Numerical and Experimental Studies of Self-Centering Post-Tensioned Steel Frames

Keywords: Numerical simulations.  Self-centering post-tensioned (SCPT) steel frames.  Steel moment-resisting frames (SMRF).  Retrofitting.  Hospitals.  Medical care facilities.  Relative performance index (RPI).  Shaking table tests.  Floor displacement.  Floor acceleration.  Beam-column connections.  Yield.  Sacrificial devices.

Abstract: This report presents a numerical and experimental study to evaluate and compare the seismic performance of Self-Centering Post-Tensioned (SCPT) steel frames and conventional Steel Moment Resisting Frames (SMRF).  A methodology for designing SCPT structures is developed and used to retrofit an existing four-story SMRF medical facility located in Northridge, California.  A Relative Performance Index (RPI) is proposed to compare the enhancement in the seismic response of SCPT’s to the SMRF’s.  Numerical simulations and shake table tests were carried out on two scaled 3-story 2-bay SCPT and SMRF building prototypes based on the medical facility.  The study indicates that the seismic floor displacements of SCPT and SMRF are alike, while absolute floor accelerations are lower when self centering systems are implemented.  Moreover, while yielding in the beam-to-column connections of the SMRF are observed, only yielding of the sacrificial devices in the self centering system of the SCPT occurred during the strongest ground motions considered.