The Behaviour Of Steel I-section Beams Curved In Plan And An Equation For Design

The theory of curved beams is not well established due to the complicated behavior of its mechanical characteristics. The comprehensive studies and experiments analysis about thin-walled curved beams in domestic are presented by Tong Genshu and Xu Qiang(2004) .This paper investigates the simple supported I-section beams curved in plane which subjects to a central concentrated load P acting at the shear center. Based on the liner elastic theories of Tong and Xu, it provides an equation to estimate the rotation angle at the central section by energy method. It also suggested an approximated equation to express the relationship among the bending moments in-plan and out of plan which are M_x,M_y, and the rotation angleθ. Moreover, on the basis of its mechanical characteristics, the three items equation is proposed to evaluate the stability strength of curved beams, including the bending moments in-plan and out of plan and the bimoments.Finite-element procedure (ANSYS 9.0) and element beam189 are used to investigate the load-deformation behavior and ultimate strength of curved beams subjected to a central concentrated load, taking into account the effects of large -displacement. Various cases are studied, including three developed lengths, two included angles and the same cross-section dimension. The rational numerical data indicates that the approximated theoretical equation about the relationship and the expression ofθare consistent with the FEM result, especially for the not unduly short curved beams. In addition, the bearing capacity of curved beams derived from this paper is compared with the existing results of experiments and design equations to verify the accuracy and validity. Comparisons with the large amounts of FEM results and the results of equations by other scholar have shown that the bearing capacity derived from the proposed equation provides a lower bound for the curved beams, especially for the beams with small curvature. As a result, the proposed equation is conservative to the strength and can be used in the structural design.