Equivalent unique global and local initial imperfection - Imperfection in EN 1993-1-1 and EN 1999-1-1 Clause 5.3.2 (11) - calculation procedure and discovered obstacles

Abstract

Equivalent unique global and local initial imperfection is introduced in standards EN 1993-1-1, EN 1999-1-1 in clause 5.3.2 (11) and in Slovak national annex to EN 1993-1-1 NB. 5. However approach described in these standards needs further explanation to fully understand its background to reduce possibility of causing errors. Equivalent unique global and local initial imperfection and derived equivalent unique global and local initial imperfection method is based on obtaining amplitude for structural buckling mode, which can be than used as full-sized imperfection in assessment of structures loaded by combination of axial compression forces and bending moments. Equivalent unique global and local initial imperfection was firstly used and introduced by prof. Eugen Chladný from Slovak University of Technology in Bratislava. The origin of this method was based on the need of assessment of upper chords of open-deck truss bridges. The main idea is described in detail by Prof. Eugen Chladný and Magdaléna Štujberová in paper in magazine Stahlbau vol. 82. Equivalent unique global and local initial imperfection method in mentioned standards and paper is designated for plane structures like simple structural members or frame structures. This paper examines in plane behavior of structures with presented imperfection and calculation procedure, which allows fast examination of many different types of plane structures.