and building of
steel construction of the tank can not be done without taking into
relation between upper steel construction and soil basement.
of coefficient of the bed Kb
in solution of contact problem in the joint shell - bottom is not sufficient.The
badly designed or
badly executed foundations can cause failure condition of the tank and
it can lead to differential settlement. Welded spatial constructions
walls are flexible and they are very sensitive to the settlement.
1. Shape of the bottom
a) cone up bottom
This is more often used bottom shape. It allows water drains from
of the tank to the situated near to the shell draw-off sump. The
atmospheric waters do not move
toward to the center of the tank and are not kept bellow the bottom.
This type of bottom is applied when the tank often must be emptied /
Value of the slope is the same as the slope of the cone up bottom. It
full drain of the water dropped inside in the tank and minimal contact
between the water inside and the bottom. One of the weaknesses is the
possibility for keeping and storing the atmospheric water felt below
bottom. Outside water can move to the center and increase the speed of
bottom without slope
It can be applied in the small tanks where the removing of the water
dropped inside into the tank is not required.
d) flat bottom with single slope.
Can be applied where the diameter D ≤ 30 m. This type of
foundation and the construction of the shell must assure its vertical
2. Type of foundation construction
a) foundation from compacted soil (earth type foundation).
This is most often applied scheme of foundation construction because it
is cheapest and easiest for execution. It is made according to the
in standard API 650. It is used when the soil can bear the pressure of the
construction and when the anchorage is not necessary. Even when there
leak moving out of the soil is possible. It can leads to
destruction of the tank. In this reason the diameter of the tank must
than the diameter of the tank with not less then 1,8 m. Earth
type foundation does not allow good leveling of the bottom i.e. of
the shell of the tank. When they are used it is possible the uneven
which cause additional efforts in the tank's elements.
Earth type foundation
b) reinforced concrete ring which is not placed
under the shell.
The tanks which are subject of this research
are the above ground facilities. They are placed on 0,3 ÷1,2 m above the
soil. This level difference is remarkable in the fuel
oil tanks where pump always must be under the liquids (Δh ≥ 0,7m). If
classical earth type foundation reaches this height the facility must
remarkable surface on the site. The reinforcing of such different
surfaces bears a risk for landslide (when the earth is covered by grass
asphalt) or it is slow, expensive and work consuming process (when the
In order to avoid this inconvenience appears the
idea of small foundation ring between the ground and the bottom level
ring is a combination free sand pillow and reinforced concrete ring in
periphery. The proposed construction is similar to the API Std. 650,
foundation ring is moved in the outside direction where it can not be
influenced of the load of the shell and the tank roof upon it. When
soil settlement under the tank, the reinforced concrete ring does not
full drain of the water so that this solution is unfortunate. It should not be applied to
Reinforced concrete ringwall foundation which
is not placed under the shell
c) reinforced concrete ring wall foundation.
The trend in the tanks building shows that the
volumes of the facility increase. Spatial steel construction of the
stands more flexible. In this reason bigger attention must be paid to
settlement and to the prevention measures. The use of the rigid
concrete ring increase around the world. When the tanks are bigger
dimensions of the rings are: largeness not less then 0,6 m and height
1,5 – 2,0 m.This type foundation construction allows very
good leveling of the periphery of the bottom and the shell which is
on it. The uneven settlement of the tank is limited. It is possible
be put there.
Reinforced concrete ringwall foundation
d) reinforced concrete slab
They could be applied when the tanks are relatively
small because this type of foundations is very expensive.
Thick concrete slabs are more favorable for upper
steel structure. They do not allow the uneven settlement of the tank.
concrete slabs are very recommendable when the level of the underground
Reinforced concrete slab
The special foundation constructions as the foundation
in the weak soil must be executed according to the concrete projects
technical and economical analysis made on the ground of results of the
geological and engineer research.