T-shaped stiffening ring steel cylinder concrete pipe and its design method

Abstract

The present invention relates to the technical field of pressure pipelines, and specifically relates to a T-shaped stiffening ring steel cylinder concrete pipe and its design method. Aiming at the technical problems of large diameter-thickness ratio of large-diameter pressure pipelines and strong destructiveness under high internal and external pressure, a T-shaped stiffening ring steel cylinder concrete pipe is proposed, which consists of an outer steel cylinder, a concrete layer and an inner steel cylinder from outside to inside. At least two T-shaped stiffening rings on the surface of the inner steel cylinder extend along the circumferential direction of the pipeline; and a design method for the T-shaped stiffening ring steel cylinder concrete pipe, including calculating the equivalent thickness of the pipe wall under the internal pressure condition; designing the distribution form of the steel along the radial direction; determining the filling thickness of the concrete between the inner and outer steel cylinders; performing strength checking and optimization design on the structure; Through the present invention, the design of "steel cylinder bearing internal pressure and concrete bearing external pressure" for large diameter-thickness ratio pressure pipelines is realized, giving full play to the tensile performance of steel in the construction of water network projects and enhancing the internal pressure resistance of the pipeline.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure pipelines, and particularly relates to a T-shaped stiffening ring steel cylinder concrete pipe and a design method thereof. Background Art

[0002] At present, large-diameter water pipes are mainly steel pipes and PCCP (Prestressed Concrete Cylinder Pipe). Among them, PCCP is widely used in high-pressure water supply pipeline projects due to its efficient structural design and low price.

[0003] However, in recent years, with the sharp increase in the number of pipe burst cases caused by broken wires of PCCP, people have realized the deficiencies of PCCP in terms of safety. The design of pressure pipelines first needs to consider that the structure has sufficient strength under the internal pressure condition. In addition, most of the service environments of pipelines are buried underground, and the external pressure conditions generated by vehicle loads and overburden cannot be ignored. Especially for large-diameter pipelines, due to the large diameter-thickness ratio, the destructive effect of high internal and external pressures is strong, the design difficulty is great, and there is no mature design standard for pipelines with a diameter greater than 4 meters, so independent research and development are required. At present, the structural design of large-diameter pressure pipelines mostly increases the compressive strength of the pipelines by adding stiffeners based on experience, without systematically considering the distribution form of stress in the pipe wall under internal and external pressure conditions, and cannot efficiently utilize the bearing capacity of materials. Summary of the Invention

[0004] In order to overcome the above deficiencies of the prior art, aiming at the technical problems of large-diameter pressure pipelines with a large diameter-thickness ratio and strong destructive effects under high internal and external pressures, a systematic method for the structural design of large-diameter pressure pipelines is urgently needed. The present invention provides a T-shaped stiffening ring steel cylinder concrete pipe and a design method thereof.

[0005] According to the first aspect of the present invention, there is provided a T-shaped stiffening ring steel cylinder concrete pipe, as Figure 1 shown, the pipe body part from the outside to the inside is successively an outer steel cylinder, a concrete layer, and an inner steel cylinder; it also includes at least two T-shaped stiffening rings fixed on the surface of the inner steel cylinder, extending along the circumferential direction of the pipeline. The T-shaped stiffening ring includes a head with a wider cross-section and an extension part with a narrower cross-section perpendicularly connected to the head. The bottom surface of the head with a wider cross-section of the T-shaped stiffening ring is vertically fixed on the surface of the inner steel cylinder, and a fixed axial spacing is set between the at least two T-shaped stiffening rings;

[0006] The concrete layer is densely filled between the inner steel cylinder, the T-shaped stiffening ring, and the outer steel cylinder, and is used to provide additional compressive capacity and durability; wherein, the minimum thickness of the filled concrete layer is greater than the vertical height from the bottom surface of the head of the T-shaped stiffening ring to the bottom surface of the end of the extension part, so as to disconnect the connection between the inner steel cylinder and the outer steel cylinder;

[0007] The vertical height h from the end of the extension part of the T-shaped stiffening ring (2) to the bottom surface of the head is:

[0008] ,

[0009] Wherein, d is the bottom width of the head of the T-shaped stiffening ring (2), h is the vertical height from the end of the extension part to the bottom surface of the head, t1 is the width at the connection position between the extension part and the head, t2 is the bottom width of the end of the extension part, t3 is the vertical distance between the connection position of the extension part and the head and the bottom surface of the head, t4 is the height of the outer sides of the left and right outer edges of the head, d T is the fixed axial pitch of the T-shaped stiffening ring (2), and t is the equivalent thickness of the pipe wall;

[0010] The T-shaped stiffening ring steel cylinder concrete pipe is designed with a thick inner steel cylinder and a thin outer steel cylinder.

[0011] Preferably, the width t1 at the connection position between the extension part and the head is equal to the vertical distance t3 between the connection position of the extension part and the head and the bottom surface of the head, and the bottom width t2 of the end of the extension part is equal to the height t4 of the outer sides of the left and right outer edges of the head; the bottom width d of the head of the T-shaped stiffening ring is greater than or equal to the vertical height h from the end of the extension part to the bottom surface of the head;

[0012] Preferably, the width t1 at the connection position between the extension part and the head of the T-shaped stiffening ring is 11 - 13 mm, the bottom width t2 of the end of the extension part is 5.5 - 6.5 mm, the vertical distance t3 between the connection position of the extension part and the head and the bottom surface of the head is 11 - 13 mm, and the height t4 of the outer sides of the left and right outer edges of the head is 5.5 - 6.5 mm. <>

[0013] Preferably, the inner diameter of the pipe cylinder of the T-shaped stiffening ring steel cylinder concrete pipe is D, and its value range is 1500 - 4600 mm.

[0014] Preferably, the equivalent thickness of the pipe wall of the T-shaped stiffening ring steel cylinder concrete pipe is t, and the thickness of the inner steel cylinder is 45% - 55% of t; the thickness of the outer steel cylinder is 18% - 22% of t.

[0015] \>Preferably, the fixed axial pitch of the T-shaped stiffening ring is d T , and its value range is 230 - 270 mm.

[0016] Preferably, the T-shaped stiffening ring is welded on the surface of the inner steel cylinder by full welding.

[0017] Preferably, the surface of the outer steel cylinder is provided with U-shaped corrugations.

[0018] According to the second aspect of the present invention, a design method for a T-shaped stiffening ring steel cylinder concrete pipe is provided, including the following steps:

[0019] Step 1: Calculate the equivalent thickness of the pipe wall under the internal pressure condition;

[0020] Step 2: Design the radial distribution form of the steel.

[0021] Step 3: Determine the filling thickness of the concrete between the inner and outer steel cylinders.

[0022] Step 4: Conduct strength checking and optimization design on the structure.

[0023] Furthermore, the specific content of Step 1 is as follows:

[0024] Establish a uniform tube structure model of the T-shaped stiffening ring steel tube concrete pipe. As Figures 2 - 4 shown, the inner diameter of the tube is D, and the equivalent thickness of the tube wall is t. Analyze the circumferential average tensile stress of the tube under the action of the internal pressure p; Take a dx micro-segment of the tube, cut it along the diameter to expose the cross-section of the tube wall, and list the static equilibrium equation along the normal direction of the tube wall:

[0025] .

[0026] It can be calculated that the circumferential average tensile stress is proportional to the internal pressure p, where the proportional coefficient is the diameter-thickness ratio D / 2t,

[0027] .

[0028] According to the yield stress of the selected steel material, select a safety factor n, and make the circumferential average tensile stress equal to the allowable stress of the material. The allowable stress is the ratio of the yield stress to the safety factor:

[0029] .

[0030] Calculate the equivalent thickness t of the tube wall under the internal pressure condition:

[0031] .

[0032] Preferably, the value range of the safety factor n is 1.8 - 2.2.

[0033] Preferably, the internal pressure p of the tube is 0.6 - 1.2 MPa.

[0034] Preferably, the selected steel material is Q235B, Q355B or Q420B steel, and the corresponding yield stress is 235 MPa, 355 MPa or 420 MPa.

[0035] The design of the radial distribution form of the steel in Step 2 includes:

[0036] According to the full stress criterion, under the internal pressure condition, the circumferential tensile stress in the uniform tube structure model varies with the tube radius and its distribution in the thickness direction is as follows:

[0037] .

[0038] It can be obtained that the circumferential tensile stress is the largest at the inner wall of the tube and the smallest at the outer wall of the tube, and decreases non-linearly from the inside to the outside; to enhance the ability of the T-shaped stiffening ring steel cylinder concrete pipe structure to resist internal pressure, the tensile material is arranged on the inner side of the pipe wall;

[0039] Under the external pressure condition, for the uniform tube structure model, take a dx micro-segment of the tube and cut it along the diameter direction, which can be simplified to a semi-circular curved beam bending model under the action of external pressure F, internal force of the pipe wall constraint and foundation support. The maximum bending stress of the model decreases in a square multiple with the increase of the total thickness t total of the tube wall. To enhance the ability of the T-shaped stiffening ring steel cylinder concrete pipe structure to resist external pressure, increase the wall thickness of the T-shaped stiffening ring steel cylinder concrete pipe, and arrange the tensile and compressive materials on the inner and outer sides of the pipe wall,

[0040] ;

[0041] Among them, is the maximum bending stress of the semi-circular curved beam bending model, F is the external pressure, D is the inner diameter of the tube, and t total is the total thickness of the tube wall.

[0042] In the third step, determining the filling thickness of the concrete between the inner and outer steel cylinders includes: the equivalent wall thickness t of the pipe wall, the total thickness t total -t of the concrete, and the average strength limit of the steel and concrete materials is:

[0043] ,

[0044] ,

[0045] Among them, is the yield limit of the selected steel, is the tensile strength of the selected concrete. Let the average strength limit of the steel and concrete materials be equal to the maximum bending stress of the uniform tube structure model, and the total thickness of the concrete is obtained as t total -t.

[0046] The strength check and optimization design of the structure in Step 4 include: determining the influence of the spacing and size of the T-shaped stiffening ring and the thickness of the concrete layer on the structural strength, establishing a model of the steel cylinder concrete pipe with T-shaped stiffening rings, checking the strength of the designed steel cylinder concrete pipe structure with T-shaped stiffening rings under internal and external pressure conditions, and optimizing the design of the structure of the steel cylinder concrete pipe with T-shaped stiffening rings.

[0047] Technical effects:

[0048] The steel cylinder concrete pipe with T-shaped stiffening rings and its design method of the present invention provide a systematic method for the structural design of large-diameter pressure pipelines. First, by analyzing the circumferential tensile stress of the pipe wall under internal pressure conditions, the equivalent thickness of the pipe wall is calculated, and the steel consumption satisfying the internal pressure conditions is determined; furthermore, the distribution laws of the circumferential tensile stress generated by internal pressure and the cross-sectional internal bending stress generated by external pressure are analyzed, and the structural form of the steel cylinder concrete pipe is determined as an internal steel cylinder, an external steel cylinder, a T-shaped stiffening ring is provided on the outer side of the internal steel cylinder, and concrete is filled between the internal and external steel cylinders. Pipelines with a diameter of 1.5 - 4.6 meters are designed using this method.

[0049] Through the structural form of a thick-walled internal steel cylinder, T-shaped stiffening rings, and a thin-walled external steel cylinder, the steel consumption gradually decreases from the inside to the outside, giving full play to the tensile performance of the steel and enhancing the internal pressure resistance of the pipeline. Sufficient thickness of concrete is filled between the internal and external steel cylinders to give full play to the compressive performance of the concrete and enhance the external pressure resistance of the pipeline. The sandwich structure of the external steel cylinder, concrete, and internal steel cylinder is designed, and the concrete is used to isolate the internal and external steel cylinders, cutting off the electrochemical circuit between the liquid inside the pipe and the external soil, and blocking the electrochemical corrosion of the steel cylinder. Through the present invention, the design of "the steel cylinder bears internal pressure and the concrete bears external pressure" for large-diameter-thickness-ratio pressure pipelines is realized, solving the technical problems of large diameter-thickness ratio and strong destructiveness under high internal and external pressures of large-diameter pressure pipelines, ensuring the bearing capacity of the pressure pipeline, reducing costs and improving safety. Description of the drawings

[0050] Figure 1 It is the overall structural design drawing of the steel cylinder concrete pipe with T-shaped stiffening rings of the present invention along the radial direction.

[0051] Figure 2 It is the uniform pipe cylinder model drawing for the structural modeling of the steel cylinder concrete pipe with T-shaped stiffening rings of the present invention.

[0052] Figure 3 It is the cross-sectional force diagram of the pipe wall for the structural modeling of the steel cylinder concrete pipe with T-shaped stiffening rings of the present invention.

[0053] Figure 4 It is the distribution diagram of the circumferential tensile stress along the thickness direction of the uniform pipe cylinder model of the steel cylinder concrete pipe with T-shaped stiffening rings of the present invention under internal pressure conditions.

[0054] Figure 5It is a schematic diagram of the flexural deformation of a curved beam of the uniform pipe barrel model of the T-shaped stiffening ring steel cylinder concrete pipe of the present invention under the external pressure condition.

[0055] Figure 6 It is a Mises stress nephogram of the inner steel cylinder of the T-shaped stiffening ring steel cylinder concrete pipe of the present invention under the internal pressure condition.

[0056] Figure 7 It is a Mises stress nephogram of the inner steel cylinder of the T-shaped stiffening ring steel cylinder concrete pipe of the present invention under the external pressure condition.

[0057] Figure 8 It is a Mises stress nephogram of the T-shaped stiffening ring of the T-shaped stiffening ring steel cylinder concrete pipe of the present invention under the internal pressure condition.

[0058] Figure 9 It is a Mises stress nephogram of the T-shaped stiffening ring of the T-shaped stiffening ring steel cylinder concrete pipe of the present invention under the external pressure condition.

[0059] Figure 10 It is a Mises stress nephogram of the outer steel cylinder of the T-shaped stiffening ring steel cylinder concrete pipe of the present invention under the internal pressure condition.

[0060] Figure 11 It is a Mises stress nephogram of the outer steel cylinder of the T-shaped stiffening ring steel cylinder concrete pipe of the present invention under the external pressure condition.

[0061] Figure 12 It is a tensile stress nephogram of the concrete layer of the T-shaped stiffening ring steel cylinder concrete pipe of the present invention under the internal pressure condition.

[0062] Figure 13 It is a tensile stress nephogram of the concrete layer of the T-shaped stiffening ring steel cylinder concrete pipe of the present invention under the external pressure condition. Detailed implementation manners

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts shall fall within the scope of protection of the present disclosure.

[0064] In some embodiments, in the T-shaped stiffening ring steel cylinder concrete pipe, the pipe body part from the outside to the inside is successively an outer steel cylinder 3, a concrete layer 4, and an inner steel cylinder 1; it further includes at least two T-shaped stiffening rings 2 fixed on the surface of the inner steel cylinder, extending along the circumferential direction of the pipeline. The T-shaped stiffening ring 2 includes a head with a relatively wide cross-section and an extension part with a relatively narrow cross-section perpendicularly connected to the head. The bottom surface of the head with a relatively wide cross-section of the T-shaped stiffening ring 2 is perpendicularly fixed on the surface of the inner steel cylinder 1, and a fixed axial spacing is set between the at least two T-shaped stiffening rings 2.

[0065] The concrete layer 4 is densely filled between the inner steel cylinder 1, the T-shaped stiffening ring 2, and the outer steel cylinder 3, for providing additional compressive capacity and durability; wherein, the minimum thickness of the filled concrete layer 4 is greater than the vertical height from the bottom surface of the head of the T-shaped stiffening ring 2 to the bottom surface of the end of the extension part, so as to disconnect the connection between the inner and outer steel cylinders.

[0066] Preferably, the width of the bottom surface of the head of the T-shaped stiffening ring is d, the vertical height from the end of the extension part to the bottom surface of the head is h, the width of the bottom surface of the end of the extension part is t2, the width of the position where the extension part is connected to the head is t1, the vertical distance from the position where the extension part is connected to the head to the bottom surface of the head is t3, and the height of the outer side edges of the left and right outer edges of the head is t4. Among them, the lengths of t1 and t3 are equal, and the lengths of t2 and t4 are equal.

[0067] Preferably, the width d of the bottom surface of the head of the T-shaped stiffening ring is greater than or equal to the vertical height h from the end of the extension part to the bottom surface of the head.

[0068] Preferably, the length of the width d of the bottom surface of the head of the T-shaped stiffening ring is 1 to 2 times the length of the vertical height h from the end of the extension part to the bottom surface of the head.

[0069] Preferably, the length of the width t1 at the position where the extension part is connected to the head and the length of the vertical distance t3 from the position where the extension part is connected to the head to the bottom surface of the head are 2 times the lengths of the width t2 of the bottom surface of the end of the extension part and the height t4 of the outer side edges of the left and right outer edges of the head.

[0070] Preferably, the width t2 of the bottom surface of the end of the extension part of the T-shaped stiffening ring is 5.5 - 6.5 mm, the width t1 at the position where the extension part is connected to the head is 11 - 13 mm, the vertical distance t3 from the position where the extension part is connected to the head to the bottom surface of the head is 11 - 13 mm, and the height t4 of the outer side edges of the left and right outer edges of the head is 5.5 - 6.5 mm.

[0071] Preferably, the T-shaped stiffening ring is welded on the surface of the inner steel cylinder by full welding.

[0072] Preferably, the surface of the outer steel cylinder is provided with U-shaped corrugations.

[0073] Preferably, the inner diameter of the tube barrel of the T-shaped stiffening ring steel cylinder concrete pipe is D, and its value range is 1500~4600mm.

[0074] Preferably, the equivalent thickness of the tube wall of the T-shaped stiffening ring steel cylinder concrete pipe is t, and the thickness of the inner steel cylinder is 45%~55% of t; the thickness of the outer steel cylinder is 18%~22% of t.

[0075] Preferably, the axial fixed spacing of the T-shaped stiffening ring is d T , and its value range is 230~270mm.

[0076] In some embodiments, the design method of the T-shaped stiffening ring steel cylinder concrete pipe includes the following steps:

[0077] Step 1: Calculate the equivalent thickness of the tube wall under the internal pressure condition by using a uniform tube barrel model;

[0078] Establish a uniform tube barrel structure model of the T-shaped stiffening ring steel cylinder concrete pipe as Figures 2 - 4 shown, the inner diameter of the tube barrel is D, and the equivalent thickness of the tube wall is t. Analyze the circumferential average tensile stress of the tube barrel under the action of the internal pressure p ; Take a dx micro-segment of the tube barrel, cut it along the diameter direction to expose the cross-section of the tube wall, and list the static equilibrium equation along the normal direction of the tube wall as shown in formula (1), and the calculated circumferential average tensile stress is proportional to the internal pressure p as shown in formula (2), where the proportional coefficient is the diameter-thickness ratio D / 2t. According to the yield stress of the selected steel material, select a safety factor n, and make the circumferential average tensile stress equal to the allowable stress of the material as shown in formula (3), and the allowable stress is the ratio of the yield stress to the safety factor. Calculate the equivalent thickness t of the tube wall under the internal pressure condition as shown in formula (4).

[0079] In this embodiment, the inner diameter D of the tube barrel is 1500~4600mm, the internal pressure p is 0.6~1.2MPa. According to the yield stress of the selected Q420b steel material being 420MPa, the safety factor n is 2.0. The equivalent thickness t is calculated by formula (4) as shown in Table 1. When D is 1500mm, t is 2.2~4.3mm; when D is 3000mm, t is 4.3~8.6mm; when D is 4600mm, t is 6.6~13.2mm.

[0080] (1)

[0081] (2)

[0082] (3)

[0083] (4)

[0084] Step 2: Design the radial distribution form of the steel according to the full stress criterion.

[0085] Under the internal pressure condition, the circumferential tensile stress in the uniform tube structure model varies with the tube radius and its distribution in the thickness direction is shown in formula (5). It can be calculated that its distribution law is as Figure 4 shown. The circumferential tensile stress is the largest at the inner wall of the tube and the smallest at the outer wall of the tube, and decreases non-linearly from the inside to the outside. Therefore, to enhance the ability of the T-shaped stiffening ring steel cylinder concrete pipe structure to resist internal pressure, the tensile material is arranged on the inner side of the pipe wall;

[0086] (5)

[0087] Under the external pressure condition, establish the curved beam bending model of the external pressure condition. For the uniform tube structure model, take a dx micro-segment of the tube and cut it along the diameter direction, as Figure 5 shown. It can be simplified to a semi-circular curved beam bending model under the combined action of the external pressure F / 2, the pipe wall binding forces X1 and X2, and the foundation. From formula (6), the maximum bending stress of the model can be obtained, which decreases in a square multiple with the increase of the total thickness t total of the tube wall. Therefore, to enhance the ability of the T-shaped stiffening ring steel cylinder concrete pipe structure to resist external pressure, increase the wall thickness of the T-shaped stiffening ring steel cylinder concrete pipe, and arrange the tensile and compressive materials on the inner and outer sides of the pipe wall. Considering the internal and external pressure conditions of the T-shaped stiffening ring steel cylinder concrete pipe comprehensively, design the T-shaped stiffening ring steel cylinder concrete pipe as a thick-walled inner steel cylinder and a thin-walled outer steel cylinder.

[0088] (6)

[0089] According to the full stress criterion, the radial distribution of the steel is designed as the structure shown in Figure 1 : the thickness of the inner steel cylinder is 45%-55% of t, the thickness of the outer steel cylinder is 18%-22% of t, and the T-shaped stiffening rings are fixed at an axial interval of d T, and its value range is 230 - 270 mm. The bottom width of the head of the T-shaped stiffening ring is d, the vertical height from the end of the extension part to the bottom surface of the head is h, the bottom width of the end of the extension part is t2 which is 5.5 - 6.5 mm, the width at the position where the extension part is connected to the head is t1 which is 11 - 13 mm, the vertical distance between the position where the extension part is connected to the head and the bottom surface of the head is t3 which is 11 - 13 mm, the height of the outer side edges of the left and right outer edges of the head is t4 which is 5.5 - 6.5 mm, and the length of the bottom width d of the head of the T-shaped stiffening ring is 1 - 2 times the length of h. The vertical height h from the end of the extension part of the T-shaped stiffening ring to the bottom surface of the head can be calculated by formula (7).

[0090] In this embodiment, the thickness of the inner steel cylinder is taken as 50% of t, the thickness of the outer steel cylinder is taken as 20% of t, and the axial fixed spacing of the T-shaped stiffening ring is d T Take 250 mm, t1 is taken as 12 mm, t2 is taken as 6 mm, t3 is taken as 12 mm, t4 is taken as 6 mm, and the vertical height h from the end of the extension part of the T-shaped stiffening ring to the bottom surface of the head is:

[0091] (7)

[0092] Wherein, d is the bottom width of the head of the T-shaped stiffening ring, h is the vertical height from the end of the extension part to the bottom surface of the head, t1 is the width at the position where the extension part is connected to the head, t2 is the bottom width of the end of the extension part, t3 is the vertical distance between the position where the extension part is connected to the head and the bottom surface of the head, t4 is the height of the outer side edges of the left and right outer edges of the head, d T is the axial fixed spacing of the T-shaped stiffening ring, and t is the equivalent thickness of the pipe wall.

[0093] Step three: Determine the filling thickness of the concrete between the inner and outer steel cylinders.

[0094] The T-shaped stiffening ring needs to be in contact with the inner steel cylinder to enhance the internal pressure resistance of the structure. If it is in contact with the outer steel cylinder at the same time, it will hinder the pouring of concrete and the embedding of monitoring elements such as optical fibers, and will also cause the inner and outer steel cylinders to be connected to form a primary battery circuit between the liquid in the pipe and the external soil, causing electrochemical corrosion of the steel cylinder. Therefore, the concrete layer should have sufficient thickness to resist external pressure, and the thickness of the concrete layer should be greater than the height of the T-shaped stiffening ring to disconnect the connection between the inner and outer steel cylinders.

[0095] Using the homogenization method, the average strength limit of the steel and concrete materials with an equivalent thickness of t for steel and a total thickness of t total -t can be calculated. As shown in formula (8),

[0096] (8)

[0097] Wherein, is the yield limit of the selected steel, is the tensile strength of the selected concrete, the external pressure is F, and let the average strength limit of the steel and concrete materials as in formula (8) be equal to the maximum bending stress of the described uniform tube structure model as in formula (6), the total thickness of the concrete is obtained as t total -t, where t total can be calculated by formula (9),

[0098] (9)

[0099] In this embodiment, the yield limit of the selected steel is 420 MPa, and the tensile strength of the selected concrete is 2 MPa. The selected external pressure F is the failure load of the Class III reinforced concrete pipe: when D is 1500 mm, F is 203 kN / m; when D is 3000 mm, F is 390 kN / m; when D is 4600 mm, F is 560 kN / m. The thickness of the concrete obtained by calculating through formula (9) is t total -t as shown in Table 1. When D is 1500 mm, the thickness of the concrete layer is 44.0 - 75.0 mm; when D is 3000 mm, the thickness of the concrete layer is 83.0 - 147.0 mm; when D is 4600 mm, the thickness of the concrete layer is 119.0 - 213.0 mm.

[0100] In some embodiments, micro-expansive concrete is selected to generate pre-pressure in the concrete between the inner and outer steel cylinders, which can improve the tensile capacity of the concrete.

[0101] This embodiment lists some design dimensions of the T-shaped stiffening ring steel cylinder concrete pipe structure, as shown in Table 1.

[0102] Table 1

[0103]

[0104] Step Four: Use the finite element method to conduct strength checking and optimization design on the structure.

[0105] Conducting strength checking and optimization design on the structure includes: determining the influence of the spacing and size of the described T-shaped stiffening ring and the thickness of the concrete layer on the structure strength, establishing a model of the T-shaped stiffening ring steel cylinder concrete pipe, checking the strength of the designed T-shaped stiffening ring steel cylinder concrete pipe structure under internal and external pressure conditions, and conducting optimization design on the structure of the T-shaped stiffening ring steel cylinder concrete pipe.

[0106] Based on the above method, the following embodiments are given.

[0107] In this embodiment, D is 3000 mm, p is 1.2 MPa, the external pressure F is 390 kN / m, and the yield stress of the Q420B steel material is selected as 420 MPa, and the safety factor n is selected as 2.0. It is calculated that the inner cylinder thickness is 5 mm, the outer cylinder thickness is 2 mm, the concrete layer thickness is 120 mm, and the parameters of the T-shaped stiffening ring are d = 40 mm, h = 40 mm, t1 = t3 = 12 mm, t2 = t4 = 6 mm, and the axial distribution pitch is 250 mm. Both steel and concrete materials adopt linear elastic models, and the material parameters are shown in Table 2.

[0108] Table 2

[0109]

[0110] According to the calculation results of the detailed finite element model, by adjusting the dimensions of the inner steel cylinder, outer steel cylinder, T-shaped stiffening ring and concrete layer, and then performing finite element simulation, the designed structure can save materials as much as possible under the condition of meeting the strength requirements, achieving the purpose of optimal design.

[0111] Figure 6 is the Mises stress nephogram of the inner steel cylinder under the internal pressure condition. The results show that the Mises stress distribution of the inner steel cylinder is relatively uniform, and the average value is about 61.8 MPa, which is less than the yield limit of Q420B steel, meeting the strength condition;

[0112] Figure 7 is the Mises stress nephogram of the inner steel cylinder under the external pressure condition. The results show that the Mises stress of the inner steel cylinder generates stress concentration at the foundation support, and the value at the dangerous section is about 95 MPa, which is less than the yield limit of Q420B steel, meeting the strength condition;

[0113] Figure 8 is the Mises stress nephogram of the T-shaped stiffening ring under the internal pressure condition. The results show that the Mises stress distribution of the T-shaped stiffening ring is relatively uniform, and the average value is about 61 MPa, which is less than the yield limit of Q420B steel, meeting the strength condition;

[0114] Figure 9 is the Mises stress nephogram of the T-shaped stiffening ring under the external pressure condition. The results show that the Mises stress of the T-shaped stiffening ring generates stress concentration at the foundation support, and the value at the dangerous section is about 70 MPa, which is less than the yield limit of Q420B steel, meeting the strength condition;

[0115] Figure 10 is the Mises stress nephogram of the outer steel cylinder under the internal pressure condition. The results show that the Mises stress distribution of the outer steel cylinder is relatively uniform, and the average value is about 55.5 MPa, which is less than the yield limit of Q42OSB steel, meeting the strength condition;

[0116] Figure 11 It is the Mises stress nephogram of the outer steel cylinder under external pressure condition. The result shows that the Mises stress of the outer steel cylinder generates stress concentration at the foundation support, about 130 MPa, which is less than the yield limit of Q420B steel, meeting the strength condition;

[0117] Figure 12 It is the tensile stress nephogram of the concrete layer under internal pressure condition. The result shows that the maximum tensile stress of the concrete layer is about 10 MPa, exceeding the tensile strength of the concrete, and the concrete will undergo fracture failure. Through equivalent calculation, the load-bearing of the concrete layer is proportionally loaded onto the inner steel cylinder, outer steel cylinder and T-shaped stiffening ring. The Mises stress of the above structure is still less than the yield limit of Q420B steel, and the designed structure meets the strength condition;

[0118] Figure 13 It is the tensile stress nephogram of the concrete layer under external pressure condition. The result shows that the tensile stress of the concrete layer generates stress concentration at the foundation support, about 28 MPa at the dangerous section, exceeding the tensile strength of the concrete, and the concrete will have local cracks. The tensile stress of the concrete in most areas is less than the tensile strength of the concrete, and the concrete layer is safe.

[0119] The above are only the preferred examples of the present invention and are not used to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made to the present invention shall be included within the protection scope of the present invention.

Claims

1. T-shaped stiffening ring steel cylinder concrete pipe, characterized in that, The pipe body part from outside to inside is successively an outer steel cylinder (3), a concrete layer (4), and an inner steel cylinder (1); it also includes at least two T-shaped stiffening rings (2) fixed on the surface of the inner steel cylinder (1), extending along the circumferential direction of the pipe. The T-shaped stiffening ring (2) includes a head with a wider cross-section and an extension part with a narrower cross-section perpendicularly connected to the head. The bottom surface of the head with a wider cross-section of the T-shaped stiffening ring (2) is perpendicularly fixed on the surface of the inner steel cylinder (1), and a fixed axial spacing is set between the at least two T-shaped stiffening rings (2). The concrete layer (4) is densely filled between the inner steel cylinder (1), the T-shaped stiffening ring (2), and the outer steel cylinder (3). The minimum filling thickness of the concrete layer (4) is greater than the vertical height from the bottom surface of the head of the T-shaped stiffening ring (2) to the bottom surface of the end of the extension part, so as to disconnect the connection between the inner steel cylinder (1) and the outer steel cylinder (3). The vertical height h from the end of the extension part of the T-shaped stiffening ring (2) to the bottom surface of the head is: ， Among them, d is the bottom surface width of the head of the T-shaped stiffening ring (2), h is the vertical height from the end of the extension part to the bottom surface of the head, t1 is the width at the connection position between the extension part and the head, t2 is the bottom surface width of the end of the extension part, t3 is the vertical distance between the connection position of the extension part and the head and the bottom surface of the head, t4 is the height of the outer sides of the left and right outer edges of the head, d T is the fixed axial pitch of the T-shaped stiffening ring (2), and t is the equivalent thickness of the pipe wall; The T-shaped stiffening ring steel cylinder concrete pipe is designed with a thick-walled inner steel cylinder and a thin-walled outer steel cylinder.

2. The T-shaped stiffening ring steel cylinder concrete pipe according to claim 1, wherein The width t1 at the connection position between the extension part and the head is equal to the vertical distance t3 between the connection position between the extension part and the head and the bottom surface of the head. The width t2 of the bottom surface of the end of the extension part is equal to the height t4 of the outer side edges of the left and right outer edges of the head; the bottom surface width d of the head of the T-shaped stiffening ring (2) is greater than or equal to the vertical height h from the end of the extension part to the bottom surface of the head. The width t1 at the connection position between the extension part and the head is 11 - 13 mm, the width t2 of the bottom surface of the end of the extension part is 5.5 - 6.5 mm, the vertical distance t3 between the connection position between the extension part and the head and the bottom surface of the head is 11 - 13 mm, and the height t4 of the outer side edges of the left and right outer edges of the head is 5.5 - 6.5 mm. The value range of the inner diameter D of the pipe barrel of the T-shaped stiffening ring steel cylinder concrete pipe is 1500 - 4600 mm. The thickness of the inner steel cylinder is 45% - 55% of the equivalent wall thickness t of the pipe wall, and the thickness of the outer steel cylinder is 18% - 22% of the equivalent wall thickness t of the pipe wall; the T-shaped stiffening ring has a fixed axial spacing d T with a value range of 230 - 270 mm.

3. The T-shaped stiffening ring steel cylinder concrete pipe according to claim 2, characterized in that The length of the bottom surface width d of the head of the T-shaped stiffening ring (2) is 1 - 2 times the length of the vertical height h from the end of the extension part to the bottom surface of the head; the lengths of the width t1 at the connection position between the extension part and the head and the vertical distance t3 between the connection position between the extension part and the head and the bottom surface of the head are 2 times the lengths of the width t2 of the bottom surface of the end of the extension part and the height t4 of the outer side edges of the left and right outer edges of the head.

4. The T-shaped stiffening ring steel cylinder concrete pipe according to claim 1, wherein, The T-shaped stiffening ring (2) is welded on the surface of the inner steel cylinder (1) by full welding; the surface of the outer steel cylinder (3) is provided with U-shaped corrugations.

5. The design method of the T-shaped stiffening ring steel cylinder concrete pipe according to any one of claims 1 to 4, characterized in that, It includes the following steps: Step 1: Calculate the equivalent thickness of the pipe wall under the internal pressure condition. Step 2: Design the radial distribution form of the steel. Step 3: Determine the filling thickness of the concrete between the inner and outer steel cylinders. Step 4: Conduct strength checking and optimization design on the structure.

6. The design method of the T-shaped stiffening ring steel cylinder concrete pipe according to claim 5, characterized in that, The calculation of the equivalent thickness of the pipe wall in Step 1 under the internal pressure condition includes: Establish a uniform tube structure model of the T-shaped stiffening ring steel tube concrete pipe. The inner diameter of the tube is D, and the equivalent thickness of the tube wall is t. Analyze the average circumferential tensile stress of the tube under the action of internal pressure p ; Take a dx micro-segment of the tube, cut it along the diameter direction to expose the cross-section of the tube wall, and list the static equilibrium equation along the normal direction of the tube wall: ； The circumferential average tensile stress can be calculated is proportional to the internal pressure p, where the proportionality coefficient is the diameter-thickness ratio D / 2t ； According to the yield stress of the selected steel material , a safety factor n is selected, and the circumferential average tensile stress is made equal to the allowable stress of the material, and the allowable stress is the ratio of the yield stress to the safety factor n: ； Calculate the equivalent thickness t of the pipe wall under the internal pressure condition: ， Wherein, p is the internal pressure of the tube; D is the inner diameter of the tube; n is the safety factor; is the yield stress.

7. The design method of the T-shaped stiffening ring steel cylinder concrete pipe according to claim 6, characterized in that, The value range of the safety factor n is 1.8 to 2.2, and the internal pressure p of the tube is 0.6 to 1.2 MPa; the selected steel material is Q235B, Q355B or Q420B steel, and the corresponding yield stress is 235 MPa, 355 MPa or 420 MPa.

8. The design method of the T-shaped stiffening ring steel cylinder concrete pipe according to claim 5, characterized in that, Step 2 is specifically: According to the full stress criterion, under the internal pressure condition, the distribution of the circumferential tensile stress in the thickness direction of the uniform tube structure model varies with the tube radius as follows: ， D is the inner diameter of the pipe barrel, t is the equivalent thickness of the pipe wall, and the circumferential tensile stress is the largest at the inner wall of the pipe barrel and the smallest at the outer wall of the pipe barrel, and decreases non-linearly from the inside to the outside; to enhance the ability of the T-shaped stiffening ring steel cylinder concrete pipe structure to resist internal pressure, the tensile material is arranged on the inner side of the pipe wall; Under the external pressure condition, for the uniform tube structure model, a dx micro-segment of the tube is taken and cut along the diameter direction, and it is simplified into a semi-circular curved beam bending model under the combined action of the external pressure F, the internal constraint force of the tube wall, and the foundation support. The maximum bending stress of the semi-circular curved beam bending model decreases in a square multiple with the increase of the total thickness t of the tube wall total To enhance the ability of the T-shaped stiffening ring steel tube concrete pipe structure to resist external pressure, the wall thickness of the T-shaped stiffening ring steel tube concrete pipe is increased, and the tensile and compressive materials are arranged on the inner and outer sides of the tube wall; ， Among them, is the maximum bending stress of the semi-circular curved beam bending model, F is the external pressure, D is the inner diameter of the tube, and t total is the total thickness of the tube wall.

9. The design method of the T-shaped stiffening ring steel cylinder concrete pipe according to claim 6, characterized in that, The determination of the filling thickness of the concrete between the inner and outer steel cylinders in the third step includes: the equivalent wall thickness t, the concrete thickness t total -t, and the average strength limit of the steel and concrete materials is as follows: ， ， Among them, is the yield limit of the selected steel, is the tensile strength of the selected concrete. Let the average strength limit of the steel and concrete materials be equal to the maximum bending stress of the said uniform tube structure model, and the total thickness of the concrete is obtained as t total -t.

10. The design method of the T-shaped stiffening ring steel cylinder concrete pipe according to claim 5, characterized in that, The fourth step of performing strength check and optimization design on the structure includes: determining the influence of the spacing and size of the T-shaped stiffening ring and the thickness of the concrete layer on the structural strength, establishing a model of the steel cylinder concrete pipe with T-shaped stiffening ring, checking the strength of the designed steel cylinder concrete pipe structure with T-shaped stiffening ring under internal and external pressure conditions, and performing optimization design on the structure of the steel cylinder concrete pipe with T-shaped stiffening ring.

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