Prediction of yield strength and prying action of TOBs bolted arc-shaped endplate

Based on the component method, the structural behavior of the arc-shaped endplate in Thread-fixed One-side Bolts (TOBs) bolted beam to circular steel column joint is investigated through the bolted arc-shaped T-stub to a thick enough steel tube connection in this paper. To properly identify the load-carrying capacity of the arc-shaped T-stub connection, the tensile strength of the arc-shaped flange and the tensile strength of the TOBs are of interest. According to EC3, the tensile strength of the arc-shaped flange is determined by different yield line patterns. In addition, the prying action, which is defined as the ratio of the vertical bolt force to the external force at the yield state, should be taken into account to determine the tensile resistance of the TOBs for thin flange. To explore different yield line patterns and the prying action induced by arc-shaped flange, Finite Element models are developed and validated. Subsequently, comprehensive parametric studies are conducted on multiple parameters with the validated model, including the flange thickness, flange width, flange curvature, bolt layout, and bolt diameter. According to the analysis results, three different yield line patterns for arc-shaped flanges are cataloged, which are the corner yielding pattern, group end yielding pattern, and double curvature pattern. Corresponding design methods are proposed to estimate the tensile strength of the arc-shaped flange and the prying action induced by the arc-shaped flange which show an acceptable error with the Finite Element results.