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The Sixth Street Viaduct is a viaduct bridge that connects the Arts District in Downtown Los Angeles with the Boyle Heights neighborhood. It spans the Los Angeles River, the Santa Ana Freeway (US 101), and the Golden State Freeway (I-5), as well as Metrolink and Union Pacific railroad tracks and several local streets. Built in 1932, the viaduct is composed of three independent structures: the reinforced concrete west segment, the central steel arch segment over the river, and the reinforced concrete east segment. In 1986, the Caltrans bridge survey found the 6th Street Viaduct eligible for inclusion in the National Register of Historic Places.〔(【引用サイトリンク】url=http://www.sixthstreetviaduct.org/history )〕 Demolition of the bridge is scheduled to begin January 8, 2016. ==Demolition and replacement== During the construction of the viaduct in the 1930s, an on-site plant was used to supply the concrete for construction. However, the quality of the concrete turned out to have a high alkali content and led to an alkali-silica reaction which creates cracks in the concrete and saps the strength of the structure. It is one of the only historic LA River bridges to suffer from ASR. Estimates are that the current viaduct has a 70% probability of collapse due to a major earthquake within 50 years. The bridge will close January 3, 2016 and demolition is scheduled to begin January 8, 2016. An estimated 48,000 cubic yards of concrete, 1,245 tons of structural steel and 4,200 tons of rebar will be hauled away as construction begins on the replacement. The new bridge designed by architect Michael Maltzan is set to be completed in 2018. City leaders are also looking into building parks and plazas around the newly built bridge. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sixth Street Viaduct」の詳細全文を読む スポンサード リンク
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