Development and Assessment of a Practical Stiffness Reduction Method for the in-Plane Design of Steel Frames

Abstract

In this paper, the development and assessment of a stiffness reduction method for the in-plane design of steel frames is presented. The adopted stiffness reduction approach is implemented by reducing the flexural stiffnesses (EI) of the members of a steel frame by considering the first-order forces they are subjected to through the stiffness reduction functions and performing Geometrically Nonlinear Analysis (i.e. second-order elastic analysis). Since the presented approach uses stiffness reduction functions that fully take into account the deleterious influence of imperfections and the spread of plasticity on the structural response and member strengths, it obviates the need of using member design equations, and only requires cross-section strength checks. The accuracy of the presented approach is illustrated for individual steel members and non-redundant and redundant benchmark steel frames from the literature. In all the considered cases, the presented method is verified against the results obtained from nonlinear finite element modelling. A comparison of the presented approach against the notional load method of the European structural steel design code EN 1993-1-1 and the direct analysis method of the US structural steel design code AISC 360-10 is also provided