Dynamic response of ground supported rectangular water tanks to earthquake excitation

Birhane Aregawi,Abdulaziz Kassahun

doi:10.4314/mejs.v9i1.5

Abstract

This study investigates an idealized ground supported reinforced concrete rectangular water tank under earthquake excitation. A linear three-dimensional finite element analysis and SAP2000 software have been used to predict tank response. The variable analysis parameters considered are the aspect ratio (tank height to length ratio) and tank water level, while the tank wall thickness is taken as a constant. The convective and impulsive masses are also represented by spring-mass model in the time history analysis for El-Centro earthquake ground motion record. Five tank models with a capacity of 216, 288, 360, 432 and 504 m3 were developed and analyzed for hydrodynamic and hydrostatic effects. In general the results show that, there is a smooth increase in the moment and displacement of both hydrostatic and hydrodynamic analysis with a decrease in aspect ratio. The top displacement and moment for the hydrodynamic effects are greater than the hydrostatic results and it is observed that the maximum hydrodynamic moment is 91.3% higher than the corresponding maximum hydrostatic moment. Likewise the displacement obtained from hydrodynamic analysis is 63.58% more than the corresponding hydrostatic value.Keywords: Hydrodynamic effect, Convective and Impulsive, Rectangular tanks, Finite Element Models, Time history, SAP2000, Ethiopia

Highlights

Storage tanks are used for storing water, inflammable liquids toxic materials and other petrochemicals
The results show that, there is a smooth increase in the moment and displacement of both hydrostatic and hydrodynamic analysis with a decrease in aspect ratio (A)
The results obtained based on dynamic analysis are critical for the design of such tank structures

Summary

INTRODUCTION

Storage tanks are used for storing water, inflammable liquids toxic materials and other petrochemicals. Using numerical methods for the rigorous evaluation of the dynamically induced stresses on the tank walls is found to be accurate approach as it involves the interaction between the lateral displacement of the tank and that of the fluid motion. Review of design Codes Some of the structural design codes that tackle fluid tank systems are the American Concrete Institute, ACI 350.3, the Euro Code 8 and the Standards Association of New Zealand, NZS These codes address ground supported circular and rectangular concrete tanks having fixed or flexible bases. This condition is relevant to this study; the aim of which is to create an idealized model suitable for representing the vibrating fluid tank system by a proper spring-mass system which considerably simplifies the interaction.

DESCRIPTION OF THE TANK STRUCTURE

FEM MODELING AND DETAILED DYNAMIC ANALYSIS

RESULTS AND DISCUSSION

CONCLUSION