Behavior of Steel Drop-In Connections Evaluated Utilizing Digital Image Correlation

Abstract

A safer and more efficient drop-in shear connection (compared to conventional shear tab and double angle connections) has been proposed for implementation in the commercial and residential steel frame building industry. This effort is part of the American Institute of Steel Construction’s (AISC’s) Need for Speed Initiative to reduce the steel construction cycle by 50%. The objective of this thesis is to aid in the development of a future design process for the proposed connection by evaluating the behavior of its various components, specifically the connection angles, girder top flange, and column web, through full-scale testing. Eleven various drop-in connections were tested in realistic girder-to-column and beam-to-column test setups at Auburn University’s Advanced Structural Engineering Laboratory. Six girder top flanges and eight angles were observed and analyzed utilizing Digital Image Correlation (DIC), an established optical technique that allows for the visualization of complete strain fields on a specimen’s surface. As well, two-column webs were observed via DIC for a typical one-sided beam-to-column connection, like that which is utilized for an exterior beam in a building. Testing revealed various ductile failure modes, such as transverse and longitudinal bending of the girder’s top flange, allowing for large plastic deformations to occur before ultimate failure. It was determined, through surface strains observed on the vertical angle legs, that the current AISC equation to determine single-angle leg shear strength would be adequate for the design of the tested connection angles. Finally, when utilizing a one-sided beam-to column connection in which the angles are attached to the column web, plastic deformation of the web may occur and should be checked.