Valuable space with functionality plus alpha|Good relationship between membrane structure and station

通路や壁、梁に木材が使われ、柔らかな光が降り注ぐ。半世紀ぶりの山手線新駅となった高輪ゲートウェイ駅※は、都心にありながらどこかゆったりとした時の流れを感じさせる駅です。
約4000㎡のトラス構造屋根に使われているのは光触媒膜。建築家の隈研吾氏はこの膜を和紙に見立て、外側にはいくつもの折り目をつくり「折り紙」を、天板から透けた光が見える内側は「障子」をイメージしたそうです。
ともすれば無機質になりがちな鉄道駅に膜構造を用いることで、日本ならではの「優しさ」、「もてなし」を表現する。膜構造はその機能性だけにとどまらず、プラスαの価値を駅という空間に生み出します。

※高輪ゲートウェイ駅
・　施主　：　東日本旅客鉄道株式会社
・　設計　：　株式会社　ジェイアール東日本建築設計事務所
隈研吾建築都市設計事務所（デザイン監修）
・　元請　：　大林組・鉄建建設ＪＶ

What Bright Stations Bring

Diffused soft light is taken into the entire station as if it were enveloped. Membrane structures are attracting increasing attention in new construction and renovation of stations as a building material that provides an overwhelming sense of openness and a bright, comfortable space. On the other hand, we have received some concerns about membrane materials in terms of durability, maintenance, and heat. What role can membrane structures play in the future of train stations and urban development centered on train stations? We answer these concerns by taking a look at the high affinity between membranes and stations.

Utilizing and Controlling Light Moderately: Spatial Staging Made Possible by a Membrane Structure

One of the main characteristics of membrane construction is its high light transmittance. The maximum illuminance of a membrane roof is 16,000 lx, which is overwhelmingly brighter than metal, slate, and other materials. During the day, natural light is utilized to brighten the platform and concourse, contributing to reduced lighting and air conditioning costs. The bright interior space also makes it easier to understand transit and exit lines, greatly improving convenience for customers, including the elderly.

At night, on the other hand, the interior lighting conversely passes through the membrane. The entire station appears symbolic, like an object emitting soft light, creating a completely different impression than during the daytime, another feature of the membrane structure. The shape plus light creates a comfortable space by bringing abundant natural light into the space, and at night it becomes a colorful presence in the city with its lighting effect. The spatial presentation made possible by a membrane structure that maximizes and moderately controls light greatly expands the possibilities of station space design.

Allows light to pass through and reflects heat, creating a comfortable space with minimal temperature increase.

その透光性能の高さから膜構造には日中の温度上昇を懸念する声をいただくこともあります。しかし太陽工業の光触媒膜材の日射反射率は約80％。光は通しても熱は通さない素材です。高い日射反射性能によって屋根裏の温度は金属屋根に比べて※９℃も低くなり、この熱吸収率の低さによって屋根元の床面温度（プラットフォーム）は金属屋根に比べて1.5℃、平均放射温度も３℃ほど低くなることが確認されています。（※メーカー計測値による）

これらは照明や空調コスト寄与するのはもちろん、近年大きな問題となっている夏場の熱中症対策にも大きな効果を発揮します。

＜Lightweight and high seismic performance to minimize secondary damage

地震大国日本において、建物の耐震性能は安心・安全の重要な要素です。特に多くの人が日々行き交う駅においては、万一の災害に備えて万全の体制が求められます。

地震の振動エネルギーは建物の重量に比例して大きくなります。膜構造は通常の建築素材に比べてはるかに軽量なため、揺れに対する負荷が少なく、特徴である柔軟性は揺れによる変形に追従するため柱への負荷も大きく軽減します。これによって地震による屋根落下などの危険性を減少でき、万一、破断した場合もガラス・金属等に比べ飛散しにくい素材のため、高い安全性を確保できます。また災害時の避難経路も確実に確保でき、利用者の安全な避難誘導が可能となるため二次被害の危険性も大幅に軽減できます。

Engineering service life of 50 years Self-cleaning function removes dirt

The durability of membrane materials varies depending on the type, but they all have a very long life span of 15 to 30 years. In the United States, some buildings have been in use for more than 30 years, and in Japan, the membrane material used in the Tokyo Dome has been in use since its opening in 1988, without being replaced once. According to engineering data, the membrane material can be expected to have a practical service life of 50 years. This high durability reduces the frequency of renovation work and greatly reduces the burden on the users of the facility.

In addition, the titanium dioxide photocatalytic membrane chemically decomposes and removes dirt adhering to the surface through its self-cleaning function. The photocatalytic decomposition function works not only on the open part of the roof but also on the reverse side, thus significantly reducing cleaning and other maintenance costs. Photocatalytic particles are integrated with the membrane material and do not deteriorate over time, so the effect is semi-permanent.

 

Photocatalytic Membrane Material with Self-Cleaning and Low Maintenance Costs

＜Titanium dioxide photocatalyst film adsorbs and decomposes NOx.

Nitrogen oxides (NOx) are one of the main causes of air pollution. High concentrations of nitrogen dioxide (NO2), which is mainly contained in automobile exhaust gases, have adverse effects on human respiratory tracts, making the reduction of nitrogen dioxide a major challenge. The most common measures to reduce nitrogen dioxide include building wall and rooftop greening using the absorption and adsorption capabilities of plants, and the maintenance of street trees, but the cost and area required for such measures are not always sufficient in urban areas. Under such circumstances, titanium dioxide photocatalytic membranes are attracting attention as a building material that contributes to environmental measures. Titanium dioxide photocatalytic membranes have the ability to adsorb, decompose, and remove nitrogen oxides contained in exhaust gas. Since sulfate ions are water soluble, they react with moisture in the air to form nitric acid (HNO3), which is then washed away by rain. The amount of HNO3 produced is so small that it has no effect on the soil. In other words, the use of titanium dioxide photocatalytic membranes on station roofs, eaves, station plazas, etc. has the same effect as greening. Titanium dioxide photocatalytic membranes, with their decomposition and removal functions, will make it possible to realize a “station that improves the environment.

summary

Lightweight, translucent, heat shielding, earthquake resistant, self-cleaning, and environmental performance. Membrane structures have a high affinity with stations, which are public spaces that require not only a high level of safety and security, but also convenience and comfort to satisfy many people.

The value of membrane structures as architectural materials has been enhanced by the experience and knowledge we have gained through our repeated efforts to devise, improve, and refine membrane structures in response to requests from architects, clients, and others who have asked us what they can do and what they want to achieve.

What can membrane structures do for future stations? How can we respond to what is required? We will continue to pursue the possibilities of membrane structures so that we can stay one step ahead of your voices and requests.

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