Upward-pulling formwork erecting construction method for concrete cantilever structure

Abstract

The invention discloses a concrete cantilever structure pull-up formwork construction method which is characterized by comprising the following steps: load calculation and component model selection; pre-burying the U-shaped bolts; pre-burying the upper-section pull rod; i-shaped steel end connecting plates are welded, and double-layer angle steel connecting plates are welded to the cantilever ends of the I-shaped steel; i-shaped steel cantilever girders are installed; assembling a pull rod system; the pull rods are fastened and leveled with a system, the two pull rods are synchronously fastened, the double rods are ensured to simultaneously advance and retreat during adjustment of an adjusting device, and a level gauge is used for observation and leveling after initial adjustment; the formwork frame and the safety enclosure are installed; pull rod pre-tensioning and deflection monitoring are carried out, pre-tension force is applied through an adjusting device, the deflection of the cantilever end is detected, monitoring points are arranged, and a deformation early warning mechanism is established; regulating and controlling concrete pouring; and removing the mold and recycling. The overhanging structure is high in anti-overturning capacity and suitable for large-span and special-shaped overhanging structures, and the safety is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high cantilever structure formwork support construction, more particularly, to a concrete cantilever structure upward pulling formwork construction method. BACKGROUND

[0002] With the continuous development of building technology, the design of modern buildings is increasingly complex and challenging, and special structural forms such as large-span cantilever structures and irregular facades frequently appear in architectural design. The on-site construction of such structures has problems such as complex process and long construction period, and the traditional ground-supported scaffold support system has been difficult to meet the construction needs.

[0003] When the traditional ground-supported scaffold supports the cantilever structure, the scaffold needs to be erected layer by layer from the ground, which not only consumes a large amount of steel pipes, fasteners and other materials, resulting in high material costs, but also significantly prolongs the construction period due to the complicated erection process. At the same time, the cantilever end is prone to large deflection under load, making it difficult to control the deflection, which can easily affect the dimensional accuracy of the concrete structure and cause structural quality problems. In addition, for complex facade structures such as irregular curved surfaces and large-span cantilevers, the stability of the traditional ground-supported scaffold is poor, and the safety of the construction personnel is low, posing significant safety risks. SUMMARY

[0004] In view of the problems in the prior art, the present application aims to provide a concrete cantilever structure upward pulling formwork construction method, which has strong anti-overturning ability, is suitable for large-span and irregular cantilever structures, and significantly improves safety.

[0005] The present application adopts the following technical solutions:

[0006] A concrete cantilever structure upward pulling formwork construction method, comprising the following steps:

[0007] S1, load calculation and component selection

[0008] According to the parameters of the cantilever structure, the total construction load is calculated, and the I-beam cantilever main beam and the inclined rod are selected;

[0009] S2, U-bolt pre-burying

[0010] Before pouring the cantilever support layer concrete, the U-bolts are pre-buried to control the positioning error and the exposed length of the bolts, and the coordinates are rechecked and fixed after pre-burying;

[0011] S3, pre-burying of upper segment pull rod

[0012] Before pouring the upper frame beam of the cantilever support layer, the round steel upper segment pull rod is pre-buried to control the horizontal projection position of the pull rod and the length of the exposed end thread, and the verticality is accepted after pre-burying;

[0013] S4, welding of I-beam end connecting plate

[0014] Welding double-layer angle steel connecting plate at the end of I-beam cantilever;

[0015] S5, I-beam cantilever girder installation

[0016] After the strength of the cantilever support layer concrete is ≥75% of the design value, the tower crane is used to hoist the I-beam to the designed position, fixed by U-shaped bolt double backing plate, the gap between the I-beam and the structure is filled with wood batten, and the bolt fastening torque is controlled;

[0017] S6, tension rod system assembly

[0018] Two round steel tension rods are used to connect the I-beams, each tension rod is divided into upper and lower sections, the lower section of the tension rod is locked by double nuts after passing through the connecting plate anchor hole, and the other end is connected with the upper section of the tension rod through the adjusting device, and double nuts are provided at all nodes;

[0019] S7, tension rod fastening and system leveling

[0020] The two tension rods are fastened synchronously, and the adjusting device is adjusted to ensure that the two rods advance and retreat simultaneously. After initial adjustment, the leveling is observed by using a level;

[0021] S8, formwork frame and safety enclosure installation

[0022] The vertical rods, horizontal rods, formwork and steel bars are installed on the cantilever platform, the safety net is fully laid on the upper part of the I-beam and fixed, wood batten is arranged on the upper part of the safety net, anti-slip limit block, safety mesh and skirting board are provided on the frame body;

[0023] S9, tension rod pre-tensioning and deflection monitoring

[0024] The pre-tensioning force is applied through the adjusting device, the deflection of the cantilever end is detected, the monitoring points are set, and the deformation early warning mechanism is established;

[0025] S10, concrete pouring control

[0026] The concrete is poured symmetrically in layers, and the deflection is monitored once for every 1m³ of concrete poured;

[0027] S11, form removal and recycling

[0028] After the concrete strength is ≥100% of the design value, the formwork frame, tension rod and adjusting device, and I-beam are removed in sequence, the I-beam is hoisted on the ground with an isolation area, and the component is recycled after passing the detection.

[0029] Further, the total construction load is calculated by the formula S=1.2Q1+1.4Q2, the maximum axial force and maximum bending moment are obtained through mechanical analysis, the I-beam cantilever girder is selected according to the Steel Structure Design Standard GB 50017, and the formula N / A≤[σ] is used to select the inclined tension rod;

[0030] In the formula, Q1 is a constant load, including the structure and formwork frame self weight; Q2 is a live load, including the construction live load, and is obtained by calculating the maximum axial force Nmax and the maximum bending moment Mmax from the load S value through mechanical analysis;

[0031] In the formula, N is the axial tension design value of the diagonal pull rod; A is the cross-sectional area of the diagonal pull rod; and σ is the tensile strength design value of the diagonal pull rod.

[0032] Further, in step S2, a Φ20mm U-shaped bolt is embedded, the positioning error is ≤5mm, and the exposed length of the bolt is ≥100mm. After embedding, the coordinates are rechecked and displacement is prevented.

[0033] Further, in step S3, an HPB300 grade round steel upper segment pull rod is embedded, the diameter of the upper segment pull rod is ≥20mm; the horizontal projection is aligned with the lower I-beam, and the center point is 28±8mm away from the edge of the I-beam; the threaded length of the exposed end of the pull rod is ≥50mm; after embedding, the perpendicularity is accepted, and the perpendicularity deviation is ≤2°.

[0034] Further, in step S5, each I-beam cantilever main beam has at least 2 fixed points, and the bolt torque is ≥100N·m.

[0035] Further, in step S8, a safety net is fully laid on the upper part of the I-beam cantilever main beam, and is connected with each other by not less than 18# iron wire after being bound tightly with the I-beam; wooden boards are arranged on the upper part of the safety net in a direction perpendicular to the I-beam, the distance between the wooden boards is not more than 200mm, and the wooden boards are bound tightly with the I-beam by not less than 18# iron wire; templates are arranged on the upper part of the wooden boards and are connected with the wooden boards by iron nails; anti-skid limiting blocks are welded at the bottom of the stand poles of the frame body, the stand poles on the outside of the frame body are connected with the inner frame body, the stand poles are spaced apart by 1.5m from the working surface, the stand poles are spaced apart by the same distance as the frame body, 2 horizontal cross bars are additionally arranged at each step distance of the frame body, a safety mesh net is arranged on the outside, and a kick plate is arranged at the bottom.

[0036] Further, in step S9, the deflection of the cantilever end is detected by using a level meter, and is adjusted to ≤L / 500; a precast tower scale label is arranged at the cantilever end, and one monitoring point is arranged every 5m; the initial elevation is recorded, a deformation early warning mechanism is established, and the warning value is L / 400.

[0037] Beneficial effects

[0038] Cost and construction period optimization: the upper pulling type adjustable support system is used to replace the traditional floor-mounted scaffold, the amount of steel pipes is reduced, the construction period is shortened, and the comprehensive construction cost is significantly reduced;

[0039] Structural precision guarantee: the pull rod tension is dynamically compensated by the adjusting device, the cantilever end deflection is actively controlled, and the concrete structure size achieves a very high qualified rate;

[0040] Safety improvement: The I-beam is anchored by U-shaped bolts, which has strong anti-overturning ability, is suitable for large-span and special-shaped cantilever structures, and significantly improves construction safety.

[0041] Strong versatility: The support system is lightweight and adjustable, suitable for cantilever structures with different parameters, especially for complex facade (such as special-shaped curved surface) construction scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The U-shaped bolt pre-buried schematic diagram of an embodiment of the present application;

[0043] Figure 2 The schematic diagram of the upper layer pull rod pre-buried in the frame beam of an embodiment of the present application;

[0044] Figure 3 The schematic diagram of the I-beam cantilever end connection angle steel welding of an embodiment of the present application;

[0045] Figure 4 The schematic diagram of the I-beam cantilever main beam installation of an embodiment of the present application;

[0046] Figure 5 The Figure 4 Cross-sectional view;

[0047] Figure 6 The schematic diagram of the upper and lower two sections of pull rod connection of an embodiment of the present application;

[0048] Figure 7 The schematic diagram of the support frame erection of an embodiment of the present application. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0050] As shown in the figure, the present application discloses a concrete cantilever structure upper pulling formwork construction method, comprising the following steps:

[0051] Step S1, according to the cantilever structure, first calculate the construction load, calculate the total construction load (in the formula, Q1 is the constant load, including structure, formwork frame self weight, etc.; Q2 is the live load, including construction live load, etc.) through the formula S = 1.2Q1 + 1.4Q2. The maximum axial force Nmax and the maximum bending moment Mmax can be obtained by mechanical analysis and calculation from the load S value.

[0052] Then, the horizontal cantilever I-beam main beam is calculated and selected according to the "Steel Structure Design Standard GB 50017". The cross-section of the tie rod is selected by calculating N / A≤[σ] (where N is the design value of the axial tensile force of the tie rod; A is the cross-sectional area of ​​the tie rod; σ is the design value of the tensile strength of the tie rod), and a tie rod of appropriate size is selected.

[0053] Step S2, as follows Figure 1 As shown, U-bolt 1 is pre-embedded in the cantilever support layer. Before the concrete is poured for the cantilever support layer, Φ20mm U-bolt 1 is pre-embedded according to the design drawings, with a positioning error ≤5mm. The exposed length of the bolt is ≥100mm. After pre-embedding, the coordinates are checked and fixed to prevent displacement.

[0054] Step S3, as follows Figure 2 As shown, before the upper frame beam of the cantilever support layer is poured, four upper tie rods of HPB300 grade round steel (Φ≥20mm) are pre-embedded; the horizontal projection is aligned with the lower I-beam, and the center point is 28±8mm from the edge of the I-beam; the exposed end of the tie rod has a thread length ≥50mm, and the verticality is inspected after pre-embedding (deviation ≤2°).

[0055] Step S4, as follows Figure 3 As shown, the connecting plate at the cantilever end of the I-beam 2 is welded, and the double-layer angle steel 3 with dimensions of 100×80×10mm is welded to the cantilever end of the I-beam. The opening diameter is 2mm larger than that of the tie rod, and it is used to connect the cantilever main beam of the I-beam and the tie rod.

[0056] Step S5, as follows Figure 4 and Figure 5 As shown, the I-beam cantilever main beam is installed, and the concrete strength of the cantilever support layer is ≥75% of the design value (verified by test blocks under the same conditions). The tower crane hoists the I-beam to the design position, and the U-bolts 1 are tightened with double washers (≥2 fixing points per beam); the gap between the I-beam 2 and the structure is filled with wooden blocks 5, and the bolt torque is ≥100 N·m (tested with a torque wrench).

[0057] Step S6, as follows Figure 6 As shown, the tie rod system is assembled. The I-beam cantilever main beam is connected by two round steel tie rods, each of which is divided into upper and lower sections. When installing the lower tie rod 6 (threaded at both ends), one end should pass through the anchoring hole of the angle steel connecting plate welded on the I-beam cantilever main beam and be locked with double nuts (exposed threads ≥ 2). The other end is connected to the upper tie rod 4 through an adjustment device. All connections are bolted connections with double nuts.

[0058] Step S7, after the pull rod is connected, the fastening adjustment is started. When the pull rod is fastened, it must be ensured that the two pull rods are tightened at the same time. When the adjusting device is adjusted, it should be ensured that the two pull rods are advanced and retreated at the same time, and the two pull rods are uniformly stressed. After the initial adjustment of the cantilever system is completed, the entire cantilever system is observed and leveled by using a level, and the parts with deviations are adjusted to ensure that the entire system is balanced.

[0059] Step S8, as shown in Figure 7 , after the pull rod adjustment is completed, the vertical rods and horizontal rods can be installed on the cantilever platform according to the general formwork support system, and the formwork and steel bars are installed. The upper part of the I-beam cantilever main beam is fully paved with safety netting, and is connected with the I-beam by using not less than 18# iron wire (diameter greater than 1.2mm); the wood boards are arranged vertically to the I-beam direction on the upper part of the safety net, the spacing between the wood boards is not greater than 200mm, and the wood boards need to be bound with the I-beam by using not less than 18# iron wire; the formwork is arranged on the upper part of the wood board and is connected with the wood board by using iron nails. The anti-skid limiting block is welded at the bottom of the vertical rod of the frame body, the vertical rod outside the formwork frame is connected with the inner formwork frame, the overworking surface is 1.5m, the spacing between the vertical rods is the same as that of the formwork frame, the step distance is the same as that of the formwork frame, two horizontal rods are additionally arranged at each step distance of the frame body, the safety mesh net is arranged outside, and the skirting board is arranged at the bottom to avoid the sliding of articles.

[0060] Step S9, the pull rod is pre-tensioned, the symmetrically tightened nuts are adjusted by the adjusting device, the pre-tensioning force is 80% of the design value; the deflection of the cantilever end is detected by using a level, and is adjusted to ≤L / 500 (such as 3.6m cantilever limit value 7.2mm). The cantilever end is provided with a prefabricated tower scale label, and one monitoring point is arranged every 5m; the initial elevation is recorded, and a deformation early warning mechanism is established (warning value=L / 400).

[0061] Step S10, concrete pouring and dynamic adjustment, symmetrically layered pouring, real-time monitoring and adjustment, deflection is monitored once every 1m³ of poured concrete; when the deviation reaches 90% of the warning value, the pouring is temporarily stopped, the adjusting nuts are tightened to compensate the tension (adjusting amount ≤2mm / time); the maximum allowable deflection is ≤L / 400 (final control value).

[0062] Step S11, form removal and turnover recovery, the concrete strength is ≥100% of the design value (verified by the same condition test block), and the frame body is removed. The formwork frame body is removed first → the adjusting device nuts are loosened → the I-beam is finally removed; a 6m isolation area is arranged on the ground, and the I-beam is hoisted by the tower crane (stop working in the wind of more than six levels). The I-beam, the pull rod and the adjusting device are detected and then recycled (limit deformation ≤L / 1000).

[0063] The above is only the preferred specific embodiment of the present application; however, the protection scope of the present application is not limited to this. Any person skilled in the art can make equivalent replacement or change according to the technical solution and the improvement concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A construction method of a concrete cantilever structure pull-up formwork, characterized in that, Comprise the following steps: S1, load calculation and component selection According to the cantilever structure parameters, calculate the construction total load, select the I-beam cantilever main beam and inclined rod components; S2, U-shaped bolt pre-burying Before pouring the cantilever support layer concrete, pre-bury U-shaped bolt, control positioning error and bolt exposed length, recheck coordinates after pre-burying and fix; S3, pre-burying upper segment rod Before pouring the upper layer frame beam of cantilever support layer, pre-bury round steel upper segment rod, control rod horizontal projection position and exposed end thread length, accept verticality after pre-burying; S4, I-beam end connecting plate welding Weld double-layer angle steel connecting plate at I-beam cantilever end; S5, I-beam cantilever main beam installation After the cantilever support layer concrete strength ≥75% design value, hoist I-beam to design position by tower crane, adopt U-shaped bolt double-pad plate fixation, fill I-beam and structure gap with wood square, control bolt fastening torque; S6, rod system assembly Adopt two round steel rods to connect I-beam, each rod is divided into upper and lower segments, lower segment rod one end passes connecting plate anchoring hole and is locked by double-nut, the other end is connected with upper segment rod through adjusting device, all nodes are provided with double-nut; S7, rod fastening and system leveling Fasten two rods synchronously, ensure double-rod same advance and retreat when adjusting device adjusts, observe and level after initial adjustment by using level; S8, formwork frame and safety enclosure installation Install vertical rod, horizontal rod, formwork and steel bar on cantilever platform, fully lay safety net on I-beam upper part and fix, arrange wood square on safety net upper part, frame body is provided with anti-slip limiting block, safety mesh and skirting board; S9, rod pre-tensioning and deflection monitoring Apply pre-tensioning through adjusting device, detect cantilever end deflection, set monitoring point and establish deformation early warning mechanism; S10, concrete pouring control Pour concrete symmetrically in layers, monitor deflection once per 1m³; S11, formwork removal and recovery After concrete strength ≥100% design value, remove in sequence of "formwork frame body→rod and adjusting device→I-beam", hoist I-beam on ground isolation area, recycle after component detection is qualified.

2. The construction method of claim 1, wherein, Adopt formula S=1.2Q1+1.4Q2 to calculate construction total load, obtain maximum axial force and maximum bending moment through mechanical analysis, select I-beam cantilever main beam according to "Steel Structure Design Standard GB 50017", select inclined rod components by formula N / A≤[σ]; In formula, Q1 is constant load, including structure and formwork frame self-weight; Q2 is live load, including construction live load, maximum axial force Nmax and maximum bending moment Mmax are obtained by calculating load S value through mechanical analysis; In formula, N is axial tension design value of inclined rod; A is cross section area of inclined rod; σ is tensile strength design value of inclined rod.

3. The construction method of claim 1, wherein, In step S2, pre-bury Φ20mm U-shaped bolt, positioning error ≤5mm, bolt exposed length ≥100mm, recheck coordinates after pre-burying and fix to prevent displacement.

4. The construction method of claim 1, wherein, In step S3, pre-bury HPB300 grade round steel upper segment rod, upper segment rod diameter ≥20mm; horizontal projection is aligned with lower I-beam, center point is 28±8mm away from I-beam edge; rod exposed end thread length ≥50mm, accept verticality after pre-burying, verticality deviation ≤2°.

5. The construction method of claim 1, wherein, In step S5, each I-beam cantilever main beam has at least 2 fixing points, and the bolt torque is ≥100 N·m.

6. The construction method of claim 1, wherein, In step S8, the upper part of the I-beam cantilever main beam is fully paved with a safety net, which is connected with each other by not less than 18# iron wire and then bound with the I-beam; wood batten is arranged on the upper part of the safety net perpendicular to the direction of the I-beam, the spacing of the wood batten is not more than 200 mm, the wood batten is bound with the I-beam by not less than 18# iron wire; formwork is arranged on the upper part of the wood batten and connected with the wood batten by iron nails; anti-skid limiting blocks are welded at the bottom of the vertical rods of the frame body, the vertical rods outside the formwork frame are connected with the inner formwork frame, the working surface is 1.5 m, the spacing of the vertical rods is the same as that of the formwork frame, the step distance is the same as that of the formwork frame, two horizontal crossbars are additionally arranged at each step distance of the frame body, safety mesh is arranged outside, and kick plates are arranged at the bottom.

7. The construction method of claim 1, wherein, In step S9, the deflection of the cantilever end is detected by a level instrument, and is adjusted to ≤L / 500; a precast tower scale label is arranged at the cantilever end, and one monitoring point is arranged every 5 m; The initial elevation is recorded, and a deformation early warning mechanism is established, and the warning value is L / 400.

Images