Civil structures such as buildings, bridges and skyscrapers are constructed in different shapes and sizes, structural design, materials of construction and their foundation and land characteristics. These different attributes affect how structures perform under high external loads and excitations such as earthquakes and strong winds. Structures experience deformations after being hit by earthquake, structural engineers should be able to detect the structural defects of the building and determine if the building needs repairs and if so to what extent. Structural engineers need to accurately assess the health of the building and decide how much longer the building can sustain itself without requiring any repairs. This is where the concept of structural health monitoring(SHM) is introduced. SHM assists in predicting when the structures are going to collapse, so catastrophic failure can be avoided and the overall safety of the people and the structures can be ensured.

In order to achieve meaningful and reliable results in performing dynamic tests with a shake table, the accurate reproduction of commanded dynamic signal (earthquake ground motion) is important. Two types of seismic ground motion data are used for the seismic analysis of the structures. Data in deterministic form are used to design the structures whereas data in probabilistic form are used for seismic analysis, study of structures and damage assessment of structures under particular earthquake ground motion.

After setting up the shaking table, building model and response measurement, structural analysis and structural modelling can be conducted on the system. Structure under the dynamic loading cannot be analysed by static analysis therefore, dynamic analysis is essential for dynamic loading. There are three different components that govern the dynamic analysis; stiffness, damping ratio and mass of structure. Without these basic components it is impossible to analyse the dynamic system.  In this project dynamic analysis is mainly focused on lateral forces (earthquake force) only. Simple dynamic system can be calculated manually but for complex problems finite element analysis can be used to determine modes and frequencies. Modal analysis is the study of dynamic properties of structure under external excitation. It uses mass and stiffness to find the various periods of vibration at which the structure will resonate. If the vibration of structure and vibration of external force are same, the structure will resonate and serious damage occurred to the structure. Dynamic systems can be modelled and analysed to predicts the performance of dynamic system operating under the specified environmental condition.

A low cost shake table with Arduino microcontroller board has been developed for earthquake simulations. The horizontal components of acceleration records obtained from past earthquakes are scaled and transferred to the shake table by developing software using Arduino DUE board. For verification, the responses of the table are measured by a data acquisition unit based on the Arduino MEGA board. The seismic ground motion along the horizontal axis is transferred to the shake table through a linear bearing system and stepper motor.

The concept of belt and pulley system is used in designing the motion system of the shake table. The rotation of the pulley is in turn controlled by the number of steps in the stepper motor. These stepper motors produce more forces and rpm which makes it easier to conduct dynamic experiments. The belt and pulley concept helps to convert the motion of stepper motor to the linear motion

After the construction of the shake table and building model with bracing and without bracing system are completed.  Building models are kept at the top of the shake table. Various signals of 2015 Gorkha earthquake were sent to stepper drivers which eventually rotate the stepper motor. A belt and pulley system is used in the designed system which converts the rotation of the stepper motor to linear motion. Data acquisition systems record the responses of the dynamic motion.

Stepper motors are powered up by an external DC source. There is a module which acts as a controller connected to the computer. It will ultimately control the stepper motor through the computer. The stepper drives which are connected to the stepper motor that acts to translate the signal from the module into the signal that the motor can understand.When the user sends earthquake signal through software, module receives it and then send it to the stepper driver which will then notify the motor what to do (e.g. turn 150 steps in clockwise direction) single motor will create unidirectional motion in the shaking table and the motion of the system represents an earthquake. While the building model is subjected to earthquake motion, acceleration and deflection data will be collected for analysis using structural dynamics.

• The vibrations generated during an earthquake will travel in all possible directions but to study vibration effects in all directions will be a very tedious task therefore, a setup which generates unidirectional excitations (i.e. horizontal direction) is constructed. Multicomponent shake tables require special knowledge and experiences which are not economical. Thus a small sized, unidirectional shake table is used for our research project.
• The scope of this project is beyond the field of civil engineering because the project team had to assemble, configure and control various electrical devices like stepper drives, motors etc. also, knowledge of programming language is required to develop testing setup and collect appropriate data.

The exact environment condition cannot be created at the laboratory which may makes slight deviation in the final results.