Journal of Constructional Steel Research 58 (2002) 565–604 www.elsevier.com/locate/jcsr Development of improved welded moment connections for earthquake-resistant design J.M. Ricles a * , J.W. Fisher a , Le-Wu Lu a , E.J. Kaufmann b a Department of Civil and Environmental Engineering, Lehigh University, 117 ATLSS Drive, Bethlehem PA 18015-4729 USA b ATLSS Engineering Research Center, Lehigh University, 117 ATLSS Drive, Bethlehem PA 18015- 4729, USA Received 15 May 2001; received in revised form 16 August 2001; accepted 19 October 2001 Abstract A comprehensive research program was conducted at Lehigh University to investigate the causes of brittle failures observed in numerous welded connections during the 1994 Northridge earthquake and ways to improve their ductility. In this program, tests on pre-Northridge con- nection details demonstrate that several weak links in the connection design and fabrication resulted in their premature failures. To develop improved details for welded unreinforced con- nections the effects of weld metal, weld access hole geometry, beam web attachment, conti- nuity plates, and panel zone strength on cyclic ductility were investigated using non-linear finite element models and full-scale connection tests. The results from these studies are presented, along with recommendations to insure ductile connection performance.  2002 Elsevier Science Ltd. All rights reserved. Keywords: Beam web attachment; Complete joint penetration groove welds; Continuity plates; Ductility; Finite element analysis; Full-scale test; Fracture; Inelastic rotation; Notch toughness; Panel zone; Seismic- resistant design; Steel moment-resisting frame; Weld access hole; Weld metal; Welded moment connec- tion * Corresponding author. E-mail address: jmr5@lehigh.edu (J.M. Ricles). 0143-974X/02/$ - see front matter  2002 Elsevier Science Ltd. All rights reserved. PII:S0143-974X(01)00095-5