霍奇斯湖橋，圣地亞哥，美國(guó)

工程設(shè)計(jì)：林同棪工程顧問(wèn)股份有限公司，伊里·斯特拉斯基工程顧問(wèn)公司，薩夫迪·拉維內(nèi)斯建筑事務(wù)所Engineers:T.Y.Lin International,Jiri Strasky Consulting Engineer,Safdie Rabines Architects

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霍奇斯湖橋，圣地亞哥，美國(guó)

Lake Hodges Bridge,San Diego,USA,2009

工程設(shè)計(jì)：林同棪工程顧問(wèn)股份有限公司，伊里·斯特拉斯基工程顧問(wèn)公司，薩夫迪·拉維內(nèi)斯建筑事務(wù)所Engineers:T.Y.Lin International,Jiri Strasky Consulting Engineer,Safdie Rabines Architects

1 實(shí)景/Bridge view

2 鳥(niǎo)瞰/Bird's-eye view

這座步行橋位于圣地亞哥郡的北部，是圣地亞哥河谷區(qū)開(kāi)闊地公園的一景。該橋由3跨100.58m長(zhǎng)的懸鏈連結(jié)而成，其中每一跨的中點(diǎn)下垂高度為1.41m。

霍奇斯湖懸鏈橋全長(zhǎng)301.75m，由預(yù)制的懸鏈節(jié)段和現(xiàn)澆的橋鞍組成。懸鏈的兩端固定在兩岸橋臺(tái)上，并與各個(gè)橋墩框接在一起。這種結(jié)構(gòu)解決方案借鑒并發(fā)展了布拉格-特洛伊和雷丁的橋梁項(xiàng)目設(shè)計(jì)方式。

預(yù)制的懸鏈節(jié)段厚0.407m、長(zhǎng)3.048m、寬4.266m，每段由兩條邊主梁和一塊甲板組成，互相連接的結(jié)點(diǎn)處由隔板進(jìn)行固定。在建造過(guò)程中，懸鏈節(jié)段首先被放置在承重纜繩上，后沿著纜繩滑動(dòng)到預(yù)定位置。在澆筑完橋鞍和預(yù)制節(jié)段之間連接節(jié)點(diǎn)后，懸鏈被預(yù)拉伸的筋腱拉緊。承重纜繩系統(tǒng)由2×3條19-0.6"的纜繩組成，預(yù)應(yīng)力筋腱由2×3 條27-0.6"的鋼筋組成。纜繩和筋腱都藏在邊梁上挖出的槽中。

每個(gè)橋鞍都有不同的厚度和寬度。厚度從0.407～0.910m不等，寬度從4.266～7.320m不等。每個(gè)橋墩上都設(shè)置了一個(gè)觀景平臺(tái)和座椅。橋鞍位于所有橋墩或橋臺(tái)的正上方，是在所有預(yù)制節(jié)段建造完成后，被澆筑在預(yù)制節(jié)段表面承托著的模板中的。建造過(guò)程中，安裝在鋼鞍座上的鐵氟龍板為承重纜繩提供支撐。

53×107N的水平拉力通過(guò)橋臺(tái)被傳送到兩岸的土壤中：左岸通過(guò)直徑2.7m的4個(gè)鉆孔樁，右岸通過(guò)石錨。

設(shè)計(jì)經(jīng)過(guò)了細(xì)致的靜、動(dòng)力分析實(shí)驗(yàn)，不僅能夠承擔(dān)普通的靜壓力，還可以耐受較大的地震荷載。分析表明，這座步行橋能夠同時(shí)為行人提供舒適的步行體驗(yàn)，又在地震中具有一定彈性。為了證實(shí)該橋能在強(qiáng)風(fēng)中保持平穩(wěn)，加州的西風(fēng)實(shí)驗(yàn)室為它進(jìn)行了一次特殊的風(fēng)力實(shí)驗(yàn)分析，將1:10的橋梁截面模型放入風(fēng)洞，檢測(cè)了橋面的空氣動(dòng)力學(xué)承重特性。（張?jiān)Ｏ?譯）

項(xiàng)目信息/Credits and Data

總長(zhǎng)/Total Length:302m

最大跨距/Maximum Span:100.5m寬度/Width:3.7m

攝影/Photos:T.Y.Lin International

The bridge is located in the northern part of San Diego County and it is a part of the San Dieguito River Valley Regional Open Space Park.The bridge is formed by a continuous stress ribbon of three equal spans of length of 100.58m.The sag at mid-spans is 1.41m.The stress ribbon of the total length of 301.75m is assembled of precast segments and cast-in-place saddles situated at all supports.The stress ribbon is fixed into the end abutments and it is frame connected with intermediate piers.The structural solution was developed from the pedestrian bridges built in Prague-Troja and in Redding.

The precast segments of the depth of 0.407m are 3.048m long and 4.266m wide.Each segment is formed by two edge girders and a deck slab.At joints the segments are strengthened by diaphragms.During the erection the segments were suspended on bearing cables and shifted along them to the design position.After casting of saddles and joints between segments,the stress ribbon was post-tensioned by prestressing tendons.The bearing cables are formed by 2×3 cables of 19-0.6" strands,the prestressing tendons are formed by 2×3 tendons of 27-0.6" strand.Both bearing cables and prestressing tendons are placed in the troughs situated at the edge girders.

The saddles have a variable depth and width.The depth varies from 0.407 to 0.910m,the width change from 4.266 to 7.320m.Above supports a viewing platforms with benches were created.The saddles were cast after erection of all segments in the formwork suspended on the already erected segments and supported by piers or abutments.During the erection the bearing cables were placed on Teflon plates situated on steel saddles.

The horizontal force as large as 53MN is transformed into the soil at the left abutment by four drilled shafts of a diameter of 2.70m,at the right abutment by rock anchors,

Very detailed static and dynamic analyses have been performed.The structure was checked not only for service load but also for significant seismic load.The analyses have proved that the bridge will be comfortable to users and will remain elastic under seismic loading.To verify that the bridge would be stable under heavy winds,a special wind analysis was performed by West Wind Labs,CA.Wind tunnel tests on a 1/10 scale model of the bridge section were performed to determine the aerodynamic load characteristics of the bridge deck.

評(píng)論

王向榮：霍奇斯湖橋如同一條懸浮在湖上的飄帶，聯(lián)通兩岸，串聯(lián)起區(qū)域的徒步路徑。熱愛(ài)自然的人一定會(huì)喜歡這座橋，它融合在湖光山色之中，形態(tài)輕盈舒展，飄蕩的線(xiàn)型呼應(yīng)著起伏的山巒。橋梁不僅是穿越湖面的便捷通道，也為步行者提供了觀賞風(fēng)景的全新視角。創(chuàng)新性的結(jié)構(gòu)體系為橋梁帶來(lái)獨(dú)特的形態(tài)，作為一個(gè)藝術(shù)的介入，這座橋也強(qiáng)化了周?chē)L(fēng)景的價(jià)值。

張昕楠：融于自然

位于圣地亞哥河谷公園的霍奇湖步行橋，以其高超的結(jié)構(gòu)和技術(shù)展示了在自然之中如何減少人工構(gòu)筑物對(duì)景觀的破壞。一方面，橋體的設(shè)計(jì)需要應(yīng)對(duì)河面300m寬度帶來(lái)的對(duì)橋體跨度的挑戰(zhàn)，另一方面，又要盡量減少對(duì)自然河面的占據(jù)以及對(duì)景觀的破壞。最終的設(shè)計(jì)僅以?xún)蓚€(gè)立于水中的支柱形成了3個(gè)跨度，并將預(yù)應(yīng)力懸索隱藏在橋板之中，從而在保證結(jié)構(gòu)穩(wěn)定性的前提下，降低了橋板的厚度，并減弱了對(duì)自然景觀的影響。

Comments

WANG Xiangrong:Spanning over the lake,Lake Hodges Bridge looks like a ribbon connecting both banks to string up the trails around this area.Nature-lovers would certainly like it.The Bridge merged in the landscape of lakes and mountains presents a lightsome and stretching appearance,with its fluttering linear form echoing to the rolling hills.It not only an easy access across the lake but also provides an unusual view of sight-seeing.Its creative body structure gives a unique form,while keeping surrounding views valuable as an art intervene.

ZHANG Xinnan:Harmony with Nature

Located in San Diego River Valley Park,the Lake Hodges pedestrian bridge shows how to reduce the destruction brought by artificial structures to the natural landscape with its superb structure and technology.On one hand,the design of the bridge needs to respond to the challenges of the bridge span brought by the 300-meter-wide river; on the other hand,it has to minimize occupation of the river and destruction of the natural landscape.The final design only uses two pillars in water to form a three-span bridge,and the prestressing tendons are hidden in the deck of the bridge,so that while the stability of the structure is guaranteed,the thickness of the deck is reduced and the impact on the natural landscape is weakened.