Expanded polystyrene small-scale model for similitude studies of elevated water tank

Abstract

In June 2015, Malaysia was shocked by a strong earthquake in Sabah. Three years later, another earthquake of 5.2 magnitude occurred in the same area. These incidents have triggered structural engineers in Malaysia to consider seismic analysis during load calculation process during the analysis phase. A full-scale seismic test is often expensive and time-consuming to construct, while a small-scale test is found rather limited and the activities are still rare among local engineers. Most of the existing small-scale tests use the same material of reinforced concrete, which has nearly 10 times model in mass due to dynamic effect and dangerous to implement. In this study, the probability to replace the material used in full-scale testing with more suitable material with equivalent properties to concrete in small-scale testing is investigated. This is achieved by conducting a seismic performance study of an elevated water tank scale model using expanded polystyrene (EPS) material. EPS was selected as the material for this study since it has high compression and low tensile value. The main objective of this study is to obtain the dynamic characteristic and ultimate behaviour of a small-scale model made with EPS. To conduct this study, 10 experimental models with different heights, types of coated layers and reinforcements were considered to vary their stiffness. The material was tested using compression test and hysteresis test to acquire the E-value for the material. Then, the model was tested using the shaking table test and the response acceleration was recorded using accelerometers. The value of natural frequency and deformed shape of the experimental model were compared and verified against Finite Element Method (FEM) modal analysis by Autodesk Simulation Mechanical software. The results show that, among the 10 experimental models, the model with mortar and paint coated layers reinforced with 6 rods of 2 mm steel rods and 0.55 mm steel mesh demonstrated a good agreement in terms of natural frequency value compared to the FEM analysis. This study has proven that a proper setting of reinforcement of the small-scale model can lead to a better prediction of real seismic behaviour, thus offering an alternative material replacement for concrete that would aid time and cost savings.