The effects of residual stresses on the column behaviour of hot finished structural steel hollow sections
The following work describes the measurement of longitudinal
residual stresses in hot finished structural steel hollow sections.
All samples were supplied by the Tubes Division of British Steel
Corporation (B.S.C.)and include circular and rectangular profiles
manufactured by all of the methods employed by B.S.C. A total of
sixty-eight profiles were examined. The technique used to
determine the longitudinal stress state was the slicing method with
strain release measured by mechanical extensometers. A new
experimental method has been developed for the rectangular
sections, where access to the inside corner area was restricted.
The effect of these measured residual stress values, or
idealisations based on them, on the behaviour of axially loaded pin
ended columns is then examined by the development of inelastic
column buckling computer programs. Various iterative solution
routines are compared and a new accelerated relaxation procedure is
developed. The relative effects of material and geometric
imperfections on column behaviour are examined and the results
obtained compared with existing and proposed column buckling design
methods. One of the analysis programs is extended to cater for the
application of primary bending moments at the ends of the columns
and results obtained compared with existing design equations for
beam-columns and modifications are suggested.
The column buckling behaviour of hot finished hollow steel
sections is also compared to geometrically similar profiles
manufactured by cold forming or by welding.
The phenomenon of local buckling of sections with relatively
thin walls is also theoretically examined by utilising a non-linear
finite element program. The effects of various parameters on local
buckling are examined, including corner geometry, stiffening effect
of stockier adjacent faces, initial geometric imperfections and
residual stresses. Existing design rules for local buckling are
described and comparisons made.