布莱希维泽步行桥，巴克南，德国

工程设计：施莱克·贝格曼及合伙人事务所Engineers:schlaich bergermann partner



布莱希维泽步行桥，巴克南，德国

Bleichwiese Footbridge,Backnang,Germany,2013

工程设计：施莱克·贝格曼及合伙人事务所Engineers:schlaich bergermann partner

1　设计草图/Sketch

1

项目信息/Credits and Data

客户/Client:Stadtbauamt Backnang

长度/Length:27m

步行道宽度/Width of Walkway:2.50m结构高度/Structural Height:1.50m

摄影/Photos:sbp/Michael Zimmermann

新的布莱希维瑟施泰格位于巴克南，靠近斯图加特。它是从火车站经施蒂夫茨霍夫到重新设计的布莱希维瑟地区最短的路线。今天，布莱希维瑟是古城中心与提供日用品的现代商业建筑施魏策尔堡之间颇具吸引力的通路。它在城市发展和景观规划中起着关键作用，因此是城镇中心连接“古今”最重要的开放空间之一。朝向历史建筑施蒂夫茨霍夫的堤岸为原始的密林陡坡。

老旧的木桁架桥由于技术上的缺陷被拆除，取而代之的是与布莱希维瑟地区现代形象浑然一体的无障碍桥。原有的基础在可能的条件下进行了再利用。

其主要目的是设计一座独立桥。一端体现现代精神，另一端融合自然风景。快速而简洁的安装则是另一项重要要求。

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因此桥体由两个几乎相同的部分组成，而后这些完全预制的构件就可以在现场直接组装。两个箱形梁的梁高向中部逐渐增加，它们既是结构也是扶手。箱形梁在桥中部的最高点断开，分为上下弦。上弦设计为铰接的受压杆；下弦是受拉的连接点。箱形梁在连接点处的梁高最小，约为30cm。这样就在桥的中部形成了一个三角形的凹口，使桥身显得通灵轻巧。镀铬螺栓则让连接点成为点睛之笔。

箱形梁在第一个横断面顶缘的外面上有一个尖锐的折角，以交错的光影为桥身增添了几分意趣。

箱形梁之间悬挂的是轻质的各向异性梁板。梁板整合的正交肋带来的框架效应能避免箱形梁倾斜。

在夜间，步行道的表面由与箱形梁一体的节能LED灯带照亮。到了白天，步行道的明亮色调与暗色的箱形梁构成鲜明对比，而箱形梁的色彩又同周围的环境协调一致。

透空的扶手望去犹如浮于桥上，更突显桥身的轻灵。水平不锈钢缆（ø 4mm）穿在纤细的栏杆和底轨之间。出于安全考虑，钢缆在步行区的间距被缩小，越靠近顶部则越大。在桥的中部，扶手就被受压杆取代，让人可以触摸和感受这种结构。在这一点上，不锈钢缆就直接附在主梁的连接处。

桥身架在4个能够各向滑动的支撑垫上。两个沿桥纵轴布置的导向锥约束着支撑垫滑动的方向。在朝向施蒂夫茨霍夫的桥基上，纵横两个方向都是固定的。而朝向布莱希维瑟的桥基只有横向是固定的。为节约成本，现有的基础被最大限度地再利用。因此要充分利用材料，保证新桥的静荷载不超过木桁架桥的重量。（尚晋 译）

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(ø 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.

评论

何可人：这是一座宁静的桥，只是单纯的从此岸过渡到彼岸，进入寂静的林地，再返回尘世。一座设计精彩的桥，并不在乎其规模和尺度，而在于其形态与结构的完美结合。这座简洁利索的小桥，其简洁有力的造型，完美地与结构精巧结合，桥身侧翼在中部与桥身的铰接三角形是其结构设计的核心，同时也是造型设计的视觉中心，传递着具有工业感的现代性。人行其上，或许会自然到意识不到是在通过一座桥，然而侧望，则会是非常具有动感的一个穿越。最想做的事是骑着单车，静静地过桥，隐入密林深处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.

高岩：桥的设计，形式发挥所受的结构限制很大，无论什么样式，结构选型无外乎梁式、索桥和拱桥这3类。布莱希维泽步行桥跨度比较小，用简支梁式经济合理。建筑师的设计策略，源于对基地文脉的充分理解，即它的重要位置注定其个性鲜明，它的基地条件要求其施工过程简易快速。设计最巧妙的地方在于利用栏杆的高度，用三角形体作为主要结构构件，有效地体现了简支梁受力的分布特点，并自然而然地促成桥体底边在中间的杵拴连接，桥体上边独立表现的压杆，以及只有10cm厚的桥面板，让行者充分领悟到由桥的结构受力与其所响应的形式和谐演奏出的整体美感。

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　桥底/Bottom of bridge

5　夜景/Night view