Method for integral hoisting of large-diameter variable-circular cross-section steel bars

Abstract

This application discloses a method for hoisting large-diameter variable-circular cross-section steel bars as a whole. It utilizes an adjustable disc-shaped lifting tool and makes reasonable use of the shape and deformation characteristics of the large-diameter variable-circular cross-section steel bar segments. After connecting the main bars of the arc segment with smaller deformation, the main hook is unloaded after most of the load is removed, allowing the steel bar segment to return to its shape. Then, the main bars of the straight segment with larger deformation are connected. In this way, there is no need to take other measures to reduce the deformation of the steel bar segments during hoisting, such as adding reinforcing rings or increasing the stiffness of the stiffening frame, which would increase the overall hoisting weight. This saves materials and speeds up the connection of the steel bars.

Description

Technical Field

[0001] This application relates to the field of bridge construction, and in particular to a method for integral hoisting of large-diameter variable-circular cross-section steel bars. Background Technology

[0002] The hoisting of large-diameter steel bar segments requires controlling the deformation of the steel bars after hoisting. For steel bar segments with a centrally symmetrical cross-section, the deformation is relatively easy to control using existing technology. However, it is more difficult to control the deformation of steel bar segments with larger diameters and non-centrally symmetrical cross-sections after hoisting. This is mainly because the deformation characteristics and amount of deformation of steel bar segments with larger diameters and non-centrally symmetrical cross-sections during overall hoisting are different from those under conventional conditions. Currently, there are no methods or corresponding special hoisting tools for hoisting steel bar segments with large diameters of 9-18m and circular (elliptical) cross-sections in towers (piers). If internal bracing structures or reinforcing rings are set up for steel bar segments according to conventional construction methods, the deformation improvement effect is poor due to the large cross-sectional size of the steel bar segments, resulting in a low qualification rate of the steel bar protective layer and increasing the total hoisting weight. This makes it difficult to connect the steel bar segments and affects construction efficiency. Summary of the Invention

[0003] The purpose of this application is to at least partially improve the shortcomings of the prior art and provide a simple and effective method for hoisting large-diameter variable-circular cross-section steel bars as a whole.

[0004] To achieve the above technical objectives, the technical solution adopted in this application is as follows:

[0005] A method for integral hoisting of large-diameter variable-circular cross-section steel bars, comprising the following steps:

[0006] Bind the reinforcing steel segments according to the preset circular cross-sectional profile;

[0007] Based on the deformation of the steel bar segments after lifting, set up lifting points and connect corresponding lifting equipment;

[0008] The steel bar segment was lifted as a whole to the docking position using the lifting equipment.

[0009] After connecting the first main reinforcement at the arc segment, the lifting device is unloaded for the first time;

[0010] After connecting the second main reinforcement bar at the straight section, remove the lifting equipment.

[0011] Preferably, the step of binding the reinforcing bar segments according to the preset circular cross-sectional profile includes:

[0012] Pre-set positioning teeth according to the connection requirements of the top and bottom openings of the steel bar segments;

[0013] The positioning toothed plate is used to bind the steel bar segments;

[0014] The steel reinforcement segment includes a stiffening skeleton, most of the main reinforcement bars, and stirrups connecting the main reinforcement bars.

[0015] Furthermore, after removing the lifting equipment, the remaining reinforcing bars are tied.

[0016] Alternatively, the lifting points can be configured to be non-coplanar to adapt to the deformation of the reinforcing bar segments.

[0017] Alternatively, the lifting point may be located on the main reinforcing bar.

[0018] In one possible implementation, the lifting device includes a coplanar upper structure and a non-coplanar lower structure. The lower structure includes a plurality of movable hangers suspended below the upper structure, and the movable hangers correspond one-to-one with the lifting points.

[0019] Alternatively, the movable hanger is sleeved and connected to the upper structure via an adjustable connector to adjust the height and planar position of the movable hanger.

[0020] Furthermore, the first unloading of the lifting device includes unloading a load of 60% to 85% of the total load.

[0021] Compared with existing technologies, this application has the following advantages:

[0022] (1) The method of this application makes reasonable use of the shape and deformation characteristics of the large-diameter variable-circular cross section steel bar segments. After connecting the main bars of the arc segment with smaller deformation, after unloading most of the load on the main hook, the steel bar segments are allowed to recover their shape. Then, the main bars of the straight segment with larger deformation are connected. In this way, there is no need to take other measures to reduce the deformation of the steel bar segments during hoisting, such as adding reinforcing rings or increasing the stiffness of the stiffening frame to increase the overall hoisting weight. This saves materials and speeds up the connection of steel bars.

[0023] (2) The method of this application uses prefabricated positioning toothed plates to tie the steel bar segments, which can accurately control the steel bar segments with variable cross sections, reduce human error, and improve construction quality.

[0024] (3) The lifting device used in the method of this application has a double-layer structure. The upper layer is stable and the lower layer is adjustable. It can adapt to the calculated deformation at various points of the cross section of the steel bar segment and make precise adjustments to the position and height of the lifting point, effectively improving the deformation of the whole lifting of the steel bar segment with large diameter variable round cross section. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the cross-section of the reinforcing bar segment applicable to the embodiments of this application.

[0026] Figure 2 This is a top view schematic diagram of an embodiment of the adjustable disc-shaped lifting device of this application.

[0027] Figure 3 This is a side view of an embodiment of the adjustable disc-shaped lifting device of this application.

[0028] Figure 4 This is a schematic diagram of the movable hanger structure in an embodiment of this application.

[0029] Figure 5 for Figure 4 A side view structural diagram.

[0030] Figure 6 This is a structural schematic diagram of the first movable hanger of this application.

[0031] Figure 7 This is a structural schematic diagram of the second movable hanger of this application.

[0032] Figure 8 This is a physical image of the positioning toothed plate of this application.

[0033] Figure 9 This is a field photo showing the suspended state of the large-diameter variable-circular cross-section steel bar segment during the overall hoisting of this application. Detailed Implementation

[0034] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] The cross-section of a bridge tower changes from a circular cross-section to a variable circular cross-section and then back to a circular cross-section from bottom to top. Furthermore, the overall radial dimension of the tower decreases and then increases again. Therefore, different assembly heights of the tower correspond to different sizes and shapes of the reinforcing steel segments. The deformation of the variable circular cross-section segments during overall hoisting is particularly prominent. This is mainly due to the high flexibility of individual reinforcing bars, and the large diameter of the resulting reinforcing cage, making it difficult to significantly strengthen the overall rigidity of the segments through the formation of a three-dimensional structure. Additionally, the variable circular cross-section segments have curved arc sections and arc-shaped top and bottom planes. Without additional reinforcing structures, the deformation of the top and bottom arc sections increases after hoisting the entire segment, increasing the difficulty of connecting the upper and lower reinforcing steel segments after hoisting. Therefore, this application addresses the deformation of large-diameter variable circular cross-section reinforcing steel segments by designing an overall hoisting method and an adjustable disc-shaped lifting device 2 for use. This application is applicable to the overall hoisting process of large-diameter variable circular cross-section reinforcing steel segments.

[0036] refer to Figure 1In this application embodiment, "large diameter" refers to a situation where the widest part of the steel bar segment cross-section reaches 9m or more, and "rounded" refers to a steel bar segment cross-section including a circular portion. In this application embodiment, the steel bar segment cross-section includes two arc segments and two straight segments connecting the endpoints of the different arc segments. Figure 1 The steel reinforcement segment 1 shown is a hollow structure, therefore the main reinforcement of the steel reinforcement segment 1 is configured as an outer ring structure 1a and an inner ring structure 1b.

[0037] refer to Figure 2 and Figure 3 This application provides an adjustable disc-shaped lifting device 2, including a main load-bearing rod 21, a connecting rod 22, a distribution beam 23, and a movable lifting frame 24. Details are as follows:

[0038] The main load-bearing rods 21 extend radially from their center points, and are distributed in a disc-like manner on the same plane. The connecting rods 22 connect adjacent main load-bearing rods 21. The main load-bearing rods 21 and the connecting rods 22 are welded together to form a non-removable, stable structure. Preferably, the main load-bearing rods 21 are evenly distributed on the plane, and several connecting rods 22 are arranged from the edges of the main load-bearing rods 21 towards the center point; preferably, the radial spacing of each connecting rod 22 is the same. In one possible implementation, the adjustable disc-shaped lifting device 2 of this application is provided with eight main load-bearing rods 21, and four connecting rods 22 are provided between every two main load-bearing rods 21. Adjacent connecting rods 22 at the same distance from the center point intersect at the same point on the main load-bearing rods 21. The main load-bearing rods 21 and the connecting rods 22 form a uniform spider web structure, or a uniform disc structure. The lifting points that are directly connected to the lifting equipment are distributed on the main load-bearing rods 21 according to the requirements of force balance. The lifting device 2 of this application and the lifting equipment (such as...) are connected by steel wire ropes. Figure 9 (As shown). For the overall hoisting of the aforementioned reinforcing bar segment 1, the radial length of the main load-bearing rod 21 needs to cover the largest and widest reinforcing bar segment. Assuming the circular cross-section reinforcing bar segment 1 is the largest segment, the length of the main load-bearing rod 21 should be greater than the longest distance from the aforementioned center point (also the center point of reinforcing bar segment 1) to the arc segment of reinforcing bar segment 1. The radial spacing of the connecting rods 22 is appropriate so that the inner ring structure 1b and the outer ring structure 1a fall under the projection of this spacing, avoiding obstruction at the location where the main reinforcement is located in the reinforcing bar segment 1, which would affect the subsequent installation of the movable lifting frame 24. Furthermore, the main load-bearing rod 21 and the connecting rods 22 can be manufactured using I-beams; the specific model should be determined according to the load requirements.

[0039] The distribution beam 23 is fixed above the connecting rods 22 and spans at least two of the connecting rods 22. The distribution beam 23 is bolted to the connecting rods 22, meaning the connection is detachable. In use, the distribution beam 23 can be configured as needed, with more beams added where the load is high and fewer beams removed where the load is low. The specific connection position of the distribution beam 23 can also be adjusted, not limited to the position shown in the diagram. In this embodiment, adapted to the inner ring structure 1b and outer ring structure 1a of the reinforcing bar segment 1, the length of the distribution beam 23 should cover the top of both the inner ring structure 1b and the outer ring structure 1a. In this case, the distribution beam 23 spans three consecutive connecting rods 22. Correspondingly, the connecting rods 22 supporting the distribution beam 23, especially those supporting the distribution beam 23 with the movable hanger 24, should be structurally reinforced at the support points, for example, by installing stiffening plates. The distribution beam 23 is preferably manufactured from I-beams; the specific model should be determined according to the load requirements.

[0040] The movable hanger 24 is fitted onto the main load-bearing rod 21 and / or the distribution beam 23, and is suspended below the main load-bearing rod 21. Specifically, as shown... Figures 4-7 As shown, the movable hanger 24 includes a steel pipe 241 for mounting reinforcing bars, a clamp 244 for holding a single reinforcing bar, a lifting lug 243 extending from the steel pipe 241, a rope ring 245 mounted on the main load-bearing rod 21 and / or the distribution beam 23, and an adjustable connector 246 connecting the rope ring 245 and the lifting lug 243.

[0041] The steel pipe 241 has positioning holes 2411 for the rebar to pass through. Each steel pipe 241 may have more than one positioning hole 2411, preferably two or three. The spacing of the positioning holes 2411 on the same steel pipe 241 is adapted to the rebar spacing of the structure to be hoisted, and the size of the positioning holes 2411 should also be adapted to the rebar type of the structure to be hoisted. In the hoisting device of this application, the rebar passing through the positioning holes 2411 is essentially the main rebar of the rebar segment 1. After the main rebar passes through the steel pipe 241, the top of each main rebar is clamped by a conical sleeve clamp, so that the conical sleeve clamp abuts against the steel pipe 241, thus becoming a hoisting point for the rebar segment 1. Preferably, the steel pipe 241 is a square steel pipe, thereby providing a flat top surface that abuts against the conical sleeve clamp to increase the stress-bearing area. The conical sleeve clamp includes a conical sleeve and a clamping plate that are nested together, and a gasket inserted between the conical sleeve and the square steel pipe.

[0042] The embodiments of this application provide two types of movable hangers, the main difference being the number of steel pipes 241 that make up them, such as... Figure 6The first movable hanger 24a shown contains two or more steel pipes 241. Each steel pipe 241 is arranged parallel to the others at a preset interval. A pair of support steel plates 242 are intersecting and connected to the steel pipes 241. At this time, at least one pair of lifting lugs 243 extend from the support steel plates 242. Each pair of lifting lugs 243 is connected to a rope loop 245 via an adjustable connector 246, enabling it to be fitted onto the main load-bearing rod 21 or the distribution beam 23. In this embodiment, the first movable hanger 24a has three steel pipes 241, each with three positioning holes 2411. A pair of support steel plates 242 are connected to both ends of the steel pipes 241. Each support steel plate 242 has two pairs of lifting lugs 243, with the axis of the holes in the two pairs of lifting lugs 243 parallel to the axis of the steel pipes 241. Therefore, this first movable hanger 24a uses two rope loops 245. The first movable hanger 24a simultaneously holds nine main reinforcing bars, which together form a lifting point. It is mainly used in the outer ring structure 1a of the reinforcing bar segment 1 in this embodiment.

[0043] like Figure 7 The second movable hanger 24b shown includes a steel pipe 241. A pair of lifting lugs 243 extend from the body of the steel pipe 241. These lugs 243 are connected to a rope loop 245 via an adjustable connector 246, enabling them to be fitted onto the main load-bearing rod 21 or the distribution beam 23. In this embodiment, the steel pipe 241 of the second movable hanger 24b has three positioning holes 2411. The pair of lifting lugs 243 extend from the middle of the body of the steel pipe 241, and the axis of the holes in these lugs 243 is parallel to the axis of the steel pipe 241. Therefore, this second movable hanger 24b uses a corresponding rope loop 245. This second movable hanger 24b simultaneously holds three main reinforcing bars, which form a lifting point. It is mainly used in the inner ring structure 1b of the reinforcing bar segment 1 in this embodiment.

[0044] like Figure 4 and Figure 5As shown, the rope loop 245 is directly sleeved on the main load-bearing rod 21 or the distribution beam 23. A limiting groove 25 is provided at the sleeve position of the rope loop 245 to prevent slippage. Optionally, a pair of reinforcing steel bars can be simultaneously fixed to the top surface of the main load-bearing rod 21 or the distribution beam 23 to form the limiting groove 25. Further, a protective structure for dispersing pressure and buffering is provided at the sleeve position of the rope loop 245. In one possible implementation, wooden planks 26 are laid on the sides of the main load-bearing rod 21 and the distribution beam 23. The wooden planks 26 are fixed by tie rods 27 penetrating the main load-bearing rod 21 or the distribution beam 23. When the main load-bearing rod 21 and the distribution beam 23 are made of I-beams, the wooden planks 26 and the beam body cannot fit securely. Therefore, square timber 28 is filled into the space between the wooden planks 26 and the beam body to support the wooden planks 26. More preferably, rubber 29 is sleeved on the upper and lower end faces of the main load-bearing rod 21 and the distribution beam 23; a 2cm thick rubber sheet can be used. The wooden planks 26 and rubber 29 provide all-around protection for the surfaces of the main load-bearing rod 21 and the distribution beam 23, preventing the tension and friction generated by the rope rings 245 during the hoisting process from adversely affecting the main load-bearing rod 21 and the distribution beam 23. In addition, the worn wooden planks 26 and rubber sheets are easy to replace, saving costs.

[0045] The rope loop 245 of this application can be made of steel wire rope, and the length of the rope loop 245 should be adjusted according to the setting height of the lifting point. The adjustable connector of this application adopts a turnbuckle or a hand chain hoist, or other connecting device that can adjust the length of the body longitudinally. The rope loop 245, together with the adjustable connector, can easily adjust the height of the lifting point. Before lifting the steel bar segment 1, the length of the rope loop 245 and the installation length of the adjustable connector can be selected. After the steel bar segment 1 is lifted into the air and when it is in place and connected, adjusting only the adjustable connector can achieve instant adjustment of the lifting point height or the force balance of the lifting point, so as to control the lifting posture of the steel bar segment 1.

[0046] Therefore, the adjustable disc-shaped lifting device 2 of this application has a double-layer structure: an upper structure composed of a main load-bearing rod 21, a connecting rod 22, and a distribution beam 23, and a lower structure composed of a movable lifting frame 24. The upper structure is stable, while the lower structure is adjustable, allowing for precise adjustment of the lifting point position and height to accommodate the calculated deformation at various points on the cross-section of the reinforcing bar segment 1, effectively improving the deformation situation during the overall lifting of large-diameter variable-circular cross-section reinforcing bar segments.

[0047] Furthermore, the adjustable disc-shaped lifting device 2 is used to achieve the overall hoisting of large-diameter variable-circular cross-section steel bar segments. The specific method is as follows:

[0048] S1, tie the steel reinforcement segments according to the preset circular cross-sectional profile.

[0049] The binding of reinforcing bar segments is usually carried out at the binding platform. A precast positioning toothed plate (such as...) is placed at the bottom of the reinforcing bar segment on the binding platform. Figure 8 As shown, the positioning toothed plate is CNC cut to meet the docking requirements of the top and bottom openings of each rebar segment, especially the inclination requirements of the main reinforcement bars during binding. The positioning toothed plate uses positioning holes to define the spacing and inclination angle at the bottom opening of each main reinforcement bar, precisely matching the top opening of the docking rebar segments. The rebar segments are bound using the positioning toothed plate. The rebar segments bound at the binding platform include the stiffening skeleton, most of the main reinforcement bars, and stirrups connecting the main reinforcement bars. If necessary, some tie bars are also included. The remaining small amount of rebar is installed in situ after alignment and connection.

[0050] S2, set up lifting points and connect corresponding lifting tools according to the deformation of the steel bar segments after lifting.

[0051] In this embodiment, calculations show that lifting the large-diameter, circularly-section steel reinforcement segment using conventional methods would cause an increase in the deformation of the first main reinforcement 11 of the circular arc segment due to its own weight, and the deformation would also differ from the conventional situation. Therefore, it is necessary to increase the lifting stability of the circular arc segment and control the deformation after lifting. One control method is to increase the number of lifting points, and another optional control method is to increase the lifting area of ​​each individual lifting point. In addition, for the densely reinforced outer ring structure 1a of this embodiment, a denser tension is also required to control the deformation. Therefore, using the aforementioned adjustable disc-shaped lifting device 2, lifting points are set for the steel reinforcement segments based on the predicted deformation of the large-diameter circular cross-section. Specifically, the positions of the connecting movable lifting frames 24 are determined on the steel reinforcement segments. A first movable lifting frame 24a, which fixes a larger number of main reinforcing bars at once, is evenly fixed to the outer ring structure 1a of the steel reinforcement segment. A second movable lifting frame 24b, which fixes a smaller number of main reinforcing bars at once, is evenly fixed to the inner ring structure 1b of the steel reinforcement segment. The relative height of each movable lifting frame 24 needs to be adjusted adaptively, mainly determined by the length of the rope loop 245 and the length of the adjustable connector. Therefore, in most cases, all lifting points are not coplanar. However, those skilled in the art should understand that when using the adjustable disc-shaped lifting device 2 of this application to lift steel reinforcement segments with circular cross-sections (or other centrally symmetrical cross-sections), lifting points should be set according to the lifting requirements, and in this case, the lifting points can be coplanar.

[0052] S3, using the lifting equipment, the entire steel bar segment is lifted to the docking position;

[0053] Before hoisting the entire rebar segment, the aerial hoisting posture is leveled. This involves lifting the rebar segment approximately 10cm above the binding platform and observing its tilt. Adjustable connectors are then used for leveling, specifically a turnbuckle combined with a hand-operated hoist. After initial leveling, the rebar segment is further lifted, gradually raised and moved to above the docking position in preparation for alignment and connection. While the rebar segment is in the air, it cannot be guaranteed to remain completely free of deformation; however, its controlled deformation can be utilized to complete the docking later.

[0054] S4, after connecting the first main reinforcement 11 at the arc segment, the lifting device is unloaded for the first time; after connecting the second main reinforcement 12 at the straight segment, the lifting device is removed.

[0055] During the connection process, the bottom of the current rebar segment should be connected to the top of the bottom rebar segment to complete the connection of the main reinforcement bars of the upper and lower rebar segments. When installing large-diameter, circular cross-section rebar segments, after the segment is hoisted into place, first connect the first main reinforcement bar 11 of the arc segment whose deformation was controlled during hoisting. Then, unload most of the lifting weight; the unloading load can be 60%–85% of the total load. This means that part of the actual weight of the rebar segment is transferred from the hoisting equipment to the constructed segment. After the support state of the rebar segment changes, its overall shape returns to a state closer to the actual connection. Specifically, the second main reinforcement bar 12 at the straight segment where the deformation was controlled during hoisting decreases from inward or outward deformation and returns to its assembled state, thus facilitating the connection of the upper and lower rebar segments. After connecting the second main reinforcement bar at the straight segment, remove the hoisting equipment. After removing the hoisting equipment, complete the binding of the remaining rebars in the segment, thereby completing the overall hoisting process of the rebar segment.

[0056] In summary, the method for hoisting large-diameter variable-circular cross-section steel bars in this application utilizes an adjustable disc-shaped lifting device and makes reasonable use of the shape and deformation characteristics of the large-diameter variable-circular cross-section steel bar segments. After connecting the main bars of the arc segment with smaller deformation, and unloading most of the load on the main hook, the steel bar segment is allowed to return to its shape. Then, the main bars of the straight segment with larger deformation are connected. In this way, there is no need to take other measures to reduce the deformation of the steel bar segments during hoisting, such as adding reinforcing rings or increasing the stiffness of the stiffening frame, which would increase the overall hoisting weight. This saves materials and speeds up the connection of the steel bars.

[0057] The above embodiments are preferred embodiments of this application, but are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of this application shall be considered equivalent substitutions and shall be included within the protection scope of this application.

Claims

1. A method for integral hoisting of large-diameter variable-circular cross-section steel reinforcement segments, wherein the cross-section of the steel reinforcement segment comprises two circular arc segments and two straight segments connecting the endpoints of the different circular arc segments, characterized in that, It includes the following steps: Bind the reinforcing steel segments according to the preset circular cross-sectional profile; Based on the deformation of the steel bar segments after lifting, set up lifting points and connect corresponding lifting equipment; The steel bar segment was lifted as a whole to the docking position using the lifting equipment. After connecting the first main reinforcement bar at the arc segment where the deformation range is controlled to be small during hoisting, the lifting equipment is unloaded for the first time, with the unloading load being 60% to 85% of the total load; After the second main reinforcement bar at the straight section with the largest deformation during the subsequent hoisting, the hoisting equipment is removed.

2. The method as described in claim 1, characterized in that, The step of binding the reinforcing bar segments according to the preset variable circular cross-sectional profile includes: Pre-set positioning teeth according to the connection requirements of the top and bottom openings of the steel bar segments; The positioning toothed plate is used to bind the steel bar segments; The steel reinforcement segment includes a stiffening skeleton, most of the main reinforcement bars, and stirrups connecting the main reinforcement bars.

3. The method as described in claim 2, characterized in that, After removing the lifting equipment, complete the binding of the remaining reinforcing bars.

4. The method as described in claim 1, characterized in that, The lifting points are configured to be non-coplanar to adapt to the deformation of the steel bar segments.

5. The method as described in claim 4, characterized in that, The lifting points are located on the main reinforcing bars.

6. The method as described in claim 4, characterized in that, The lifting device includes a coplanar upper structure and a non-coplanar lower structure. The lower structure includes several movable hangers suspended below the upper structure, and each movable hanger corresponds to a lifting point.

7. The method as described in claim 6, characterized in that, The movable hanger is connected to the upper structure via an adjustable connector, which is used to adjust the height and planar position of the movable hanger.

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