Dimensionamento de um pavimento em estrutura mista aço-concreto em situação de incêndio

Abstract

Mixed structures consist of the association of steel (such as formwork, in the case of slabs, and profiles, in the case of beams) with concrete, so both materials work together in resistance to mechanical stress. The use of the mixed system, when compared to steel and reinforced concrete structures, has several advantages, such as reduction of the execution time of work, reduction of the weight of the structure, increase of overall rigidity, among others. However, since steel is structurally present, it is necessary to have a more accurate project in a fire situation, since there is a rapid degradation of the mechanical properties of the element when exposed to high temperatures. Therefore, the main objective of this work is to design the structural components, beams and slabs, which compose a steel - concrete mixed floor of an example building according to ABNT NBR 14323:2013, comparing the load efforts with the resistant efforts in the event of fire. In case of non-attendance, it will be proposed the application of coating against fire in the profiles and redone the verification. Consequently, the project considerations were presented, as well as the final design performed at room temperature, according to ABNT NBR 8800:2008, the floor was considered as not anchored and the mixed beams dimensioned as bi supported. As a result, the procedures for designing in a fire situation were described, verification was carried out for all slabs and for the most requested beam of the floor. The scaling of the remaining beams was presented in spreadsheets, in Appendix. It was concluded that, for the steel-concrete mixed pavement studied, the elements used did not meet the requirements prescribed by the standard, and it is necessary to apply a coating against fire. The projected mortar used, Monokote MK-6, added about 15 times the value of the resistance moment value when compared to uncoated, causing most of the structural elements meet the requirements.