隐桥丨中国浙江丨泛式建筑

2024/11/26 16:57:02

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隐桥，莫干山阜溪七桥中的一桥。泛式建筑在 2022 年七桥国际竞赛中获得了其中两座步行桥梁的设计权，隐桥便是其中一座。

Ephemeral Bridge is one of the seven pedestrian bridges in Fuxi, Moganshan. Far Workshop won two pedestrian bridges in the 2022 Seven Bridges International Competition, and Ephemeral Bridge is one of them.

▼桥梁与环境，bridge and surroundings © Biosphere 建筑摄影

时间

Time

如何让桥跟时间粘结在一起？我们看到了下方流过的潺潺溪水。将隐桥的设计高度降至接近水面，桥便不能独善其身，溪水的涨落时时刻刻都会影响着桥的呈现，我们想起了法国的圣米歇尔山（Mont-Saint-Michel and its Bay)。

How can we bond a bridge with time? We observe the babbling stream flowing beneath. By lowering the design height of Ephemeral Bridge to be close to the water surface, the bridge cannot remain unaffected; the rise and fall of the stream constantly influence the bridge’s appearance, reminding us of Mont-Saint-Michel and its Bay in France.

▼俯瞰，top view© Biosphere 建筑摄影

▼接近水面的桥梁，close to the water surface © Biosphere 建筑摄影

▼潺潺溪水，stream flowing© Biosphere 建筑摄影

我们让桥体微微起拱，当溪水在低水位的时候，整座桥体显露，人们可以自由通行。而当水面升高时，桥面渐渐被水覆盖，由于桥面微拱，最后剩下最顶端的桥面露在水面上，像一座孤岛，暗示着下方桥体的存在，同时也标记出水面仍然还在安全高度范围，人们可以淌着水过桥。当水面继续上升时，桥便被水完全吞没，消失。这样，桥就完成了跟自然的绑定，呈现出自然地景般的时间变化。

在前工业时代，人们不知道自然与人工的边界在哪里，暧昧成为了这条边界的关键词。这种暧昧是危险的，但是也是神秘且富有诗意。进入城镇的制度化之后，暧昧的边界被抽离，所有的空间体验非黑即白，要么绝对安全，要么绝对危险，城市不允许模棱两可的存在。我们的桥试图挑战这种绝对，引入与自然暧昧的边界，重新与自然建立某种诗意的关系。

▼桥跟水面在不同时节的关系变化，

The relationship between the bridge and the water surface changes with different seasons© 泛式建筑

We have given the bridge a slight arch. When the stream is at a low level, the entire bridge is exposed, allowing people to pass freely. As the water level rises, the bridge surface gradually becomes submerged. Due to the slight arch of the bridge, the top part of the bridge remains above the water, like an isolated island, hinting at the existence of the submerged bridge body and also indicating that the water level is still within a safe range, allowing people to wade across the bridge. When the water level continues to rise, the bridge is completely engulfed by the water and disappears. In this way, the bridge is bound to nature, exhibiting the temporal changes akin to a natural landscape.

In the pre-industrial era, people were unaware of where the boundary between nature and artificiality lay, with ambiguity becoming the keyword for this boundary. This ambiguity was dangerous, yet also mysterious and poetic. After entering the era of urban institutionalization, the ambiguous boundary was stripped away, with all spatial experiences becoming black and white, either absolutely safe or absolutely dangerous. The city does not allow for the existence of ambiguity. Our bridge attempts to challenge this absoluteness, introducing an ambiguous boundary with nature, and re-establishing a poetic relationship with nature.

▼与自然暧昧的边界，an ambiguous boundary with nature

结构与构造

Structure and tectonics:

整桥跨度 13.5 米，如同一个扁豆荚，由两片钢板焊接而成。跨中厚度 150mm，由微凸的顶板与水平底板组成箱型截面，截面延伸到支座时，上凸顶板渐变为平面与底板贴合，支座处总厚度减小到 32mm。力学上，豆荚板的上表面受压，而微凸的断面恰好增加了其局部稳定性（桥面附加抗滑钢筋也有辅助作用），箱体内无需设置横隔板及纵肋，大幅简化了构造，降低加工难度。同时让形式与结构形成了高度纯粹化的统一。极薄的桥体如同悬浮在水面的一张纸片，“隐桥”不仅没入了水中，还隐入了空中。

▼剖面概念，sectional concept study© 泛式建筑

▼桥体生成曲面构造线，construction lines for bridge body generation© 泛式建筑

▼上下面边缘满焊后桥体形式，The bridge body after full edge welding© 泛式建筑

▼结构模型参数分析，structural analysis diagrams © 和作结构建筑研究所

The entire bridge spans 13.5 meters, resembling a lentil pod, made from two steel plates welded together. The thickness in the middle of the span is 150mm, consisting of a slightly convex top plate and a horizontal bottom plate forming a box section. As the section extends to the support, the convex top plate gradually becomes a flat surface that adheres to the bottom plate, reducing the total thickness at the support to 32mm. Mechanically, the upper surface of the lentil plate is under compression, and the slightly convex section increases its local stability (the anti-slip steel bars attached to the bridge surface also play a supportive role). There is no need to set up transverse diaphragms or longitudinal ribs inside the box, which greatly simplifies the structure and reduces the difficulty of processing. At the same time, it forms a highly purified unity of form and structure. The extremely thin bridge body is like a piece of paper floating on the water surface. Ephemeral bridge not only merges into the water but also blends into the air.

▼隐入空中，blends into the air© Biosphere 建筑摄影

▼桥梁与河面，bridge and the river© Biosphere 建筑摄影

为了防滑，我们铺设了由螺纹钢筋所拼成的防滑桥面，部分钢筋延展而上，形成了栏杆及扶手。

▼三维剖面及扶手示意，3d section & balustrade study© 泛式建筑

To prevent slipping, we have installed an anti-slip bridge surface made up of reinforcing steel bars. Some of these bars extend upwards to form railings and handrails.

▼螺纹钢筋所拼成的防滑桥面及扶手，anti-slip bridge surface and handrails made up of reinforcing steel bars© Biosphere 建筑摄影

施工

construction

由于钢板尺寸的限制，这个桥在施工过程中上下两片钢板分别被分解成九段。相比于底面钢板，上层的每块钢板都需要通过压轴机来校准弧度，从而满足设计要求。在底面钢板全部焊接结束后，上层弧面的钢板才依次与底面钢板进行边缘满焊。最后再安装桥面防滑铺设以及相应的扶手。

▼钢板分解示意，Steel Plate Breakdown Schematic diagram© 泛式建筑

▼桥梁分解示意，Bridge Structure Explosive Diagram© 泛式建筑

▼桥梁施工现场，Bridge Factory Construction Scene© 泛式建筑

Due to the limitations of steel plate dimensions, the bridge is divided into nine sections for both the upper and lower steel plates during construction. Compared to the bottom steel plate, each piece of the upper steel plate needs to be calibrated to the required curvature using a press machine. After the bottom steel plate is fully welded, the upper curved steel plates are then sequentially edge-welded to the bottom steel plate. Finally, the bridge deck anti-slip paving and corresponding handrails are installed.

▼桥梁施工现场，in construction© 泛式建筑

▼连续横截面变化，continuous cross-sectional variation© 泛式建筑

隐桥虽然结构系统简单，但实现方式并不常规，为了验证结构安全性，在出厂前即进行了全桥堆载实验。同时对于极致轻薄的结构，除静载外，其自振引发的舒适度问题也得到了关注。虽桥体独立工作时基本无阻尼，但吊装完成后，支座与基础的附加阻尼有显著贡献，振动快速消散至无感状态。

Although the structural system of the Hidden Bridge is simple, its implementation method is unconventional. To verify the structural safety, a full bridge load test was conducted before leaving the factory. At the same time, for the extremely thin structure, in addition to the static load, the comfort issue caused by its own vibration has also been paid attention to. Although the bridge body has almost no damping when working independently, after the hoisting is completed, the additional damping of the support and the foundation makes a significant contribution, and the vibration quickly dissipates to an imperceptible state.

▼3.5kN/m² 全桥堆载/振动实验 © 和作建筑结构研究所

▼概览，overview© Biosphere 建筑摄影

后记

Epilogue

极薄的“隐桥”的极致的结构所带来的假装的“危险脆弱”会让人们刚上桥的时候小心翼翼，但是桥面的稳定很快会使人们打消疑虑，桥面极度接近水面，人们行走之时犹如行走在水面之上，但是又保持了某种安全感，这种复杂的身体及心理的知觉会持续带来某种矛盾的惊奇感，“隐桥”触发了人们对脚下空间的身体知觉，“隐桥”不隐。

The extremely thin ‘Ephemeral Bridge’, with its extreme structure that feigns ‘dangerous fragility’, initially makes people tread carefully as they step onto it. However, the stability of the bridge surface quickly dispels their doubts. The bridge deck is extremely close to the water surface, making people feel as if they are walking on the water itself, yet it maintains a certain sense of security. This complex mix of physical and psychological perception continuously brings about a sense of paradoxical wonder. The ‘Ephemeral Bridge’ triggers people’s bodily perception of the space beneath their feet; the ‘Ephemeral Bridge’ is not invisible.