COMPARISON BETWEEN STANDARDIZED APPROXIMATED AND RIGOROUS STRUCTURAL ANALYSIS FOR ESTIMATING 2ND ORDER EFFECTS APPLIED TO STEEL STRUCTURES

Resumo

Considering the approximated method of structural analysis estimating 2nd order effects
applied to steel structures, recommended by the ABNT NBR 8800 (2008) standard, also known as
Amplification Coefficients Method, and the constant search for greater structural efficiency and
consequently economy, the aim of this study was to compare the numerical responses of steel
structures subjected to horizontal and vertical loadings, obtained by approximated standardized
analysis and by rigorous geometrically nonlinear analysis. For that, a program was developed to
perform all the constituent steps of the Amplification Coefficients Method and to determine internal
forces and displacements. The resulting considered models are useful for medium lateral
displaceability class in which the 2nd order analysis, as a rule, can be performed by simplified or
approximated method. The results from the approximated approach were compared to the results from
a more rigorous nonlinear approach aided by the software SAP2000. It was observed that the internal
forces obtained by approximation are similar to those with the rigorous one, concerning axial and
shearing forces. Differences can be witnessed regarding bending moment results, being the
standardized method conservative. Analysis of the results from structures classified with small and
large lateral displaceability were also made, grounding standard classification method and following
proceedures recommendations. Concluding, the normative methodology is a proper approach to
nonlinear analysis in steel structures as long as classification permits.