Análise comparativa do dimensionamento de uma treliça plana de aço utilizando a a norma norte-americana AISC 360-05 e a norma brasileira NBR 8800:2008

Abstract

Metallic structures represent an interesting alternative for some situations in civil construction. In Brazil, even though it is still not widespread, it frequently appears in general purpose sheds and roof trusses. Its design requires special care and the use of computer programs can optimize and facilitate this task. In this sense, the present work approaches the situation of a truss on the roof of a fictitious industrial shed located in Santa Maria - RS. Initially, a brief description of the metal sheds and trusses will, so that the next steps are better understood. The permanent and variable loads are determined, with special attention given to the wind load, which plays a decisive role in the design of this type of structure. The truss is drawn and analyzed in the SAP2000 computer program, based on the North American standard AISC 360-05, in order to obtain the active efforts so that the computer program automatically assigns sections to the different elements. The results are verified according to ABNT NBR 8800:2008 both for the ultimate limit state and for the service limit state. Starting from an initial model, the ties were positioned so as to have traction as the greatest request among the load combinations made and thus use lighter profiles. Once the positions of the ties were defined, the automatic design of the program was carried out based on a list of back-to-back double angles for the chords and a list of simple angles for the ties and struts. It was possible to reduce the weight of the truss by almost 10% when analyzing the automatic results and using lighter profiles that meet the national standard in the upper chord and ties.