COLLAPSING OF THE REINFORCED CONCRETE ROOF BEEM DESIGNED FOR THE INDUSTRIAL BUILDDING. ITS CAUSES, WORKING CONDITIONS AND CONDITIONS FOR SAFETY OF REMAINING ROOF BEAMS
Journal Title: Вісник Національного університету "Львівська політехніка". Серія "Теорія та практика будівництва" - Year 2018, Vol 0, Issue 904
Abstract
The project of the production house features the design of concrete roof. The roof is composed of typical precast reinforced concrete beams: single-slope (for ending spans) and double-slope (for middle span). The beam types are БО9 and БД9 accordingly, spanning over 9.0 m, designed for a typical ПК-01-05 series “Reinforced precast concrete load bearing structure for roofing with rolled-on surface” (issue 1 – beams). The article presents the results of collapsed reinforced concrete roof beam exploration. The industrial building beam has collapsed after a breakdown of its longitudinal rebar pack of 2Ø20+1Ø32 p.5 (A300C). The beam is T-shaped in section with its flange in a compression zone. The beam features a multirow composition of its longitudal performing reinforcement as a pack of repetitive section rebars precasted of hot rolled steel, allowing to shrink the beams web width down to the minimum of 100 mm. The check has shown that the breakdown could be caused by poor quality of the Ø32 mm rebar joints along the span. The reason could be either the beam’s reinforcement welding process or during the beams substantial overload during its early performance. Additionally the actual rebar composition is discovered to differ from he one in the design dwawings. The calculation check resembles that the number of remaining working 2Ø20 rebars was not enough to support the actual load of the roof structure. Therefore its ongoing breakdown has turned to the beams physical dismental with following consequences. The analysis of the remaining beams’ working conditions has shown the lack of their load bearing capacity. In order to ensure normal performance, the beams in every span should be additionally reinforced. There are two reinforcement options suggested: first, usage of prestressed sprengel ties (for БО9 beam types) or second, installation of a springing post in the middle span supported by triangular sprengel system of double L-shaped members (for БД9 beam types).
Authors and Affiliations
Roman Shulyar, Viktor Kvasha
Keywords
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