悉尼國際體育中心

悉尼國際體育中心從設計到施工均由澳大利亞人完成，是鋼結構設計和工程實踐的范例。鋼結構的成功運用代表了澳大利亞在鋼結構方面成就。這個出色的鋼結構體育建筑，已在2000年吸引了全世界的目光。

結構的設計主旨是把體育中心融合到場地環境中。鋼材可以在大型結構中保持最小的聯結點，不僅滿足結構需要，也能滿足美學需要。曲面屋頂和看臺的優美曲線表現出澳大利亞早期的“黃金時代”。

從設計到施工，各方面都滲透著創新精神，尤其是屋面系統。大看臺的屋面系統與傳統形式非常不同，輕質屋面通過鋼纜網懸掛在45m高的鋼桅桿上。桅桿支持著屋面前部，各桅桿的六個傾斜前支柱把向下的荷載從鉚接在桅桿上帶有兩個后支柱的椽子上傳遞到地面。

鋼桅桿可承擔350t荷載，并保持輕巧外形。與采用7個交錯式桅桿結構方案相比，由預張力高強度桿加強的4個鋼管構成的核心既能滿足美學上的要求，又能滿足經濟上的要求。

鋼桅桿完全在車間中制造組裝，這樣加快了安裝速度并提高了場地安全。前桅支索裝配前已系到桅桿上。構件組裝前的全面檢測和計算機分析顯示鋼纜的最終位置與預計位置相差不超過25mm。屋面在地面預先組裝好，包括屋面梁、屋面系統和天花板、線纜和燈具，而后吊裝到位，不需搭建腳手架。

各桅桿基座上的200m長懸索連接到前支柱上，以抵消風的升力。前支柱加入預張力以減小前支柱因自重而下垂。屋面支撐鋼桅桿可以安裝泛光燈，使此方案的經濟性大大提高，場地的兩個照明結構可以取消。

鋼纜支撐屋面系統的獨特之處是屋面向前傾斜，從前沿排水，為觀眾和官員提供了最大的遮蔽。

屋面的彈性變形模型在莫納什大學進行了風洞試驗，以準確確定風荷載和檢測屋面的動態變化。風洞試驗得到了一個不尋常結果，可以用一個獨特的鋼纜結構承擔，而不需很大的投資。

由于鋼纜的下垂作用，屋面試驗的動態分析較為復雜，需同時加載結構的自然頻率。

在整個設計階段應用了藝術工程設計和計算機分析。開發了一個專用計算機程序，用于確定在特定前支柱預張力的作用下鋼纜系統的形狀和計算鋼纜的下垂和總鋼纜用量。非線性分析被應用到確定因安裝屋面導致的結構幾何形狀的累積變化上。

結構的耐久性是設計的主要考慮方面，因而開發了一套噴涂系統，鑄件完全鍍鋅，并且設計了一整套自排水和清潔系統，以降低積塵和雨水沖刷。暴露在外的鋼結構盡量使用封閉截面的構件，如盒形或桶形，以便于雨水把積塵沖走，并且能減少鳥獸的棲息地。

決定采用鋼纜支撐系統經過了廣泛的調查，并考察了各種屋面的方案，以及如何有效處理下列問題；結構的效率、投資的效率、美學因素、造型、可建性、用戶友好性、環境影響和耐久性。

（水潤宇譯）

Totally designed, engineered, constructed and developed in Australia by Australians, the Sydney International Athletic Centre is an extraordinary example of innovation and invention in steel design and engineering practice.An ingenious solution to a difficult problem, the use of steel elements throughout the Athletic Centre has provided the people of Australia with a truly remarkable grandstand building.This use of steel has confirmed the appropriateness of the material for a high profile project;a steel structure on which the eyes of the world will be cast come the year 2000. A major design theme flowing through the structure was that the Centre integrate into the landscape and recognise existing landforms.The earth is mounded and modelled to respond to these needs which the built form is designed to grow out of and complement.Steel was specified for its ability to be easily moulded with even the smallest connection examined in great detail to ensure that it not only satisfied strength requirements but fulfilled aesthetic requirements.The catenary cables of the Athletic Centre are in counterpoise to the curved roof and grandstand which are natural extension of the curved berm forming the arena.Paved areas meander between parts of the facility in graceful curves reflecting the earliest images of Australia‘s Dreamtime.Innovation permeates almost every aspect of the design, engineering and construction of the Athletic Centre, in particular its roofing system.In a major departure from conventionally used grandstand roofing systems, an extremely lightweight roof structure was designed which is suspended by a network of cables from two 45m high steel masts at each end of the stand.These masts provide support for the front of the roof and six raking front stays from each mast transfer the downward load from the rafters with two back stays anchoring the masts to the ground. The steel masts had the potentially conflicting responsibility of carrying loads of 350 tonnes yet also provide an aesthetically fine and lightweight structure.A combination of a core of four clustered tubes braced by pre-tensioned high strength rod bracing elements best fulfilled aesthetic and economic requirements when compared to seven alternative structure mast schemes.The engineering of such a mast is at the absolute cutting edge of analysis and design techniques.Relevant Australian safety standards were exceeded as a direct result of the material chosen for the construction of the roof.The masts were entirely fabricated and preassembled in the shop, speeding erection and significantly enhancing site safety.Even the forestay cables were attached to the masts prior to erection.Thorough checking and computer analysis of all elements prior to erection saw the final location of the cables within 25 mm of the predicted position;a truly remarkable result.The roof was prefabricated in panels on the ground including roof girders, roof systems and ceilings, cables and lights and lifted into position without scaffolding.Secured by just four pins, the crane time required to erect each panel was significantly reduced. A 200 m long catenary cable taken over the top of each mast pedestal and connected to the forestays provides resistance to wind uplift.The forestays are pretensioned to tension the catenary cable and to minimise the sag of the stays under self-weight.This is a true tension structure.

The ability to attach floodlights to the roof-supporting steel masts also contributed dramatically to the economy of this scheme as two lighting structures for the arena were able to be deleted.A unique characteristic of the cable-stayed roofing system is that the roof tilts forward due to the double curvature of the roof profile, disposing of roof stormwater at the front edge and allowing maximum protection for spectators and officials.An aeroelastic model of the roof was wind tunnel tested at Monash University to provide an accurate determination of wind loads and to examine the dynamic behaviour of the roof.This wind tunnel testing resulted in very unusual load combinations which the unique behaviour of a cable structure was able to accommodate without significant cost penalty.The dynamic analysis and testing of the roof was complicated by the effect of cable sag which resulted in the natural frequency of the structure being load dependant, a highly unusual situation.State of the art engineering and computer analysis was carried out throughout the design stage.A specially developed computer program was used to determine the shape of the cable system under specified forestay pretensions and to calculate cable sags and total cable mass.Non-linear analysis was undertaken using a purpose written computer program which the building contractor used to determine the progressive changes in the geometry of the structure as the roof panels were erected.Durability of the structure was a major consideration in design.A special paint system was developed, castings were fully galvanised, and self draining and cleaning systems were an integral part of the design to minimise dust build-up and rainwater run-off.Exposed structural steelwork makes extensive use of closed sections, box and circular steel tubes, where dust build-up can be effectively washed away by rain, and to minimise potential roosting places for vermin.The decision to use a cable stayed structure was made after an exhaustive investigation and review of alternative roof schemes and how effectively they met the key criteria - efficiency in structure, cost effectiveness, aesthetics, image, buildability, user friendliness, effect on the environment and durability.The construction of the Sydney International Athletic Centre formed a major part of Sydney‘s bid for the 2000 Olympics and represents an outstanding asset for the people of Sydney of which they can be justifiably proud.The successful use of steel for this structure and the role of steel technology combined with innovative design and engineering techniques was influential in Sydney securing the 2000 Olympics.The structure was completed six months ahead of time and under budget and results in a roof with superior weather protection for the public.Throughout the intense bid process, the Australian steel design and construction industry was the subject of immense international scrutiny with nothing short of exceptional expertise and practice in steel design acceptable.The result is a triumph of what can be achieved with a careful attention to details, world best practice in engineering techniques and pushing technology to its limits in from of the watchful eyes of the world.The Sydney International Athletic Centre rests as evidence of what can be achieved in Australia with steel construction.This stadium represents innovation in the true sense of the work.There is no other stadium like it anywhere else in the world.

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