Thin-walled steel studs in fire : analysis and design recommendations

Abstract: Development of steel frame modular buildings is gaining increased popularity and support throughout Europe. Due to flexibility in construction and good long-term performance, lightweight steel frame structures are often preferred solutions, for instance in partitions and suspended ceilings as well as for load-bearing elements. In many applications the steel frame structure are required, indirectly or directly, to have a certain fire resistance performance. There is still knowledge to be gained in order to accomplish efficient rules for assessment of the behaviour of lightweight steel frames in fire situations. The lack of such rules creates a disadvantage for the elements since they will require additionally costly protection measures, or to perform expensive fire tests. The problem is more pronounced for load-bearing structures. This makes design by testing a rather inefficient method. Therefore, it is important to develop economical design rules at elevated temperature for possible implementation in Eurocode 3. The main objectives of the thesis is to evaluate FE-models for analysis of thin-walled steel columns and to compare the results with experiments at room temperature and at elevated temperatures. The main contribution of the work is to recommend the design model for a possible implementation in Eurocode 3, Part 1-2. The design model includes possibility of flexural and torsional-flexural failure mode. It contemplates thermal deflection, reduced yield strength and elastic modulus and is evaluated on studs with a constant temperature (symmetric heating) and with a temperature gradient (unsymmetrical heating). Constant temperature distribution is assumed along studs in both cases.