EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS Earthquake Engng Struct. Dyn. 2006; 35:1403–1424 Published online 19 June 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/eqe.589 Behaviour of the double concave Friction Pendulum bearing Daniel M. Fenz ‡, ¶ and Michael C. Constantinou ∗, †, § Department of Civil, Structural and Environmental Engineering, 212 Ketter Hall, State University of New York at Buffalo, Buffalo, NY 14260, U.S.A. SUMMARY The double concave Friction Pendulum (DCFP) bearing is an adaptation of the well-known single concave Friction Pendulum bearing. The principal benefit of the DCFP bearing is its capacity to accommodate substantially larger displacements compared to a traditional FP bearing of identical plan dimensions. Moreover, there is the capability to use sliding surfaces with varying radii of curvature and coefficients of friction, offering the designer greater flexibility to optimize performance. This paper describes the principles of operation of the bearing and presents the development of the force–displacement relationship based on considerations of equilibrium. The theoretical force–displacement relationship is then verified through characterization testing of bearings with sliding surfaces having the same and then different radii of curvature and coefficients of friction. Lastly, some practical considerations for analysis and design of DCFP bearings are presented. Copyright 2006 John Wiley & Sons, Ltd. Received 10 October 2005; Revised 19 February 2006; Accepted 11 April 2006 KEY WORDS: double concave Friction Pendulum bearing; seismic isolation 1. INTRODUCTION The double concave Friction Pendulum (DCFP) bearing consists of two facing concave stainless-steel surfaces. The upper and lower concave surfaces have radii of curvature R 1 and R 2 , respectively, which may be unequal. The coefficients of friction of the concave surfaces are  1 and  2 , respectively, which are also not necessarily equal. An articulated slider faced with a non-metallic sliding material separates the two surfaces. The articulation is necessary for proper ∗ Correspondence to: Michael C. Constantinou, Department of Civil, Structural and Environmental Engineering, 212 Ketter Hall, State University of New York at Buffalo, Buffalo, NY 14260, U.S.A. † E-mail: constan1@eng.buffalo.edu ‡ E-mail: dmfenz@buffalo.edu § Professor. ¶ Ph.D. Student. Contract/grant sponsor: Multidisciplinary Center for Earthquake Engineering Research; contract/grant number: 8.2.1 Copyright 2006 John Wiley & Sons, Ltd.