03.18: Anchor bolt tensile load distribution: Effects of the column base‐plate design: Wide flange column bases – loading on additional line of bolts

Abstract

ABSTRACTThe designer of column base elements usually considers that the uplift force existing in the column member is equally distributed on its anchor bolts. While this simplified approach may be used for the most common cases of a steel structures (for instance, when only 4 equally spaced anchor bolts exist in the column base design), it may lead the designer to overlook that the distribution of uplift loads is highly influenced by factors such as the rigidity of the base plate, the positioning of its stiffeners and the number and geometric arrangement of the anchor bolts. This unequal distribution of uplift loads on the anchor bolts may cause overloading on some of the anchor bolts, leading to diverting failure. This paper analyses through finite element several different wide‐flange column base elements, with varying plate thicknesses and geometry. The conclusion summarizes that the distribution of the loads on the anchor bolts largely depend on the typology of the base plate and suggests a revision of the codes to be more precise on when unequal axial tensile loads may arise on the anchor bolts and recommend more refined methods for the estimation of those unequally distributed loads.