Author(s)

M. Sarkisian, P. Lee, E. Long, D. Shook & A. Díaz

Abstract

Seismic isolation shines as the top performance system for earthquake resistant structures, having involved a large variety of essential facilities since the late 1980s. Within the available devices, friction pendulum bearings present beneficial dynamic characteristics which are not intrinsically provided by other isolation systems. Developed and engineered by Earthquake Protection Systems, Inc. in California, these bearings have become a popular choice for designers. This paper firstly presents the experience of Skidmore, Owings & Merrill LLP (SOM) on the design of friction pendulum base isolated buildings, with systems evolving from the single concave to the Triple Friction PendulumTM (TFP) bearing and with a corresponding history of isolator displacement and base shear demands. The discussion is followed by a case study on a TFP system, in which the client is not only provided with a high performance structure tuned to experience low damage for design earthquake events, but also a more flexible interior unit layout given the reduction on shear wall requirements. Advanced modeling of the bearings and calibration of the design properties are discussed from a practical standpoint, including adjustment of friction coefficients and curvature radii to meet isolator displacement demands and minimum base shear requirements in compliance with the American Standard ASCE 7. Specific issues addressed during the design process and in response to state-of-the-art discussions with the Peer Review Panel, such as the effect of the stiffening range of the bearings or the consideration of rotational ground motion components, are described in depth. Keywords: enhanced seismic systems, base isolation, Triple Friction Pendulum, performance-based design, rotational ground motions.

Keywords

enhanced seismic systems, base isolation, Triple Friction Pendulum, performance-based design, rotational ground motions