Behavior and Design of an Adjustable Bolted Steel Plate Connection

This dissertation investigates a novel adjustable bolted steel plate connection to join steel members at a range of angles with the capability of adjusting in-situ to accommodate additional angles or tolerances by cold bending. The connection is comprised of prefabricated splice plates (cold bent via press brake) to defined angles, then further cold bent during field installation (by bolt tightening) to form moment-resisting joints. This approach uses a small number of prefabricated unique components to facilitate rapid erection. Analytical, numerical, and experimental approaches are utilized to (1) develop a versatile connection geometry for greatest adaptability to manufacturing and erection tolerances, as well as member dimensions, (2) understand the residual strains induced during prefabrication via press brake, (3) understand the effect of field installation via bolt tightening on the plates and bolts, (4) investigate the behavior of the connection under service and ultimate loads, and (5) develop recommendations on the design and behavior of adjustable connections. This is the first investigation of cold bending via bolt tightening for a kit-of-parts adjustable steel connection. Importantly, findings also offer insight into the behavior of bent connections, as well as misaligned or non-flush connections that are force-fit in the field.

Investigation of the prefabrication process found that the peak circumferential strain depends primarily on the ratio of plate thickness to bend radius. During investigation of the field installation procedure, the peak strain induced in the plates was found to depend primarily on the difference in ply angles (i.e., magnitude of bending). Overall, the field installation strains are significantly lower than prefabrication strains. The field installation process induces both axial and bending strain patterns in the bolts depending primarily on the bolt deformation demand. Ply angle deviations below 2.5 degrees are recommended. High bolt eccentricity / diameter ratios up to 0.3 were found to be acceptable with capacity reductions for slip and bolt shear. Measured peak loads for the adjustable bolted steel plate connection, for a failure mode of bolt shear, are found to be lower than a comparable straight and flush control scenario. These results indicate that the connection shows promise for future implementation with appropriate reduction factors applied.