Description

Field of the Invention

The technical background of this design is related to designing security systems of structures (civil) and liquid storage repository (including oil, natural liquid gas, water and etc)

Problems found in previous methods

Liquid storage tanks include important structures in vital artery networks which their destruction during earthquake will lead to undesired economical, environmental and safety consequences. Moreover, liquid storage tanks will play a major role in meeting essential requirements of people after earthquake. Therefore, applying some methods for reducing seismic response of liquid storage tanks is considered as a critical action to control the damages caused by the earthquake.

To generalize, the damages caused by earthquake in liquid storage tanks can be summarized in the following types:

1- Buckling of tank wall as a result of hydrodynamic powers caused by the interaction of liquid and structure

2- Destruction as a result of wavy motion of fluid during the earthquake and its collision with the ceiling and the upper parts of the tank wall.

3- Liquid leakage from the tank because of high circular tensions in joints

4- The rise of tank from the wall (for uncontrolled tanks)

5- The buckling of central stable columns which are used to hold the ceiling. 6- Lateral movement of tank structure (not using flexible joints in the joining points of the tank and pipes where the liquid enters and exists may cause tearing in the wall sheet or destroy the tank accessories.

The major problem in running isolator system to strengthen the tanks against earthquake is the high cost and long time it takes to use the isolator in the current method. In the present design, the isolators are extended and installed under the tank for each one meter. It means that if we consider radius of tank floor to be 8 meters, then we need 200 isolators to keep the tank safe against the earthquake. Another costly action is required which is making a rigid concrete bed as high as 1 meter under the tank.

The number of projects exerted for dividing the storage tanks is restricted to fewer than 5 cases worldwide. This is an evidence of not welcoming this method.

Description of the Prior

The only innovation to reduce the seismic response of liquid storage tanks during the earthquake is using isolators which as mentioned above have not been welcomed for some reasons.

Brief description of figure:

Fig. 1 is a cross-sectional view of the tank.

Fig. 2 is a top view of the tank.

Description of Invention

We have been able to improve the seismic behavior of tanks by changing the layout of isolators. As it is obvious in the figures, in this design, tank floor 1 is installed without rigid concrete bed, and around the tank 2 a concrete ring 3 as thick as one meter is created. This ring is used for installing isolator connectors 4.

One isolator is installed in the outside layer 5 of tank every five meters. The isolators are installed exactly in the middle of the concrete ring 6. As it is seen in the figure 1, the isolators are installed below the outside layer of tank 7 body shell.

Joining tank shell to its floor is done through the Geomembrane 8 layer which is reactionary. Consequently, in the case of an earthquake, the tank moves to the sides by Geomembrane layers and it is controlled by the isolators. This movement causes significant reduction in total bending and cutting and the height of liquid compared to the available methods.

Clear and precise explanation of advantages of the claimed invention

1- A significant fall in the cost of project running

2- percentage of effective influence on the main seismic factors

3- potentiality of its execution on the available tanks

4- higher speed in project running

Explicit statement of application

Using this invention can sharply reduce the probable damages to the tank (more than 80 percent) for the tanks that are under construction and also the available tanks which are placed in the areas which require seismic calculation.

Explaining at least one executive method for applying this invention

While designing and installing liquid storage tanks, tank environment is made of ring concrete as thick as 1 meter and one isolator is installed every 5 meter. Then the shell is joined to the tank floor by geomembrane layer which is reactionary.