NCh2369 vs. ASCE 7 – Strength vs. Ductility? Industrial steel moment frames

Abstract

Earthquake-resistant design philosophies behind ASCE7-10/AISC341-10 and NCh2369.Of2003 are different. The differences make very difficult the task of satisfying simultaneously both design criteria, both from the conceptual and the practical points of view.This paper presents the comparison of the inelastic seismic response of a moment frames of an industrial structure. The structure was designed to meet independently with both American and Chilean Codes provisions. The comparison of the seismic response is made at three levels of earthquake excitations: for a standard earthquake demand, (10% of exceedance in a 50-year period), for a maximum credible demand, (2% of exceedance in 50-year period), and for an operational level earthquake, (50% of exceedance in a 30-year period). Each of these earthquake levels is represented by a set of artificial ground motions compatibles with the corresponding design spectra. Additionally, some design aspects showing the differences among the design philosophies are presented.The results obtained after the analysis show a similar behavior for the both operant and standard level design. Relative to maximum credible design the results show a best performance in the Chilean design, with interstory displacement and base shear reduction about 30%. In this way and considering the target of the industrial Chilean code (limited shutdown period after the earthquake) it can be seen that codes responses are according with their own philosophies. Finally, the measure responses modification factors after nonlinear analysis show a best assessment from the ASCE7-10/AISC341-10 design.