NEHRP Clearinghouse

Title
Closed-Loop Modal Testing of a 27-Story Reinforced Concrete Flat Plate-Core Building.
File
PB92129980.pdf
Author(s)
Somaprasad, H. R.; Toksoy, T.; Yoshiyuki, H.; Aktan, A. E.
Source
National Science Foundation, Washington, DC., July 15, 1991, 148 p.
Identifying Number(s)
NCEER-91-0016
Abstract
Modal testing of a 27-story reinforced concrete flat plate building with concrete cores was performed to identify a reliable analytical model. Closed-hoop modal tests were performed to acquire reliable data by utilizing a linear inertia-mass exciter capable of generating a higher level of force to overcome the influence of wind excitation. Furthermore, the level of force permitted the observation of rocking. Recently developed HP SINE signal processing software with an HP-3565S measurement hardware was utilized in a close-loop test setup to control the excitation and to acquire and process the data. The natural frequencies, damping, and modal vectors were determined by post processing the measured data. It was possible to determine the mass-orthonormal modal vectors and flexibility without assuming a mass matrix. The rotational flexibility of the core foundation due to rocking was also quantified. A comparison of the current and previous modal test results is presented. An increase in the level of excitation force resulted in variations in the dynamic characteristics and lateral flexibility of the building. The performance of the hardware and software and the difficulties encountered during the test are detailed in the report.
Keywords
Dynamic response; Signal processing; Buildings; Earthquake engineering; Data acquisition; Loads (Forces); Structural vibration; Foundations; Reinforced concrete; Vibration damping; Concrete structures; Resonant frequency; Structural analysis; Algorithms; Closed loop modal tests