جسر كليداو

جسر كليداو ( ينطق [ ˈklɛðai ] ، بالويلزية : Pont Cleddau ) في بيمبروكشاير ، ويلز ، يحمل الطريق A477 فوق نهر كليداو بين نيلاند وبيمبروك دوك .

تسببت أخطاء في تصميم الجسر الصندوقي في انهياره أثناء بنائه عام 1970. أصبح الجسر جاهزًا للتشغيل خلال عام 1975 وتديره الآن مجلس مقاطعة بيمبروكشاير . ^{[ 1 ]}

يقسم نهر كليدو مقاطعة بيمبروكشاير . تقع هوبز بوينت في بيمبروك دوك جنوباً، ونييلاند شمالاً، على بُعد أقل من 1.6 كيلومتر عبر النهر، ولكن كان يتطلب الوصول من إحداهما إلى الأخرى قطع مسافة 45 كيلومتراً بالسيارة . بين عامي 1858 و1950، سمحت الأميرالية بتشغيل عبّارات بخارية بين المدينتين. ومنذ عام 1950، أدار مجلس المقاطعة خدمة عبّارات تتسع لـ 24 مركبة و250 مشاة.  

في ستينيات القرن الماضي، اتُخذ قرار باستبدال خدمة العبّارات، ما استدعى بناء جسرين، أحدهما يعبر نهر كليدو، والآخر أصغر حجماً شمال نيلاند يعبر خور ويستفيلد بيل . وتم تعيين شركتي سير ألكسندر جيب وشركائه وفريمان فوكس وشركائه كمهندسين استشاريين مشتركين، ورُسّي عقد بناء الجسر على شركة إيه إي فار المحدودة في سبتمبر 1968 مقابل 2.1 مليون جنيه إسترليني.

The project was expected to be completed by March 1971 but on 2 June 1970 a 230-foot (70 m) cantilever being used to put one of the 150-tonne sections into position collapsed on the south side of the estuary. Four workers died and five were injured. Construction was halted until October 1972. The Merrison Committee of Inquiry into the Design and Erection of Steel Box Girder Bridges concluded that the cause of the collapse was the inadequacy of the design of a pier support diaphragm (a diaphragm of half the designed thickness was used),^[2] but considered "the failure of site organisation between the parties as of more general significance".^[3] The committee believed that the only relevant Code of Practice relating to the design of steel bridges in the UK was inadequate for applications such as the Cleddau Bridge, and they implemented Interim Design and Workmanship Rules.^[4] These rules laid the groundwork for a new British Standard covering box girder bridge design.^[5]As of 2007, the collapse during construction is the last major bridge disaster in the UK.^[6][7]

The final cost of construction was £11.83 million and the bridge was opened to traffic on 20 March 1975. The £7 million of overspend was attributed to design changes made due to the Merrison Committee's recommendations. This was covered by a £3 million out-of-court settlement between the County Council and the consulting engineers and a £4 million interest-free loan from the Government that was repayable over 40 years.^[8] 885,900 crossings were made during the bridge's first year in operation.^[9]

It was originally called the Milford Haven Bridge. The ferry service between Hobbs Point and Neyland ceased when the construction of the Cleddau Bridge was completed in 1975. The ferry Cleddau King was sold, modified by Harland & Wolff of Belfast and put into operation as a reserve Portaferry–Strangford ferry in Northern Ireland.^[10]

Formerly, tolls were collected on the south side of the bridge from traffic travelling in both directions. Toll booths with barriers were introduced in September 2004 to reduce the number of vehicles driving through without paying.^[11] The bridge has been toll-free since 28 March 2019.^[12]

The county council may close the bridge depending on wind speed, wind direction and the weather forecast. Vehicles taller than 1.9 m (6 ft 3 in), bicycles and motorcycles are usually not permitted to cross the bridge when wind speeds exceed 50 mph (80 km/h). The bridge is closed to all vehicles and pedestrians should wind speeds exceed 70 mph (110 km/h). The council records the time the bridge is closed.^[13]

A memorial plaque to the four men who died in the bridge collapse was unveiled on the 25th anniversary of the disaster in 1995, but was reported stolen in 2017.^[7]

• List of bridges in Wales