Composite beam based on super-large-head studs

Abstract

The utility model relates to a composite beam based on super-large-head studs. The method is suitable for construction engineering technical field. According to the technical scheme, the composite beam based on the super-large-head studs is characterized in that a plurality of super-large-head studs I are fixed to a steel beam corresponding to a hogging moment area of the composite beam and located in a reinforced concrete plate above the steel beam, the diameter of a bolt rod of each super-large-head stud I is smaller than 10 mm, and the diameter of a bolt head of each super-large-head stud I is larger than or equal to 1.8 times of the diameter of the bolt rod of the super-large-head stud I; corresponding to a positive bending moment area of the composite beam, a plurality of super-large-head studs II are fixed on the steel beam, the super-large-head studs II are located in the reinforced concrete slab above the steel beam, the diameter of a bolt rod of each super-large-head stud II ranges from 10 mm to 25 mm, and the diameter of a bolt head of each super-large-head stud II is larger than or equal to 1.6 times of the diameter of the bolt rod of the super-large-head stud II; and a plurality of super-large-head studs III are fixed on the steel beam corresponding to a high shear area of the composite beam, the super-large-head studs III are positioned in the reinforced concrete slab above the steel beam, the diameter of each super-large-head stud III is greater than 25mm, and the diameter of a stud head of each super-large-head stud III is greater than or equal to 1.6 times of the diameter of a stud rod of each super-large-head stud III.

Description

Technical Field

[0001] The utility model relates to a composite beam based on super-large head stud bolts, which is applicable to the construction engineering industry, fields such as building structures and bridge structures. Background Art

[0002] Composite structural members are structural members formed by combining steel sections, steel pipes or steel plates with concrete to form an integral stressed structure, which have the advantages of high bearing capacity, good deformability, reasonable stress, etc., and have been widely used in various technical fields of the construction engineering industry. The key to ensuring that composite structural members give full play to the performance of the two materials is the connecting piece at the interface between steel and concrete. The connecting piece mainly plays two roles in the composite structural member: (1) Shear resistance. Shear resistance is also anti-slip. The connecting piece needs to be able to bear the interface shear force between steel and concrete, effectively limit the free sliding of the two, and ensure that the two form an integral stressed member under load. (2) Anti-pulling. Anti-pulling is also anti-lifting. It is necessary to resist the interface normal stress between steel and concrete, and be able to effectively prevent the vertical separation and lifting of the two, and ensure that the two form an integral stressed member under load.

[0003] An important source of the shear bearing capacity of stud bolts is the interface friction force between the stud bolts and concrete. There will be interface friction force only when there is pressure on the interface, and the existence of pressure on the interface means that there is tension in the stud bolt. The tension is anchored to the stud bolt head. Therefore, increasing the area of the stud bolt head can increase the bearing area between the stud bolt head and concrete, increase the ability of the stud bolt to bear tension, and then increase the friction force and the shear resistance of the stud bolt.

[0004] Furthermore, taking the composite beam in the field of building engineering or the composite beam bridge in the field of bridge engineering as an example for illustration. The relevant specifications clearly state that the form of the connecting piece between the steel beam and the concrete slab should preferably be a cylinder head weld stud (also known as a stud bolt), and channel steel can also be used. However, there are the following problems in the actual engineering use of stud bolt connectors:

[0005] (1) The stud bolt connectors in the negative moment area will put the concrete slab in a tensile state, resulting in accelerated cracking of the concrete slab.

[0006] (2) When the thickness of the concrete slab becomes thinner due to the application of materials such as ultra-high performance concrete, the stud bolt length-diameter ratio usually cannot meet the recommended limit of not less than 4, and it may be difficult to meet the anti-pulling requirements of the stud bolts, thereby affecting the shear performance of the stud bolts.

[0007] (3) In the high shear area, a large number of stud bolt connectors are arranged to improve the shear strength, but too dense stud bolts will have the problem of group stud effect, resulting in uneven stress of the stud bolts and strength reduction of the stud bolts. Summary of the Invention

[0008] The technical problem to be solved by the utility model is: aiming at the above problems, to provide a composite beam based on super-large head stud bolts.

[0009] The technical solution adopted by the utility model is as follows: a composite beam based on super-large head studs, which is characterized in that it includes:

[0010] Corresponding to the negative bending moment area of the composite beam, a number of super-large head studs Ⅰ are fixed on the steel beam. The super-large head studs Ⅰ are located in the reinforced concrete slab above the steel beam. The shank diameter of the super-large head stud Ⅰ is less than 10 mm, and the head diameter is greater than or equal to 1.8 times its shank diameter;

[0011] Corresponding to the positive bending moment area of the composite beam, a number of super-large head studs Ⅱ are fixed on the steel beam. The super-large head studs Ⅱ are located in the reinforced concrete slab above the steel beam. The shank diameter of the super-large head stud Ⅱ is between 10 mm and 25 mm, and the head diameter is greater than or equal to 1.6 times its shank diameter;

[0012] Corresponding to the high shear area of the composite beam, a number of super-large head studs Ⅲ are fixed on the steel beam. The super-large head studs Ⅲ are located in the reinforced concrete slab above the steel beam. The diameter of the super-large head stud Ⅲ is greater than 25 mm, and its head diameter is greater than or equal to 1.6 times its shank diameter.

[0013] The length-diameter ratios of the super-large head studs Ⅰ, Ⅱ, and Ⅲ are not less than 4 or greater than 2 and less than 4.

[0014] The head diameter of the super-large head stud Ⅰ is 2.2 times or more of its shank diameter.

[0015] The head diameter of the super-large head stud Ⅱ is 1.9 to 2.2 times or more of the shank diameter.

[0016] The shank diameter of the super-large head stud Ⅱ d and the head diameter d k are respectively:

[0017] .

[0018] The head diameter of the super-large head stud Ⅲ is 1.9 times or more of its shank diameter.

[0019] The super-large head studs are made of ML15 or ML15Al steel with a tensile strength of not less than 400 MPa, or made of steel with a tensile strength of not less than 600 MPa.

[0020] The beneficial effect of the utility model is that when the composite beam is sheared, tensile force will be generated on the studs. The utility model increases the bearing area between the stud head and the concrete by enlarging the stud head diameter, thereby increasing the pressure at the interface between the concrete and the steel beam, achieving the purpose of locking the tensile force on the studs, and further increasing the shear resistance of the studs in the composite beam.

[0021] In the present utility model, for the super-large head stud I, the small-diameter stud bar can reduce the shear stress between the steel beam and the concrete slab, reduce the tensile stress brought by the stud to the concrete floor slab, and effectively avoid the cracking of the floor slab. At the same time, the super-large head can provide greater anchoring force for the stud, ensuring the effective cooperative work between the steel beam and the concrete floor slab.

[0022] In the present utility model, the super-large head stud II can replace the function of the ordinary stud, and is especially suitable for the situation where the length-diameter ratio of the stud cannot meet the limit value of not less than 4 due to the thinning of the concrete slab. By using the super-large head stud with an ordinary diameter, the super-large head can improve the anchoring force of the stud in the concrete slab, prevent the concrete slab from being lifted, ensure that the stud can exert normal shear strength, achieve the purpose of not needing to reduce the shear strength of the stud, and ensure the effective cooperative work between the steel beam and the concrete floor slab.

[0023] In the present utility model, the super-large head stud III can increase the shear stress between the steel beam and the concrete slab, reduce the arrangement of the number of studs, and avoid the group stud effect caused by the over-dense arrangement of studs. At the same time, the super-large head can provide greater anchoring force for the stud, ensuring the effective cooperative work between the steel beam and the concrete floor slab. Description of the Drawings

[0024] Figure 1 Shows the stress mechanism of the stud in the composite beam.

[0025] Figure 2 Schematic structural diagram of the embodiment (the end is a fixed end).

[0026] Figure 3 Schematic structural diagram of the embodiment (the end is a simply supported end).

[0027] Figure 4 Schematic diagram of the application of the composite beam in the building structure in the embodiment.

[0028] Figure 5 Schematic diagram of the application of the composite beam in the bridge structure in the embodiment.

[0029] Figure 6 For Figure 4 A-A sectional view.

[0030] Figure 7 For Figure 4 B-B sectional view.

[0031] Figure 8 For Figure 5 A-A side view.

[0032] Figure 9 For Figure 5 B-B side view.

[0033] Figure 10 For Figure 5C-C cross-sectional side view.

[0034] Figure 11 Schematic diagram of the super-large head stud structure (a is stud I; b is stud II; c is stud III).

[0035] Figure 12 Schematic diagram of the super-large head stud structure with different stud head types.

[0036] Figure 13 Schematic diagram of the stud size.

[0037] Figure 14 Schematic diagram of the stud pull-out failure.

[0038] Figure 15 Load-displacement relationship diagram in the embodiment.

[0039] Figure 16 Shear stiffness-bolt head diameter magnification factor relationship diagram.

[0040] 1. Vertical member; 2. Steel beam; 21. Flange; 22. Web; 3. Reinforced concrete slab; 31. Concrete; 32. Longitudinal in-slab reinforcement; 33. Transverse in-slab reinforcement; 4. Stud; 41. Super-large head stud I; 42. Super-large head stud II; 43. Super-large head stud III; 4a. Stud head; 4b. Stud shank; 4c. Arc starting point. Specific implementation mode

[0041] This embodiment is a composite beam based on super-large head studs, which has a steel beam and a reinforced concrete slab arranged on the steel beam. A number of studs are fixed on the upper surface of the steel beam, and the studs are located inside the reinforced concrete slab to strengthen the connection between the steel beam and the reinforced concrete slab through the studs. In this example, different types of studs are set according to different force conditions in different regions, specifically including:

[0042] In this embodiment, corresponding to the negative moment area of the composite beam, super-large head stud I is used for the studs on the steel beam. The stud shank diameter of the super-large head stud I is less than 10 mm, and the stud head diameter is greater than or equal to 1.8 times its stud shank diameter, preferably 2.2 times or more.

[0043] In this embodiment, corresponding to the positive moment area of the composite beam, super-large head stud II is used for the studs on the steel beam. The stud shank diameter of the super-large head stud II is between 10 mm and 25 mm, and its stud head diameter should not be less than the stud head diameter of the ordinary stud, and it is preferably greater than or equal to 1.2 to 1.3 times the stud head diameter of the ordinary stud.

[0044] The ordinary stud adopts the stud head d k and the stud shank d Nominal diameter and their ratio are:

[0045]

[0046] The nominal diameter of the head of the super-large headed stud II is enlarged by a certain proportion according to the conventional dimensions in the specification. The head diameter enlargement coefficient Scl is taken as 1.1 - 1.5 for analysis, and the load-displacement relationship diagram is obtained. The abscissa is the slip amount, and the ordinate is the ratio of the pull-out load of each head nominal diameter to the nominal diameter of the ordinary stud in the specification. It can be found that the curves with the head nominal diameter of the super-large headed stud enlarged by 1.2 and 1.3 times are relatively close. In this embodiment, the enlargement ratio coefficient of 1.2 times can be taken, that is, the ratio of the head nominal diameter to the shank nominal diameter of the super-large headed stud is 1.9 - 2.2, and the ratio of the head nominal diameter to the shank nominal diameter of all super-large headed studs should not be less than the requirements of the ordinary studs in the specification.

[0047] The shank diameter of the super-large headed stud II in this embodiment d and the head diameter d k are respectively:

[0048]

[0049] According to the Specification for Design of Steel Structures (GB 50017 - 2017), the shear strength when the slip amount is 1 mm is defined as the shear stiffness. k s . Similarly, the shear stiffness-head diameter enlargement coefficient relationship diagram can be obtained. The abscissa is the head diameter enlargement coefficient Scl, and the ordinate is the shear stiffness of each head nominal diameter to the nominal diameter of the ordinary stud in the specification. k s . It can be found that even when the head nominal diameter of the super-large headed stud is enlarged by 1.1 times, its shear stiffness is also greatly improved. Therefore, it is appropriate to take the enlargement ratio coefficient of 1.2 times for the head nominal diameter of the super-large headed stud involved in this embodiment.

[0050] In this embodiment, corresponding to the high shear zone of the composite beam, a number of super-large headed studs III are fixed on the steel beam. The super-large headed studs III are located in the reinforced concrete slab above the steel beam. The diameter of the super-large headed stud III is greater than 25 mm, and its head diameter is greater than or equal to 1.6 times of its shank diameter, preferably 1.9 times or more.

[0051] Due to the application of materials such as ultra-high performance concrete, the thickness of the concrete slab becomes thinner. At this time, the slenderness ratio of the stud usually cannot meet the recommended limit of not less than 4. In actual applications, there are studs with a slenderness ratio less than 4. Therefore, the super-large headed studs involved in this embodiment include two types: conventional with a slenderness ratio not less than 4 and unconventional with a slenderness ratio less than 4.

[0052] In this example, the super-large head stud I with a small diameter is used in the negative moment area of the composite beam to solve the problem of the adverse effect of the stud on the concrete slab; the super-large head stud III with a large diameter is used in the high shear area of the composite beam to solve the problem of the group stud effect caused by the over-dense arrangement of studs, and the super-large head of the super-large head stud II with a normal diameter can improve the anchoring force of the stud in the concrete slab, thereby ensuring that the stud can exert its normal shear strength. In addition to replacing the application scenarios of ordinary studs, it is especially suitable for the situation where modern high-performance concrete is applied to the floor slab or bridge deck slab, resulting in a thinner concrete slab and the slenderness ratio of the stud not meeting the limit of not less than 4.

[0053] In this embodiment, the super-large head stud is made of steel such as ML15 or ML15Al with a tensile strength of not less than 400 MPa in "Cylindrical Head Studs for Arc Stud Welding" (GB / T 10433-2002), or can also be made of steel with a tensile strength of not less than 600 MPa.

[0054] When calculating the uplift bearing capacity of the stud, it is usually assumed that the angle between the concrete failure surface and the horizontal plane is 35° or 45°. The area of the failure surface is taken by projecting downward from the lower surface of the outer edge of the stud head of the stud. It can be seen that increasing the diameter of the stud head of the stud can increase the area of the concrete failure surface, that is, can improve the uplift bearing capacity of the stud. The angle between the concrete failure surface and the horizontal plane is taken as 45°, and the diameter of the failure surface is d k + 2h e , and the area of the effective concrete failure surface S cor can be calculated according to the following formula.

[0055]

[0056] The specific construction steps of the composite beam in this embodiment include the following steps:

[0057] 1. Weld the super-large head stud connectors in the factory. Select studs with a reasonable diameter and weld them to the flange plate at the top of the steel beam through their arc starting points.

[0058] 2. Assembled connection of the steel beam and the vertical member. On-site, connect the flange and web of the steel beam to the vertical member through bolts, welding and other forms to form a reliable force-bearing structure.

[0059] 3. Pour concrete. A steel bar mesh composed of longitudinal in-slab steel bars and transverse in-slab steel bars is arranged in the reinforced concrete slab. After the steel bar mesh is tied in place, pour concrete to form a composite member of the steel beam and the concrete slab.

Claims

1. A composite beam based on oversized head studs, characterized in that: include: Corresponding to the negative bending moment area of ​​the composite beam, a number of oversized head bolts I are fixed on the steel beam, and the oversized head bolts I are located in the reinforced concrete slab above the steel beam. The bolt rod diameter of the oversized head bolts I is less than 10 mm, and the bolt head diameter is greater than or equal to 1.8 times the bolt rod diameter; In the positive bending moment area of ​​the composite beam, a number of oversized head bolts II are fixed on the steel beam. The oversized head bolts II are located in the reinforced concrete slab above the steel beam. The bolt rod diameter of the oversized head bolt II is between 10 mm and 25 mm, and the bolt head diameter is greater than or equal to 1.6 times the bolt rod diameter. Corresponding to the high shear zone of the composite beam, a number of super-large head bolts III are fixed on the steel beam. The super-large head bolts III are located in the reinforced concrete slab above the steel beam. The diameter of the super-large head bolts III is greater than 25 mm, and the bolt head diameter is greater than or equal to 1.6 times the bolt rod diameter.

2. The composite beam based on oversized head studs according to claim 1, characterized in that: The aspect ratio of the super-large head bolts I, II and III is not less than 4 or greater than 2 and less than 4.

3. The composite beam based on oversized head studs according to claim 1, characterized in that: The bolt head diameter of the extra-large head bolt I is 2.2 times or more of the bolt rod diameter.

4. The composite beam based on oversized head studs according to claim 1, characterized in that: The bolt head diameter of the super-large head bolt II is 1.9 to 2.2 times or more of the bolt rod diameter.

5. The composite beam based on oversized head studs according to claim 4, characterized in that: The bolt rod diameter of the super large head bolt II d and bolt head diameter d k They are: When the bolt rod diameter d is 10mm, the bolt head diameter d k 22mm; When the bolt rod diameter d is 13mm, the bolt head diameter d k 26mm; When the bolt rod diameter d is 16mm, the bolt head diameter d k 35.2mm; When the bolt rod diameter d is 19mm, the bolt head diameter d k 38mm; When the bolt rod diameter d is 22mm, the bolt head diameter d k 41.8mm; When the bolt rod diameter d is 25mm, the bolt head diameter d k It is 47.5mm.

6. The composite beam based on oversized head studs according to claim 1, characterized in that: The bolt head diameter of the super-large head bolt III is 1.9 times or more of the bolt rod diameter.

7. The composite beam based on oversized head studs according to claim 1, characterized in that: The oversized head bolt is made of ML15 or ML15Al steel with a tensile strength of not less than 400 MPa, or made of steel with a tensile strength of not less than 600 MPa.

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