The use of post-tensioning to reduce seismic damage in steel frames

Abstract

This chapter introduces a post-tensioned friction damped connection for earthquake resistant steel moment resisting frames (MRFs). The post-tensioned high strength strands run parallel to the beam and are anchored outside of the connection. Due to the initial post-tensioning force applied to the strands, the beam flanges are compressed against the column flanges. Friction devices are located at the beam flanges, consisting of a friction plate sandwiched by two brass shim plates that are inserted between the beam flange reinforcing plate and an outer plate. All plates are bolted to the beam flanges. Long slotted holes are drilled through the friction plate. The computer program DRAIN-2DX is used to develop a model of the post-tensioned friction damped moment connection (PFDC) and the associated beams and columns of the MRF. The beams and columns are modeled using fiber elements. Each fiber element is divided into a number of segments along the element length. The cross-section of each segment is comprised of several fibers. The analytical investigations indicate that moment resisting frames with PFDCs may perform better than moment resisting frames with conventional welded moment connections.