24th Concrete Days 2017

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Authors: Adam Svoboda, Ladislav Klusáček
Abstract: Post-tensioning is a suitable, reliable and durable method for strengthening existing reinforced concrete bridge structures. The high efficiency of post-tensioning can be seen on many implemented applications for bridge reconstructions worldwide. There are still several thousands of beam and slab bridges the load capacity of which no longer meets the demanding transport conditions. The oldest reinforced concrete beam bridges, from 1905-1915, are designed according to the Austrian Ministry of Railways Bridge Standard of 1904 when the largest load to be considered was the 18-tonne road steamroller. These bridges are not dimensioned for the currently valid traffic load values. The paper deals with the strengthening of the parapet beam bridges from the period of 1905-1930. These bridges have two main beams pulled over the bridge deck which is supported by cross beams. The cross beams connect the two main beams, forming a half-frame in the transverse direction which provides spatial rigidity of the structure. The spans of these bridges are usually in the range of 15 to 25 m.
Authors: Radim Čajka, Jana Vašková, Pavlina Matečková, Kamil Burkovič
Abstract: Heavy industry, industrial plants and technology facilities use really big manufacturing units or assemblies with the weight of tens of tons. In case of rotary kilns, the weight can reach hundreds of tons. During the production process, those units move, creating, in addition to considerable static effects, big dynamic effects. Industrial facilities often face failures of the reinforced concrete foundation which is loaded dynamically by a rotating machine. Such failures typically result in cracks and failures of any of the foundation cross-section. Thus, a part of the foundation starts deviating, the rigidity goes down, geometry of the machine position is changing and an accident may occur - for instance, bearings may fail or malfunctions may occur in the machine. This has also happened in the case described in this article. The subject of the article is the large foundation structure of the rolling device in the Block Mill I in Třinecké železárny a.s. The slab of the foundation structure is approximately a T-shape, which has nearly 43 m in one direction and over 30 m in the other direction. The monolith foundation slab will be 2.0 m thick, the whole foundation structure will be 2.0 - 8.0 m thick. With such an extensive foundation, considerable attention must be paid not only to the design and realization, but also to the effect of the hydration heat.

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