Jambatan London Bridge, London, United Kingdom [1176]

Jambatan London, salah satu daripada beberapa struktur berturut-turut yang merangkumi Sungai Thames antara Borough High Street di Southwark dan King William Street di Kota London.

Jambatan London Lama

The Old London Bridge of the nursery rhyme terkenal sejak tahun 1176, ketika Peter, seorang imam dan pendeta St. Mary's Colechurch, memulakan pembinaan yayasan. Menggantikan jambatan kayu (salah satu dari beberapa yang dibina pada akhir Rom dan awal abad pertengahan), struktur Peter adalah jambatan lengkungan batu besar pertama yang dibina di Britain. Itu terdiri dari 19 lengkungan runcing, masing-masing dengan jarak sekitar 24 kaki (7 meter), dibangun di atas dermaga selebar 20 kaki (6 meter); pembukaan ke-20 dirancang untuk dijangkau oleh jambatan kayu. Asas batu dari dermaga dibangun di dalam cofferdam yang dibuat dengan menggerakkan timbunan kayu ke dasar sungai; ini pada gilirannya dikelilingi oleh jalak (pengisian batu longgar yang ditutup oleh timbunan). Hasil daripada halangan yang dihadapi semasa memandu cerucuk,jarak lengkungan yang dibina sebenarnya berbeza dari 15 hingga 34 kaki (5 hingga 10 meter). Di samping itu, lebar pelindung pelindung sangat besar sehingga keseluruhan jalan air dikurangkan menjadi seperempat dari lebar asalnya, dan air laut meraung melalui lengkungan sempit seperti jarak tempuh. "Menembak jambatan" dengan kapal kecil menjadi salah satu keseronokan warga London.

Pada tahun 1205 Peter of Colechurch meninggal dunia, dan tiga warga London yang lain menyelesaikan jambatan itu pada tahun 1209. Hampir sahaja jambatan itu bukan sahaja menjadi persimpangan komersial yang penting tetapi juga tempat perniagaan dan kediaman pilihan. Kedai-kedai berbaris di kedua-dua jalan di antara pintu-pintu kubu di kedua-dua hujungnya; rumah dibina di atas kedai, dengan 138 premis direkodkan pada tahun 1358. Laluan pejalan kaki dan bilik tambahan diperluas di antara bangunan, mengubah jalan raya menjadi jalan seperti terowong di mana pedagang dan pelancong lain sibuk. Pada tahun 1580-an, semasa pemerintahan Ratu Elizabeth I, kilang air dipasang yang menambah kegemparan.

The bridge became the site of calamities. Three years after its completion a huge fire destroyed all the buildings and killed as many as 3,000 people. But the houses (a source of income for the bridge) were quickly rebuilt, lining the 926-foot (282-metre) length of the bridge and reducing the carriageway to only 12 feet (4 metres). In 1282 five arches collapsed under the pressure of winter ice. These, too, were rebuilt, and the bridge, though often in a state of disrepair, survived as London’s sole crossing of the Thames until 1750. In that year Westminster Bridge opened, despite opposition from City merchants.

Shortly thereafter the City decided to repair Peter of Colechurch’s bridge, and the project was given to Charles Labelye, designer of the Westminster Bridge. By 1762 all the houses were removed, the carriageway was widened to 46 feet (14 metres), and the two central arches were replaced by one great arch at mid-span. The removal of the central pier led to serious erosion of the riverbed, and gravel was constantly poured to protect the remaining piers. Finally the maintenance became too much of a burden, and the City asked the renowned engineer John Rennie to design a wholly new structure several yards upstream.

New London Bridge

For the new structure, Rennie proposed five semielliptical stone arches, with the central span reaching 150 feet (46 metres), the next two 140 feet (43 metres), and the two shore spans 130 feet (40 metres). Rennie died in 1821 before work began, and the job was left to his two sons. George Rennie had actually made the design in 1820, but construction was conducted under John Rennie, Jr., beginning in 1824. In 1831 King William IV and Queen Adelaide arrived by water to celebrate the opening of the new bridge. Demolition of the ancient structure began that year, and by 1832 it disappeared, having served 622 years.

Rennie’s bridge survived less than 140 years. Between 1968 and 1971 its facing stone was dismantled and shipped across the Atlantic Ocean to the U.S. state of Arizona, where it was reerected on a five-span core of reinforced concrete to serve as a tourist attraction at the resort town of Lake Havasu City. The New London Bridge now crosses Lake Havasu behind Parker Dam, 155 miles (250 km) south of Hoover Dam on the Colorado River.

Modern London Bridge

The current London Bridge, built between 1968 and 1972, replaced Rennie’s stone arches with beams of prestressed concrete reaching 340 feet (104 metres) in the central span. Construction was carried out using the cantilever method, with segments being built outward from two piers, each segment tied to the previous one by high-strength steel tendons. In the centre the two cantilevers did not meet but stopped short, leaving a space into which the builders placed a concrete beam to complete the span. The design represents a major post-World War II innovation in bridge engineering, but the bridge itself is not of great historical significance.