I-beam cantilever scaffold for caisson and construction method thereof

Abstract

The present invention relates to the technical field of caisson construction, and specifically to an I-beam cantilever scaffold for caisson and a construction method thereof, comprising a working well, wherein the working well comprises a well wall and a plurality of inner partition walls arranged on the inner side of the well wall, including well wall embedded components, inner partition wall embedded components and cantilever components, wherein the well wall embedded components are used to realize a detachable connection between the cantilever components and the well wall, and the inner partition wall embedded components are used to realize a detachable connection between the cantilever components and the inner partition wall. Compared with the prior art, the present invention designs an I-beam cantilever scaffold for caisson according to the structural characteristics of the working well, and respectively arranges well wall embedded components and inner partition wall embedded components for the well wall and the inner partition wall of the working well, so that the cantilever scaffold can be arranged on the inner side of the well wall (outer pool wall) and on both sides of the inner partition wall in the working well, and is convenient to use, has a stable connection and a novel structure, thereby realizing the application of the cantilever scaffold in the field of caisson construction.

Description

Technical Field

[0001] The invention relates to the technical field of caisson construction, in particular to an I-beam cantilever scaffold for caisson and a construction method thereof. Background Art

[0002] Cantilever scaffolding is a simple facility commonly used in construction. Usually, the bottom of the scaffolding upright is placed on the floor, beam or wall and then tilted outward and fixed. Then, crossbars and scaffolding boards are set up on the upper part to form a construction layer. my country's patent publication number CN207582926U discloses a cantilever scaffolding, which fixes one end of the cantilever support steel beam on the horizontal wall structure layer by bolts, and the cantilever support steel beam is connected to the wall structure layer by steel wire ropes to achieve the fixation of the cantilever support steel beam, solving the problem of cantilever scaffolding being difficult to fix during construction.

[0003] However, in caisson construction, there is no suitable and easy-to-fix cantilever scaffolding structure. Since there is no horizontal structural layer in the working shaft for connecting the cantilever supporting steel beams, the cantilever scaffolding in the prior art cannot be directly applied to caisson construction. Therefore, it is necessary to design a novel I-beam cantilever scaffolding suitable for caisson construction and a construction method thereof. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the prior art and to provide an I-beam cantilever scaffold for caisson and a construction method thereof, which can provide an I-beam cantilever scaffold and a construction method thereof for caisson construction which is easy to use and has a stable connection.

[0005] In order to achieve the above-mentioned purpose, an I-beam cantilever scaffolding for caisson is designed, including a working well, wherein the working well includes a well wall and a plurality of inner partition walls arranged on the inner side of the well wall, including well wall embedded components, inner partition wall embedded components and cantilever components, the well wall embedded components are used to realize a detachable connection between the cantilever components and the well wall, and the inner partition wall embedded components are used to realize a detachable connection between the cantilever components and the inner partition walls.

[0006] A plurality of groups of well wall embedded components are embedded in the well wall, each group of well wall embedded components includes two well wall embedded components located on the same horizontal plane, one end of the well wall embedded component is located in the well wall, the other end of the well wall embedded component extends to the inner side of the well wall, and the other end of the well wall embedded component is provided with a thread for matching with the cantilever component; a plurality of groups of inner partition wall embedded components are embedded in the inner partition wall, each group of inner partition wall embedded components includes two inner partition wall embedded sleeves located on the same horizontal plane, the middle part of the inner partition wall embedded sleeve is used to penetrate the inner partition wall embedded component, and the two ends of the inner partition wall embedded sleeve are connected It passes through the surface of the inner partition wall, and the two ends of the embedded parts of the inner partition wall can extend to the two sides of the inner partition wall respectively, and the two ends of the embedded parts of the inner partition wall are respectively provided with threads for matching with the cantilever components; each of the cantilever components includes a cantilever steel, and one end of the cantilever steel is provided with an end plate, and the end plate is provided with two bolt slot holes located in the same horizontal plane, which can be used to match with the embedded parts of the well wall or the embedded parts of the inner partition wall, and the lower side of the cantilever steel is provided with a triangular support frame, and the triangular support frame is provided with a support plate on the side of the end plate for supporting on the surface of the well wall or the inner partition wall.

[0007] The triangular support frame is in the shape of a right triangle, one right-angled side of the triangular support frame is connected to the lower side of the cantilevered steel, the other right-angled side of the triangular support frame is located on the side close to the end plate, and the support plate is provided on the other right-angled side of the triangular support frame toward the end plate.

[0008] The triangular support frame is connected with a telescopic rod via an internal thread, and the outer end of the telescopic rod is connected with the support plate.

[0009] The connection between the well wall embedded parts and / or the inner partition wall embedded parts and the bolt slot holes provided on the end plate is achieved through the cooperation of bolts and gaskets.

[0010] Connecting fixings are respectively provided between the two well wall embedded parts of each group of well wall embedded parts and between the two inner partition wall embedded sleeves of each group of inner partition wall embedded parts.

[0011] Vertical poles, horizontal poles and sweeping poles of the scaffolding are arranged on the cantilevered member.

[0012] A net bag is hung on the scaffold.

[0013] The present invention also relates to a construction method of a cantilever scaffolding using the I-beam for caisson, comprising the following steps: a. pre-setting well wall embedded parts and inner partition wall embedded casings; b. pouring concrete of the well wall and the inner partition wall; c. installing cantilever steel on the well wall embedded parts and the inner partition wall embedded parts; d. setting up scaffolding uprights, horizontal rods, sweeping rods and wall connecting parts on the cantilever components.

[0014] The step c is specifically as follows: insert the inner partition wall embedded parts into the inner partition wall embedded sleeve, and use a crane to lift the cantilever steel, then align the bolt slot holes at the top of the cantilever steel with the inner partition wall embedded parts and embed them, and add gaskets on the inner partition wall embedded parts outside the bolt slot holes and tighten them with nuts; use a crane to lift the cantilever steel, then align the bolt slot holes at the top of the cantilever steel with the well wall embedded parts and embed them, and add gaskets on the well wall embedded parts outside the bolt slot holes and tighten them with nuts.

[0015] Compared with the prior art, the combined structure of the present invention is simple and feasible, and is easy to install and disassemble. The advantages of the present invention are as follows: according to the structural characteristics of the working well, an I-beam cantilever scaffolding for caisson is designed, and well wall embedded components and inner partition wall embedded components are respectively provided for the well wall and inner partition wall of the working well, so that the cantilever scaffolding can be arranged on the inner side of the well wall (outer pool wall) and on both sides of the inner partition wall in the working well. The cantilever scaffolding is convenient to use, has a stable connection and a novel structure, thus realizing the application of the cantilever scaffolding in the field of caisson construction and being conducive to the rapid and stable construction of the scaffolding in the working well. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of a working well of the present invention in one embodiment;

[0017] Figure 2 is a schematic diagram of the connection of the cantilever member of the present invention in one embodiment;

[0018] Figure 3 is a side view of a cantilever member of the present invention in one embodiment;

[0019] Figure 4 is a schematic diagram of an internal partition wall embedded component of the present invention in one embodiment;

[0020] Figure 5 is a schematic diagram of a well wall embedded component of the present invention in one embodiment;

[0021] Figure 6 is a schematic diagram of pre-embedded inner partition wall pre-embedded sleeves of the present invention in one embodiment;

[0022] Figure 7 yes Figure 6 AA direction schematic diagram;

[0023] Figure 8 yes Figure 6 BB direction schematic diagram;

[0024] Fig. 9 is a schematic diagram of the pre-embedding of the well wall embedded part of the present invention in one embodiment;

[0025] Fig.10 is a schematic diagram of the installation of the present invention at an inner partition wall in one embodiment;

[0026] Fig.11 is a schematic diagram of the installation of the present invention at the well wall in one embodiment;

[0027] Fig.12 is a schematic diagram of erecting a scaffold on a cantilever member in one embodiment;

[0028] Fig.13 is a schematic diagram of the connection between the cantilever member and the well wall in one embodiment;

[0029] Fig.14 is a simplified diagram of force analysis in one embodiment;

[0030] Fig.15 is a schematic diagram of an embodiment in which the apparatus of the present invention is arranged in a working well;

[0031] In the figure: 1. Cantilever steel 2. End plate 3. Bolt slot 4. Pre-embedded casing of inner partition wall 5. Connecting fixings 6. Pre-embedded parts of well wall 7. Inner partition wall 8. Triangular support frame 9. Extension section 10. Telescopic rod 11. Support plate. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings, and the structure and principle of the device and method are very clear to people in the field. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] See also Figure 1 , is a schematic diagram of a working well, and within the outermost circle of the well wall (outer pool wall), there are also several inner partition walls for dividing the area within the well wall into several spaces. This embodiment is to set up a cantilever scaffolding in the working well, and the specific components include well wall embedded components, inner partition wall embedded components and cantilever components. The well wall embedded components are used to achieve a detachable connection between the cantilever components and the well wall, and the inner partition wall embedded components are used to achieve a detachable connection between the cantilever components and the inner partition wall.

[0034] The arrangement of the well wall embedded components is as follows: a plurality of well wall embedded components are embedded on the well wall, each group of well wall embedded components includes two well wall embedded components located on the same horizontal plane, one end of the well wall embedded component is located in the well wall, and the other end of the well wall embedded component extends to the inner side of the well wall, such as Figure 5 As shown, the other end of the well wall embedded part is provided with a thread for matching with the cantilever component.

[0035] The arrangement of the embedded components of the inner partition wall is as follows: a plurality of groups of embedded components of the inner partition wall are embedded in the inner partition wall, each group of embedded components of the inner partition wall includes two embedded sleeves of the inner partition wall located on the same horizontal plane, the middle of the embedded sleeves of the inner partition wall is used to pass through the embedded components of the inner partition wall and the two ends of the embedded sleeves of the inner partition wall are connected to the surface of the inner partition wall, the two ends of the embedded components of the inner partition wall can pass through the two ends of the embedded sleeves of the inner partition wall and extend to the two sides of the inner partition wall, such as Figure 4 As shown, both ends of the inner partition wall embedded part are respectively provided with threads for matching with the cantilevered components.

[0036] like Figure 2 and Figure 3 As shown, each of the cantilever components includes a cantilever steel section. The present embodiment adopts an I-beam. An end plate is welded to the left or right end of the cantilever steel section. The present embodiment is explained by taking the end plate welded to the left end as an example. Two bolt slot holes located in the same horizontal plane are opened on the end plate. The bolt slot holes are arranged symmetrically with respect to the vertical section of the I-beam, and can be used to cooperate with the embedded parts of the well wall or the embedded parts of the inner partition wall. A triangular support frame is welded to the lower side of the cantilever steel section, and a support plate is provided on the side of the triangular support frame toward the end plate for supporting on the surface of the well wall or the inner partition wall. In this embodiment, the triangular support frame is in the form of a right triangle and is made of welded steel. One right-angled side of the triangular support frame is welded to the lower side of the cantilevered steel, and the other right-angled side of the triangular support frame is located on the side close to the end plate, i.e., the left side of this embodiment. The other right-angled side of the triangular support frame is provided with an extension section toward the end plate, i.e., the left side. A through hole is provided at the extension section toward one side of the end plate, and an internal thread is provided in the through hole. A telescopic rod is connected to the through hole through threaded cooperation, and the support plate is welded to the outer end of the telescopic rod. The support plate can be extended and retracted by rotating the telescopic rod. Alternatively, among the three sides of the right-angled triangle support frame, the right-angled side at the top welded to the lower side of the cantilevered steel can be omitted, that is, the cantilevered steel is used as the right-angled side at the top of the right-angled triangle support frame.

[0037] Example 1

[0038] The entire construction process is as follows: standardized production of components → construction preparation → pre-embedded casing of inner partition walls (pre-embedded components of outer pool walls and well walls) → pouring of structural concrete → installation of cantilever steel → erection of steel pipe scaffolding → use of scaffolding → dismantling of scaffolding.

[0039] Specifically, the components are manufactured first. The cantilever steel is made of I-beam with a specification of I23a, a material of Q235-A, and a length of 1.5m. The end plate is made of 200×300×12mm steel plate with a material of Q235-A. Two horizontal slots are opened on the end plate to facilitate the adjustment of the horizontal construction error of the embedded steel casing. The I-beam and the end plate are connected by fillet welds with a weld foot height of 6mm. Both types of embedded parts are made of HRB400 steel bars with a diameter of 28mm that are stripped and rolled.

[0040] During the construction preparation process, scientific calculations are required to ensure that it can meet the force requirements; and subsequent processes are carried out only after samples are made on site and good results are obtained through use.

[0041] The steps for pre-embedding the inner partition wall, pre-embedding the inner partition wall, and pre-embedding the outer pool wall and well wall are as follows. Figure 6-Figure 8 For the pre-buried casing of the inner partition wall, the specifications of the pre-buried casing of the inner partition wall are The length of the embedded sleeve is determined according to the thickness of the well wall, and the center distance between the two embedded sleeves of each group of embedded components of the inner partition wall is ensured to be 100mm, and all embedded iron pipes are kept on the same horizontal plane as much as possible. Preferably, the embedded iron pipes should also be fully fixed in a reliable way to prevent displacement during concrete pouring. For example, a number of connecting steel bars are welded between the two embedded sleeves of each group of embedded components of the inner partition wall as connecting fixings. As for the outer pool wall, that is, the well wall, see Fig. 9 Considering the factors such as the thick wall of the outer pool of the caisson, the excessive length of the through-wall bolts, and the need to fill holes in the later stage to prevent leakage, the outer pool wall directly embeds the well wall embedded parts as the load-bearing support of the cantilever steel.

[0042] For the structural concrete pouring steps, after the above steps are completed, check and verify the installation positions of the embedded components of the well wall and the embedded components of the inner partition wall, and control the deviation within the allowable range. The concrete construction needs to be vibrated and compacted with a vibrating rod to control quality defects. After the concrete is poured, maintenance must be carried out in time in accordance with the specifications to prevent the occurrence of cracks and accelerate the improvement of the early strength of the concrete.

[0043] After that, the cantilever steel can be installed only after the concrete reaches a certain strength (≥75% of the design strength). Before installing the cantilever steel of the inner partition wall, first insert the inner partition wall embedded parts into the inner partition wall embedded casing, use a 25t crane to lift and install the cantilever steel, arrange two workers to cooperate in adjusting the installation position of the cantilever steel, set gaskets between the nuts and the wall, and then align the bolt slots at the top of the cantilever steel with the inner partition wall embedded parts and embed them, and add gaskets to the inner partition wall embedded parts outside the bolt slots and tighten them with nuts. The effect after installation is as follows: Fig.10 Before installing the cantilever steel on the outer pool wall, it is necessary to remove the dirt, slurry and other debris on the outer end of the embedded components of the well wall. The installation method is the same as that of the inner partition wall. For details, see Fig.11 shown.

[0044] Then, you can set up the scaffolding poles, horizontal poles, sweeping poles and wall connecting parts according to the conventional method. For details on the erection of the poles and horizontal poles, see Fig.12 To ensure construction safety, railings and scaffolding boards are set up on the standard scaffolding, and the bottom layer is isolated by hardening the formwork. Net bags are hung every two steps of the scaffolding to prevent objects from falling and injuring people. After the cantilever steel scaffolding is installed, it needs to be tested for safety performance and can only be used after passing the test.

[0045] Finally, after use, the scaffolding should be dismantled in strict accordance with the principle of erecting first and dismantling later, or dismantling later and first. At the same time, the dismantling operation should be carried out from top to bottom, layer by layer, and it is strictly forbidden to operate at the same time. Before dismantling, first comprehensively check the safety and integrity of the scaffolding's fastener connections, pull-in parts, and support systems, and formulate a complete dismantling plan and safety protection measures based on the inspection results, conduct dismantling safety technical briefings for the workers, and clean up the debris and unprocessed garbage on the scaffolding.

[0046] Example 2

[0047] This embodiment provides a related strength calculation of a cantilever scaffolding of an I-beam caisson as follows:

[0048] 1. Scaffolding erection parameters

[0049] The vertical distance of the cantilever scaffolding poles is 1.8m, the horizontal distance of the poles is 1.05m, the step distance of the poles is 1.80m, the calculated height of the double-row scaffolding is 12m, the poles are single vertical tubes, the distance between the inner row and the wall is 0.35m, the large crossbar is parallel to the wall, the small crossbar is perpendicular to the wall, the large crossbar overlaps the poles, and the small crossbar is erected on the large crossbar, all using Φ48×3.5mm steel pipes. The connection between the crossbar and the poles is double fasteners; the anti-slip bearing capacity coefficient of the fasteners is taken as 0.80 during calculation.

[0050] 2. Load parameters

[0051] According to Chapter 4.2 of the "Safety Technical Specifications for Clamped Steel Pipe Scaffolding in Building Construction" (JGJ 130-2011), the standard load values ​​are as follows.

[0052] Constant load parameters: The standard deadweight of the structure per meter of vertical poles is 0.1389kN / m; the standard deadweight of the scaffolding board is 0.350kN / m2; the standard deadweight of the handrail footboard is 0.170kN / m; the safety facilities and safety nets are 0.01kN / m2; the number of scaffolding board layers: 2; the type of scaffolding board: wooden scaffolding board.

[0053] Live load: The standard value of the uniformly distributed construction load is 3.0kN / m2, and the scaffolding is designed as a concrete scaffolding; at the same time, the number of construction layers is considered to be 2 layers; only construction personnel and small equipment such as small vibrators are allowed on the scaffolding, and it is strictly forbidden to stack materials exceeding 3.0kN / m2 (especially horizontal longitudinal reinforcement).

[0054] Wind load: According to the "Building Structure Load Code", in Zhenjiang, Jiangsu Province, the basic wind pressure is 0.400kN / m2, the wind load height variation coefficient is considered to be 1.0 in the suburbs of the city, and the wind load body shape coefficient μs is 0.96; consider the wind load.

[0055] The standard value of scaffolding load is calculated as follows:

[0056] The standard values ​​of dead load include the following:

[0057] (1) The structural deadweight standard per meter of vertical poles (kN / m) is 0.1389;

[0058] N G1 =0.1389×12=1.67kN.

[0059] (2) Standard value of deadweight of scaffolding board (kN / m2). This project uses wooden scaffolding board, and the standard value is 0.35;

[0060] N G2 =0.35×1.8×(1.05+0.5)×2=1.95kN.

[0061] (3) Standard value of deadweight of railing footboard (kN / m). This project uses railing and wooden scaffolding board, and the standard value is 0.17;

[0062] N G3 =0.17×1.8×2=0.61kN.

[0063] (4) The standard value of the deadweight of the hanging safety facilities (safety net) is 0.01 kN / m2;

[0064] N G4 =0.01×1.8×12=0.216kN.

[0065] After calculation, the standard value of constant load N Gk =N G1 +N G2 +N G3 +N G4 =4.45kN.

[0066] Live load standard value N Q =3×1.8×1.05×2 / 2=5.67kN.

[0067] Standard value of wind load w k =μ z ·μ s ·w o =1×0.4×0.96=0.384kN.

[0068] According to the Safety Technical Specifications for Coupler-type Steel Pipe Scaffolding in Building Construction (JGJ 130-2011), the design value of the axial force N of the vertical pole section should be calculated according to the following formula:

[0069] Not considering wind load: N = 1.2N Gk +1.4N Q =1.2×4.45+1.4×5.67=13.28kN.

[0070] 3. Selection of cantilever steel

[0071] The end-welded horizontal I-beam adopts [No. 20a I-beam], where the cantilever length of the horizontal steel beam is 1.5m, the end plate adopts 200mm*300mm*12mm steel plate, the connection between the I-beam and the end plate adopts fillet welding, and the weld leg height is 6mm; a section of Φ25mm round steel with a length of about 5cm is vertically welded on the cantilevered I-beam to place the scaffolding steel pipe.

[0072] 4. Calculation of local and overall force of scaffolding

[0073] The scaffolding is calculated as a ground-type scaffolding. The calculation results of the forces and deflections of the large and small crossbars and vertical poles meet the requirements of the design specifications. The design value of the average vertical axial force transmitted from the upper structure to the vertical poles at the bottom of the scaffolding is: N = 13.28kN; that is, the force between the scaffolding and the I-beam, and the cantilever I-beam and the end anchorage are calculated.

[0074] 5. Calculation of stress stability and safety of cantilevered I-beam

[0075] Design steps: Calculation of welds between I-beam and steel plate; Calculation of shear and tensile resistance of bolts, calculation of bending moment, shear force, deflection and overall stability of I-beams, calculation of anchor length of embedded bolts on outer pool wall, and calculation of compression resistance of concrete shaft wall.

[0076] The axial force N transmitted from the scaffolding to the cantilever beam is 13.28 kN, which is 1.1 times larger than the axial force for the cantilever I-beam safety calculation. The cantilever scaffolding is placed on the I-beam, and the 20a I-beam is used for calculation. Fig.13 and Fig.14 shown.

[0077] (I) Calculation of connection strength

[0078] (1) Calculation of welds between the ends of I-beams and end plates

[0079] The vertical axial force of the double-row scaffolding is N1=N2=13.28KN×1.1=14.61kN;

[0080] I-beam deadweight N3 = 27.9kg / m × 1.5m × 1.2 × 10N / kg = 0.502kN;

[0081] Bending moment M = N1 × (0.35 + 1.4) + N3 × 0.75 = 25.95 kN.m;

[0082] Shear force V = N1 + N2 + N3 = 29.72 kN;

[0083] This bending moment generates tension on the upper flange weld and pressure on the lower flange weld. The tension generated on the upper flange weld is 25.95÷0.2=129.75(KN). The upper flange weld height is 7mm, and the weld length is 90×2=180mm (taking No. 20a I-beam as an example, its upper flange width is 100mm. In actual production, it is required to weld the perimeter between the I-beam and the anchor plate, and the weld height is ≮7mm. According to the welding specification requirements, the weld thickness between the I-beam beam and the steel plate is hf=7mm, and the effective width is he=0.7x7mm=4.9mm). The design value of the tensile strength of the fillet weld is 160N / ㎜2.

[0084] The tensile force that the upper flange weld can withstand is:

[0085] 180×0.7×7×160=141120(N)=141.12KN>129.75KN, safe.

[0086] (2) Calculation of bolt strength

[0087] The tensile force generated by the two embedded bolts is 129.75N. The embedded bolts are Ordinary hot-rolled steel bars are processed by straight thread rolling. According to the provisions of Article 7.2.1 of the "Code for Design of Steel Structures (GB50017)" for calculating the strength of ordinary bolt connections, the tensile bearing capacity of a single bolt is:

[0088]

[0089] Where: f t b is the design value of the tensile strength of the bolt. The calculated tensile strength design value of the steel bar as embedded bolt is 360KN / mm2; d e is the effective diameter of the bolt outside the thread, which is 25 mm in this calculation; N t b=360x3.14x252x0.25=176.625KN.

[0090] The two through-beam bolts can withstand a tensile force of 353.25KN, which is much greater than 129.75KN and is safer.

[0091] According to Article 7.2.1 of the Code for Design of Steel Structures (GB50017), the calculation formula for the shear bearing capacity of ordinary bolts is:

[0092] Where: f v b is the design value of the shear bearing capacity of the bolt. The shear bearing capacity of the steel bar is 0.5 of its tensile design strength. In order to ensure the calculation result is on the safe side, f is selected in this calculation. v b 140KN / mm2; N v b =2x140x3.14x252x0.25=137.2KN;

[0093] From this, we can see that the shear bearing capacity of the two bolts is 137.2KN, which is much larger than 25.95KN, which means that the structure is safe.

[0094] (II) Calculation of I-beam:

[0095] Since the longitudinal horizontal bar at the bottom of the steel pipe scaffolding upright has the function of preventing the lateral displacement of the I-beam cantilever beam, it can be regarded as a lateral support point. The distance between the lateral support points is 1050mm, and the ratio of the width of the upper flange of the 20a I-beam 100mm is 10.5<16. According to the steel structure design code, it is not necessary to calculate the strength and overall stability of the cantilever beam. However, the stiffness of the cantilever beam should be calculated. The stiffness calculation of the 20a I-beam cantilever beam in this method is as follows:

[0096] Since the distance between the inner scaffolding pole and the outer side of the structural edge beam is 350mm, and the distance between the inner and outer poles is 1050mm, the distance between the outer pole and the outer side of the structural edge beam is 1400mm, and the total length of the cantilever beam is 1500mm. Checking the cantilever beam table for structural static calculation, we can know:

[0097]

[0098] 1) The deflection of the inner pole is:

[0099] W1=(N1*3502*1500 / 6EI)*(3-350 / 1500).

[0100] 2) The deflection of the external pole is:

[0101] W2=(N1*14002*1500 / 6EI)*(3-1400 / 1500).

[0102] The moment of inertia of No. 20a I-beam is I = 2170.7cm4 = 21.70x106mm4; elastic modulus E = 2.06×105, and the axial force of the vertical rod is F = 10.93KN = 10930N. Substituting into the above formula, we can calculate: W1 = 0.207mm, W2 = 2.476mm.

[0103] According to Table 5.1.8 of the "Safety Technical Specifications for Coupler-Type Steel Pipe Scaffolding (JGJ130-2011)", the allowable deflection W of the cantilever steel beam of the steel cantilever scaffolding is: [w] = l / 400, where l is the span of the cantilever member and for the cantilever rod it is twice the cantilever length.

[0104] That is, the total deflection W = W1 + W2 = 2.683 mm < [w] = 3000 / 400 = 7.5 mm, which meets the requirement.

[0105] (III) Calculation of the length of the anchor bolts on the outer pool wall

[0106] Determine the length of the embedded anchor steel bars according to Chapter 8.3 Anchorage of Steel Bars in the Code for Design of Concrete Structures (GB50010-2011).

[0107]

[0108] l a =ψ a / l ao

[0109] Where: l ao ——Basic anchorage length of tension reinforcement;

[0110] l a - Anchorage length of tension reinforcement;

[0111] f py ——design value of tensile strength of steel bars;

[0112] f t ——The design value of concrete axial tensile strength shall be adopted in accordance with the relevant provisions of the concrete structure design code;

[0113] d——nominal diameter of steel bar;

[0114] α——shape coefficient of anchor reinforcement;

[0115] ψ a ——Anchorage length correction factor.

[0116] The selected steel bar is HRB400Φ28, the design value of the tensile strength of the steel bar is 360N / mm2, the concrete grade used for casting the shaft wall beam is C35, the design value of the axial tensile strength is 1.57N / mm2, α=0.13, so: la=0.13×360 / 1.57×0.028=0.835m.

[0117] Two bolt holes are reserved for each steel plate, and HRB400Φ28 threaded steel bars are connected after the bolts, with a length of 1m. The tensile strength of HRB400Φ28 threaded steel bars is: 360MPa, that is: F = 360×3.14×282x0.25 = 221.56kN. The bearing capacity of a group of embedded threaded steel bars is Ftotal = F×2 = 221.56x2 = 443.12KN. It is much larger than the external tension of 105.72KN. It meets the bearing capacity requirements.

[0118] (IV) Calculation of concrete compressive strength

[0119] A 200mm×300mm steel plate is used between the cantilever beam and the shaft wall to protect the shaft wall and maximize the effective contact area of ​​the steel plate. The effective contact area S=200×300=60000mm2, the shaft wall concrete is C35P8, the caisson sinks not less than 70% of the design strength, and the shaft wall concrete strength is at least 25MPa during the heightening process of the caisson structure. P=105.72x1000 / 60000=1.762MPa<25MPa. The shaft wall meets the compressive strength.

Claims

1. A cantilever scaffolding with I-beam for caisson, comprising a working well, wherein the working well comprises a well wall and a plurality of inner partition walls arranged on the inner side of the well wall, characterized in that It includes a well wall embedded component, an inner partition wall embedded component and a cantilever component, wherein the well wall embedded component is used to realize a detachable connection between the cantilever component and the well wall, and the inner partition wall embedded component is used to realize a detachable connection between the cantilever component and the inner partition wall; A plurality of groups of well wall embedded components are embedded in the well wall, each group of well wall embedded components includes two well wall embedded components located on the same horizontal plane, one end of the well wall embedded component is located in the well wall, the other end of the well wall embedded component extends to the inside of the well wall, and the other end of the well wall embedded component is provided with a thread for matching with the cantilever component; A plurality of groups of embedded components for the inner partition wall are embedded in the inner partition wall, each group of embedded components for the inner partition wall includes two embedded sleeves for the inner partition wall located on the same horizontal plane, the middle of the embedded sleeves for the inner partition wall is used to penetrate the embedded components for the inner partition wall and the two ends of the embedded sleeves for the inner partition wall are connected to the surface of the inner partition wall, the two ends of the embedded components for the inner partition wall can extend to the two sides of the inner partition wall respectively, and the two ends of the embedded components for the inner partition wall are respectively provided with threads for matching with the cantilever components; Each of the cantilevered components comprises a cantilevered steel, one end of which is provided with an end plate, on which two bolt slots located in the same horizontal plane are provided, which can be used to cooperate with the embedded parts of the well wall or the embedded parts of the inner partition wall, and a triangular support frame is provided on the lower side of the cantilevered steel, and a support plate is provided on the side of the triangular support frame facing the end plate, which is used to support the surface of the well wall or the inner partition wall; The triangular support frame is in the shape of a right triangle, one right-angled side of the triangular support frame is connected to the lower side of the cantilevered steel, the other right-angled side of the triangular support frame is located on the side close to the end plate, and the support plate is provided on the other right-angled side of the triangular support frame toward the end plate; The triangular support frame is connected with a telescopic rod via an internal thread, and the outer end of the telescopic rod is connected with the support plate.

2. The I-beam cantilever scaffold for caisson as claimed in claim 1, characterized in that The connection between the well wall embedded parts and / or the inner partition wall embedded parts and the bolt slot holes provided on the end plate is achieved through the cooperation of bolts and gaskets.

3. The I-beam cantilever scaffold for caisson as claimed in claim 1, characterized in that Connecting fixings are respectively provided between the two well wall embedded parts of each group of well wall embedded parts and between the two inner partition wall embedded sleeves of each group of inner partition wall embedded parts.

4. The I-beam cantilever scaffold for caisson as claimed in claim 1, characterized in that Vertical poles, horizontal poles and sweeping poles of the scaffolding are arranged on the cantilevered member.

5. The I-beam cantilever scaffold for caisson as claimed in claim 4, characterized in that A net bag is hung on the scaffold.

6. A construction method using the I-beam cantilever scaffolding for caisson as claimed in claim 1, characterized in that The steps include: a. Pre-install the embedded parts of the well wall and the embedded casing of the inner partition wall; b. Carry out concrete pouring of well wall and inner partition wall; c. Install cantilever steel on the embedded components of the well wall and the embedded components of the inner partition wall; d. Set up scaffolding uprights, horizontal poles, sweeping poles and wall connectors on the cantilevered components.

7. A construction method as claimed in claim 6, characterized in that The step c is specifically as follows: inserting the inner partition wall embedded part into the inner partition wall embedded sleeve, and using a crane to lift the cantilever steel, and then aligning the bolt slot hole at the top of the cantilever steel with the inner partition wall embedded part, and adding a gasket to the inner partition wall embedded part outside the bolt slot hole, and tightening it with a nut; Use a crane to lift the cantilever steel, then align the bolt slot holes at the top of the cantilever steel with the embedded parts of the well wall and embed them, add gaskets to the embedded parts of the well wall outside the bolt slot holes, and tighten them with nuts.

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