Keywords: post-buckling, shear strength, non-linear analysis, finite element analysis, tension field action, end-bearing stiffener.

In most classical failure theories for post-buckled web panels subjected to pure shear, it was assumed that diagonal tension strip was anchored by flanges and, or adjacent web panels. Such an assumption led to the conclusion that post-buckling strength can only develop in intermediate web panels. Accordingly, the AISC specification [1] does not account for post-buckling strength in proportioning end web panels.

In this paper the finite element analysis of end web panels was conducted using the general-purpose finite element software, ANSYS. All plate elements in a simply supported plate girder were modelled with the iso-parametric finite strain shell element, Shell 181. End-bearing and intermediate stiffeners were proportioned to satisfy area and inertia requirements stipulated by the AISC specifications. The finite element model was verified by comparing the elastic buckling load to classical theory [2] whereas ultimate load was compared to the test results on six plate girders published in the literature [3]. The computed elastic buckling load was bound by the theoretical buckling load assuming simply supported and fixed boundary conditions at the flanges. Unlike most post-buckling theories, the numerical solution revealed that end web panels developed a compressive stress field after buckling along the stiffeners and top flange to balance with the diagonal tension [4]. A portion of the diagonal tension was also supported by the end-bearing stiffener.

The effect of end-bearing stiffeners on the shear strength of end web panels was investigated. It was shown that single pair end-bearing stiffener increased significantly the shear strength of end-web panels compared to one-sided end-bearing stiffeners. On the other hand, no significant increase in the ultimate shear strength was noticed when a double end-bearing stiffener was used compared with a single pair end bearing stiffener. An extensive parametric analysis was conducted to investigate the effect of: web slenderness ratio, panel aspect ratio, inertia of intermediate stiffeners and ratio of flange to web thickness on the shear strength of end web panels stiffened with single pair end-bearing stiffener and one sided intermediate stiffeners. Numerical results for more than sixty plate girders were used to establish an expression for the elastic buckling coefficient, the post-buckling strength and the ultimate strength of transversally stiffened end web panels. The proposed expressions provided good estimates of the numerical results compared with AISC design rules.

1

American Institute of Steel Construction, "Specification for structural steel buildings, Load and Resistance Factor Design", AISC, Chicago, III, 2005.

2

S.P. Timoshenko, J.M. Gere, "Theory of elastic stability", 2nd Ed., McGraw-Hill Book Co., Inc., New York, N. Y., 1961.

3

S.C. Lee, C.H. Yoo, D.H. Yoon, "New Design Rule for Intermediate Transverse Stiffeners Attached to Web Panels", Journal of Structural Engineering, ASCE, 129, 1607-1614, 2003. doi:10.1061/(ASCE)0733-9445(2003)129:12(1607)

4

S.S. Safar, "Effect of Transverse Stiffeners on Shear Strength of Web Panels", International Bridge Conference, Pittsburgh, Pennsylvania, USA, IBC 11-32, 2011.

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