Stability analysis of light gauge steel members using the finite element method and the generalized beam theory.
In this thesis a finite element programme for material and geometric nonlinear
analysis, has been modified with pre- and post-data processing and eigenvalue
solution. More efficient methods to solve elastic and inelastic eigenvalue and
eigenvectors have been developed to deal with stability problems in structures with
arbitrary shape, irregular stiffness, loads and boundary conditions.
The Generalized Beam Theory (GBT) with the facilities of elastic spring restraints,
buckling under coupled loads, different load locations has been developed and
programmed by the author. It has been applied to reveal the basic behaviour and
the interaction between the modes of light gauge steel members. It has been found
that the AISI design approach with elastic bucking stresses obtained using GBT can
be used to correctly predict the strength of compression thin-walled columns.
Three different types of widely used light gauge steel members, namely rack
columns, purlins and decks, have been analyzed using both FEM and GBT. The
comparison of results from the numerical analyses and comprehensive tests agrees
well. The author has risen to the challenge of complicated buckling problems and
a pseudo-plastic design procedure for a continuous purlins and roof decks has been
established in order to make the best us of the materials.
Through the highly complex analyses, some important conclusions for composite
deck profiles in the wet concrete stage have been obtained. The ECCS and AISI
design approaches for bending have been found to be conservative when the deck
is subject to plastic buckling or strength failure. The calculation of the ultimate web
crippling load without consideration of bending moment is awkward and further light
is shed on this topical problem. The influence of dimples in reducing the deck
bending resistance mainly depends on the flange slenderness