عنوان مقاله [English]
Generally, beams are designed to withstand bending and shear stresses, in practice, as well as for local yielding or instability under load and lateral torsional buckling. Another type of instability has been observed as a mode of failure in steel beams under some circumferences, referred to as web sidesway buckling or tension flange instability in previous work and steel design
codes, and is related to the lateral movement of tension flanges and tension zones of the web with considerable reduction in the load bearing of the beam. Experimental and numerical work has been conducted for web sidesway buckling, mostly based on simple analytical, experimental or numerical models that provide a conservative estimate of the load capacity of beams.
In the present paper, a concise study has been carried out on the behavior and occurrence mechanism of this instability, which resulted in proposal of a one dimensional (skeletal) model to describe the instability. This model consists of a column and two tensile members, like cable, for restraining the lateral displacement of the column support. The stability analysis of the proposed model has been undertaken, and then the critical load of the model has been generalized to the real beam, which undergoes instability. The provided expression for the model is related to the parameters of the beam. Furthermore, some coefficients have been used to calibrate the proposed critical load, with respect to the numerical and experiments results of previous research.
Effective parameters, such as web thickness, end condition and the tension area of the web were included in the model expression. The proposed model predicts the occurrence of this phenomenon and the load capacity of beams under web sidesway buckling. Results were compared with previous experiments and numerical models and show the good accuracy of the model in load capacity estimation.