鐵匠城門步行橋，布魯日，比利時

建筑設(shè)計及結(jié)構(gòu)設(shè)計：奈伊及合伙人事務(wù)所Architects and Structural Engineers:Ney & Partners

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鐵匠城門步行橋，布魯日，比利時

Smedenpoort Footbridges,Bruges,Belgium,2012

建筑設(shè)計及結(jié)構(gòu)設(shè)計：奈伊及合伙人事務(wù)所
Architects and Structural Engineers:Ney & Partners

1　實景/Bridge view

鐵匠城門是布魯日現(xiàn)存的4座古城門之一，建于13世紀(jì)。然而在現(xiàn)代交通壓力下，它已經(jīng)成為城市的瓶頸，對于川流不息的車流、人流和自行車流來說過于狹窄。因此，布魯日市政府決定在城門的兩側(cè)建造新的步行橋來緩解這個問題，建造的主管方是古跡及景觀委員會。

通過在現(xiàn)存的城門兩側(cè)添加兩座步行橋，行人將與車輛分流。車輛依然走城門中央的道路，自行車可以使用城門的側(cè)門，而行人將會獲得一條全新的路徑，來穿越這條古老的防衛(wèi)運(yùn)河。

出于對地段歷史價值的尊重，步行橋的結(jié)構(gòu)設(shè)計需要盡量纖薄和通透。它更像是一條景觀中的散步道，而非簡單的一座橋。兩座橋在平面上彎曲，從而對城門形成“環(huán)抱”之勢。密集的細(xì)柱降低了橋梁的跨度，而扶手也被設(shè)計為結(jié)構(gòu)體系的一部分，使得材料的使用更加高效。最終，橋梁的體量元素都被最小化，形成一座極為通透的結(jié)構(gòu)。

橋梁的結(jié)構(gòu)采用了銹蝕金屬格柵，橋面鋪設(shè)混凝土地磚。橋梁中的實心金屬柱以及此類的細(xì)節(jié)都是對鐵匠工藝傳統(tǒng)的致敬。

結(jié)構(gòu)體系結(jié)合了華倫式桁架和弗倫第爾桁架，扶手加強(qiáng)了結(jié)構(gòu)的縱向穩(wěn)定性。扶手作為桁架的上部，而橫向梁則形成桁架的下部。兩種構(gòu)件分別承受彎曲時的壓力和張力，而縱向構(gòu)件則承受剪力。連續(xù)的桁架是由間距5m左右的細(xì)柱支撐的。結(jié)構(gòu)的橫向硬度來源于鋼框架和混凝土鋪地，后者在截面上隆起形成一個拱形的空心結(jié)構(gòu)。

照明是由藏在扶手外側(cè)的發(fā)光二極管實現(xiàn)的，它在晚上將增強(qiáng)橋梁環(huán)抱古城門的效果。扶手上包裹了不銹鋼面層。（黃華青 譯）

2　剖面/Section

3　平面/Plan

4　步行橋與鐵匠城門/the bridge and the Blacksmith's Gateway

By placing two footbridges next to the existing gateway,pedestrians could be separated from vehicles,which could continue to use the gateway,and bicycles which could use the doors at the sides of the gateway.Pedestrians would have a new route across the old defensive canal.

In order to respect the historical value of the site,the footbridge structure was designed to be as slender and transparent as possible.They are intended to create something more akin to a promenade in the landscape than merely a bridge over water.The bridges are curved on plan,so that they "embrace" the gateway; the use of multiple small columns reduces the span length,and the design of a parapet which acts as part of the structural system results in more efficient use of material.This enables the dimensions of the elements to be reduced,creating a more transparent structure.

The structure consists of a weathering steel lattice construction with concrete tiles forming the bridge deck.The use of solid steel bars and the type of details chosen are intended to reference the heritage craftsmanship of the blacksmith.

The structural system is a combination of a Warren truss and a Vierendeel truss,and the railing acts structurally to provide vertical stability.The handrail forms the upper member of the truss while a longitudinal beam forms the lower member.These take up the bending moments,respectively acting in compression and tension,while the uprights take the shear forces.The continuous trusses are supported on slender columns at spacings of just over 5m.The horizontal stiffness of the structure is provided by the steel framework and concrete tiles which form an arched lattice in the horizontal plane.

Lighting is achieved by the use of light-emitting diodes integrated into the handrail of the outer railing,which at night enhances the impression that the bridges are embracing the historic gate.The handrail is provided with a stainless steel covering.

項目信息/Credits and Data

客戶/Client:布魯日市/City of Bruges

總承建商/General Contractor:Artes Depret

觀察組顯效37例、有效30例、無效3例，總有效率為95.7%；對照組顯效34例、有效20例、無效9例，總有效率為85.7%，差異具有統(tǒng)計學(xué)意義（χ2=4.039 5，P=0.044 4）。

鋼結(jié)構(gòu)承建商/Steel Contractor:Anmeco

長度/Length:南橋/Southern bridge:62.7m，北橋/ northern bridge:57.2m

跨距/Span:5m

寬度/Width:2.5m

結(jié)構(gòu)/Structure:桁架橋及弗倫第爾桁架橋的結(jié)合/ Combination of truss bridge and vierendeeltruss bridge

材料/Material:耐候鋼結(jié)構(gòu)及混凝土結(jié)構(gòu)面板/Weathering steel structure with concrete structural tiles

鋼結(jié)構(gòu)/Structural Steel:56t

造價/Cost:€1,100,000

攝影/Photos:Ney & Partners,Jean Luc Deru(fig.1,7),Alain Trellu(fig.4)

5　扶手欄桿圖案/Passerelle railing bars pattern

6　水平荷載/Horizontal load bearing

7　夜景/Night view

評論

張昕楠：消隱的景框

纖細(xì)與透明，是解讀這座步行橋的關(guān)鍵詞。在平面的處理上，弧線的形式，既對原有的古橋進(jìn)行了回避，又強(qiáng)化了空間透視，如同畫框一般將古橋突顯出來。在結(jié)構(gòu)方面，所有的構(gòu)件都被處理得足夠纖細(xì)：相對密集的橋柱一方面消解了更大跨度對橋身剛性的要求，一方面也降低了橋柱本身 截面尺寸，從而使其更為纖細(xì)；同時，護(hù)欄的集束形式回應(yīng)了當(dāng)?shù)氐蔫F藝傳統(tǒng)，并和橋身共同形成一個剛性的整體，從而減少了不必要的結(jié)構(gòu)構(gòu)件。這一消隱的處理方式，最大程度地弱化了新加橋體對原有古跡景觀畫面的影響，并使得步行者宛如漂浮地行進(jìn)在其中。

范路：“環(huán)抱”歷史是鐵匠城門步行橋的核心意向。步行橋分為兩座，分列城門兩側(cè)，并在平面上彎曲，“環(huán)抱”充滿歷史的古城門。橋體結(jié)構(gòu)極盡纖薄，最大限度地弱化體量，減小對古城門形象的影響。而金屬橋身上的種種細(xì)節(jié)設(shè)計，更是以當(dāng)代做法向鐵匠城的傳統(tǒng)工藝致敬。

8　橫梁截面細(xì)部/Detail of supports on cross-beams and concrete tiles

9　左側(cè)斜撐剖面/Section of left bracing

Comments

ZHANG Xinnan:the Transparent Frame

"Slender" and "transparent" are the keywords to interpret this pedestrian bridge.In dealing with the plan,the arc form not only avoided the existing ancient bridge,but also enhanced spatial perspective,highlighting the ancient bridge as a framed view.In structure,all the components are made slim and slender:on one hand,the dense columns fulfill the rigid requirements of the greater span of the bridge,while also reducing the cross-sectional dimension of the column itself; at the same time,the cluster form of the fence responds to local craftsmanship of the blacksmith and constitutes a rigid whole with the bridge itself,thus reducing unnecessary structural components.This transparent approach weakened the impact of the new part of the bridge on the view of existing ancient monuments,and makes the pedestrians seem floating in between.

FAN Lu:"Embrace history" is the dominant intention of the design for Smedenpoort Footbridge.The new two footbridges curved on plan are placed on both sides of the existing gateway to emphasize the importance of the historical structure.In order to minimize the interference with image of the gateway,the footbridge structure was designed to be as slender as transparent as possible.Some types of detail designs for the steel bridge are referenced on the heritage craftsmanship of the blacksmith in the city.