Branch Plate-to-Circular Hollow Structural Section Connections. II: X-Type Parametric Numerical Study and Design

This paper presents a numerical finite-element parametric study on the behavior of transverse or longitudinal X-type plate-to-circular hollow section connections loaded under branch plate tension or compression, to evaluate the suitability of present international (CIDECT) design recommendations, the effect of boundary conditions and chord length, and the influence of applied chord normal stress. A total of 449 connections with wide-ranging values of geometric properties and chord normal stress levels were modeled and analyzed using commercially available software. An analysis of the effect of chord length determined that, to exclude the influence of chord end boundary conditions, an effective chord length of at least 10 times the chord diameter should be used for experimental and numerical studies. Further, the present CIDECT chord stress functions (Q(f)) provide an acceptable lower bound for all connections examined. Evaluation of present CIDECT partial design strength functions (Q(u)) indicated general conservatism, lack of plate thickness incorporation, and underutilization of tension-only connections. Partial design strength functions, determined through regression analysis, are hence proposed with lower-bound reduction (resistance) factors. DOI: 10.1061/(ASCE)ST.1943-541X.0000545. (C) 2012 American Society of Civil Engineers.