Cold-formed Edge and intermediate stiffener plays important role

Cold-formed
members are thin in nature, hence predominant mode of failure found to be
local. Edge and intermediate stiffener plays important role to improve local
buckling strength of the member. Various parameters influences the buckling
load of cold-formed member hence it is necessary to recognize influence
of these parameters on critical buckling load under axial compression. From
literature, it is observed that, influence of parameters on buckling load, like
shapes of intermediate stiffener, thickness of steel plate, width of flange,
depth of intermediate web stiffener and length of lip for cold-formed lipped
channel section has been not studied in detail. In this paper, the study have
been conducted on 924 models of lipped channel section and selected as per
criteria given in AISI -2007. In present study, the linear buckling analysis
has been performed on various shapes of triangular, trapezoidal and
quadrilateral intermediate stiffener by varying depth of intermediate stiffener
from 3 to 36 mm with constant thickness as 1.50 mm, thickness of steel plate
from 1.5 to 6 mm with constant ratio of depth of triangular intermediate
stiffener to depth of web or flange as 0.06,  flange width from 50 to 90 mm with constant
depth of triangular intermediate stiffener to depth of web or flange as 0.06,
width of triangular, trapezoidal and quadrilateral intermediate web stiffener
from 2 to 20 mm with constant ratio of depth of intermediate stiffener to depth
of web as 0.12 and length of lip from 3 to 24 mm for plain lipped channel
section.  The study have been conducted
on various models of lipped channel sections by varying lengths from 0.5 m to
6.0 m. The member has been analysed with both end fixed and allows translation
in the lateral direction. The linear buckling analysis have been performed on
various models by using finite element software ABAQUS. Local, distortional and
Euler’s failure modes were observed for critical elastic buckling. From the
study, it has been observed that, the shape of intermediate stiffener are
effective up to 2.50 m length of member and beyond that the effectiveness
diminishes. However, as compared to triangular and trapezoidal shape the
quadrilateral shape intermediate web stiffener imparts larger resistance to
buckling. Increase in thickness of steel plate and flange width reduces the
effectiveness of intermediate web stiffener for shorter members i.e. 0.5 and
2.0 m length of member and for larger length, intermediate web stiffener are
not effective and no effect of thickness and flange width has been observed.
Increase in depth of triangular, trapezoidal and quadrilateral intermediate
stiffener reduces the effectiveness of intermediate web stiffener after 6 mm.
Lip length up to 9 mm is effective for the length up to 2.5 m long member and
up to 6 mm for 3.0 m long member.