Stability Research Of The Emergency Beam In Monorail

ABSTRACT:Due to the properties:three sides loading, small curve radius and various linear of Monorail tracts, inverted T-shaped steel box girders are used for emergency beams. Based on the domestic and abroad researches, design rules and experiments, this paper investigate the stability issues in the design of emergency beams by theoretical and finite element analyses. The main works involved in this research are follows:(1) Lateral buckling as the controlling factor, the formulas used for calculating overall stability of emergency beams under different kinds of load were derived. The overall stabilities of the emergency beams with different radiuses were theoretically and numerically analyzed. The results showed that, the effect of radius on the critical buckling load was insignificant, and it can be calculated according to the characteristics of the buckling properties of linear beam.(2) A parametric study involving main factors which affect the lateral buckling of emergency beam was applied, and the formulas used for calculating critical values of the ratio (flange length/width, emergency beam) were deduced. So, the maximum ratios (span/width, emergency beam) under three kinds of load were presented for various emergency beams'cross-sections.(3) Based on the energy principle, the formulas used for calculating critical stress of elastic buckling of stiffened plates with unequal interval opening stiffeners were derived. The formulas were simplified later, regarding the stiffened plates with equal interval opening stiffeners as a special case.(4) Taking into account the actual position of the centroidal axis and tensional rigidity of the section, and considering the flexural rigidity of the stiffeners separately, the formula used for critical buckling stress of stiffened plates with unequal interval closed stiffeners was derived, using the energy theory. Comparing the current calculation methods of stiffened plates with trapezoidal stiffeners, the above formula can more accurately reflect the contribution of panels and stiffeners on bending stiffness of the cross-section.(5) Based on the elastic theory of stiffened plates, the main factors, which affect critical buckling stress of the stiffened plates with opening stiffeners and closed stiffeners, were parametric studied respectively. According to stiffened plates structures and force characteristics of the longitudinal stiffeners, the maximum limited sizes and reasonable stiffness formulas for opening stiffeners and closed stiffeners were derived.(6) Finite element models for the different size stiffened plates with rectangular stiffeners were established, for analyzing the welding residual stress of models. The factors which affect the residual stress profiles of the models were parametric studied. At last, the simplified diagrams for calculating residual stress profiles of the stiffened plates were presented.(7) Taking into account the material nonlinearly and geometric nonlinearity, and considering the initial geometric imperfections and residual stresses, the ultimate strength of stiffen plates with opening stiffeners and rectangular stiffeners, which are different on size, were analyzed by finite element models and, the factors affecting the ultimate strength were parametric studied.