Structural design method for crack control in negative moment zone and overall linear shape of continuous composite beams

Abstract

The present invention is a structural design method for controlling cracks in the negative moment area and the overall linear shape of a continuous composite beam, and the specific steps are: according to the production capacity of steel plate beams or steel sections, the continuous composite beam application scenario load and load combination, the positive moment area and negative moment area of ​​the continuous composite beam are drawn; the continuous composite beam adopts densely distributed I-beams as the structural main beams over the entire length; the lateral spacing between the structural main beams is determined and connected; the concrete bridge decks in the positive and negative moment areas above the structural main beams are arranged in a classified manner: the concrete bridge decks are laid in the positive moment area of ​​the continuous composite beams, and are connected to the structural main beams with cylindrical head welds; the concrete bridge decks are laid in the negative moment area of ​​the continuous composite beams, and are not connected to the structural main beams; and prestressed steel bars are laid and tensioned. The present invention cancels the connection between the structural main beams and the concrete bridge decks in the negative moment area, which can effectively avoid the occurrence of cracks in the concrete bridge decks in the negative moment area of ​​the continuous composite beams, improve the overall linear shape of the continuous composite beams, and achieve beneficial mechanical and economic effects.

Description

Technical Field

[0001] The invention relates to the technical field of engineering structure optimization design, and in particular to a structural design method for controlling cracks in a negative moment zone of a continuous composite beam and overall linear shape. Background Art

[0002] Continuous composite beams are widely used in structural engineering fields such as industrial and civil buildings. Under the combination of dead load, live load and the most unfavorable load, continuous composite beams will form two areas: positive bending moment (tension at the bottom of the beam) and negative bending moment (tension at the top of the beam). The beam length range corresponding to the positive bending moment is larger than the beam length range corresponding to the negative bending moment. Therefore, when designing continuous composite beams, engineers generally complete the entire cross-section design of the beam based on the positive bending moment area. This beam cross-section design based on positive bending moment will lead to unreasonable force on the beam in the negative moment area. For example, when using the steel-concrete composite beam cross-section design, the concrete is often arranged above the cross-section, and the steel structure is arranged below the cross-section, and they are connected to each other by bolts. This layout is conducive to the force and load layout and contact in the positive moment area, but not conducive to the force of the negative moment. For example, when the application environment is a civil air defense structure or a parking lot structure, the concrete in the negative moment area is in a tensile state, and the shrinkage creep and temperature effects are superimposed. Unfavorable phenomena such as concrete cracking in the negative moment area and linear deflection of the continuous composite beam are more common.

[0003] In recent years, although some people have adopted process optimization measures such as high-performance concrete and pull-out but not shear-resistant structures, the idea is still mainly based on "resistance", resulting in poor anti-cracking effect and uncontrollable deflection line shape under long-term load.

[0004] For example:

[0005] Sun Zonglei, Ai Zongliang, Zhang Yuhan. Research on durability improvement technology of steel-concrete continuous composite beams in negative moment zone[J]. Journal of Railway Engineering Society, 2022, 39(12): 54-59.

[0006] Nie Jianguo, Li Yixin, Tao Muxuan, et al. Experiment on the pull-out performance of a new type of pull-out but non-shear connector[J]. China Journal of Highway and Transport, 2014, 27(4): 38-45. Summary of the invention

[0007] The present invention aims to solve the deficiencies of the prior art and provides a structural design method for controlling cracks in the negative moment zone of a continuous composite beam and the overall linear shape.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The structural design method for cracks in the negative moment zone of continuous composite beams and overall linear control includes the following specific steps:

[0010] S1. Draw the positive moment area and negative moment area of ​​the continuous composite beam according to the production capacity of steel plate beams or steel sections, the application scenario load and load combination of the continuous composite beam:

[0011] The single span of the continuous composite beam is 20-40m. The main structural beam is made of I-shaped steel plate beams and H-shaped rolled steel with a height of 1.2m-1.7m. The upper and lower flange plates are of equal width and thickness, with a maximum plate width of 0.5m. The flange plate thickness is within 50mm, and 1.0 times the web thickness ≤ flange thickness ≤ 1.9 times the web thickness; the concrete bridge deck is made of C45 or above grade concrete;

[0012] Select the specified live load to perform load combination and internal force calculation, and draw the positive moment area and negative moment area of ​​the continuous composite beam;

[0013] S2. The entire length of the continuous composite beam uses densely packed I-beams as the main structural beam:

[0014] The spacing of the main beams is 1.3-1.5 times the height of the main beam web to achieve dense distribution;

[0015] S3. Determination and connection of transverse spacing between structural main beams:

[0016] I-shaped steel beams are laid transversely between the main beams of the structure. The spacing between the beams is 3.5-5 times the spacing of the main beams of the structure. The transverse connection is achieved through high-strength bolt double-sided symmetrical joints.

[0017] S4. Classification and layout of concrete bridge decks in the positive and negative moment areas above the main beams:

[0018] The concrete bridge deck is laid in the positive bending moment area of ​​the continuous composite beam, and the concrete bridge deck in the positive bending moment area is connected to the main beam of the structure by cylindrical head welds; the concrete bridge deck is laid in the negative bending moment area of ​​the continuous composite beam, and the concrete bridge deck in the negative bending moment area is not connected to the main beam of the structure; prestressed steel bars are laid and tensioned.

[0019] The beneficial effects of the present invention are as follows: the present invention eliminates the connection between the structural main beam and the concrete bridge deck in the negative bending moment area, which can effectively avoid the occurrence of cracks in the concrete bridge deck in the negative bending moment area of ​​the continuous composite beam, improve the overall linear shape of the continuous composite beam, and achieve beneficial mechanical and economic effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of positive moment region and negative moment region of the continuous composite beam in specific embodiment 1;

[0021] Figure 2 This is a schematic diagram of the cross beams used to transversely connect the main beams of the structure in the specific embodiment 1;

[0022] Figure 3This is a schematic diagram of a double-sided symmetrical joint connection using high-strength bolts for transverse connection in specific embodiment 1;

[0023] 1- positive bending moment area; 2- negative bending moment area; 3- structural main beam; 4- concrete bridge deck; 5- cross beam; 6- high-strength bolt double-sided symmetrical joint;

[0024] The following is a detailed description of the embodiments of the present invention with reference to the accompanying drawings. DETAILED DESCRIPTION

[0025] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The embodiments are only used to explain the present invention and are not used to limit the scope of the present invention. The present invention is described in more detail by way of example with reference to the accompanying drawings in the following paragraphs. The advantages and features of the present invention will become clearer according to the following description. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0027] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0028] The structural design method for cracks in the negative moment zone of continuous composite beams and overall linear control includes the following specific steps:

[0029] S1. According to the production capacity of steel plate beams or steel sections, the application scenario load and load combination of continuous composite beams, draw the positive moment area 1 and negative moment area 2 of the continuous composite beam:

[0030] The single span of the continuous composite beam is 20-40m. The main structural beam 3 is made of I-shaped steel plate beams and H-shaped rolled steel with a height of 1.2m-1.7m. The upper and lower flange plates are of equal width and thickness, with a maximum plate width of 0.5m. The flange plate thickness is within 50mm, and 1.0 times the web thickness ≤ flange thickness ≤ 1.9 times the web thickness; the concrete bridge deck 4 is made of C45 or higher grade concrete;

[0031] Select the specified live load to perform load combination and internal force calculation, and draw the positive moment area 1 and negative moment area 2 of the continuous composite beam;

[0032] S2. The entire length of the continuous composite beam uses densely packed I-beams as the main structural beam 3:

[0033] The spacing of the structural main beams 3 is 1.3-1.5 times the main beam web height to achieve dense distribution;

[0034] S3. Determination and connection of transverse spacing between structural main beams 3:

[0035] I-shaped steel is horizontally arranged between the main structural beams 3 as cross beams 5, and the spacing between the cross beams 5 is 3.5-5 times the spacing of the main structural beams 3, and the cross beams 5 are horizontally connected by high-strength bolt double-sided symmetrical joints 6;

[0036] S4. Classification and layout of concrete bridge deck 4 in positive bending moment area 1 and negative bending moment area 2 above structural main beam 3:

[0037] A concrete bridge deck 4 is laid in the positive bending moment area 1 of the continuous composite beam, and the concrete bridge deck 4 in the positive bending moment area 1 is connected to the structural main beam 3 by cylindrical head welds; a concrete bridge deck 4 is laid in the negative bending moment area 2 of the continuous composite beam, and the concrete bridge deck 4 in the negative bending moment area 2 is not connected to the structural main beam 3; prestressed steel bars are laid and tensioned. Specific embodiment 1:

[0039] A bridge adopts a three-span continuous composite beam structure with a span of 32.5+40+32.5m, a bridge width of 16.75m, and a load level of City-A. The structural design that can achieve crack control and overall linear control in the negative moment area 2 of this continuous composite beam is required.

[0040] Step 1: Draw the positive moment area 1 and negative moment area 2 of the continuous composite beam according to the steel production capacity, the application scenario load and load combination of the continuous composite beam.

[0041] According to market research, the main beam 3 of the bridge structure is a welded I-beam with a beam height of 1600mm, a flange width of 500mm, a web thickness of 22mm, an upper flange thickness of 36mm, and a lower flange thickness of 36mm. The bulk density of the steel is 78kN / m 3 Calculation: Bridge deck concrete 4 uses C50 concrete with a bulk density of 26kN / m 3 Calculation; After the combination of the dead load calculation and the city-A load calculation, the positive moment area 1 and the negative moment area 2 of the continuous composite beam are drawn, as shown in Figure 1 shown.

[0042] Step 2: The entire length of the continuous composite beam uses densely distributed I-beams as the main structural beam 3.

[0043] Through mechanical calculation, it was determined that 8 structural main beams 3 were arranged within a horizontal range of 16.75m, and the spacing between the structural main beams 3 was 2.1m.

[0044] The main beam web height is 1600mm-36mm-36mm=1528mm, and the spacing of the structural main beam 3 is 2.1m, which is 1.3-1.5 times the main beam web height.

[0045] Step 3: Determine and connect the transverse spacing between the main structural beams 3.

[0046] The transverse connection of the main structural beam 3 is still made of I-shaped steel, which is used as the cross beam 5. The flange width of the cross beam 5 is 250mm, the flange thickness is 10mm, the web thickness is 12mm, and the web height is 550mm. It is connected by a high-strength bolt double-sided symmetrical joint 6. Figure 2 and Figure 3 As shown; the spacing between beams 5 is 8m.

[0047] Step 4: Classified layout of the concrete bridge deck 4 in the positive bending moment area 1 and the negative bending moment area 2 above the main structural beam 3.

[0048] A concrete bridge deck 4 is laid in the positive bending moment area 1 of the continuous composite beam. The concrete bridge deck 4 is connected to the structural main beam 3 by cylindrical head welds to achieve the effect of coordinated deformation and common force. A concrete bridge deck 4 is laid in the negative bending moment area 2 of the continuous composite beam. The concrete bridge deck 4 is not connected to the structural main beam 3. Prestressed steel bars are laid and tensioned to improve the prestressing efficiency and solve the cracking problem of the concrete bridge deck 4 in the negative bending moment area 2. Under the influence of the later shrinkage and creep of concrete, an upward arch effect is formed to improve the overall linear shape of the continuous composite beam.

[0049] The present invention is an optimized design based on the current production process level of steel plate beams and steel sections and the service requirements of building structures. The connection between the structural main beam 3 and the concrete bridge deck 4 in the negative bending moment area 2 is cancelled, which can effectively avoid the occurrence of cracks in the concrete bridge deck 4 in the negative bending moment area 2 of the continuous composite beam, improve the overall linear shape of the continuous composite beam, and achieve beneficial mechanical and economic effects.

[0050] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made using the method concept and technical solution of the present invention, or are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A structural design method for controlling cracks in the negative moment zone of a continuous composite beam and its overall linear shape, characterized in that: The specific steps are: S1. Draw the positive moment area (1) and negative moment area (2) of the continuous composite beam according to the production capacity of steel plate beams or steel sections, the application scenario load and load combination of the continuous composite beam: The single span of the continuous composite beam is 20-40m. The main structural beam (3) is made of I-shaped steel plate beams or H-shaped rolled steel with a height of 1.2m-1.7m. The upper and lower flange plates are of equal width and thickness, with a maximum plate width of 0.5m. The flange plate thickness is within 50mm, and 1.0 times the web thickness ≤ flange thickness ≤ 1.9 times the web thickness. The concrete bridge deck (4) is made of C45 or higher grade concrete. S2. The entire length of the continuous composite beam uses densely packed I-beams as the main structural beam (3): The spacing of the structural main beams (3) is 1.3-1.5 times the height of the main beam webs, so as to achieve dense distribution; S3. Determination of transverse spacing between structural main beams (3) and their connection: I-shaped steels are horizontally arranged between the main structural beams (3) as cross beams (5), the spacing between the cross beams (5) is 3.5-5 times the spacing between the main structural beams (3), and the cross beams (5) are horizontally connected by high-strength bolt double-sided symmetrical joints (6); S4. Classification and layout of the concrete bridge deck (4) in the positive bending moment area (1) and negative bending moment area (2) above the main structural beam (3): A concrete bridge deck (4) is laid in the positive bending moment region (1) of the continuous composite beam, and the concrete bridge deck (4) in the positive bending moment region (1) is connected to the structural main beam (3) by means of cylindrical head welded nails; a concrete bridge deck (4) is laid in the negative bending moment region (2) of the continuous composite beam, and the concrete bridge deck (4) in the negative bending moment region (2) is not connected to the structural main beam (3), and prestressed steel bars are laid and tensioned.

2. The structural design method for controlling cracks in the negative moment zone and overall linear shape of a continuous composite beam according to claim 1, characterized in that: In step S1, a specified live load is selected to perform load combination and internal force calculation, and the positive moment area (1) and negative moment area (2) of the continuous composite beam are drawn.

3. The structural design method for controlling cracks in the negative moment zone and overall linear shape of a continuous composite beam according to claim 2, characterized in that: In step S1, the parameters of the structural main beam (3) and the parameters of the concrete bridge deck (4) are calculated using finite element software and verified experimentally.

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