竹构飞桥 | 传统工艺的现代演绎

桥，在传统中国，是一种饱含“情”与“志”的标志物。一方面，在乡村造桥是一种功德或是纪念；另一方面，“桥”是一种诗情的想象，在传统山水画的谋篇中，是整个画境的入口和起点。不只是物本身，桥是一个可以入画的艺术形象，造桥是一个福祉于民的社会事件。

Bridge, in traditional Chinese culture, is a sign full of “emotion” and “will”. On one hand, building a bridge in the countryside is a kind of merit or commemoration; on the other hand, “bridge” is a kind of poetic imagination, in the strategy of traditional landscape painting, it is the entrance and starting point of the whole painting. Not only the thing itself, the bridge is an artistic image that can be painted, and building a bridge is a social event that benefits the people.

▼场地环境，context

项目的场地位于安徽祁门县桃源村。一条10米宽的水系贯穿村头村尾，阻隔了村落和农田。为了便于村民去田间耕作，需要增加一座人行桥。水系是居住和劳作的分界线，而桥则是通向田园山野的入口。后山上，毛竹密布。用竹子建造，材料本身取之于自然，为人所用，是一种在地的营造。

▼场地原貌，the original site

The project is located in Taoyuan Village, Qimen County, Anhui Province. A 10-meter-wide water system runs through the head and end of the village, blocking the village and farmland. In order to make it convenient for the villagers to farm in the fields, an additional footbridge is needed. The water system is the dividing line between living and working, while the bridge is the entrance to the countryside. The back mountain is covered with bamboo. To build with bamboo, taking the material itself from nature and using them for the purpose of human beings, is a kind of construction methodology based on the local environment and resources.

▼悬岸飞桥外观，the bamboo bridge

▼鸟瞰图，aerial view

确定了造桥的材料之后，这座桥该以怎样的画意呈现？

After determining the materials for the construction of the bridge, what kind of poetic approach should we use to present the bridge?

竖向挺立是重力最直白的表达，压弯才是对重力的一种诗意的刻画。不同于木构与石构，竹材本身就具有良好的可弯曲的韧性，而且通过人工的火烤工艺，弧线曲率变得更加可塑，为人所驭。被烤弯的竹子，随着时间推移，会逐渐产生回弹力，这是一种天然的预应力。

Standing upright is the most straightforward expression of gravity, while bending is a poetic portrayal of gravity. Different from wood structure and stone structure, bamboo itself has good bendable toughness, and through artificial fire roasting technology, the arc curvature becomes more malleable and controlled. Processed bamboo, with the passage of time, will gradually produce resilience, which is a kind of natural prestress.

▼被烤弯的竹子（左）和施工过程（右），the processed bamboo (left) and construction phase (right)

如何实现一个跨度为10米的桥梁，简支梁桥和拱桥是最适合的结构选型，但是河岸一侧，桥头正对两棵树，若要做成桥基础无疑会破坏树根，为了避免影响树，选择了悬臂梁结构。

How to construct a bridge with a span of 10 meters, the simply supported beam bridge and the arch bridge are the most suitable structural selections. But on one side of the river bank, the bridgehead is facing two trees. if you want to make the foundation of the bridge, it will undoubtedly destroy the tree roots. Therefore, the cantilever beam structure is chosen in order to avoid affecting the tree.

▼悬臂梁结构避免了对树的影响，the cantilever beam structure is chosen in order to avoid affecting the tree

▼河岸一侧的树得以保留，the trees are remained on the river bank

德国结构力学家库尔曼，在1866年就绘制了一张悬臂梁的结构主应力轨迹线。可以看到一个受到均布荷载下的悬臂梁，可以将其复杂的应力简化为图中的轨迹线，即当我们沿着应力线布置成仅仅受拉或者受压的二力杆，则达到了结构的最大效率。这也是后来工程师对结构构件进行格构化的依据和方法，比如造于1890年的福斯湾大桥即是一种钢结构桁架悬臂梁。

Kullmann, a German structural mechanist, drew a structural principal stress trajectory of a cantilever beam in 1866. It can be seen that the complex stress of a cantilever beam under uniformly distributed load can be simplified to the trajectory line in the diagram, which is, when it’s arranged as a two-force bar under tension or compression along the stress line, the maximum efficiency of the structure is achieved. This is also the basis and method for engineers to grid the structural members later. For example, the Forth Bay Bridge, built in 1890, is a kind of steel truss cantilever beam.

▼福斯湾大桥（左）和库尔曼绘制的悬臂梁的结构主应力轨迹线（右），the Forth Bay Bridge (left) and the structural principal stress trajectory of a cantilever beam by Kullmann (right)

然而对比库尔曼的原图我们发现，真实的合理主应力线其实是弯曲的，然而在工业化制作的钢结构和混凝土结构当中，弯曲的成本较高，只能简化为直线的三角形单元桁架。竹子的弯曲特性，可以更加接近合理应力线，比起工业化的材料更具有一种理性的优势。

However, comparing with Kullmann’s original drawing, we find that the real reasonable principal stress line is actually curved. However, in the industrial production of steel structure and concrete structure, the bending cost is higher. It explains why they are simplified to a straight triangular element truss. The bending characteristic of bamboo can be closer to the reasonable stress line and has a rational advantage over industrial materials.

▼竹子的弯曲特性可以更加接近合理应力线，the bending characteristic of bamboo can be closer to the reasonable stress line

▼西侧视角，view from the west

通过对竹桥建模和结构计算可以看出，每一根竹竿的弯矩被很好得平均分布在整根竹竿，而轴力则是逐渐递增。符合材料的属性和应力分配的设想。

Through the modeling and structural calculation of the bamboo bridge, it can be seen that the bending moment of each bamboo pole is well distributed evenly in the whole bamboo pole, while the axial force increases gradually. It is in accordance with the properties of the material and the assumption of stress distribution.

▼内力恒载弯矩（左）和内力恒载轴力（右），beam bending moment (left) and

axial force

(right)

桥面扶手同桥身融为一体，成为主要的结构高度，而桥面较为平缓，利于行走。桥身上弧线的为受拉杆件，直线的为受压杆件，有效避免了竹子受弯不利的弱点。竹结构的节点是核心技术问题。通过钢片加强以及竹筒中用混凝土灌浆来加强节点，另外增加不锈钢抱箍解决了竹子日久开裂强度下降的问题。

▼平缓的桥面，a gentle bridge deck

The handrail of the bridge deck is integrated with the bridge body and becomes the main structural height, while the bridge deck is relatively gentle and easy to walk. The arc on the bridge body is the tension bar, and the straight one is the compression bar, which effectively avoids the disadvantageous weakness of bamboo bending. The node of bamboo structure is the core technology. The joint is strengthened by steel sheet and concrete grouting in the bamboo tube, and the stainless steel hoop is added to solve the problem of bamboo cracking or the decrease of strength with the passage of time.

▼模型，model

▼施工过程，process

最终，竹构悬臂桥，仅靠竹子的力量，自一岸飞架而出，直达对面，形成悬岸飞桥的画面。桥的端头同对岸脱开，犹如“断桥”，强化了悬臂这一结构形式的奇观感，形成了一种因结构张力而产生的戏剧性。

In the end, the bamboo cantilever bridge, relying only on the power of bamboo, flies out from one bank and goes straight to the opposite side, forming a picture of the overhanging flying bridge. The end of the bridge is separated from the opposite bank, like a “broken bridge”, which strengthens the sense of wonder of the structural form of the cantilever and forms a kind of poetic drama caused by the structural tension.

▼仅靠竹子的力量，自一岸飞架而出，the bridge flies out from one bank relying only on the power of bamboo

▼“断桥”般的观感， a “broken bridge”

▼场地平面图，site plan

▼轴测图，axon

▼平面图，plan

▼剖面图，section

▼节点，details

项目名称：悬岸飞桥

业主：祁门皖农旅游投资发展有限公司

设计方：来建筑设计工作室

项目类型：桥

竹结构施工：上海境道原竹建筑设计工程有限公司

地理位置：安徽省，黄山市，祁门县，闪里镇

主持建筑师：马科元

结构顾问：常江

设计团队：龚澄莹，陈运，胡霄玥

摄影：唐徐国，赵奕龙

结构：竹结构

用地面积：20 m²

建筑面积：20 m²

设计周期：2018年3月-2018年9月

建设周期：2018年10月-2019年5月