Behaviour of thin-walled structures under combined loads
The thesis is concerned with the theory of thin-walled beams of open section. The aim is to formulate a general beam element for analysis of this type of structure. Thus a general stiffness matrix for the element, and a transformation matrix for loads and displacements with respect to centroid and shear centre were derived, by taking into consideration the value of-bimoment due to an axial force offset from the shear centre. Internal forces including bimoments, and global displacements including warping were calculated, and the stress distributions on the cross-sections of a beam at each-element node, were evaluated. The problem of buckling of thin-walled beams was treated using a finite strip program which was formulated to solve problems with the following combination of stresses: a) Linearly distributed axial stresses b) Uniform lateral stresses c) Uniform shear streses The results for beams of cruciform, box and channel sections, under uniform axial stresses and linearly distributed axial stresses, also accounting for flexural stresses, were conpared with other theoretical and some experimental results. The agreement was satisfactory. A series of, laboratory tests on beams of channel sections under compression were carried out. The recorded failure load and critical buckling load, computed by the Southwell plot method, were compared with the finite strip results and satisfactory agreement was observed.