從純結(jié)構(gòu)設(shè)計(jì)到自然結(jié)構(gòu)設(shè)計(jì)

金箱溫春

KANEBAKO Yoshiharu

1 東京工業(yè)大學(xué)

2 金箱結(jié)構(gòu)設(shè)計(jì)事務(wù)所

劉曉茜 LIU Xiaoqian/ 譯

郭屹民 GUO Yimin/ 校

1 概述

建筑設(shè)計(jì)與結(jié)構(gòu)工程的關(guān)系在任何時(shí)代都是至關(guān)重要的，結(jié)構(gòu)工程的發(fā)展離不開力學(xué)、計(jì)算機(jī)技術(shù)和建筑材料的支撐?，F(xiàn)代主義建筑在世界各地傳播的同時(shí)，結(jié)構(gòu)的合理性同樣也備受關(guān)注。以材料的特性及簡(jiǎn)單恰當(dāng)?shù)慕Y(jié)構(gòu)體系為出發(fā)點(diǎn)的設(shè)計(jì)方法，可以實(shí)現(xiàn)具有吸引力且結(jié)構(gòu)合理的建筑，我將其稱為“純結(jié)構(gòu)設(shè)計(jì)”。

隨著社會(huì)的發(fā)展，人們對(duì)建筑的需求變化促使建筑的形態(tài)和功能變得更加復(fù)雜。建筑結(jié)構(gòu)需要對(duì)這些需求做出回應(yīng)，在兼顧其力學(xué)合理性的同時(shí)更要發(fā)揮多樣性。這讓更復(fù)雜的結(jié)構(gòu)問題僅靠單純的結(jié)構(gòu)思維無法解決，需要運(yùn)用不同的結(jié)構(gòu)設(shè)計(jì)理念去創(chuàng)造超越純粹的、更為自然靈活的結(jié)構(gòu)，我將其稱為“自然結(jié)構(gòu)設(shè)計(jì)”。與純結(jié)構(gòu)設(shè)計(jì)不同，自然結(jié)構(gòu)設(shè)計(jì)是用合適的材料制作最有效的結(jié)構(gòu)框架來實(shí)現(xiàn)建筑形象。在這個(gè)概念中，材料和框架并不局限于一種類型，它們可以被充分地組合在建筑的每個(gè)部分，并且完全協(xié)調(diào)。

本文介紹了材料在兩種結(jié)構(gòu)設(shè)計(jì)中的不同使用方法。一種是使用單一材料的結(jié)構(gòu)設(shè)計(jì)，即純結(jié)構(gòu)設(shè)計(jì)；另一種是混合了多種材料和多種框架體系的結(jié)構(gòu)設(shè)計(jì)，自然結(jié)構(gòu)設(shè)計(jì)被蘊(yùn)含在這兩種設(shè)計(jì)方法中。下面以筆者參與設(shè)計(jì)的案例分別進(jìn)行詳細(xì)介紹。

2 純鋼筋混凝土結(jié)構(gòu)設(shè)計(jì)

混凝土、鋼材和木材是常見的結(jié)構(gòu)材料，它們具有不同的特點(diǎn)。首先，介紹鋼筋混凝土結(jié)構(gòu)的工程實(shí)例?；炷潦且环N耐用、結(jié)實(shí)的材料，可以構(gòu)成自由的結(jié)構(gòu)形式，所以經(jīng)常被用作有機(jī)結(jié)構(gòu)，如弧形屋頂。由于它不能抵抗拉伸應(yīng)力，因此設(shè)計(jì)師有時(shí)會(huì)采用預(yù)應(yīng)力的方法來控制混凝土的拉伸應(yīng)力。

“小松科學(xué)城”（Science Hills Komatsu，圖1）是一座有機(jī)建筑，是位于日本地方城市的科學(xué)博物館。建筑設(shè)計(jì)的主題是與景觀融合，四排覆蓋著綠色的連續(xù)曲面從地面升起，人們可以在屋頂周圍漫步。建筑結(jié)構(gòu)復(fù)雜，包括展覽空間、活動(dòng)大廳、圓頂劇場(chǎng)和實(shí)驗(yàn)室多個(gè)功能空間，彎曲的屋頂在多個(gè)房間內(nèi)被呈現(xiàn)（圖2）。

由于軸向力占主導(dǎo)地位，曲面屋頂結(jié)構(gòu)在力學(xué)上是合理的。但是，建筑師要求的低曲率導(dǎo)致了彎曲屋頂?shù)膫?cè)向推力巨大。此外，建筑樁基不允許破壞地下既有的古代遺跡。于是我在跨中用鋼梁來支撐屋頂，基礎(chǔ)采用直接基礎(chǔ)而不是樁基，從而解決低層屋頂和地基的問題。由于屋頂結(jié)構(gòu)為殼體和平板組合的體系，屋頂采用圓柱形和圓錐形組合的形式來考慮鋼筋混凝土的施工，平板采用彎曲平板和球空板，厚度為300～375mm，由跨度中間的薄鋼柱支撐，其間距約為7～9m（圖3）。連續(xù)的曲面屋頂，最終以一種新的景觀呈現(xiàn)出來。

1 小松科學(xué)城

2 小松科學(xué)城內(nèi)部連續(xù)的曲面屋頂

3 小松科學(xué)城屋頂施工

4 小松科學(xué)城混凝土螺旋樓梯

5 企鵝館水池

6 企鵝館水池樓梯結(jié)構(gòu)受力分析

7 兒童博物館

8 兒童博物館內(nèi)部結(jié)構(gòu)

9 兒童博物館鋼框架結(jié)構(gòu)示意

10 兒童博物館柱與水平桁架的連接

在博物館大廳有一個(gè)混凝土螺旋樓梯（圖4），總直徑為10m，當(dāng)螺旋樓梯直徑較小時(shí)，應(yīng)力主要集中在軸面上，結(jié)構(gòu)簡(jiǎn)單。但該樓梯不僅涉及豎向彎矩，而且涉及水平彎矩。建筑師要求采用薄型混凝土結(jié)構(gòu)，普通結(jié)構(gòu)體系不能實(shí)現(xiàn)樓梯的細(xì)長(zhǎng)形態(tài)，還需要抵抗拉力。這個(gè)樓梯的結(jié)構(gòu)類似于在倫敦由奧雅納（Ove Arup）設(shè)計(jì)的“企鵝館水池”（圖5），但有著更大的體量，必須通過新的手段加以解決。最終我們采用后張預(yù)應(yīng)力法，使混凝土厚度達(dá)到30cm，其結(jié)構(gòu)的水平彎矩和預(yù)應(yīng)力索布置如圖6所示。

3 純鋼結(jié)構(gòu)設(shè)計(jì)

鋼結(jié)構(gòu)建筑中，鋼通常用作軸心構(gòu)件，組合柱、梁和對(duì)角支撐。當(dāng)結(jié)構(gòu)系統(tǒng)以軸向應(yīng)力為主，承受豎向荷載或地震荷載時(shí)，鋼結(jié)構(gòu)系統(tǒng)是最合理的。而當(dāng)使用薄鋼構(gòu)件時(shí)，如何限制屈曲是重中之重。

圖7是一個(gè)兒童博物館，外墻覆蓋著玻璃幕墻。為了將立面透明化，將其主要結(jié)構(gòu)設(shè)置在建筑內(nèi)部（圖8），并將鋼框架放置在建筑周圍（圖9）。部分鋼柱放置在建筑周邊，其他柱呈對(duì)角線布置。地震荷載由斜柱抵抗，因此所有柱均能通過軸力抵抗豎向荷載和水平荷載。立柱采用直徑300mm的鋼管，由于中庭高20m，該區(qū)域的立柱太長(zhǎng)，不易屈曲，因此使用水平桁架來加強(qiáng)柱的屈曲強(qiáng)度。同時(shí)，柱與水平桁架的連接構(gòu)件設(shè)計(jì)為不交叉的形式（圖10）。

11 某高中體育館

12 某高中體育館室內(nèi)

13 某高中體育館網(wǎng)架結(jié)構(gòu)

14 某高中體育館屋頂四角布置V 形鋼柱

圖11 是一個(gè)高中體育館，一層為鋼筋混凝土結(jié)構(gòu)，二層上部為鋼結(jié)構(gòu)，屋頂尺寸為33.6m×39.6m。附近現(xiàn)有建筑物的存在使得體育館的布置受到了限制，為了避免相互干擾，平面不得不切出一個(gè)角（圖12）。我們?cè)O(shè)計(jì)了一個(gè)底部為八角形、頂部為矩形的臺(tái)形屋頂，將雙層桁架結(jié)構(gòu)和單層網(wǎng)架結(jié)構(gòu)相結(jié)合。屋頂高2.0～2.8m，采用雙層交叉弦桁架結(jié)構(gòu)，125mm×125mm的上下弦桿件及各節(jié)點(diǎn)之間用直徑101.6mm的管子連接，網(wǎng)架在上下弦桿件間提供屈曲加勁效果。

此外，網(wǎng)架還和上弦桿件構(gòu)成四邊形金字塔，負(fù)責(zé)增強(qiáng)面內(nèi)的剛度（圖13）。在周邊區(qū)域，受水平推力的限制，屋頂采用單層網(wǎng)架結(jié)構(gòu)。在抗震設(shè)計(jì)方面，V形鋼柱布置在二層的四個(gè)角落，在豎向荷載的作用下抵抗水平荷載（圖14）。由于構(gòu)件主要承受軸向力，因此構(gòu)件的尺寸較小，實(shí)現(xiàn)了透明的效果。

4 純木結(jié)構(gòu)設(shè)計(jì)

木結(jié)構(gòu)在日本古代被廣泛使用，但是在20世紀(jì)，由于防火原因，大型建筑已不能使用木結(jié)構(gòu)。近年來，為了促進(jìn)生態(tài)，木結(jié)構(gòu)被允許用于大型建筑物。與鋼筋混凝土或鋼結(jié)構(gòu)相比，木結(jié)構(gòu)的特點(diǎn)是重量輕、接縫薄且構(gòu)件尺寸較小。由于木結(jié)構(gòu)很難達(dá)到剛性框架的要求，因此需要放置剪力墻或支撐構(gòu)件以進(jìn)行抗震設(shè)計(jì)。木結(jié)構(gòu)的材料和結(jié)構(gòu)系統(tǒng)有很多種，最常見的一種是通過小尺寸構(gòu)件的組合疊加來實(shí)現(xiàn)。

圖15是一座藝術(shù)博物館遺址中的木制拱廊，拱形結(jié)構(gòu)的跨度為9m，主拱構(gòu)件為9cm×9cm的膠合木。圖16是一個(gè)村莊的社區(qū)中心，抗震墻在平面上平衡布置，面向廣場(chǎng)設(shè)有6m×18m的多功能空間。屋頂結(jié)構(gòu)的建筑形象就像日本的老房子，以小尺寸構(gòu)件集結(jié)而成，構(gòu)件尺寸為120mm×180mm～120mm×300mm，用粘合膠相連（圖17）。圖18是一座小型教堂，尺寸為9m×9m，高度為9m。建筑最重要的是滿足安靜和光線的需求，外墻采用雙層設(shè)計(jì)，覆蓋木材薄片，以減少城市的噪音。陽光從頂部照射進(jìn)來，穿過雙層墻進(jìn)入房間，為了遮擋光線，屋頂和墻壁的構(gòu)件尺寸被設(shè)計(jì)得盡可能?。▓D19）。墻壁由兩列圓柱組成，尺寸為9cm×9cm，屋頂采用桁架結(jié)構(gòu)，繩索構(gòu)件為12cm×18cm，角部構(gòu)件為4.4cm×9cm和9cm×9cm（圖20）。

5 混合多種材料和多種框架體系的結(jié)構(gòu)設(shè)計(jì)

純結(jié)構(gòu)設(shè)計(jì)不適用于復(fù)雜性的建筑，從廣義的角度來看，復(fù)雜性建筑的結(jié)構(gòu)體系更加自由和靈活，它的結(jié)構(gòu)材料和框架體系并不局限于一種類型，需要選擇恰當(dāng)?shù)牟牧虾涂蚣荏w系組合在建筑的每個(gè)部分。但這并不等于無限自由，這些材料和框架體系既要滿足動(dòng)力學(xué)的合理性，又要實(shí)現(xiàn)整體的協(xié)調(diào)性。

15 某藝術(shù)博物館遺址中的木制拱廊

16 某村莊的社區(qū)中心

17 某村莊的社區(qū)中心屋頂木結(jié)構(gòu)

18 某小型教堂

19 某小型教堂室內(nèi)

20 某小型教堂純木結(jié)構(gòu)

圖21是一個(gè)初中的體育館，平面形狀為橢圓形，長(zhǎng)軸67m、短軸43m。屋頂采用斜網(wǎng)格木殼膜結(jié)構(gòu)，墻面也采用斜網(wǎng)格木結(jié)構(gòu)。但由于這座體育館的高度較低，而且由薄弱的木結(jié)構(gòu)支撐，無法抵抗拱的推力，因此薄膜結(jié)構(gòu)不可能實(shí)現(xiàn)。如果這座建筑是用木桁架結(jié)構(gòu)建造的，那就不需要薄膜結(jié)構(gòu)了。為了實(shí)現(xiàn)建筑形象，結(jié)構(gòu)設(shè)計(jì)了木材和懸索組合系統(tǒng)（圖22）。上部拉索與膠合木橫梁呈對(duì)角線形式，下部拉索、拉力懸索一起與上部拉索呈對(duì)角線設(shè)置。頂梁的高度為140cm，但懸索的直徑只有48mm。屋頂梁端部采用鋼接頭，將懸索與接頭連接（圖23），頂梁和立柱的連接構(gòu)件均采用鋼管。建筑采用了木結(jié)構(gòu)和鋼結(jié)構(gòu)組合的方式，但當(dāng)人們看到這個(gè)屋頂時(shí)，會(huì)感覺到是一個(gè)由木質(zhì)膜結(jié)構(gòu)構(gòu)成的空間（圖24）。如果僅用木結(jié)構(gòu)來設(shè)計(jì)的話，則達(dá)不到這樣的效果。

圖25是日本當(dāng)?shù)氐囊蛔y泥博物館，紋泥是在湖底沉積了70萬年的淤泥，能夠反映此地過去的天氣和氣候狀況，該建筑用于展覽和研究紋泥。建筑整體呈帶狀，長(zhǎng)76m、寬9.6m，屋頂材料采用了業(yè)主要求的當(dāng)?shù)啬静摹Ｒ粚訛榇筇煤椭型?，與景觀融為一體；二層為展示空間，一面鋼筋混凝土墻將二層的空間寬度劃分為6.4m和3.2m（圖26）。圖27展示了建筑的結(jié)構(gòu)系統(tǒng)和材料，木屋頂由梁和膠合板組成，鋼構(gòu)件由梁、斜構(gòu)件、柱等組成，鋼筋混凝土墻和樓板由預(yù)應(yīng)力梁支撐。建筑屋面為組合結(jié)構(gòu)，木結(jié)構(gòu)布置簡(jiǎn)單方便，復(fù)雜部分采用鋼構(gòu)件（圖28）。建筑一層為鋼筋混凝土結(jié)構(gòu)，采用兩列張拉梁，兩側(cè)布置懸臂板。

圖29是一個(gè)自然公園的游泳池，其構(gòu)思是將公園的路徑置于水池之上，使其“漂浮”在上面。這條路徑原本就存在于公園中，在游泳池建好后，路徑的位置沒有改變，所以這條路穿過了游泳池空間（圖30）。考慮到建筑的結(jié)構(gòu)，將建筑的形狀設(shè)計(jì)為一個(gè)圓柱體，上層較寬，底部直徑約34m。屋頂為雙層膜結(jié)構(gòu)，柔和的陽光可以透過薄膜滲透進(jìn)來。

考慮到建筑每個(gè)部分的結(jié)構(gòu)受力，設(shè)計(jì)篩選最有效的材料和結(jié)構(gòu)系統(tǒng)。對(duì)這個(gè)建筑來說最重要的功能是這條路徑，結(jié)構(gòu)設(shè)計(jì)由此而開始。設(shè)計(jì)計(jì)劃為該路徑制作30cm厚的鋼筋混凝土空心板，并由鋼構(gòu)件懸掛，形似豎框，所以看上去感覺像是漂浮的（圖31，32）。大尺度的鋼桁架作為龍骨支撐著通道，被放置在通道上方。建筑的外墻為鋼筋混凝土墻體結(jié)構(gòu)，鋼桁架與鋼筋混凝土外墻的連接部分采用鋼筋混凝土結(jié)構(gòu)，并向外延伸。屋頂分為兩個(gè)半圓形，由鋼桁架和周邊鋼筋混凝土結(jié)構(gòu)支撐，形成單向桁架體系。該結(jié)構(gòu)在建設(shè)完成后是不可見的，每個(gè)結(jié)構(gòu)構(gòu)件都由最有效的材料和結(jié)構(gòu)體系構(gòu)成，并且所有構(gòu)件形成了整體系統(tǒng)上的和諧。

21 某初中體育館

22 某初中體育館木材與懸索的組合結(jié)構(gòu)

23 某初中體育館懸索、梁、立柱采用鋼接頭

24 某初中體育館屋頂是木質(zhì)膜結(jié)構(gòu)

25 紋泥博物館

26 紋泥博物館二層展示空間

28 紋泥博物館屋頂為木結(jié)構(gòu)與鋼結(jié)構(gòu)的組合

29 某自然公園的游泳池

30 某自然公園的路徑穿過游泳池

31 某自然公園的游泳池鋼桁架支撐通道

32 某自然公園的游泳池結(jié)構(gòu)系統(tǒng)

6 結(jié)語

在一個(gè)項(xiàng)目建成后，結(jié)構(gòu)的可見性是不同。無論結(jié)構(gòu)是否能被看到，結(jié)構(gòu)的設(shè)計(jì)理念在任何情況下都是一樣的，因?yàn)榻Y(jié)構(gòu)設(shè)計(jì)需要平衡包括力學(xué)、建筑設(shè)計(jì)、建筑功能和經(jīng)濟(jì)等多個(gè)條件。純結(jié)構(gòu)設(shè)計(jì)由于其設(shè)計(jì)的局限性，在近年來復(fù)雜的項(xiàng)目中很少應(yīng)用，而包含純結(jié)構(gòu)設(shè)計(jì)的自然結(jié)構(gòu)設(shè)計(jì)將是最有效的設(shè)計(jì)方法。

Introduction

Relationship between architectural design and structural engineering has been important at any age.Building structure has been supported by establishment of dynamic,growth of computer technology and development of structural materials.When modernism architectures spread around the world,the rationality of structure was purchased at the same time.As a simple solution,it is available to apply features of materials and to use a simple adequate structure system.A lot of attractive architectures that were based on dynamics rationality were realized according to this philosophy.I call this method “pure structural design”.

According to development of society,the demand for architecture has been changed,shape of buildings became complicated and function of architecture became complex.The building structure was needed to respond to those demands and to be requested considering depend on not dynamical rationality but multi standpoint.The considering problem of structure is complicated,so it cannot be solved by pure structural thinking,A different structural design concept should be needed; it has naturally and flexibility beyond pure.I call it “natural structural design”.Natural is different pure,natural structural design is making the most efficient frames with suitable materials to satisfy architectural image.In this concept,material and frame system do not restrict one type,adequate materials or frame systems are combined at each part of the building,and they are harmonized totally.

In this paper,two different approaching methods to use materials in structural design are introduced.One is the structural design used by single material purely,as it is called pure structural design.Another is the structural design mixed several materials and several frame systems.Natural structural design is included in both design methods.All introduced projects are designed by the author.

Structural Design used by Reinforced Concrete Purely

Concrete,steel and wood are mainly used as structure material,and they have different characteristic.At first,some projects used RC structure are introduced.Concrete is continuous material and has advantages to make a free form,so it is often used in organic structure such as curved roof.Because it is not able to resist tensile stress,sometimes prestress method is used to control tensile stress.

Photo.1 is an organically configured architecture named Science Hills Komatsu; a science museum located in a local city of Japan.The architectural design was themed on fusion with the landscape.There are four rows of curved roofs,which are continuous shape from the ground level to the roof and covered with green.People can walk around on the roofs and under the roofs.The building is a complex architecture,which includes exhibit spaces,event hall,dome theater and laboratories.The curved roof is appeared inside the several rooms (Photo.2).

Because axial force is dominant,the curved roof structure is rational as dynamics.But the curvature the architect requested was small,in that case the thrust of the curved roof is bigger.Also,the pile foundation was not allowed to existent of the ancient remains under the ground.So,I designed to support the roof by steel beams at the midspan,and the foundation is used direct foundation instead of pile.I solved the problem of the low-rise roof and the foundation.As the result the roof structure is shell and flat slab combined system.The roof shape was used a geometrical shape,combination of cylindrical and conical form to consider construction of reinforced concrete.The slab was used as curved flat slab and ball void slab,thickness is 300 to 375 mm and it is supported in the midspan by thin steel columns placed at a pitch of about 7 to 9m (Photo.3).The figure of continuous curved roof became a new landscape.

Photo.4 is a concrete spiral stair placed in the lobby space of a museum.The plenary diameter of stair is 10m.When the diameter of spiral stair is small,the dominant stress is axial face and structure is simple.But in this project not only vertical bending moment but horizontal moment is influenced.The architect requested slim concrete structure.It was not able to realize to slim structure to apply normal structural system,so it is needed to resist tensile force.The structure of this stair is similar to the Penguin pool in London designed by Ove Arup(Photo.5).But the scale is bigger than the Penguin pool,any idea was needed in this project.The post-tensioning prestress method is arranged to make thickness of concrete as 30cm.The horizontal moment occurred in this structure,the arrangement of prestressed cable was used so as shown in Photo.6.

Structural Design used by Steel Purely

Secondary,projects made by steel structure are introduced.Steel is normally used as axis member,combined column,beam and diagonal bracing.Especially when the structural system is mainly dominant as axial stress for vertical load or seismic load,system is most rational.On the other hand,when the thin steel member is used,how to restrict against buckling is an important problem.

Photo.7 is a children’s museum,which outer wall is covered with glass facade.To realize transparent facade,the structural cores are placed inside of the building (Photo.8) and steel flames are placed around building (Photo.9).Some steel columns are placed at the perimeter are placed vertically,and other columns are placed diagonally.Earthquake load is resisted by diagonal columns; therefore,all column resists vertical load and lateral load by axial force.The columns are used pipe,with diameter of 300mm.The height of the atrium is 20m,the column of this part is too long to be weak on buckling.Horizontal truss is placed to stiffen the buckling strength of the column.The connection of column and horizontal truss is designed as not to cross each member (Photo.10).

Photo.11 is a gymnasium of high school,which has the roof dimensions of 33.6m x 39.6m.There are already some existing buildings nearby,so the building placement was restricted and the plan had to cut a corner in order to avoid interference with the existing building (Photo.12).First floor is RC structure and the upper part of second floor is steel structure.A frustum-shaped roof with an octagonal bottom and a rectangular top was designed.The feature of this structure is combination of double layer truss and single-layer lattice structure.The top roof with a depth of 2.0m to 2.8m is composed of a double-layered structure of crossing chord truss in which H-125x125 upper and lower chords and each node are connected by 101.6mm diameter pipe as presented in Figure 6.The lattices provide a buckling stiffening effect on the upper and lower chords.Moreover,the lattices and the upper chords constitute the quadrangular pyramid which is responsible for enhancing the in-plane stiffens (Photo.11).At the perimeter zone of the roof,the pipe member is used for single lattice structure,and thrust is restricted by the horizontal members.

In the seismic design aspect,the VVV-shaped steel columns are arranged at the four corners on the second floor and resist lateral load with vertical load (Photo.13,14).Because the dominant force of members is axial,the size of members is small and the image of transparency was realized.

Structural Design used by Wooden Purely

Thirdly,projects made by wood are introduced.Wooden structure was widely used in Japan from the old era,but at 20 century large scale buildings could not be made with wooden structure for reasons of fire protection.Recently wooden structure is recognized and adopted for large scale buildings in order to contribute to ecology.The characteristics of wood are that weight is light,joint is weak and member size is relatively small compared with reinforced concrete or steel.Because it is difficult to make rigid frame,shear wall or bracing member are needed to place for earthquake resistant design.There are many kinds of wooden materials and structural systems.One useful method is accumulating small members.

Photo.15 is a wooden arcade at the site of an art museum,which is 9m spanning vault-shaped structure.It is simple and pure arch structure.The main arch member is 9cm x 9cm used glue-laminated wood.

Photo.16 is a community centre in a local village.Some seismic resistant wall is placed in planarly balance,and there is a multi-purpose space size as 6m x 18m face to the plaza.The architectural image of roof structure is like an old Japanese house,to accumulate with small size members.The size of member is 120mm x180mm to 120mm x 300mm used with glue-laminated wood and timber(Photo.17).

Photo.18 is a small church,which has a plenary size as 9m x 9m and height as 9m.The important architectural function of this project is silence and light.The outer wall is planned as double,the outside wall is covered plywood panel to cut the sound of the town.The sunlight comes from the top light and intrude through the double-wall to the room.To intrude the light the member size of roof and wall was planned to make small as possible (Photo.19).The wall consists two lines of columns,which size is 9cm x 9cm,and the roof is used truss structure.The cord member is 12cm x 18cm and diagonal member is 4.4cm x 9cm and 9cm x 9cm (Photo.20).

Structural Design Mixed Several Materials and Several Frame Systems

Pure structural design is limited to apply architectural complexity.On a wide standpoint,the structural system is freer and more flexible.Structural material and frame system do not restrict one type,adequate materials or frame systems are combined at each part of the building.But it is not limitless freely.It is needed to satisfy rational dynamics and to harmonize totally.

Photo.21 is a gymnasium of a junior high school.The plane shape of the gymnasium is an oval,which has 67m by 43m length at each direction.The roof was imaged wooden membrane structure using diagonal grid,and the wall was imaged wooden diagonal structure.But because this gymnasium had a low rise and it was supported by weak wooden structure,the thrust of arch was not resisted and membrane structure was not possible.If this building is made with only wood truss structure is needed,and it was not felt membrane structure.To realize architectural image the combination system wood and cable was plan to arrangement (Photo.22).The upper cord is used with glulam beams and placed diagonally,and the lower cord is used with tension cables placed diagonally as same the upper cord.The roof beams have 140cm in height,but the size of tension cable is only 48mm in diameter.The end of the roof beam was used the steel joint,the tension cable was connected to the joint (Photo.23).The connection member of the roof beams and the columns were used steel pipes.

This structure is combination of wood and steel,but when people look at this roof,they feel a space made by wooden membrane structure (Photo.24).If the structure was designed with only wood,the light image could not be realized.

Photo.25 is a museum of varve at the local city in Japan.Varve is an accumulated mud at the bottom of a lake for 700 thousand years,which shows the state of weather and climate condition in the past time.The building is used for exhibition and research of the varve.So,the shape of the building is belt shape which has width as 9.6m and length as 76m.Material of the roof is used wood of the local area requested by the client.Second floor is used for exhibition space,and there is RC wall in the center,which divide space as 6.4m and 3.2m.First floor is used for lobby and pilotis which is unified with landscape (Photo.26).

Photo.27 shows the structural system and material.The wooden roof is composed of beam and plywood panel.Steel members are composed of beam,diagonal member and column.Steel members are small members.RC wall and slab are supported by prestressed beams.The structure of roof is composite structure.Arrangement of wooden structure is simple and easy; the complicated part is used with steel member (Photo.28).Complicated details are used only steel members.

The structural design of the first story is RC structure:2 lines of tensioning beams are placed,and cantilever slabs are placed at the both sides.

Photo.29 is a swimming pool in a natural park.The architectural concept of this building is that the pathway placed above the pool as like floating.There was the pathway in the park previous time.One day the swimming pool was constructed,but the pathway remains as before,so the pathway penetrated through in the large pool space.It is the story based architectural concept.The shape of building is a cylinder wider at the upper level (Photo.30),and the diameter is about 34m at the bottom.The roof is double-membrane structure,the soft sunlight intrudes through the membrane.

I thought about structural system at each part applying the most effective materials and structural system.The most important function as architectural design is the pathway,so structural design was beginning to arrange this part.The pathway was planned to make reinforced concrete void slab,30 cm thickness.The slab is hanged by steel members who look like mullion,so pathway is felt like floating (Photo.31,32).The big scale steel truss as keel truss,which supports the pathway is placed above the pathway On the other hand,the outer wall of the building is made with reinforced concrete wall structure.The connection part of steel truss and outer RC wall is made with steel reinforced concrete (SRC) structure,and it extends outside of the cylindrical building.The roof is divided into two semicircular shape parts; each part is supported steel truss and perimeter RC structure,so a oneway truss system is available.

This structure is not visible after completion.But each structural component is used the most effective materials and structural system,and all components keep harmony of the system.

Conclusion

Structure is sometimes appeared and sometimes disappeared after completion.Appear or disappear is not an important thing,and philosophy of structural design is same at any situation.Structural design is needed a balance among several conditions of the project,about dynamics,architectural design,architectural function and economy et.Pure structural design has limitation of design,and it is not available about complex architecture recently.Natural structural design which includes pure structural design would be effective methods.