Proceedings of the 1st Iberic Conference on Theoretical and Experimental Mechanics and Materials /

11th National Congress on Experimental Mechanics. Porto/Portugal 4-7 November 2018.

Ed. J.F. Silva Gomes. INEGI/FEUP (2018); ISBN: 978-989-20-8771-9; pp. 711-716.

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PAPER REF: 7330

EFFECT OF STIFFENING BEAMS ON SLOSHING OF LIQUID IN

CYLINDRICAL METALLIC TANKS

W. Samir Manser1, Mokhtar Touati

1(*), Rui C. Barros

2

1Civil Engineering Faculty, LBE, University of Sciences and Technology Houari Boumediene, Algiers, Algeria 2Civil Engineering Faculty, FEUP University, Porto, Portugal (*)

Email:touatimokh@yahoo.fr

ABSTRACT

Cylindrical metallic storage tanks are widely used structures in the field of civil engineering;

these installations are particularly used in industry where they are used to store all kinds of

products - most of them are toxic or flammable. The tanks are also used for municipal

purposes for the storage of drinking water. In earthquakes, these structures must be preserved

in order to avoid losing their precious contents, causing reactions that can cause more damage

that the earthquake itself.. In order to check the sloshing of the liquid, a study was carried out

to demonstrate the effect of reinforcement beams for different positioning and different inertia

of the beams. For numerical calculations, the ANSYS v11.0 software was used.

Keywords: Stiffening beams, cylindrical tanks, ANSYS, Finite Element Method.

IMPORTANCE OF LIMITING THE MAXIMUM SLOSHING WAVE HEIGHT

(MSWH)

Since the vertical movement of the convective liquid may lead to loss of the liquid contained

in the tank or damage to the roof of the reservoir, the MSWH must be taken into account

during the design and calculation of the tanks. There are a variety of standards for calculating

the liquid storage tanks resistance to the earthquake, these standards attempt to control the

liquid’s sloshing by predicting the MSWH values which constitute major parameters in the

calculation of these structures.

PURPOSE OF THE STUDY

Since cylindrical metallic storage tanks have relatively thin walls, their shells must have

sufficient thickness and rigidity to resist the hydrodynamic loads exerted by the liquid

contained in the excited tank.

The reinforcement of the shell in the radial direction by the introduction of the circumferential

reinforcing rings constitutes a real solution for limiting the response of the cylindrical shells

especially for the sloshing wave.

In this paper, the effect of the introduction of reinforcing rings on the response of cylindrical

metal water storage tanks to the base is studied while varying various parameters such as: the

height of the liquid HL, the inertia of The reinforcing ring ISR and the level of this ring ZSR.

For this purpose, transient non-linear dynamic analyzes of 100 tanks with a height of 10 m

and a similar radius are made using ANSYS v11.0 software to determine their dynamic

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responses to the earthquake used, the results are found and then interpreted in order to reach

concrete conclusions regarding the use of reinforcement rings to reduce the seismic response

of cylindrical tanks.

First, the tanks are simulated in the program ANSYS v11.0 Software using the finite element

method for the 3D modelling of the fluid-shell system. The properties of the materials were

assumed to be homogeneous.

Elements are selected to simulate a movement close to that of the system: liquid - shell: For

this, the shell was modelled by SHELL 63 elements, this 4 nodes element - have 6DDL at

each node, choice of This element was based on its flexural capacities as well as the ability to

accept loads in the plan and in the normal direction.

The tank was modelled by FLUID 80 elements: It is a solid three-dimensional element with 4

nodes having 3 translations in each node. The FLUID 80 has the ability to model contained

fluids producing hydrostatic and hydrodynamic pressures as well as fluid-structure

interaction.

Fig. 1 - The 3D modelisation of the system liquid -shell by ANSYS.

For the analysis, a Tabas earthquake recording with a PGA of 0.328 was used (Figure 2), only

the excitation in the horizontal direction UX was taken into account in the time-history

analysis in order to study the variation of The height of the MSWH during the earthquake.

Fig. - The Tabas earthquake‘s recording.

The nodes of the tank’s base are embedded on the periphery while the rest of the nodes are

simply pressed while those of the fluid are blocked only in the vertical direction. The finite

element model of one of the tanks simulated by ANSYS Software is shown in Figure 1. The

mesh used in all analyzes is (1*1) m2.

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SPECIFICATION OF THE TANKS STUDIED

The tanks studied, their properties and the level of stiffening rings (SR) are summarized in the

following tables:

Table 1 - SR at z = 10 m. Table 2 - SR at z = 8 m. Table 3 - SR at z = 6 m.

Table 4 - SR at z = 4 m. Table 5 - SR at z = 2 m.

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For this purpose, the inertia of the reinforcing beam was varied as follows:

UAP 1: UAP 100.

UAP 2: UAP 130.

UAP 3: UAP 150.

UAP 4: UAP 175.

UAP 5: UAP 200.

NUMERICAL RESULTS

The numerical results are obtained in Table 6.

Table 6 - Numerical Results.

CONCLUSION

In this work, we studied the effect of the introduction of the reinforcing beams in the

cylindrical metallic tanks on their seismic responses to an excitation at the base while varying

different parameters such as the height of the liquid, the level of the reinforcement ring and its

inertia. The study was performed by numerical means using the ANSYS v 11.0 software.

The maximum height of the sloshing wave, its values decrease with the increase in the inertia

of the reinforcing beam and reaches its minimum values when the level of the ring is close to

the total height of the tank. Concludes that lowering the values of the sloshing waves is

possible by placing the reinforcement system at the top of the tank.

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On the basis of the numerical results obtained by the previous study, it is recommended to

realize the reinforcing beams between the heights 0.4 H and 0.6 H for which the mode of

rupture (sloshing) is controlled.

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