Analytical behavior of exposed base plates with extended anchor bolts

Abstract

This study investigates the behavior of a fixed exposed base plate connection with ductile behavior for special moment frame buildings. The base plate detail consists of a steel plate anchored to the concrete foundation through bolts extended to a steel chair (i.e., exposed bolts). This detail concentrates plastic strains mainly in the extended region of the anchor bolts, forcing the other connection components to remain elastic. While this base column connection has been extensively used in industrial facilities and is recommended in design codes, there is a lack of research on its cyclic behavior. A total of four 3D nonlinear FE models were created to characterize the key features of the connection. The models were validated against experimental data. Results indicate that the connection analyzed in this paper presents advantages over the traditional connection shown in the Design Guide 1. Plastic strains develop almost exclusively in the anchor rods, and no damage occurs at the remaining components. Another essential characteristic is the length of the exposed stretch, with which it is possible to achieve a target design rotation without significant strain concentrations in the anchor rods. This characteristic facilitates post-earthquake inspections and repairs, and damage is virtually eliminated in the first story columns.