Round bamboo composite profile type selection and construction method

Abstract

The invention provides a model selection and construction method of round bamboo composite profiles, relates to the technical field of building profile construction, and provides a novel round bamboo connection method based on the characteristics of round bamboo structures and the principle of fully transferring rift grain tensile resistance of round bamboos, quantifies the component specifications of round bamboo connection devices, standardizes round bamboo connection, and improves the construction efficiency. A reliable way is provided for external connection of the round bamboos, the round bamboos can be easily combined into columns, beams, wallboards, beam plates and other building profiles for assembly construction, wide application of the round bamboo materials in the building industry is promoted, and the round bamboo connecting structure has wide prospects.

Description

Technical Field

[0001] The invention relates to the technical field of building profile construction, in particular to a round bamboo composite profile selection and construction method. Background Art

[0002] my country is rich in bamboo resources, and the current development of bamboo-based plastics, such as the use of bamboo in industrial applications, has achieved some success. However, due to the relatively high cost of bamboo products and the natural hollowness of bamboo, its application is greatly limited.

[0003] The construction market has a huge demand for materials. Many researchers have been exploring the application of bamboo in building materials, proposing applications such as replacing steel and concrete with bamboo and conducting extensive research. Research on moso bamboo as a building material is a major focus. Moso bamboo is the primary bamboo species in my country, accounting for 70% of the country's bamboo resources. It only takes 4-6 years to mature, boasts high yields, a wide distribution, and is inexpensive. Its excellent mechanical properties make it a valuable green, low-carbon building material.

[0004] A search revealed patents CN217537317U, which discloses a "bamboo frame structure," CN210767268U, a "beam-column connection structure for a raw bamboo skeleton," CN220953902U, a "raw bamboo structure rod connection structure," and CN210134535U, a "round bamboo butt-joint connection structure." While these patents offer insights into using round bamboo profiles to form building frames, they are limited to specific circumstances and fail to quantitatively analyze the mechanical properties of the connection points between round bamboo beams and columns. They also fail to determine component selection methods based on this quantitative analysis, making it difficult to provide quantitative standards for round bamboo building design. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention quantitatively analyzes the components of the round bamboo connection device and determines the component selection method, which solves the problem of determining the mechanical parameters of the existing round bamboo profiles or round bamboo composite profile connection structures and provides a feasible reference standard for round bamboo building design.

[0006] The technical solution of the present invention is: a method for selecting and constructing round bamboo composite profiles, comprising the following steps:

[0007] S1. Select multiple round bamboos, cut them into the same length, remove the inner layers at the bamboo joints, and after material selection, obtain hollow round bamboos of basically uniform size and specifications, and obtain the parameters of the hollow round bamboos;

[0008] S2. Cut a steel bar of 200 mm to 500 mm in length, drill a threaded connection hole on the end face of one end of the steel bar for connection with an external bolt, and drill multiple screw holes along the radial direction of the steel bar at the other end of the steel bar to form an external connection rod;

[0009] S3, drilling a through hole in the bamboo wall corresponding to the screw hole at the end of the hollow round bamboo;

[0010] S4. Arrange at least one hollow round bamboo of the same length in a staggered manner into a plate or column shape according to the large and small ends, embed the external connecting rod into the end of the hollow round bamboo so that the end face of the external connecting rod close to the threaded connection hole is flush with the end face of the hollow round bamboo, use a double-headed screw to pass through the through hole and the screw hole in the bamboo wall and tighten them to form a spliced ​​round bamboo frame; cast an adhesive filler at the end of the hollow round bamboo to fix the external connecting rod.

[0011] As a preferred embodiment of the present invention, in step S1, the parameters include: the tensile strength along the grain of the bamboo material, the cross-sectional area of ​​the small end of the hollow round bamboo, and the tensile strength along the grain of the hollow round bamboo;

[0012] The calculation expression for the cross-sectional area of ​​the small end wall of the hollow round bamboo is:

[0013]

[0014] Where, d1 is the average outer diameter of the small end of the round bamboo, d2 is the average inner diameter of the small end of the round bamboo, and A yzb It is the cross-sectional area of ​​the bamboo wall at the small end of the round bamboo.

[0015] The calculation expression of the tensile stress along the grain of the small end of the hollow round bamboo is:

[0016]

[0017] Where, F cu is the tensile strength of hollow round bamboo along the grain, f cu It is the tensile strength of bamboo along the grain.

[0018] As a preferred embodiment of the present invention, in step S4, the number and type of double-headed screws are selected based on the tensile strength along the grain of the hollow round bamboo and the number of screw holes; the expression for selecting the double-headed screw diameter is:

[0019]

[0020] Where: d lg The minimum diameter of the twin-head screw to meet the strength requirements, f vlg is the shear stress strength of the screw, n v is the number of shear surfaces of the screw.

[0021] According to d lgvalue, select a general screw model close to or larger than this value, and record its diameter as d lgx .

[0022] As a preferred solution of the present invention, in step S2, the distance between any screw hole and the end of the external connecting rod is greater than or equal to the diameter of the external connecting rod, and the distance between any screw holes is greater than or equal to the diameter of the external connecting rod; there is an angle between the axes of the different screw holes, following the expression: ∠B=180° / n, where ∠B is the angle between adjacent screw holes, and n is the number of double-headed screws.

[0023] As a preferred embodiment of the present invention, in step S2, the size of the threaded connection hole and the corresponding external bolt model are selected according to the tensile strength along the grain of the hollow round bamboo. The expression for selecting the diameter of the external bolt is:

[0024]

[0025] Where: f tls is the tensile strength of the external bolt, d ls The minimum diameter of external bolts to meet strength requirements.

[0026] According to d ls The value is close to and larger than the general bolt model, whose diameter is d lsz .

[0027] As a preferred embodiment of the present invention, in step S2, the model of the external connecting rod is selected based on the tensile strength along the grain of the hollow round bamboo and the diameter of the external bolt (equivalent to the inner diameter of the threaded connection hole). The expression for selecting the diameter of the external connecting rod is:

[0028]

[0029] Among them: F tlkc f is the tensile strength of the screw hole end of the external connecting rod; tgj is the tensile strength of the external connecting rod; d gj The minimum diameter of the external connecting rod to meet the strength requirements; d lsz This is the final diameter of the external bolt, which is equivalent to the inner diameter of the screw hole.

[0030] Calculate d gj value, select a common steel bar model close to or larger than this value, and record its diameter as d gjx .

[0031] As a preferred solution of the present invention, step S4 further includes the steps of: verifying the tensile strength value of the external connecting rod 4 at the screw hole;

[0032] Calculate the cross-sectional area A of the external connecting rod at the screw lgk:

[0033]

[0034] Calculation: F tlgc =f tgj ×A lgc Value, such as F tlgc >F cu / 2, then the primary selected external connection steel bar model meets the requirements, recorded as d gjz Otherwise, select a larger outer diameter external connecting rod and substitute the diameter into d gjx , calculate F tlgc value, to meet F tlgc >F cu / 2 requirement, the external connecting rod model meets the requirement, recorded as d gjz .

[0035] Among them, f tgj A is the tensile strength of the external connecting rod; lgk It is the cross-sectional area of ​​the external connecting rod at the screw.

[0036] Preferably, in step S4, the method further comprises: bonding and wrapping a fiber band around the outer wall of the hollow round bamboo to form a fiber hoop.

[0037] Preferably, in step S4, the method further comprises: wrapping and bonding fiber materials to the periphery of the spliced ​​round bamboo frame to form a fiber winding layer; and filling adhesive fillers in gaps between the fiber winding layer, the spliced ​​round bamboo frame, and the hollow round bamboo.

[0038] Preferably, after step S4, concrete is poured around the fiber hoop and the fiber winding layer as a protective layer.

[0039] Preferably, the fiber hoop and the fiber winding layer can be made of one or more combinations of bamboo fiber, glass fiber, and carbon fiber.

[0040] Preferably, the bonding filler can be selected from one or more combinations of mortar and concrete.

[0041] The codes used in the above calculation formula express the following parameters:

[0042] d1 outer diameter of the small end of the round bamboo d2 inner diameter of the small end of the round bamboo A yzb Cross-sectional area of ​​bamboo wall at the small end of round bamboo;

[0043] F cu Tensile stress along the grain of round bamboo f cu Tensile strength of round bamboo along the grain;

[0044] N vlg Screw shear stress f vlg Screw shear strength n vis the number of shear surfaces of the screw;

[0045] d lgx The initial diameter d of the twin-head screw lgz Final diameter of the twin-head screw;

[0046] N clg Screw yield stress f clg Screw yield strength;

[0047] F tls Bolt tensile stress f tls Bolt tensile strength d ls is the bolt diameter d lsz Select the final diameter for the bolt;

[0048] F tlkc Tensile stress f at the screw hole end of the external connecting rod tgj is the tensile strength of the external connecting rod;

[0049] A lgk Cross-sectional area of ​​the connecting rod at the screw hole d gjx Connecting rod initial diameter d gjz Final diameter of connecting rod;

[0050] d lgk Connecting rod screw hole diameter.

[0051] Compared with the prior art, the advantages of the present invention are:

[0052] 1. Based on the structural characteristics of round bamboo and the principle of fully transmitting the tensile strength of round bamboo along the grain, the present invention proposes a new method for connecting round bamboo profiles.

[0053] 2. The round bamboo composite profile constructed in the present invention solves the technical problems of existing round bamboo profile extension and external connection, and can keep the tensile performance of the round bamboo profile unaffected.

[0054] 3. Based on the tensile stress of round bamboo profiles, the present invention proposes a calculation formula and selection method for determining the selection of double-headed screws, external bolts and external connecting rods of the connection device components, and proposes a reference table for component selection.

[0055] 4. This invention provides a reliable method for connecting round bamboo profiles to external surfaces, enabling their use in the assembly and connection of building beams, columns, and slabs. This ensures structural safety and offers advantages in earthquake resistance. This invention has broad prospects for promoting the widespread use of bamboo in the civil engineering and construction industries.

[0056] 5. The ends of the round bamboo composite profiles constructed in the present invention are designed with external connecting rods, which can be flexibly assembled and easily assembled on-site, saving construction time and on-site construction costs, and providing strong guarantees for civilized and green construction on-site.

[0057] The detailed structure of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a flow chart of the steps for selecting the stud screw, external bolts and external connecting rods of the present invention;

[0059] Figure 2 This is a cross-sectional view of a round bamboo composite profile constructed from a single hollow round bamboo according to the present invention;

[0060] Figure 3 The second cross-sectional view of the round bamboo composite profile constructed from a single hollow round bamboo of the present invention;

[0061] Figure 4 A cross-sectional view of a round bamboo composite profile constructed of multiple hollow round bamboos according to the present invention;

[0062] Figure 5 Schematic diagram of the measurement points of the outer diameter and inner diameter of the small end of the round bamboo of the present invention;

[0063] Figure 6 This is a schematic diagram of the force area of ​​the double-headed screw of the present invention;

[0064] Figure 7 This is a physical picture of the round bamboo composite profile of the present invention;

[0065] Figure 8 This is the second actual picture of the round bamboo composite profile of the present invention.

[0066] Names of components and corresponding serial numbers: 1. Hollow round bamboo; 2. Fiber winding layer; 3. Protective layer; 4. External connecting rod; 5. Double-headed screw; 6. Threaded connection hole; 7. Adhesive filler; 8. External bolt; 9. Screw hole; 10. Through hole in bamboo wall. DETAILED DESCRIPTION

[0067] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings herein can be arranged and designed in various different configurations. The following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0068] A method for selecting and constructing round bamboo composite profiles comprises the following steps:

[0069] S1, selecting a plurality of round bamboos of substantially the same size and specifications, cutting them into the same length, and obtaining the cross-sectional parameters of the small end of each hollow round bamboo 1;

[0070] S2. Cut a steel bar of 200 mm to 500 mm in length, drill a threaded connection hole 6 on the end face of one end of the steel bar, and drill a plurality of screw holes 9 along the radial direction of the steel bar at the other end of the steel bar to form an external connection rod 4;

[0071] S3, drilling a through hole 10 in the bamboo wall at the end of the hollow round bamboo 1 corresponding to the screw hole 9;

[0072] S4. External connection device structure of single round bamboo: Figure 2 、 Figure 3 、 Figure 7 and Figure 8 As shown, the external connecting rod 4 is embedded in the end of the hollow round bamboo 1 so that the end surface of the external connecting rod 4 near the threaded connection hole 6 is flush with the end surface of the hollow round bamboo 1. A double-headed screw 5 is passed through the bamboo wall through-hole 10 and the screw hole 9, and the double-headed screw 5 is anchored to the bamboo wall of the hollow round bamboo 1 with an internal and external thread nut; an adhesive filler 7 is poured at the end of the hollow round bamboo 1 to fix the external connecting rod 4 and bond the external connecting rod 4 to the inner wall of the hollow round bamboo 1; a fiber tape is bonded and wrapped around the outer wall of the hollow round bamboo 1 to form a fiber hoop;

[0073] The external connection device structure of multiple round bamboo composite profiles: Figure 4 As shown, a plurality of hollow round bamboos 1 of the same length are arranged in a staggered manner according to the large and small ends into a plate or column shape, the external connecting rod 4 is embedded in the end of the hollow round bamboo 1 so that the end face of the external connecting rod 4 close to the threaded connection hole 6 is flush with the end face of the hollow round bamboo 1, and a double-headed screw 5 is sequentially passed through the bamboo wall through-hole 10 and the screw hole 9, and the exposed head of the double-headed screw 5 is anchored with a nut to form a spliced ​​round bamboo frame; an adhesive filler 7 is poured at the end of the hollow round bamboo 1 to fill and bond the cavity between the external connecting rod 4 and the inner wall of the hollow round bamboo 1 to fix the external connecting rod 4; a fiber material is wrapped and bonded to the outer periphery of the spliced ​​round bamboo frame to form a fiber winding layer 2; and the adhesive filler 7 is filled in the gap between the fiber winding layer 2 and the spliced ​​round bamboo frame and the hollow round bamboo 1.

[0074] Specifically, after step S4, concrete is poured on the fiber winding layer 2 and on the periphery of the assembled round bamboo frame to form a protective layer 3.

[0075] Specifically, in step S1, the specific steps are as follows:

[0076] a. Take the test sample from the round bamboo and do the bamboo tensile strength test along the grain. The bamboo tensile strength along the grain f can be measured. cu value.

[0077] b. Measure the cross-sectional area of ​​the bamboo wall. The bamboo is divided into a large section and a small end. Take the small end of the bamboo and measure the cross-sectional area of ​​the bamboo wall. Figure 5 The outer and inner diameters of the round bamboo at points ae, bf, cg, and dh are averaged, denoted as d1; the inner diameters are averaged, denoted as d2. The cross-sectional area of ​​the bamboo wall at the small end is then expressed as:

[0078]

[0079] The expression of tensile stress along the grain of round bamboo's small end is:

[0080]

[0081] Where, d1 is the average outer diameter of the small end of the round bamboo, d2 is the average inner diameter of the small end of the round bamboo, and A yzb is the cross-sectional area of ​​the bamboo wall at the small end of the round bamboo, F cu is the tensile strength of hollow round bamboo along the grain, f cu It is the tensile strength of bamboo along the grain.

[0082] The present invention uses double-headed screw 5, external connecting rod 4, external bolt 8. The specific selection scheme is as follows Figure 1 shown.

[0083] Specifically, in step S4, the number and type of double-headed screws 5 are selected according to the tensile strength along the grain of the hollow round bamboo 1 and the number of screw holes. The specific steps are as follows:

[0084] The double-headed screws 5 in this structure are all double-shear-loaded. In this embodiment, the number of double-headed screws 5 is selected as two, and the shear surface of the two double-headed screws 5 is 4 (i.e., n v =4).

[0085] According to the "Mechanical and physical properties of bolts, screws and studs" (GB / T3089.1-2010 Table 3), select the specific material of the double-headed screw 5 and check the shear strength f of the double-headed screw 5. vlg .

[0086] 1) The formula for calculating the shear resistance of the double-headed screw is:

[0087]

[0088] 2) The calculation formula for the diameter of the double-headed screw 5 is:

[0089]

[0090] Where: d lg To meet the strength requirements of the twin-head screw diameter, N vlg is the screw shear stress, f vlgis the screw shear stress strength, n v is the number of shear surfaces of the screw.

[0091] Initially select the standard double-head screw 5 model, its diameter is d lgx .

[0092] 3) Calculate the yield strength N of the double-headed screw 5 at the round bamboo wall clg .like Figure 6 As shown, the pressure areas of the double-headed screw 5 are D lg ×t 11 , D lg ×t 12 , D lg ×t 21 , D lg ×t 22 To simplify the calculation, we use Then, according to the "Mechanical and physical properties table of bolts, screws and studs" (GB / T3089.1-2010 Table 3), the standard value of screw yield strength f of the primary double-head screw material 5 is obtained by looking up the table. clg , calculate the screw yield strength N clg .

[0093]

[0094] Where: N clg is the screw yield force; f clg is the standard value of screw yield strength;

[0095] like Figure 7 As shown, when N clg >F cu , in line with the requirements, the initial selection of double-headed screw 5 model is feasible, recorded as d lgz ; When N clg ≦F cu , select a larger double-headed screw 5 diameter value and substitute it into d lgx , until the calculated N clg >F cu The screw determined at this time is the final screw, and its diameter is recorded as d lgz .

[0096] Furthermore, in step S4 , internal and external thread nuts may be provided in the bamboo wall through-holes 10 to facilitate anchoring of the double-headed screw 5 and the hollow round bamboo 1 .

[0097] Specifically, in step S2, the distance between any screw hole and the end of the external connecting rod 4 is greater than or equal to the outer diameter of the hollow round bamboo 1, and the distance between any screw holes 9 is greater than or equal to the diameter of the external connecting rod 4; there is an angle between the axes of different screw holes 9, which follows the expression:

[0098]

[0099] Wherein, ∠B is the angle between adjacent screw holes 9 , and n is the number of double-headed screws 5 .

[0100] Specifically, in step S2, the size of the threaded connection hole 6 and the corresponding model of the external bolt 8 are selected according to the tensile strength of the hollow round bamboo 1. The specific steps are as follows:

[0101] a. According to the "Mechanical and physical properties of bolts, screws and studs" (GB / T3089.1-2010 Table 3), select the bolt material to obtain the tensile strength value f tls , the bolt diameter selection requirements are:

[0102]

[0103] Where: F tls is the tensile stress of the external bolt 8, f tls is the tensile strength value of the external bolt 8, d ls The minimum diameter of the external bolt 8 that meets the strength requirements.

[0104] b. Calculate the minimum diameter d ls Then, check the Mechanical and Physical Properties of Bolts, Screws and Studs (GB / T3089.1-2010 Table 3) and select the one with a diameter larger than and closest to d ls Standard bolt model with a diameter of d lsz .

[0105] Specifically, in step S2, the model parameters of the external connecting rod 4 are selected according to the tensile strength of the hollow round bamboo 1 and the model parameters of the external bolt 8. The specific steps are as follows:

[0106] According to GB1499.2-2024 "Steel for reinforced concrete Part 2: Hot-rolled ribbed steel bars" - Table 6 Mechanical properties of steel bars, select the tensile strength value f of the steel bar material for the external connecting rod 4 tgj ,

[0107]

[0108] The diameter of the external connecting rod 4 is:

[0109]

[0110] Among them: F tlkc f is the tensile stress at the screw hole end of the external connecting rod 4; tgj is the tensile strength of the external connecting steel bar 4; d gj The minimum diameter of the external connecting rod 4 to meet the strength requirements; d lszThe final diameter of the external bolt 8 is equal to the inner diameter of the threaded connection hole 6.

[0111] Check GB1499.2-2024 "Steel for reinforced concrete Part 2: Hot-rolled ribbed steel bars" - Table 6 Mechanical properties of steel bars. gj The diameter of the steel bar model with the closest value is d gjx .

[0112] b. Check the tensile strength of the external connecting rod 4 at the screw hole;

[0113] Calculate the cross-sectional area A of the external connecting rod at the screw lgk :

[0114]

[0115] Calculation: F tlgc =f tgj ×A lgc Value, such as F tlgc >F cu / 2, then the primary selected external connection steel bar model meets the requirements, recorded as d gjz Otherwise, select a larger outer diameter external connecting rod 4 and substitute the diameter value into d gjx , calculate F tlgc value, to meet F tlgc >F cu / 2 requirement, the external connecting rod 4 model meets the requirement, recorded as d gjz .

[0116] Among them, f tgj A is the tensile strength value of the external connecting rod 4; lgk It is the cross-sectional area of ​​the external connecting rod 4 at the screw.

[0117] c. Verify the yield strength of the external connecting rod 4 at the screw hole;

[0118] According to calculations, under normal circumstances, the compressive area here is larger than the compressive area on the bamboo side wall, so verification is generally not required.

[0119] The above calculations show that the components of the round bamboo connection device are determined based on the principle that they can withstand a greater tensile stress than the small end of the round bamboo. Therefore, after the above components are selected, the axial tensile stress at the end of the round bamboo composite profile can be calculated using the following calculation formula:

[0120]

[0121] Where: F is the tensile stress at the end of the round bamboo composite profile; δ is the reduction coefficient. This can be determined by analysis based on a large amount of experimental data. For example, referring to the research results of Fei Benhua et al., "Load-bearing Capacity of Bamboo Structural Material Connectors" (Journal of Nanjing Forestry University (Natural Science Edition), Vol. 32, No. 3, May 2008), a reduction coefficient of 0.95 can be taken; n is the number of hollow round bamboos 1 in the round bamboo composite profile that constitute the spliced ​​round bamboo frame; It is the sum of the tensile stress along the grain at the small end of all hollow round bamboos.

[0122] Specifically, after step S4, concrete is poured around the fiber hoop and the fiber winding layer as a protective layer.

[0123] Specifically, in step S4, the fiber winding layer 2 can be made of one or more combinations of bamboo fiber, glass fiber, and carbon fiber.

[0124] Specifically, in step S4, the bonding filler 7 can be selected from one or more combinations of mortar and concrete materials.

[0125] Example of calculation for selecting stud screw 5, external bolt 8, and external connecting rod 4

[0126] (1) Round bamboo, outer diameter d1 = 90 mm, inner diameter d2 = 74.7 mm (wall thickness is 8.5% of outer diameter) tensile strength along the grain is f cu =103.796MPa (the standard strength value is 122.113MPa according to the coefficient of 0.85); then the tensile stress of round bamboo is:

[0127]

[0128] (2) Double-head screw 5, check the "Mechanical and physical properties of bolts, screws and studs" (GB / T3089.1-2010 Table 3), and choose a high-strength screw with a material of 8.8. The standard value of tensile strength is 800MP, the standard value of yield strength is 640MP, and the standard value of shear strength is 480MP.

[0129]

[0130] The initial nominal diameter of the screw is 10mm, then d lgx =10mm.

[0131] (3) Calculate the yield strength of the double-headed screw 5 at the round bamboo wall

[0132] The calculation formula for the screw yield strength is:

[0133] f clg =640MP

[0134] n v =4

[0135]

[0136] If it does not meet the requirements, continue to select a screw with a nominal diameter of 12mm, then take d lgx =12mm.

[0137]

[0138] Meets the requirements, then d lgz =12mm.

[0139] (4) External bolts 8, check the "Mechanical and physical properties of bolts, screws and studs" (GB / T3089.1-2010 Table 3). Select high-strength bolts with a material of 10.9 and a tensile strength standard value of 1000MP.

[0140]

[0141] Select the bolt model with a diameter of 18mm, d lsz =18mm.

[0142] (5) Preliminary selection of the model of the 4 threaded steel bars for the external connecting rod.

[0143] According to GB1499.2-2024 "Steel for reinforced concrete Part 2: Hot-rolled ribbed steel bars" - Table 6 Mechanical properties of steel bars, the steel bar material used for the external connecting rod 4 is HRB400, and the standard value of tensile strength is f tgj =540MP.

[0144]

[0145] The initial diameter of the steel bar is 32mm, d gjx =32mm.

[0146] (6) Verify the tensile strength of the external connecting rod 4 at the screw hole.

[0147] The diameter of the screw hole of the external connecting rod 4 is recorded as D lgk , D lgk =12+4=16mm, (where 4mm is the gap) the cross-sectional area of ​​the external connecting rod 4 is A lgk .

[0148]

[0149] Then we have:

[0150] F tlgc =f tgj ×A lgk=540×489.65=264411N>205321.91 / 2=102660.96N

[0151] Meet the requirements, select d gjz =32mm.

[0152] Therefore, the selection of the main components of this connection device can be determined as follows:

[0153] Double-head screw 5: material grade 8.8, diameter 12mm.

[0154] External bolt 8: material grade 10.9, diameter 18 mm.

[0155] External connecting rod 4: material HRB400, diameter 32mm, inner diameter of the end screw hole 18mm.

[0156] According to the above procedures and calculations, the reference selection table of components shown in Table 1 can be obtained.

[0157] Table 1 Reference selection table for round bamboo end connection device components

[0158]

[0159] Note: 1. According to "Research and Application of Modern Bamboo Structural Building Systems" (by Hao Jiping and Tian Limin), the wall thickness of round bamboo is 8.5% of the outer diameter of the round bamboo, the standard value of tensile strength along the grain (with knots) is 122.113 MPa, and the heterogeneity coefficient of raw bamboo is 0.85. In this column, 103.796 MPa is used as the standard value. 2. The parameters for rebar are based on GB1499.2-2024, "Steel for Reinforced Concrete - Part 2: Hot-rolled Ribbed Bars," and the material is HRB400. 3. The parameters for bolts and screws are based on GB / T3089.1-2010, "Mechanical and Physical Properties of Bolts, Screws, and Studs," with the screw material being grade 8.8 and the bolt material being grade 10.9.

[0160] The above is a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and concepts of the present invention, should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for selecting and constructing round bamboo composite profiles, characterized by: The steps include: S1, select a plurality of round bamboos of substantially the same size and specifications, cut them into the same length, and obtain the parameters of the hollow round bamboo (1); S2, cutting a steel bar of 200 mm to 500 mm in length, drilling a threaded connection hole (6) on the end face of one end of the steel bar, and drilling a plurality of screw holes (9) along the radial direction of the steel bar at the other end of the steel bar to form an external connection rod (4); S3, drilling a through hole (10) in the bamboo wall at the end of the hollow round bamboo (1) corresponding to the screw hole (9); S4. Arrange at least one hollow round bamboo (1) of the same length in a staggered manner at the large and small ends to form a plate or column shape, embed the external connecting rod (4) into the end of the hollow round bamboo (1), so that the end face of the external connecting rod (4) close to the threaded connection hole (6) is flush with the end face of the hollow round bamboo (1), and use a double-headed screw (5) to pass through the bamboo wall through-hole (10) and the screw hole (9) and tighten them to form a spliced ​​round bamboo frame; pour an adhesive filler (7) at the end of the hollow round bamboo (1), fix the external connecting rod (4), and form a round bamboo composite profile.

2. The method for selecting and constructing round bamboo composite profiles according to claim 1, characterized in that: In step S1, the parameters include: the tensile strength along the grain of the bamboo material, the bamboo wall cross-sectional area at the small end of the hollow round bamboo (1), and the tensile strength along the grain of the hollow round bamboo (1).

3. The method for selecting and constructing round bamboo composite profiles according to claim 2, characterized in that: In step S4, the number and model of the double-headed screws (5) are selected according to the tensile strength along the grain of the hollow round bamboo (1) and the number of screw holes (9).

4. The method for selecting and constructing round bamboo composite profiles according to claim 3, characterized in that: In step S2, the distance between any one of the screw holes (9) and the end of the external connecting rod (4) is greater than or equal to the diameter of the external connecting rod (4), and the distance between any one of the screw holes (9) is greater than or equal to the diameter of the external connecting rod (4); and there is an angle between the axes of the different screw holes (9), which follows the expression: , where ∠B is the angle between adjacent screw holes (9), and n is the number of double-headed screws (5).

5. A method for selecting and constructing round bamboo composite profiles according to any one of claims 2 to 4, characterized in that: In step S2, the model of the external bolt (8) and the size of the corresponding threaded connection hole (6) are selected according to the tensile strength along the grain of the hollow round bamboo (1).

6. A method for selecting and constructing round bamboo composite profiles according to any one of claims 2 to 4, characterized in that: In step S2, the model parameters of the external connecting rod (4) are selected according to the tensile strength along the grain of the hollow round bamboo (1).

7. A method for selecting and constructing round bamboo composite profiles according to any one of claims 1 to 3, characterized in that: In step S4, the method further comprises: when the number of hollow round bamboos (1) constituting the spliced ​​round bamboo frame is equal to 1, bonding and winding a fiber tape on the outer wall of the hollow round bamboo (1) to form a fiber hoop; when the number of hollow round bamboos (1) constituting the spliced ​​round bamboo frame is greater than 1, winding and bonding a fiber material to the outer periphery of the round bamboo composite profile to form a fiber winding layer (2), and filling a bonding filler (7) in the gap between the fiber winding layer (2) and the spliced ​​round bamboo frame and the hollow round bamboo (1).

8. The method for selecting and constructing round bamboo composite profiles according to claim 7, characterized in that: The fiber hoop and the fiber winding layer (2) can be selected from one or more combinations of bamboo fiber, glass fiber, and carbon fiber.

9. A method for selecting and constructing round bamboo composite profiles according to any one of claims 1 to 4, characterized in that: The bonding filler (7) may be selected from one or more combinations of mortar and concrete.

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