍与滚轴底部的接触面积，为1078 MPa。绳鞍上部结构的最大冯米塞斯应力为232 MPa，发生在鞍槽底部。对于 Q345 钢，通常不会发生屈服损坏。滚子轴的最大冯米塞斯应力为773 MPa，出现在滚子轴下表面的末端。塔顶面的最大米塞斯应力为885 MPa，发生在与滚子轴接触区域的两端。鞍座底座与滚子轴接触区、滚子轴两端下表面、塔顶表面应注意冯·米塞斯应力，以免造成材料损坏。

6. Characteristics Comparison
6. 特点对比

Through the above analysis of the anti-slip saddle and rolling saddle in the three aspects of structural design, mechanical characteristics, and the casting process, a comparison of their characteristics is summarized in Table 2.
通过以上对防滑鞍座和滚动鞍座在结构设计、力学特性、铸造工艺三个方面的分析，表2总结了其特性的比较。

Table 2. Comparison between an anti-slip saddle and a rolling saddle.

Content		Anti-Slip Saddle	Rolling Saddle
Structural design	Base design	PTFE, bonded connection	Roller contact
	Anti-skid measures	Horizontal and vertical friction plate	Self-equilibrating system
Mechanical characteristics	Contact type	Face contact	Line contact
	Friction type	Sliding friction	Rolling friction
	Stress condition	Welding stress, unbalanced force	Higher vertical forces, stress concentrations
Casting process	Structural fabrication	Cast-welded, mature process	All-welded, complex process
Used materials	Material Selection	Thick steel plates with high welding performance	Highly pressure-bearing contact surface materials

7. Conclusions 7. 结论

In this paper, the anti-slip saddle structure and rolling saddle structure in large-span bridges are studied in three aspects, including design principles, mechanical properties, and the casting process. The main conclusions are as follows:
本文从设计原理、力学性能和铸造工艺三个方面研究了大跨度桥梁中的防滑鞍座结构和滚动鞍座结构。主要结论如下：

(1)

Based on the analysis of design principles and mechanical characteristics, it can be concluded that the anti-slip saddle increases the unbalanced horizontal force in the tower top, leading to saddle material loss and structural wear. The slip phenomenon is prone to occurring in the cable. The original sliding friction is changed into rolling friction. The two sides of the main cable horizontal force and the saddle rolling friction force are designed to be self-balancing, but the stability of the structural performance is insufficient.
根据对设计原理和力学特性的分析，可以得出结论，防滑鞍座增加了塔顶的不平衡水平力，导致鞍座材料损失和结构磨损。电缆中容易发生滑移现象。原来的滑动摩擦力变为滚动摩擦力。两侧主缆水平力和鞍座滚动摩擦力设计为自平衡，但结构性能稳定性不足。

(2)

A rolling saddle in a bridge project was taken as an example and its mechanical situation in the roller area was investigated. The maximum von Mises stress mainly occurs in the contact area of the base of the rope saddle and the roller shaft. The maximum von Mises stress in the upper structure of the rope saddle occurs at the bottom of the saddle groove and that of the roller shaft appears at the ends of the lower surface of the roller shaft.
以某桥梁工程中的滚动鞍座为例，研究了其在滚轮区域的机械情况。最大冯米塞斯应力主要发生在绳鞍和滚轴底部的接触区域。绳鞍上部结构中的最大冯·米塞斯应力出现在鞍槽的底部，滚轴的最大应力出现在滚子轴下表面的末端。

(3)

The stress concentration phenomenon is prone to occurring in the rolling saddle because of the line contact in the contact area, and the rolling saddle is mainly subjected to vertical force, which is also consistent with the analysis of general mechanical characteristics. Thus, attention should be paid to the von Mises stress in the contact area between the saddle base and the roller shaft, the lower surfaces of both ends of the roller shaft, and the top surface of the tower, to avoid material damage.
滚动鞍座由于接触区域的线接触容易出现应力集中现象，滚动鞍座主要受垂直力，这也与一般力学特性的分析相一致。因此，应注意鞍座与滚子轴接触区域、滚子轴两端下表面和塔顶表面的冯·米塞斯应力，以免造成材料损坏。

(4)

Combined with the analysis of stress distribution and the saddle casting process, it is obvious that the casting process of the anti-slip saddle structure is mature, but also faced with problems due to the welding of thick plates, and urgently needs to be improved and upgraded. The rolling saddle is used with the all-welded casting process but its technology is relatively immature and the requirements for the roller shaft material performance are strict.
结合应力分布和鞍座铸造工艺的分析，可以明显看出，防滑鞍座结构的铸造工艺已经成熟，但也面临着因厚板焊接而出现的问题，亟待改进和升级。滚鞍采用全焊接铸造工艺，但其技术相对不成熟，对滚子轴材料性能要求严格。