Caracterização da flambagem lateral torcional e determinação do momento fletor característico para viga perfil “i” bissimétrica

Abstract

A increscent application a charging on steel bars – when they reach determined intensity – causing bend in the elements, the process of lateral torsional buckling starts, which is characterized by translating the section perpendicular to the direction of loading and rotation of the cross section in relation to the longitudinal axis, such a phenomenon constitutes an limit state of collapse related the instability. The brazilian standard ABNT NBR 8800:2008 has a methodology for calculating the characteristic bending moments, but few practical tests are found to compare the results obtained with the current standard. For this, a bissimetric “I” beam was tested with dimensions 76,2 x 8,48 with punctual loading in the middle of the span with the aid of the universal testing machine EMIC DL 2000 and supported on a reaction beam, measuring horizontal displacement on the compressed table with assistance of LVDT’s HBM WA 50mm. Observing a critical moment 208,3% greater than the plastification limit for a case with constant momentum across the beam (Cb=1) and 160,5% higher for punctual loading in the middle of the span (Cb=1,316), but both moments within the plastic behavior of the section, which is not allowed by standard being limited to the plastification moment of 810 kN*cm to section with Cb=1,316 and 624, 21 kN*cm for Cb=1, it being evident that there is a region in which the beam showed support capability, but that because of the regime of non-elastic behavior, is limited to safety.