13 th World Conference on Earthquake Engineering Vancouver, B.C., Canada August 1-6, 2004 Paper No. 1603 SEISMIC RESPONSE AND DESIGN OF POST-TENSIONED STEEL MOMENT RESISTING FRAMES WITH FRICTION COMPONENTS Pedro ROJAS 1 , James M. RICLES 2 , and Richard SAUSE 3 SUMMARY A post-tensioned friction damped connection (PFDC) for earthquake resistant steel moment resisting frames (MRFs) is introduced. The connection includes friction components on the beam flanges with post-tensioned (PT) high strength strands running parallel to the beam. The connection minimizes inelastic deformation to the connection components and requires no field welding. Nonlinear analyses were performed on a 6-story, 4-bay steel MRF with PFDCs to study its response to strong ground shaking. A performance based design approach was developed to design the PFDC-MRF. The results demonstrate that the seismic performance of a PFDC-MRF is satisfactory in terms of strength, energy dissipation, deformation, and self-centering capability. The analysis indicate that the seismic performance of a PFDC frame can exceed that of a frame with conventional moment resisting connections. INTRODUCTION During the 1994 Northridge Earthquake, many steel-framed buildings suffered unexpected premature fractures in their welded beam-to-column connections. The occurrence of these premature fractures forced the engineering community to revise design and construction practice. Recent research has provided new details for MRF construction, but these new details are expensive to fabricate. Moreover, the use of the standard MRF connection often results in damage and permanent drift in the MRF following a major earthquake. As an alternative to welded construction, a post-tensioned friction damped connection (PFDC) for use in seismic resistant steel MRFs was developed. The connection utilizes high strength steel strands (Figure 1(a)) that are post-tensioned after the friction components are installed. The post-tensioning strands run through the column, and are anchored outside the connection region (Figure 1(b)). A properly designed PFDC has several advantages: (1) field welding is not required; (2) the connection is made with conventional materials and skills; (3) the connection has an initial stiffness similar to that of a typical 1 Professor, Catholic University, Ecuador, per2@ecua.net.ec 2 Professor, Lehigh University, jmr5@lehigh.edu 3 Professor, Lehigh University, rs0c@lehigh.edu