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Results of Millikan Library Forced Vibration Testing

Bradford, Samuel Case and Clinton, John F. and Favela, J. and Heaton, T. H. (2004) Results of Millikan Library Forced Vibration Testing. California Institute of Technology . http://resolver.caltech.edu/CaltechEERL:EERL-2004-03

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Abstract

This report documents an investigation into the dynamic properties of Millikan Library under forced excitation. On July 10, 2002, we performed frequency sweeps from 1 Hz to 9.7 Hz in both the East-West (E-W) and North-South (N-S) directions using a roof level vibration generator. Natural frequencies were identified at 1.14 Hz (E-W fundamental mode), 1.67 Hz (N-S fundamental mode), 2.38 Hz (Torsional fundamental mode), 4.93 Hz (1st E-Wovertone), 6.57 Hz (1st Torsional overtone), 7.22 Hz (1st N-S overtone), and at 7.83 Hz (2nd E-Wovertone). The damping was estimated at 2.28% for the fundamental E-W mode and 2.39% for the N-S fundamental mode. On August 28, 2002, a modal analysis of each natural frequency was performed using the dense instrumentation network located in the building. For both the E-W and N-S fundamental modes, we observe a nearly linear increase in displacement with height, except at the ground floor which appears to act as a hinge. We observed little basement movement for the E-W mode, while in the N-S mode 30% of the roof displacement was due to basement rocking and translation. Both the E-W and N-S fundamental modes are best modeled by the first mode of a theoretical bending beam. The higher modes are more complex and not well represented by a simple structural system.


Item Type:Report or Paper (Technical Report)
Group:Earthquake Engineering Research Laboratory
Record Number:CaltechEERL:EERL-2004-03
Persistent URL:http://resolver.caltech.edu/CaltechEERL:EERL-2004-03
Usage Policy:You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format.
ID Code:26542
Collection:CaltechEERL
Deposited By: Imported from CaltechEERL
Deposited On:19 Feb 2008
Last Modified:26 Dec 2012 14:00

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