A method for calculating the thickness of POZD explosion-proof coating

Abstract

This invention relates to safety protection technology, specifically a method for calculating the thickness of a POZD explosion-proof coating. The invention determines the critical fracture thickness of the coating by analyzing the maximum fragmentation velocity within the explosive projection area on the back of the substrate during a contact explosion test and the coating's fracture characteristics. Furthermore, based on the relationship between the maximum fragmentation velocity and the proportional plate thickness, the critical fracture thickness of the coating is directly calculated using the proportional plate thickness. The method provided by this invention can predict the thickness required for the coating to reach critical fracture, providing technical support for the design of POZD explosion-proof coating thicknesses on reinforced concrete structures. It can also be used to evaluate the explosion-proof performance of reinforced concrete structures coated with POZD explosion-proof coatings, thereby effectively protecting against concrete fragments generated by explosions.

Description

Technical Field

[0001] This invention relates to safety protection technology, specifically a method for calculating the thickness of POZD explosion-proof coating. Background Technology

[0002] Concrete debris generated during terrorist bombings or accidental explosions of flammable and explosive materials, especially near-field explosions, travels at high speeds and lasts for extended periods, posing a serious threat to the safety of personnel and equipment within the structure. To address this issue, spraying a polyurea explosion-proof coating onto the inner surface of reinforced concrete buildings (structures) utilizes its large deformation capacity to effectively contain concrete debris generated on the back surface of the reinforced concrete under explosive loads due to delamination. This provides an effective safety protection solution.

[0003] The preparation apparatus and methods for polyurea explosion-proof coating materials, as well as the spraying equipment and methods, are relatively mature, and their explosion-proof effects are good. POZD explosion-proof coatings belong to one type of polyurea explosion-proof coating materials. In practical applications of anti-terrorism and explosion protection, how to calculate the required thickness of the polyurea explosion-proof coating according to actual requirements is a key issue that needs to be addressed. Currently, the selection of coating thickness is mostly based on experience, and experiments are used to verify the actual explosion-proof effect of the coating at that thickness. This easily leads to insufficient or excessive coating thickness, resulting in increased actual efficiency and cost, directly affecting the engineering application of polyurea explosion-proof coatings. Patent CN111429025A discloses a design calculation method for elastic coatings to prevent the collapse of reinforced concrete slabs. This method can calculate the coating thickness based on the collapse coefficient, but it does not address the quantitative correlation between the coating thickness and the dynamic response between the explosive structure and the reinforced concrete structure under the action of an explosive shock wave, nor does it provide specific parameters for evaluating coating cracking, making it difficult to meet the precise design requirements of polyurea explosion-proof coatings under different conditions. Research on the explosion-proof mechanism of polyurea coatings has revealed that the coating is most prone to cracking within the explosive projection area. The velocity of concrete fragments formed after the explosion of reinforced concrete structures has a significant impact on the coating thickness. However, no corresponding engineering algorithm has been found for the design of polyurea explosion-proof coating thickness that takes into account comprehensive factors such as the thickness of reinforced concrete structures, the mass of explosives, the shape of explosives, and the velocity of concrete fragments. Summary of the Invention

[0004] In response to the problems mentioned in the background art, the purpose of this invention is to provide a method for calculating the thickness of POZD blast-resistant coating. This method determines the critical fracture thickness of the sprayed POZD blast-resistant coating by considering factors such as explosive mass, explosive shape, reinforced concrete structure thickness, and concrete fragmentation velocity. This method can be used to evaluate the blast resistance performance of reinforced concrete structures sprayed with POZD blast-resistant coating, thereby effectively protecting against concrete fragments generated by an explosion.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for calculating the thickness of a POZD explosion-proof coating includes the following steps:

[0007] Step S1: Determine the explosive mass Q according to design requirements. TNT and the thickness H of the reinforced concrete structure;

[0008] Step S2: Define the explosive shape as a geometric body with a uniform cross-section. Calculate the explosive shape factor λ based on the explosive length a and explosive width b. Calculate the explosive centroid height based on the explosive height h. ;

[0009] Step S3: The mass Q of the explosive in step S1 TNT The thickness H of the reinforced concrete structure, the explosive shape factor λ obtained in step S2, and the height h of the explosive centroid. c The parameters are combined into one, and this parameter is named proportional plate thickness T. S ;

[0010] Step S4: The explosive is placed on the front of the reinforced concrete structure and detonates, forming a concrete fragment flow within the explosive projection area on the back of the reinforced concrete structure. The maximum concrete fragment velocity V of the concrete fragment flow is related to the proportional slab thickness T. S There exists a functional relation ;

[0011] Step S5: Set the critical fracture thickness of the POZD explosion-proof coating on the back of the reinforced concrete structure to T. pozd Then T pozd There is a functional relationship with V. ;

[0012] Step S6: Convert the functional relationship With functional relationship By combining the two equations, the proportional plate thickness T is obtained. S and the critical fracture thickness T of POZD anti-explosion coating pozd Functional relationship F Thus utilizing the proportional plate thickness T S Directly calculate the critical fracture thickness T of the coating pozd .

[0013] In step S2, the geometric body with a constant cross-section is a cuboid or a cylinder, and the explosive shape factor λ is calculated using the following formula:

[0014]

[0015] In the above formula, 'b' represents the length of the explosive cross-section in cm; 'b' represents the width of the explosive cross-section in cm.

[0016] In step S3, the height of the explosive's centroid Calculate using the following formula:

[0017]

[0018] In the above formula, h represents the height of the explosive, in cm.

[0019] In step S3, the proportional plate thickness T S Calculate using the following formula:

[0020] (1)

[0021] In formula (1), the proportional plate thickness T S The unit is cm / g 1 / 3 .

[0022] In step S4, the functional relationship is... The following method is used to establish it:

[0023] Step B1: Prepare specimen A with length A, width B, and thickness H. Specimen A is a reinforced concrete slab, and the steel reinforcement and cement grade used in specimen A are the same as those used in reinforced concrete structures; [The text then abruptly shifts to a different topic:] ...a mass Q... TNT The explosive was placed on the front of specimen A for an explosion test, and the test data of concrete fragment flow on the back of specimen A were obtained.

[0024] Step B2: Based on the experimental data, conduct a velocity characteristic analysis of the concrete fragment flow. It can be determined that the concrete fragment velocity at the front end of the concrete fragment flow in the explosive projection area on the back of specimen A is the largest. The concrete fragment velocity at this point is set as the maximum concrete fragment velocity V.

[0025] Step B3: Based on the factors affecting the concrete fragmentation velocity, establish a concrete fragmentation velocity model under the condition of a uniform cross-section geometric charge through dimensional analysis.

[0026] Step B4: Based on the concrete fragment velocity model obtained in Step B3, and combined with the analysis of experimental results, establish a formula for predicting the maximum concrete fragment velocity, i.e., a functional relationship. The formula was verified through experimental data and is as follows:

[0027] (1)

[0028] In equation (1), V is the maximum concrete fragment velocity, in m / s.

[0029] In step S5, T pozd Functional relationship with V The following method is used to establish it:

[0030] Step L1: Fabricate specimen B, which consists of a substrate and a POZD explosion-proof coating sprayed on the back of the substrate. The substrate is the same as that of specimen A; [The following appears to be a separate, unrelated step:] ...to prepare a specimen of mass Q... TNT Explosives were placed on the front of the substrate for an explosion test;

[0031] Step L2: Keeping the substrate parameters and POZD explosion-proof coating thickness constant, change the explosive mass to obtain test data on the critical fracture thickness of the coating;

[0032] Step L3: Based on the experimental data of the critical fracture thickness of the coating, fit and establish the maximum concrete fragmentation velocity V and the critical fracture thickness of the coating T. pozd Functional relation And verified through experimental data, the functional relationship Specifically as follows:

[0033] (2)

[0034] In equation (2), T pozd The critical fracture thickness of the coating is expressed in mm.

[0035] In step S6, the critical fracture thickness T of the coating is... pozd The following functional relationship is used for calculation:

[0036] When E≤ When ≤F,

[0037] when When F > F, take T. pozd =3mm;

[0038] In the formula, T pozd E represents the critical fracture thickness of the coating, in mm; F ​​represents... The interval parameters were obtained experimentally.

[0039] This invention provides a method for calculating the critical thickness of POZD anti-explosion coating under TNT explosive load, which can accurately predict the thickness required when the coating is critically fractured, providing technical support for the design of POZD anti-explosion coating thickness for reinforced concrete structures. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the present invention.

[0041] Figure 2 This is a top view of specimen B used in Example 1.

[0042] Figure 3 for Figure 2 Top view. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. It should be noted that the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] like Figure 1 As shown, the present invention provides a method for calculating the thickness of POZD explosion-proof coating, and the specific steps of the method are shown in the following Example 1.

[0045] Example 1

[0046] There is a C40 reinforced concrete structure. The upper limit of contact explosion on the outer surface of the C40 reinforced concrete structure is designed to be 800g of TNT explosive. If a POZD anti-explosion coating is sprayed on the inner surface of the C40 reinforced concrete structure, the specific steps of the design method for the thickness of the POZD anti-explosion coating are as follows.

[0047] Step S1: Determine the explosive mass Q according to design requirements. TNT and the thickness H of the reinforced concrete structure; the mass Q of the TNT explosive in Example 1 TNT The weight is 800g, and the thickness H of the C40 reinforced concrete structure is measured to be 15cm.

[0048] Step S2: Set the explosive shape to a geometric shape with a uniform cross-section; in this example, a cuboid is chosen. Calculate the explosive shape factor λ based on the explosive length *a* and width *b*. Calculate the explosive centroid height based on the explosive height *h*. ;

[0049] The TNT explosive has a length a of 10cm, a width b of 10cm, and a height h of 5cm; the formula for calculating the explosive shape factor λ is:

[0050]

[0051] Substituting the length a=10cm and width b=10cm of the TNT explosive into the above formula, we get the explosive shape factor λ=1.

[0052] Explosive center of mass height The calculation formula is:

[0053]

[0054] Substituting the TNT explosive height h = 5cm into the above formula, we obtain the height of the explosive's centroid. =2.5cm.

[0055] Step S3: The mass Q of the explosive in step S1TNT The thickness H of the reinforced concrete structure, the explosive shape factor λ obtained in step S2, and the height h of the explosive centroid. c The parameters are combined into one, and this parameter is named proportional plate thickness T. S ;

[0056] proportional plate thickness T S The calculation formula is:

[0057]

[0058] Q TNT =800g, λ=1, Substituting 2.5cm and H=15cm into the above formula, we get the proportional plate thickness T. S =1.885cm / g 1 / 3 ;

[0059] Step S4: The explosive is placed on the front of the reinforced concrete structure and detonates, forming a concrete fragment flow within the explosive projection area on the back of the reinforced concrete structure. The maximum concrete fragment velocity V of the concrete fragment flow is related to the proportional slab thickness T. S There exists a functional relation In this example, the functional relationship is... Established using the method provided by this invention:

[0060] Step B1: Prepare specimen A with a length of 100cm, a width of 100cm, and a thickness of 15cm. Specimen A is a reinforced concrete specimen. Specimen A has the same structural steel bars and cement grade as the reinforced concrete structure. Place 800g of TNT explosive on the front of specimen A for an explosion test and obtain test data on the concrete fragment flow on the back of specimen A.

[0061] Step B2: Based on the experimental data, conduct a velocity characteristic analysis of the concrete fragment flow. It can be determined that the concrete fragment velocity at the front end of the concrete fragment flow in the explosive projection area on the back of specimen A is the largest. The concrete fragment velocity at this point is set as the maximum concrete fragment velocity V.

[0062] Step B3: Based on the factors affecting the rate of concrete fragmentation, perform dimensional analysis. Establish Concrete fragment velocity model under cuboid charge conditions; specifically, the method for establishing the concrete fragment velocity model under cuboid charge conditions in step B3 can be found in "Concrete Fragment Velocity Model under Cuboid Charge Conditions" (Engineering Failure Analysis, 167 (2025) 109047, Guo Shixu, He Xiang, Liu Fei, et al.)

[0063] Step B4: Based on the concrete fragment velocity model obtained in Step B3, and combined with the analysis of experimental results, establish a formula for predicting the maximum concrete fragment velocity, i.e., a functional relationship. And verified through experimental data, in this example, the functional relationship... Using the formula (1) established in this invention:

[0064] (1)

[0065] In equation (1), V is the maximum concrete fragment velocity, in m / s.

[0066] Step S5: Set the critical fracture thickness of the POZD explosion-proof coating on the back of the reinforced concrete structure to T. pozd Then T pozd There is a functional relationship with V. In this example, the functional relationship is... Using the formula (2) established in this invention:

[0067] (2)

[0068] In equation (2), T pozd The critical fracture thickness of the coating is expressed in mm.

[0069] Step S6: Convert the functional relationship With functional relationship By combining the two equations, the proportional plate thickness T is obtained. S and the critical fracture thickness T of POZD anti-explosion coating pozd Functional relationship F Thus utilizing the proportional plate thickness T S Directly calculate the critical fracture thickness T of the coating pozd Critical fracture thickness T of the coating pozd The calculation formula is:

[0070] When E≤ When ≤F,

[0071] when When F > F, take T. pozd =3mm;

[0072] In the formula, T pozd E represents the critical fracture thickness of the coating, in mm; F ​​represents... The interval parameters were obtained experimentally.

[0073] The proportional plate thickness T in step S5 S =1.885cm / g 1 / 3 First, perform an interval determination; we can then obtain that E ≤ ≤F, substitute The critical fracture thickness T of the coating was obtained. pozd =8.1mm.

[0074] In the above Example 1, the functional relationship is... The following method is used to establish it:

[0075] Step L1: Prepare specimen B, such as Figure 2-3 As shown, specimen B consists of a substrate and a POZD anti-explosion coating sprayed on the back of the substrate. The substrate is the same as that of specimen A; a mass of Q is... TNT TNT explosives were placed on the front of the substrate for an explosion test;

[0076] Step L2: Keeping the substrate parameters and POZD explosion-proof coating thickness constant, change the explosive mass to obtain test data on the critical fracture thickness of the coating;

[0077] Step L3: Based on the experimental data of the critical fracture thickness of the coating, fit and establish the maximum concrete fragmentation velocity V and the critical fracture thickness of the coating T. pozd Functional relation .

[0078] The innovation of this invention lies in the proportional plate thickness T proposed in this invention. S Compared to common proportional plate thickness There is a difference; for reinforced concrete slabs, a proportional slab thickness is usually used. To measure the impact of explosives under contact explosion conditions, the proportional plate thickness of this invention... The invention takes into more detail the effects of changes in explosive shape and centroid height under the same explosive mass conditions; based on the study of the partitioned energy dissipation mechanism and fracture mechanism of polyurea coating, the invention determines that the coating in the explosive projection area is most prone to fracture; the invention determines the critical fracture thickness of the coating by comparing the maximum fragmentation velocity in the explosive projection area on the back of the substrate with the coating fracture results in contact explosion tests.

[0079] The critical fracture thickness T of the coating of the present invention pozd The physical meaning of the interval parameters used in the calculation formula is as follows: For practical applications, when the coating is extremely thin, its critical fracture thickness has limited significance. At this point, the spraying process has a more significant impact because a large number of randomly distributed microbubbles exist within the coating during spraying. Stress concentration around these microbubbles may trigger coating tearing. Considering the coating's anti-explosion effect and safety in practical applications, this formula takes T as... pozd =3mm is used as the lower limit of the critical cracking thickness of the coating. In addition, increasing the coating thickness will lead to a corresponding increase in the amount of spraying work and economic costs, and the actual improvement in effect is not significant beyond a certain thickness.

[0080] The parts of this invention not described in detail are prior art.

Claims

1. A method for calculating the thickness of POZD explosion-proof coating, characterized in that: Includes the following steps: Step S1: Determine the explosive mass Q according to design requirements. TNT and the thickness H of the reinforced concrete structure; Step S2: Define the explosive shape as a geometric body with a uniform cross-section. Calculate the explosive shape factor λ based on the explosive length a and explosive width b. Calculate the explosive centroid height based on the explosive height h. ; Step S3: The mass Q of the explosive in step S1 TNT The thickness H of the reinforced concrete structure, the explosive shape factor λ obtained in step S2, and the height h of the explosive centroid. c The parameters are combined into one, and this parameter is named proportional plate thickness T. S ; Step S4: The explosive is placed on the front of the reinforced concrete structure and detonates, forming a concrete fragment flow within the explosive projection area on the back of the reinforced concrete structure. The maximum concrete fragment velocity V of the concrete fragment flow is related to the proportional slab thickness T. S There exists a functional relation ; Step S5: Set the critical fracture thickness of the POZD explosion-proof coating on the back of the reinforced concrete structure to T. pozd Then T pozd There is a functional relationship with V. ; Step S6: Convert the functional relationship With functional relationship By combining the two equations, the proportional plate thickness T is obtained. S and the critical fracture thickness T of POZD anti-explosion coating pozd Functional relationship F Thus utilizing the proportional plate thickness T S Directly calculate the critical fracture thickness T of the coating pozd .

2. The method for calculating the thickness of a POZD explosion-proof coating according to claim 1, characterized in that: In step S2, the geometric body with a constant cross-section is a cuboid or a cylinder, and the explosive shape factor λ is calculated using the following formula: ； In the above formula, 'b' represents the length of the explosive cross-section in cm; 'b' represents the width of the explosive cross-section in cm.

3. The method for calculating the thickness of a POZD explosion-proof coating according to claim 1, characterized in that: In step S3, the height of the explosive's centroid Calculate using the following formula: ； In the above formula, h represents the height of the explosive, in cm.

4. The method for calculating the thickness of a POZD explosion-proof coating according to claim 1, characterized in that: In step S3, the proportional plate thickness T S Calculate using the following formula: （1） In the above formula (1), the proportional plate thickness T S The unit is cm / g 1 / 3 .

5. The method for calculating the thickness of a POZD explosion-proof coating according to claim 1, characterized in that: In step S4, the functional relationship is... The following method is used to establish it: Step B1: Prepare specimen A with length A, width B, and thickness H. Specimen A is a reinforced concrete slab, and the steel reinforcement and cement grade used in specimen A are the same as those used in reinforced concrete structures; [The text then abruptly shifts to a different topic:] ...a mass Q... TNT The explosive was placed on the front of specimen A for an explosion test, and the test data of concrete fragment flow on the back of specimen A were obtained. Step B2: Based on the experimental data, conduct a velocity characteristic analysis of the concrete fragment flow. It can be determined that the concrete fragment velocity at the front end of the concrete fragment flow in the explosive projection area on the back of specimen A is the largest. The concrete fragment velocity at this point is set as the maximum concrete fragment velocity V. Step B3: Based on the factors affecting the concrete fragmentation velocity, a concrete fragmentation velocity model under the condition of uniform cross-section irregular charge is proposed through dimensional analysis. Step B4: Based on the concrete fragment velocity model obtained in Step B3, and combined with the analysis of experimental results, establish a formula for predicting the maximum concrete fragment velocity, i.e., a functional relationship. The formula was verified through experimental data and is as follows: （1） In equation (1), V is the maximum concrete fragment velocity, in m / s.

6. The method for calculating the thickness of a POZD explosion-proof coating according to claim 1, characterized in that: In step S5, T pozd Functional relationship with V The following method is used to establish it: Step L1: Fabricate specimen B, which consists of a substrate and a POZD explosion-proof coating sprayed on the back of the substrate. The substrate is the same as that of specimen A; [The following appears to be a separate, unrelated step:] ...to prepare a specimen of mass Q... TNT Explosives were placed on the front of the substrate for an explosion test; Step L2: Keeping the substrate parameters and POZD explosion-proof coating thickness constant, change the explosive mass to obtain test data on the critical fracture thickness of the coating; Step L3: Based on the experimental data of the critical fracture thickness of the coating, fit and establish the maximum concrete fragmentation velocity V and the critical fracture thickness of the coating T. pozd Functional relation And verified through experimental data, the functional relationship Specifically as follows: （2） In equation (2), T pozd The critical fracture thickness of the coating is expressed in mm.

7. The method for calculating the thickness of a POZD explosion-proof coating according to claim 1, characterized in that: In step S6, the critical fracture thickness T of the coating is... pozd The following functional relationship is used for calculation: When E≤ When ≤F, ; When F > F, take T. pozd =3mm; In the formula, T pozd E represents the critical fracture thickness of the coating, in mm; F ​​represents... The interval parameters were obtained experimentally.

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