الفهرس | Only 14 pages are availabe for public view |
Abstract Composite steel box girder bridges represent the optimum system in many cases for short and middle span bridges. However, during construction, the open box steel girder is erected first and the concrete deck is added later. The open box section is relatively flexible in torsion. It has small stiffness against torsion compared with the stiffness of the closed box section after casting the concrete deck. A critical design stage for steel girder occurs during the construction phase, where its deformations and the corresponding stresses mcrease than safety values. Three dimensional finite element models are proposed and solved by program ANSYS-8. 0 to study the behavior of straight simple and continuous open box girder bridges consisting of steel girders with rectangular or trapezoidal cross section and two top flanges, during girder erection and bridge construction. The proposed finite element model has been verified by comparing its results, with the results of other models that have been investigated. A parametric study was carried to study the behavior of simple and continuous span open steel box girders for two main cases, without bracing and with different bracing systems due to torsional moment (concentrated and distributed) and vertical loads (symmetrical and asymmetrical). It was found that the classical method, which is used in the torsion analysis, is not recommended to determine the rotation angle of girder cross section about its axis in cases of girders with cross sections having shear center in direction and other cross section points in another direction, such as open box section. New equations are derived to determine the accurate values of the rotation angle for the top and bottom flanges for open box cross sections. The form of the classical method |