CN101211379A - Static and Dynamic Analysis Method for Large Column Digester - Google Patents

Abstract

The invention discloses a static dynamic analysis method of a large cylindrical digester, comprising the following steps: determining the structure, material and geological parameters of the digester; defining the load and value of the digester; based on the plate shell unit and the three-dimensional Establish and calculate the simplified model of the digester with block elements; conduct static analysis on the simplified model: determine the combination of digester load and working conditions; equivalent conversion of prestressed load, convert the internal force of the hoop prestressed steel bar into equal Effect external load; internal force analysis of the digester under the load standard value; force analysis of the cylindrical digester under the design value; input seismic waves, use the three-dimensional overall modeling method to perform dynamic analysis on the simplified model, and obtain the top ten order mode. The invention can accurately simulate the circumferential force on the pool wall produced by the prestressed tendons, and obtain the vertical bending moment of the pool wall produced by the prestress under the working condition of the empty pool, thereby avoiding the vertical bending moment of the pool wall caused by the vertical Cracking phenomenon caused by inaccurate calculation of bending moment value.

Description

Static and Dynamic Analysis Method for Large Column Digester

technical field

The invention belongs to the field of structural engineering, in particular to a highly reliable static and dynamic analysis method for a digester.

Background technique

With the development of the national economy and the improvement of people's quality of life, the contradiction between industrial and domestic water use and actual water supply capacity has become increasingly acute. In order to achieve energy saving and emission reduction, environmental engineering has attracted more and more attention. Due to the rapid development of industry, the population of cities and towns has increased rapidly, and the sources of pollution have increased. However, the investment in urban infrastructure construction, especially municipal engineering, and environmental protection measures are not in place. A large amount of industrial wastewater and domestic water are directly discharged into urban rivers, resulting in Serious pollution of the living environment of residents. To protect the urban environment, improve the quality of life, and promote economic development, sewage treatment is imminent and imperative. Sewage treatment projects can not only turn waste into treasure, but also a sign of urban environmental quality and a symbol of civilization. Many developed countries in the world have used it as one of the means of resource utilization, and are committed to its research and application, and urban sewage treatment systems are becoming more and more important. In the process of sewage treatment, a large amount of sludge is produced. The sludge is very unstable and needs to be treated in time to achieve the purpose of comprehensive utilization of resources and environmental protection. The cost of sludge disposal is very high, accounting for about 20% to 50% of the operating cost of the sewage treatment plant, and the digester is the main structure in the sludge disposal process.

The sludge digester is one of the main structures in the process flow of large-scale sewage treatment plants using the activated sludge method. The digester is basically composed of four parts: gas collecting hood, tank cover, tank body and lower cone, with stirring and heating equipment attached. The digester has a large capacity and high internal pressure. After construction, it is full of water all the year round, with a water level of more than 10m, and the water level of a large digester is even as high as 30m. In addition, the digestion tank is generally required to maintain a medium temperature of 33-35 °C, and biogas is generated during the digestion process, and there is a certain internal pressure. Therefore, the structure of the tank body is required to be airtight, water-tight and air-tight, and cracks are absolutely not allowed on the tank wall. Insulation is required. Therefore, the digester has the characteristics of high size, heavy weight, complex structure and bearing capacity, long construction period, and high cost in investment.

Among water supply and drainage structures, cylindrical digesters are the most widely used. This type of digester has a simpler structure and is more convenient to construct. It was initially favored in sewage treatment systems. This type of digester is mainly built in the United Kingdom and the United States, also known as Saxon type. Digester, as shown in Figure 1-1. The second is a digester with a cylindrical wall as the main body and a combination of cones on the upper and lower parts. It is mainly built in the European continent and is called a continental digester, as shown in Figure 1-2. These cylindrical structures are all composed of one or several rotating shells, circular beams and circular plates. The combined structure of these rotating shells can give full play to the characteristics of good mechanical performance, high rigidity, and material saving of the shell. Most of the casing is mainly subjected to axial force, so the effectiveness of all materials can be fully utilized, it can be made into a thinner thickness, and can cover a larger area.

For the sake of brevity, we will collectively refer to the above-mentioned Saxon and continental digesters as columnar digesters. As shown in Figure 1-1 and Figure 1-2.

The history of the development of domestic cylindrical digester design has appeared successively: the cylindrical digester with non-prestressed structure, the cylindrical digester with prestressed wire-wrapped structure, and the current one with unbonded prestressed technology Cylindrical digester.

The design and calculation of the digester are mainly based on empirical design and supplemented by simple theoretical verification, which requires high design ability of engineering designers. Most designers rely on engineering experience to ignore secondary factors when establishing calculation models, such as the influence of small openings, the influence of appendages on the structure, the simulation of similar unit types, and the simple distinction of boundary conditions as hinged or rigid. , and then take the maximum value, etc. These simplifications lead to relatively conservative calculation results, often with high safety factors and excessive amounts of various materials, resulting in unnecessary waste.

At present, for the general pool structure, two methods are commonly used in the design: one is to simplify the calculation model according to the actual engineering, and compile the internal force coefficient table of the cylindrical shell, conical shell, spherical shell, and circular plate under various load conditions , for simple pool structures, such as cylindrical pools, conical pools, etc., the internal force at each height of the pool wall can be obtained by looking up the table first, and then by manual calculation. In terms of formula derivation for simple models, researchers at home and abroad have rich experience and can guarantee the calculation accuracy required by engineering practice. As for the cylindrical digester, it has the characteristics of high body size, heavy weight, complex structure and stress situation. At the same time, the cylindrical digester belongs to the category of special structures, which are different from both architectural structures and hydraulic structures, which put forward higher requirements for its design. The research and analysis on the structure of cylindrical digester has attracted more and more attention. Due to the complex structure, the derivation of the formula is very cumbersome. So far, there are no ready-made calculation formulas and tables for application. The whole can only be split into ring beams, cone shells, egg shells, blocks, etc., and the components of each part are considered separately. Boundary conditions, and calculate their respective internal forces, and then combine the internal forces according to the stiffness conditions, which brings a lot of trouble to manual calculations and is prone to errors. The second is to use large-scale calculation and analysis software to establish a mathematical model in line with the actual situation according to the actual structural form and boundary conditions, and calculate it by computer. This method requires the designer to have a good foundation in mathematics and finite element elements, especially when dealing with boundary conditions. This method is also the first method to be considered when calculating the digester.

The digester is the key structure of the sewage treatment plant, which has the characteristics of high size, heavy weight, complex structure and stress. At the same time, the pool structure (including the cylindrical digester) belongs to the category of special structures, which are different from both architectural structures and hydraulic structures, which put forward higher requirements for its design. In recent years, more and more attention has been paid to the research and analysis of digester structure.

Contents of the invention

The large-scale cylindrical digester referred to in the present invention refers to a cylindrical digester with a capacity of 5000 to ^15000m3 , and the static and dynamic analysis method of the large-scale cylindrical digester of the present invention solves the equivalent transformation of the prestressed load of the large-scale cylindrical digester It overcomes that in the prior art, because its equivalent conversion method cannot be quantified, it cannot correctly guide the design of the digester, which brings many uncertain factors to the normal use of the digester in the future, such as: it cannot give Due to the constant load effect caused by the prestress, the vertical bending moment value of the digestion tank cannot be accurately obtained, which leads to cracking of the tank wall.

In order to solve the above-mentioned technical problems, the technical scheme implemented by the static and dynamic analysis method of the large cylindrical digester of the present invention is to include the following steps: determining the structural parameters, material parameters and geological parameters of the digester; defining the load and value range of the digester ; Establish and calculate the simplified model of the digester based on the plate shell element and three-dimensional block element in the ANSYS system; conduct static analysis on the simplified model of the above-mentioned large cylindrical digester: determine the combination of loads in the digester; The equivalent transformation of the prestressed load converts the internal force of the hoop prestressed steel bar into an equivalent external load;

That is: take a thin-walled rotating cylinder with a ratio of inner diameter to outer diameter close to 1, and there is a uniform pressure p acting on the outside;

Taking a circular platform with a height of dz, this section of curved thin-walled cylinder can be approximately regarded as the side of the circular platform under the action of uniform force, the dimensions are: average radius R, thickness t, the angle between the outer wall and the horizontal plane is α, and the angle of the ring is from β ₁ to _β2 ;

Under the action of uniform pressure p on the outside of the thin-walled cylinder, hoop stress σ _θ is generated in the circumferential direction, and radial stress σ _r is generated in the radial direction;

The radial stress changes from -p on the outside of the pool wall to 0 on the inside of the pool wall. When the wall thickness is very thin, σ _r is very small compared with σ _θ . Therefore, σ _r is often negligible, and it is assumed that σ _θ is at uniform distribution in the section, then the concentrated force T on the section in the height direction is the product of σ _θ and the area of the section;

Let the y-coordinate axis of the simplified model of the digester be the symmetry axis of the fan-shaped ring, and take a micro-segment dβ, then the force acting on the dβ segment is:

dP=pRlcos(α)dβ (3)

The force acting on the β ₁ -β ₂ fan-shaped ring is:

$\underset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; pR</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&beta;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Considering the force balance in the y direction on the ring, and β ₂ =180-β ₁ , then

$\underset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; pR</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&beta;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Formula (5) simplifies to:

2pRlcos(α)cos(β ₁ )=2Tcos(β ₁ ) (6)

Namely: pRlcos(α)=T

Among them: T—the ring tension of all prestressed steel bars within the range of length l (N/m ² )

Here, T＝Ay·(σ _con -∑σ _li )

Where: Ay—the cross-sectional area of all prestressed steel bars within the range of length l (mm ² )

σ _con — Tension control stress of prestressed steel bars (N/mm ² )

∑σ _li — total prestress loss of prestressed steel bars (N/mm ² )

Equivalent pressure of prestressed steel bars:

$\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Ay</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; con</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; lt</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; Rl</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

R——circumferential horizontal radius of the pool body within the range of l, taking the average value (m);

α—the angle between the shell normal and the horizontal plane.

Through the above calculation, the internal force of the hoop prestressed steel bar is transformed into an equivalent external load; the internal force analysis of the cylindrical digester under the load standard value is carried out; the force analysis of the cylindrical digester under the design value is carried out; the input seismic wave , using the method of three-dimensional overall modeling to carry out dynamic analysis on the simplified model of the above-mentioned large-scale cylindrical digester, so as to obtain the dynamic characteristics of the large-scale cylindrical digester.

In the static dynamic analysis method of the large-scale cylindrical digester of the present invention, the dynamic characteristics of the obtained large-scale cylindrical digester are the mode shapes and frequencies of the large-scale cylindrical digester in two states of empty pond and full pond. The ten-order mode shapes are as follows: mode shape 1 is the expansion and contraction of the pool wall in the directions of 0 degrees, 120 degrees and 240 degrees; mode shape 2 is the expansion and contraction of the pool wall in the directions of 30 degrees, 150 degrees and 270 degrees; Type 4 is swinging back and forth; mode shape 5 is the expansion and contraction of the pool wall in the directions of 30 degrees, 120 degrees, 210 degrees and 300 degrees; mode shape 6 is the expansion and contraction of the pool wall in the directions of 45 degrees, 135 degrees, 225 degrees and 315 degrees; 7 is the expansion and contraction of the pool wall in the direction of 45 degrees and 225 degrees; the mode shape 8 is the expansion and contraction of the pool wall in the directions of 90 degrees and 270 degrees; the mode shape 9 is the expansion and contraction of the pool wall in the directions of 0 degrees, 72 degrees, 144 degrees, 216 degrees and 288 degrees Shrinkage; mode shape 10 is the expansion and contraction of the pool wall in the directions of 54.5 degrees, 126.5 degrees, 198.5 degrees, 270.5 degrees and 342.5 degrees.

Compared with the prior art, the present invention has the beneficial effect that since the hoop force generated by the prestressed tendons on the wall of the large cylindrical digester can be accurately simulated, it can be concluded that the digester is in the air Under the working condition of the pool, the vertical bending moment of the pool wall is generated by the prestress, so as to avoid the cracking of the pool wall caused by the inaccurate calculation of the vertical bending moment value.

Description of drawings

Figure 1-1 is a schematic diagram of a Saxon digester;

Figure 1-2 is a schematic diagram of a continental digester;

Fig. 2 is a structural sectional view of a large cylindrical digester;

Fig. 3 is a calculation model diagram of a large cylindrical digester;

Fig. 4 is the force diagram that the internal force of the prestressed steel bar is converted into an equivalent pressure and acts on the wall of the cylindrical digester;

Figure 5 is a force diagram of the wall of a large cylindrical digester under three load combinations;

Figure 6 is a force diagram of the top of a large cylindrical digester under three load combinations;

Figure 7-1, Figure 7-2, Figure 7-3 and Figure 7-4 are respectively the circular force diagram, vertical force diagram and circular bending moment diagram of the pool wall under the joint action of gravity, water pressure and air pressure standard values and the vertical bending moment diagram;

Figure 8-1, Figure 8-2, Figure 8-3 and Figure 8-4 are the hoop force diagram, vertical force diagram, hoop bending moment diagram and vertical bending moment on the pool wall under the action of prestress standard value respectively picture;

Figure 9-1, Figure 9-2, Figure 9-3 and Figure 9-4 are the hoop force diagram, vertical force diagram, hoop bending moment diagram and vertical bending diagram of the pool wall under the joint action of gravity and prestress respectively. moment diagram;

Figure 10-1, Figure 10-2, Figure 10-3 and Figure 10-4 are respectively the hoop force diagram, vertical force diagram, hoop bending moment diagram and vertical bending moment diagram;

Figure 11-1, Figure 11-2, Figure 11-3 and Figure 11-4 are the circular force diagram, vertical force diagram and circular bending moment diagram of the pool wall under the joint action of gravity, prestress, water pressure and air pressure respectively and the vertical bending moment diagram;

Figure 12-1, Figure 12-2, Figure 12-3, and Figure 12-4 are the circular force diagram, vertical force diagram, and circular bend of the pool wall under the joint action of gravity, prestress, water pressure, air pressure and temperature, respectively. moment diagram and vertical bending moment diagram;

Fig. 13-1, Fig. 13-2, Fig. 13-3, Fig. 13-4, Fig. 13-5 and Fig. 13-6 are the deformation diagrams of the large cylindrical digester under various load conditions;

Figure 14-1 to Figure 14-10 are the first ten vibration modes of the large cylindrical digester;

Fig. 15 is a flow chart of the static dynamic analysis method for a large cylindrical digester of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 15, the static dynamic analysis method of the large cylindrical digester of the present invention comprises the following steps: determine the structure, material and geological parameters of the digester; define the load and value of the digester; Establish and calculate the simplified model of the digester with three-dimensional block elements; conduct static analysis on the simplified model: determine the combination of digester load and working conditions; equivalent conversion of prestressed load, convert the internal force of the hoop prestressed steel bar into The equivalent external load; the internal force analysis of the digester under the action of the standard load value; the force analysis of the cylindrical digester under the action of the design value; input the seismic wave, and use the three-dimensional overall modeling method to perform dynamic analysis on the simplified model, and obtain the previous Tenth order mode.

The general engineering situation (that is, the structure of the digester) involved in the static and dynamic analysis method of the large-scale columnar digester of the present invention is: used as a large-scale columnar digester in the sewage treatment plant, the pool body Unbonded prestressed reinforced concrete structure is adopted. Its structural shape (from bottom to top) is composed of inverted conical shell, bottom ring beam, cylindrical shell, upper ring beam, spherical shell and other unit components, and the effective volume of each pool is up to 10000m ³ . The foundation of the digestion tank is made of C30 concrete, the wall of the tank is made of C40 concrete, and the prestressed structure is adopted. The sectional view of the digestion tank is shown in FIG. 2 .

1. Determine the basic parameters of the material properties of the large cylindrical digester: the materials used for the digester are mainly concrete, unbonded prestressed steel bars, and ordinary steel bars. The tank wall is made of C40 concrete, the foundation is made of C30 concrete, and the unbonded prestressed 7Φ5 steel strands are used for stress reinforcement, HPB235 (φ) and HRB335 (Φ) are used for ordinary reinforcement, and the material parameters of concrete and unbonded prestressed reinforcement are shown in Table 1. The anchorage adopts OVMZ15-X special anchorage. When the unbonded prestressed steel strand is tensioned, both ends of the jack are used for tensioning. The tensioning method is the post-tensioning method.

Table 1 Material parameters

Concrete   Unbonded prestressed reinforcement parts pool wall Base type 7Φ5 power level C40 C30 Nominal diameter (mm) 15.2 Standard value of axial tensile strength f _tk (N/mm ² ) 2.39 2.01 Nominal cross-sectional area (mm ² ) 139 Design value of axial tensile strength f _t (N/mm ² ) 1.71 1.43 Strength standard value f _ptk (N/mm ² ) 1860 Standard value of axial compressive strength f _ck (N/mm ² ) 26.8 20.1 Strength design value f _py (N/mm ² ) 1320 Axial compressive strength design value f _c (N/mm ² ) 19.1 14.3 Elastic modulus E _s (×10 ⁵ N/mm ² ) 1.95 Elastic modulus E _c (×10 ⁴ N/mm ² ) 3.25 3.00 Tensile control stress σ _con (N/mm ² ) 0.75f _ptk Poisson's ratio μ _c 0.2 0.2 Coefficient of linear expansion α _c (/℃) 1×10 ⁵

2. Determine the material parameters and geological data used in the dynamic analysis:

The specific data are shown in Table 2 and Table 3 respectively.

Table 2 Material parameters required for dynamic analysis

parts pool wall Abutment pile liquid Concrete strength grade C40 C30 C25 / Elastic modulus (10 ⁴ N/mm ² ) 3.25 3.00 2.80 / Poisson's ratio 0.2 0.2 0.2 / Damping ratio 0.05 0.05 / / Density (10 ³ kg/m ³ ) 2.5 2.5 2.5 1.05

Table 3 Geological data

Soil layer number Bottom elevation m Soil thickness m Elastic modulus P _a Poisson's ratio μ Cohesion cP _a Friction angle φ° Wet bulk density kg/m ³ 1 1 2.5 1.28E+07 0.4   24250 14.5 1835 2 -11 12 9.28E+06 0.4 14139 17.3 1820 3 -17 6 2.53E+07 0.35   16167 24.4 2023 4 -20 3 3.40E+07 0.3 2000 30 2090 5 -48.5 28.5 1.92E+07 0.35 16500 23.9 2040

3. Define the load value and working condition combination

(1) Load value

The loads acting on the digester fall into two categories, permanent loads and variable loads. The self-weight of the structure, the water pressure in the pool, and the prestress of the structure are permanent loads; the air pressure and temperature (humidity) changes acting on the digester are variable loads.

The values of various loads and their acting positions are as follows:

Self-weight: the self-weight of reinforced concrete shall be 25kN/ ^m3 ;

Air pressure: Air pressure is divided into working air pressure and test air pressure, and its size and action position are determined according to process requirements. The working air pressure of the digester is 6.0kPa, and the test air pressure is 1.5 times of the working air pressure, which is 9.0kPa. The air pressure is evenly distributed and acts on the inner wall of the entire digester;

Water pressure: The water pressure in the pool should be calculated according to the hydrostatic pressure of the design water level. For the sewage treatment pool, the gravity density of sewage is 10.5kN/m ³ , the design water level is 1.1m above the junction of the conical shell and the spherical shell, the water level elevation is 33.290m, and the water depth is 39.790m. It is distributed in a triangle and perpendicular to the inner wall of the digester.

Temperature: The process of sludge digestion tank adopts medium temperature digestion (33℃～35℃), which causes thermal expansion and contraction deformation of the tank wall and roof, and deformation caused by temperature difference inside and outside the tank wall, and when these deformations are constrained When , stress is generated in the cell body. According to the requirements of the specification, the temperature difference of the pool wall is 10°C.

Prestress: The standard value of prestress acting on the structural components of the pool should be adopted according to the tension control stress value of the prestress steel bar minus the prestress loss of the corresponding tension process.

(2) Combination of working conditions

The structural components of the pool should be calculated according to the limit state of the bearing capacity. Except for the overall stability check calculation of the structure, the rest shall use the sub-item coefficient design expression. And should satisfy the following formula:

γ ₀ S≤R (1)

γ ₀ ——structural importance coefficient. Generally, the safety level of the pool is taken as level two, and γ ₀ is taken as 1.0;

S—the combined design value of action and effect;

R——Design value of resistance of structural member.

The combined design value S of action effect should satisfy:

S＝γ _G1 C _G1 G _1k +γ _G (C _w F _wk +C _p F _pk )+ψ _c γ _Q (C _gas F _gask +C _t F _tk ) (2)

γ _G1 ——digester self-weight partial coefficient, take 1.2; when it is beneficial to the structure, take 1.0;

C _G1 ——digester self-weight effect coefficient;

G _1k ——Standard value of self-weight of digester;

γ _G —— Subitem coefficient of water pressure and prestress acting on the digester, 1.27 when it is unfavorable to the structure; 1.0 when it is beneficial to the structure;

C _w —coefficient of water pressure effect in the pool;

F _wk — standard value of water pressure in the pool;

C _p —coefficient of prestressing effect;

F _pk — standard value of pre-stress;

γ _Q ——partial coefficient of air pressure and temperature acting on the digester, take 1.40;

ψ _c —coefficient of combination of two or more variable effects, take 0.9;

C _t —coefficient of temperature (humidity) effect effect;

f _tk ——the standard value of temperature (humidity) effect.

When calculating according to the limit state of bearing capacity, the design value of the basic combination of action effects should be based on the form of the pool and its working conditions to take different combinations of action items. For ground pools, the internal force analysis must consider various possible loads in the construction stage, normal use stage, and closed water and air-tight test stage. The load combinations that need to be considered are as follows:

Gravity + water pressure + air pressure (combination of standard values, used to calculate prestressed steel bars)

Gravity + prestress (the most unfavorable load combination that produces vertical bending moment when the tank is empty)

Gravity + prestress + water pressure (load combination during closed water test)

Gravity + prestress + water pressure + air pressure (load combination in closed water and air test)

Gravity + prestress + water pressure + air pressure + temperature (load combination in normal use stage)

4. The establishment of the model carried out by the present invention on the above examples, the equivalent of the prestressed load, the force analysis of the cylindrical digester under the action of the design value, and the dynamic analysis of the cylindrical digester

(1) Calculation model

The calculation model on the rigid foundation, as shown in Figure 3, uses ANSYS software for internal force calculation and analysis, the pool wall uses shell elements, the foundation uses solid elements, and fixed constraints are imposed on the positions of cast-in-situ piles on the bottom surface of the foundation. Its application is: static analysis of digester; earthquake response analysis of digester.

(2) Transformation of equivalent load of prestressed steel bars

The prestressed steel bars have a restraining effect on the circumferential displacement of the digester under the action of water pressure. The steel bars can generate sufficient circumferential pressure to offset the circumferential tension produced by the water pressure. The effect is equivalent to the uniform distribution on the outside of the tank wall pressure.

How to convert the internal force of the prestressed steel bar into equivalent pressure to act on the tank wall of the digester is a key issue in the present invention.

Take a thin-walled rotating cylinder with a ratio of inner diameter to outer diameter close to 1, as shown in Figure 4, there is a uniform pressure p acting on the outside. Taking a circular platform with a height of dz, this section of curved thin-walled cylinder can be approximately regarded as the side of the circular platform under the action of uniform force, the dimensions are: average radius R, thickness t, the angle between the outer wall and the horizontal plane is α, and the angle of the ring is from β ₁ to β ₂ . Under the action of uniform pressure p on the outside of the thin-walled cylinder, hoop stress σ _θ is generated in the circumferential direction, and radial stress σ _r is generated in the radial direction. The radial stress changes from -p on the outside of the pool wall to 0 on the inside of the pool wall. When the wall thickness is very thin, σ _r is very small compared with σ _θ . Therefore, σ _r is often negligible, and it is assumed that σ _θ is at Evenly distributed in the section, then the concentrated force T on the section in the height direction is the product of σ _θ and the area of the section.

Let the y coordinate axis be the symmetry axis of the fan-shaped ring, take a micro-segment dβ, and the force acting on the dβ segment is:

dP=pRlcos(α)dβ (3)

The force acting on the β ₁ -β ₂ fan-shaped ring is:

$\underset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; pR</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&beta;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Considering the force balance in the y direction on the ring, and β ₂ =180-β ₁ , then

$\underset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; pR</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&beta;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Formula (5) simplifies to:

2pRlcos(α)cos(β ₁ )=2Tcos(β ₁ ) (6)

Namely: pRlcos(α)=T

T—the ring tension of all prestressed steel bars within the range of length l (N/m ² )

Here, T＝Ay·(σ _con -∑σ _li )

Ay—the cross-sectional area of all prestressed steel bars within the range of length l (mm ² )

σ _con — Tension control stress of prestressed steel bars (N/mm ² )

∑σ _li — total prestress loss of prestressed steel bars (N/mm ² )

Equivalent pressure of prestressed steel bar:

$\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Ay</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; con</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; lt</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; Rl</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

R——circumferential horizontal radius of the pool body within the range of l, taking the average value (m);

α—the angle between the shell normal and the horizontal plane.

Through the above calculation, the internal force of the hoop prestressed steel bar is transformed into an equivalent external load.

(3) Internal force analysis of cylindrical digester under load standard value

After the large-scale cylindrical digester is subjected to the load standard value, there is a big difference in the law of internal force generated on the wall and roof of the tank. Figure 5 shows the force of the wall of the large cylindrical digester under three load combinations, and Figure 6 shows the force of the top of the large cylindrical digester under the three load combinations, Figure 5 and Figure 5 The (a) curve shown in 6 is the force curve under the action of gravity standard value; (b) curve is the force curve under the joint action of gravity and water pressure standard value; (c) curve is the force curve under the action of gravity, water pressure The force curve under the joint action of the air pressure standard value.

For the wall of the digester, the internal force of the wall is the largest when the three loads act together, while the force generated by gravity and air pressure is very small, and the force generated by gravity on the wall of the cylindrical digester is quite small, and most of the range The ring pull is close to zero. For the pool roof, the hoop force is mainly controlled by gravity. Since the pool roof is relatively thin and the gravity is small, the hoop force generated is also relatively small. The internal force diagrams of the digester under the joint action of gravity, water pressure and air pressure standard values are shown in Figures 7-1 to 7-4, where Figure 7-1 is a circular force diagram, and Figure 7-2 is a vertical force diagram, and 7-3 is a hoop bending moment diagram, and Fig. 7-4 is a vertical bending moment diagram. It can be seen that under the combined action of the three loads, the circumferential direction of the cylindrical digestion tank wall mainly produces ring tension, and the maximum value occurs in the range of the middle and lower height; the radial direction mainly produces pressure, which is linearly distributed and mainly composed of water pressure. Decision; the hoop bending moment and vertical bending moment only occur in the range near the bottom of the middle and lower part.

(4) Stress analysis of cylindrical digester under design value

①The internal force of the cylindrical digester under the equivalent pressure of prestress

The equivalent pressure of the prestressed steel bar acts on the tank wall of the digester, and the internal force diagrams obtained after calculation are shown in Figure 8-1 to Figure 8-4, where Figure 8-1 is the circular force diagram, and Figure 8-2 is the Vertical force diagram, Figure 8-3 is a hoop bending moment diagram, and Figure 8-4 is a vertical bending moment diagram. It can be seen that the prestressed steel bars only produce circumferential pressure on the pool wall and do not affect the vertical force of the pool wall. The reason is that when the pool wall is vertical, the hoop prestressed steel bars only produce uniform pressure perpendicular to the pool wall, without Vertical component. But for the top of the pool, the prestressed steel bars not only produce hoop pressure, but also produce vertical pressure to offset the vertical tension generated by other loads on the top of the pool.

The bending moment generated by the prestressed steel bar on the pool wall is opposite to the bending moment generated by other loads. The bending moment generated at the bottom causes the inside of the pool wall to be bent, while the bending moment generated at the root of the pool wall causes the outside of the pool wall to be bent.

②Mechanical analysis of cylindrical digester under various load conditions

The force diagrams of the cylindrical digester under various load conditions are shown in Fig. 9 to Fig. 12 . Among them, Figure 9-1 is a hoop force diagram, Figure 9-2 is a vertical force diagram, Figure 9-3 is a hoop bending moment diagram, and Figure 9-4 is a vertical bending moment diagram. It can be seen that the hoop pressure generated by the prestressed steel bar not only offsets the hoop tension generated by other loads, but also offsets a part of the bending moment on the pool wall.

When gravity and prestress act together, the wall of the digester is under pressure in the circumferential direction; the vertical pressure is mainly generated by gravity and is distributed in a triangle; the variation trend of the circumferential bending moment and vertical bending moment along the height is the same, similar to that of prestress alone The case where the vertical bending moment plays a controlling role.

From Figures 10-1 to 10-4 and Figures 11-1 to 11-4, it can be seen that after adding water and gas to the tank, the force on the digester becomes more favorable, both hoop and vertical compression, hoop bending moment and The vertical bending moment is controlled within 50kN.m/m, and the bending moment at the corresponding height is smaller than that of the empty tank under the action of gravity and prestress. The digestion tank when the empty tank produces the maximum bending moment of internal bending, which belongs to a kind of worst case.

It can be seen from Figure 12-1 to Figure 12-4 that the temperature has a great influence on the bending moment of the digester, so that almost the entire digester is pulled in the ring or vertical outside, and the maximum value of the vertical bending moment reaches 320kN.m/ m, due to the rigid connection between the pool wall and the foundation, the inner bending moment is generated within one meter of the bottom. This is another most unfavorable situation for digester forces.

③Deformation of cylindrical digester under various load conditions

The digester mainly produces circumferential, vertical and total displacements under various load conditions, and the displacements are symmetrical along any meridian. The deformation diagrams of the digester are shown in Figure 13-1 to Figure 13-6. Among them: Figure 13-1 is the combined effect of gravity, water pressure and air pressure standard value; Figure 13-2 is the effect of prestress standard value; Figure 13-3 is the joint action of prestress and gravity; Figure 13-4 is the effect of gravity, prestress Joint action of stress and water pressure (closed water test); Figure 13-5 is the joint action of gravity, prestress, water pressure and air pressure (closed water and air test); Figure 13-6 is gravity, prestress, water pressure, air pressure and The temperature works together.

From the above deformation diagram, it can be seen intuitively that the pool wall expands outward under the action of gravity, water pressure, and air pressure, while the prestressed steel bars restrain the deformation. The maximum value is reached near 6.1m, and under the combined action of the two, a part of the deformation is canceled out, which makes the force of the digester more reasonable.

5. Dynamic characteristics of large cylindrical digester

The seismic wave is input, and the dynamic analysis of the simplified model of the above-mentioned large-scale cylindrical digester is carried out by using the method of three-dimensional overall modeling, and the dynamic characteristics of the large-scale cylindrical digester are obtained.

The mode shapes and frequencies of the cylindrical digester in the empty and full states were obtained by modal analysis. Due to the difference in quality between the two cases, the frequency difference is quite large. The first ten vibration modes are the same, and the first ten The first-order natural frequencies are shown in Table 4.

Table 4 Natural vibration frequency and period of cylindrical digester

Mode shape Frequency f/Hz Period T/s empty pool full pool empty pool full pool 1 12.7647 6.0924 0.0783 0.1641 2 12.7647 6.0924 0.0783 0.1641 3 13.7237 6.1243 0.0729 0.1633 4 13.7237 6.1243 0.0729 0.1633 5 15.1195 6.7084 0.0661 0.1491 6 15.1195 6.7084 0.0661 0.1491 7 15.9565 7.1190 0.0627 0.1405 8 15.9565 7.1190 0.0627 0.1405 9 19.7187 8.9763 0.0507 0.1114 10 20.2335 8.9763 0.0494 0.1114

The vibration diagrams of the first ten orders above are shown in Figure 14-1 to Figure 14-10:

Mode shape 1 - expansion and contraction of the pool wall in the directions of 0°, 120° and 240°;

Mode shape 2—the expansion and contraction of the pool wall in the direction of 30 degrees, 150 degrees and 270 degrees;

Mode shape 3 - left and right swing;

Mode shape 4 - swing back and forth;

Mode shape 5—the expansion and contraction of the pool wall in the direction of 30 degrees, 120 degrees, 210 degrees and 300 degrees;

Mode shape 6—the expansion and contraction of the pool wall in the directions of 45 degrees, 135 degrees, 225 degrees and 315 degrees;

Mode shape 7—the expansion and contraction of the pool wall in the direction of 45 degrees and 225 degrees;

Mode shape 8—the expansion and contraction of the pool wall in the direction of 90 degrees and 270 degrees;

Mode shape 9—the expansion and contraction of the pool wall in the directions of 0 degrees, 72 degrees, 144 degrees, 216 degrees and 288 degrees;

Mode shape 10—the expansion and contraction of the pool wall in the directions of 54.5 degrees, 126.5 degrees, 198.5 degrees, 270.5 degrees and 342.5 degrees.

Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments, and the above-mentioned specific embodiments are only illustrative, rather than restrictive. Under the enlightenment of the present invention, without departing from the gist of the present invention and the protection scope of the claims, many modifications can be made, and these all belong to the protection of the present invention.

Claims (5)

1. A static and dynamic analysis method for a large-scale columnar digester, characterized in that it may further comprise the steps: Step 1: Determine the structural parameters, material parameters and geological parameters of the digester; Step 2: Define the load and value range of the digester; Step 3: Establish and calculate the simplified model of the digester based on the plate-shell element and three-dimensional block element in the ANSYS system; Step 4: Static analysis of the simplified model of the above-mentioned large cylindrical digester: (4-1) Determine the combination of digester loads; (4-2) Determine the combination of working conditions and satisfy the following formulas (1) and (2): The structural components of the pool are calculated according to the limit state of the bearing capacity. Except for the overall stability check calculation of the structure, the rest adopt the sub-item coefficient design expression. And should satisfy the following formula: γ ₀ S≤R (1) Where: γ ₀ ——structural importance coefficient. Generally, the safety level of the pool is taken as level two, and γ ₀ is taken as 1.0; S—the combined design value of action and effect; R——Design value of resistance of structural member. The combined design value S of action effect should satisfy: S＝γ _G1 C _G1 G _1k +γ _G (C _w F _wk +C _p F _pk )+ψ _c γ _Q (C _gas F _gask +C _t F _tk ) (2) in: γ _G1 ——digester self-weight partial coefficient, take 1.2; when it is beneficial to the structure, take 1.0; C _G1 ——digester self-weight effect coefficient; G _1k ——Standard value of self-weight of digester; γ _G ——partial coefficient of water pressure and prestress acting on the digester, 1.27 when it is unfavorable to the structure; Take 1.0 when it is beneficial to the structure; C _w —coefficient of water pressure effect in the pool; F _tk — standard value of water pressure in the pool; C _p —coefficient of prestressing effect; F _tk — standard value of pre-stressing force; γ _Q ——partial coefficient of air pressure and temperature acting on the digester, take 1.40; ψ _c —coefficient of combination of two or more variable effects, take 0.9; C _t —coefficient of temperature (humidity) effect effect; F _tk — standard value of temperature (humidity) effect; (4-3) Equivalent transformation of prestressed load: Take a thin-walled rotating cylinder with a ratio of inner diameter to outer diameter close to 1, and there is a uniform pressure p acting on the outside; Taking a circular platform with a height of dz, this section of curved thin-walled cylinder can be approximately regarded as the side of the circular platform under the action of uniform force, the dimensions are: average radius R, thickness t, the angle between the outer wall and the horizontal plane is α, and the angle of the ring is from β ₁ to _β2 ; Under the action of uniform pressure p on the outside of the thin-walled cylinder, hoop stress σ _θ is generated in the circumferential direction, and radial stress σ _r is generated in the radial direction; The radial stress changes from -p on the outside of the pool wall to 0 on the inside of the pool wall. When the wall thickness is very thin, σ _r is very small compared with σ _θ . Therefore, σ _r is often negligible, and it is assumed that σ _θ is at uniform distribution in the section, then the concentrated force T on the section in the height direction is the product of σ _θ and the area of the section; Let the y-coordinate axis of the simplified model of the digester be the symmetry axis of the fan-shaped ring, and take a micro-segment dβ, then the force acting on the dβ segment is: dP=pRlcos(α)dβ (3) The force acting on the β ₁ -β ₂ fan-shaped ring is: $\underset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; pR</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&beta;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$ Considering the force balance in the y direction on the ring, and β ₂ =180-β ₁ , then $\underset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; \&beta;</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; pR</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&beta;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$ Formula (5) simplifies to: 2pRlcos(α)cos(β ₁ )=2Tcos(β ₁ ) (6) Namely: pRlcos(α)=T Among them: T—the ring tension of all prestressed steel bars within the range of length l (N/m ² ) Here, T＝Ay·(σ _con -∑σ _li ) Where: Ay—the cross-sectional area of all prestressed steel bars within the range of length l (mm ² ) σ _con — Tension control stress of prestressed steel bars (N/mm ² ) ∑σ _li — total prestress loss of prestressed steel bars (N/mm ² ) Equivalent pressure of prestressed steel bar: $\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Ay</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; con</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; lt</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; Rl</span>}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$ R——circumferential horizontal radius of the pool body within the range of l, taking the average value (m); α—the angle between the shell normal and the horizontal plane. Through the above calculation, the internal force of the hoop prestressed steel bar is transformed into an equivalent external load; (4-4) Internal force analysis of cylindrical digester under load standard value; (4-5) The force analysis of the cylindrical digester under the design value; Step 5: Input seismic waves, and use the three-dimensional overall modeling method to perform dynamic analysis on the simplified model of the above-mentioned large-scale cylindrical digester, and obtain the dynamic characteristics of the large-scale cylindrical digester. 2. the static dynamic analysis method of large cylindrical digester according to claim 1, wherein, said calculation model is the calculation model on rigid foundation, carries out internal force calculation and analysis with ANSYS system, the pond wall of described digester The shell unit is adopted, the foundation of the digester adopts a solid unit, and a fixed constraint is imposed on the position of the cast-in-situ pile on the bottom surface of the foundation. 3. the static dynamic analysis method of large cylindrical digester according to claim 1, wherein, the combination situation of described this digester load is: Combination of standard values for the calculation of prestressed reinforcement, the combination of which is formed by gravity + water pressure + air pressure; When the tank is empty, the most unfavorable load combination that produces vertical bending moment is formed by gravity + prestress; Load combination during closed water test, the combination is formed by gravity + prestress + water pressure; The combination of loads in closed water and closed air tests is formed by gravity + prestress + water pressure + air pressure; The load combination in the normal use stage is formed by gravity + prestress + water pressure + air pressure + temperature. 4. The static and dynamic analysis method of a large cylindrical digester according to claim 1, wherein the force analysis of the cylindrical digester in the step 4 under the design value includes: The internal force of the cylindrical digester under the equivalent pressure of prestress; Stress analysis of cylindrical digester under various load conditions; Deformation of a cylindrical digester under various load cases. 5. The static dynamic analysis method of a large cylindrical digester according to claim 1, wherein the obtained dynamic characteristics of the large cylindrical digester are mode shapes and frequencies in both states of an empty pond and a full pond , the first ten vibration modes are as follows: Mode shape 1 is the expansion and contraction of the pool wall in the directions of 0 degrees, 120 degrees and 240 degrees; Mode shape 2 is the expansion and contraction of the pool wall in the directions of 30 degrees, 150 degrees and 270 degrees; Mode shape 3 is left and right swing; Mode shape 4 is swinging back and forth; Mode shape 5 is the expansion and contraction of the pool wall in the directions of 30 degrees, 120 degrees, 210 degrees and 300 degrees; Mode shape 6 is the expansion and contraction of the pool wall in the directions of 45 degrees, 135 degrees, 225 degrees and 315 degrees; Mode shape 7 is the expansion and contraction of the pool wall in the direction of 45 degrees and 225 degrees; Mode shape 8 is the expansion and contraction of the pool wall in the direction of 90 degrees and 270 degrees; Mode shape 9 is the expansion and contraction of the pool wall in the directions of 0 degrees, 72 degrees, 144 degrees, 216 degrees and 288 degrees; Mode shape 10 is the expansion and contraction of the pool wall in the directions of 54.5 degrees, 126.5 degrees, 198.5 degrees, 270.5 degrees and 342.5 degrees.

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