Based on the displacement variational principle and the strain-displacement relations of curved beams, the paper presents some fundamental nonlinear equations that describe the elastic behavior of thin-walled curved beams. The lateral buckling of thin-walled curved members with shear lag is analyzed. A transformed B3 spline function is used to simulate the warping displacements of the thin-walled curved beams. The stability of the simple beams with I-shaped cross sections is studied. The method is shown to be versatile, accurate and efficient.

The eccentrically compressed reinforced concrete members heated on three faces are loaded in different conditions,namely the after heating, after two hours of high temperature maintenance and after cooling. The behavior, including failure patterns, ultimate load capacity and deformation have been investigated and analyzed. The test result shows that the members are damaged heavily under high temperature, but the behavior of the members after cooling are less different from that under high temperature, while the members loaded after two hours of high temperature maintenance are damaged much more seriously.