Novel structure cover plate meeting maintenance pedestrian requirement and design method of novel structure cover plate

Abstract

The invention relates to the technical field of cover plates, discloses a novel cover plate based on an arch structure and a design method of the novel cover plate, and aims to solve the problem that material distribution and stress characteristics of a traditional tunnel maintenance path and sidewalk cover plate are not matched. The cover plate adopts an innovative structural form that the upper part is flat and the lower part is arched, material utilization is optimized through thickness gradient distribution and parabolic arch design, and the midspan thickness is obviously reduced, so that the material consumption and the engineering cost are reduced. The design method comprises the following steps: determining reference geometric parameters and bearing performance indexes, calculating a total load, checking bending strength, compression strength and shear strength, and generating a thickness distribution function and an engineering drawing. The method is suitable for various tunnel engineering scenes, has remarkable economical efficiency, durability and environmental adaptability, provides an efficient and reliable solution for tunnel cover plate design, and has important engineering significance and popularization value.

Description

Technical Field

[0001] The invention relates to the technical field of cover plates, and in particular to a new type of structural cover plate that meets the needs of maintenance personnel and a design method thereof. Background Art

[0002] In tunnel engineering, maintenance road and pedestrian cover plates are important components to ensure daily maintenance and safe passage of tunnels. Traditional cover plates mostly adopt equal thickness flat plate structure, which is simple in design and easy to construct, but there are significant technical problems in practical application: material distribution does not match the stress characteristics. Specifically, there is material redundancy in the mid-span area, while the material utilization rate is low in the edge area due to stress concentration, and the overall material utilization rate is only 65%-70%. This design not only wastes a lot of building materials, but also increases the cost of the project.

[0003] In order to improve the above problems, the existing technology has proposed improved solutions such as local ribs or prestressed reinforcement. However, although these methods can improve the structural performance to a certain extent, they significantly increase the complexity of construction and fail to fundamentally achieve the optimal matching of material distribution and force characteristics. Therefore, how to develop a new cover plate structure and its design method that can not only meet the load-bearing requirements, but also significantly save materials and reduce engineering costs has become a technical problem that needs to be solved urgently in the current tunnel engineering field. Summary of the invention

[0004] To solve the above problems, the present invention proposes a new cover plate design method based on an arch structure. By reasonably optimizing the material distribution and structural form, the thickness of the middle part of the cover plate is significantly reduced while meeting the pedestrian load requirements, thereby achieving the purpose of saving materials and reducing costs, and effectively improving the overall mechanical properties and durability of the cover plate.

[0005] The technical solution adopted by the present invention is:

[0006] A new type of cover plate based on an arch structure, which is in the shape of a rectangular plate as a whole, with a flat top surface and an inwardly concave bottom surface to form a flat top and an arched bottom structure; a plurality of weight-reducing holes are arranged at equal intervals on the new type of cover plate based on an arch structure, and the weight-reducing holes penetrate from the top surface of the cover plate to its bottom surface.

[0007] A cover plate design method, which is aimed at the above-mentioned new cover plate based on the arch structure, comprises the following steps:

[0008] Step 1: Based on engineering requirements and material properties, determine the geometric parameters and performance indicators of the cover plate, and set the minimum mid-span thickness as the variable to be determined;

[0009] Step 2: Calculate the deadweight of the cover plate and the crowd load, and establish a total load model for subsequent mechanical analysis;

[0010] Step 3: Based on the simplified curved beam model, conduct bending, compressive, and shear strength checks to determine the geometric parameters that meet the load-bearing requirements; the geometric parameters include the mid-span thickness and the springing width.

[0011] Step 4: Generate a thickness gradient distribution function and draw engineering drawings to clarify the geometric shape and construction details of the cover plate.

[0012] Step 5: Through theoretical verification, experimental testing, and multi-objective optimization, ensure that the design results meet the performance requirements and achieve material savings.

[0013] Furthermore, in Step 1, according to the actual requirements of the tunnel project, determine the load-bearing performance indicators and durability requirements of the cover plate; among them, the load-bearing performance indicators include bending, compressive, and shear strengths; determine the environmental grade where the cover plate is located and select the appropriate material type and design parameters accordingly.

[0014] Determine the key geometric parameters of the cover plate, including the span L, width B, thickness t, and springing width L1; set the minimum mid-span thickness t min as the variable to be solved.

[0015] According to the engineering specifications and actual requirements, select the unit weight γ of the concrete, the tensile strength f t and the compressive strength f c .

[0016] Furthermore, in Step 2, calculate the self-weight of the cover plate and the crowd load, including:

[0017] Dead load calculation: According to the unit weight γ of the cover plate material and the geometric dimensions, calculate the uniformly distributed load q1 caused by the self-weight of the cover plate; the calculation formula is as follows:

[0018]

[0019] In the formula, q1 represents the uniformly distributed load caused by the self-weight of the cover plate; γ represents the unit weight of the cover plate material; t represents the maximum thickness of the cover plate; t min represents the minimum thickness of the mid-span area of the cover plate; represents the average thickness of the cover plate along the thickness direction;

[0020] Live load statistics: Determine the crowd load, that is, the weight W 人 of an adult, and its distribution range L q ;

[0021] Total load superposition: Superpose the dead load and the live load to establish a total load model.

[0022] Furthermore, in Step 3, conduct bending, compressive, and shear strength checks based on the simplified curved beam model, including:

[0023] Simplified mechanical model: Simplify the arched cover plate into a curved beam model, and analyze its stress state under load in combination with the principles of structural mechanics;

[0024] Mid-span flexural strength check: Calculate the mid-span bending moment M and the section modulus of resistance to bending W, and check the mid-span flexural strength according to Equation 1;

[0025]

[0026] In the formula, σ t represents the maximum tensile stress at the crown of the mid-span of the cover plate; k represents the safety factor; W represents the section modulus of resistance to bending of the mid-span section of the cover plate; M represents the bending moment borne by the mid-span section of the cover plate; f t represents the design value of the tensile strength of concrete;

[0027] Among them, the calculation formula for the section modulus of resistance to bending W of the mid-span section of the cover plate is:

[0028]

[0029] In the formula, B q represents the effective width of the cover plate; t min represents the minimum thickness of the mid-span area of the cover plate; 6 is the constant coefficient of the section modulus of resistance to bending formula of the rectangular section;

[0030] By sorting out the formula, solve for the minimum thickness t min ;

[0031] Spring footing compressive strength check: According to the vertical force F R of the support and the contact area A1, check the spring footing compressive strength according to Equation 2:

[0032]

[0033] In the formula, σ c represents the maximum compressive stress at the spring footing; k represents the safety factor; F R represents the vertical reaction force of the support; A1 represents the compressive area where the spring footing contacts the ground; f c represents the design value of the compressive strength of concrete;

[0034] Thus, determine the minimum value of the spring footing width L1;

[0035] Support shear strength check: According to the shear force V of the support, check the shear strength according to Equation 3:

[0036] kV ≤ 0.7f t Bt Equation 3

[0037] In the formula, k represents the safety factor; V represents the shear force at the support; f tIt represents the design value of the tensile strength of concrete; B represents the width of the cover plate; t represents the thickness of the cover plate; 0.7 is an empirical coefficient;

[0038] This ensures that the shear strength of the bearing meets the requirements.

[0039] Furthermore, in step 4, the thickness gradient distribution function is: generating the height change function z(x) of the arch curve at the bottom of the cover plate based on the parabola equation;

[0040]

[0041] In the formula, z(x) represents the height of the arch curve at the lower edge of the cover plate; f represents the rise of the parabola; L0 represents the effective span of the arch curve; x represents the horizontal coordinate along the span direction of the cover plate; L0 - x represents the distance from the current coordinate x to the other end of the arch curve;

[0042] Among them, f = t - t min , L0 = L - 2L1;

[0043] In the formula, t represents the maximum thickness at the arch feet on both sides of the cover plate; t min represents the minimum thickness in the mid - span area of the cover plate; t - t min represents the change in the thickness of the cover plate from the arch feet to the mid - span; L represents the total span of the cover plate; L1 represents the width of a single - side arch foot; 2L1 represents the total width of the arch feet on both sides;

[0044] Determine the thickness change of the cover plate along the span direction according to the thickness distribution function t(x):

[0045] t(x) = t - z(x), (0 ≤ x ≤ L0)

[0046] In the formula, t(x) represents the thickness of the cover plate at the horizontal position x; t represents the maximum thickness at the arch feet on both sides of the cover plate; z(x) represents the height of the arch curve at the lower edge of the cover plate, and x represents the horizontal coordinate along the span direction of the cover plate;

[0047] Generate the three - dimensional geometric model and construction drawings of the cover plate according to the finally determined geometric parameters and thickness distribution function.

[0048] The beneficial effects of the present invention are:

[0049] The novel cover - plate design method based on the arch structure proposed by the present invention shows significant technical advantages in terms of mechanical properties, material saving, and construction convenience through innovative structural forms and scientific design processes. Its main beneficial effects are as follows:

[0050] 1. The material consumption is significantly reduced, and the project cost is lowered

[0051] Optimized material distribution: By adopting the structural form of flat upper and arched lower and the design of thickness gradient distribution, the thickness in the middle of the cover plate is minimized, and the thickness at the arch feet on both sides is reasonably increased, avoiding the problem of material redundancy in the mid-span area of the traditional flat plate structure. Material saving: The data of the embodiment show that the new cover plate reduces the consumption of concrete materials by about 48% compared with the traditional design, significantly reducing the material cost. Economic improvement: There is no need to configure auxiliary measures such as steel bars or ribs, which simplifies the material requirements and further saves the project cost.

[0052] 2. Significantly improved mechanical properties and more uniform and reasonable force

[0053] Excellent load dispersion effect: The arched structure can effectively transfer the load along the curve to the arch feet on both sides, significantly reducing the moment concentration effect in the mid-span area and enhancing the overall bearing capacity. Uniform stress distribution: Through the thickness gradient distribution and the parabolic arched design, the common stress concentration problems in the traditional structure are avoided, significantly improving the stability and durability of the cover plate. Meeting the requirements of multiple working conditions: Through the checking calculations of flexural strength, compressive strength and shear strength, the safety and reliability of the cover plate under various load conditions are ensured.

[0054] 3. Scientific and reasonable structural design with strong operability

[0055] Solid theoretical foundation: The design method is based on basic mechanical principles, constructing a complete design system from the theory, and the calculation process is scientific, rigorous and concise. Design cycle shortened: Through clear steps and formulaic design processes, the design efficiency is significantly improved and the design cycle is shortened. Improved construction convenience: Using plain concrete materials, there is no need for complex steel bar reinforcement or ribbing processes, which simplifies the construction process and improves the project implementation efficiency.

[0056] 4. Strong environmental adaptability and high promotion and application value

[0057] Enhanced durability: The arched structure and thickness optimization design reduce the fatigue damage of the cover plate under long-term load, extending the service life. Environmentally friendly: The reduction of material usage not only reduces resource consumption but also reduces the generation of construction waste, conforming to the development trend of green buildings. Wide application range: This design method is applicable to various scenarios such as tunnel inspection roads and sidewalks, and has wide promotion and application value.

[0058] In summary, the new cover plate design method of the present invention realizes the maximization of material utilization rate and the optimization of mechanical properties through the organic combination of the arched structure and the thickness gradient distribution, and at the same time has multiple advantages such as economy, science and operability. This method not only solves the problems of material waste and stress concentration existing in the traditional cover plate, but also provides an efficient and reliable solution for the cover plate design in the tunnel engineering field, with important engineering significance and promotion value. Description of the drawings

[0059] Figure 1 This is the overall structural schematic diagram of the novel cover plate based on the arch structure of the present invention;

[0060] Figure 2 This is the flowchart of the cover plate design method of the present invention;

[0061] Figure 3 This is the front view of the novel cover plate based on the arch structure of the present invention;

[0062] Figure 4 This is the side view of the novel cover plate based on the arch structure of the present invention;

[0063] Figure 5 This is the top view of the novel cover plate based on the arch structure of the present invention;

[0064] Figure 6 This is the force diagram of the novel cover plate based on the arch structure of the present invention;

[0065] In the figure, 1 - novel cover plate, 2 - depression, 3 - weight reduction hole. Specific embodiments

[0066] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0067] For ease of explanation, spatial relative terms such as "upper", "lower", "left", "right", etc. can be used here to describe the relationship between one element or feature shown in the figure and another element or feature. It should be understood that in addition to the orientation shown in the figure, the spatial terms are intended to include different orientations during the use or operation of the device. For example, if the device in the figure is inverted, the element described as being "below" other elements or features will be located "above" other elements or features. Therefore, the exemplary term "lower" can include both upper and lower orientations. The device can be positioned in other ways, and the spatial relative descriptions used here can be interpreted accordingly.

[0068] Aiming at the problem that the material distribution of the traditional tunnel inspection road and sidewalk cover plate does not match the force characteristics, this embodiment provides a novel cover plate based on the arch structure. As Figure 1As shown, the novel cover plate 1 based on the arch structure is integrally in the shape of a rectangular plate. Its top surface is flat to provide a flat walking surface, ensuring the safety and comfort of pedestrians. The bottom surface is recessed inward by 2 to form an upper flat and lower arched structure, effectively dispersing the load through the arched structure and reducing the moment concentration effect in the mid-span area. Five weight-reducing holes 3 are equidistantly arranged on the novel cover plate 1 based on the arch structure, and the weight-reducing holes 3 penetrate from the top surface of the cover plate to its bottom surface.

[0069] Furthermore, for the above-mentioned novel cover plate 1 based on the arch structure, this embodiment provides a cover plate design method. As Figure 2 shown, this cover plate design method includes the following steps:

[0070] Step 1: Determine the reference geometric parameters and bearing performance indicators;

[0071] Based on engineering requirements and material properties, determine the geometric parameters and performance indicators of the cover plate, and set the minimum thickness at the mid-span as the variable to be solved.

[0072] Specifically, first clarify the engineering requirements:

[0073] According to the actual requirements of the tunnel project, determine the bearing performance indicators and durability requirements of the cover plate. Among them, the bearing performance indicators include flexural, compressive, and shear strengths. Determine the environmental grade where the cover plate is located and select appropriate material types and design parameters accordingly.

[0074] Then set the reference geometric parameters: Determine the key geometric parameters of the cover plate, including the span L, width B, thickness t, and arch-foot width L1. Set the minimum thickness t min at the mid-span as the variable to be solved for subsequent mechanical analysis.

[0075] Finally, select the material properties: According to engineering specifications and actual requirements, select material parameters such as the unit weight γ of concrete, the tensile strength f t and the compressive strength f c and so on.

[0076] In this embodiment, the cover plate uses C30 concrete, with a unit weight γ = 23 kN / m 3 , a span L = 49 cm, a width B = 78 cm, a hollow single-span width B q = 18 cm, and a thickness t = 10 cm. The geometric schematic diagram of the cover plate is as Figure 3 , Figure 4 and Figure 5 shown.

[0077] Step 2: Calculate the total load:

[0078] Calculate the self-weight of the cover plate and the crowd load, and establish a total load model for subsequent mechanical analysis.

[0079] Specifically, first calculate the dead load:

[0080] According to the unit weight γ and geometric dimensions of the cover plate, calculate the uniformly distributed load q1 caused by the self-weight of the cover plate; the calculation formula is as follows:

[0081]

[0082] In the formula, q1 represents the uniformly distributed load caused by the self-weight of the cover plate; γ represents the unit weight of the cover plate material; t represents the maximum thickness of the cover plate; t min represents the minimum thickness in the mid-span area of the cover plate; represents the average thickness of the cover plate along the thickness direction.

[0083] Then conduct live load statistics: Determine the crowd load, that is, the weight W of an adult 人 , and its distribution range L q .

[0084] Finally, superimpose the total loads: Superimpose the dead load and the live load to establish a total load model.

[0085] In this embodiment, it is assumed that the self-weight of the cover plate is a uniformly distributed load, Take the human load as an 80-kg adult in the middle two spans of the cover plate, and the load "W 人 = 0.8 kN, and the distribution range on the cover plate is L distributed on both sides of the mid-span q distance, take L q = 0.1 m.

[0086] Step 3, establish a mechanical model and conduct strength check:

[0087] Based on the simplified curved beam model, conduct bending, compressive, and shear strength checks to determine the geometric parameters that meet the bearing requirements; the geometric parameters include the mid-span thickness and the springing width.

[0088] Specifically, first simplify the mechanical model: Simplify the arched cover plate into a curved beam model, apply structural mechanics and material mechanics, conduct strength checks on the structure, and determine the mid-span thickness of the cover plate that meets the strength requirements. The force of the simplified curved beam of the cover plate is as Figure 6 shown.

[0089] Then conduct mid-span bending strength check: Calculate the mid-span moment M and the section modulus of bending resistance W, and check the mid-span bending strength according to Equation 1;

[0090]

[0091] In the formula, σ t represents the maximum tensile stress at the mid-span crown of the cover plate; k represents the safety factor; W represents the section modulus of bending resistance of the mid-span section of the cover plate; M represents the moment borne by the mid-span section of the cover plate; f tRepresents the design value of the tensile strength of concrete.

[0092] Among them, the bending moment borne by the mid-span section of the cover plate, that is, the mid-span bending moment M, and its calculation formula is:

[0093]

[0094] In the formula, M represents the bending moment borne by the mid-span section of the cover plate; q1 represents the uniform load caused by the self-weight of the cover plate; B q represents the effective width of the cover plate; L represents the total span of the cover plate; W 人 represents the crowd load; L q represents the distribution range of the crowd load; L-L q represents the remaining span outside the action range of the crowd load; represents the mid-span bending moment caused by the self-weight of the cover plate; represents the mid-span bending moment caused by the crowd load.

[0095] The calculation formula for the flexural section modulus W of the mid-span section of the cover plate is:

[0096]

[0097] In the formula, B q represents the effective width of the cover plate; t min represents the minimum thickness of the mid-span area of the cover plate; 6 is the constant coefficient of the flexural section modulus formula for the rectangular section.

[0098] By sorting out the formula, solve for the minimum mid-span thickness t that meets the flexural strength requirements min :

[0099] In this embodiment, substituting the mid-span bending moment M and the section flexural coefficient W into Equation 1, it can be sorted out as:

[0100] At min 2 + Bt min + C ≥ 0

[0101] In the formula, A represents the coefficient related to the design value of the tensile strength of concrete f t and the safety factor k, B represents the coefficient related to the uniform load q1 of the self-weight of the cover plate, the span L and the width B q related, B = -3γL 2 ; C represents the comprehensive coefficient related to the self-weight of the cover plate, the crowd load and its distribution range, C = -3γtL 2 - 12W 人 L q (L - L q ) ;

[0102]

[0103] Take t min = 0.05 m.

[0104] Then, carry out the checking calculation of the arch springing compressive strength: According to the vertical force F of the support R and the contact area A1, check the arch springing compressive strength according to Equation 2:

[0105]

[0106] In the formula, σ c represents the maximum compressive stress at the arch springing; k represents the safety factor; F R represents the vertical reaction force of the support; A1 represents the compressive area where the arch springing contacts the ground; f c represents the design value of the compressive strength of concrete.

[0107] Thus, determine the minimum value of the arch springing width L1.

[0108] In this embodiment, A1 = BL1, k = 2, f c = 14.3 MPa, substitute into

[0109] Equation 2, and obtain:

[0110]

[0111] In this embodiment, take the arch springing width L1 = 0.05 m according to the structure.

[0112] Finally, carry out the checking calculation of the shear strength of the support: According to the shear force V of the support, check the shear strength according to Equation 3:

[0113] kV ≤ 0.7f t Bt Equation 3

[0114] In the formula, k represents the safety factor; V represents the shear force at the support; f t represents the design value of the tensile strength of concrete; B represents the width of the cover plate; t represents the thickness of the cover plate; 0.7 is an empirical coefficient.

[0115] Thus, ensure that the shear strength of the support meets the requirements.

[0116] In this embodiment, k = 2, t min = 0.05 m, substitute into Equation 3, and obtain:

[0117] kV = 0.7 KN, 0.7f t Bt = 78.08 KN; Equation 3 is obviously established.

[0118] Step Four, generate the thickness gradient distribution function and engineering drawings:

[0119] Generate the thickness gradient distribution function and draw engineering drawings to clarify the geometric shape and construction details of the cover plate.

[0120] Specifically, the thickness gradient distribution function:

[0121] Generate the height change function z(x) of the arch curve at the bottom of the cover plate based on the parabolic equation;

[0122]

[0123] In the formula, z(x) represents the height of the arch curve at the lower edge of the cover plate; f represents the rise of the parabola, f = t - t min ; L0 represents the effective span of the arch curve; x represents the horizontal coordinate along the span direction of the cover plate; the parabola function with the y-axis vertically upward; L0 - x represents the distance from the current coordinate x to the other end of the arch curve.

[0124] Among them, f = t - t min , L0 = L - 2L1;

[0125] In the formula, t represents the maximum thickness at the springing of both sides of the cover plate; t min represents the minimum thickness in the mid-span area of the cover plate; t - t min represents the change in the thickness of the cover plate from the springing to the mid-span; L represents the total span of the cover plate; L1 represents the width of a single springing; 2L1 represents the total width of the springings on both sides.

[0126] Determine the thickness change of the cover plate along the span direction according to the thickness distribution function t(x):

[0127] t(x) = t - z(x), (0 ≤ x ≤ L0) Equation 5

[0128] In the formula, t(x) represents the thickness of the cover plate at the horizontal position x; t represents the maximum thickness at the springing of both sides of the cover plate; z(x) represents the height of the arch curve at the lower edge of the cover plate, and x represents the horizontal coordinate along the span direction of the cover plate.

[0129] Then, draw the engineering drawings:

[0130] Generate the 3D geometric model and construction drawings of the cover plate according to the finally determined geometric parameters and thickness distribution function. Clearly mark the key dimensions, such as: span L, width B, thickness t, springing width L1, and minimum mid-span thickness t min etc., as well as construction details.

[0131] In this embodiment, t min = 0.05m, L1 = 0.05m, the rise of the arch at the lower edge of the cover plate

[0132] f = t - t min= 0.05 m, L0 = L - 2L1 = 0.39 m. Substituting these values into Equation 4 and Equation 5, we get:

[0133] z(x) = 1.31x(0.39 - x), (0 ≤ x ≤ 0.39);

[0134] t(x) = 0.1 - 1.31x(0.39 - x), (0 ≤ x ≤ 0.39);

[0135] The finally determined cover plate design drawing is as Figure 1 shown.

[0136] Step Five, Verification and Optimization:

[0137] Through theoretical verification, experimental testing and multi-objective optimization, ensure that the design results meet the performance requirements and achieve material savings; specifically:

[0138] Theoretical verification: Recheck the design results to ensure that all mechanical calculations, including bending resistance, compressive resistance, and shear resistance, meet the code requirements. Further verify the mechanical properties of the cover plate through numerical simulation or finite element analysis.

[0139] Experimental verification: Conduct full-scale tests to measure the mechanical properties and durability of the cover plate under actual load conditions. Collect experimental data and optimize the design parameters to improve the overall performance.

[0140] Multi-objective optimization: On the premise of meeting the mechanical properties, further optimize the material distribution and geometric shape to reduce the material consumption and project cost. Consider the construction convenience and aesthetics, and promote the standardized and modular design.

[0141] The above design method systematically solves the problems of low material utilization rate and stress concentration of traditional cover plates through scientific steps, from the setting of benchmark parameters to the generation of final engineering drawings. This method not only improves the mechanical properties and economy of the cover plate, but also has strong operability and popularization value, providing an efficient solution for the cover plate design in the tunnel engineering field. Through engineering quantity calculation, the new structure cover plate reduces the concrete material consumption by 48% compared with the traditional cover plate.

[0142] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A novel cover plate based on an arch structure, characterized in that: The new cover plate based on the arch structure is in the shape of a rectangular plate as a whole. Its top surface is flat, and its bottom surface is recessed inward to form an upper-flat and lower-arch structure. A number of weight-reducing holes are arranged at equal intervals on the new cover plate based on the arch structure, and the weight-reducing holes penetrate from the top surface of the cover plate to its bottom surface.

2. A cover plate design method, which is directed to the novel cover plate based on the arched structure described in claim 1, and is characterized in that, It includes the following steps: Step 1, based on engineering requirements and material properties, determine the geometric parameters and performance indicators of the cover plate, and set the minimum thickness at the mid-span as the variable to be solved; Step 2, calculate the self-weight of the cover plate and the crowd load, and establish a total load model for subsequent mechanical analysis; Step 3, based on the simplified curved beam model, conduct bending, compressive and shear strength checks to determine the geometric parameters that meet the bearing requirements; the geometric parameters include the mid-span thickness and the arch-foot width; Step 4, generate a thickness gradient distribution function and draw engineering drawings to clarify the geometric shape and construction details of the cover plate; Step 5, through theoretical verification, experimental testing and multi-objective optimization, ensure that the design results meet the performance requirements and achieve material savings.

3. The cover plate design method according to claim 2, characterized in that: In Step 1, according to the actual requirements of the tunnel project, determine the bearing performance indicators and durability requirements of the cover plate; among them, the bearing performance indicators include bending, compressive and shear strengths; determine the environmental grade where the cover plate is located and select appropriate material types and design parameters accordingly; Determine the key geometric parameters of the cover plate, including the span L, width B, thickness t, and springing width L1; set the minimum thickness t at the mid-span min as the variable to be determined; According to engineering specifications and actual requirements, select the unit weight γ, tensile strength f t and compressive strength f c .

4. The cover plate design method according to claim 2, wherein: In Step 2, the calculation of the self-weight of the cover plate and the crowd load includes: Dead load calculation: According to the unit weight γ of the cover plate material and its geometric dimensions, calculate the uniformly distributed load q1 caused by the self-weight of the cover plate; the calculation formula is as follows: Wherein, q1 represents the uniformly distributed load caused by the self-weight of the cover plate; γ represents the unit weight of the cover plate material; t represents the maximum thickness of the cover plate; t min represents the minimum thickness of the mid-span region of the cover plate; represents the average thickness of the cover plate in the thickness direction; Live load statistics: Determine the crowd load, i.e., the weight W of an adult 人 , and its distribution range L q ; Total load superposition: Superpose the dead load and the live load to establish a total load model.

5. The cover plate design method according to claim 2, wherein: In Step 3, based on the simplified curved beam model, conduct bending, compressive and shear strength checks, including: Simplified mechanical model: Simplify the arched cover plate into a curved beam model, and combine the principles of structural mechanics to analyze its stress state under the action of the load; Mid-span bending strength check: Calculate the mid-span moment M and the section bending coefficient W, and check the mid-span bending strength according to Equation 1; Where, σ t represents the maximum tensile stress at the crown of the mid-span of the cover plate; k represents the safety factor; W represents the flexural section modulus of the mid-span section of the cover plate; M represents the bending moment borne by the mid-span section of the cover plate; f t represents the design value of the tensile strength of concrete; Among them, the calculation formula for the bending section modulus W of the mid-span section of the cover plate is: where B q represents the effective width of the cover plate; t min represents the minimum thickness of the cover plate in the mid-span region; 6 is the constant coefficient of the flexural section modulus formula for rectangular sections; By arranging the formula, solve for the minimum thickness \(t\) at the mid-span that meets the flexural strength requirements min ; Arch springing compressive strength check: According to the vertical force F of the support R and the contact area A1, check the arch springing compressive strength according to Equation 2: Where, σ c represents the maximum compressive stress at the arch springing; k represents the safety factor; F R represents the vertical reaction force of the support; A1 represents the compression area where the arch springing contacts the ground; f c represents the design value of the compressive strength of concrete; From this, determine the minimum value of the arch-foot width L1; Support shear strength check: According to the support shear force V, check the shear strength according to Equation 3: kV ≤ 0.7f t Bt type 3 Wherein, k represents the safety factor; V represents the shear force at the support; f t represents the design value of the tensile strength of concrete; B represents the width of the cover plate; t represents the thickness of the cover plate; 0.7 is an empirical coefficient; From this, ensure that the support shear strength meets the requirements.

6. The cover plate design method according to claim 2, characterized in that: In Step 4, the thickness gradient distribution function is: Generate the height change function z(x) of the bottom arch curve of the cover plate based on the parabola equation; In the formula, z(x) represents the height of the arch curve at the lower edge of the cover plate; f represents the rise of the parabola; L0 represents the effective span of the arch curve; x represents the horizontal coordinate along the span direction of the cover plate; L0 - x represents the distance from the current coordinate x to the other end of the arch curve; where f = t - t min , L0 = L - 2L1; In the formula, t represents the maximum thickness at the springing of both sides of the cover plate; t min represents the minimum thickness in the mid-span area of the cover plate; t - t min represents the change in the thickness of the cover plate from the springing to the mid-span; L represents the total span of the cover plate; L1 represents the width of a single springing; 2L1 represents the total width of the springings on both sides; Determine the thickness change of the cover plate along the span direction according to the thickness distribution function t(x): t(x) = t - z(x), (0 ≤ x ≤ L0) In the formula, t(x) represents the thickness of the cover plate at the horizontal position x; t represents the maximum thickness at both arch feet of the cover plate; z(x) represents the height of the arch curve at the lower edge of the cover plate, and x represents the horizontal coordinate along the span direction of the cover plate; Generate the three-dimensional geometric model and construction drawings of the cover plate according to the finally determined geometric parameters and thickness distribution function.

Images