Design method of cast-in-place beam formwork

Abstract

The invention relates to the technical field of beam body structure design and construction, in particular to a cast-in-place beam formwork design method which comprises a bottom formwork load calculation step including the steps that S1, the dead load of a bottom formwork and the live load of the bottom formwork are calculated, the dead load of the bottom formwork comprises the gravity of the bottom formwork, the gravity of a side formwork and the gravity of reinforced concrete, and the live load of the bottom formwork is calculated; live loads of the bottom formwork comprise loads generated by concrete vibration and loads generated by personnel and construction; s2, the total load of the bottom formwork is calculated according to the dead load of the bottom formwork and the live load of the bottom formwork; s3, the stress and deflection of the bottom formwork are calculated according to the size of the bottom formwork; and S4, whether the strength of the bottom formwork meets the requirement or not is judged according to the stress and deflection of the bottom formwork. According to the method, the bottom formwork design parameters just meeting the strength requirement can be obtained through calculation, it can be guaranteed that the bottom formwork meets the strength requirement, meanwhile, the minimum steel structure consumption is used, the construction workload is reduced, the construction efficiency is improved, in addition, the self weight of the formwork structure is reduced, and demolding after pouring is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of beam structure design and construction, and in particular to a design method for a cast-in-place beam template. Background Art

[0002] For the beam structure of cast-in-place beams, especially the cast-in-place beam structure in the port area, the concrete beam section is generally supported by multiple steel pipe piles. Before pouring, it is necessary to set up formwork on the steel pipe piles. The formwork includes bottom formwork, side formwork, etc. The bottom formwork needs to be set up between two adjacent steel pipe piles through the transverse and longitudinal beam structure to form a certain span. During pouring, the bottom formwork needs to bear the vertical loads of the upper side formwork, concrete, steel bars, personnel, equipment, etc. The side formwork also needs to bear the horizontal loads generated by the concrete vibration. Therefore, the bottom formwork and side formwork need to have sufficient strength for support; currently, in the cast-in-place beam formwork, the In the design of the slab, especially for the size of the cast-in-place beam formwork, the number and spacing of I-beams and channel steel structures installed on the horizontal and vertical beams, there is a lack of effective calculation methods to verify whether the strength of the formwork meets the use requirements. The only choice is based on the experience of on-site construction personnel. In order to ensure the stability of the beam structure and not cause safety hazards, as many I-beams and channel steels as possible are often arranged in the horizontal and vertical beam structures of the bottom formwork to improve the supporting performance. However, too many steel structures will also increase the construction workload and reduce construction efficiency. In addition, it will also increase the self-weight of the formwork structure, causing inconvenience to demoulding after pouring. Summary of the invention

[0003] The purpose of the present invention is to overcome the technical problem that the prior art relies on experience to design cast-in-place beam templates, which will result in too many steel structures in the templates and thus cause low construction efficiency, and to provide a design method for cast-in-place beam templates.

[0004] The present invention provides a design method for a cast-in-place beam formwork, which comprises a bottom formwork and a side formwork, wherein the bottom formwork is horizontally erected between a plurality of steel pipe piles, and the side formwork is vertically installed on the bottom formwork; the design method comprises a load calculation step for the bottom formwork, comprising: S1: respectively calculating the dead load of the bottom formwork and the live load of the bottom formwork, wherein the dead load of the bottom formwork comprises the gravity of the bottom formwork, the gravity of the side formwork and the gravity of reinforced concrete, and the live load of the bottom formwork comprises the load generated by concrete vibration, and the load generated by personnel and construction; S2: calculating the total load of the bottom formwork according to the dead load of the bottom formwork and the live load of the bottom formwork; S3: calculating the stress and deflection of the bottom formwork according to the size of the bottom formwork; S4: judging whether the strength of the bottom formwork meets the requirements according to the stress and deflection of the bottom formwork.

[0005] The design method of the present application can divide the load borne by the bottom formwork into a dead load and a live load and perform calculations separately, so as to obtain the total load borne by the bottom formwork during the construction process, and further calculate the stress and deflection parameters of the bottom formwork, and then compare the calculated stress and deflection parameters with the parameter values ​​specified in the construction specification standard. If the stress and deflection parameters are less than the standard value, the strength requirement is met; if the stress and deflection parameters are greater than the standard value, the size of the steel structure in the bottom formwork needs to be further adjusted until it meets the requirement after recalculation; the present design method can obtain the bottom formwork design parameters that just meet the strength requirements through calculation, so as to ensure that the bottom formwork meets the strength requirements while using the least amount of steel structure, thereby reducing the construction workload and improving the construction efficiency. In addition, the self-weight of the formwork structure is reduced, which facilitates demolding after pouring.

[0006] Preferably, the bottom formwork includes a crossbeam bottom formwork and a longitudinal beam bottom formwork which are perpendicular to each other, the crossbeam bottom formwork is mounted on the longitudinal beam bottom formwork, and the crossbeam bottom formwork and the longitudinal beam bottom formwork both include a splint, a plurality of secondary beams and a plurality of main beams; the design method includes load calculation steps for the crossbeam bottom formwork and the longitudinal beam bottom formwork, including: A1: calculating the dead load of the splint, the secondary beam or the main beam, and calculating the live load of the splint, the secondary beam or the main beam; A2: calculating the total load of the splint, the secondary beam or the main beam according to the dead load and live load of the splint, the secondary beam or the main beam; A3: calculating the stress and deflection of the splint, the secondary beam or the main beam according to the size of the splint, the secondary beam or the main beam; A4: judging whether the strength of the splint, the secondary beam or the main beam meets the requirements according to the stress and deflection of the splint, the secondary beam or the main beam.

[0007] The crossbeam bottom formwork and the longitudinal beam bottom formwork are modularly designed. Each component in the crossbeam bottom formwork and the longitudinal beam bottom formwork can be checked separately to verify whether the stress and deflection parameters they bear meet the strength requirements. If not, it is necessary to adjust the spacing and number of plywood, secondary beams and main beams in the crossbeam bottom formwork and the longitudinal beam bottom formwork, and then re-calculate until it meets the requirements.

[0008] Preferably, several of the main beams are connected by welding or bolting, and several of the secondary beams are connected to the main beams by welding or bolting; several of the main beams are located in a first plane, and several of the secondary beams are located in a second plane, and the first plane is parallel to the second plane and is spaced apart.

[0009] Specifically, for example, in the bottom form of the crossbeam, 6 main beams and 14 secondary beams are included, among which 4 main beams are arranged transversely and parallel to each other, and the other 2 main beams are arranged longitudinally and are respectively connected to the two ends of the 4 transversely arranged main beams, that is, the 4 transversely arranged main beams can be connected through 2 longitudinally arranged main beams, and the 6 main beams can be connected to form a whole; 14 secondary beams can be arranged longitudinally and parallel to each other, the 14 secondary beams can be connected to the 4 transversely arranged main beams, and the 14 secondary beams can be connected to the 6 main beams to form an integral structure, and the main beams and the main beams and the secondary beams can be fixedly connected by welding or bolting. The bottom formwork can be formed into a modular structure. Before the overall construction of the formwork, the strength design and verification can be carried out for a single modular formwork and the assembly can be completed. When demolding after pouring, the entire formwork can be disassembled by cutting the corbels on the steel pipe piles. Since the existing scattered formwork structure has components such as I-beams and channel steels that are directly erected without any fixing measures, the modular formwork structure of the present application avoids the problem of reduced construction efficiency caused by separately erecting and disassembling components such as I-beams and channel steels during construction. The construction is more convenient and efficient, and the material loss rate is reduced. At the same time, the modular formwork structure is more conducive to repeated turnover after disassembly.

[0010] In addition, the modular formwork structure of the present application is fixed by welding so that multiple I-beams are located on the same plane, and multiple channel steels are located on another parallel plane. The formwork structure is a two-layer plane. However, since the scattered formwork structure has no fixing measures, the transversely arranged I-beams need to be erected on the longitudinally arranged I-beams, so that the scattered formwork structure is at least three layers. Therefore, the modular formwork structure of the present application is reduced from the existing three-layer structure to two layers, and the thickness of the formwork can be further reduced. For example, the main beam adopts 25# I-beams. After the formwork structure is reduced by one layer, the thickness can be reduced by about 25cm. During construction, the top of the formwork The elevation is fixed, that is, the height of the upper surface of the template must meet the construction standards, and the lower surface of the template must be erected on the corbel of the steel pipe pile. If the thickness of the template is too large, it means that the height of the corbel is lower. At high tide, the position of the corbel is more likely to be below the water surface, which is not conducive to the welding construction of the corbel, and will shorten the construction window period of the corbel, which may lead to an extension of the construction period and reduced efficiency. After the three-layer structure of the template is reduced to two layers, the thickness of the template can be significantly reduced in the present application, and the position of the corbel on the steel pipe pile can be raised, thereby reducing the possibility of the corbel being below the water surface, extending the construction window period of the corbel, and improving the construction efficiency of the corbel.

[0011] Preferably, the design method also includes a load calculation step for the side formwork, including: B1: calculating the maximum lateral pressure F generated by concrete vibration on the side formwork and the horizontal load F' generated by pouring concrete; B2: calculating the total load of the side formwork based on the maximum lateral pressure F generated by concrete vibration on the side formwork and the horizontal load F' generated by pouring concrete.

[0012] Preferably, the calculation formula of the maximum side pressure F is:

[0013]

[0014] as well as

[0015] F=γ c H (2)

[0016] The maximum side pressure F is the smaller value of equation (1) and equation (2).

[0017] Preferably, the maximum horizontal load F' generated by pouring concrete is 6 kN / m 2 .

[0018] Preferably, calculating the total load of the side formwork includes respectively calculating the standard value q' of the side pressure and the design value q of the side pressure, q'=F+F'; q=F×dead load partial coefficient+F'×live load partial coefficient; the dead load partial coefficient is 1.2, and the live load partial coefficient is 1.4.

[0019] The main force types of the side formwork can be divided into the lateral pressure caused by concrete vibration and the horizontal load caused by pouring concrete. The lateral pressure caused by concrete vibration can be verified by the corresponding calculation formula, and the horizontal load caused by pouring concrete can refer to the standard values ​​in the relevant specifications.

[0020] Preferably, the side formwork includes a splint and a plurality of channel steels, and the load calculation step of the side formwork also includes: C1: respectively calculating the stress and deflection of the splint and the stress and deflection of the channel steel; C2: judging whether the stress and deflection of the splint and the channel steel meet the requirements.

[0021] Preferably, the calculation formula for the stress σ of the clamping plate and the channel steel is: σ=M / W; wherein M is the bending strength and W is the cross-sectional parameter.

[0022] Preferably, the calculation formula for the deflection ω of the splint and the channel steel is: ω=(Ml^2) / 9.6EI; wherein M is the bending strength, l is the maximum span size of the splint or the channel steel, E is the elastic modulus of the splint or the channel steel, and I is the section moment of inertia of the splint or the channel steel.

[0023] The side formwork is mainly composed of channel steel and plywood. The corresponding calculation formulas can be used to verify the force parameters of the channel steel and plywood, and compared with the relevant standard values ​​to determine whether they meet the requirements. If not, it is necessary to adjust the spacing and number of plywood and channel steel in the side formwork, and then recalculate until it meets the requirements.

[0024] Preferably, a plurality of corbels are provided on the steel pipe piles, and the bottom formwork is erected on the corbels; the design method also includes a load calculation step for the corbels, including: D1: respectively calculating the bending stress and shear stress parameters of the corbels; D2: judging whether the strength of the corbels meets the requirements based on the bending stress and shear stress parameters of the corbels.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention provides a design method for a cast-in-place beam formwork. Through the design method of the present application, the load borne by the bottom formwork can be divided into a dead load and a live load, and the loads are calculated separately. The total load borne by the bottom formwork during the construction process can be obtained, and the stress and deflection parameters of the bottom formwork can be further calculated. The calculated stress and deflection parameters are then compared with the parameter values ​​specified in the construction specification standard. If they are less than the standard values, the strength requirements are met. If they are greater than the standard values, the size of the steel structure in the bottom formwork needs to be further adjusted until it meets the requirements after recalculation. The present design method can obtain the bottom formwork design parameters that just meet the strength requirements by calculation, and can ensure that the bottom formwork meets the strength requirements while using the least amount of steel structure, thereby reducing the construction workload and improving the construction efficiency. In addition, the self-weight of the formwork structure is also reduced, which is convenient for demolding after pouring.

[0027] 2. The present invention provides a formwork structure for cast-in-place beams. The main beams and the secondary beams are connected with the main beams by welding or bolting to form a modular overall structure. Before the overall construction of the formwork, the strength design verification and assembly of the individual modular formworks can be performed. When demolding after pouring, the formwork can be disassembled as a whole by cutting off the corbels on the steel pipe piles. The construction is more convenient and efficient, and the material loss rate can be reduced. In addition, the existing three-layer formwork structure can be reduced to a two-layer structure, which can significantly reduce the thickness of the formwork, thereby raising the position of the corbels on the steel pipe piles, reducing the possibility of the corbels being below the water surface, extending the construction window period of the corbels, and improving the construction efficiency of the corbels. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a plan view of the bottom template.

[0029] Figure 2 This is a plan view of the bottom formwork of the beam.

[0030] Figure 3This is a schematic cross-sectional view of the bottom formwork of the beam.

[0031] Figure 4 This is a schematic diagram of the vertical assembly of the beam bottom formwork.

[0032] Figure 5 This is a plan view of the longitudinal beam bottom formwork.

[0033] Figure 6 This is a schematic cross-sectional diagram of the longitudinal beam bottom mold.

[0034] Figure 7 This is a schematic diagram of the vertical assembly of the longitudinal beam bottom formwork.

[0035] Figure 8 This is a schematic diagram of the back elevation of the side formwork.

[0036] Fig. 9 This is a plan view of the corbel position.

[0037] Markings in the figure:

[0038] 1. Steel pipe piles, 2. Bottom formwork, 21. Bottom formwork of horizontal beam, 22. Bottom formwork of longitudinal beam, 23. Plywood, 24. Secondary beam, 25. Main beam, 3. Side formwork, 31. 12# channel steel, 4. Corbel. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below in conjunction with specific embodiments. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0040] Unless otherwise specified, in the description of the specific embodiments of the present invention, the terms indicating the orientation or position relationship such as "up", "down", "left", "right", "center", "inside", "outside", etc. are all expressions based on the orientation or position relationship shown in the drawings, or are the orientation or position relationship when the invented product / equipment / device is usually used. These terms of orientation or position relationship are only for the convenience of describing the scheme of the present invention or simplifying the description in the specific embodiments, so as to facilitate the technicians to quickly understand the scheme, and do not indicate or imply that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific position relationship, and therefore cannot be understood as a limitation on the present invention.

[0041] In addition, if the terms "horizontal", "vertical", "overhanging", "parallel" and the like appear, it does not mean that the corresponding devices / components / elements are required to be absolutely horizontal or vertical or overhanging or parallel, but may be slightly tilted or have deviations. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but may be slightly tilted. Alternatively, it can be simplified to mean that the corresponding devices / components / elements are set in directions such as "horizontal", "vertical", "overhanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably an error / deviation within ±8%, more preferably an error / deviation within ±6%, more preferably an error / deviation within ±5%, and more preferably an error / deviation within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its role in the scheme of the present invention.

[0042] In addition, the expressions “first”, “second”, “third”, etc., which appear in the terms, are merely used to distinguish the description of the same or similar components and should not be understood as emphasizing or implying the relative importance of specific components.

[0043] In addition, in the description of the embodiments of the present invention, "several", "plurality" and "a number" represent at least 2. It can be any number such as 2, 3, 4, 5, 6, 7, 8, 9, and even more than 9.

[0044] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / restricted, the terms "set", "install", "connect", "connected", "provided with", "laid", and "arranged" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection, and can be welding, riveting, bolting, threading, and other commonly used connection means in the field. This connection can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, and it can be the internal connection of two elements.

[0045] Example

[0046] This embodiment provides a design method for a cast-in-place beam formwork.

[0047] like Figures 1 to 9As shown in the figure, there are schematic diagrams of the structures and positions of the bottom formwork 2, the crossbeam bottom formwork 21, the longitudinal beam bottom formwork 22, the side formwork 3 and the corbel 4, wherein the crossbeam bottom formwork 21 and the longitudinal beam bottom formwork 22 are crisscrossed and erected between multiple steel pipe piles 1 to form the overall structure of the bottom formwork 2. Specifically, the longitudinal beam bottom formwork 22 is erected on the corbel 4 of the steel pipe pile 1, and the crossbeam bottom formwork 21 is erected on the longitudinal beam bottom formwork 22; the bottom formwork 2 is horizontally arranged, and the side formwork 3 is vertically installed above the bottom formwork 2. The crossbeam bottom formwork 21 and the longitudinal beam bottom formwork 22 both include a splint 23, a plurality of secondary beams 24 and a plurality of main beams 25, wherein the secondary beams 24 can be 8# channel steels, the main beams 25 can be 25# I-beams, and the side formwork 3 includes a splint 23 and a 12# channel steel 31.

[0048] Specifically, the crossbeam bottom mold 21 may include 6 main beams 25 and 14 secondary beams 24, wherein 4 main beams 25 are arranged transversely and parallel to each other, and the other 2 main beams 25 are arranged longitudinally and are respectively connected to the two ends of the 4 transversely arranged main beams 25, that is, the 4 transversely arranged main beams 25 can be connected through 2 longitudinally arranged main beams 25, and the 6 main beams 25 can be connected to form a whole; 14 secondary beams 24 can be arranged longitudinally and parallel to each other, the 14 secondary beams 24 can be connected to the 4 transversely arranged main beams 25, and the 14 secondary beams 24 and the 6 main beams 25 can be connected to each other. The beams 25 are connected to form an integral structure. The main beams 25 and the main beams 25 and the secondary beams 24 can be fixedly connected by welding or bolting, so that the bottom template can be formed into a modular structure; the longitudinal beam bottom template 22 may include 6 main beams 25 and 15 secondary beams 24. Of course, the number of main beams 25 and secondary beams 24 in the crossbeam bottom template 21 and the longitudinal beam bottom template 22 needs to be determined based on the design verification results. The number of main beams 25 and secondary beams 24 may change under different working conditions. This application does not specifically limit the number of main beams 25 and secondary beams 24 in the bottom template.

[0049] In addition, the six main beams 25 in the crossbeam bottom formwork 21 are located on a first plane, and the 14 secondary beams 24 are located on a second plane. The first plane and the second plane are parallel and spaced apart from each other. That is to say, the first plane and the second plane do not overlap (are not coplanar), so that the crossbeam bottom formwork 21 forms a two-layer structure. Similarly, the six main beams 25 and the 15 secondary beams 24 in the longitudinal beam bottom formwork 22 are also located on different planes to form a two-layer structure. Compared with the existing three-layer structure of the loose-laying formwork, the two-layer structure formwork can further reduce the thickness, increase the position of the corbel on the steel pipe pile, reduce the possibility of the corbel being below the water surface, extend the construction window period of the corbel, and improve the construction efficiency of the corbel.

[0050] The template structure shown in the figure is taken as an example to carry out design verification using this design method, wherein the numerical value substituted into the formula for calculation only represents one size and mass value of the template, and the scope of protection claimed by the present invention is not limited to a specific numerical value.

[0051] The vertical loads during construction mainly include:

[0052] Dead load: self-weight of formwork (bottom formwork, side formwork, pouring platform plate), self-weight of newly poured concrete (the height of the first pouring of concrete for the track beam is 2.15 meters; the pouring height of the longitudinal beam is 1.55 meters and 1.65 meters; the size of the cross beam is 1.4-2.0 meters, and the self-weight of concrete is the self-weight of concrete with a pouring height of 1.65 meters; the height of the first pouring of concrete for the cantilever structure of the track beam on the shore side is 2.15 meters);

[0053] Live load: load from construction workers and equipment, load from vibrating concrete (vertical direction).

[0054] The horizontal loads during construction include: loads generated by vibrating concrete.

[0055] Coefficient value: The dead load partial coefficient is 1.2; the live load partial coefficient is 1.4.

[0056] The template size (unit: mm) and the template size (length × width) are: the size of the middle longitudinal beam bottom template 22 plate 2 is: 5100×1800; the size of the cross beam bottom template 21 is 4700×1800 and 4148×1800; the side templates are 4380×1780, 3930×1780, 3430×1780, and 4380×2250.

[0057] The calculation method of the beam bottom mold 21 is as follows:

[0058] The main beam 25 of the crossbeam bottom formwork 21 adopts 25# I-steel with a center-to-center spacing of 470mm, and there are 4 beams in total. The secondary beam 24 adopts 8# channel steel with a spacing of 310mm, and there are 14 beams in total. All of them are processed with new materials. Holes are opened on the 8# channel steel, and 50*30mm wooden strips are fixed to the 8# channel steel with bolts, and 18mm thick plywood 23 is nailed on the wooden strips. The crossbeam bottom formwork 21 has two sizes. The template with the largest span is taken for verification, so the 4700×1800 crossbeam bottom formwork 21 is taken for verification.

[0059] Calculation of dead load of splint 23:

[0060] Deadweight of bottom mold plate: 83×10 / 1000=0.83KN;

[0061] Side formwork deadweight: 500×10×2 / 1000=10KN;

[0062] Self-weight of pouring platform slab:

[0063] Self-weight of reinforced concrete: 6.0×1.4×1.65×2500×10 / 1000=346.5KN;

[0064] The standard value of total dead load is: G = 360.33KN;

[0065] The total dead load design value is: G = 360.33 × 1.2 = 432.4KN;

[0066] The design value of the dead load surface load is:

[0067] Live load calculation of clamping plate 23:

[0068] Load generated by vibrating concrete: 2kN / m 2 ;

[0069] Human and construction load: 2.5kN / m 2

[0070] The standard value of total live load is: 4.5kN / m 2 ;

[0071] The total live load design value is: 4.5×1.4=6.3kN / m 2 ;

[0072] Combination of forces on the splint 23

[0073] Select 1cm plywood as the calculation unit, and the design value of the uniformly distributed load is:

[0074] q=0.01×(65.72+6.3)=0.72N / mm;

[0075] Force calculation of splint 23

[0076] The board calculation specification stipulates that when the board has only transverse ribs but no small longitudinal ribs, the panel is a one-way board, and any grid of the board can be taken as the calculation unit during calculation. The one-way board is mainly bent in one direction, and the ratio of the long side to the short side is greater than or equal to 2, so the bending moment in the long span direction can be ignored, and it is approximately considered that the force is only transmitted to the long side along the short span direction, and the structure is approximately a simply supported structure, so it can be approximately considered that the maximum span of the splint is 310mm and the thickness is 1.8cm; 1cm is selected as the calculation unit:

[0077] The cross-sectional parameters of the splint 23 are:

[0078] The moment of inertia of the cross section of the clamping plate 23 is:

[0079] Calculation of bending strength of splint 23:

[0080] The template stress of the splint 23 under bending state is:

[0081] Meet the requirements.

[0082] Deflection calculation of splint 23:

[0083] Meet the requirements.

[0084] Secondary beam 24 dead load calculation

[0085] Deadweight of bottom mold plate: 83×10 / 1000=0.83KN;

[0086] Deadweight of bottom mold wood: 25×10 / 1000=0.25KN;

[0087] Side formwork deadweight: 500×10×2 / 1000=10KN;

[0088] Self-weight of pouring platform slab:

[0089] Self-weight of reinforced concrete: 6.0×1.4×1.65×2500×10 / 1000=346.5KN;

[0090] The standard value of total dead load is: G = 360.58KN;

[0091] The total dead load design value is: G = 360.58 × 1.2 = 432.7KN;

[0092] The design value of the dead load surface load is:

[0093] Live load calculation of secondary beam 24

[0094] Load generated by vibrating concrete: 2kN / m 2 ;

[0095] Human and construction load: 2.5kN / m 2

[0096] The standard value of total live load is: 4.5kN / m 2 ;

[0097] The total live load design value is: 4.5×1.4=6.3kN / m 2 ;

[0098] Combination of forces on the secondary beam 24

[0099] The unit weight of 8# slot is 8.045kg / m, so the deadweight is 0.46×8.045×10 / 1000=0.1KN / m, and the uniformly distributed load design value is: q=0.46×(65.76+6.3)+0.1=33.25N / mm;

[0100] Force calculation of secondary beam 24

[0101] The maximum spacing of the secondary beam 24 is 310 mm, and the span is: l = 460 mm:

[0102] The cross-sectional characteristics of two 8# slots are: W = 2 × 25.3 × 10 3 mm 3 ; I = 2 × 101 × 10 4 mm 4 ;

[0103] Take three spans and calculate the maximum bending moment as approximate continuous beam:

[0104] M=0.1ql 2 =0.1×33.25×460 2 =703570N·mm

[0105] Strength verification of secondary beam 24: Meet the requirements.

[0106] Secondary beam 24 deflection verification:

[0107] Meet the requirements.

[0108] Calculation of the dead load of main beam 25

[0109] Deadweight of bottom mold plate: 83×10 / 1000=0.83KN;

[0110] Deadweight of bottom mold wood: 25×10 / 1000=0.25KN;

[0111] Weight of bottom die 8# slot: 36.24×8.045×10 / 1000=2.92KN;

[0112] Side formwork deadweight: 500×10×2 / 1000=10KN;

[0113] Self-weight of pouring platform slab:

[0114] Self-weight of reinforced concrete: 6.0×1.4×1.65×2500×10 / 1000=346.5KN;

[0115] The standard value of total dead load is: G = 363.5KN;

[0116] The total dead load design value is: G = 363.5 × 1.2 = 436.2KN;

[0117] The design value of the dead load surface load is:

[0118] Live load calculation of main beam 25

[0119] Load generated by vibrating concrete: 2kN / m2 ;

[0120] Human and construction load: 2.5kN / m 2

[0121] The standard value of total live load is: 4.5kN / m 2 ;

[0122] The total live load design value is: 4.5×1.4=6.3kN / m 2 ;

[0123] Combination of forces on main beam 25

[0124] The unit weight of 25# I-beam is 42.03kg / m, so the deadweight of 25# I-beam is:

[0125] 4.7×42.03×10 / 1000=1.97KN / m;

[0126] Design value of uniformly distributed load: q = 1.4 × (66.29 + 6.3) + 1.97 = 103.6 N / mm;

[0127] Main beam 25 force calculation

[0128] The maximum spacing of the main beam 25 is 460mm, and the span is: l = 4700mm. The load is transferred to the 25# I-beam through the 8# channel steel, and the load is approximated as a uniformly distributed load:

[0129] The cross-sectional parameters of the four 25a I-beams are: W = 4 × 402 × 10 3 mm 3 ; I = 4 × 5020 × 10 4 mm 4 ;

[0130] Take three spans and calculate the maximum bending moment as approximate continuous beam:

[0131] M=0.1ql 2 =0.1×103.6×4700 2 =228.85×10 6 N·mm

[0132] Strength verification of main beam 25: meet the requirements;

[0133] Calculation of 25 degree deflection of main beam:

[0134] meet the requirements;

[0135] The calculation method of the longitudinal beam bottom mold 22 is as follows:

[0136] The main beam of the longitudinal beam bottom formwork 22 is made of 25# I-steel with a center-to-center spacing of 470mm, and there are 4 beams in total. The secondary beam is made of 8# channel steel with a spacing of 315mm, and there are 15 beams in total. All of them are processed with new materials. Holes are opened on the 8# channel steel, and 50*30mm wooden strips are fixed to the 8# channel steel with bolts, and 18mm thick plywood is nailed on the wooden strips. There are two sizes of longitudinal beam bottom formwork. The template with the largest span is taken for verification, so the longitudinal beam bottom formwork of 5100×1800 is taken for verification.

[0137] Clamp 23 Dead Load Calculation

[0138] Deadweight of bottom mold plate: 88×10 / 1000=0.88KN;

[0139] Side formwork deadweight: 500×10×2 / 1000=10KN;

[0140] Self-weight of pouring platform slab:

[0141] Self-weight of reinforced concrete: 6.4×1.4×1.65×2500×10 / 1000=369.6KN;

[0142] The standard value of total dead load is: G = 383.48KN;

[0143] The total dead load design value is: G = 383.48 × 1.2 = 460.18 KN;

[0144] The design value of the dead load surface load is:

[0145] Clamp 23 live load calculation

[0146] Load generated by vibrating concrete: 2kN / m 2 ;

[0147] Human and construction load: 2.5kN / m 2

[0148] The standard value of total live load is: 4.5kN / m 2 ;

[0149] The total live load design value is: 4.5×1.4=6.3kN / m 2 ;

[0150] Combination of forces on the splint 23

[0151] Select 1cm plywood as the calculation unit, and the design value of the uniformly distributed load is:

[0152] q=0.01×(64.45+6.3)=0.71N / mm;

[0153] Force calculation of splint 23

[0154] It can be seen from the figure that the structural panel is a one-way board, so it can be approximately considered that the maximum span of the plywood is 315mm and the thickness is 1.8cm; 1cm plywood is selected as the calculation unit:

[0155] The cross-sectional parameters of the splint 23 are:

[0156] Calculation of bending strength of splint 23:

[0157] The template stress of the splint 23 under bending state is:

[0158] Meet the requirements.

[0159] Deflection calculation of splint 23:

[0160] Meet the requirements.

[0161] Secondary beam 24 dead load calculation

[0162] Deadweight of bottom mold plate: 88×10 / 1000=0.88KN;

[0163] Deadweight of bottom mold wood: 20×10 / 1000=0.2KN;

[0164] Side formwork deadweight: 500×10×2 / 1000=10KN;

[0165] Self-weight of pouring platform slab:

[0166] Self-weight of reinforced concrete: 6.4×1.4×1.65×2500×10 / 1000=369.6KN;

[0167] The standard value of total dead load is: G = 383.68KN;

[0168] The total dead load design value is: G = 383.68 × 1.2 = 460.42KN;

[0169] The design value of the dead load surface load is:

[0170] Live load calculation of secondary beam 24

[0171] Load generated by vibrating concrete: 2kN / m 2 ;

[0172] Human and construction load: 2.5kN / m 2

[0173] The standard value of total live load is: 4.5kN / m 2 ;

[0174] The total live load design value is: 4.5×1.4=6.3kN / m 2 ;

[0175] Combination of forces on the secondary beam 24

[0176] The unit weight of 8# slot is 8.045kg / m, so the deadweight is 0.46×8.045×10 / 1000=0.1KN / m, and the uniformly distributed load design value is: q=0.46×(64.48+6.3)+0.1=32.66N / mm;

[0177] Force calculation of secondary beam 24

[0178] The maximum spacing of the secondary beam 24 is 315 mm, and the span is: l = 460 mm

[0179] 8# slot cross section parameters: W = 2 × 25.3 × 10 3 mm 3 ; I = 2 × 101 × 10 4 mm 4 ;

[0180] Take three spans and calculate the maximum bending moment as approximate continuous beam:

[0181] M=0.1ql 2 =0.1×32.66×460 2 =691085.6N·mm

[0182] Strength verification of secondary beam 24: meet the requirements;

[0183] Secondary beam 24 deflection verification:

[0184] Meet the requirements; Main beam 25 dead load calculation

[0185] Deadweight of bottom mold plate: 88×10 / 1000=0.88KN;

[0186] Deadweight of bottom mold wood: 20×10 / 1000=0.2KN;

[0187] Deadweight of bottom mold 8# slot: 338×10 / 1000=3.38KN;

[0188] Side formwork deadweight: 500×10×2 / 1000=10KN;

[0189] Self-weight of pouring platform slab:

[0190] Self-weight of reinforced concrete: 6.4×1.4×1.65×2500×10 / 1000=369.6KN;

[0191] The standard value of total dead load is: G = 387.06KN;

[0192] The total dead load design value is: G = 387.06 × 1.2 = 464.48KN;

[0193] The design value of the dead load surface load is:

[0194] Live load calculation of main beam 25

[0195] Load generated by vibrating concrete: 2kN / m 2 ;

[0196] Human and construction load: 2.5kN / m 2

[0197] The standard value of total live load is: 4.5kN / m 2 ;

[0198] The total live load design value is: 4.5×1.4=6.3kN / m 2 ;

[0199] Combination of forces on main beam 25

[0200] The unit weight of 25a# I-beam is 42.03kg / m, so the deadweight of 25a# I-beam is:

[0201] 5.1×42.03×10 / 1000=2.14KN / m;

[0202] Design value of uniformly distributed load: q = 1.4 × (65.05 + 6.3) + 2.14 = 102.03 N / mm;

[0203] Main beam 25 force calculation

[0204] The maximum spacing of the main beam 25 is 460mm, and the span is: l = 5100mm. The load is transferred to the 25a# I-beam through the 8# channel steel, and the load is approximated as a uniformly distributed load:

[0205] The cross-sectional parameters of the four 25a I-beams are: W = 4 × 402 × 10 3 mm 3 ; I = 4 × 5020 × 10 4 mm 4 ;

[0206] Take three spans and calculate the maximum bending moment as approximate continuous beam:

[0207] M=0.1ql 2 =0.1×102.03×5100 2 =265.38×106 N·mm

[0208] Strength verification of main beam 25: Meet the requirements.

[0209] Calculation of 25 degree deflection of main beam:

[0210] Meet the requirements.

[0211] The calculation method of side formwork 3 is as follows:

[0212] The side formwork 3 is made of the newly purchased 12# channel steel 31. After it is made, holes are drilled on the 12# channel steel 31, 50×30mm wooden strips are nailed, and 18mm plywood is nailed on the wooden strips. Because the side formwork has many sizes, the side formwork 3 of the beam with a size of 4380×2200mm is the most unfavorable, so this size side formwork is taken as an example for verification.

[0213] Maximum lateral pressure of fresh concrete on the side formwork:

[0214] When using an internal vibrator, the maximum pressure of the newly poured concrete on the formwork side can be calculated according to the following two formulas, and the smaller value of the two formulas is taken:

[0215]

[0216] F=γ c H=25×1.65=41.25KN / m 2 ;

[0217] Where: F-maximum lateral pressure of newly poured concrete on the formwork (KN / m 2 );

[0218] γ c - Gravity density of concrete (take 25KN / m 3 );

[0219] t0 - initial setting time of fresh concrete, using the formula Where T is the temperature of the concrete ( 0 );

[0220] V-concrete pouring speed;

[0221] H-total height from the concrete lateral pressure calculation position to the top surface of the newly poured concrete (m);

[0222] β1-admixture effect correction coefficient, which is 1.0 when no admixture is added and 1.2 when admixture with retarding effect is added;

[0223] β2-concrete slump correction coefficient, when the slump is less than 30mm, take 0.85; when the slump is 50-90mm, take

[0224] 1.0; 110-150mm, take 1.15;

[0225] So take F = 41.25KN / m 2 ;

[0226] (1) Horizontal load generated when pouring concrete:

[0227] The maximum horizontal load generated when pouring concrete is 6kN / m 2 ;

[0228] (2) Standard value of template side pressure:

[0229] q'=41.25+6=47.25KN / m 2 ;

[0230] (3) Design value of template side pressure:

[0231] q=1.2×41.25+1.4×6=57.9KN / m 2 ;

[0232] Force calculation of each part of side formwork 3

[0233] Clamp 23 calculation

[0234] It can be seen from the figure that the plywood is a one-way board. When calculating, it can be approximately assumed that the maximum span of the plywood is 320mm and the thickness of the board is 1.8cm. Select a 1cm wooden board as the calculation unit, and the force calculation is as follows:

[0235] q1=57.9×0.01=0.579N / mm;

[0236] Calculation of flexural strength:

[0237] The cross-sectional parameters of the splint 23 are:

[0238] Strength verification: meet the requirements;

[0239] Deflection calculation:

[0240]

[0241] 12# Channel Steel 31 Verification

[0242] The effective calculated length of 12# channel steel 31 is: l = 1650mm; the bearing side pressure width is 320mm;

[0243] q2=57.9×0.32=18.53N / mm;

[0244]

[0245] 12# channel steel 31 section parameters: W = 62.1cm 3 ; I = 391 cm 4 ;

[0246] Strength calculation: Meet the requirements.

[0247] Deflection calculation:

[0248] Meet the requirements.

[0249] Bearing capacity calculation of corbel 4:

[0250] All loads on the bottom formwork are ultimately concentrated on the bracket 4. According to the above calculation, since the longitudinal beam bracket is not only subject to the construction load of the longitudinal beam itself but also to the vertical downward pressure generated during the pouring of the cross beam concrete, the concentrated force on the bracket is the largest, that is, the support reaction force generated by the longitudinal beam supporting the steel. The above calculation has been calculated, and the force is P = 246.06KN.

[0251] The bracket 4 is welded with Q355B steel with a thickness of 18mm (see the vertical pile bracket structure diagram for details). In the most unfavorable case of the horizontal steel plate verification, all forces are concentrated on the horizontal steel plate, and the horizontal steel plate is subjected to force P = 246.06KN, so

[0252] The bending moment of the bracket 4 is M = 246.06 × 0.5 = 123.03 kN.m,

[0253] Web section characteristics: W = b × h2 / 6 = 2 × 18 × 5002 / 6 = 1.5 × 106 mm 3

[0254] Web cross-sectional area: A = b × h = 2 × 18 × 500 = 1.8 × 104 mm 3

[0255] Corbel 4 bending stress σ=M / W=123.03×106 / 1.5×106=82.02<295N / mm 2

[0256] Shear stress of bracket 4: τ=P / A=246.06×103 / 1.8×104=13.67<170N / mm 2

[0257] Therefore, corbel 4 meets the requirements.

[0258] Weld calculation

[0259] Welding foot size: h w ≥8mm

[0260] Weld length: l w =50cm

[0261] The maximum shear force that the weld can withstand is Nmax

[0262] Design value of weld shear strength f t w =200N / mm 2

[0263] Nmax=0.7f t w ·l w ·h w =0.7×200×8×500=560KN

[0264] Considering 1.5 times the safety factor, the bearing capacity of each corbel is 246.06×1.5=369.09KN

[0265] Based on the calculation results of the bearing capacity of each part of the corbel 4, the bearing capacity of the corbel 4 is 560kN, so the corbel 4 can meet the requirements as a construction platform support.

[0266] In summary, the present invention provides a design method for cast-in-place beam formwork. Through the design method of the present application, the load borne by the bottom formwork can be divided into a dead load and a live load and calculated separately, and the total load borne by the bottom formwork during the construction process can be obtained, and the stress and deflection parameters of the bottom formwork can be further calculated, and then the calculated stress and deflection parameters are compared with the parameter values ​​specified in the construction specification standard. If they are less than the standard value, the strength requirements are met. If they are greater than the standard value, the size of the steel structure in the bottom formwork needs to be further adjusted until it meets the requirements after recalculation; the present design method can obtain the bottom formwork design parameters that just meet the strength requirements by calculation, which can ensure that the bottom formwork meets the strength requirements while using the least amount of steel structure, thereby reducing the construction workload and improving the construction efficiency. In addition, the self-weight of the formwork structure is also reduced, which facilitates demolding after pouring.

[0267] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A design method for a cast-in-place beam formwork, characterized in that: The cast-in-place beam formwork comprises a bottom formwork (2) and a side formwork (3), wherein the bottom formwork (2) is horizontally erected between a plurality of steel pipe piles (1), and the side formwork (3) is vertically installed on the bottom formwork (2); The design method comprises a load calculation step of the bottom template (2), comprising: S1: respectively calculating the dead load of the bottom formwork (2) and the live load of the bottom formwork (2), wherein the dead load of the bottom formwork (2) includes the gravity of the bottom formwork (2), the gravity of the side formwork (3) and the gravity of the reinforced concrete, and the live load of the bottom formwork (2) includes the load generated by concrete vibration, and the load generated by personnel and construction; S2: Calculating the total load of the bottom formwork (2) according to the dead load of the bottom formwork (2) and the live load of the bottom formwork (2); S3: Calculating the stress and deflection of the bottom template (2) according to the size of the bottom template (2); S4: judging whether the strength of the bottom template (2) meets the requirements based on the stress and deflection of the bottom template (2).

2. The design method of cast-in-place beam formwork according to claim 1, characterized in that: The bottom mold (2) comprises a cross beam bottom mold (21) and a longitudinal beam bottom mold (22) which are perpendicular to each other, the cross beam bottom mold (21) is mounted on the longitudinal beam bottom mold (22), and both the cross beam bottom mold (21) and the longitudinal beam bottom mold (22) comprise a clamping plate (23), a plurality of secondary beams and a plurality of main beams (25); The design method comprises a load calculation step of the cross beam bottom mold (21) and the longitudinal beam bottom mold (22), including: A1: Calculate the dead load of the clamping plate (23), the secondary beam (24) or the main beam (25), and calculate the live load of the clamping plate (23), the secondary beam (24) or the main beam (25); A2: Calculate the total load of the splint (23), the secondary beam (24) or the main beam (25) according to the dead load and live load of the splint (23), the secondary beam (24) or the main beam (25); A3: Calculating the stress and deflection of the splint (23), the secondary beam (24) or the main beam (25) according to the size of the splint (23), the secondary beam (24) or the main beam (25); A4: Judging whether the strength of the splint (23), the secondary beam (24) or the main beam (25) meets the requirements based on the stress and deflection of the splint (23), the secondary beam (24) or the main beam (25).

3. The design method of cast-in-place beam formwork according to claim 2, characterized in that: A plurality of the main beams (25) are connected by welding or bolts, and a plurality of the secondary beams (24) are connected to the main beams (25) by welding or bolts; the plurality of the main beams (25) are located in a first plane, and the plurality of the secondary beams (24) are located in a second plane, and the first plane is parallel to the second plane and is spaced apart.

4. The design method of cast-in-place beam formwork according to claim 1, characterized in that: The design method further comprises a load calculation step of the side formwork (3), comprising: B1: Calculate the maximum lateral pressure F generated by concrete vibration on the side formwork (3) and the horizontal load F' generated by pouring concrete; B2: Calculate the total load of the side formwork (3) based on the maximum side pressure F generated by concrete vibration on the side formwork (3) and the horizontal load F' generated by pouring concrete.

5. The design method of cast-in-place beam formwork according to claim 3, characterized in that: The calculation formula of the maximum side pressure F is: as well as F=γ c H (2) Where: F-maximum lateral pressure of newly poured concrete on the formwork (KN / m 2 ); γ c - Gravity density of concrete; t0 - initial setting time of fresh concrete, using the formula Where T is the temperature of concrete; V-concrete pouring speed; H-total height from the concrete lateral pressure calculation position to the top surface of the newly poured concrete (m); β1-admixture effect correction factor; β2-concrete slump correction factor; The maximum side pressure F is the smaller value of equation (1) and equation (2).

6. The design method of cast-in-place beam formwork according to claim 3, characterized in that: The maximum value of the horizontal load F' generated by pouring concrete is 6kN / m 2 .

7. The design method of cast-in-place beam formwork according to claim 3, characterized in that: Calculating the total load of the side formwork (3) includes respectively calculating the standard value q' of the side pressure and the design value q of the side pressure, q'=F+F'; q=F×dead load partial factor+F'×live load partial factor; The dead load partial coefficient is 1.2, and the live load partial coefficient is 1.

4.

8. The method for designing a cast-in-place beam formwork according to claim 3, characterized in that: The side formwork (3) comprises a clamping plate (23) and a plurality of channel steels, and the load calculation step of the side formwork (3) further comprises: C1: respectively calculating the stress and deflection of the clamping plate (23) and the stress and deflection of the channel steel; C2: Determine whether the stress and deflection of the clamping plate (23) and the channel steel meet the requirements.

9. The method for designing a cast-in-place beam formwork according to claim 7, characterized in that: The calculation formula of the stress σ of the clamping plate (23) and the channel steel is: σ=M / W In the formula, M is the bending strength and W is the cross-sectional parameter; The calculation formula of the deflection ω of the clamping plate (23) and the channel steel is: In the formula, M is the bending strength, l is the maximum span size of the clamping plate (23) or the channel steel, E is the elastic modulus of the clamping plate (23) or the channel steel, and I is the section moment of inertia of the clamping plate (23) or the channel steel.

10. The method for designing a cast-in-place beam formwork according to any one of claims 1 to 9, characterized in that: The steel pipe pile (1) is provided with a plurality of corbels (4), and the bottom template (2) is erected on the corbels (4); The design method further comprises a load calculation step of the corbel (4), comprising: D1: Calculate the bending stress and shear stress parameters of the bracket (4) respectively; D2: judging whether the strength of the corbel (4) meets the requirements according to the bending stress and shear stress parameters of the corbel (4).

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