A modular design method based on CS-FC-SB composite wall

Abstract

The present invention discloses a modular design method based on a CS-FC-SB combined wall. The modular design method includes decomposing the CS-FC-SB wall into a foamed concrete wall (CS-FC) with a cold-formed steel frame, an outer ecological straw board (SB), and end columns, and finally designing the connection method. The size, reinforcement, and foamed concrete model of the CS-FC are selected based on a performance-based design method, the thickness of the SB is obtained based on a finite element analysis method, the size of the end columns is constructed with reference to standard specifications, and the design of key parameters such as welding, self-tapping screws, or bolt connections is obtained based on a simplified calculation formula for the seismic requirements of the CS-FC-SB combined wall. The above modular design method can greatly simplify the calculation and analysis process of the CS-FC-SB combined wall. Only welding, self-tapping screws, and bolt connections need to be calculated on site, which can effectively shorten the construction period and reduce construction costs. It can be promoted and applied in low-rise and multi-story rural and town building structures.

Description

Technical Field

[0001] The present invention belongs to the field of construction, and specifically relates to a modular design method based on a CS-FC-SB composite wall, wherein the foamed concrete wall with a cold-formed steel frame is referred to as CS-FC, and the outer ecological straw board is referred to as SB. Background Art

[0002] Currently, most rural buildings are constructed using masonry, brick-concrete, and cold-formed steel structures. The former, due to their age and lack of rational design, suffer from poor integrity, while cold-formed steel structures offer poor sound and thermal insulation. Foamed concrete, a lightweight, porous cement-based material, offers advantages such as light weight, thermal insulation, sound insulation, environmental friendliness, excellent fire resistance, and strong energy dissipation and earthquake resistance. In recent years, it has been increasingly adopted as a shear wall structure in rural buildings.

[0003] However, the discreteness of foamed concrete materials is large, and the quality of the wall depends on the level of engineering casting. Therefore, foamed concrete shear wall structures are usually prefabricated in the factory and then assembled on site. The assembly method often uses mortar, reserved steel bars or shear keys to connect, which is a complicated process. The construction and connection of prefabricated walls are mostly based on the experience of designers, and there is no corresponding design method.

[0004] In recent years, with the country's increasing focus on rural architecture, the design requirements for foamed concrete shear walls in rural areas have shifted from a single safety criterion to one that emphasizes comfort and multifunctionality. New demands are being placed on foamed concrete shear walls for various shapes, such as cross-shaped and T-shaped walls, reliable connection methods, and sophisticated and convenient design approaches.

[0005] The present invention proposes a CS-FC-SB combined wall. It includes cold-formed steel frames and end columns for welding and assembly, an outer layer of ecological straw boards, and an inner layer of foamed concrete. Ribs are welded to the inner side of the cold-formed vertical steel webs, and the straw boards are embedded in the rib grooves. The straw boards and the vertical and horizontal cold-formed steel form a closed space for pouring foamed concrete. The cold-formed steel, foamed concrete and ecological straw boards together form a combined force system. At the same time, the foamed concrete and ecological straw boards are lightweight insulation materials, which can make the combined wall have good thermal insulation properties and are easy to maintain in the future. In order to further promote its use, a corresponding design method is urgently needed. Therefore, the present invention proposes a modular design method for CS-FC-SB combined walls. Summary of the Invention

[0006] To address the above issues, the present invention discloses a modular design method based on CS-FC-SB composite walls. This modular design method can greatly simplify the calculation and analysis process of CS-FC-SB composite walls. On-site calculations only require welding, self-tapping screws, and bolt connections, effectively shortening the construction period and reducing construction costs. The method can be widely applied in low-rise and multi-story rural and urban building structures.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A modular design method based on the CS-FC-SB composite wall is proposed. The foamed concrete precast wall with a cold-formed steel frame, the end columns, and the outer ecological straw board are designed separately. After the above modules are designed, only the connection nodes between the end columns and the foamed concrete precast wall need to be designed during assembly.

[0009] The CS-FC-SB composite wall comprises a precast foamed concrete wall with a cold-formed steel frame, end columns, outer ecological straw panels, and connection nodes. The precast wall includes a square cold-formed steel frame for welded assembly, embedded vertical cold-formed steel for securing the straw panels, vertical bracing to prevent the straw panels from expanding, and an inner foamed concrete filling. The end columns are made of section steel or concrete-filled steel tube columns. The end columns can be connected to the steel frame of the foamed concrete precast wall using pre-set bolts, studs, or welding. The foamed concrete precast walls I, II, III, and IV with cold-formed steel frames can be connected in angled, T-shaped, or cross-shaped configurations.

[0010] The design of the foamed concrete prefabricated wall with cold-formed steel frame is divided into compressive bearing capacity design and shear bearing capacity design. The compressive bearing capacity design is designed using formula (1), and the shear bearing capacity design value is designed using formula (2).

[0011] N c =0.2ζf c bh (1)

[0012] V wh =(0.95+0.07λ1+0.025λ2)(0.077f c hb+0.26N c )cosθ (2)

[0013] The thickness of the outer ecological straw board is selected and calculated using formulas (3) and (4). The finite element method can be used to discretize and calculate the formula, and the design is carried out based on the maximum stress value under the allowable displacement angle.

[0014] The end columns are sized according to standard construction requirements. For concrete columns, refer to GB 50010, the standard for concrete; for steel columns, refer to GB 50017, the standard for steel structures. If bolts and studs are reserved for connection, the construction of embedded components in the concrete column must still meet the requirements of GB 50010.

[0015] After the connection form is designed, the connection node becomes a weak point. According to the node form adopted, the corresponding design method is carried out. The calculation formula is shown in formula (5) and (9):

[0016] l weld = max{min(l1,l2),l3} (5)

[0017] N = max {N1,N2} (9)

[0018] According to the modular design method based on the CS-FC-SB composite wall described in the present invention, the cold-formed steel-foamed concrete-ecological straw board assembled composite wall is produced, which reduces the air pollution caused by straw burning and turns waste into treasure. It is rolled at high temperature and high pressure without polluting materials such as glue. The straw board has good bending resistance and thermal insulation performance, and can also serve as a template for internal foam concrete in the composite wall. Internal foam concrete has excellent thermal insulation performance and is lightweight, reducing the weight of the composite wall. Straw board and foam concrete can effectively avoid local buckling of cold-formed steel frames. Through the reasonable combination of outer straw board and internal foam concrete, the standard of 65% building energy saving in hot summer and cold winter areas can be achieved, and it can withstand vertical pressure and horizontal shear force, has good seismic performance, and can achieve structural enclosure-insulation integration.

[0019] The modular design method proposed in this invention can greatly simplify the calculation and analysis process of the CS-FC-SB composite wall. On-site calculations only require welding, self-tapping screws, and bolt connections. The modules are prefabricated in the factory, without post-casting strips or on-site wet work. On-site assembly is convenient and efficient, effectively shortening the construction period, turning waste into treasure, and eliminating the need for subsequent construction of a building insulation layer, thereby reducing construction costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a design drawing of the present invention.

[0021] Figure 2 This is the top view of module I.

[0022] Figure 3 Schematic diagram of the cold-formed steel frame of module I.

[0023] Figure 4 Schematic diagram of the vertical steel ribs of module I.

[0024] Figure 5 Schematic diagram of the vertical cold-formed steel of module I.

[0025] Figure 6 This is the top view of module II.

[0026] Figure 7 Schematic diagram of the frame of module II with holes, module I and the end column frame.

[0027] Figure 8 This is a cross-sectional view of module I with holes in the frame of module II and the end column.

[0028] Figure 9 This is a structural diagram of a straight-line wall.

[0029] Figure 10 This is the structural diagram of the corner wall.

[0030] Figure 11 This is the T-shaped wall structure diagram.

[0031] Figure 12 This is a diagram of the cross-shaped wall structure.

[0032] Figure 13 This is a three-dimensional diagram of a T-shaped wall.

[0033] List of Figure Symbols:

[0034] 1. Cold-formed steel frame, 2. Vertical cold-formed steel, 3. Tie rods, 4. Outer ecological straw board, 5. Foamed concrete, 6. Box-type end columns, 100, self-tapping screws; 101, vertical steel ribs; 102, horizontal U-shaped steel; 1010, upper and lower end ribs; 1020, equally spaced holes; 1021, elliptical hole one; 201, elliptical hole two; 601 and 602, vertical U-shaped steel; 6010, elliptical hole three. DETAILED DESCRIPTION

[0035] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. (The calculation methods for the straight, T-shaped, and cross-shaped types are similar and will be explained together at the end.) Example

[0036] A CS-FC-SB combined wall comprises a cold-formed steel frame 1 for assembly. The cold-formed steel frame 1 is provided with vertical steel ribs 101 for fixing straw boards 4. The outer ecological straw boards 4 are clamped in the vertical steel ribs 101, and vertical cold-formed steel 2 is embedded inside. Tie rods 3 are provided on the outside. The cold-formed steel frame 1 can be used for welding or connecting into a wall group using L-shaped steel sheets. Example

[0037] According to a CS-FC-SB combined wall described in Example 1, the cold-formed steel frame 1 includes vertical cold-formed steel welded with ribs 101, which are used to clamp the straw board 4; the embedded vertical cold-formed steel 2 can prevent the straw board 4 from being concave, and at the same time improve the vertical steel matching rate. The vertical pull bars 3 on the outside of the straw board 4 can prevent the straw board from expanding outward during pouring. The cold-formed steel frame 1 is fixed to the straw board 4 by self-tapping screws 100. The upper horizontal U-shaped steel 102 is densely covered with evenly spaced holes 1020, which are used to pour and fill the foamed concrete to form module I, such as Figure 2 shown. Example

[0038] Fabricate the frame of the perforated frame module I: Based on Example 2, increase the length of the upper and lower horizontal U-shaped steels 102 by the width of the box-shaped end column 6. The two vertical U-shaped steels 601 and 602 are welded to each other via a Type I weld to form the box-shaped end column 6, which is then clamped into the upper and lower horizontal U-shaped steels 102. Elliptical holes 1021 and 6010 are provided on the contact surface between the perforated frame module I and the box-shaped end column, corresponding to the elliptical holes 6010, for pouring foam concrete to fill the holes and form a through hole. Concrete is poured from the evenly spaced holes 1020 in the upper horizontal U-shaped steel 102, extending all the way into the box-shaped end column 6 to form module II. Figure 6 shown.

[0039] The prefabricated modules I and II can be designed and assembled to meet the needs of long walls, corner walls, T-shaped walls, and cross-shaped walls. The modules can be connected by I-shaped welds or L-shaped steel sheets. Example

[0040] Long walls, corner walls, T-shaped walls, and cross-shaped walls are formed by prefabricating modules I and II and welding them on site with type I welds or connecting them with L-shaped steel sheets. Figure 13 As shown, self-tapping screws are used to connect the steel sheets and modules. The self-tapping screws are spaced according to specifications, with L-shaped steel sheets placed every 500 mm vertically. The composite wall and steel beams or cold-formed steel composite beams can be connected by welding or bolting. Bolting requires pre-embedded screws in Modules I and II, and steel sleeves corresponding to the screws embedded in the corresponding steel beams or cold-formed steel composite beams. The screws pass through the steel sleeves and are secured with nuts at the ends.

[0041] Design Methodology:

[0042] (1) According to the above wall structure, the pressure P and shear design value V1 of the single wall are obtained in the professional design software (Note: Here is the design value obtained under a certain load rather than the bearing capacity design value), assuming that the wall section height is h. When the foamed concrete grade is 500kg / m 3 When the compressive strength f c 4MPa, E cis the elastic modulus of foam concrete under pressure, which is 19 GPa. The minimum wall thickness b can be determined by the following formula: min , must meet the following requirements:

[0043] P≤N c ; b1 ≥ P / (0.2ζf c h)

[0044] V1≤(0.95+0.07λ1+0.025λ2)(0.077f c hb+0.26N c )cos(1 / 100)

[0045] b2≥{V1 / (0.95+0.07λ1+0.025λ2) / cos(1 / 100)-0.26N c} / 0.077f c h

[0046] b min =max(b1, b2)

[0047] ζ is the correction factor for the compressive bearing capacity of the embedded vertical cold-formed steel considering the constraint effect of the straw board. According to the test and finite element simulation results, the correction factor is taken as 1.05 (E s A s / (E c b min h));

[0048] E s is the elastic modulus of the embedded vertical cold-formed steel;

[0049] A s is the cross-sectional area of ​​the embedded vertical cold-formed steel;

[0050] f c is the compressive strength of foam concrete prism, unit: MPa;

[0051] h is the height of the wall section;

[0052] (2) When the straw board size is known and the thickness is determined by using the finite element method and discrete formula 3, the bottom boundary is taken as rigid connection, the board thickness is 1, the top forced displacement is 0.01H, and the maximum strain is σ max , the design thickness d of the ecological board meets:

[0053] d>f yh / σ max

[0054] (3) The end column structure can be determined according to the relevant specifications.

[0055] (4) After completing the above three steps, the design of all prefabricated parts of the CS-FC-SB composite wall can be realized. This part is processed in the factory and transported to the site. The subsequent determination only requires the length of the weld and the number of bolts or studs.

[0056] (5) Formulas 5 and 9 can be used to determine the corresponding weld length, weld leg size, number of bolts, bolt diameter, and bolt strength, ultimately realizing the modular design method of the CS-FC-SB composite wall.

[0057] For welded joints, the weld leg size h f It can be 4mm or 5mm. The total length of the weld is calculated as follows:

[0058] l weld = max{min(l1,l2),l3} (5)

[0059] l1={1.05(0.95+0.07λ1+0.025λ2)(0.077f c hb+0.26N c )cosθ} / f tw h f (6)

[0060] l2=0.8NsH (7)

[0061] l3= 60h f H (8)

[0062] Among them, N s is the number of welds; for a straight-line combined wall, N s =4; for T-shaped composite walls, N s =6; for cross-shaped composite walls, N s =8; H is the vertical distance between the point where the horizontal shear force of the wall acts and the wall foundation; f tw Design strength for fillet welds;

[0063] For bolted or studded nodes, the minimum diameter of the bolts or studs is 10 mm, and the number of bolts is calculated as follows:

[0064] N = max {N1,N2} (9)

[0065] N1={1.05(0.95+0.07λ1+0.025λ2)(0.077f c hb+0.26N c )cosθ} / (f vb A sb ) (10)

[0066] Among them, A sbis the minimum cross-sectional area of ​​the bolt;

[0067] N1 is the minimum number of bolts calculated based on the vertical shear resistance of the node;

[0068] N2 is the minimum number of bolts obtained based on the test structure. For the straight-shaped composite wall, N2=24; for the T-shaped and cross-shaped composite walls, N2=48;

[0069] f vb is the design strength of the bolt or stud.

[0070] It should be noted that the above content merely illustrates the technical idea of ​​the present invention and cannot be used to limit the scope of protection of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A modular design method based on CS-FC-SB combined walls, characterized by: The CS-FC-SB wall comprises a foamed concrete prefabricated wall with a cold-formed steel frame, end columns, outer ecological straw boards and connection nodes. The prefabricated wall comprises a square cold-formed steel frame (1) for welding and assembly, an embedded vertical cold-formed steel (2) for fixing the straw board, a vertical brace (3) for preventing the straw board from expanding outward, and foamed concrete (4) filled in. The end columns are steel sections or steel tube concrete columns. The end columns are connected to the steel frame of the foamed concrete prefabricated wall by reserved bolts, studs or welding. The foamed concrete prefabricated walls I, II, III and IV with cold-formed steel frames can be connected in a corner, T-shaped or cross-shaped manner. The foamed concrete prefabricated walls with cold-formed steel frames, end columns, and outer ecological straw panels are designed separately. After the above modules are designed, only the connection nodes between the end columns and the foamed concrete prefabricated walls need to be designed during assembly. The design of the foamed concrete prefabricated wall with cold-formed steel frame is divided into compressive bearing capacity design and shear bearing capacity design. The compressive bearing capacity design is designed using formula (1), and the shear bearing capacity design value is designed using formula (2). N c =0.2ζf c bh (1) Among them, N c is the vertical compressive bearing capacity; ζ is the correction factor for the compressive bearing capacity of the embedded vertical cold-formed steel considering the constraint effect of the straw board. According to the test and finite element simulation results, the correction factor is taken as 1.05 (E s A s / (E c bh)); E s is the elastic modulus of the embedded vertical cold-formed steel; A s is the cross-sectional area of ​​the embedded vertical cold-formed steel; E c is the compressive elastic modulus of foam concrete; f c is the compressive strength of foam concrete prism, unit: MPa; h is the height of the wall section; b is the width of the wall section; V wh =(0.95+0.07λ1+0.025λ2)(0.077f c hb+0.26N c )cosθ (2) Among them, V wh horizontal shear bearing capacity; λ1 is the correction coefficient considering the contribution of straw board to shear resistance, and f yh A sh / (0.077f c hb+0.26N c ); λ2 is the correction coefficient considering the contribution of straw board to shear resistance, and f yv A sv / (0.077f c hb+0.26N c ); f yh With f yv are the yield strengths of straw panels and vertical cold-formed steel, respectively; A sh is the cross-sectional area of ​​the horizontal tie rod; A sv is the cross-sectional area of ​​the vertical tie rod; θ is the maximum allowable displacement angle of the wall. According to the test and finite element results, the value is taken as 1 / 100.

2. The modular design method based on the CS-FC-SB combined wall according to claim 1, characterized in that: The thickness of the outer ecological straw board is selected and calculated using formulas (3) and (4). The finite element method is used to discretize and calculate the formulas, and the design is carried out based on the maximum stress value under the allowable displacement angle. （3） Where, u is the horizontal displacement and v is the vertical displacement; λ=E, E is the elastic modulus of the ecological straw board; μ is the Poisson's ratio of the ecological straw board; When the finite element method is used for calculation and the discrete formula (3), the bottom boundary is taken as rigid connection, the plate thickness is 1, and the top forced displacement is 0.01H, where H is the vertical distance between the horizontal shear force point of the wall and the wall foundation; the maximum strain is σ max , the design thickness d of the ecological board meets: d>f yh / s max (4).

3. The modular design method based on the CS-FC-SB combined wall according to claim 1, characterized in that: After the connection form is designed as above, the connection node becomes the weak point. According to the node form adopted, the corresponding design method is carried out. The calculation formula is shown in formula (5) and (9): For welded joints, the weld leg size h f Take 4mm or 5mm, and calculate the total length of the weld according to the following formula <h2 style=";text-align:left;direction:ltr">l<h2 style=";text-align:left;direction:ltr"> weld <h2 style=";text-align:left;direction:ltr"> = max{min(l1,l2),l3} (5) l1={1.05(0.95+0.07λ1+0.025λ2)(0.077f c hb+0.26N c )cosθ} / f tw h f (6) l2=0.8NsH (7) <h2 style=";text-align:left;direction:ltr">l3= 60h<h2 style=";text-align:left;direction:ltr"> f <h2 style=";text-align:left;direction:ltr"> H (8) Among them, N s is the number of welds; for a straight-line combined wall, N s =4; for T-shaped composite walls, N s =6; for cross-shaped composite walls, N s =8; H is the vertical distance between the point where the horizontal shear force of the wall acts and the wall foundation; f tw Design strength for fillet welds; For bolted or studded nodes, the bolt or stud size is 10 mm, and the number of bolts is calculated as follows: N = max {N1,N2} (9) N1={1.05(0.95+0.07λ1+0.025λ2)(0.077f c hb+0.26N c )cosθ} / (f vb A sb ) (10) Among them, A sb is the minimum cross-sectional area of ​​the bolt; N1 is the minimum number of bolts calculated based on the vertical shear resistance of the node; N2 is the minimum number of bolts obtained based on the test structure. For the straight-shaped composite wall, N2=24; for the T-shaped and cross-shaped composite walls, N2=48; f vb is the design strength of the bolt or stud.

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