Variant Concept of Elevation of a Steel Grid Tower
J. Krentowski , S. Mlonek , Kamil Ziminski , Piotr Knyziak
AbstractThe article presents the stages of analysis of an existing steel structure of a 35m-high lattice tower, located in a woodland. The assessment of the condition of the tower’s structural elements and connections was made in the aspect of plans for its elevation, in order to install an observation camera warning against fire hazard. The tower up to 30 m was made of five segments with a square section, with decreasing width from 4.86 m to 2.05 m. The last segment, 5m high, was made as a cuboid. Truss walls and horizontal truss membranes were used. Technical platforms were installed inside the shaft. Rolled sections of St3S steel with a yield point fd = 215 MPa were used as structural elements. The tower was erected on concrete spot footing. Static and strength analyses of the existing structure were carried out, taking into account the actual condition of materials and connections in the aspect of the planned modernization. The influence of wind gusts and the load from ice were taken into account. The user planned to install an observation camera on an additional mast with a height of 12 m. Initially, the concept of an additional construction made of Ø60.3 x 4 mm steel pipe set in a steel sleeve fastened to the bridge plates was adopted. The support tube was stabilized with four steel stay rope with diameter of 5 mm, fixed to the corners of the platform at 35m. As a result of the conducted calculations, it was justified that the adopted concept is inappropriate due to the fact that the limit values of horizontal displacement of the end of the mast, also unacceptable due to excessive vibrations of the image from the observation camera, would have been exceeded. Therefore, another concept was developed, in which a 12 m mast would be made with an aluminium lattice construction. In the horizontal section, the mast would have the shape of an equilateral triangle with a side length of 450 mm (420 mm in the axes). The mast branches would be made of RO35x2 round tubes, and the gratings would be made of rectangular, full profiles with a 20 x 10 mm cross section. The mast would consist of three latticed segments with a length of 4.0 m. The stays would be made of Ø5 mm steel ropes. Mast with sliding support would be stabilized with lashings, mounted on three levels. In order to obtain a proper tilting of the lashings in relation to the vertical axis of the mast, it is planned to use additional horizontal expansion elements made of square profiles RK80x5, located at the level of the highest platform. As a result of the calculations carried out, it was shown that a construction designed as presented would meet the conditions of limit states defined in the current standards of fire safety. The work was summarized by providing user guidelines for ensuring the durability of the modernized structure in the anticipated period of usage.
|Journal series||IOP Conference Series: Materials Science and Engineering, ISSN , e-ISSN 1757-899X|
|Publication size in sheets||0.5|
|Conference||World Multidisciplinary Civil Engineering-Architecture-Urban Planning Symposium (WMCAUS), 18-06-2018 - 22-06-2018, Prague, Czechy|
|Keywords in English||observation tower, numerical analysis, modernized structure, durability|
|Score||= 5.0, 11-07-2020, ArticleFromConference|
|Publication indicators||= 0; = 0|
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