砂漠に現れる木製トラスと膜による球状の屋根

©︎ Cristóbal Correa

©︎ Cristóbal Correa

チリ中央部の砂漠の標高2,900m地点に建つ〈アルマ・スポーツファシリティズ（Alma sports facilities）〉は、日射や風、砂塵や雪、寒暖差といった過酷な環境に適応した空間を提供するスポーツ施設です。

建物のメインフロアを地下化し、地表に出る屋根を曲率を抑えた木製アーチと膜構造で構成することで、風を受け流しつつ自然光を取り入れ、地中熱を活用した快適な空間をつくり出しています。

チリの建築事務所 ベンジャミン・ムルア・アーキテクツ（Benjamín Murúa Arquitectos）が設計した、砂漠という水や電気の供給が乏しい場所だからこそエネルギー効率を重視した建築です。

（以下、Benjamín Murúa Arquitectosから提供されたプレスキットのテキストの抄訳）

©︎ Cristóbal Correa

環境条件から形成する建築

アタカマ砂漠の標高2,900mの地点に位置するこのプロジェクトのデザインは、敷地の過酷な環境へ対応するためのものである。

高い日射量や風、砂塵や雪の嵐、暑さや寒さといった極端な環境条件にさらされるため、建物はこれらの条件に適応した設計とする必要があった。また、気候条件に適応しつつ効率的な設計とすることも課題となった。

©︎ Cristóbal Correa

©︎ Cristóbal Correa

特に雪の荷重と風の負荷により建物に大きな横荷重がかかり、過剰な構造が必要になるため、各階層ごとに2つの設計戦略を考案した。

1つは風への適応性を高めるため、空中の構造体や屋根の曲率を少なくすること、もう1つは建物のメインレベルを地下に埋めることである。

これらの戦略を組み合わせ、メインフロアの地下化と曲率の低い屋根により風の影響を低減しつつ、地熱エネルギーを活用した暖かい地下レベルをつくり出した。建物内部に蓄積される熱は、クロスベンチレーションにより放出している。

Plan

地下4.5mのスポーツエリアは965m²の楕円形の空間となっており、中央にバスケットボール、サッカー、バレーボール等に対応したスポーツ用のコートを配置した。

このメインフロアにはスポーツエリアの他にエクササイズマシンのあるジムエリアと、男女それぞれに用意した浴室・脱衣室、障害者用の浴室、授乳室、ゴミ処理室のあるサービスエリアがあり、それぞれが地上に通じるメイン通路に面している。プロジェクト全体の総面積は1,100m²となっている。

©︎ Cristóbal Correa

カテナリー曲線により最適化する集成材の木製トラス

〈アルマ・スポーツファシリティズ〉の地中の構造はRC造、屋根は木構造と2層の膜で構成した。

この軽量屋根はグルーラム集成材の木製トラスで構成されており、大スパンと空力的に必要な曲率を実現している。また、木製梁は自然な重力が形成する懸垂曲線を描くカテナリーアーチで構成されており、圧縮応力を最小限に抑えながら自らを支えている。

Model

©︎ Cristóbal Correa

スポーツのための快適な空間を生み出す二層の膜

木造構造の内側には、連続的な空間をつくり出しつつジムの熱的快適性を確保する保温性を有した第一の膜があり、外側には日射、風、雨などの気象条件から保護しつつスポーツ空間に影をつくり出す第二の膜がある。

それぞれの膜は双曲放物面、つまり反対方向に曲率をもつ形状とすることで、荷重は一方の軸には圧縮、他方の軸には引張をエッジに伝達する。

底面の周囲が水平の場合、エッジは圧縮と引張を吸収する必要があるが、エッジの梁を円弧形状とすることにより、これらの水平力をほとんど曲げることなくコーナーに伝達するしている。

Section

Section

膜構造にはメンテナンスの時間とコストを削減するため、たるみや張り直しの必要がないプレコントレント膜（Precontraint Membrane）を採用した。

この膜は標準的なPVDF膜の2倍の自然光透過率をほこりつつ、太陽エネルギーの透過を14％削減できるため、建物に自然光を導入しつつ外部の熱から保護することができる。

膜の耐用年数は30年以上であり、気象条件（雨、紫外線、熱、雪）によって生じる侵食に対して高い耐性をもつため、長寿命が期待されている。

©︎ Cristóbal Correa

砂漠という特殊な環境だからこそ重要なエネルギー効率

エネルギー効率化プロジェクトは2つの段階からなる。第一段階は、気候条件とパラメータを特徴付け、エネルギーコンセプトの提案を行う。第二段階では、建物に影響を与える特定の要因、例えば日射、日陰、伝導、浸透、換気などによる利得や損失を分析する。

エネルギー効率化の目的は、エネルギー消費を最適化することで、利用者の一定レベルの快適性を達成することにある。特にアタカマ砂漠のように、水や電気の供給が乏しい場所では、エネルギーロスを最小限に抑え、省エネを達成し、スポーツ空間における実際のニーズに合わせて消費量を調整する対策を実施することが重要である。

©︎ Cristóbal Correa

©︎ Cristóbal Correa

Elevation

Elevation

以下、Benjamín Murúa Arquitectosのリリース（英文）です。

ALMA SPORTS FACILITIES

SHAPING THE FORM ENVIRONMENTAL CONDITIONS

The design was a response to the whole environmental conditions founded during the development of the project. Located in Atacama Desert at 2900 masl, the project was influenced by extreme environmental conditions like high radiation, winds, dust and snow storms, heat and cold temperatures. The building had to be designed and adapted according to how this conditions could impact the form. Finally, is about the efficient design.

First it was considered that the weight of snow and the impact of wind forces over the structure could impact the building requiring an over structured building to avoid lateral deformations.

It was necessary to think in two design strategies for each one of the levels of the construction. The first one was to think the aerial structure or roofing with less curvature to improve their adaptation to wind blasts.

The second one is burying the main level locating the court underground to take advantage of geothermal energy.

Both strategies resulted in a concave form and continuous space with a warm comfort zone underground clearly differentiated of roof. Afterwards the curvature of roofing was reduced to make it more aerodynamic and obtain a better thermal comfort zone in the underground level, burying more the main place of building.

The accumulated heat inside the building could be released through a cross ventilation system that spreads it and, at the same time, separates the roof (that receives direct solar radiation) from the sports space.

MAIN LEVEL DESCRIPTION SPORTS SPACE

The sports area is composed by a main space with an oval shape of 965 m² of surface. This space includes an indoor sports court at the center, for sports such as basketball, soccer rand volleyball, mainly.

Towards the shorter edges of the oval plan there are sports exercise machines, and to the larger parts of the oval plan there are large seats around the concave wall.
The perimeter wall of the main level is projected to the outside until it reaches the surface.

Towards one side of the larger edge of the oval shape is the circulation. This connects the underground with the surface through a stair and a hallway which leads to an elevator.

Adjacent to the circulation is located de services area which has women bathroom and dressing room, man bathroom and dressing room, handicap bathroom, nursery room and garbage room. These spaces are articulated by a hallway.

The entire project includes the oval main level, circulation and services area. A total surface of 1,100 m².

PROJECT’S LAYERS STEREOTOMIC & TECTONIC

This project is composed by two principle strategies: Stereotomic and tectonic space. These two spaces are separate in eight different elements.

Stereotomic space:
First the underground, principal space for the gym. In the center it is placed the court and in the edges the sports exercise machines.
This level presents an oval form with 965 m² of surface and It is located 4,5 meters below ground level.
The principal space material is wood, the perimeter structure is concrete. This wall is opening as it rises to the surface.

In one side it is located the services areas. This works as an oval space attachment and contains the women ́s bathroom and dressing room, men ́s bathroom and dressing room, handicap bathroom, nursing room and garbage room. These all are connected by a hallway.

At the same side of services area, it is the circulation. The purpose of this zone is to generate an articulation that connects the underground level with the surface. The stair is the principal vertical connection and a lift is the secondary connection.

Over the exterior surface is the access and ventilation. The ventilation is a perimeter foundation of the roof. Its principal function is to generate a cross ventilated system. This foundation is the intersection between the surface and the main level.

The gym access is displayed as an attachment to the concavity of the roof. This sticks out from the ground with 15 m² of surface.

Tectonic space:
Located on the ventilation foundation, the gym has a light weight roof with concave shape, conformed by a wood structure and two membrane layers.

The roof is structured by beams of laminate wooden. This wooden trusses allows big lights and the curvature required for the roof.

Inside the wooden structure it is the first membrane which creates a continuous space that allows conserving the temperature to generate thermal comfort at the gym.

Towards the exterior of the wooden structure it is the second membrane, that is exposed to the environmental conditions of the place. Its main function is to protect from weather conditions such as radiation, wind and rain, besides generating shadow to the space destinated to sports activities.

STRUCTURE CATENARY & MEMBRANE

The structure of Alma sports facilities is composed of two different structures:

1. Catenary arcs: this corresponds with a bi-articulated system that supports itself, minimizing the compression effort, as a consequence of its mass being distributed uniformly, leaving this uniquely submitted to the forces of gravity. The horizontal compression is inversely proportional to the height of the arc.

The structure is design in wood elements covering an area of 900 m². Down this main floor there is a concrete underground.

2. Membrane: this membrane works with a system called surface active structure. This consist of a flexible surface, but resistant to traction, compression and shear forces, in which the transmission of forces is made trough the resistance of the surface, and it depends of the specific shape of this surface.

The membrane has to have a hyperbolic paraboloid shape with an opposite direction curve. This makes the loads to be transmitted to the edges as a result of the arc mechanism (compression force) in one of the axes and the suspension (traction) in the other one. If the perimeter is horizontal, the edge must absorb the conjunction of the compression and traction forces.

Because of its arc shape (hyperbolic), the edge beam transmits the horizontal effort to the corners almost without bending.

MEMBRANE SPECIFICATION PRECONTRAINT

The membrane has been chosen considering its particular characteristics.
In first place, it avoids re-tensioning and sagging, reducing maintenance and costs at the same time.

This type of membrane provides natural light for the facilities, as consequence of its translucency, which allows two times more natural light transmission than standard pvdf membranes. The membrane also grants protection from the outside heat, reducing to only 14% the transmission of solar energy to the interior space.

This membrane has a proven life expectancy of over 30 years. This kind of membrane is being used in major construction projects and in structures that are thought to be permanent. Therefore, it is expected from this type of membranes a long life, as a result of its design which is highly resistant to the erosion generated by weather conditions (rain, UV radiation, heat, snow).

ENERGETIC EFFICIENCY REDUCING LOSSES OF ENERGY

The energetic efficiency project is composed of two phases. The first one characterizes the climate and parameter conditions to make an energetic concept proposal.

The second phase analyzes the specific factors that impacts the building, such as solar radiation, shading, gains or losses of conduction, infiltrations and ventilations, between others.

The purpose of this project is to optimize the energetic consumption to bring comfort and reach a certain user friendly level. The aim is to implement actions to minimize the losses of energy, saving costs, and adapting the consumption to the real necessities of the sport space, especially in a place like Atacama Dessert where there is lack of water and electricity services.

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