JPS5924955B2 - flat bottom cylindrical tank - Google Patents

Description

[Detailed Description of the Invention] <Explanation of the Summary> The present invention relates to a flat-bottomed cylindrical tank in which the earthquake resistance of the flat-bottomed cylindrical tank is increased by reinforcing an integral annular plate at the lower end of the side plate of the tank. In particular, the invention relates to a flat-bottomed cylindrical tank in which an annular girder is fixed to the upper surface of the annular plate to reinforce the annular plate, thereby increasing the second moment of area in the circumferential direction of the annular plate.

<Theoretical Background of the Invention> The theoretical background of the invention will be disclosed as follows.

As is well known, in a liquid storage tank 1 as shown in FIG. 1, the side plate 2 is generally subjected to a static load s in the horizontal direction due to hydraulic pressure.

On the other hand, when subjected to lateral vibration due to an earthquake, etc., the side plate 2 is affected by the weight of the tank 1 against the seismic force E, the inertial horizontal force of incidental equipment, etc., and the reaction of the stored liquid against the lateral vibration, as shown in Figure 2. The dynamic horizontal force H is applied to tank 1 by the total multiplication of dynamic liquid pressure due to deflection through inertial motion, and in the case of double-shell low-temperature tanks, inertial horizontal force due to insulation materials, etc. The load distribution is as shown in FIG.

The total force is as shown in Figure 3, which is the horizontal force H
This acts as the overturning moment of inertia M for the tank.
Here, regarding the static load s, as shown in Fig. 4, deformation occurs at the joint between the lower part of the tank side plate 2 and the bottom 3, and in the vicinity thereof due to the combination of the different shapes of the cylinder and the flat plate. occurs,
The load distribution is as shown in Figures 5 and 6, for example, the side plate 2
In the vicinity of the bottom joint, the vertical film force Ns and the static load s
A radial shearing force Qs generated by a restraining shearing force Qo by the bottom plate 3 of the side plate 2 and a bending moment M corresponding to the restraining bending moment Mo by the bottom plate 3 of the side plate 2
receive s.

Further, the bottom plate 3 connected to the side plate 2 is loaded with a reaction force Mo' to the above-mentioned Mo and a reaction force Qo' to the Qo.

On the other hand, in the case of the dynamic hydraulic pressure drop during the earthquake, a load distribution as shown in FIGS. 7 and 8 occurs.

That is, if an arbitrary point on the side plate 2 is taken and the angle formed by the radius passing through that point and the earthquake load direction is θ, then the vertical membrane force Ns and the increase in the overturning moment during the earthquake ΔNsco
sθ, an increase in the radial shearing force Qs mainly due to dynamic hydraulic pressure ΔQscOsθ, and an increase in the longitudinal bending moment Ms and the overturning moment during an earthquake ΔM8COS
θ works. Furthermore, although horizontal force H is actually applied during the earthquake, circumferential shear force N is generated as a new internal force due to horizontal force H.
sθ occurs. The circumferential shearing force Nsθ is an internal force that has hardly been considered in conventional tank designs, but as tanks become larger and seismic conditions become more severe, it is becoming a factor that cannot be ignored. This is the main focus for forming factors, and its distribution is a Sin distribution as shown in FIG. 8, and is assumed to have a maximum value in approximately 900 directions.

Then, assuming that the tank radius is R, the total load H. as shown in FIG. M and the above loads (Ns, Ms.Qs.N
sθ) distribution, and since the first term on the right side is generally much larger than the second term, it is thought that the overturning moment M during an earthquake mainly generates the vertical membrane force of the side plate. .

Therefore, in reality, as a measure to prevent the tank from overturning, an anchor bolt 4 corresponding to the vertical force Ns+ΔNs is installed to balance the overturning moment M.

Therefore, for the horizontal force H during an earthquake, the second term on the right side (sum of circumferential shear force increments) is the first
(total phase of radial shear force increments), but sufficient consideration has not been taken into consideration in conventional tank design.

Therefore, as long as the horizontal force H is applied, the circumferential shear force Nsθ is transmitted from the upper part of the measuring plate to the lower part with shearing deformation on the side plate, and the seismic horizontal force E is applied to the tank. As long as the horizontal movement of the tank is restrained, no matter how the horizontal movement of the tank is restrained, the circumferential shearing force Nsθ generated on the side plate will be transmitted to the bottom plate via the joint between the side plate and the annular plate. At that time, the distribution of the circumferential shearing force at the side plate joining part of the annular plate shows the same tendency as the circumferential shearing force at the side plate in Fig. 8, as shown in Fig. It is maximum in the 900 direction.

Additionally, as the shearing force increases and decreases, the generation of a circumferential membrane force (hereinafter tentatively referred to as a hoop in a part of the annulus) is observed, as shown in FIG.

At this time, some hoops of Anyura have a tensile force in the 00 direction,
It is a compressive force in the 180 la direction.

As a result of such shear load transmission from the side plate 2, it is natural that the above-mentioned annular plate undergoes a so-called "rice ball-shaped" shear deformation as shown in FIG. 11, and the bottom plate also undergoes shear deformation in the same way. It turns out.

However, some of the hoops in the above-mentioned annulus are transmitted inversely to the side plates, resulting in an increase in the hoops on the side plates, and unless the thickness of the side plates is increased, there is a synergistic effect that reduces safety.

That is, regarding the occurrence of shear stress in the side plates and annular plate, for example, if safety evaluation is performed based on the maximum shear stress theory as stated in the [Technical Guidelines for Industrial Safety and Disaster Prevention], the allowable shear stress τa, Yield stress σy
Considering that the allowable stress σa for bending is It is difficult to confirm that sufficient safety design considerations have been taken.

Therefore, when considering the theory of the load acting on the flat-bottomed cylindrical tank mentioned above during an earthquake and taking into account the flat-bottomed cylindrical tank based on the conventional technology, it is found that when designing the tank, the bottom plate, especially the annular plate, and the side plate should be However, there is a structural drawback in that the circumferential shear force generated by the horizontal force H during an earthquake, which is a large load, is not taken into account. Not only is there a risk of damage, but even if it is small, repeated loads can cause damage and paralyze tank function.

OBJECT OF THE INVENTION The purpose of the present invention is to solve the problems of the earthquake-resistant structure of flat-bottomed cylindrical tanks based on the above-mentioned prior art, and to improve the anti-hoop resistance that occurs in the annular plate without reinforcing the side plates. The purpose of the present invention is to provide an excellent flat-bottom cylindrical tank for use in the energy industry as an earthquake-resistant structure with reinforcement and a rational and theoretical design.

<Structure of the Invention> In accordance with the above-mentioned object, the structure of the present invention, which is summarized in the above-mentioned claims, is to reduce the amount of liquid stored in the flat-bottomed cylindrical tank and its own weight that is generated on the side plate and bottom plate when the tank receives horizontal input during an earthquake. Circumferential shear deformation, which is caused by horizontal force H due to the inertial load of Technical measures have been taken to increase the seismic strength of the flat-bottomed cylindrical tank by reducing or eliminating directional shearing forces.

Embodiment 1 Configuration> Next, embodiments of the present invention will be described in 12th to 1st embodiments.
The explanation will be as follows based on the drawing of FIG.

In the embodiment shown in FIG. 12, annular reinforcing beams 7 constituting a resistance reinforcing structure are integrally fixed vertically at predetermined positions on the inner periphery of the annular plate 6 of the flat-bottomed cylindrical tank 5 at predetermined intervals. As shown in FIG. 13, the reinforcing girder 7 has ribs 8 between the side plate 9 and the reinforcing girder 7, or between the bottom plate 13 or the annular plate 6 and the ribs 8 at appropriate intervals in the circumferential direction. It is fixedly interposed between the reinforcing girder 7 and the reinforcing girder 7. 12 is a foundation, which is installed in flat contact with the bottom plate 13 without constraining each other;
14 is a liquid storage.

<Embodiment 1 Effect> In the above configuration, the flat bottom cylindrical tank 5
When it receives horizontal input during an earthquake, its side plate 9, annular plate 6, etc. will experience vertical membrane forces, respectively, as described above.
Radial shear forces, longitudinal bending moments, circumferential shear forces, etc. are applied with interaction.

In particular, the horizontal force H during an earthquake is transmitted from the side plate 9 to the bottom plate 13 with shear deformation, and the resulting circumferential shear force and shear deformation are approximately 90 degrees with respect to the earthquake input direction.
However, in this invention, the reinforcing girder 7 provided on the annular plate 6 prevents the horizontal force bending of the lower part of the side plate 9, the annular plate 6, and the reinforcing girder 7. Due to the significantly increased rigidity,
The resistance of this increased bending rigidity restrains the shear deformation transmitted from the side plate 9 to the bottom plate 13, thereby keeping the shape of the bottom plate 13 inside the reinforcing girder 7 into a substantially circular shape even during an earthquake. As a result, shear stress can be reduced by preventing so-called "rice ball-shaped deformation". Therefore, the degree of safety against circumferential shear force failure at the bottom plate 13 does not decrease, and the flat-bottomed cylindrical tank 5 has high earthquake resistance, increasing the safety of the tank as a whole.

In addition, to show another design example of the above-mentioned embodiment, the one shown in FIG. In the embodiment shown in FIG. 15, an annular reinforcing beam 19 is vertically disposed on the outer periphery of the side plate 21 of the annular plate 20, and a rib 22 is provided. In the embodiment shown in FIG.
Further, in the embodiment shown in FIG. 17, reinforcing beams 28 are vertically disposed on the inner and outer sides of the annular plate 29 with side plates 30 interposed therebetween, and ribs 31 are provided.

Further, the present invention is not limited to the dome roof tank of the embodiment described above, but is applicable to flat bottom cylindrical tanks in general, including low temperature storage tanks and floating roof tanks.

According to the present invention, by providing a reinforcing girder on the upper surface of the annular plate, among the various loads that are applied to the tank itself due to the inertia of the tank body and stored liquid during an earthquake, in particular, the circumferential shear is reduced. We decided to give sufficient design consideration to force as an important element in strength design, and by vertically installing annular reinforcing girders on the annular plate, we increased the moment of inertia of the annular plate in the circumferential direction. It is possible to significantly reduce the circumferential shear force propagated from the side plate of the flat-bottomed cylindrical tank to the annular plate during an earthquake, thereby reducing the deformation caused by the circumferential shear force in the annular plate near the reinforcing girder and the bottom plate. extremely small, and as a result,
The excellent effect of preventing tank destruction and increasing its strength is achieved.

In addition, for example, by increasing the thickness of the annular plate, we also aim to reduce the annular part hoop force on the bottom plate of the annular plate, reduce the annular part hoop stress in the 00 direction, and improve the safety of the tank. It also has the effect of increasing.

Therefore, even when the load on the side plate is in the 00 direction, it is possible to minimize the increase in the side plate hoop due to the above-mentioned annular partial hoop, and it is also possible to incidentally prevent a decrease in the seismic strength of the side plate. The effect of making it possible is achieved.

In addition, since the tank is cylindrical in shape, it has the advantage of being able to exhibit the above-mentioned earthquake resistance in the same manner against any earthquake direction.

Furthermore, since the annular plate and the foundation are not constrained, the foundation has the advantage of being of conventional specifications.

[Brief explanation of the drawing]

Figure 1 is an illustration of the static load acting on the side plate of a typical flat-bottom cylindrical tank, Figure 2 is an illustration of the static load during an earthquake, Figure 3 is an illustration of the total load during an earthquake, and Figure 4 is an illustration of the annulus load. Fig. 5 is an explanatory diagram of the static load and moment acting on an arbitrary point on the side plate, Fig. 6 is an explanatory diagram of the static load on a part of the annulus, and Fig. 7 is when an earthquake input is applied. Fig. 8 is an explanatory diagram of the action of circumferential shearing force and a dynamic hydraulic pressure distribution diagram, and Fig. 9 is an explanatory diagram of circumferential shearing force distribution. Fig. 10 is an explanatory diagram of the hoopka distribution in a part of the annular plate, Fig. 11 is an explanatory diagram of the shear deformation of the annular plate 3 during an earthquake, and Fig. 12 and the following are explanatory diagrams of the embodiments of the present invention. FIG. 13 is a partially sectional perspective view of the flat bottom cylindrical tank, FIG. 13 is a partial sectional view of the vicinity of the bottom plate and side plate, and FIGS. 14 to 17 are sectional views illustrating the installation of reinforcing girders showing other embodiments. 1, 5, 24...Flat bottom cylindrical tank, 3, 6, 1
6, 20, 25, 29... Annular plate, 7, 8, 15, 17, 19, 22, 23, 27, 28
, 31...Seismic reinforcement member, 7, 15, 19, 2
3,28...Annular girder, 12...Foundation.

Claims (1)

[Claims] 1. In a flat-bottom cylindrical tank in which an annular seismic reinforcing member is fixed to an integral annular plate at the lower end of the side plate, the seismic reinforcing member is an annular girder and has a vertical cross section on the upper surface of the annular plate which is provided unrestricted on the foundation. A flat-bottomed cylindrical tank characterized by being fixed vertically.