טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMoshe Zelkha
SubjectSeismic Behavior of Cylindrical Water Tanks
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Emeritus Rutenberg Avigdor


Abstract

In section 105 of the Israeli standard, IS 413, “Design Provisions for Earthquake Resistance of Structures”, IS 413 classifies the structures, which are included. In the subsection dealing with tanks and silos the standard points out that the design should take into account the response of the tank’s content. Regarding the analysis for this design IS 413 directs the designer to the technical literature.

In Israel there are hundreds or even thousands liquid containing tanks (petroleum, water, etc’). The significance of water tanks, which are an essential component for water supply to the consumer, becomes a matter of special importance during an earthquake. Water supply structures are essential components for all services that must remain functional during an earthquake e.g. hospitals, first aid services and fire controlling services. During an earthquake a common hazard is fire, without a secured water supply the fire may cause substantially more damage than the earthquake itself, as occurred during the San Francisco earthquake in 1906. Failure of tanks with chemicals or petroleum could cause fire and pollution with destructive results in populated areas, as occurred during the Nigata and Alaska earthquakes in 1964.

The horizontal force acting during an earthquake is a significant factor in the design of the tank. The main challenge for the designer is to evaluate the hydrodynamic forces on the tank. The mechanism of the liquid response during an earthquake is characterized by two components. The first is the convective component, which activates in the upper region of the tank and is characterized by seismic waves or sloshing motion of the liquid. The second one is the impulsive component, which is near the tank base. In this area the liquid is confined between the tank’s walls and the liquid motion is in unison with the tank’s walls. The part of the liquid that acts as either impulsive or convective motion is determined by the geometry of the tank and by the ratio of the liquid height to the tank’s radius H/R.

The main purpose of this work is to enrich the knowledge on the response of cylindrical liquid tanks to earthquake excitation and, by doing so, to try and bring a useful and practical recommendation for the design of cylindrical liquid tanks that would match the seismic conditions in Israel.