Construction method of steel concrete composite beam bridge deck slab

Abstract

The invention relates to the technical field of bridge deck slab construction, in particular to a construction method of a steel-concrete composite beam bridge deck slab of an over-crossing expressway bridge. Comprising a bamboo plywood, a longitudinal square timber, an I-shaped steel cross beam, a top support, a steel pipe support, a bottom support and an I-shaped steel bottom cross beam from top to bottom in sequence; a bridge deck slab support system in a steel box girder box chamber sequentially comprises bamboo plywood, longitudinal square timber, an I-shaped steel beam, a top support, a steel pipe support, a bottom support and a box girder bottom plate from top to bottom. The steel box girder flange plate support system sequentially comprises bamboo plywood, longitudinal square timber and I-shaped steel brackets / angle steel from top to bottom. The invention further provides a steel concrete composite beam bridge deck slab construction method, aiming at the complex characteristics of a construction site, lug plates on the two sides of the steel beam are utilized, improved and optimized, a bridge deck slab support system between the steel box beams and a steel box beam flange plate support system are erected on the basis, and therefore concrete pouring is completed under the condition that normal driving on a road is not affected.

Description

Technical Field

[0001] The invention relates to the technical field of bridge deck construction, and in particular to a construction method for a steel-concrete composite beam bridge deck of a bridge spanning an expressway. Background Art

[0002] The steel-concrete composite beam bridge deck integrates steel beams and reinforced concrete bridge decks. The steel beams bear tension and shear forces, while the reinforced concrete bridge deck bears pressure. The two work together through shear connectors. This structure takes advantage of the high strength and good ductility of steel and the strong compressive resistance of concrete. It has high bearing capacity, excellent structural performance and economy, and is widely used in bridge engineering. In traditional construction, steel beams are first prefabricated in the factory, transported to the site, and hoisted into place and fixed with lifting equipment. Then the bridge deck formwork is installed, mostly made of wood or steel materials, supported by brackets. Then the steel bars are processed in the steel bar processing plant, transported to the site and tied into a steel bar skeleton. After that, the concrete is mixed at the mixing station, transported to the site by a mixer truck for pumping and pouring, and vibrated with a vibrating equipment. Finally, maintenance is carried out to ensure the strength of the concrete increases.

[0003] For cast-in-place bridge deck construction without external cantilever steel box girders, it is difficult to set up supports. Traditional support systems are prone to deformation or even collapse under construction loads or external factors (such as strong winds) due to inaccurate force analysis, threatening construction safety and quality.

[0004] The following technical problems exist in the construction of steel-concrete composite beam bridge decks that cross busy highways:

[0005] The upper span project adopts a conventional full-span support system, which has high requirements for the construction site. During the construction of the upper span bridge deck, the national highway must be kept open for normal traffic, which makes the construction difficult.

[0006] There is a large amount of traffic on the highway, and the use of traditional support platforms will occupy the entire two-way lane, which may cause traffic closures and affect urban transportation. Summary of the invention

[0007] The present invention provides a steel-concrete composite beam bridge deck construction method, and the technical problem to be solved is: in view of the complex characteristics of the construction site, the problem of limited construction site, construction difficulties, and impact on transportation is solved, and a bridge deck support system that is safe, efficient, and easy to install and disassemble is realized to meet the normal traffic conditions of ground roads.

[0008] In order to achieve the above-mentioned invention object, the present invention discloses a steel-concrete composite bridge deck construction support system, characterized in that it comprises a first support structure of the bridge deck arranged between steel box girders, a second support structure of the bridge deck arranged in the steel box girder box chamber, and a third support structure arranged on the steel box girder flange plate, wherein the first support structure comprises bamboo plywood, longitudinal square timber, I-beam cross beam, top support, steel pipe support, bottom support and I-beam bottom cross beam arranged in sequence from top to bottom;

[0009] The second support structure includes a bamboo plywood, longitudinal square timbers, I-beam crossbeams, top supports, steel pipe supports, bottom supports, and box girder bottom plates arranged in sequence from top to bottom.

[0010] The third support structure includes a bamboo plywood, longitudinal square timbers, and I-beam brackets arranged in sequence from top to bottom. Angle steels are provided inside the I-beam brackets, and the I-beam brackets are connected to the ear plates on the steel beam webs by bolts.

[0011] Furthermore, in the first support structure, a support crossbeam support is provided. The support crossbeam support includes a vertical ear plate and a steel plate. The vertical ear plate is vertically arranged on the steel beam web, the steel plate is arranged above the vertical ear plate, and diagonal ribs are provided between the steel plate and the vertical ear plate.

[0012] The present invention also discloses a construction method for a steel-concrete composite beam bridge deck, which includes the following steps:

[0013] S1. Support construction

[0014] When constructing the bridge deck support between steel box girders, a fastener-type steel pipe support is used for construction. The support system is, from top to bottom: bamboo plywood, longitudinal square timbers, I-beam crossbeams, top supports, steel pipe supports, bottom supports, and I-beam bottom crossbeams.

[0015] When constructing the bridge deck support inside the steel box girder chamber, a fastener-type steel pipe support is used for construction. The support system is, from top to bottom: bamboo plywood, longitudinal square timbers, I-beam crossbeams, top supports, steel pipe supports, bottom supports, and box girder bottom plates.

[0016] When constructing the support for the steel box girder flange plate, the support system is, from top to bottom: bamboo plywood, longitudinal square timbers, I-beam brackets, and angle steels.

[0017] S2. Formwork installation

[0018] The formwork is comprehensively coated with a release agent before installation, and the connection parts between the formworks are blocked with a foam expander.

[0019] S3. Steel bar binding construction

[0020] The main steel bar connection method is lap welding.

[0021] S4. Embedded part installation

[0022] Embed the embedded parts of components such as bridge deck system guardrails, expansion joints, and traffic engineering, and weld them firmly.

[0023] S5. Bridge deck concrete work

[0024] When pouring concrete, it expands from the mid-span to the supports to reduce the influence of support settlement, and the concrete is poured according to the marked height of the formworks on both sides.

[0025] S6. Concrete curing

[0026] After the concrete is poured, it is covered with geotextile and cured by sprinkling water after the slurry is collected. When the concrete surface is covered with formwork, the formwork should be kept moist during the curing period;

[0027] S7. Formwork removal

[0028] After the top support or wedge block of the support is loosened, the formwork removal work is carried out; the formwork removal follows the principle of first erecting and then removing, and removing the later erected parts first. It is carried out in a cyclic order from the mid-span to the support direction; when removing the side formwork, it can be removed only after the concrete strength can ensure that its surface and edges are not damaged due to formwork removal; first remove the non-load-bearing formwork, and then remove the load-bearing part of the formwork, from top to bottom; when removing the bottom formwork, after the top support and longitudinal and transverse square timbers of the support are removed, gently pry the formwork with a steel bar or tap it gently with a wooden hammer to remove the first piece, and then remove it piece by piece and section by section;

[0029] S8. Steel pipe support removal

[0030] It is carried out in the order of removing the later installed parts first and the earlier installed parts later; the removal of the support should be carried out symmetrically and layer by layer from top to bottom; for the components and reinforcement parts on the same layer, follow the order of first upper then lower, first outer then inner;

[0031] S9. I-beam removal

[0032] After the square timbers, formwork, I-beams, etc. above the cross beam are removed, the I-beam cross beam is removed; the I-beam cross beam is removed one by one from the middle to both ends. First, remove the I-beam longitudinally connecting between the two cross beams, then loosen the bolts, and slowly extract the I-beam cross beam by using a truck crane; repeat the above steps to complete the removal of the I-beam cross beam.

[0033] The beneficial effects of the present invention are as follows: This solution is aimed at the construction of the bridge deck of the steel-concrete composite beam of highway bridges, especially for the construction of the bridge deck of the steel-concrete composite beam of expressways and national and provincial trunk line bridges. The ear plates on the steel beam webs are used as the force points of the support system to set up the support system. It is efficient, safe, with a low consumption of turnover materials. The components can be uniformly processed in the backfield, not restricted by site conditions, with guaranteed bearing capacity and convenient installation and removal; for the over-crossing working environment, compared with the traditional full hall support, it not only ensures the normal passage of vehicles on the road but also ensures the normal construction of the bridge deck, without interrupting the road traffic, and the construction advantages are particularly obvious. Description of the drawings

[0034] Figure 1 It is the plan view of the bridge deck support between the steel box girders of the embodiment of the present invention;

[0035] Figure 2 It is the plan view of the bridge deck support inside the steel box girder of the embodiment of the present invention;

[0036] Figure 3 Plan view of the steel box girder flange bracket for the embodiment of the present invention;

[0037] Figure 4 Structural schematic diagram of the bracket cross beam support for the embodiment of the present invention;

[0038] Figure 5 Cross-sectional layout plan of the bracket;

[0039] Figure 6 Schematic diagram of the characteristic section Figure 1 ;

[0040] Figure 7 Schematic diagram of the characteristic section Figure 2 ;

[0041] Figure 8 Model diagram of I10 I-beam;

[0042] Figure 9 Combined stress envelope diagram of I10 I-beam;

[0043] Figure 10 Shear stress envelope diagram of I10 I-beam;

[0044] Figure 11 Deflection envelope diagram of I10 I-beam

[0045] Figure 12 Reaction force diagram of the I-beam measuring beam;

[0046] Figure 13 is Combined stress envelope diagram of I10 I-beam;

[0047] Figure 14 Shear stress envelope diagram of I10 I-beam;

[0048] Figure 15 Shear stress envelope diagram of I10 I-beam;

[0049] Figure 16 Axial force diagram of the inclined rod of I10 I-beam

[0050] Figure 17 Reaction force diagram of I10 I-beam;

[0051] Figure 18 Combined stress envelope diagram of I10 steel;

[0052] Figure 19 Model diagram of I20a I-beam;

[0053] Figure 20 Model diagram of I10 I-beam;

[0054] Figure 21It is the shear stress envelope diagram of I20a I-beam;

[0055] Figure 22 It is the deformation envelope diagram of I20a I-beam;

[0056] Figure 23 It is the reaction force diagram of I20a I-beam;

[0057] Figure 24 It is the construction process flow chart of the present invention.

[0058] Among them, 1. Bamboo plywood; 2. Longitudinal square timber; 3. I-beam cross beam; 4. Jack; 5. Steel pipe support; 6. Bottom support; 7. I-beam bottom cross beam; 8. Box girder bottom plate; 9. I-beam bracket; 10. Angle steel; 11. Vertical ear plate; 12. Steel plate; 13. Inclined rib. Specific embodiments

[0059] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. The same components are denoted by the same reference numerals.

[0060] It should be noted that the terms "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to the directions in the drawings, and the terms "inner" and "outer" respectively refer to the directions towards or away from the geometric center of a specific component.

[0061] In order to make the content of the present invention more clearly understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0062] Embodiment

[0063] In this embodiment of the high-speed railway overpass project, the starting mileage of the left bridge: K22+220.7~K23+639.7, with a total length of 1419m. The upper structure of the fifth continuous span of the left bridge adopts a steel box composite beam, and the span layout is (29.5 + 40 + 30.5)m; the main beam is composed of four open steel boxes and a concrete bridge deck. The net distance between the steel boxes is 1.1~4.3m, and the width change is realized by changing the distance between the four steel boxes. The height of the box girder is 2000mm. The width of the top plate of the bridge deck is 17.1~24.25m, the thickness is 25~35cm, the cantilever length is 1.2m, and C50 concrete is used. The concrete of the bridge deck is constructed by the cast-in-place construction plan and is poured in two times. The side span and the mid-span mid-span bridge deck are poured first, and the concrete bridge deck in the negative moment area of the pier top is poured after the strength and stiffness of the first-stage bridge deck reach the design values. Shear studs are used to connect the bridge deck and the steel beam.

[0064] A construction support system for a steel-concrete composite bridge deck in this solution includes a first support structure for the bridge deck between steel box girders, a second support structure for the bridge deck inside the steel box girder chambers, and a third support structure for the bridge deck on the flange plates of the steel box girder. The first support structure includes a 15-mm bamboo plywood, 8-cm x 8-cm longitudinal square timbers, I10 I-beam crossbeams, adjustable supports, φ60.3x3.2-mm steel pipe supports, bottom supports, and I-beam bottom crossbeams arranged from top to bottom. Due to the gradually changing spacing between the in-situ concrete slab chambers of the bridge deck, when the spacing between the bottom crossbeam I-beams is < 2 m, I10 I-beams are used; when 2 m ≤ spacing < 3 m, I14 I-beams are used; when 3 m ≤ spacing < 4 m, I16 I-beams are used. The spacing of the square timbers is 20 cm, the longitudinal spacing of the steel pipe supports is 150 cm, the transverse spacing is 60 cm, and the standard step spacing is 50 cm, as Figure 1 ;

[0065] The second support structure includes a 15-mm bamboo plywood, 8-cm x 8-cm longitudinal square timbers, I10 I-beam crossbeams, adjustable supports, φ60.3x3.2-mm steel pipe supports, bottom supports, and the bottom slab of the box girder arranged from top to bottom. The spacing of the square timbers is 20 cm, the longitudinal spacing of the steel pipe supports is 150 cm, the transverse spacing is 60 cm, and the standard step spacing is 50 cm, as Figure 2 ;

[0066] The third support structure includes a 15-mm bamboo plywood, 8-cm x 8-cm longitudinal square timbers, and I10 I-beam brackets arranged from top to bottom. The spacing of the brackets is 150 cm. A 50x32x3 angle steel is provided inside the I-beam brackets. The I-beam brackets and the ear plates on the steel beam webs are connected by bolts, as Figure 3 。

[0067] In the first support structure, a support crossbeam support is provided. The support crossbeam support includes a vertical ear plate and a steel plate. The vertical ear plate is vertically provided on the steel beam web. The steel plate is provided above the vertical ear plate. A diagonal rib is provided between the steel plate and the vertical ear plate. The steel plate is 18×10 cm with a thickness of 2 cm, as Figure 4 。

[0068] In this solution, a construction method for a steel-concrete composite beam bridge deck includes the following steps:

[0069] S1. Support and formwork construction

[0070] S1.1. Support construction

[0071] S1.1.1. Support construction for the bridge deck between steel box girders

[0072] The cast-in-place slab box rooms on the bridge deck are constructed using fastener-style steel pipe supports, and the diversion operation of G105 National Highway is carried out. The support system from top to bottom is as follows: 15mm bamboo plywood, 8cm x 8cm longitudinal square timbers, I10 I-beam crossbeams, top supports, φ60.3 x 3.2mm steel pipe supports, bottom supports, I-beam bottom crossbeams. Since the spacing between the cast-in-place slab box rooms on the bridge deck gradually changes, when the spacing of the bottom crossbeam I-beams is < 2m, I10 I-beams are used; when 2m ≤ spacing < 3m, I14 I-beams are used; when 3m ≤ spacing < 4m, I16 I-beams are used. The spacing of the square timbers is 20cm, the longitudinal spacing of the steel pipe supports is 150cm, the transverse spacing is 60cm, and the standard step spacing is 50cm, as Figure 1 ;

[0073] Among them, vertical ear plates are designed at the web position of the steel girder. To facilitate the erection of the cast-in-place supports, a 2cm-thick 18×10cm steel plate is set above the ear plates, and diagonal ribs are set between the steel plate and the ear plates to serve as the support crossbeam bearing, as Figure 4 , and all steel components are connected by welding, and this part is welded together at the steel structure factory.

[0074] After the steel structure hoisting is completed, the cast-in-place bridge deck supports are installed. The crossbeams are installed according to the dimensions and directly placed on the bearings, and 5cm-high steel retaining blocks are set on both sides for easy installation and removal;

[0075] S1.1.2 Erection of the bridge deck supports in the steel box girder chamber

[0076] The cast-in-place slab box rooms on the bridge deck are constructed using fastener-style steel pipe supports. The support system from top to bottom is as follows: 15mm bamboo plywood, 8cm x 8cm longitudinal square timbers, I10 I-beam crossbeams, top supports, φ60.3 x 3.2mm steel pipe supports, bottom supports, and the bottom slab of the box girder; the spacing of the square timbers is 20cm, the longitudinal spacing of the steel pipe supports is 150cm, the transverse spacing is 60cm, and the standard step spacing is 50cm, as Figure 2 ;

[0077] S1.1.3 Erection of the supports for the flange plates of the steel box girder

[0078] The support system at the flange plate from top to bottom is as follows: 15mm bamboo plywood, 8cm x 8cm longitudinal square timbers, I10 I-beam brackets / 50x32x3 angle steel; the spacing of the brackets is 150cm, as Figure 3 ;

[0079] S1.2 Formwork installation

[0080] S1.2.1 Bottom formwork

[0081] The bottom formwork uses 1.5cm-thick high-strength bamboo plywood. The formwork is fully coated with release agent before installation, and the same variety of release agent is used. The connection parts between the formworks are blocked with foam expanders to prevent leakage of mortar. The formwork splicing joints should be in a straight line vertically and horizontally to avoid misalignment;

[0082] After the bottom formwork is laid, conduct plane lofting, comprehensively measure the longitudinal and transverse elevations of the bottom plate, detect one point every 5m in the longitudinal and transverse directions, and adjust the bottom formwork to the design elevation according to the measurement results; after the elevation of the bottom plate is adjusted, measure the elevation again. If the elevation does not meet the requirements, make a secondary adjustment.

[0083] S1.2.2, Side formwork

[0084] The side formwork uses 1.5cm thick high-strength bamboo plywood. Determine the edge line of the bridge deck bottom plate according to the measurement lofting, draw an ink line on the bottom formwork, and then install the side formwork. After installation, comprehensively detect the elevation and line type; paste foam expander at the joint between the side formwork and the bottom formwork to prevent slurry leakage.

[0085] S2. Steel bar binding construction

[0086] The steel bars use hot-rolled ribbed steel bars with diameters of 12, 16, 20, 22, and 28. The main steel bar connection method is lap welding. The length of the double-sided lap weld is 5D, and the length of the single-sided lap weld is 10D. The weld joint positions are staggered from each other.

[0087] Before steel bar binding, the surveyor first locates and sets out the lines, checks the deviation of the bottom formwork and the bottom elevation. After passing the inspection, clean the bottom formwork, brush the release agent, and then start steel bar installation. The steel bar acceptance deviation table is shown in Table 1;

[0088] Table 1 Steel bar deviation table

[0089]

[0090] S3. Embedded part installation

[0091] Before pouring, check the drawings, embed the embedded parts of components such as the bridge deck railing, expansion joint, and traffic engineering, and weld them firmly to prevent displacement during the concrete pouring process due to the vibration of the concrete vibrator;

[0092] S4. Bridge deck concrete works

[0093] The cast-in-place bridge deck uses C50 concrete. When pouring concrete, strictly control the pouring speed and pouring sequence. The beam body concrete is poured from the mid-span to the supports in the longitudinal direction of the bridge and symmetrically in the transverse direction of the bridge.

[0094] (1) Concrete pouring

[0095] When pouring concrete, expand from the mid-span to the supports to reduce the influence of support settlement.

[0096] In order to control the elevation of the bridge deck, concrete must be poured according to the height marked on the formwork on both sides, and an elevation control point must be set every 2m to ensure that the concrete surface of the main beam is flat and that the longitudinal and transverse slopes of the beam surface meet the requirements.

[0097] (2) Concrete vibration

[0098] The vibrating rod adopts vertical vibration and should be "inserted quickly and pulled out slowly". When the end of the vibrating rod is about to expose the concrete surface, it should be pulled out quickly to avoid creating a cavity. The vibration time for each insertion point is 20 to 30 seconds. When vibrating, the vibrating rod should be slightly twitched up and down, and the flexible shaft should not be bent hard. The effective radius of the vibrating rod is considered to be 300 to 400 mm, and the moving position of the vibrating rod should not be greater than 1.5 times the effective radius of the vibrating rod.

[0099] S5. Concrete curing

[0100] After the concrete is poured, it should be covered with geotextile and watered as soon as possible after the slurry is collected. The surface of the concrete should not be damaged or polluted during the covering. When the concrete surface is covered with a formwork, the formwork should be kept moist during the curing period. Water 4 to 6 times a day within 3 days, and 2 to 3 times a day after 3 days.

[0101] S6, bracket and template removal

[0102] S6.1. When the concrete strength reaches 90%, the support should be removed. The formwork should be removed in the order of erection first and then removal, or removal of the last erection first. It is advisable to remove the formwork in a cyclic manner from the mid-span to the support.

[0103] The support dismantling should be carried out in stages and cycles according to the order of "from the side away from the pier to the center of the pier" and the principle of "symmetry and balance in the longitudinal direction of the bridge and basic synchronization in the transverse direction of the bridge".

[0104] S6.2. Formwork removal

[0105] After the bracket top support or wedge block is loosened, the template can be removed as follows:

[0106] ⑴. The unloading of the bracket should be carried out according to the planned unloading procedure, and it should be unloaded in several sections. The unloading amount should be small at the beginning and gradually increased. It should be unloaded symmetrically and evenly in the longitudinal direction and simultaneously in the transverse direction.

[0107] ⑵、Dismantling of side formwork: It can be removed only after the concrete strength can ensure that its surface and edges are not damaged by removing the formwork. Generally, it should be removed only when the compressive strength of concrete reaches 2.5MPa. First remove the non-load-bearing formwork, then remove the load-bearing formwork, from top to bottom.

[0108] ⑶. Removal of bottom formwork: After the top brackets and longitudinal and transverse square timbers are removed, gently pry the formwork with a steel bar or tap it gently with a wooden hammer to remove the first piece, and then remove it piece by piece and section by section. It is strictly prohibited to let the removed formwork fall freely to the ground;

[0109] S6.3. Removal of steel pipe supports

[0110] The removal of the supports shall be carried out in the order of installing later and removing first, installing first and removing later, and the following safety operation requirements; the removal of the supports shall be carried out symmetrically and layer by layer from top to bottom; for the components and reinforcement members on the same layer, follow the order of first upper then lower, first outside then inside;

[0111] S6.4. Removal of I-beams

[0112] After the square timbers, formwork, I-beams, etc. above the cross beams are removed, the I-beam cross beams shall be removed;

[0113] The I-beam cross beams shall be removed one by one from the middle to both ends. First, remove the I-beams longitudinally connecting between the two cross beams, then loosen the M20 ordinary bolts, and slowly extract the I-beam cross beams with a truck crane; repeat the above steps to complete the removal of the cross beams.

[0114] Load verification

[0115] 1. Temporary support load analysis

[0116] 1.1 Standard value of load

[0117] (1) Self-weight of the framework G1: Take the actual value; (2) Unit weight of concrete: G2: 25.5 kN / m³;

[0118] (3) Formwork load G3: 0.5 kN / m²; (4) Construction personnel and stacking load: Q1: When calculating, q = 2.5 kN / m²;

[0119] (5) Pressure of newly poured concrete on the side formwork is Q2;

[0120] 1.2 Load combination and checking content

[0121] Strength and stability: 1.3×(G1 + G2 + G3) + 1.5×(Q1 + Q3); Bearing capacity and deformation stiffness of horizontal bars: G1 + G2 + G3 + Q1

[0122] Foundation bearing capacity: G1 + G2 + G3 + Q1; Overturning: 0.9×(G1 + G2 + G3) + 1.5×Q3

[0123] 1.3 Calculation method and stress value

[0124] The ultimate limit state method is adopted for checking calculation.

[0125] Design value of steel strength and elastic modulus:

[0126] ① Q235 steel:

[0127] Combined stress: σw = 215 MPa; Axial stress: σ = 215 MPa; Shear stress: τ = 125 MPa; Elastic modulus: E = 206 GPa

[0128] ② Q345 steel:

[0129] Combined stress: σw = 305 MPa; Axial stress: σ = 175 MPa; Shear stress: τ = 125 MPa; Elastic modulus: E = 206 GPa

[0130] ③ Lumber (TC13 - A):

[0131] Combined stress: σw = 13 MPa; Shear stress: τ = 1.5 MPa; Elastic modulus: E = 10 GPa

[0132] ④ Bamboo plywood (values taken according to the safety technical code for building construction formwork A.5.1):

[0133] Combined stress: σw = 15 MPa; Shear stress: τ = 1.8 MPa; Elastic modulus: E = 6000 MPa

[0134] 1.4 Load analysis

[0135] As Figure 5 is the layout diagram of the cross - section of the support, Figure 6 is the schematic diagram of the characteristic section Figure 1 , Figure 7 is the schematic diagram of the characteristic section Figure 2 ;

[0136] The section information table is shown in Table 2,

[0137] Table 2. Section information table

[0138]

[0139] From Table 2, the loads of different sections can be calculated. Taking the A area of the Ⅰ - Ⅰ section as an example: The self - weight of concrete borne by the unit

[0140] area of the bottom formwork is:

[0141] NkA = 25.5 kN / m³ × = 0.954 m² 2 / 4.02 m 6.051 kN / m

[0142] The formwork load is:

[0143] NkA = 0.5 kN / m² × = 4.074 m² / 4.02 m 0.507 kN / m

[0144] The structural importance coefficient is 1.1. For the concrete load and formwork load which are static loads, a coefficient of 1.3 is taken; for the construction personnel and equipment load which is a dynamic load, a coefficient of 1.5 is taken. Then the load N1 in area A of section 1-1 is: NA = 1.1×(1.3×(6.051 + 0.507)) kN / m² + 1.5× = 2.5 kN / m² 213.503 kN / m

[0145] For the load of construction personnel and equipment which is a dynamic load, a coefficient of 1.5 is taken. Then the load N1 in area A of section 1-1 is: NA = 1.1×(1.3×(6.051 + 0.507)) kN / m² + 1.5× = 2.5 kN / m² 213.503 kN / m

[0146] NA = 1.1×(1.3×(6.051 + 0.507)) kN / m² + 1.5× = 2.5 kN / m² 213.503 kN / m

[0147] The loads of different sections are listed in Table 3;

[0148] Table 3. Section Load Table (Unit: kN / m²)

[0149]

[0150] Load N1 is the load used for calculating the formwork strength and stability, and load N2 is the load used for calculating the deformation and bearing capacity of the foundation.

[0151] 2. Force calculation and check of steel pipe support members

[0152] 2.1. Check of 15-mm-thick bamboo plywood

[0153] The wooden formwork uses 15-mm-thick bamboo plywood, and the design value of the flexural strength is 15 MPa, and the design value of the shear strength is 1.8 MPa. The cross-sectional properties of 1-mm-wide bamboo plywood are as follows:

[0154] Cross-sectional area: A = 1×15 = 15 mm²; Elastic modulus: E = 6000 MPa; Flexural modulus: W = bh² / 6 = 1×15² / 6 = 37.5 mm³

[0155] Moment of inertia: I = bh³ / 12 = 1×15³ / 12 = 281.25 mm⁴

[0156] I = bh³ / 12 = 1×15³ / 12 = 281.25 mm⁴

[0157] σ = M / W = q1L1² / 10W ≤ fj; v = 0.6q1L1; τ = 1.5V / A ≤ fjv; ω = 0.677q2L1⁴ / 100EI ≤ CR

[0158] In the formula:

[0159] Σ——Bending stress of formwork; M——Bending moment borne by 1-mm-wide formwork; q1, q2——Uniformly distributed loads borne by 1-mm-wide formwork; L1——Center spacing of longitudinal (transverse) beams of formwork; fj——Design value of flexural strength of formwork; fjv——Design value of shear strength of formwork; ω——Bending deflection of formwork; v——Shear force of formwork; τ——Shear stress of formwork; A——Transverse area of formwork;

[0160] CR——Deflection limit, taking L / 400.

[0161] Taking the formwork calculation under the flange plate of section Ⅰ-Ⅰ (area A) as an example, the spacing of square timbers is 0.2 m:

[0162] σ = 0.001×13.503×200² / (10×37.5) = 1.440 MPa ≤ 15 MPa;

[0163] τ = 1.5×0.6×0.001×13.503×200 / (1×15) = 0.162 MPa ≤ 1.8 MPa;

[0164] ω = 0.677×0.001×9.964×200⁴ / (100×281.25×6000)

[0165] = 0.064 mm ≤ 200 / 400 = 0.5 mm.

[0166] The formwork calculations for different sections are listed in Table 4;

[0167] Table 4. Formwork Calculation Table

[0168]

[0169] Load N1 is the load used for calculating the formwork, and load N2 is the load used for calculating the stiffness

[0170] According to the calculation results, the bending stresses are all less than 15 MPa, the shear stresses are all less than 1.8 MPa, and the deformation values are all less than L / 400. Therefore, the strength and stiffness of the bamboo plywood formwork both meet the requirements.

[0171] 2.2. Check calculation of 8 cm×8 cm square timber longitudinal beams

[0172] The spacing of 8 cm×8 cm square timber longitudinal beams under the cast-in-place bridge deck slab is 20 cm, and they are supported on I 10 steel beam crossbeams and brackets. The spacing of the crossbeams and brackets is 150 cm.

[0173] The calculated loads borne by the 8 cm×8 cm square timber longitudinal beams are shown in Table 5.

[0174] Table 5. Square Timber Load Calculation Table

[0175]

[0176] The load N1 is the load used for calculating the longitudinal and cross beams under the formwork, and the load N2 is the load used for calculating the stiffness. The longitudinal beam load takes the larger value of Q1 and Q2: Q1 = N1×S1; Q2 = N1×L / n, where S1 is the spacing of the square timbers, L is the transverse width of the area, as shown in Table 2;

[0177] σ = M / W = q3L2 / 10W ≤ fw; v = 0.6q3L2; τ = 1.5V / A ≤ fwv; ω = 0.677q4L24 / 100EI ≤ CR

[0178] In the formula:

[0179] σ—the bending stress of the longitudinal (transverse) beam; M—the bending moment borne by the longitudinal (transverse) beam; W—the section modulus of the longitudinal (transverse) beam;

[0180] E—the elastic modulus of the longitudinal (transverse) beam; q3, q4—the uniformly distributed load borne by the longitudinal (transverse) beam;

[0181] L2—the support center spacing under the longitudinal (transverse) beam; fw—the design value of the bending strength of the longitudinal (transverse) beam;

[0182] fwv—the design value of the shear strength of the longitudinal (transverse) beam; ω—the bending deflection of the longitudinal (transverse) beam; v—the shear force of the longitudinal (transverse) beam;

[0183] τ—the shear stress of the longitudinal (transverse) beam; A—the transverse area of the formwork; CR—the deflection limit value, taking L / 400.

[0184] Taking the calculation of the square timbers under the flange plate of the Ⅰ-Ⅰ section (Area A) as an example, the support spacing of the square timbers is 0.6m:

[0185] σ = 2.857×15002 / (10×85333.33) = 7.573MPa ≤ 13 MPa;

[0186] τ = 1.5×0.6×2.857×1500 / (80×80) = 0.603MPa ≤ 1.5 MPa;

[0187] ω = 0.677×2.108×15004 / (100×10000×3413333.33)

[0188] = 2.117mm ≤ 1500 / 400 = 3.75mm.

[0189] The calculations of square timbers with different sections are listed in Table 6;

[0190] Table 6. Calculation results of the 8cm×8cm longitudinal square timbers of the cast-in-place support

[0191]

[0192] From the above calculations, it can be seen that the bending stress is less than 13 MPa, the shear stress is less than 1.5 MPa, the deformation value is less than L / 400, and the setting of 10cm×10cm square timber longitudinal beams meets the bearing capacity requirements.

[0193] 2.3 Check and calculate I-beam and bracket

[0194] The spacing between the I 10 I-beam beams and brackets under the cast-in-place slab of the bridge deck between the boxes and at the cantilever is 150 cm. The loads borne by beams and brackets with different cross sections are shown in Table 7 below;

[0195] Table 7, I 10 I-beam load table

[0196]

[0197] Beam load: P = N × S2

[0198] 1) Between the boxes: I 10 I-beam beams are supported on the steel pipe frame uprights and bear the concentrated force transmitted by the longitudinal timber. According to the calculation of multi-span continuous beams bearing concentrated loads, the I 10 I-beam beam model of the A partition of the Ⅰ-Ⅰ section is established using midas. The calculation is as follows: Figure 8 This is the I10 I-beam model diagram. Figure 9 is the combined stress envelope diagram of I10 I-beam, Figure 10 is the shear stress envelope diagram of I10 I-beam, Figure 11 It is the deformation envelope diagram of I10 I-beam;

[0199] From the above calculation, we can get: From the above calculation, we can get:

[0200] ; ; m), L is the span of the maximum deformation point 900mm;

[0201] From the above calculations, it can be seen that the strength and stiffness of the I-beam bracket in section Ⅰ-ⅠA partition I 10 meet the requirements of the specification.

[0202] 2) Cantilever: The I10 I-beam bracket is supported on the T-shaped platform at the ear plate of the steel beam. The T-shaped platform steel plate and the ear plate are bolted with M20 ordinary bolts. The bracket bears the concentrated force transmitted by the longitudinal square wood. According to the calculation of multi-span continuous beams bearing concentrated loads, the I10 I-beam bracket model of the B partition of the Ⅰ-Ⅰ section is established by midas. The calculation is as follows: Figure 12 For the I10 I-beam model, Figure 13 isComposite stress envelope diagram of I 10 I-beam, Figure 14 is the shear stress envelope diagram of I 10 I-beam, Figure 15 is the shear stress envelope diagram of I 10 I-beam;

[0203] It can be obtained from the above calculations that: It can be obtained from the above calculations that:

[0204] ; ; m) Take the span of 659 mm at the place with the largest deformation for L;

[0205] It can be seen from the above calculations that the strength and stiffness of the I 10 I-beam bracket in Zone B of Section Ⅰ-Ⅰ meet the specification requirements.

[0206] Stability calculation of the inclined rod of I10 I-beam: The calculated results of the axial force are as follows Figure 16 is the axial force diagram of the inclined rod of I10 I-beam;

[0207] The maximum axial pressure of the inclined rod of I10 I-beam is 17.2 kN, and the strength and stability of the inclined rod are calculated;

[0208] Net cross-sectional area of the I-beam: A = 14.3 cm2; Minimum radius of gyration: ix = 4.14 cm; Length of the I-beam: L = 0.8 m.

[0209] The calculated length coefficient of the I-beam is taken as μ = 1.2 according to the condition of one end fixed and the other end unable to rotate but able to translate during calculation

[0210] Then the slenderness ratio of the inclined rod of the I-beam: λ = μl / ix = 1.2×80 / 4.14 = 23.2.

[0211] The I-beam material is selected as Q235 steel, fy = 235, so .

[0212] According to Appendix Table D of the "Standard for Design of Steel Structures" (GB50017-2017), the stability coefficient of the axially compressed member is obtained: j = 0.976, and the stability check of the column is as follows: ;

[0213] The stability of the inclined rod of I10 I-beam meets the requirements.

[0214] Shear resistance calculation of bolts, as Figure 17 is the reaction force diagram of the I 10 I-beam. The reaction force at the ear plate is 14.5 N, and the shear force borne by a single M20 ordinary bolt is 14.5 / 2 = 7.25 N. The cross-sectional area of a single M20 ordinary bolt is 245 mm2, then the shear stress of the bolt is

[0215] , meeting the requirements.

[0216] Calculation of the bearing capacity of a single vertical pole of a steel pipe scaffold

[0217] The vertical pole is a Q355 steel pipe with a diameter of 60.3 mm and a wall thickness of 3.2 mm. The reaction force received by the I 14 I-beam crossbeam is the vertical force acting on the steel pipe.

[0218] Considering the manufacturing defects, corrosion, etc. of the vertical pole, when calculating, the diameter of the steel pipe is taken as 60 mm and the wall thickness is taken as 3 mm. Then the cross-sectional area A = 5.372 cm2, the radius of gyration i of the vertical pole cross-section is 2.018 cm, and the section modulus W of the vertical pole cross-section is 7.293 cm3; the strength design value of the vertical pole material is f = 300 MPa.

[0219] As Figure 18 shown, the reaction force diagram of the I 10 I-beam;

[0220] The maximum load borne by a single vertical pole is located in area A of section I-I, with a value of 20.3 kN. Considering the increase coefficient of 1.05 for the self-weight of the vertical pole, horizontal pole and diagonal pole, the maximum axial force value borne by the vertical pole is calculated as Nmax = 1.05 × 20.3 = 21.305 kN.

[0221] According to Article 5.3.2 of the "Safety Technical Standards for Steel Pipe Scaffolds for Building Construction" (JGJ / 128 - 2019), the ultimate bearing capacity of a single vertical pole is known. The calculation formula takes the and larger value, where is taken, the step distance h = 50 cm, is taken, is taken, is taken, k = 0.6, a = 0 cm. Therefore, the calculated length is taken, and the slenderness ratio of the vertical pole is: By looking up the table, the stability coefficient is obtained. When not considering the wind load, the allowable bearing capacity of the vertical pole is: ;

[0222] In summary, the bearing capacity of a single vertical pole meets the requirements, but it is necessary to strictly ensure that the length of the adjustable screw rod extending from the upper end of the vertical pole beyond the top horizontal bar does not exceed 65 cm.

[0223] 2.5. Check calculation of the bottom I20a crossbeam

[0224] The I20a I-beam bottom cross beam is set between the box chambers, used to support the steel pipe scaffold and bear the concentrated force transmitted by the vertical poles of the steel pipe scaffold. Both ends of the I20a I-beam bottom cross beam are supported on the T-shaped platforms at the ear plates of the steel beam, and the steel plates of the T-shaped platforms are connected to the ear plates with M20 ordinary bolts. A model of the I20a I-beam bottom cross beam in Zone A of Section Ⅰ-Ⅰ is established using midas for calculation as follows Figure 19 is the model of the I20a I-beam, Figure 20 is the envelope diagram of the combined stress of the I20a I-beam, Figure 21 is the envelope diagram of the shear stress of the I20a I-beam; Figure 22 is the envelope diagram of the deformation of the I20a I-beam;

[0225] ; ; mm, and L is taken as the span of 4020mm at the location with the largest deformation;

[0226] From the above calculations, it can be seen that the strength and stiffness of the I20a I-beam bottom cross beam in Zone A of Section Ⅰ-Ⅰ meet the specification requirements.

[0227] Calculation of bolt shear resistance is as follows Figure 23 is the reaction force diagram of the I20a I-beam:

[0228] The reaction force received at the ear plate is 45.8kN, and the shear force borne by a single M20 ordinary bolt is 45.8 / 2 = 22.9kN. The cross-sectional area of a single M20 ordinary bolt is 245mm2, then the bolt shear stress is τ = 22.9 * 1000 / 245 = 93.47MPa < [τ] = 190MPa. The requirements are met.

[0229] Conclusion: (1) The strength and stiffness checks of the 15mm thick bamboo plywood meet the specification requirements. (2) The strength and stiffness checks of the 8cm×8cm square wood meet the specification requirements. (3) The strength and stiffness checks of the I10 I-beam cross beam and bracket meet the specification requirements. (4) The strength and stiffness checks of the I20a I-beam bottom cross beam meet the specification requirements. (5) The bearing capacity of the φ60.3×3.2mm steel pipe scaffold vertical pole meets the requirements.

[0230] The above is only the preferred embodiment of the present invention patent and is not intended to limit the present invention patent. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention patent shall be included within the protection scope of the present invention patent.

Claims

1. A construction support system for a steel-concrete composite bridge deck, characterized in that, The first support structure of the bridge deck is arranged between the steel box girders, the second support structure of the bridge deck is arranged inside the steel box girder chamber, and the third support structure of the bridge deck is arranged on the flange plate of the steel box girder. The first support structure includes bamboo plywood, longitudinal square timbers, I-beam cross beams, top supports, steel pipe supports, bottom supports, and I-beam bottom cross beams arranged in sequence from top to bottom; The second support structure includes bamboo plywood, longitudinal square timbers, I-beam cross beams, top supports, steel pipe supports, bottom supports, and box girder bottom plates arranged in sequence from top to bottom; The third support structure includes bamboo plywood, longitudinal square timbers, and I-beam brackets arranged in sequence from top to bottom. Angle steels are arranged inside the I-beam brackets, and the I-beam brackets are connected to the ear plates on the steel beam web by bolts.

2. The construction support system for a steel-concrete composite bridge deck according to claim 1, wherein In the first support structure, a support cross beam support is arranged. The support cross beam support includes a vertical ear plate and a steel plate. The vertical ear plate is vertically arranged on the steel beam web, the steel plate is arranged above the vertical ear plate, and diagonal ribs are arranged between the steel plate and the vertical ear plate.

3. A construction method for the concrete - steel composite beam bridge deck, characterized in that, It includes the following steps: S1. Support construction When constructing the bridge deck support between steel box girders, fastener-style steel pipe supports are used for construction. The support system from top to bottom is: bamboo plywood, longitudinal square timbers, I-beam cross beams, top supports, steel pipe supports, bottom supports, and I-beam bottom cross beams; When constructing the bridge deck support inside the steel box girder chamber, fastener-style steel pipe supports are used for construction. The support system from top to bottom is: bamboo plywood, longitudinal square timbers, I-beam cross beams, top supports, steel pipe supports, bottom supports, and box girder bottom plates; When constructing the support of the steel box girder flange plate, the support system from top to bottom is: bamboo plywood, longitudinal square timbers, I-beam brackets, and angle steels; S2. Formwork installation Before installing the formwork, a release agent is comprehensively applied to it. The connection parts between the formworks are blocked with foam expanders; S3. Steel bar binding construction The main steel bar connection method is lap welding; S4. Embedded part installation Embed the embedded parts of components such as bridge deck system guardrails, expansion joints, and traffic engineering, and weld them firmly; S5. Bridge deck concrete project When pouring concrete, it expands from the mid-span to the supports to reduce the influence of support settlement, and the concrete is poured according to the marked height of the two-side formworks; S6. Concrete curing After the concrete is poured, it is covered with geotextiles and watered for curing after the slurry is retracted. When the concrete surface is covered with formworks, the formworks should be kept moist during the curing period; S7. Formwork removal After the top support or wedge block of the support is loosened, the formwork removal work is carried out; the formwork removal follows the principle of first erected, last removed, and last erected, first removed, and is carried out in a cyclic order from the mid-span to the support direction; when removing the side formworks, it can be removed only after the concrete strength can ensure that its surface and edges are not damaged due to formwork removal; first remove the non-load-bearing formworks, and then remove the load-bearing part of the formworks, from top to bottom; when removing the bottom formworks, after the top support and longitudinal and transverse square timbers of the support are removed, gently pry the formwork with a steel bar or tap it with a wooden hammer to remove the first piece, and then remove it piece by piece and section by section; S8. Steel pipe support removal It is carried out in the order of last installed, first removed, and first installed, last removed; the removal of the support should be carried out symmetrically and layer by layer from top to bottom; for the components and reinforcement members on the same layer, follow the order of first upper, then lower, first outer, then inner; S9. I-beam removal After the removal of the square timbers, formworks, I-beams, etc. above the crossbeam is completed, the removal of the I-beam crossbeam is carried out; the I-beam crossbeams are removed one by one from the middle to both ends. First, the I-beams longitudinally connecting between the two crossbeams are removed, and then the bolts are loosened, and the I-beam crossbeams are slowly pulled out by a truck crane; repeat the above steps to complete the removal of the I-beam crossbeams.

Images