细部设计：巴厘岛绿色学校的弧形竹结构
Detail: Bamboo Structure of the Arc at Green School Bali  

由专筑网一颗尘土，小R编译

位于巴厘岛的建筑工作室Ibuku完成了一个由漂浮的轻质外壳覆盖的多功能运动场，名为Arc，位于印度尼西亚Abiansemal校园。复杂的屋顶完全由竹子制成、其结构强度源自双曲线几何。Arc是一个依靠当地传统的竹子建筑技术的创新项目。

2021年，Ibuku为绿色学校完成了Arc，绿色学校是一个鼓励在自然环境中学习的机构。竹子项目是校园里的最新项目，校园里已有几个设计理念与学校的初心相一致的实验性建筑，目的是通过与当地社区的合作来传授可持续发展理念。

位于印度尼西亚巴厘岛的Ibuku设计工作室由经营绿色学校的家族创立。Ibuku在印尼语中是“我们的母亲”的意思。Ibuku通过试验竹子的自然形态及与当地工匠合作建立了声誉，这些工匠一生都在用竹子进行建造。

Arc多功能运动场是与德国竹子专家Jörg Stamm和英国结构工程公司Atelier One合作设计的。图像上看该项目很简单，它包括了一个开放的健康空间和健身房。但是在它非凡的覆盖式的曲线外壳上发现了其复杂性，从外部看它像一个光滑的盖布在树林中跳舞，从内部看它拥有一个巧妙的颗粒结构。

Bali-based architecture studio Ibuku has completed a billowing lightweight shell that covers a multipurpose sports court on a school campus in Abiansemal, Indonesia. The intricate roof is made entirely from bamboo, with its structural strength derived from a double-curved geometry. The Arc is a project that innovates while relying on local, traditional techniques for building with bamboo.
In 2021 Ibuku completed the Arc for the Green School, an institution which encourages learning in a natural environment. The bamboo project is the newest addition to a campus which is already home to several experimental buildings designed in alignment with the school’s ambitions to teach sustainability through collaborations with the local community.
The Bali, Indonesia-based design studio Ibuku was founded by the same family which runs the Green School. Ibuku – a word meaning ‘our mother’ in Indonesian – has built its reputation on experimenting with bamboo’s natural forms, as well as working with local artisans that have spent their lives constructing with the material.
The Arc was designed in partnership with the German bamboo specialist Jörg Stamm and UK-based structural engineering firm Atelier One. Programmatically, the project is simple, consisting of an open wellness space and gymnasium. It finds complexity, however, in its extraordinary covering – a curvilinear shell that, from the exterior, appears as a smooth sheet dancing among the trees and, from the interior, boasts an ingenious granular structure.



用竹子建造

竹子具有一定的延展性、耐久性和美学性，这是其他建筑材料难以比拟的。“我们使用竹子的原因很简单，因为在印度尼西亚我们有竹子。”Ibuku的建筑负责人Defit Wijaya说，“这是我们文化遗产的一部分，我们已经用了很长时间了。”

毫无疑问竹建筑的技术具有社会属性。竹子原产于热带气候，在南亚和东亚、南太平洋、中美洲和南美洲大量生长。这些地区的居民几百年来一直在使用竹子，今天的建造者非常了解这种材料的潜力和局限性。

Building with bamboo
Bamboo can yield a certain malleability, durability and beauty that is difficult to compare with other building materials. “We use bamboo simply because we have it in Indonesia,” says Defit Wijaya, Ibuku’s head of architecture. “It’s part of our cultural heritage, and we have been using it for a long time.”
There is no doubt that the know-how of bamboo construction is societal. Bamboo is native to tropical climates and abundant in South and East Asia, the South Pacific, and Central and South America. Inhabitants of these regions have been working with bamboo for hundreds of years, and today’s builders are well-versed in the material’s potentials and limitations.





事实上，在巴厘岛这样的地方，类似Arc这样的项目开始之前几乎没有什么准备工作要做。Wijaya说“我们有很多接受过训练的工匠可以使用这种材料。他们明白如何使用会坏如何使用不会坏。该项目旨在向游客和用户传授竹子知识，我们试图培养人们对这种材料的理念模式。”他说。

竹子是可持续的、坚固的、经济的。虽然不是生长于任何地方，但由于它的丰富性以及在某些气候条件下能够快速生长，它是一种成本相对较低在全球范围内都能可见的低消耗材料。热带竹子通常比温带品种长得更大从而有更厚的壁，这通常会导致用于建筑施工时有更好的结构和机械性能。用于建造Arc的竹子主要来自巴厘岛，还有一小部分来自爪哇。

In fact, there is very little preparation to be done before a project like the Arc commences in a place like Bali. “We have a lot of artisans that can already work with this material,” says Wijaya. “They are trained how to use it. They understand that, if you do this, it will break and, if you do that, it won’t.” The project is, instead, meant to teach visitors and users about bamboo, according to Wijaya. “We try to train the mindset of people about this material,” he says.
Bamboo is sustainable, strong and economical. While not grown everywhere, it is a relatively low cost product that is globally available due to its abundance and speedy growth in certain climates. Tropical bamboos typically grow larger than temperate species and so have thicker walls, which often results in better structural and mechanical properties for use in building construction. The bamboo used to construct the Arc was sourced mostly from Bali, with a small portion from Java.



由于其生长周期短且固碳能力强，竹子也是市场上最多的可持续建筑材料之一。相比于平均需要30-40年才能生产大量木材的树木，竹子可以在大约四年后得到收获。

虽然竹子在农村地区经常被使用，但在大多数城市中，竹子是不允许被用作建筑元素的。这在一定程度上是因为竹子作为天然材料具有可变性，它在接触水时可能会腐烂，且会成为被竹子淀粉，吸引昆虫侵扰。

虽然竹制建筑目前还不能在大城市中见到，但这并不是说竹子在未来不能成为一种典型的结构材料。国际标准化组织(ISO)在2004年发布了三个关于竹制建筑的标准。这些标准参考了现有的木材标准和适用于竹子的物理和机械性能的测试方法。包括中国、哥伦比亚、印度和美国在内的几个国家也在不同程度上采用了自己的竹子标准。例如，2021年，美国测试与材料学会(ASTM)将竹子作为一种纤维材料，可用于制造结构复合木材产品。


传统的材料，先进的几何形状

像Ibuku的其他几个项目一样，Arc的设计从自然界中找到的形式，同时以竹子的特定特性为指导。

Arc是从一个“鞍形的”网格壳的几何形状中派生出来的。薄壳具有一定的强度和刚性由于其弯曲的性质，就像鸡蛋或龟壳的表面。而只有张力而无压缩的拉伸表面则依赖于双曲率来保持稳定性。鞍形的表面呈现两个相反的弯曲方向。Arc将这种压缩结构与受拉表面相交。

With its short growth cycle, and due to its carbon sequestration capacity, bamboo is also among the more sustainable building materials on the market. Bamboo can be harvested after about four years, compared with an average of 30-40 years for trees yielding mass timber products.
While bamboo is readily used in rural areas, it is not permitted by code for use as a structural element in most cities. This is in part to its variability as a natural material, its likelihood to rot when exposed to water, and because it is a target for infestation by insects attracted to bamboo’s starches.
Even as bamboo building cannot yet be seen in major cities, hat is not to say bamboo cannot become a typical structural material in the future. The International Organization for Standardization (ISO) published three standards in 2004 on bamboo construction. These reference existing timber standards with testing methods for physical and mechanical properties adapted to bamboo. Several countries including China, Columbia, India and the USA have also adopted their own standards for bamboo, to varying degrees. In 2021 the American Society for Testing and Materials (ASTM) added bamboo as a fiber material that can be used in the manufacture of structural composite lumber products, for example.

Traditional materials, advanced geometries
Like several of Ibuku’s projects, the design for the Arc draws from forms found in nature while being instructed by the specific properties of bamboo.
The Arc is derived from the geometry of an ‘anticlastic’ grid shell. Thin shells possess strength and rigidity due to their curved nature, such as the surface of an egg or a turtle shell. And tensile surfaces, which carry only tension and no compression, rely on double curvature for stability. Anticlastic surfaces are curved in two opposing directions and take forms such as saddles. The Arc makes use of such tensioned surfaces intersected with a compression structure.





根据建筑师的说法，该项目需要几个月的研究来确定如何构建屋顶的形式。Ibuku使用竹瓦制成的夹层表面形成网格壳，然后支撑在一系列14米高、跨度19米的竹拱门上。计划中该建筑宽23.5米，长41米。这座建筑花了8个月才建成。


材料及内饰

在外壳下760平方米的不间断空间内允许一系列的活动，外壳使其免受巴厘岛赤道阳光的热量直射。由于竹子的结构和外壳都很明显，其内部空间的饰面是温暖、均匀和宽敞的。抬头望去会看到一个纹理复杂的天花板。这些拱门类似于哥特式大教堂的肋状拱顶，从拱门的顶端延伸到地面，沿着精细的线条表达了结构的轻盈。

According to the architects, the project required months of research to determine how to construct the roof’s form. Ibuku employed sandwiched surfaces made of bamboo shingles to form the gridshells, which are then supported on a series of 14-meter tall bamboo arches spanning 19 meters. In plan the building is 23.5 meters wide by 41 meters long. The structure took eight months to construct.

Material and interior
Within the shell an uninterrupted space of 760 square meters permits a range of activities protected from the heat of Bali’s equatorial sunlight. As both the bamboo structure and shell are apparent, the finishes of the interior space are warm, uniform and expansive. Looking up, one sees a ceiling that is textured and complex. The arches resemble the ribbed vaults of a gothic cathedral, extending from the Arc’s apex to the ground along fine lines that express the structure’s physical lightness.





屋顶从地面升起使室内外空间具有渗透性。当阳光从底座进入并从地板上反射时，它在外壳内部弯曲的表面上创造出有趣的、戏剧性的图案。凸起的顶盖设计也可以让微风流过为室内提供自然通风。屋顶顶部的通风口可以让热空气逸出。


竹子保护法

竹子的木质柱子，也就是杆在环或节之间通常是中空的，这给了它们力量。秆从粗大的茎上分枝成簇生长。尽管竹子重量轻、坚韧、耐久，但需要保护它不被长时间暴露在水里和不受阳光照射，最重要的是不受以竹子糖分为食的昆虫的侵扰。

不幸的是，竹子生长的热带和亚热带气候以及最常用的竹子作为建筑材料的地区，同时也是容易出现长湿润季节、极端高温和大量昆虫的地区。因此我们需要充分考虑保护建筑中使用的竹子。

Wijaya说：“在过去的10年或15年里，我们在巴厘岛发现了如何处理竹子使其更持久耐用的方法。”和其他地方一样，巴厘岛的竹秆通常是用硼化学竹溶液来进行保护的，这种溶液是硼砂和硼酸的低毒混合物。

据Wijaya介绍这种处理有两种选择。其方法可以根据项目的时间限制和资源选择：第一种选择是将竹子浸泡在硼溶液中两周以上;第二种方法是将竹子放入溶液中煮沸24小时。在秆暴露在溶液中之前将其首尾相连地打孔，在固体环上形成小孔使化学物质完全渗透到秆中。

The roof is lifted from the ground to allow permeability between the interior and exterior spaces. As the sunlight enters from the base and reflects off of the floor, it bends around the curved surfaces of the shell’s interior and creates interesting, dramatic patterns. The design of the raised canopy also allows breezes to flow through and provide natural ventilation. Vents at the roof's apex allow warm air to escape.

Protecting bamboo
Bamboo’s woody columns, known as culms, are typically hollow between their more solid rings or nodes, which give them strength. Culms grow in branching clusters from a thick stem. While lightweight, tough and durable, bamboo culms need to be protected from prolonged exposure to water, from sunlight and, most importantly, from the infestation of insects which feed on the bamboo’s sugars.
Unfortunately the tropical and subtropical climates where bamboo is native and where buildings are most commonly constructed in the material, are also regions prone to long wet seasons, extreme heat and plenty of insect life. Much consideration is therefore required to adequately protect the bamboo used in buildings.
“It’s only in the last 10 or 15 years that we here in Bali found out how we can treat the bamboo to make it long-lasting and durable,” says Wijaya. As in other places, the bamboo culms in Bali are typically protected from insects with a boron chemical bamboo solution that is a low-toxicity mixture of borax and boric acid.
According to Wijaya, there are two options for this treatment, and the method can be selected based on a project’s time constraints and resources: the first option is to sink the bamboo over two weeks in the boron solution; the second is to boil the bamboo in a chamber with the solution for 24 hours. Before the culms are exposed to the solution, they are punched end to end, to create holes at the solid rings that allow the chemical to completely penetrate the stalk.



为了防止紫外线，竹子上涂了一层带有水基的透明乙烯基饰面层。对于Arc，在建筑的整个生命周期内，每两年需要进行一次。最后，为了保护拱门的结构部件不受天气的影响，深檐和大悬挑被整合到设计中，使拱门永久处于阴影中。


不可预知的情况

Ibuku与工程师合作，工程师提供结构计算和细节，然后提交给竹子承包商进行评估。作为设计顾问，Ibuku提供了一套完整的施工文件，其中详细说明了每个秆的长度。但模型通常是现场传达设计意图的最有效方式。Wijaya说:“物理模型非常重要，因为工匠们根据的是这些模型而不是图纸进行工作。”

To protect against UV, a clear vinyl finishing layer with a water base is applied to the bamboo. For the Arc, this application will be required every 2 years throughout the life of the building.
Finally, to protect the Arc’s structural components from weather exposure, deep canopies and large overhangs were integrated into the design to keep the arches permanently in shade.

Unpredictable conditions
Ibuku works in collaboration with engineers who provide the structural calculations and details, which are then submitted to a bamboo contractor for assessment. And as a design consultant Ibuku provides a full set of construction documents which specify the length of each culm. But models are often the most effective way to communicate design intent on site. “The physical models are very important because the artisans use these instead of working from the drawings,” says Wijaya.





另一个担忧与竹子的可变性有关。“工人们尽最大努力复制模型，但我们使用的是天然材料，所以我们无法预测材料的直径，现场总有调整。”Wijaya说。这是需要Ibuku解决的主要影响，而次要的影响通常由工匠解决。

为了进一步指导工匠以确保施工质量，在结构安装之前制作了一系列的模型测试结构的强度和对设计进行交流。

Another concern has to do with the variability of the bamboo. “The workers try as best as they can to copy the models, but we are dealing with a natural material, so we cannot predict the diameter,” says Wijaya. “There are always adjustments on site.” Major implications require Ibuku’s input, while minor implications are typically resolved by the artisans.
To further guide the artisans, ensure construction quality, test the strength of the structure and communicate its design, a series of mock-ups were produced prior to erection of the structure.



竹子细节

Arc的底座采用了一系列雕刻而成的混凝土底座，这些底座将竹肋与地面连接起来同时使它们安全地远离潮湿的地面。Wijaya称这个基础细节非常简单。“在我所知道的每一个竹结构中，都有一种铰链式的基础细节。根据场地的土壤条件，在地基上设置一个基座，然后将钢筋插入每一片落在基座上的竹子中。”

竹拱安装到位后，在钢筋末端的每根竹竿上打一个小孔。这允许混凝土浇筑到60或70厘米的总深度足以安全地将竹子固定在钢筋上。在一次实地考察中，Ibuku在建造和浇筑拱门之前检查了拱门每根钢筋连接的位置。

Bamboo details
The base of the Arc features a series of sculpted concrete footings, which connect the bamboo ribs with the earth while keeping them safely above the moist ground. Wijaya claims this foundation detail is very simple. “In every bamboo structure that I’ve ever known there is a sort of hinged base detail,” he says. “You have a pedestal set on a foundation based on site soil conditions, and then rebar is inserted into each piece of bamboo that touches down on the pedestal.”
Once the bamboo arches are set in place, a small hole is made in each bamboo culm above the termination of the rebar. This allows for concrete to be poured in up to a total depth of 60 or 70 centimeters, enough to safely anchor the bamboo to the rebar.  During one of its site visits Ibuku checked the position of each of the Arc’s rebar connections prior to the erection and pouring of the arches.







竹拱门似乎从基座上有机地发芽，就像它们从森林里的树干上发芽一样。肋骨被捆扎在一起，在他们的交叉处用钢丝支撑。每根肋骨都用一系列简单的螺钉与网格壳相连接。Arc的屋顶在本质上也很简单，防水层夹在两层竹瓦之间，使结构外壳两边都呈现自然的装饰。

整个肋骨和外壳系统由脚手架固定，在混凝土干燥和结构连接完成后释放出来。

The Arc’s bamboo arches appear to organically sprout from their pedestals as they would from stems in the forest. The ribs are bundled and tied together with steel wire at their crossings for support. Each of the ribs meets the grid shell with a series of simple screws. The Arc’s roof is also simple in nature, a buildup of waterproofing sandwiched between two layers of bamboo shingles that gives the structural shell a natural finish on both sides.
The entire system of ribs and shells was held in place with scaffolding that was only released once the concrete dried and the structural connections completed.