JPH0941706A - Stainless steel tank and design method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stainless steel tank strong against external force of a great earthquake, etc., and excellent in work efficiency and to make it possible to design even a large water tank by analyzing structurally large frames provided in the inside space of a tank to design wall panels used for an exterior wall and stiffening collars. SOLUTION: Large frames 40 are provided to a water tank main body 10 to analyze structurally strength and deformation quantity with a finite element method. Then, static water pressure, dynamic water pressure and water weight acting on a water tank wall and a water tank floor are substituted for nodal load acting on the large frames 40. Then, sectional characteristics of finite elements are compared with each other to decide so that the maximum stress and deformation quantity of the finite elements are smaller than allowable value of a frame material. Wall panels 12, 14, 16, 18 and 20 and stiffening collars are designed for constructing the water tank wall, and the stiffening collars are provided at specific intervals between the large frames 40. When water pressure and earthquake act on the large frames, optimum combination of the plate thickness of the wall panels 12-20 with sectional size of the stiffening collars is so calculated that the maximum deflection quantity and maximum stress of them are within allowable value, and they are decided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel tank for storing a liquid such as water, and more particularly to an improved rectangular and relatively large stainless steel tank and a method for designing the same.

[0002]

Background Art A large rectangular stainless steel tank, for example, a stainless water tank used in a water purification plant, has a size of 1 [m] x 1
A large number of wall panels made of stainless steel such as [m] or 1 [m] × 2 [m] are joined in a rectangular parallelepiped shape to be assembled.

The procedure of the conventional design method will be described with reference to FIG. 8. First, static water pressure and dynamic water pressure act on the wall panel due to the weight of stored water, an earthquake, etc. It is replaced with a static load (step SA in the figure).
Further, the water weight and the dynamic water pressure act on the floor panel, and these are similarly replaced with the static load (step SB). And from those replaced static loads,
The maximum stress and the amount of deformation in each panel are calculated (step SC). Next, the thickness of each panel is determined from these calculated values (step SD). That is, the maximum stress of each panel is smaller than the allowable stress level of the stainless steel material, and
The thickness of each panel is determined so that the amount of deformation of each panel becomes smaller than the allowable value.

Next, the wall panels whose thickness has been determined as described above are joined to assemble a water tank. At this time, each panel is supported by the tension member so that the assembled water tank does not bulge outward due to the water stored therein (step SE). Since the arrangement intervals of the tension members are the same as the dimensions of the wall panel, the tension members are arranged inside the water tank like a jungle gym. In addition, in order to further support the pulling member, an uprising material or a fired material is provided as needed.

FIG. 9 schematically shows a part of a stainless water tank designed by such a conventional design method.
As shown in the figure, the wall panel 100 has a structure that resists a force applied to the panels by a frame 102 that bears a tensile force such as jungle gym built inside. The skeleton 102 is mainly composed of a skeleton 104 that pulls the wall panel 100 in the horizontal direction and a skeleton 106 (only part of which is shown) for supporting them in the vertical direction.

[0006]

As described above, conventionally, the design of the wall panel is started, and thereafter, the framework of the entire tension member is determined so as to support the wall panel.
That is, it is a design method in which an external force obtained by replacing hydraulic pressure or seismic force with a static load is resisted by a panel wall and the wall is prevented from collapsing by being pulled by a skeleton such as a jungle gym.

However, in such a conventional technique,
There are the following inconveniences. (1) Internal reinforcing frames such as jungle gym cannot fully resist horizontal load, so-called shear force, when seismic force is actually applied. As the fact that the steel or concrete gate-type highway viaduct collapsed due to shear forces in the next Hyogoken Nanbu Earthquake (January 17, 1995), the conventional internal reinforcement frame It cannot resist horizontal load sufficiently.

(2) As shown in FIG. 10, in the structural calculation for the frame, the static load acting on the wall panel 112 which is considered to be borne by each tension member 110 (the load acting on the shaded portion in the figure). The pulling member 110
The strength calculation is based on the assumption that it is a simple support member at both ends, and it is thought that it will give an excessively safe result.

(3) The work space in the water tank is narrow and the work efficiency is poor. (4) Since it is rectangular, the corners, that is, the corners, are weak in strength. For this reason, a large amount of reinforcing member is required to increase the strength of the corner portion. (5) Since the design method is based on the strength of the wall panel material, the maximum designable tank size is about 500 tons. However, recently, a water tank having a larger capacity is required, and a designing method for a large-capacity water tank is desired.

The present invention focuses on such points, and an object thereof is to provide a stainless steel tank which is strong against external force such as a large earthquake, has good workability, and enables the design of a large water tank, and a design method thereof. It is what

[0011]

In order to achieve the above object, according to the present invention, first, a large-frame framework is constructed in a tank, and its structural analysis is performed using the finite element method. The structural analysis of this large frame is based on the actual condition of the internal framework of the tank in order to analyze the entire large frame at a time, and the structural members can withstand both axial force and bending load. It is thought that it will not bring about such a result. In structural analysis, a large frame is placed so as to secure a working space, and analysis is performed in consideration of external forces such as a large earthquake. And after the design of the large frame,
The design of the wall panel and the stiffening brim that will be the outer wall is performed. A quarter cylinder panel is arranged in the corner portion in consideration of strength. The above and other objects, features and advantages of the present invention are
It will be apparent from the following detailed description and the accompanying drawings.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to Examples.

FIG. 1 shows an example of a stainless water tank designed by the design method of the present invention. In the figure, on the side surface of the water tank body 10, the length × width = 1 [m] × 2
5 [m] -sized wall panels 12 vertically, 3 horizontally
Individually joined. Also, in the corner part, vertical x horizontal = 1
Five wall panels 14 each having a size of [m] × 1 [m] and one-quarter cylindrical panels 16 are vertically joined to each other. Also,
Eight wall panels 18 of length × width = 0.5 [m] × 1 [m] and two 1/4 cylindrical panels 20 are joined to the uppermost stage. A ceiling panel 21 is joined to the ceiling side, and a floor panel (not shown) is joined to the floor side. The aquarium body 10 composed of these panels is wholly provided on the foundation 23.

At the bottom of the water tank body 10, an inflow pipe 24,
An outflow pipe 26, an overflow pipe 28, and a drain pipe 30 are provided, and a manhole 32, a vent 34, a water level gauge 36, and an outer ladder 38 are provided on the ceiling portion.

Next, the procedure of the method for designing the above stainless steel tank will be described. (1) Design of large frame Figure 2 shows the main steps. As a prerequisite for the design of the water tank shown below, the allowable bearing capacity of the ground, the weight of the water tank, and the foundation slab and foundation beams will be studied and designed.

In the water tank to be designed, two plane directions (one direction parallel to the foundation beam and one direction perpendicular to it)
Large frames are arranged at intervals of [m] (FIG. 2, step S).
10). At this time, a large frame having a space as large as possible is provided so that various works can be efficiently performed during the construction of the water tank and after completion. All large frame members are designed as rigid joint members that can resist both axial forces and bending. FIG. 3 shows how the large frame is arranged when the water tank body 10 is viewed from the ceiling side. As shown by hatching in the figure, the large frames 40 are arranged at equal intervals in the vertical and horizontal directions. In addition, what is shown by a dotted line in the figure is a caution frame 42 for stabilizing the quarter-cylindrical panel 16.

For example, the dimensions are width × depth × height = 10.
[M] × 10 [m] × 5.5 [m] water tank 2 [m] ×
Consider a large frame structure that can be divided into 10 [m] x 5.5 [m] segments and can resist the water pressure and water weight acting on each segment. In the design, assuming that the water in the tank fills up to the ceiling plate height,
Adopt water weight on the safe side.

FIG. 4 shows a part of the inside of the water tank body 10 as seen from the direction of arrow F1 in FIG. 3, and FIG.
The interior viewed from the # 5- # 5 line in the direction of the arrow is shown. As shown in these figures, in this embodiment, 2 [m]
The large frames 40 are arranged at intervals. In FIG. 4, the entire frame shown by hatching is the large frame 40. In the illustrated example, the large frame 40 includes the horizontal members 40A to 40A.
E, vertical members 40F-40H, brace members 40I-
Includes 40K.

The strength and the amount of deformation of the large frame 40 are structurally analyzed by the finite element method (step S12). At this time, the large frame 40 is divided into, for example, tens to hundreds of finite elements, and structural analysis is performed by the finite element method. For example, as finite elements (structural elements), axial force, shear force,
A bending member element having one node and three degrees of freedom capable of resisting a bending moment is used. Next, the static water pressure, dynamic water pressure, and water weight acting on the water tank wall and the water tank floor are replaced with the nodal load acting on the large frame 40 (step S14). For example, a numerical example of the load condition for the nodes H1 to H5 shown in FIG. 4 is shown in Table 1 below. In the table, X corresponds to the horizontal direction in FIG. 4 and Y corresponds to the vertical direction in FIG. Further, M is the direction of rotation, and E is a multiplier of 10. The other nodes can be similarly obtained.

[0020]

[Table 1]

Next, the sectional characteristics of each finite element are determined so that the maximum stress and the amount of deformation of each finite element obtained by the finite element analysis in step S12 are smaller than the allowable values of the frame material. (Step S16). Specifically, the total stress at the start and end points of the bending member element is calculated from the stiffness equation of one bending member element, and the allowable stress that is reduced considering the buckling phenomenon specified in the road bridge specification is exceeded. The dimensions of each member of the large frame structure are determined under the condition that there is none. For example, Table 2 shows numerical values of the structural analysis results for the members B1 to B5 shown in FIG. The same can be obtained for other members.

[0022]

[Table 2]

From the values shown in Table 2, the member force of each member element is converted into a stress level, and it is shown in Table 3 whether or not the total stress exceeds the above allowable stress. In the table, when the total stress exceeds the allowable stress, the numerical value of the total stress is 1.0 or more, but no such member is found in the example of the same table. Similar values are obtained for the other members, and the resultant stress is similarly examined. From this result, the cross-sectional characteristics of each member forming the large frame 40 are determined.
For example, as the member B1, length × width × thickness = 80 × 40
× 3 mm [shaped steel (channel steel) is used.
As the member B3, length × width × thickness = 20 × 20 × 3 mm
L-shaped steel (angle steel) is used.

[0024]

[Table 3]

(2) Design of wall panel and stiffening brim Next, in order to construct an aquarium wall, the wall panels 12, 14, 1
6, 18, 20 and stiffening collar 50 are designed. In this embodiment, the design is performed by regarding the convex wall panel as a flat plate having a plate thickness equivalent in strength (step S18). The wall panels 12 to 20 are usually subjected to uneven pressing to improve strength, but it is convenient to assume that they are flat plates in order to determine the plate thickness of the wall panels. Therefore, the plate thickness is calculated as a flat plate, and then a convexly deformed panel that is equivalent in strength is selected.

Specifically, a hydraulic load test is performed on the wall panel subjected to the convex deformation process, and the results are
Using the relational expression of the maximum deflection and the maximum bending moment when a uniform load is applied to a rectangular plate, the plate thickness of a flat plate having the same strength as the convexly deformed panel is calculated. Table 4 shows an example of a hydraulic load test for a stainless convex deformation panel having a short side of 1 [m] and a long side of 2 [m]. From the calculation using this test result, it was found that the equivalent flat plate thickness of the convex deformable panel is about 6 to 7 times the actual plate thickness. In other words, if a convex deformation panel is used, it will be 1/6 that of a flat panel.
A thickness of about 1/7 is sufficient. Here, in consideration of safety, the equivalent flat plate thickness is 5
Design is performed assuming that the thickness is twice as thick. Table 4
The medium and residual values represent the allowable residual deformation amount.

[0027]

[Table 4]

Next, in this embodiment, as shown in FIGS. 4 to 6, stiffening collars 50 are provided between the large frames 40 at predetermined intervals. The wall panels 12 to 20 are supported by the stiffening brim 50. In the design, it is assumed that the wall panels 12 to 20 are equivalent flat plates that are simply supported at the joints to the large frame 40 and elastically supported at the stiffening collar 50 (step S18). Then, when water pressure (static load) or earthquake (dynamic load) acts, the plate thickness of the wall panels 12 to 20 and the stiffening brim 50 are adjusted so that the maximum deflection amount and the maximum stress are within the allowable values. The optimum combination of cross-sectional dimensions (combination considered to be economically cheapest) is calculated (step S20). As a result,
Rectangular wall panels are usually placed vertically (vertically),
In this design method, the layout is horizontal (horizontally long). Table 5 shows the rigidity ratio (ratio of bending rigidity of equivalent flat plate and bending rigidity of stiffening collar).
And an example of the relationship between the maximum deflection and the maximum bending moment of the equivalent flat plate are shown.

[0029]

[Table 5]

Next, the thickness of the wall panels 12 to 20 and the cross-sectional dimension of the stiffening collar 50 are determined. Water pressure depending on the depth acts on each panel. That is, a trapezoidal distributed load, which is a partial load of the triangular hydraulic pressure distributed load, acts. However, it is assumed here that a uniformly distributed load equal to the mean value of the trapezoidal distributed load acts on the wall panels 12-20 supported by the stiffening collar 50. According to the experimental results shown in Table 4, the maximum allowable deflection of the stainless steel panel is 11 with respect to the static load.
[Mm] and 15 [mm] for the dynamic load. The allowable stress is 1400 [kg / c for static load.
m ² ], and 2000 [kg / cm ² ] with respect to the dynamic load. Therefore, the thickness of the wall panels 12 to 20 and the cross-sectional dimension of the stiffening brim 50 that satisfy these constraints are determined as economically as possible. Table 6 shows an example. In the table, the number of steps of the panel is the number of steps counted from the ceiling side of the water tank 10.

[0031]

[Table 6]

The stiffening collar 5 shown in Table 6 is used.
The required second moment of area of 0 is a value when the panel is considered as a single plate. In practice, since the panels of each stage are connected, the stiffness of the stiffening collar 50 at the panel connection portion is the sum of the stiffnesses required by both adjacent panels. In addition, since it is advantageous in terms of cost to use a member that is generally commercially available, in practice, a commercially available member having a second moment of area close to the conditions shown in Table 6 may be used.

(3) Joining between large frame members Further, in the present embodiment, since the large frame structure (including members under the floor plate) described above reliably transmits the axial force and the bending moment, the members of the large frame structure are connected to each other. The joint is also devised. In the above-described conventional design method, no special strength design is made for the joints between the members that make up the jungle gym, and they are simply joined by spot welding. In other words, it is welding only to maintain the shape of the jungle gym.

On the other hand, in this embodiment, the gusset of the bridge member is used so that the axial force and the bending moment are reliably transmitted. Structural calculation is performed. The major gusset joints are shown enlarged in FIG. FIG. 7A is an enlarged view of a portion from PA to PB in FIG. 4, and the large frame member 40 is shown on the left side of FIG. 7A.
B is joined to the gusset 60A, and on the right side, the large frame members 40B, 40G, 40I, 40J are joined to the gusset 60B.

FIG. 7B is an enlarged view of the portion from PC to PD in FIG. 5. The large frame member 40L is joined to the gusset 60C on the left side of FIG. 7B, and the large frame member 40L is large on the right side. The frame members 40L and 40M are joined to the gusset 60D. In FIG. 7C, the PE portion of FIG. 4 is shown in an enlarged manner, and the large frame members 40E, 40F, 4
0K is joined to the gusset 60E.

As described above, according to the design method of this embodiment, the design starts from a large frame constructed using a material capable of bearing bending force and axial force, and is regarded as an elastically supported equivalent plate. Leading to the economical design of wall panels. That is, the design process is completely opposite to the above-mentioned conventional technique. Therefore, the following advantages can be obtained.

(1) The large frame is designed by the finite element method by replacing the water pressure and the seismic force with the nodal load acting on the large frame. Therefore, while the conventional internal reinforcing member having the jungle gym structure can only bear the tensile force, it can also resist the load in a large earthquake.

(2) Since the 1/4 cylindrical panel is used in the corner portion and the precautionary frame is provided between the corners, the large frame structure can be maintained even in the corner portion. The strength is improved as compared with the conventional rectangular parallelepiped.
It also has an excellent external appearance. It should be noted that the present embodiment can be considered to be located between the conventional rectangular water tank and the cylindrical water tank.

(3) If a large frame having a wide space is used at the time of design, a good working space can be secured.

(4) Regarding the stainless steel tank, the structural design method considering the frame and the wall panel as one body has not been established yet. The conventional design method from the wall panel to the skeleton (jungle gym) is how much the wall panel can withstand static and dynamic loads.
No consideration has been given to the overall structural design of the wall panel and frame, and the empirical judgment factor is probably large. In other words, the actual situation is that we actually make a water tank, fill it with water, and then conduct an experiment to see if the water tank will break. Therefore, a small capacity is sufficient, but it is not suitable for designing a large tank. However, according to the present embodiment, since the design is performed not from the panel but from the frame, 2000
It is also possible to design a water tank of about ton.

(5) Since the gusset is used in the joint portion of the large frame member, the axial force and the bending moment are surely transmitted, and good strength against external force can be obtained.

The present invention has numerous embodiments,
Various modifications can be made based on the above disclosure. For example, the following is also included. (1) In the above embodiment, the large frames are arranged at intervals of 2 [m], but the arrangement intervals may be increased or decreased as necessary. (2) Although the above-mentioned embodiment applies the present invention to a water tank, it can also be applied to the storage of other liquids. (3) The numerical values shown in the above embodiments are also examples, and the present invention is not limited thereto.

[0043]

As described above, according to the present invention, the frame is designed from the large frame and then the panel is designed. Therefore, the panel is strong against external force such as a large earthquake and the workability is good. In addition, the effect that it is possible to design a large water tank can be obtained.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a stainless steel tank according to the present invention.

FIG. 2 is a diagram showing a procedure of a method for designing the stainless steel tank.

FIG. 3 is a diagram showing a large frame as seen from a plane of the stainless steel tank.

FIG. 4 is a diagram showing a large frame as seen from the direction F1 in FIG.

5 is a view taken along line # 5- # 5 in FIG. 4 as seen in the direction of the arrow.

FIG. 6 is a diagram showing a relationship between a large frame, a stiffening brim, and a wall panel.

FIG. 7 is a view showing a gusset joint portion between members of a large frame.

FIG. 8 is a diagram showing a procedure of a conventional design method.

FIG. 9 is a partial perspective view showing the inside of a conventional stainless water tank.

FIG. 10 is a partial perspective view showing the inside of a conventional stainless steel water tank.

[Explanation of symbols]

 10 ... Water tank main body 12, 14, 16, 18, 20 ... Wall panel 23 ... Foundation 24 ... Inflow pipe 26 ... Outflow pipe 28 ... Overflow pipe 30 ... Drain pipe 32 ... Manhole 34 ... Vent 36 ... Water level gauge 38 ... Outside Ladder 40 ... Large frame 42 ... Beware frame 50 ... Stiffening collar 60 ... Gusset

Claims (4)

[Claims] 1. A step of arranging a large frame serving as a framework of a stainless steel tank in a space inside the tank; a step of structurally analyzing the large frame by a finite element method to calculate maximum stress and deformation amount; tank wall and tank floor The static pressure, dynamic pressure and liquid weight acting on the frame are replaced by the nodal load acting on the large frame; the cross-sectional characteristics of each finite element so that the maximum stress and the amount of deformation are smaller than the allowable value of the frame material. A method for designing a stainless steel tank, the method comprising: 2. A stiffening brim is provided between the large frames, and the wall panel is assumed to be a flat plate elastically supported by the stiffening brim, and the maximum deflection amount and the maximum stress when a predetermined load acts on the flat plate. 2. The method for designing a stainless steel tank according to claim 1, further comprising the step of calculating the plate thickness of the wall panel and the cross-sectional dimension of the stiffening collar so that is within an allowable value. 3. A stainless steel tank designed by the design method according to claim 2, wherein a large frame serving as a framework of the stainless steel tank; a stiffening brim provided between the large frames; Wall panel provided; 1/4 cylindrical panel used in the corners;
A stainless steel tank provided with a precautionary frame for stabilizing this quarter cylinder panel. 4. The stainless steel tank according to claim 3, wherein a gusset is used at a joint portion between members of the large frame and the precautionary frame.