The shake table rig with base displacement measurement allows advanced analysis of the behaviour of a building during an earthquake. The rig emulates a 2-storey building, with base excitation being provided by an electric motor.
This improved version of the shaker table rig builds on feedback taken from Professor Mike Davis (UTas) to add additional sensing capabilities to the model building. With the addition of a high-precision Linear Variable Differential Transformer (LVDT), the amplitude and frequency of the base excitation can be measured in real-time. Further improvements were made in software, with the addition of real-time Fast Fourier Analysis and Lissajous Curve generation. These tools allow students to conduct more detailed analysis of the behaviour of the structure at resonant frequencies.
The rig consists of a 2-level building model where each storey is represented by a known mass. The levels are linked by strips of spring steel with known stiffness coefficients. The model can be excited by a pure sine wave through the use of an electric motor and scotch yoke mechanism (which converts rotational motion into linear motion). The frequency of excitation can be controlled by the user, with the resulting displacements measured by linear displacement sensors, plotted in real-time on the user interface. Users can additionally control specialised eddy-current coil dampers, either by applying a fixed (user-adjustable) damping force or through closed-loop control (PI controller), where the coefficients can be adjusted by the user.
All data measured by the system, including displacement, damping level and FFT plots can be downloaded for later analysis by the user. As a result, students are able to easily and effectively use the shake table rig to characterise a real, physical structure and determine the optimal parameters for inciting resonance as well as eliminating it through the application of dampers.