Dynamic Stiffness and Vibration of Reinforced Concrete Beams


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Title: Dynamic Stiffness and Vibration of Reinforced Concrete Beams

Author(s): Sukhvarsh Jerath and Milad M. Shibani

Publication: Journal Proceedings

Volume: 82

Issue: 2

Appears on pages(s): 196-202

Keywords: beams (supports); deflection; dynamic characteristics; dynamic loads; moments of inertia; reinforced concrete; resonant frequency; rigidity;stiffness; structural analysis; structural design; vibration.

Date: 3/1/1985

It is necessary to know the stiffness rigidity of concrete structures to calculate their response to a dynamic load. The natural period of vibration and static deflection of six reinforced concrete beams on simple supports were measured for different loads, and the natural frequency and stiffness rigidity under dynamic excitation were calculated from these readings. The effect of reinforcement was tested using singly and doubly reinforced concrete beams with different amounts of reinforcement. The effective moment of inertia I,, calcu-ated from ACI Standard 318-83 can be used for finding static de-flections but may not be correct for determining the stiffness rigidity of reinforced concrete beams under dynamic excitation. There is a need to develop a formula similar to the CI 318-83 expression for Ieff which can be used for calculating dynamic stiffness. On the basis of the limited number of tests performed, an equation for dynamic stiffness is proposed.