NONLINEAR FINITE ELEMENT ANALYSIS OF THIN-WALLED STEEL TUBE AND CONCRETE-FILLED STEEL TUBE (CFT) COLUMNS

Thin-walled structural members have the ability to resist high tension and bending
forces. At the same time, steel members can carry the compression force. For those
reasons the engineers started extensively using the cold-formed steel members in
construction industry, especially in light-weight buildings. Physical experiments are
relatively time consuming. Therefore, finite element analysis (FEA) plays a
significant part in practices of engineering. In the finite element model, measuring
the primary geometric insufficiency, dimensions of cross-section and properties of
materials must be taken in account. In this research a non-linear FEM (included nonlinearities
of material and geometric) has been used. The FEM results that obtained
from ANSYS.15 software were compared against the results that obtained from
experiments or codes-design. The results of failure modes and ultimate loads for
columns have been predicted and obtained by using finite element model of
ANSYS.15 software. Also, the parametric study of cross-section has been used in
analysis of FEM for columns with different heights. The strengths of channel
columns that obtained from experiment have been compared against the results that
calculated using BS5950 code and obtained from ANSYS.15. On the other hand, the
strengths of hollow circular and box columns that obtained from ANSYS.15 software
have been compared against the results that calculated using BS5950 code. Also
concrete is considered as brittle material. So, an application of thin walled steel
jacketing around the concrete is a best solution with a view to improve and increase
the ductility and strength of concrete. The study of FEA is used to check the
strengths and buckling behavior of fixed-ended thin walled plain hollow circular, box
and channel cross-sections columns and also concrete-filled steel tube (CFT) column.
Also to strengthen the concrete columns by applying thin walled steel jacketing
around columns. The results also showed that application of steel tube jacketing in
CFT composite columns mitigates the concrete cracks and also increases the stiffness
and strength of the columns.