Post-tensioned prestressed seamless concrete floor construction method

Abstract

The application discloses a post-tensioned prestressed seamless concrete floor construction method, which comprises the following steps: laying a corrugated pipe; installing a tension end and a fixed end node; inserting a prestressed tendon into the corrugated pipe; installing a strain sensing assembly, wherein the strain sensing assembly comprises stress transmission steel bars and a strain sensing sensor, the stress transmission steel bars comprise coaxially arranged first steel bars and second steel bars, and the two main steel bars are connected through connecting steel bars; an installation gap is left between the end faces of the opposite ends of the first steel bars and the second steel bars, and the strain sensing sensor is installed in the installation gap; pouring concrete, wherein the strain sensing assembly is poured and wrapped in the concrete; and tensioning the prestressed tendon, wherein during the tensioning process of the prestressed tendon, the prestress is controlled, the tensioning elongation value is measured as a check, and the strain value of the concrete is simultaneously referred to. According to the application, the strain condition of the concrete in the prestressed seamless floor construction process can be known by the staff through the strain sensing assembly.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of building technology, in particular to a post-tensioned prestressed seamless concrete floor construction method. BACKGROUND

[0002] The prestressed integral seamless floor is arranged with prestressed tendons in the concrete, and after the concrete strength reaches the design requirement, the prestressed tendons are tensioned to apply a pre-compressive stress to the concrete, so as to solve the shrinkage stress of the concrete itself and resist the external load during normal use of the floor. By applying the prestress, the cutting joint of the floor can be cancelled.

[0003] In the tensioning construction of the prestressed tendon, the tensioning force control is generally used as the main control, and the tensioning elongation value is measured for checking, so that the theoretical elongation value and the actual elongation value of the prestressed tendon are controlled within a certain error range. The actual purpose of the prestressed tendon tensioning is to apply a pre-compressive stress to the concrete. The concrete will produce a corresponding strain under the action of the pre-compressive stress. By controlling the tensioning force, the strain of the concrete can be indirectly controlled. However, the actual strain of the concrete under the action of the pre-compressive stress cannot be directly fed back, which is not conducive to the prevention of the cracking problem of the concrete structure. SUMMARY

[0004] In order to understand the strain of the concrete in the construction process of the prestressed seamless floor, the present application provides a post-tensioned prestressed seamless concrete floor construction method.

[0005] The post-tensioned prestressed seamless concrete floor construction method provided by the present application adopts the following technical scheme:

[0006] The post-tensioned prestressed seamless concrete floor construction method comprises the following steps: cleaning the base layer; laying the broken stone bending-resistant layer; laying the sand sliding layer; laying the corrugated pipe; installing the tensioning end and the fixed end node; threading the prestressed tendon into the corrugated pipe; installing the strain sensing assembly, the strain sensing assembly comprising a stress transmission steel bar and a strain sensing sensor, the stress transmission steel bar comprising a first steel bar and a second steel bar arranged coaxially, the axial directions of the first steel bar and the second steel bar being arranged along the extension direction of the corrugated pipe, the first steel bar and the second steel bar being connected by a connecting steel bar, one end of the connecting steel bar being connected and fixed to the outer peripheral surface of the first steel bar, the other end of the connecting steel bar being connected and fixed to the outer peripheral surface of the second steel bar; an installation gap being left between the end faces of the opposite ends of the first steel bar and the second steel bar, the strain sensing sensor being installed in the installation gap; pouring the concrete, the strain sensing assembly being wrapped inside the concrete; tensioning the prestressed tendon, in the tensioning process of the prestressed tendon, the pre-compressive stress is controlled, the tensioning elongation value is measured as a checking value, and the strain value of the concrete is also referred to; and the prestressed tendon is threaded and grouted.

[0007] By adopting the above technical solution, during prestressing tendon tensioning, the prestressing tendons undergo tensile deformation. The deformation force of the prestressing tendons acts on the concrete, causing compressive deformation. The strain sensing component located inside the concrete deforms accordingly. The strain sensor of the strain sensing component is installed between the first and second reinforcing bars. When the concrete compresses and deforms, the first and second reinforcing bars, which transmit stress, move closer together, compressing the strain sensor. This allows the strain sensor to reflect the strain of the concrete, enabling workers to use the actual strain of the concrete as a control parameter for the tension force. The strain sensor is mainly deformed by the compression of the first and second reinforcing bars, which in turn are compressed by the concrete. Due to the relatively long length of the first and second reinforcing bars, the strain sensing component can reflect a wider range of concrete strain, reducing errors. Furthermore, the indirect compression of the strain sensor by the concrete through the first and second reinforcing bars helps avoid the formation of pores on the surface of the strain sensor, which could affect its performance.

[0008] Optionally, the connecting bar has an arc-shaped structure; there are two connecting bars, which are symmetrically arranged along the axis of the first reinforcing bar.

[0009] By adopting the above technical solution, the first and second reinforcing bars are connected by connecting reinforcing bars, ensuring a stable width of the installation gap between them. The connecting reinforcing bars are arc-shaped, making them more prone to deformation when the first and second reinforcing bars approach and compress the strain sensor. The two connecting reinforcing bars are symmetrically positioned along the axis of the first reinforcing bar, which improves the stability of the connection between them and promotes a more balanced compression effect on the strain sensor.

[0010] Optionally, at least three elastic rods are provided at one end of the first reinforcing bar near the second reinforcing bar. The elastic rods are arranged in a circumferential array along the axis of the first reinforcing bar, and the outer circumferential surface of the elastic rods abuts against the strain sensing sensor.

[0011] By adopting the above technical solution, multiple elastic rods are arranged in a circumferential array along the axis of the first reinforcing bar. When all elastic rods simultaneously abut against the strain sensor, they can limit the strain sensor, making it difficult for the strain sensor to fall out of the installation gap. The elastic rods are flexible, allowing the strain sensor to be pressed into or removed from the installation gap from the gap between two adjacent elastic rods, which is quite convenient.

[0012] Optionally, the strain sensor has a columnar structure, the length direction of the strain sensor is along the axial direction of the first reinforcing bar, and a gap compensation shim is provided between the strain sensor and the first reinforcing bar.

[0013] By adopting the above technical solution, by setting a gap compensation shim between the strain sensor and the first reinforcing bar, the strain sensor and the gap compensation shim can fully fill the installation gap between the first reinforcing bar and the second reinforcing bar. When the concrete is strained, the first reinforcing bar and the second reinforcing bar can squeeze the strain sensor in time.

[0014] Optionally, the strain sensor has wires that extend beyond the floor paving area.

[0015] By adopting the above technical solution, the wires of the strain sensor are extended beyond the floor paving area. After the floor construction is completed, the strain sensor can continue to be used to monitor the strain of the floor structure.

[0016] Optionally, the wire is disposed at the end of the strain sensor away from the first reinforcing bar, and the end of the second reinforcing bar near the first reinforcing bar has a notch, the notch being used to avoid the wire.

[0017] By adopting the above technical solution, the conductor is positioned at the end of the second reinforcing bar closest to the first reinforcing bar. The notch in the second reinforcing bar can avoid the conductor, allowing the conductor to bend inside the notch and extend outwards. The gap compensation shim is located at the end of the strain sensor furthest from the conductor, eliminating the need for a notch in the shim to avoid the conductor.

[0018] Optionally, multiple strain sensing components are installed, with each strain sensing component positioned between two adjacent bellows, and the number of bellows between each pair of adjacent strain sensing components is two.

[0019] By adopting the above technical solution, the number of corrugated pipes for every two adjacent strain sensing components is set to two, so that each corrugated pipe is adjacent to one strain sensing component. Therefore, when the prestressing tendon passing through the corrugated pipe is tensioned, the strain of the concrete near the corresponding corrugated pipe can be fed back through the adjacent strain sensing component. Furthermore, compared to the case where there is only one corrugated pipe between every two adjacent strain sensing components, the number of strain sensing components can be reduced.

[0020] Optionally, before laying the sand and slip layer, multiple steel wires are laid at intervals above the crushed stone flexural layer, with both ends of the steel wires extending beyond the laying range of the sand and slip layer; before pouring concrete, the two ends of the steel wires are straightened, and then the taut steel wires are vibrated by a vibration device to indirectly vibrate the sand and slip layer.

[0021] By employing the aforementioned technical solution, workers often need to walk and tread on the sand-slip layer after its installation to perform subsequent tasks such as rebar tying and corrugated pipe installation. The sand-slip layer, after being stepped on, is prone to unevenness, which can significantly affect the flatness of the concrete surface during subsequent pouring. However, using a vibrating tool and taut steel wire to vibrate the sand-slip layer helps to level its surface, reducing unevenness.

[0022] Optionally, before vibrating the sand-slip layer using a vibrating device and a steel wire, the tensioned steel wire is pulled back and forth to loosen the steel wire relative to the sand-slip layer.

[0023] By adopting the above technical solution, the steel wire can be loosened relative to the sand slip layer by reciprocating pulling and moving the steel wire, reducing the clamping force of the sand slip layer on the steel wire, making it easier for the steel wire to vibrate the sand particles in the sand slip layer.

[0024] Optionally, before pouring concrete, one end of the steel wire is cut off, and then the steel wire is pulled out of the sand layer by pulling the other end of the steel wire.

[0025] By adopting the above technical solution, cutting off one end of the steel wire makes the cut part of the steel wire smoother, allowing the steel wire to be pulled out of the sand layer more smoothly and reducing the driving effect of the steel wire on the sand particles in the sand layer.

[0026] In summary, this application includes at least one of the following beneficial technical effects:

[0027] 1. Strain sensors can detect the strain of concrete, allowing workers to use the actual strain as a control parameter for tension. The strain sensors detect deformation caused by the compression of the first and second reinforcing bars. Due to the relatively long length of the first and second reinforcing bars, the strain sensing component can provide feedback on a wide range of concrete strain, reducing errors.

[0028] 2. Vibrating the sand-slip layer using a vibrating tool and a taut steel wire helps to level the upper surface of the sand-slip layer, reducing unevenness on the upper surface. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the construction method of tensioned prestressed seamless concrete flooring in Example 1.

[0030] Figure 2 This is a schematic diagram of the strain sensing component in Example 1.

[0031] Figure 3 This is a schematic diagram in Example 1 illustrating the separation of the strain sensing sensor from the stress transmission steel bar.

[0032] Figure 4 This is a schematic diagram in Example 1 used to illustrate the relative positional relationship between the bellows and the strain sensing component.

[0033] Figure 5 This is a flowchart illustrating the construction method of tensioned prestressed seamless concrete flooring in Example 2.

[0034] Figure 6 This is a schematic diagram used in Example 2 to illustrate the positional relationship between the steel wire and the sand-slip layer.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Strain sensing component; 11. Strain sensing sensor; 111. Wire; 12. Stress transfer reinforcement; 121. First reinforcement; 122. Second reinforcement; 1221. Notch; 123. Connecting reinforcement; 13. Installation gap; 14. Elastic rod; 15. Gap compensation shim; 2. Corrugated pipe; 3. Steel wire; 31. Collar. Detailed Implementation

[0037] The following is in conjunction with the appendix Figures 1-6 This application will be described in further detail.

[0038] Example 1

[0039] This application discloses a method for constructing a post-tensioned prestressed seamless concrete floor. (Refer to...) Figure 1 The construction method for post-tensioned prestressed seamless concrete flooring includes the following steps:

[0040] Step 1: Clean the base layer to ensure the site is clean, free of debris, and the roads are unobstructed;

[0041] Step 2: Lay geogrid paving material on the base layer;

[0042] Step 3: Lay the crushed stone flexural layer. The crushed stone flexural layer is a cement-stabilized crushed stone layer formed by compaction and curing. The cement content of the cement-stabilized crushed stone layer is not less than 5%, the crushing value of the crushed stone does not exceed 30%, and the maximum particle size is not greater than 30mm.

[0043] Step 4: First, lay a 0.5mm thick PE film puncture-proof and moisture-proof layer on the surface of the crushed stone bending layer, then lay a 30mm thick sand and slip layer, and then lay two layers of 0.3mm thick PE film; the PE film puncture-proof and moisture-proof layer, the sand and slip layer, and the two layers of PE film together serve as a slip layer.

[0044] Step 5: Install the edge template and armor seams;

[0045] Step 6, tie the bottom layer of reinforcing steel;

[0046] Step 7, Lay corrugated pipe 2;

[0047] Step 8: Installation of tensioning end and fixed end nodes;

[0048] Step 9: Insert the prestressing tendons into the corrugated pipe 2. The inner cavity of the corrugated pipe 2 serves as the channel for inserting the prestressing tendons. The prestressing tendons are steel strands, which are inserted using a shuttle.

[0049] Step 10: Install the stirrup reinforcement and securely tie the stirrup reinforcement to the corrugated pipe 2;

[0050] Step 11: Install multiple strain sensing components 1. Each strain sensing component 1 is set between two adjacent bellows 2, and there are two bellows 2 between each two adjacent strain sensing components 1.

[0051] Step 12: Pour concrete, encapsulate strain sensing component 1 inside the concrete, and apply the diamond abrasion wear-resistant surface layer.

[0052] Step 13, tensioning of prestressing tendons. During the tensioning process of prestressing tendons, the control of prestress is mainly based on the tension force, and the measured elongation value of the tension is used as a check, while the strain value of the concrete is also taken into account.

[0053] Step 14: Grout all the prestressing tendon ducts after the tensioning process is completed.

[0054] Reference Figure 2 and Figure 3 The strain sensing component 1 includes a stress transmission reinforcing bar 12 and a strain sensing sensor 11. The stress transmission reinforcing bar 12 includes a first reinforcing bar 121 and a second reinforcing bar 122 arranged coaxially. The first reinforcing bar 121 and the second reinforcing bar 122 are made of cold-rolled ribbed steel bar material of the same specification. The first reinforcing bar 121 and the second reinforcing bar 122 are arranged axially along the extension direction of the corrugated pipe 2. The first reinforcing bar 121 and the second reinforcing bar 122 are tied to the bottom reinforcing bar by wire or cable tie.

[0055] The first reinforcing bar 121 and the second reinforcing bar 122 are connected by a connecting bar 123. The connecting bar 123 has an arc-shaped structure and is a circular cross-section reinforcing bar. The diameter of the connecting bar 123 is smaller than that of the first reinforcing bar 121. One end of the connecting bar 123 is welded and fixed to the outer circumference of the first reinforcing bar 121, and the other end of the connecting bar 123 is welded and fixed to the outer circumference of the second reinforcing bar 122. There are two connecting bars 123, which are symmetrically arranged along the axis of the first reinforcing bar 121.

[0056] An installation gap 13 is left between the end faces of the two main reinforcing bars, and the strain sensor 11 is installed in the installation gap 13. The strain sensor 11 has a cylindrical structure, and its length direction is set along the axial direction of the first reinforcing bar 121. The strain sensor 11 has a wire 111, which is located at the end of the strain sensor 11 away from the first reinforcing bar 121. The end of the second reinforcing bar 122 near the first reinforcing bar 121 has a notch 1221, which can avoid the wire 111. The wire 111 is bent in the inner area of ​​the notch 1221 and extends outward to the outside of the paving range of the ground, so that the strain sensor 11 can form an electrical connection with the external control system. Thus, the strain sensor 11 can feed back the strain value of the concrete as a tensioning control parameter for the prestressing tendon.

[0057] The strain sensor 11 of the strain sensing component 1 is installed between the first reinforcing bar 121 and the second reinforcing bar 122. When the concrete undergoes compressive deformation during the tensioning of the prestressing tendon, the first reinforcing bar 121 and the second reinforcing bar 122 of the stress transmission reinforcing bar 12 approach each other and squeeze the strain sensor 11, so that the strain sensor 11 can reflect the strain of the concrete.

[0058] Reference Figure 2 Three elastic rods 14 are provided at one end of the first reinforcing bar 121 near the second reinforcing bar 122. The elastic rods 14 are arranged in a circumferential array along the axis of the first reinforcing bar 121. The elastic rods 14 are welded to the outer circumferential surface of the first reinforcing bar 121 by means of cylindrical contact. The outer circumferential surface of the elastic rods 14 abuts against the strain sensing sensor 11. The elastic rods 14 can limit the strain sensing sensor 11, making it difficult for the strain sensing sensor 11 to fall out of the installation gap 13.

[0059] Reference Figure 3 A gap compensation shim 15 is provided between the strain sensor 11 and the first reinforcing bar 121. The outline shape of the gap compensation shim 15 is adapted to the outer outline shape of the first reinforcing bar 121. The number of gap compensation shims 15 can be set to multiple as needed. Multiple gap compensation shims 15 can be set to different thickness specifications as needed. The thickness specification of the gap compensation shim 15 is between 0.1mm and 1mm. The material of the gap compensation shim 15 can be thin copper sheet or thin steel sheet.

[0060] Reference Figure 3 A gap is left between the end of the elastic rod 14 away from the first reinforcing bar 121 and the end face of the second reinforcing bar 122 near the first reinforcing bar 121 for the gap compensation shim 15 to pass through. The gap compensation shim 15 enters the installation gap 13 through the gap between the elastic rod 14 and the second reinforcing bar 122, and moves to a position close to the first reinforcing bar 121. Then, each elastic rod 14 limits the gap compensation shim 15.

[0061] To further improve the stability of the installation state of the strain sensor 11, adhesive can be used to bond both ends of the strain sensor 11 to the first reinforcing bar 121 and the second reinforcing bar 122, respectively. When multiple gap compensation shims 15 are stacked, the adhesive can bond the gap compensation shims 15 together as a whole.

[0062] The implementation principle of the post-tensioned prestressed seamless concrete floor construction method in this application embodiment is as follows: During prestressing tendon tensioning, the concrete undergoes compressive deformation, and the strain sensing component 1 located inside the concrete deforms accordingly. The strain sensing sensor 11 of the strain sensing component 1 is installed between the first reinforcing bar 121 and the second reinforcing bar 122. When the concrete compresses and deforms, the first reinforcing bar 121 and the second reinforcing bar 122 of the stress transmission reinforcing bar 12 move closer to each other, squeezing the strain sensing sensor 11, enabling the strain sensing sensor 11 to reflect the strain of the concrete. This allows workers to use the actual strain of the concrete as a control parameter for the tension force. The strain sensing sensor 11 is mainly deformed by the compression of the first reinforcing bar 121 and the second reinforcing bar 122, while the first reinforcing bar 121 and the second reinforcing bar 122 are squeezed by the concrete. Because the first reinforcing bar 121 and the second reinforcing bar 122 are relatively long, the strain sensing component 1 can reflect the strain of the concrete over a larger range, reducing errors.

[0063] Example 2

[0064] Reference Figure 5 and Figure 6 The difference between this embodiment and embodiment 1 is that in step 3, before laying the sand and slip layer, multiple steel wires 3 are laid at intervals above the crushed stone bending layer. The steel wires 3 are located on the upper surface of the PE film puncture-proof moisture barrier layer. The two ends of the steel wires 3 extend out of the laying range of the sand and slip layer. The two ends of the steel wires 3 are respectively tied with loops 31 that can be gathered.

[0065] When the steel wire 3 needs to pass through the side template, it can pass through the gap between the side template and the side template support surface, or a through hole can be drilled in the side template for the steel wire 3 to pass through.

[0066] In step 12, before pouring concrete, two rod-shaped tools or two hook-shaped tools are inserted into the loops 31 at both ends of the steel wire 3, respectively. Then, the rod-shaped tools are used to straighten both ends of the steel wire 3, making the steel wire 3 taut. The taut steel wire 3 is then pulled back and forth. The taut steel wire 3 is then vibrated by a vibration device to indirectly vibrate the sand and slip layer, so that the upper surface of the sand and slip layer is vibrated and leveled, reducing the unevenness of the upper surface of the sand and slip layer. After the vibration is completed, one end of the steel wire 3 is cut off, and then the steel wire 3 is pulled out of the sand and slip layer by pulling the other end of the steel wire 3.

[0067] The vibration device in this embodiment can be a vibrating rod or a plate vibrator, etc.

[0068] The implementation principle of this embodiment is as follows: When the steel wire 3 is tensioned, the vibration device vibrates the sand particles in the sand-slippery layer through the tensioned steel wire 3, which helps to vibrate and level the upper surface of the sand-slippery layer, so that the unevenness caused by workers stepping on it during work can be repaired and leveled, making the surface of the sand-slippery layer smoother. This allows for a higher degree of flatness of the bottom surface of the concrete to be poured in subsequent construction, thereby reducing the resistance when the concrete expands and contracts.

[0069] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A construction method for post-tensioned prestressed seamless concrete flooring, characterized in that, Includes the following steps: Clean up the grassroots level; Lay a crushed stone flexural layer; Lay a sand and slip layer; Laying corrugated pipe (2); Installation of tensioning and fixed end nodes; Insert the prestressed tendons into the corrugated pipe (2); Install a strain sensing component (1), which includes a stress transmission steel bar (12) and a strain sensing sensor (11). The stress transmission steel bar (12) includes a first steel bar (121) and a second steel bar (122) arranged coaxially. The first steel bar (121) and the second steel bar (122) are arranged axially along the extension direction of the corrugated pipe (2). The first steel bar (121) and the second steel bar (122) are connected by a connecting bar (123). One end of the connecting bar (123) is connected and fixed to the outer peripheral surface of the first steel bar (121), and the other end of the connecting bar (123) is connected and fixed to the outer peripheral surface of the second steel bar (122). An installation gap (13) is left between the end faces of the opposite ends of the first steel bar (121) and the second steel bar (122). The strain sensing sensor (11) is installed in the installation gap (13). Concrete is poured, and the strain sensing component (1) is poured and encased inside the concrete. Prestressing tendon tensioning: During the prestressing tendon tensioning process, the control of prestress is mainly based on the tension force, and the measured tension elongation value is used as a check, while the strain value of concrete is also taken into account. Grouting of the prestressing tendon insertion ducts.

2. The construction method for post-tensioned prestressed seamless concrete flooring according to claim 1, characterized in that: The connecting bar (123) has an arc-shaped structure; there are two connecting bars (123), and the two connecting bars (123) are symmetrically arranged along the axis of the first reinforcing bar (121).

3. The construction method for post-tensioned prestressed seamless concrete flooring according to claim 1, characterized in that: At least three elastic rods (14) are provided at one end of the first reinforcing bar (121) near the second reinforcing bar (122). The elastic rods (14) are arranged in a circumferential array along the axis of the first reinforcing bar (121), and the outer circumferential surface of the elastic rods (14) abuts against the strain sensing sensor (11).

4. The construction method for post-tensioned prestressed seamless concrete flooring according to claim 1, characterized in that: The strain sensor (11) has a columnar structure. The length direction of the strain sensor (11) is along the axial direction of the first reinforcing bar (121). A gap compensation shim (15) is provided between the strain sensor (11) and the first reinforcing bar (121).

5. The construction method for post-tensioned prestressed seamless concrete flooring according to claim 1, characterized in that: The strain sensor (11) has a wire (111) that extends beyond the paving area.

6. The construction method for post-tensioned prestressed seamless concrete flooring according to claim 5, characterized in that: The conductor (111) is located at the end of the strain sensor (11) away from the first reinforcing bar (121), and the second reinforcing bar (122) has a notch (1221) at the end near the first reinforcing bar (121), the notch (1221) being used to avoid the conductor (111).

7. The construction method for post-tensioned prestressed seamless concrete flooring according to claim 1, characterized in that: Multiple strain sensing components (1) are installed, and each strain sensing component (1) is set between two adjacent bellows (2). The number of bellows (2) between each two adjacent strain sensing components (1) is two.

8. The construction method for post-tensioned prestressed seamless concrete flooring according to claim 1, characterized in that: Before laying the sand and slip layer, multiple steel wires (3) are laid at intervals above the crushed stone bending layer, with both ends of the steel wires (3) extending out of the sand and slip layer. Before pouring concrete, the two ends of the steel wires (3) are straightened, and then the taut steel wires (3) are vibrated by a vibration device to indirectly vibrate the sand and slip layer.

9. The construction method for post-tensioned prestressed seamless concrete flooring according to claim 8, characterized in that: Before vibrating the sand-slip layer using a vibrating device and a steel wire (3), the tensioned steel wire (3) is pulled back and forth to loosen the steel wire (3) relative to the sand-slip layer.

10. The construction method for post-tensioned prestressed seamless concrete flooring according to claim 8, characterized in that: Before pouring concrete, one end of the steel wire (3) is cut off, and then the steel wire (3) is pulled out of the sand layer by pulling the other end of the steel wire (3).

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