Dynamic Characterization of Shock Table

Abstract

During earthquake structures experience base motion that has potential to damage structure to diferent degrees. Understanding dynamic response of structure to base motion is quite important. This is achieved by mounting scaled model of struc- tures on Shake Table capable of simulating earthquake scenario in the laboratory. However, such facility is quite costly from both development and operation point of view. Dynamic response of structure can, alternatively, be determined using Shock Table made of Reinforced Cement Concrete(R.C.C.), wherein impact of various de- grees are applied. It consists of a rigid platform mounted on wheels, with ability to move in one direction. The table can be set into to and fro motion through pen- dulum impacts on one side and rigid rebound beam on the opposite side of the table. Present study aim towards dynamic characterization of Shock Table in terms of Acceleration, Force and Dominant Frequency. An Experimental set-up consisting of Accelerometers, Data Acquisition System and Computer System and is integrated to capture dynamic response of the Shock Table. In order to validate experimental results, a Numerical solution using Finite Element (FE) analysis is carried out. FE model developed is analyzed using Transient Analysis through ANSYS software. Experimental results indicate that Shock Table can be subjected to Force of about 1500 kN with dominant frequency of about 1 Hz. This means that scale models with natural frequency around 1 Hz can be well excited on Shock Table. Acceleration of as high as 80 g is produced when Shock Table is subjected to an impact through Pendulum released by an angle of 40 . Loss of acceleration along the length of Shock Table is not very evident. There is some agreement as far as peak acceleration value is concern among experimental results and numerical results obtained through FE analysis. However complete time history derived through FE analysis do not match with time history captured experimentally.