INTERPRETATION OF THE STRUCTURAL RELIABILITY INDEX BY STUDY OF HOT ROLLED STEEL BEAMS

Resumo

Reliability analysis is a used tool to measure a structure’s ability of perform safety and
serviceability requirements. Methods for reliability assessment have been developed based on using the
probability distribution functions of input random variables accounting for the uncertainties coming both
structural properties and external actions. In the present structural codes the safety verification is based
on a linear analysis of the structure and the satisfaction of ultimate and serviceability limit states, using
a semi-probabilistic security format through the consideration of resistance factor and load factors,
which affect the action values and the characteristic values of the material properties. This work presents
an investigation of the safety level of hot rolled steel I-beams dimensioned according to Brazilian
building code NBR 8800:2008. The study allows an interpretation of the reliability indexes calculated
for steel beams by the First-Order Reliability Method (FORM), when this reliability analysis is
compared with structural design results. In the analyzed beams, it is assumed that local buckling and
lateral-torsional buckling are not controlling limit states, i.e., the beam section is compact and laterally
supported along the length. The results of this study show the correspondence of the structural reliability
indices with the beams calculated by the standard.