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力與美的結合—淡江大橋的特點

Combining strength and beauty—Features of the Danjiang Bridge

全世界最大跨距單塔不對稱斜張橋

The world's longest-span single-pylon asymmetric cable-stayed bridge

淡江大橋跨河主橋段長920m,橋塔高211m,主跨距450m,背跨距175m,橋面最寬處約70m,為世界主跨最長之單塔不對稱跨距斜張橋。考量日落位置與淡水河岩盤深度,橋塔設立於河道中央偏淡水側,並於河道深槽區保留200m寬、至少20m淨高的船舶運航空間。

The main river-crossing section of the Danjiang Bridge has a length of 920m, a pylon height of 211m, a main front span length of 450m, a back span length of 175m, and a maximum deck width around 70m. It is the world's longest-span single-pylon asymmetric span cable-stayed bridge. In view of the sunset location and the depth of bedrock under the Tamsui River, the pylon is located toward the Tamsui side from the center of the river chan-nel, and a boat navigation channel with a width of 200m and clearance of at least 20m will be retained in the river trough area under the bridge.

臺灣第一座公路和軌道共構的景觀橋

Taiwan's first co-constructed highway and railway scenic bridge

因應淡海輕軌運輸系統建設與通車,淡江大橋規劃中也預留未來推動淡海輕軌系統「八里延伸線」所需的橋面空間(八里輕軌未施工前規劃作為公車專用道)。

In response to the construction and use of the Danhai Light Rail system, the plans for the Danjiang Bridge also call for the retention of deck space for the future construction of a Bali extension line (the space for the pro-posed Bali extension line will be used as a dedicated bus lane until the light rail line has been opened

橋梁設計

Bridge design

淡江大橋為北臺灣的新地標,位處重要的交通動線,除了基本運輸功能外,更肩負了重大災害發生時維生動線之重任。故本工程在耐震與抗風設計、水文水理分析、防蝕耐久等方面,皆比照世界大型橋梁,以適合橋址環境條件的最高標準進行設計與檢核。

The Danjiang Bridge will be a new landmark in northern Taiwan, and will provide an important traffic route. Apart from the bridge's basic transportation function, it will also serve as a safe escape and emergency response route in the event of a major natural disaster. As a consequence, the project's earthquake resistance and wind resistance design, hydrological and hydraulic analysis, anti-corrosion and durability design work have been con-ducted on the basis of the common standards for large bridges around the world, the design and review work has been performed in an effort to ensure that the bridge satisfies the environmental conditions of the bridge site to the highest standards.

耐震設計

Earthquake resistance design

臺灣位處歐亞大陸板塊與菲律賓海板塊之交界處,地震頻繁,為世界六大强震區之一。淡江大橋耐震設計除依據2009年6月交通部頒之「公路橋梁耐震設計規範」進行地震反應譜與地震歷時分析外,並納入工址附近50km半徑範圍內斷層震源參數及實際紀錄地震資料進行「場址地震危害度分析」,以最大地震情況下做為橋梁耐震設計之目標。橋梁結構系統工程師透過調整結構載重分佈,並於適當位置設置HFR、FVD阻尼器及摩擦單擺支承等多項隔減震設施,可有效控制橋梁振動頻率,抵抗7級以上劇震,確保結構安全並保障震後生命線功能。

Taiwan is located at the junction of the Eurasian and Philippines Sea plates, and has frequent earthquakes. It is considered one of the world's six most seismically active areas. Apart from performing earthquake response spectrum and earthquake time-history analysis in accordance with the "Highway Bridge Earthquake Resistance Design Standards" issued by the Ministry of Transportation and Communications in June 2009, the earthquake resistance design of the Danjiang Bridge also included "site earthquake hazard analysis" by using fault seismic source parameters and actually recorded earthquake datas for the region within 50km of the project site, with the goal of ensuring that the bridge's earthquake resistance is sufficient to withstand the strongest earthquake under consideration. By adjusting the distribution of structural load, and establishing seismic isolation and energy dis-sipation facilities, including HFR and FVD dampers and friction pendulum bearings, in appropriate locations, the engineers responsible for the bridge's structural system effectively controlled the bridge's vibration frequency, allowing it to withstand earthquakes of over 7th grade, ensuring structural safety, and safeguarding the bridge's function as an escape route following an severe earthquake, as mentioned above.

淡江大橋鄰近斷層震源分佈

Location of fault seismic sources

淡江大橋支承系統與受力說明

The Danjiang Bridge's bearing system and earthquake loadings

地震來襲時,橋梁所受的作用力可以分為水平力與垂直力兩種,其中水平力又可分為車行方向及垂直車行方向兩種(即橋梁之縱向及橫向),共計三個方向的作用力。

When an earthquake occurs, the forces on the bridge can be divided into horizontal and vertical components, and the horizontal components can be further divided into forces in vehicles' direction of motion and perpendicu-lar to it (i.e., in the longitudinal and transversal directions relative to the bridge), so forces in three directions must be taken into consideration.

垂直向地震力

Vertical seismic forces

由所有橋墩墩頂所設支承直接傳導到基礎地盤;橋面斜拉鋼索則以張力型式傳導到主橋塔上,並以垂直壓力方式傳遞到基礎地盤。

The bearings mounted on the top of the piers can directly transmit vertical forces to the foundation ground, and the deck stays can transmit tensile forces to the main pylon, which transmits the forces to the foundation ground in the form of vertical comprehensive force pressure.

水平向地震力

Horizontal seismic forces

縱向:主要由設在主橋塔柱的7支HFR阻尼器與設在橋梁兩端輔助用的4支FVD阻尼器,透過液壓方式減緩力道並傳遞到基礎地盤。

橫向:所有內側橋墩頂部設置的FPB鋼製支承與橋塔八里側橋腳橫向配置的合成橡膠墊,以磨擦碰撞消能方式共同減緩力道並傳遞到基礎地盤。

Longitudinal: Longitudinal forces are chiefly reduced and transmitted to the foundation ground employing hydrau-lic pressure via 7 HFR dampers mounted on the main pylon and 4 auxiliary FVD dampers mounted on the two ends of the bridge.

Transversal: Steel bearings mounted on the top of interior piers and synthetic rubber pads mounted on the both transversal sides of main pylon leg of Bali side employed friction and collision energy dissipation methods to reduce forces and transmit them to the foundation ground.

風洞試驗

Wind tunnel testing

淡水河口位於台灣北部,地形開闊,一般來說冬季吹東北季風、夏季吹西南季風;夏季可能另受颱風影響而有來自西北方之強風吹撫。為了瞭解淡江大橋在各種風力作用下產生之可能影響,如:顫振、抖振、渦流顫振等現象,淡江大橋設計時進行「風洞模型試驗」及數位模型分析,模擬橋梁受風力吹撫下之氣動及氣彈行為。試驗包括「斷面模型試驗」與「全橋模型試驗」兩類,試驗內容包括施工階段橋梁穩定性、完工後整體橋梁穩定性、橋上車輛的穩定性與行人舒適性、纜索風致振動反應評估…等等。試驗結果顯示淡江大橋各方面皆不產生氣動及氣彈不穩定現象,而試驗所得之結構部件風動反應力數據亦納入結構分析與設計,確保橋梁結構安全。

The bridge is situated in a wide-open location at the mouth of the Tamsui River, in northern Taiwan. Generally speaking, the northeast monsoon wind blows in winter, and the southwest monsoon wind blows in summer. Fur-thermore, when typhoons approach in the summertime, heavy winds may blow from the northwest. In order to understand the behavior of the Danjiang Bridge—including flutter, buffeting, and vortex shedding—under different wind speeds and directions, wind tunnel model testing and numerical modeling analysis were performed during the bridge design stage to simulate the bridge's responses when wind forces are present. Tests included a "sec-tional model test" and "full-bridge model test," and test content included bridge stability during the construction stage, stability of the completed bridge, stability of vehicles on the bridge, comfort of pedestrians on the bridge, and assessment of the vibration response of cables under windy conditions, etc. The results of these tests indi-cated that the Danjiang Bridge would not give rise to aerodynamic or aeroelastic instability, and the resulting wind force response data for structural components was included in structural analysis and design, ensuring the safety of the bridge structure.

獨立橋塔模型試驗(1:200縮尺模型)

Independent pylon model test (1:200 scale model)

水工模型試驗

Hydraulic model testing

淡江大橋跨越淡水河口,為了瞭解其橋塔與橋墩興建是否會對河川沖淤造成影響,以及河水沖刷對橋墩及其周邊河床的影響,於設計階段前期使用縮小比例的模型(比例1:81),進行「水工模型試驗」,模擬橋梁橋墩基礎在水流作用下的沖刷程度。試驗過程發現橋墩基礎樁帽頂高程低於現有河床面,可減輕橋墩基礎周圍河道沖刷,而試驗最終結果顯示為橋墩基礎周圍河道沖刷量不影響橋梁安全。

The Danjiang Bridge spans the mouth of the Tamsui River. In order to understand the effect of the construction of the bridge's pylon and piers on scouring and silting in the river, as well as the effect of scouring by the river flow on the piers and the nearby riverbed, a small-scale model (1:81 scale) was employed during the erarly de-sign stage for hydraulic model testing, which simulated the scouring of the foundations of the piers under river flow conditions. Testing revealed that the elevation of the pile caps of the pier foundations was lower than that of the current riverbed, which can reduce scouring around the pier foundations, and the final test results indicated that the amount of scouring around the pier foundations will not affect bridge safety.

橋塔基礎(無圍堰)沖刷試驗後周邊浸淤情形

State of nearby scouring and silting after pylon foundation(seen with no cofferdam) scouring testing

主橋塔局部沖刷試驗

Main pylon localized scouring testing

結果顯示主橋塔八里側呈現最大深度8公尺之沖刷

The results indicated that scouring occurred to a maximum depth of 8m on the Bali side of the main pylon

全橋一般沖刷試驗

Full bridge general scouring testing

結果顯示除主橋塔外,其餘橋墩樁帽皆未露出河床。

The results indicated that apart from the main pylon, none of the remaining pier pile caps were exposed above the riverbed.

河川影響詳估

Detailed assessment of impact on the river

河岸沖淤分析:淡江大橋興建後淡水側局部河岸沖刷略為增加(黑色虛線處),八里側河岸幾無影響,整體評估其不影響淡水河口沖淤情況。

Riverbank scouring and silting analysis: After the construction of the Danjiang Bridge, localized scouring of the riverbank on the Tamsui side will increase slightly (indicated by black dotted lines), but there will be almost no effect on the riverbank of the Bali side. An overall assessment concluded that the bridge will have no impact on scouring and silting at the mouth of the Tamsui River.

淡江大橋興建前

Before construction of the Danjiang Bridge

淡江大橋興建

After construction of the Danjiang Bridge

防蝕耐久

Anti-corrosion and durability measures

淡江大橋位於淡水河口,屬於極嚴重鹽害區,因此所採用混凝土之類型、配比、保護塗層、鋼筋保護層厚度及鋼構材的防蝕等均為耐久性設計重點。

The Danjiang Bridge's location at the mouth of the Tamsui River will expose it to severe salt damage. As a con-sequence, the concrete type, mixing ratio, protective coating, thickness of the rebar protection cover, and pre-vention of steel structure corrosion all constitute key aspects of the bridge's durability design.

1.依橋址所在環境條件,訂出符合120年使用年限之鋼筋保護層厚度。

In accordance with the environmental conditions of the bridge site, the thickness of the rebar protection cover met 120-year service life requirements.

2.河道中墩柱混凝土表面於帽樁頂至水下1公尺區間噴覆純聚脲;水下1公尺至水上10公尺區間則加覆一般氟碳防蝕塗裝。

A pure polyurea coating will be applied to the surface of the concrete piers in the river channel from the top of the pile caps to 1m below the water surface, and a general fluorocarbon resin anti-corrosion coating will be applied to the piers from 1m below the water surface to 10m above the surface.

3.河道中墩柱及主橋塔兩者之最外層主鋼筋及箍筋、繫筋均採鍍鋅鋼筋。

The main rebar elements, stirrups, and crossties in the outermost layer of the main pylon and piers in the river channel will consist of galvanized rebar.

4.鋼橋外露面使用重防蝕塗裝。

A heavy-duty anti-corrosion coating will be applied to exposed steel parts of the bridge.

5.採用含卜特蘭II型水泥或IP水硬性混凝土,降低混凝土裂縫發生機率。

Type II Portland cement or IP water-hardening concrete will be used to reduce the probablity of concrete cracking.

6.斜拉鋼索、支承、阻尼器、伸縮縫等設計為可置換,鋼橋塗裝及橋面防水層仍須於固定年限內維護更新。

The cables, bearings, dampers, and expansion joints are designed to be replaceable, and the steel coating and deck waterproof coating must be maintained and replaced after a certain number of years.

7.設置橋檢桁架以供定期檢修維護,另設針對橋塔、斜拉鋼索、鋼箱梁、橋墩P120及P140等重要結構元件與橋址自然環境進行24小時監控。

Inspection trusses will be installed to facilitate regular inspection and maintenance. In addition, important structural elements, such as the pylon, cables, steel box girders, and piers P120 and P140, and the natural environment around the bridge site, will proceed 24-hour monitoring.

7-2監測系統配置

Monitoring system configuration