Research on stressed behavior of open thin-walled steel girders of curved composite beams stiffened by diaphragms in construction stage

For the curved composite beam stiffened by diaphragms, the bearing structure in the construction stage is the open thin-walled steel girder. In order to reveal its behavior, taking the diaphragm's number and span-radius ratio as parameters, model tests were conducted on five curved open thin-walled steel girders during the process of casting concrete. On the basis of the M/r method, the stressed behaviors of curved open thin-walled steel girders under the wet height of concrete were analyzed with Software ANSYS. The analysis results indicate as follows: Under the action of loading of wet concrete, the vertical displacement, radial displacement, tangential stress and the ratio of wrap stress to bending stress all increase linearly with increasing of the span-radius ratio and decrease nonlinearly with increasing of the diaphragm's number N, and the changing amplitudes are large when N being in the range from 0 to 3 and are small when N≥5; the end diaphragms and middle diaphragm have the most great effect on the bending-torsion behavior of the curved steel girder; the span-radius ratio is a dominant index to reflect the torsion level of the curved open thin-walled steel girders, and the layout of diaphragms in the curved open steel girder should be determined according to the ratio of wrap stress to bending stress and with reference to the span-radius ratio.