布萊希維澤步行橋，巴克南，德國

工程設計：施萊克·貝格曼及合伙人事務所Engineers:schlaich bergermann partner

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布萊希維澤步行橋，巴克南，德國

Bleichwiese Footbridge,Backnang,Germany,2013

工程設計：施萊克·貝格曼及合伙人事務所Engineers:schlaich bergermann partner

1　設計草圖/Sketch

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項目信息/Credits and Data

客戶/Client:Stadtbauamt Backnang

長度/Length:27m

步行道寬度/Width of Walkway:2.50m結構高度/Structural Height:1.50m

攝影/Photos:sbp/Michael Zimmermann

新的布萊希維瑟施泰格位于巴克南，靠近斯圖加特。它是從火車站經施蒂夫茨霍夫到重新設計的布萊希維瑟地區最短的路線。今天，布萊希維瑟是古城中心與提供日用品的現代商業建筑施魏策爾堡之間頗具吸引力的通路。它在城市發展和景觀規劃中起著關鍵作用，因此是城鎮中心連接“古今”最重要的開放空間之一。朝向歷史建筑施蒂夫茨霍夫的堤岸為原始的密林陡坡。

老舊的木桁架橋由于技術上的缺陷被拆除，取而代之的是與布萊希維瑟地區現代形象渾然一體的無障礙橋。原有的基礎在可能的條件下進行了再利用。

其主要目的是設計一座獨立橋。一端體現現代精神，另一端融合自然風景。快速而簡潔的安裝則是另一項重要要求。

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因此橋體由兩個幾乎相同的部分組成，而后這些完全預制的構件就可以在現場直接組裝。兩個箱形梁的梁高向中部逐漸增加，它們既是結構也是扶手。箱形梁在橋中部的最高點斷開，分為上下弦。上弦設計為鉸接的受壓桿；下弦是受拉的連接點。箱形梁在連接點處的梁高最小，約為30cm。這樣就在橋的中部形成了一個三角形的凹口，使橋身顯得通靈輕巧。鍍鉻螺栓則讓連接點成為點睛之筆。

箱形梁在第一個橫斷面頂緣的外面上有一個尖銳的折角，以交錯的光影為橋身增添了幾分意趣。

箱形梁之間懸掛的是輕質的各向異性梁板。梁板整合的正交肋帶來的框架效應能避免箱形梁傾斜。

在夜間，步行道的表面由與箱形梁一體的節能LED燈帶照亮。到了白天，步行道的明亮色調與暗色的箱形梁構成鮮明對比，而箱形梁的色彩又同周圍的環境協調一致。

透空的扶手望去猶如浮于橋上，更突顯橋身的輕靈。水平不銹鋼纜（? 4mm）穿在纖細的欄桿和底軌之間。出于安全考慮，鋼纜在步行區的間距被縮小，越靠近頂部則越大。在橋的中部，扶手就被受壓桿取代，讓人可以觸摸和感受這種結構。在這一點上，不銹鋼纜就直接附在主梁的連接處。

橋身架在4個能夠各向滑動的支撐墊上。兩個沿橋縱軸布置的導向錐約束著支撐墊滑動的方向。在朝向施蒂夫茨霍夫的橋基上，縱橫兩個方向都是固定的。而朝向布萊希維瑟的橋基只有橫向是固定的。為節約成本，現有的基礎被最大限度地再利用。因此要充分利用材料，保證新橋的靜荷載不超過木桁架橋的重量。（尚晉 譯）

2　全景/Panoramic view

The new Bleichwiesensteg in Backnang,near Stuttgart,is the shortest connection from the train station via the Stiftshof to a redesigned area named Bleichwiese.Today the Bleichwiese serves as an attractive link between the historic town centre and the so called Schweizerbau; a modern building that houses shopping facilities for daily supplies.It plays a key role in urban development and landscape planning.Thus,it is one of the most important open spaces within the town center that connects "new" and "old".The bank facing the historic Stiftshof is a steep,wooded slope,largely untouched.

The main aim was to design a bridge that is independent,but also incorporates the modern spirit of one end of the bridge,as well as the natural scenery on the other side.The quick and easy installation was another major requirement.

Hence,the bridge consists of two almost identical parts.These completely prefabricated parts could then be combined and assembled directly on site.Two box girders that feature increasing heights towards the centre comprise the structure and at the same time also the banister.At the highest point,midway,the box girders are disconnected and split into upper and lower chord.The upper chord has been designed as articulated compression rod; the lower chord is a joint that bears tensile loads.Reaching the joint the height of the box girders is reduced to its minimal height of around 30cm.Consequently a triangular recess has been created at the bridge centre that lends the bridge an air of lightness.Due to the chrome coated bolts the joints stand out as a special feature.

At the top edge of the first cross section the box girders feature a sharp bend at the outer face.This lends the bridge another dimension through the shape’s interplay of light and shadow.

A lightweight orthotropic slab is suspended between the box girders.Cross ribs integrated in theslab generate a frame effect that prevents the box girders from tilting.

3　近景/Close view

At night,the walkway slab with its light toned surfacing is illuminated by energy-saving LED lighting strips that are integrated into the box girders.Also during the day,the light hue of the walkway creates a contrast to the significantly darker box girders,whose chromaticity has been adapted to the surroundings.

The highly transparent banister seems to be floating above the bridge and thus emphasizes the bridge's air of lightness.Horizontal stainless steel cables(? 4mm)run between the slender balustrade posts and the bottom rail.For safety reasons these had to be mounted with less clearance at the foot area,before the distance gradually increases towards the top.At the centre of the bridge the compression rod takes over the function of the guardrail; and thus invites to touch and understand the structure.At this point the stainless steel cables are tightened directly over the connection of the main beams.

The bridge rests on four movable bearing pads that are slidable in all directions.Two guiding spikes arranged on the longitudinal bridge axis determine the way the bearings can slide.At the abutment facing the Stiftshof the longitudinal and the transverse direction is held in place.While at the abutment facing the Bleichwiese only the transverse direction is fixed.To save costs,the existing foundation has been reused as far as possible.Hence,materials had to be used efficiently to make sure that the dead load of the new bridge does not exceed the weight of the timber truss bridge.

評論

何可人：這是一座寧靜的橋，只是單純的從此岸過渡到彼岸，進入寂靜的林地，再返回塵世。一座設計精彩的橋，并不在乎其規模和尺度，而在于其形態與結構的完美結合。這座簡潔利索的小橋，其簡潔有力的造型，完美地與結構精巧結合，橋身側翼在中部與橋身的鉸接三角形是其結構設計的核心，同時也是造型設計的視覺中心，傳遞著具有工業感的現代性。人行其上，或許會自然到意識不到是在通過一座橋，然而側望，則會是非常具有動感的一個穿越。最想做的事是騎著單車，靜靜地過橋，隱入密林深處找一艘不存在的方舟。

Comments

HE Keren:A quiet bridge simply connecting both sides,it enters the silent woods,and then comes back to the man-made world.A well-designed bridge is not up to its scale and mass,but to its integrity of form and structure.This austere bridge possesses a very simple but powerful form,which perfectly integrates with its exquisite structure.The hinged triangle segments in the middle of the bridge that connect the sides are the core of the structural design,as well as the focal point of the form,which conveys the message of industrial modernity.When you walk on the bridge,you might not realize you are crossing the water.But when you look around,you will probably feel the dynamic transcendence.What you want to do most at this moment is to cross the bridge quietly,get into the dense forest and seek for a non-existing Ark.

高巖：橋的設計，形式發揮所受的結構限制很大，無論什么樣式，結構選型無外乎梁式、索橋和拱橋這3類。布萊希維澤步行橋跨度比較小，用簡支梁式經濟合理。建筑師的設計策略，源于對基地文脈的充分理解，即它的重要位置注定其個性鮮明，它的基地條件要求其施工過程簡易快速。設計最巧妙的地方在于利用欄桿的高度，用三角形體作為主要結構構件，有效地體現了簡支梁受力的分布特點，并自然而然地促成橋體底邊在中間的杵拴連接，橋體上邊獨立表現的壓桿，以及只有10cm厚的橋面板，讓行者充分領悟到由橋的結構受力與其所響應的形式和諧演奏出的整體美感。

GAO Yan:The form of a bridge design has to comply with the structural constrains.Whatever innovative forms a bridge may be,its structure is always limited to three types,i.e.girder,cable suspension and arch.Bleichwiese Footbridge employs a simple supported beam solution as an economic and efficient solution to respond its small span.The design originated from the architect's insightful understanding of the site context and the project objectives.It is important to exhibit its distinct characteristics with simple and fast construction due to the physical site conditions.The architect made the best use of the balustrade height with the triangular form as the main structural elements,which effectively reflects the force distribution of the simply supported beam and inherently forms a series of tectonic response,including the pin joint at the bottom with the independent compressions bars at the top in the middle of the bridge,as well as the deck slabs as thin as 10cm.The synthetic design of the bridge celebrates the aesthetic harmony that integrates the structural stress and the formal response.

4　橋底/Bottom of bridge

5　夜景/Night view