39 research outputs found
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Strengthening Techniques for Greenhouses
Steel greenhouse structures are generally constructed by individual sole contractors using quick empirical structural calculations (pre-engineered solutions). It is also common to import standard greenhouses from other countries, mainly from The Netherlands, Italy, and France, and sometimes from Great Britain and Israel. Evidently, these countries differ concerning the local wind and snow conditions. Therefore, there is a need for a better design of structures accepted as satisfactory, while installation can be done in a different location. Many greenhouse structures incorporating poor designs or inappropriate pre-engineered solutions are currently in use. At the same time, demolition and reconstruction represent a very expensive solution considering the loss of crop production and the demolition and construction costs; thus, strengthening is a reasonable alternative. This paper presents strengthening techniques for steel greenhouses that are code-deficient according to EN 13031 and Eurocodes. Consequently, two case studies are presented as typical applications of greenhouse structure strengthening
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Fire Resistance of Unprotected Ultra Shallow Floor Beams (USFB): A Numerical Investigation
This paper presents the fire resistance behaviour of partially encased in concrete ultra shallow floor beams (USFB) using numerical analysis method based on material specifications of the EN1994-1-2. Investigating the behaviour of USFBs under elevated temperatures is crucial in determining their fire resistance and evaluating their overall performance in contemporary construction. Even though the manufacturing company provides fire resistances for USFBs based on EC4-1-2 procedures, their response to elevated temperature effects remains up to date neither well documented nor clearly understood. The analyses involved two different beams of span 5 m and 8 m respectively, as specified by the manufacturer. Analysis results showed that such beams, when unprotected, experience severe temperature gradients if exposed to fire, as the lower flange still remains unprotected in contrast to the concrete encased part of the cross-section. As it was anticipated, the moment capacity governs the fire resistance of the beams and the load factor highly effects the elevated temperature behaviour. In addition, the loss of the lower flange, which develops high temperatures, is not compensated by the web and consequently the moment capacity ultimately depends on the temperature of the lower flange. Results also suggest that simulated beams sustained the applied load for approximately 40 min of exposure to the standard fire
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Post-fire assessment and reinstatement of steel structures
Purpose
This paper aims to present technical aspects of the assessment method and evaluation of fire damaged steel structures. The current work focuses on the behavior of structural normal steel (hot-rolled and cold-formed) and high-strength bolts after exposure to elevated temperatures. Information on stainless steel, cast iron and wrought iron is also presented.
Design/methodology/approach
Because of the complexity of the issue, an elaborate presentation of the mechanical properties influencing factors is followed. Subsequently, a wide range of experimental studies is extensively reviewed in the literature while simplified equations for determining the post-fire mechanical properties are proposed, following appropriate categorization. Moreover, the reinstatement survey is also comprehensively described.
Findings
Useful conclusions are drawn for the safe reuse of the structural elements and connection components. According to the parametric investigation of the aforementioned data, it can be safely concluded that the most common scenario of buildings after fire events, i.e. apart from excessively distorted structures, implies considerable remaining capacity of the structure, highlighting that subsequent demolition should not be the case, especially regarding critical infrastructure and buildings.
Originality/value
The stability of the structure as a whole is addressed, with aim to establish specific guidelines and code provisions for the correct appraisal and rehabilitation of fire damaged structures
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Fire resistance of axially restrained and partially unprotected Ultra Shallow Floor Beams (USFBÂź) and DELTABEAMÂź composite beams
Ultra-shallow floor types such as the USFBÂź and DELTABEAMÂź beam âplugâ composite flooring systems are recently developed and have seen many applications in contemporary construction. They involve partially encased steel beams in concrete, with the lower flange remaining exposed. Besides the satisfactory behavior of the system at ambient conditions, understanding their response to elevated temperatures is critical in evaluating their overall performance. Previous numerical studies of the authors have investigated their fire resistance when simply supported. The computational analyses demonstrated that such flooring systems are experiencing severe thermal gradients and bowing. When such beams are axially restrained, the compression due to the restraining may produce second order effects on the bowed beams. On the other hand, the effect of axial restraints is difficult to be estimated because of the temperatureâs non-uniformity across the cross-sections. For this reason, comprehensive Finite Element Analyses (FEA) were implemented in this paper to simulate the response of such restrained beams subjected to fire. Material properties were modelled according to Eurocodes. The coupled thermal-structural parametric analyses involved different variations of the âshortestâ cross-sections. From the FE analyses, useful conclusions are drawn