Large-span prestressed concrete holed beam frame structure system reinforced by profile steel and stiffening plates and design method of large-span prestressed concrete holed beam frame structure system

Abstract

The invention discloses a large-span prestressed concrete holed beam frame structure system reinforced by profile steel and stiffening plates and a design method of the large-span prestressed concrete holed beam frame structure system. The large-span prestressed concrete holed beam frame structure system comprises a prestressed concrete beam, prestressed tendons, common full-length steel bars, profile steel for reinforcing a hole, upper and lower chord stirrups of the hole and upper and lower chord angle ribs of the hole, stirrups are arranged on the side edges of the hole; and reinforcing inclined ribs are arranged on the side edges of the hole. Wherein the profile steel and the upper and lower chord angle ribs of the hole are mainly used for supplementing the loss of strength and rigidity of concrete caused by hole opening, and the stirrups and the inclined ribs on the side edges of the hole are used for bearing shear force transmission of a concrete beam. By adopting the reinforcing measures to reinforce the hole, the site construction is convenient and quick, the component mounting efficiency is improved, the use amount of reinforcing steel bars can be greatly reduced, the congestion of the reinforcing steel bars in a core area is avoided, the section height of the component can be reduced, the self weight is reduced, and the anti-cracking performance and the bearing capacity of the component are improved, so that the anti-seismic performance of the whole frame structure is improved.

Description

Technical Field

[0001] The invention relates to the technical field of large-span prestressed concrete open-hole beam frame structure system construction, and in particular to a large-span prestressed concrete open-hole beam frame structure system reinforced by steel sections and stiffening plates and a design method thereof. Background Art

[0002] In recent years, the side-type railway passenger station has been widely used in the design of small and medium-sized high-speed railway passenger stations due to its economic efficiency and architectural characteristics. Due to the control of investment and building functions, the two-story side-type passenger station building generally adopts the traditional single-span large-span reinforced concrete frame structure system. The net height of the first-floor ceiling is controlled at about 5.4m, and the net height of the waiting hall is relatively depressed, which affects the comfort of passengers. In order to meet the requirements of passenger comfort, headroom and cost reduction. A large-span prestressed concrete open-hole beam frame structure is proposed to facilitate the passage of equipment pipelines and increase the net height of the building. If the equipment pipeline passes through the hole in the beam, the number of building floors and the volume ratio can be increased under the condition of unchanged total height, carbon emissions can be reduced, and good social and economic benefits can be obtained. In addition, when the number of floors of a building is fixed, reducing the floor height through this measure can reduce the total height of the building accordingly, relatively increase the usable space, reduce the deadweight, and reduce the load effect (including seismic load effect, wind load effect, etc.), thereby reducing the project cost.

[0003] However, opening a hole in the beam destroys the integrity and continuity of the beam, and easily generates stress concentration at the corner of the hole, causing the beam to crack prematurely. When the crack width is too large, it will affect the durability of the beam. The existence of the hole in the web of the beam weakens the strength and stiffness of the beam, and changes the stress mechanism of the beam under static load and earthquake. At the same time, the shear bearing capacity of the beam with a hole decreases significantly, and the deflection increases significantly, especially for large-span prestressed concrete frame structures, the effect is more significant.

[0004] Steel-concrete structure is a composite structure in which steel sections are built into ordinary reinforced concrete structures. Compared with ordinary reinforced structures, when the cross-section of the components is the same, the upper limit of the total amount of reinforcement (including ordinary steel bars and steel sections) of steel-concrete structures is larger, which means higher bearing capacity and stiffness. Compared with steel structures, steel-concrete structures have higher stiffness, good durability and fire resistance, and can save a lot of money in terms of steel usage, corrosion protection and fire prevention of steel structures. At present, steel-concrete column components have been widely used in general multi-story and high-rise building structures, while SRC beam components are mainly used in large-span, heavy-load structures, such as industrial plants, large stadiums, exhibition halls, bridges, and conversion structures of high-rise buildings.

[0005] Applying steel-concrete to the upper and lower chords of the opening can, on the one hand, compensate for the weakening of strength and stiffness caused by the opening, and on the other hand, save the amount of steel bars, avoid steel bar crowding, and improve construction quality. Therefore, it is possible to apply steel-concrete to the opening. By using steel to reinforce the opening of the large-span prestressed concrete opening beam frame structure, a design method is provided to further promote the application of the large-span prestressed concrete opening beam frame structure in areas with different seismic resistance levels, so as to reduce the load effect (including seismic load effect, wind load effect, etc.), thereby reducing the project cost and obtaining more significant economic and social benefits. Summary of the invention

[0006] The purpose of the present invention is to address the deficiencies of the prior art and combine the excellent performance of steel-concrete to propose a large-span prestressed concrete open-hole beam frame structure system reinforced with steel and stiffening plates and its design method. It combines three traditional structures, namely steel-concrete, prestressed concrete structure and opening diagonal reinforcement structure system, to achieve the purpose of improving the seismic performance of the large-span prestressed concrete open-hole beam frame structure system.

[0007] The advantages of the present invention are mainly reflected in three aspects: steel-concrete, prestressed concrete and diagonal reinforcement of the opening. In terms of force transmission of components, the upper and lower chords of the opening are integrated with the adjacent concrete beams through steel-concrete, thereby improving the seismic performance of the overall frame structure. In terms of the amount of steel bars used, the steel bars of the upper and lower chords of the opening are greatly reduced, which greatly saves the production time of prefabricated components and the on-site installation time, and improves the construction quality. Therefore, the large-span prestressed concrete opening beam frame structure system reinforced by steel sections proposed in the present invention is in line with my country's green development strategy for building industrialization.

[0008] The technical problem solved by the present invention can be achieved by adopting the following technical solutions: A large-span prestressed concrete opening beam frame structure system reinforced by steel sections and stiffening plates and a design method thereof, comprising a prestressed concrete beam, prestressed tendons, common through-length steel bars, steel sections for opening reinforcement, upper and lower chord stirrups of the opening, upper and lower chord angle bars of the opening, strengthening stirrups on the sides of the opening and strengthening diagonal bars on the sides of the opening.

[0009] The concrete beam is provided with prestressed tendons and ordinary through-length steel bars for reinforcing the steel sections of the upper and lower chords of the opening, stirrups of the upper and lower chords of the opening, angle bars of the upper and lower chords of the opening, reinforcing stirrups on the sides of the opening and reinforcing diagonal bars on the sides of the opening.

[0010] The steel section is located at the geometric centroid of the upper and lower chords of the opening, and both ends are anchored in the adjacent complete concrete beam.

[0011] The steel section is fixed by upper and lower chord stirrups of the opening, upper and lower chord angle bars of the opening and reinforced oblique bars on the sides of the opening.

[0012] The upper and lower chord angle bars of the opening extend out of the opening area and are directly anchored to the adjacent complete concrete beams.

[0013] The reinforcing oblique ribs on the side of the opening pass through the upper and lower chords of the opening and are bent in the area on the side of the opening.

[0014] The prestressed concrete beams also include fully prefabricated prestressed concrete beams; the bonded prestressed tendons include straight line, broken line, and curved prestressed tendons.

[0015] The bonded prestressed tendons may be bonded, bonded or partially bonded, unbonded or unbonded within the opening area.

[0016] The prestressed tendons are constructed using a post-tensioning construction method.

[0017] Before the reinforcement of the steel-concrete, prestressed concrete and diagonal reinforcement of the opening, construction verification is carried out according to the force transmission mode suitable for ordinary concrete beams. After the concrete beams and the upper and lower chords of the openings are cast, the concrete strength of the concrete beams and the upper and lower chords of the openings reaches the design requirements, and the bonded prestressed tendons are tensioned. After the tensioning is completed, the construction stage verification is carried out according to the unbonded frame beams; in the normal use limit state, the calculation is carried out according to the effective prestress, in the ultimate bearing limit state, the stress increment of the unbonded tendons is considered, and under seismic loads, the recovery performance provided by the unbonded tendons is considered.

[0018] Furthermore, the steel-reinforced large-span prestressed concrete opening beam frame structure system is composed of three traditional structures: steel-reinforced concrete and prestressed concrete structures and an opening diagonal reinforcement structure system.

[0019] Furthermore, the steel bars of ordinary reinforced concrete beams (except the opening area) are tied according to the construction drawings. The stirrups are divided into a reinforced area and a non-reinforced area, and the reinforcement is arranged according to the design requirements. Furthermore, the reinforcing stirrups on the side of the opening, the angle bars of the upper and lower chords of the opening, and the stirrups of the upper and lower chords of the opening are tied at the corresponding positions. The reinforcement design is designed and verified in accordance with the corresponding specifications.

[0020] Furthermore, the steel sections are placed in the upper and lower chords of the opening and are fixed by stirrups of the upper and lower chords of the opening, angle bars of the upper and lower chords of the opening and reinforcing diagonal bars on the sides of the opening.

[0021] Furthermore, the prestressed tendons are arranged in the concrete beam component, pass through the lower chord of the opening and extend out of the concrete beam at both ends, and are respectively fixed with clamps and anchors at both ends.

[0022] Next, pour the concrete, paying special attention to the vibration of the opening area.

[0023] A large-span prestressed concrete open-hole beam frame structure system reinforced with steel sections and stiffening plates and a design method thereof, comprising the following steps: Step 1: Tie up the steel cages of concrete columns and concrete beams (except the opening area); the upper and lower chord stirrups in the opening area, the stirrups on the sides of the opening, and the reinforced diagonal bars on the sides of the opening should be placed in the opening area in advance.

[0024] Step 2: Tie the stirrups on the sides of the opening.

[0025] Step 3: Place the steel section at the geometric center of the upper and lower chords of the opening and fix it temporarily.

[0026] Step 4: Insert the reinforcing diagonal bars on the side of the opening and the angle bars on the upper and lower chords of the opening into the stirrups on the upper and lower chords of the opening.

[0027] Step 5: Tie the reinforcing diagonal bars on the side of the opening, and the angle bars and stirrups of the upper and lower chords of the opening in corresponding positions.

[0028] Step 6: Adjust the position of each steel bar, and fix the position of the steel section through the upper and lower chords of the opening, the stirrups of the upper and lower chords of the opening, the angle bars of the upper and lower chords of the opening, and the reinforcing diagonal bars on the sides of the opening.

[0029] Step 7: Pass the prestressed steel strands through the opening area through the lower chord of the opening, leaving anchor plates and spiral stirrups at both ends.

[0030] Step 8: Cast the beams and columns of the frame structure, and make sure the opening area is vibrated and compacted.

[0031] Step 9: When the concrete reaches the corresponding strength, the prestressed tendons are tensioned.

[0032] Step 10: Repeat the above manufacturing process to complete the large-span prestressed concrete open-hole beam frame structure system reinforced with steel sections.

[0033] Compared with the prior art, the advantages of the present invention are: 1. The invention combines a post-tensioned bonded prestressed concrete open-hole beam frame structure and a steel-concrete structure together, and utilizes the advantages of the steel-concrete structure, such as convenient and fast construction, good construction quality, energy saving and environmental protection, while combining the advantages of the post-tensioned bonded prestressed structure, which can improve the structural performance, reduce the cross-sectional height of the component, reduce the deadweight, and improve the crack resistance and self-recovery of the component, thereby improving the seismic performance of the overall frame structure.

[0034] 2. The present invention adopts steel-shaped concrete and applies it in the opening area, which can realize the reliable connection between the upper and lower chords of the opening and the complete concrete beam, which can not only improve the bearing capacity and seismic performance of the opening area, but also greatly reduce the steel bars and significantly reduce the amount of stirrups in the opening area, thereby avoiding the congestion of steel bars in the opening area and greatly improving the production, transportation and installation efficiency and construction quality of prefabricated beam and column components. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the structure of the long-span prestressed concrete open-hole beam frame structure system reinforced by the steel section of the present invention Figure 2 Front view of the opening reinforcement of the large-span prestressed concrete opening beam frame structure system reinforced by the steel section of the present invention Figure 3 A side cross-sectional view of the opening reinforcement of the large-span prestressed concrete opening beam frame structure system reinforced by the steel section of the present invention The corresponding relationship between the reference numerals and the components is as follows: stress concrete beam (1), ordinary continuous steel bars (2), upper and lower chord angle bars of the opening (3), prestressed bars (4), reinforcing stirrups on the sides of the opening (5), upper and lower chord stirrups of the opening (6), reinforcing diagonal bars on the sides of the opening (7), and steel sections (8) for reinforcing the opening. Implementation

[0036] In order to make the features, purposes and advantages of the present invention easier to understand, the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0037] like Figure 1-3 As shown, a steel-reinforced large-span prestressed concrete opening beam frame structure system according to the present invention comprises a prestressed concrete beam (1), prestressed tendons (4), ordinary through-length steel bars (2), steel (8) for reinforcing the opening, upper and lower chord stirrups (6) of the opening, upper and lower chord angle bars (3) of the opening, reinforced stirrups (5) on the sides of the opening, and reinforced diagonal bars (7) on the sides of the opening.

[0038] The concrete beam is provided with prestressed bars (4), ordinary through-length steel bars (2), section steel (8), upper and lower chord stirrups (6) at the opening, upper and lower chord angle bars (3) at the opening, reinforced stirrups (5) at the sides of the opening, and reinforced diagonal bars (7) at the sides of the opening.

[0039] The steel section (8) is located at the geometric centroid of the upper and lower chords of the opening, and the selection of the steel section is designed according to demand.

[0040] The steel section (8) is placed inside the upper and lower chord stirrups (6) of the opening. The steel section (8) is fixed by the upper and lower chord angle bars (3) of the opening and the reinforcing diagonal bars (7) on the side of the opening.

[0041] The upper and lower chord angle bars (3) of the opening extend out of the opening area and are directly anchored to the complete concrete beam next to it. The design of the upper and lower chord angle bars (3) of the opening and the anchor length are designed as required.

[0042] The strengthening oblique ribs (7) on the side of the hole are placed in the upper and lower chords of the hole, and need to be bent in the area on the side of the hole. The strengthening oblique ribs (7) on the side of the hole are in the shape of a "J". The design of the strengthening oblique ribs (7) on the side of the hole is designed as needed.

[0043] The prestressed concrete beam (1) also includes a fully prefabricated prestressed concrete beam and a cast-in-place concrete beam.

[0044] The bonded prestressed tendons (4) include straight line, broken line, and curved line prestressed tendons.

[0045] The bonded prestressed tendons (4) can be bonded, bonded or partially bonded, or unbonded or unbonded in the opening area.

[0046] The prestressed tendons (4) are constructed using a post-tensioning construction method.

[0047] Before the reinforcement of the steel-concrete, prestressed concrete and diagonal reinforcement of the opening, construction verification is performed according to the force transmission mode suitable for ordinary concrete beams. After the concrete beams and the upper and lower chords of the opening are cast, the concrete strength of the concrete beams and the upper and lower chords of the opening reaches the design requirements, and the bonded prestressed tendons (4) are tensioned. After the tensioning is completed, the construction stage verification is performed according to the unbonded frame beam; in the normal use limit state, the calculation is performed according to the effective prestress, in the ultimate bearing limit state, the stress increment of the unbonded tendons is considered, and under the earthquake load, the recovery performance provided by the unbonded tendons is considered.

[0048] The steel bars of the ordinary reinforced concrete beam (except the opening area) are tied according to the construction drawings. The stirrups are divided into a reinforced area and a non-reinforced area. The reinforcement is arranged according to the design requirements. The reinforcing stirrups (5) on the side of the opening, the angle bars (3) on the upper and lower chords of the opening, and the stirrups (6) on the upper and lower chords of the opening are tied at corresponding positions. The reinforcement design is designed and verified according to the corresponding specifications.

[0049] The steel section (8) is placed in the upper and lower chords of the opening and is fixed by the upper and lower chord stirrups (6), the upper and lower chord angle bars (3) and the strengthening diagonal bars (7) on the sides of the opening.

[0050] The prestressed tendons (4) are arranged in the concrete beam component, pass through the lower chord of the opening and extend out of the concrete beam at both ends, and are respectively fixed with clamps and anchors at both ends.

[0051] Next, pour the concrete, paying special attention to the vibration of the opening area.

[0052] A steel reinforced long-span prestressed concrete open-hole beam frame structure system, characterized by comprising the following steps: Step 1: The steel bars of the columns and beams (except the opening area) of the prestressed concrete frame are designed and tied in accordance with the normal prestressed concrete frame. For the convenience of subsequent construction, the upper and lower chord stirrups (6) of the opening area, the stirrups (5) on the sides of the opening, and the strengthening diagonal bars (7) on the sides of the opening should be placed in the opening area in advance.

[0053] Step 2: Tie the stirrups (5) on the side of the opening at a reasonable position according to the construction drawings. When designing the stirrups (5) on the side of the opening, the steel section (8) needs to be considered to avoid conflicts between the stirrups (5) and the steel section (8).

[0054] Step 3: For the convenience of subsequent construction, it is necessary to temporarily place the steel section (8) into the upper and lower chords of the opening, pass through the upper and lower chord stirrups (6) of the opening, and temporarily fix it through the upper and lower chord stirrups (6), the upper and lower chord angle bars (3) of the opening, and the reinforcing diagonal bars (7) on the side of the opening.

[0055] Step 4: The strengthening diagonal bars (7) on the side of the opening must first be inserted into the stirrups (6) of the upper and lower chords of the opening and temporarily fixed. At the same time, the angle bars (3) of the upper and lower chords of the opening must be inserted into the stirrups (6) of the upper and lower chords of the opening and temporarily fixed.

[0056] Step 5: According to the construction drawings, tie the diagonal reinforcement bars (7) on the side of the opening, the angle bars (3) of the upper and lower chords of the opening, and the upper and lower chord stirrups (6) at the corresponding reasonable positions. First, the upper and lower chord stirrups (6) should be tied and fixed. Secondly, the diagonal reinforcement bars (7) on the side of the opening are fixed on the diagonal reinforcement bars (7) on the side of the opening and the upper and lower chord stirrups (6). Finally, the angle bars (3) of the upper and lower chords of the opening should be placed at the corners of the upper and lower chord stirrups (6) (excluding the corners of the full-length steel bars).

[0057] Step 6: Check the upper and lower chord stirrups (6), the upper and lower chord angle bars (3) and the side reinforcement diagonal bars (7) of the opening according to the construction drawings. The steel section (8) should be placed at the geometric center of the upper and lower chords of the two openings, and the position of the steel section (8) should be fixed by the upper and lower chords, the upper and lower chord stirrups (6), the upper and lower chord angle bars (3) and the side reinforcement diagonal bars (7) of the opening.

[0058] Step 7: Pass the prestressed tendons (4) through the lower chord of the opening and fix the line shape of the prestressed tendons (4) according to the construction drawings. Anchor plates and spiral stirrups are left at both ends of the prestressed concrete to tension the prestressed tendons (4).

[0059] Step 8: When pouring the prestressed concrete frame, the frame columns should be poured first. Secondly, pour the concrete within the height range of the lower chord beam in the opening and the area near the opening, and use a concrete vibrator to vibrate obliquely. Finally, pour the concrete in the opening area and the concrete in other parts of the prestressed concrete beam. Pay attention to ensure that the opening area is vibrated and compacted.

[0060] Step 9: Before applying prestress to the prestressed tendons (4), the appearance and dimensions of the components shall be checked. Tensioning can only be carried out when the appearance and dimensions of the components meet the quality standard requirements. During tensioning, the concrete strength of the components shall meet the design requirements. If not specified in the design, the concrete strength shall not be less than 75% of the design strength grade value.

[0061] Step 10: Repeat the above manufacturing process to complete the large-span prestressed concrete open-hole beam frame structure system reinforced with steel sections.

[0062] The above is merely an exemplary description of the present invention. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method, that is, the description is not restrictive. Without departing from the method concept and technical solution of the present invention, the present invention can be easily improved, changed or replaced in various ways, and these improvements and changes all belong to the protection scope of the present invention.

Claims

1. A large-span prestressed concrete opening beam frame structure system reinforced with steel sections and stiffening plates and a design method thereof, comprising a prestressed concrete beam (1), prestressed tendons (4), ordinary through-length steel bars (2), steel sections (8) for opening reinforcement, upper and lower chord stirrups (6) of the opening, upper and lower chord angle bars (3) of the opening, strengthening stirrups (5) on the sides of the opening, and strengthening diagonal bars (7) on the sides of the opening; It is characterized in that The upper and lower chords of the opening of the prestressed concrete beam (1) are provided with opening reinforcement steel (8), opening upper and lower chord stirrups (6), opening upper and lower chord angle bars (3), prestressed bars (4) and ordinary through-length steel bars (2). The opening side of the prestressed concrete beam (1) is provided with opening side reinforcement stirrups (5) and opening side reinforcement diagonal bars (7). The opening reinforcement steel (8) is fixed by the opening upper and lower chord stirrups (6), opening upper and lower chord angle bars (3) and opening side reinforcement diagonal bars (7). The prestressed concrete beam (1) also includes a fully prefabricated prestressed concrete beam; the prestressed tendons (4) include straight line, broken line, and curved line prestressed tendons. The prestressed tendons are constructed using a post-tensioning construction method. The prestressed tendons (4) in the prestressed concrete beam (1) can be bonded, partially bonded, unbonded, or unbonded; when the concrete strength reaches the design requirements, the prestressed tendons (4) are tensioned, and after the tensioning is completed, the support is removed.

2. A large-span prestressed concrete open-hole beam frame structure system reinforced with steel sections and stiffening plates and a design method thereof according to claim 1, characterized in that: The structural system comprises a prestressed concrete beam (1), prestressed tendons (4), ordinary through-length steel bars (2), steel sections (8) for reinforcing the opening, upper and lower chord stirrups (6) of the opening, upper and lower chord angle bars (3) of the opening, reinforcing stirrups (5) on the sides of the opening, and reinforcing diagonal bars (7) on the sides of the opening.

3. The prestressed tendon (4) according to claim 1, characterized in that: The linearity of the prestressed tendons must meet the requirements of the prestressed concrete beam (1) and avoid the opening area. Specifically, the distance between the prestressed tendons and the opening must be at least 1 times the beam height.

4. The steel section (8) according to claim 1, characterized in that: The steel section is in an I-shape, and the design of the steel section needs to meet corresponding design specifications. The steel section (8) is fixed by upper and lower chord stirrups (6) at the opening, upper and lower chord angle bars (3) at the opening, and reinforced diagonal bars (7) at the side of the opening.

5. The upper and lower chord reinforcement measures for the opening according to claim 1 are characterized in that: The reinforcement structure comprises upper and lower chord stirrups (6) at the opening and upper and lower chord angle bars (3) at the opening. The upper and lower stirrups (6) of the opening are in a U shape. The upper and lower stirrups (6) of the opening are arranged according to design requirements. The upper and lower chord angle bars (3) of the opening are arranged according to design requirements.

6. The stirrups (5) at the side of the opening according to claim 1, characterized in that: The cross-section of the stirrups in the opening area is larger than that of ordinary stirrups. Secondly, the shape of the stirrups should facilitate the passage of the steel sections. The spacing of the stirrups (5) on the sides of the opening is arranged according to design requirements.

7. The strengthening diagonal rib (7) at the side of the hole according to claim 1, characterized in that: The reinforcing oblique ribs (7) on the side of the hole are in the shape of a "X". As mentioned above, the position of the reinforcing diagonal ribs (7) on the side of the hole needs to pass through the area on the side of the hole.

8. The hole size according to claim 1, characterized in that: The opening is located at the geometric center of the concrete section.

9. Design method of prestressed concrete opening beam: Use steel bars to reinforce the opening area, mainly including upper and lower chord stirrups, upper and lower chord longitudinal bars, opening side stirrups and opening side diagonal bars, as shown in Figure 2. The specific design method is as follows (1) Section control conditions The compression chord and the tension chord (usually the upper and lower chords) should meet the following requirements: in, V c and V t They are V=V c +V t +0.05N p0 (2a) V c =β(V c +V t ) (2b) V t =1.2(V c +V t )-V c (2c) Among them, V c and V t are the shear forces borne by the compression and tension chords, V is the shear design value at the center section of the opening, b is the beam width, h0 c and h0 t are the effective heights of the compression and tension chord sections, respectively, and f c is the design value of concrete axial compressive strength, β is the shear force distribution coefficient (taken as 0.9), N p0 It is the prestress when the normal prestress of concrete is equal to 0. (2) Side stirrups at the opening The side stirrups of the opening should meet the following requirements: A v ≥0.54(V1-0.05N p0 ) / f yv (3) The side diagonal reinforcement of the opening should meet the following requirements: Among them, the larger shear design value at the edge section of the opening, A v and A d are the cross-sectional areas of the stirrups and diagonal bars on the side of the opening, respectively, and f yv and f yd are the design values ​​of tensile strength of stirrups and diagonal bars on the side of the opening, respectively; α is the angle between the diagonal bars on the side of the opening and the horizontal line. (3) Upper and lower stirrups The upper and lower stirrups of the opening should meet the following requirements: Among them, A sv c and A sv t are the total cross-sectional areas of the stirrups at the compression and tension chords at the opening, respectively. t is the design value of concrete axial tensile strength, N c and N t are the axial pressure and axial tension of the compression and tension chords, respectively, s c and t are the stirrup spacings of the compression and tension chords, respectively, and A s1 , A s2 , A s3 , A s4 are the cross-sectional areas of the longitudinal reinforcement of the compression and tension chords, respectively, l h is the length of the hole, h c 、h h 、h t is the height of the compression chord, opening, and tension chord, λ c and λ t is the shear span ratio of the compression and tension chords. When A is calculated according to formula (6) sv t The calculated V t Less than f yv A sv t h0 t / s t When V t =f yv A sv t h0 t / s t (≥0.36bh0 t f t ). (4) Longitudinal reinforcement of upper and lower chords at the opening The compression chord is a symmetrically reinforced eccentrically compressed member. b When , the compression chord is in a state of large eccentric compression. Therefore, the longitudinal reinforcement A in the compression chord s2 It can be calculated by formula (9). Among them, ξ is the relative height of the compression zone, b is the height of the relative limit compression zone, e is the distance from the axial force action point to the tensile reinforcement, e a is the additional eccentricity, a′ and a are the distances from the resultant force points of the longitudinal reinforcement in the compression zone and the tension zone to the edge of the section, respectively. The tension chord is an asymmetric eccentric tension member. Therefore, A s3 and A s4 It can be calculated by equations (10) to (15). At this time, the eccentric tension member is divided into a large eccentric tension member and a small eccentric tension member. When the axial force N t The action is now the tension string A s3 and A s4 When the cross section is between 1 and 2, it is a case of small eccentric tension, and the internal force of the cross section is taken as N t and M t1 , the corresponding A s3 for M t1 =0.25V t l h (10) Correspondingly, the internal force of the section is taken as N t and M t2 , the corresponding A s4 for I t2 =0.75V t l h (12) When the axial force N t Acting on the tension chord A s3 and A s4 When the eccentric tension is large, A s3 and A s4 for Where x is the height of the concrete compression zone (2a′≤x≤ξ b h0 t ), f y ′ and f y are the design values ​​of tensile strength of longitudinal reinforcement in compression zone and tension zone respectively, and e′ is the distance from the axial force application point to the farther longitudinal reinforcement. When the above calculated A s4 When it is smaller than the bottom tension longitudinal reinforcement of the beam without opening, the bottom tension longitudinal reinforcement without opening is used to replace A. s4 .

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