A 23-kilometer-long network of footpaths allows the residents and visitors of Xiamen to reach the nearby nature with a shortwalk. As most of the ”Xiamen Mountains to Sea Trail” is elevated, it provides a perfect opportunity for family outings as well as uninterrupted runs and walks. The footpath is the latest addition to Xiamen’s unique approach to infrastructure. Being denser populated than Hong Kong (7150 inhabitants/km2) and Singapore (7800 inhabitant/km2), the Island of Xiamen (15 000 inhabitants/km2) is in need for unique approaches to public transport. Among these is Xiamen's Bus Rapid Transit system (BRT), a 70km long network of bridges that is exclusively used by buses. It was the first of its kind in China when it opened in 2008. Another notable and award-winning piece of infrastructure was added in 2017 with the Xiamen Bicycle Skyway. The 8-kilometer-long elevated pedestrian and bicycle path covers the city’s five major residential areas and three business centers. For most of its length, it runs either along or underneath the formerly mentioned BRT system on the Island. Like the Xiamen Mountains to Sea Trail, it was designed by the Danish architectural firm Dissing+Weitling.
A 23-kilometer-long network of footpaths allows the residents and visitors of Xiamen to reach the nearby nature with a shortwalk. As most of the ”Xiamen Mountains to Sea Trail” is elevated, it provides a perfect opportunity for family outings as well as uninterrupted runs and walks. The footpath is the latest addition to Xiamen’s unique approach to infrastructure. Being denser populated than Hong Kong (7150 inhabitants/km2) and Singapore (7800 inhabitant/km2), the Island of Xiamen (15 000 inhabitants/km2) is in need for unique approaches to public transport. Among these is Xiamen's Bus Rapid Transit system (BRT), a 70km long network of bridges that is exclusively used by buses. It was the first of its kind in China when it opened in 2008. Another notable and award-winning piece of infrastructure was added in 2017 with the Xiamen Bicycle Skyway. The 8-kilometer-long elevated pedestrian and bicycle path covers the city’s five major residential areas and three business centers. For most of its length, it runs either along or underneath the formerly mentioned BRT system on the Island. Like the Xiamen Mountains to Sea Trail, it was designed by the Danish architectural firm Dissing+Weitling.
通过一条长达 23 公里的山海健康步道，让厦门的居民和游客不需远行就可以近距离接触大自然，这是城市与设计师提供给大众的便利。“山海健康步道”大部分属于高架的步道，为家庭出游以及不受干扰地跑步和徒步提供了绝佳的机会，是厦门新增的一项特别的基础设施。厦门的人口密度（ 15000 人 / 平方公里）比香港（ 7150 人 / 平方公里）和新加坡（ 7800 人 / 平方公里）还要大，需要建设一些特别的公共交通方式。如厦门快速公交系统（ BRT ）便是其中一种，它是公交车专用的 70 公里长的桥梁线路网络， 2008 年投入使用时，是中国首个此类型的公共交通方式。 2017 年，厦门又新增了另一项引人注目且屡获殊荣的基础设施，也就是厦门空中自行车道，这条 8 公里长的高架人行和自行车道覆盖了厦门市的五个主要居民区和三个商业中心，其大部分路段沿着 BRT 系统或在 BRT 系统下方运行，与山海健康步道一样，该空中自行车道均由丹麦建筑师事务所 Dissing + Weilling 设计。
In general, the Mountains to Sea Trail is designed as an elevated footpath but where topology and built environment allow for it, the path changes into a ground path. The cross-section of the path changes with its surroundings. In urban areas, the footpaths use a closed hollow-box cross-section while it uses an open section in natural surroundings. Both sections are designed to span approx. 20m if continuously supported. At several locations, it is not possible to span the underlying streets, crossings or natural topology with 20m spans, and bridges with larger spans are necessary. These bridges are intended to stick out from the repetitiveness and simplicity of the footpath. They stick out from an architectural as well as from an engineering point of view as they use a bunch of different structural systems. These bridges include:
Bridge #1: 30m high circular bridge tower with a cantilevering spiraling walkway
Bridge #2: mono-cable suspension bridge with curved bridge deck and 220m main span
Bridge #3: inclined arch bridge with curved bridge deck and 90m main span
Bridge #4: double-span beam bridge with 40m main span
Bridge #5: mono-cable suspension bridge with 70m main span
Bridge #6: cable suspended and underslung supported bridge with 85m main span
整体来说，山海健康步道是一条高架的步道，但在地理和建筑环境允许的情况下，步道考虑降低至地面，更为贴近自然。步道结构的构件截面在设计上会根据周围环境而有所不同，在市区段采用封合的空心箱型截面，而在自然环境中则可以采用开放式的横截面，允许雨水等直接从桥面进入自然，行人也可以透过桥面空隙看到桥下自然景致；在步道有连续支座的情况下采用这两种截面都可能实现 20m 的跨度。但在某些位置，如要跨越下方的街道、交叉路口或 20 米跨度的自然地形是不可能的，必须采用更大跨度的桥梁才能实现。山海健康步道上的设计采用的桥梁与步道本身重复和简单的外观截然不同，从建筑和工程的角度来看，这些桥梁通过使用一系列不同的结构体系，将桥梁从重复和简单的步道中跳跃出来。这些桥梁包括：
1号桥：30m高的圆柱状景观塔，悬挑的步道沿桥塔螺旋状盘旋而上；
2号桥：V型塔单侧悬挂曲线型悬索桥，主跨220m；
3号桥：单侧悬挂曲线型提篮式拱桥，主跨90m；
4号桥：双跨梁桥，主跨40m；
5号桥：单塔悬索桥，主跨70m；
6号桥：下承式悬索桥，主跨85m；
7号桥：下承式桁架桥，主跨90m
▲ illustration: pictures of Bridges #1, #3, #5, #6 - picture copyright: schlaich bergermann partner / Gustav Krieg / 图示: 节点1号、3号、5号、6号桥梁– 图片版权：schlaich bergermann partner / Gustav Krieg
After a successful competition phase, schlaich bergermann partner supported Dissing+Weitling with a feasibility study for bridges #2, #3, and #6. With the project progressing fast, the client decided to involve three structural engineering offices into the design process of the large-span bridges. sbp got contracted to design bridges #2 and #3. With Bridge #2, called Hemei Bridge, schlaich bergermann partner was able to design not only the bridge with the longest free span but also the one with the most daring structural concept of the bridges along the Xiamen Mountains to Sea Trail. sbp collaborated with the Xiamen-based structural engineering firm Xiamen Municipal Engineering Design Division Co., Ltd for this project. The construction of the bridge was finished and the bridge is now open to the public as an integral part of the footpath. We would like to use this possibility to provide an insight into the design and construction process of this remarkable bridge.
竞赛阶段之后， sbp 施莱希公司对 2 号、 3 号和 6 号桥梁进行了可行性研究以支持 Dissing+Weilling 建筑师事务所的工作。由于工程进展迅速，业主决定委托三家结构工程单位加入大跨度桥梁的设计， sbp 施莱希公司负责设计 2 号和 3 号桥梁。其中 2 号桥梁名为“和美桥”，它是世界上最长的弧形单侧悬索人行桥，也是山海健康步道沿线桥梁中结构方案最大胆的一座， sbp 施莱希公司与厦门市的结构工程单位 - 厦门市市政工程设计院有限公司合作完成了该项目。 和美桥已顺利竣工，它 作为健康步道的一部分已经向公众开放。本文将深入介绍这座标志性桥梁的设计和施工过程。
The biggest change between the bridge design that was proposed in the competition and the final design was the shape of the mast. In the early design stages, the bridge featured a singular 70m tall mast. Being the structurally most straightforward solution, this approach raised concerns regarding the height and Feng-Shui of a singular mast with sharp edges. An option with a 52m high V-shaped Mast was able to overcome both concerns and was chosen as the preferred option by the client.
竞赛阶段提出的桥梁方案与最终实施方案之间最大的不同是桥塔的形状。在早期设计阶段，桥梁采用了单独一根 70 米高的桥塔。这种设计在结构上是最直接的解决方案，但这个具有独桥塔在视觉上呈现较为锐利的视觉冲击，在高度上和风水方面都引起了各方的关切和担心，所以需要进行调整。调整后的设计采用 52 米高的 V 形桥塔的方案，从而被业主选为最终实施方案。
Replacing the single mast with a V-shaped mast had a strong impact on the appearance of the bridge while it had only minor effects on the flow of forces and the structural efficiency. For both variants, the biggest impact on the structural efficiency of the bridge has the position of the mast tip as this parameter determines the forces in the main cable. While a lower main cable force obviously leads to a smaller main cable diameter, the big impact of a smaller main cable force lies within the reduction in cost and material needed to anchor the forces of the main cable and the bridge deck at both ends of the bridge. The most important relationship to understand in this regard is that mast height and the horizontal distance of the mast tip from the deck are correlated. A higher mast tip will also move the mast tip further away from the bridge deck. For a better understanding of this correlation, it is essential to understand the global force flow of the bridge.
用 V 形桥塔代替单桥塔对桥梁的外观有很大的影响，而对力的传递和结构效率的影响很小。对桥梁结构效率影响最大的是桥塔顶标高，因为该参数决定了主缆中力的大小。索力减小意味着索的直径也会减小，相应地，较小的索力就意味着降低成本，以及减少主缆锚固支座结构的体量。在这方面需要理解的最重要的关系是，桥塔的高度与桥面到塔顶之间的水平距离是相关的，塔顶越高，塔顶与桥面之间的水平距离就越大。为了更好地理解这种相关性，有必要理解桥梁的整体受力分析。
A large fraction of the acting forces of the bridge is the dead-load and superimposed dead load of the bridge deck (F G in the illustration below). While regular suspension bridges have vertical hangers, this is impossible for curved bridge decks as the main cable would have to follow the curved geometry of the deck which it can’t if it has only vertical forces (from the vertical hangers) acting on it. Therefore, the hangers have to be inclined to suspension bridges with significantly curved bridge decks.
作用于桥梁的力很大一部分来自桥面的恒荷载和超静载（下图中的 F G ）。常规悬索桥有竖向悬索，但弧形桥面的悬索桥不能这样做，因为主缆必须沿着桥面的弧度，如果只有（来自竖向悬索的）竖向力作用在桥面上，则不能实现这种弧度，因此，对于桥面具有明显弧度的悬索桥，悬索只能倾斜布置。
Due to the eccentricity and inclination of the hanger cables, the acting dead load F G also creates a rotational bending moment (M Deck ) and a horizontal force (F Deck ). Both, the bending moment and the horizontal Force can only be transferred to the abutments through the bridge deck. In a straight bridge deck, this rotating moment would cause a torsional moment which would increase towards the abutments. This is not the case for a curved bridge deck and can be easily understood if the rotating moment is replaced by a force couple (F TOP and F BOTTOM )
由于悬索偏心和倾斜布置，恒荷载 F G 会产生倾覆弯矩（ M Deck ）和水平力（ F Deck ），且二者都只能通过桥面传递到桥台支座上。在直线型桥面上，该倾覆弯矩会产生一个扭矩且扭矩会沿着桥台方向而增大。弧形桥面则与其不同，倾覆弯矩分解为一对力偶（ F TOP 和 F BOTTOM ）作用其上。
If the forces from the force couple are shown in a plan view of the bridge it becomes clear how the acting forces are transferred to the abutments. As the force couple is applied in every hanger axis, the system works similarly to a pressure tank. The upper horizontal force(F TOP ) generates a constant compression force in the upper flange of the bridge deck while the lower force (F BOTTOM ) generates a constant tension force in the lower flange of the bridge deck. Following this understanding, the closed hollow-box is structurally not necessary and could be replaced by an open, dissolved cross-section with a distinct upper compression ring and a lower tension ring. The liberty bridge in Greenville (USA) is one example by sbp that uses this approach of a suspension bridge with a curved and dissolved bridge deck.
如果将力偶作用力示意在桥梁的平面视图上，那么该作用力是如何传递到桥台就能表达得很清楚了。取力偶作用于悬索轴上的平面示意图，结构体系的工作原理类似于压力罐，上部水平向力（ F TOP ）在桥面上翼缘产生恒定的压力，下部的力（ F BOTTOM ）在桥面下翼缘产生恒定的拉力。基于这一理解，采用封闭的空心箱型截面在结构上并不是必须的，同样可以采用开口式的截面具备受力清晰的上部受压环与下部受拉环的结构体系。位于美国 Greenville 市的自由桥是 sbp 的一个采用该设计思路的实施项目案例，它是一座弧形桥面同时采用开口截面的悬索桥。
The Hemei Bridge in Xiamen however has a closed box section which is beneficial in multiple ways. First of all it follows the identity of the bridge family of the Xiamen Mountains to Sea Trail and the vision of the architects to have closed sections when the path is part of the cityscape and open section in natural surroundings. Second, the closed section does significantly improve the dynamic behavior of the bridge and furthermore reduces the deflections of the bridge from non-symmetrical loadings.
在厦门的和美桥项目上，我们采用了封闭式的箱形截面，这在多方面是有益的。首先，它遵循了山海健康步道沿线桥梁系列中的桥形设定以及建筑师的设计意图，即当步道是城市景观的一部分时，采用封闭的截面，当远离城市景观而处在自然环境中时则采用开口式截面；第二，封闭式截面显著改善了桥梁的动力性能，并进一步减小了桥梁在非对称荷载作用下的变形。
As described earlier, geometrical and structural principles require inclined hangers in suspension bridges with curved bridge decks. The inclination of the hangers depends on the position of the mast tip and main cable anchorage. While the position of the latter can normally not be changed in a way to have a meaningful impact on the structural performance, the mast tip position should be determined through an optimization process. Within reasonable limits, a higher mast tip reduces the main cable force as a higher mast tip increases the sag of the parabolic main cable shape in elevation. However, the height of the mast should not be changed without changing the distance between the mast tip and the bridge deck in plan view as the resulting main cable force is a combination of two parabolas. The vertical and horizontal components of the Hanger Force is transferred through a vertical and horizontal parabola. As both force components are transferred through the same cable, the shape of the main cable follows a three-dimensional shape which results from the overlay of the vertical and horizontal parabola. Optimizing both parabolas at the same time will determine the optimal distance between the mast tip and the bridge deck in plan view as a function of the mast height. If the mast tip position is determined with such an optimization process the lowest possible main cable force for a given mast height can be ensured.
如前文所述，根据桥梁几何和结构受力原理，弧形桥面的悬索桥其悬索应该倾斜布置，倾斜度取决于塔顶和主缆锚固点的位置，后者的位置通常情况下已经确定，主要对于结构性能会产生影响。对于塔顶的位置，应通过优化设计过程来确定。在合理的范围内，较高的塔顶能够减小主缆中的力，因为较高的塔顶会增加抛物线形的主缆在立面上的垂度。但是，如果塔顶与桥面在平面上的距离不变，则不应改变桥塔的高度，因为主缆中的力是两抛物线组合作用的结果。悬索中竖向力和水平力分量通过竖向和水平向抛物线传递，且两向分力通过同一根索传递，主缆的形状是竖向和水平向抛物线叠加的三维几何。同时优化两条抛物线将确定平面中塔顶和桥面之间的最佳距离，该距离也是确定桥塔高度的其中一个函数。通过这种优化过程确定塔顶位置，就可以确定桥塔高度下主缆中所产生的最小索力。
In general, changing the single Mast tip into a double-tip has no significant influence onto the force flow and efficiency of the bridge. However, this is only the case if the hanger cables keep their radial arrangement in plan view and some of the hangers are connected to the cable that spans between the two mast tips. The resulting appearance of that principle was aesthetically not convincing and we adjusted the orientation of the hangers in a way that no hanger cable would connect to the cable between the mast tips. In the final design, the hangers now emphasize the V-shape of the mast, giving the bridge a consistent and eye-pleasing overall appearance.
总体上讲，将单塔改为双桥塔对桥梁结构的受力和效率影响不大。但是，只有当悬索在平面中保持径向排列，并且部分悬索与两个塔顶之间的索相互贯通连接时，这种结论才成立。基于该原理而设计出的桥梁的最终外观在美学上并不如人意，我们调整了悬索的排布，使悬索并不与两个塔顶之间的连接索相连。在最终的设计方案中，悬索更能强调桥塔的 V 形形状，使桥梁整体外观在视觉上是协调的，也是让人愉悦的。
Having the design fixed, the most challenging part of the project started: Getting it built. After all, it is the first large-scale bridge of its kind in China and also the longest mono-cable suspension bridge with a curved bridge deck in the world.
设计完成后，项目最具挑战性的部分开始了：建造它。毕竟，它是中国同类型桥梁结构中第一座如此大跨度的桥梁，也是目前世界上最长的弧形单侧悬索人行桥。
Extensive wind-tunnel testing was conducted to ensure the bridge would withstand typhoons with wind speeds of up to 300km/h. To improve the bridge performance under severe wind loads the cross-section of the bridge was modified. A 600mm long baffle plate was added along the outside of the bridge which acts as a wind splitter and improves the aerodynamic behavior of the bridge drastically. By shifting the lower horizontal flange plate of the cross-section more towards the middle, a more symmetrical section was generated which reduced the acting wind loads further. As this change also moved the center of gravity of the cross-section further away from the hanger connection this adjustment had to be chosen carefully to balance the aerodynamic benefits and the resulting structural disadvantages. While both measures improved the bridge's aerodynamic behavior, the resulting wind loads are still high. Characteristic wind pressures onto the Mast reach values of up to 8.20kN/m2 and uplifting wind pressures onto the bridge deck are as high as 1.75 kN/m2.
对桥梁开展了充分的风洞试验，从而确保其能够抵御风速高达 300km/h 的台风。为了改善桥梁在恶劣风荷载作用下的性能，我们对桥梁的横截面进行了修改，沿桥梁外侧增设了一道 600mm 长的折流板，起到了分风的作用并能大大改善桥梁的空气动力性能。通过折流板将作用于桥梁横断面的水平力进行分流，减弱风直接于下翼缘的作用力，使风荷载作用面更为对称，从而进一步减小了风荷载作用。由于这一变化使横截面的重心进一步远离悬索节点，因此必须精心设计这种调整，以平衡空气动力优势和由此产生的结构劣势。虽然这两种措施都改善了桥梁的空气动力性能，但由此产生的风荷载仍然很高。桥塔上的基本风压高达 8.20kN/m 2，桥面上的风吸力高达 1.75kN/m 2。
Having never seen a similar bridge before, local authorities and several other involved parties had to be convinced that such a bridge was buildable and safe.
Having never built a similar bridge before, the involved companies responsible for calculation and supervision of the construction sequence as well as the construction company themselves had countless doubts if the proposed construction sequence was feasible. It took great efforts and many meetings to overcome these concerns one by one.
也由于之前从未建造过类似的桥梁，负责计算和施工顺序监督的相关方以及施工方对拟定的施工顺序是否可行产生了无数疑问，经过多次的会议沟通和各单位的共同努力，这些问题都逐一得到了解决。
Undoubtedly, the pre-stressing of the bridge, which involved a well-coordinated movement of the two mast tips by approx. 1.0m each, was the most challenging step during construction. The pre-stressing started first and after 3 days all 10 steps of the process had been finished successfully. The installation of 21 tuned mass dampers followed shortly after. 19 of them are installed in the bridge deck to reduce human-induced vibrations from 3 critical eigenfrequencies. The remaining 2 dampers are installed inside the mast to prevent undesirable wind-induced vibrations. After the application of the thin-layer coating, the bridge was inaugurated successfully.
毫无疑问，施加预应力是桥梁施工过程中最具挑战性的一步，它涉及到两个塔顶的良好协调运动。为此，首先两个塔顶向桥面一侧预偏约 1.0m 。施加预应力之后 3 天内，施工过程中的所有 10 个步骤均成功完成，紧接着安装了 21 个调谐质量阻尼器，其中 19 个安装在桥面中以减小三个控制振型下导致的人致振动，剩余 2 个安装在桥塔内以防止不必要的风致振动。最后，外表面施加涂层后，大桥成功落成。
Bridge information
construction: JIANGSU PROVINCIAL TRANSPORTATION ENGINEERING GROUP CO.,LTD
桥梁相关信息：
桥梁总长：234.7 m
主跨跨度：216.7 m (曲线距离)，202.2 m (直线距离)
半径：167.7 m
走道宽度：3.8 m
桥面结构高度：1.20 m
结构形式: V型塔单侧悬挂曲线型悬索桥
业主：厦门市市政建设开发有限公司
建筑设计：Dissing + Weitling Architecture
结构设计: sbp施莱希工程设计咨询有限公司
本地院： 厦门市市政工程设计院有限公司
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about schlaich bergermann parner (sbp)
schlaich bergermann partner (sbp) are globally prestigious consulting civil and structural engineers with the headquarter in Stuttgart, Germany. Since it was founded in 1980s, schlaich bergermann partner (sbp), has never stopped contributing to the excellence of marvelous architectural works with its outstanding expertise and professional mind as structural engineers. Our involvement in prestigious international projects requires that we operate globally and to better serve our clients, so we established office branches in Berlin, New York, S?o Paulo, Shanghai, Paris and Mardrid. With totally around 190 staffs, we stick to the principle of “elite” as company growing strategy.
