A joint assembly for applying prestress and a method of prestress application

Abstract

The application discloses a joint assembly for prestress application, which comprises a pressure seat and a transition piece arranged at intervals, the pressure seat comprises a pressure frame and pressure bearing plates and end head plates installed at both ends of the pressure frame, a jack is detachably installed in a force applying cavity, and a piston hole is formed in the end head plate; the end plate and the end head plate are parallel to each other or have an included angle of less than or equal to 5 degrees; both ends of a tension bolt are connected to the pressure seat and the transition piece respectively; the joint assembly can be installed between a horizontal support and a structural member, and is used for prestress application of the horizontal support; after jacking of the transition piece is completed, high-early-strength grouting material is poured into a gap between the end plate and the end head plate to form a grouting material pouring block. The application further discloses a prestress application method for the horizontal support by using the joint assembly. In the application, the grouting material pouring block is used to replace the existing steel wedge, so that the prestress in the horizontal support and the structural member can be kept stable.

Description

Technical Field

[0001] This invention relates to a joint assembly for applying prestress to braces and corner braces, and a method for applying prestress. Background Technology

[0002] During foundation pit construction, to ensure the safety of the pit and prevent collapse, various supports need to be erected within the pit, and prestressing needs to be applied to these supports. Currently, prestressing is generally applied in two ways: one-time application and intermittent application. When applying prestress in a one-time application, jacks are placed between the support and another structural component. The jacks are then activated to apply pressure to the support, generating prestress to resist the pressure of the external soil. After prestressing is applied, steel wedges are driven between the support and the structural component, and bolts are used to secure the wedges to both. The jacks are then removed. In this method, a clamping surface needs to be set on both the support and the structural component, and the steel wedges are clamped between the two clamping surfaces.

[0003] To prevent the steel wedges from slipping outwards due to external vibrations and the pressure from structural components, the two clamping surfaces must be kept parallel. However, in actual construction, achieving perfect parallelism is a high bar, often impossible; only a near-parallel state is possible. Even this requires repeated adjustments and corrections, significantly increasing construction difficulty and extending construction time. Sometimes, in an effort to expedite progress, the adjustment of the two clamping surfaces is insufficient, resulting in an angle between them. Due to this angle, the steel wedges gradually slip outwards over time, exacerbated by vibrations during construction, leading to a reduction in prestress.

[0004] In addition, due to the non-parallelism of the two clamping surfaces, the steel wedge cannot be fully attached to the two clamping surfaces, which can easily cause the support to deviate from its original extension direction, generating radial force and affecting the stability of the support.

[0005] When applying prestress intermittently, the jacks are kept in the pressurized position at all times. Since these jacks are typically hydraulic, their pressure gradually decreases over time, requiring restarting to restore pressure. This method ensures stable prestress, but it necessitates monitoring the jack pressure and requires a large number of jacks. The equipment is bulky and requires corresponding monitoring equipment. Furthermore, the construction environment is harsh, often outdoors, which negatively impacts the stability of the monitoring equipment and increases operating and management costs. Summary of the Invention

[0006] To address the aforementioned problems, this application first proposes a joint assembly for applying prestress, comprising a pressure seat and a transition member spaced apart. The pressure seat includes a pressure frame extending along a first axis and a bearing plate and an end plate fixedly installed at both ends of the pressure frame along the first axis. A force-applying cavity is provided within the pressure frame, and an inlet and outlet for entering and exiting the force-applying cavity are provided on one side of the pressure frame. A jack is detachably installed within the force-applying cavity, and a piston hole is provided on the end plate. The transition member includes an end plate, which is disposed opposite to the end plate, and the end plate and the end plate are parallel to each other or have an included angle of ≤5°. The two ends of a tension bolt are respectively connected to the pressure seat and the transition member.

[0007] The joint assembly can be installed between a horizontal support and a structural member to apply prestress to the horizontal support. When the joint assembly is used to apply prestress to the horizontal support, the piston rod of the jack pushes the transition member. After the push is completed, high early strength grout is poured into the gap between the end plate and the end plate to form a grout casting block.

[0008] The horizontal support is either a brace or a corner brace. When the horizontal support is a brace, the end plate is perpendicular to the first axis. When the horizontal support is a corner brace, the angle between the end plate and the first axis is 30-60°.

[0009] Reinforcing plates are detachably installed at the inlet and outlet to compensate for the strength loss of the pressure frame caused by the opening of the inlet and outlet.

[0010] When the joint assembly in this application is used, the pressure seat and the transition piece need to be installed on the horizontal support and a structural component respectively. When the piston rod of the jack pushes the transition piece, it can generate prestress in both the horizontal support and the structural component. The structural component is specifically the support pile, support wall, or waler, cap beam, etc. erected on the support pile or support wall at the edge of the foundation pit.

[0011] In this application, a grouting block is formed between the end plate and the end cap plate, replacing the existing steel wedge. The grouting block has high compressive strength, capable of withstanding the resistance forces generated by the horizontal supports and structural components. Tension bolts are used to restrain the grouting block, preventing it from detaching from the gap between the end cap plate and the end plate. After the grouting block is formed, the piston rod can be retracted. Because the grouting block does not continuously deform under the pressure of the horizontal supports and structural components, nor does it undergo plastic deformation, dimensional stability is ensured. This prevents the prestress within the horizontal supports and structural components from decreasing due to deformation of the grouting block or its outward detachment from the gap between the end cap plate and the end plate.

[0012] Due to the tension bolts, the grouting block is stably held between the end plates and the end plate, and will not come outward due to external vibration. With this application, it is not necessary to make the end plates and end plates perfectly parallel, and no adjustment is required even if there is a small angle between them, thereby improving construction efficiency.

[0013] By utilizing the fluidity of high early strength grout, the entire gap between the end plates can be filled and fixed in place, ensuring that the horizontal support can extend along the original direction without deviation.

[0014] Using this application, due to construction or manufacturing errors, there can be an angle of ≤5° between the end plate and the end head plate. Although the angle can be increased in actual construction, an excessively large angle will cause the end face of the piston rod of the jack to also form an angle with the end plate, which will increase the friction between the cylinder of the jack and the piston rod and affect the service life of the jack. It is recommended to keep the end plate and the end head plate parallel as much as possible.

[0015] The high early strength grouting material in this application is also known in the prior art as high strength early strength grouting material or early strength grouting material.

[0016] Furthermore, after the jacking is completed, the tension bolts are tensioned using nuts, and then high early strength grout is poured into the gap between the end plate and the end head plate to form a grout casting block; the tension bolts pass through the grout casting block.

[0017] In this application, because the high-early-strength grout is poured after the tension nuts are tensioned, the grout casting block wraps around the tension bolts, forming a prestressed concrete structural block, which further improves the stability of the grout casting block between the end plates and the end caps. Pre-tensioning the tension bolts allows them to undergo elastic deformation beforehand. After the jacks are removed, when the grout casting block is compressed and deformed under the pressure of the horizontal supports and structural components, the tension bolts and the grout casting block can contract synchronously. This avoids the grout casting block being subjected to additional stress due to asynchronous contraction between the two, which would affect the structural stability of the grout casting block.

[0018] Specifically, the pressure frame is composed of two H-beams extending along a first axis, with their webs parallel to each other and their flanges welded together, forming a rectangular cavity between them. This rectangular cavity serves as the force application cavity. This design fully utilizes the structural stability of the H-beams themselves, as well as their standardization, reducing the amount of welding and enabling the equipment to be standardized.

[0019] Specifically, two spaced-apart connecting plates are provided on the side of the end plate away from the pressure seat. End plate holes for connecting tension bolts are provided on the end plates, and the space between the two connecting plates forms an operating space for tightening the nuts. This design facilitates tightening the nuts on the tension bolts, thus enabling tensioning of the bolts.

[0020] Furthermore, to reduce the adhesion of the high early strength grout to the piston rod, an anti-adhesion component is provided inside the pressure seat. This anti-adhesion component includes a positioning ring and a stretching ring, with the stretching ring being circular. The positioning ring is connected to the stretching ring via an elastic membrane or a stretching membrane. The positioning ring is fixed to the bearing plate or sleeved on the cylinder of the jack. When viewed along the first axis, the stretching ring is located inside the positioning ring and inside the piston hole.

[0021] A stepped portion is provided at the outer end of the piston rod of the jack. This stepped portion is formed by an axial indentation from the radially outer end of the outer end face of the piston rod, and has an annular stepped surface. The axial depth of this stepped portion is greater than or equal to the diameter of the tension ring. When the piston rod extends outward, the tension ring can be fitted onto the stepped portion and pressed against the stepped surface. The tension ring stretches the elastic or stretching membrane, causing it to wrap around the piston rod. To avoid the tension ring directly pressing against the transition piece during prestressing, which would affect the smooth application of prestress, the axial depth of the stepped portion is 0-5 mm greater than the diameter of the tension ring. The elastic membrane can be made of butadiene rubber, natural rubber, styrene-butadiene rubber, or nitrile rubber, or other rubbers. The stretching membrane is made of folded plastic film.

[0022] By utilizing the isolation effect of elastic or stretch membranes, the adhesion force of high early strength grout to the piston rod will be reduced, thereby reducing the tensile force on the piston rod when it retracts.

[0023] Furthermore, a concrete equalizing block is provided on the side of the force application cavity facing the pressure plate. This concrete equalizing block is formed by directly pouring concrete into the force application cavity, and the base of the jack rests against this concrete equalizing block. Using the concrete equalizing block, the reaction force generated by the jack during operation can be evenly distributed on the pressure plate, preventing localized deformation of the pressure plate due to excessive stress. Because the concrete equalizing block is formed by directly pouring concrete into the force application cavity, it is also actually bonded to part of the inner wall of the force application cavity, further distributing the reaction force generated by the jack more evenly. The thickness of the concrete equalizing block in the first axial direction is 100-300 mm.

[0024] Secondly, this application also proposes a prestressing application method, which uses the joint assembly described in any of the above claims, and the prestressing application method includes the following steps:

[0025] (1) Install the pressure seat on the horizontal support via the pressure plate, install the transition piece on a structural member, and set the end plate opposite to the end plate;

[0026] (2) Start the jack. The piston rod of the jack extends outward from the force application chamber and presses against the transition piece to push the transition piece until the pre-pressure produced by the push reaches the set value.

[0027] (3) Under the set tension, connect the two ends of the tension bolt to the pressure seat and the transition piece respectively, and then pour high early strength grout between the end plate and the end plate. When the high early strength grout reaches the set strength, release the pressure of the jack, retract the piston rod into the force application chamber, and remove the jack.

[0028] In this application, the prestress is 1.05-1.1 times the prestress set for the horizontal support.

[0029] The set strength of the above-mentioned high early strength grout is 20-30 MPa. The set tension is preferably 20-30 MPa.

[0030] Because the performance of high early strength grouting materials produced by different companies varies, it is necessary to conduct strength testing on the high early strength grouting materials used before construction to determine the pressure relief time of the jacks.

[0031] In this application, after the prestressing is applied, high-early-strength grout is poured between the end plates to form a grouting block. This grouting block replaces the steel wedges used in the prior art. The grouting block has high compressive strength and can withstand the resistance forces generated by the first and second structural components. Pre-tensioning the tension bolts allows them to undergo axial elastic deformation. After the jacks are removed, the grouting block is compressed and deformed under the pressure of the first and second structural components. Because the tension bolts are pre-tensioned, they can contract synchronously with the grouting block, preventing asynchronous contraction that could subject the grouting block to additional stress and affect its structural stability. The tension bolts ensure the stable holding of the grouting block between the end plates and the end plates, preventing it from being pulled outwards due to external vibrations. Using this application, even if the parallelism between the end plates is poor and there is a small angle, no adjustment is required. Using this application, there can be an angle of ≤5° between the end plate and the end head plate. Although this angle can be increased in actual construction, an excessively large angle will cause the end face of the piston rod of the jack to also form an angle with the end plate, which will increase the friction between the cylinder of the jack and the piston rod and affect the service life of the jack.

[0032] Furthermore, to reduce the adhesion between the grouting block and the end plate and end plate, so as to facilitate the subsequent removal of the joint assembly, a release agent is applied or a release film is adhered to the opposite sides of the end plate and end plate.

[0033] Furthermore, when an anti-sticking component is provided, as the piston rod extends outward into the force application chamber, the stretching ring is fitted onto the stepped portion of the piston rod and presses against the stepped surface. The stretching ring stretches the elastic or stretching membrane, causing it to wrap around the piston rod. The high-early-strength grout is then wrapped around the piston rod by the elastic or stretching membrane. Utilizing the isolating effect of the elastic or stretching membrane, the adhesion of the grout casting block to the piston rod is reduced, allowing the piston rod to retract smoothly.

[0034] Furthermore, when the pressure seat and transition piece are installed on the first and second structural components respectively, the gap between the end plates is ≤100mm. Preferably, the gap between the end plates is 5-80mm. If the distance between the horizontal support and the structural component is exactly equal to the total length of the pressure seat and transition piece in the first axial direction, the end plate will be tightly pressed against the end plate. During installation, whether one is installed first and then the other, or the pressure seat and transition piece are first bolted together and then placed between the horizontal support and the structural component, considerable force is required to insert the pressure seat and transition piece sequentially or all at once between the horizontal support and the structural component. Furthermore, alignment is required during installation to prevent deviation, which increases the operational difficulty. However, by setting a small gap between the end plates, ensuring that the distance between the horizontal support and the structural component is greater than the total length of the end plates in the first axial direction, both the pressure seat and the transition piece can be smoothly installed on the horizontal support and the structural component. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the first joint assembly after prestressing has been applied to the horizontal support.

[0036] Figure 2 This is a structural schematic diagram of the first connector assembly.

[0037] Figure 3 yes Figure 2 The exploded diagram.

[0038] Figure 4 This is a schematic diagram of the structure of the first pressure seat in the first connector assembly.

[0039] Figure 5 This is a structural diagram of the first pressure seat after the reinforcing plate has been removed.

[0040] Figure 6 yes Figure 5 A view from the center AA direction.

[0041] Figure 7 yes Figure 6 Enlarged view of section B.

[0042] Figure 8 yes Figure 7 Diagram showing the state of the piston rod of the jack when it extends outward.

[0043] Figure 9 A schematic diagram of the anti-stick component.

[0044] Figure 10 hour Figure 9 Enlarged view of section C.

[0045] Figure 11 A schematic diagram of the structure of the first transition piece in the first connector assembly.

[0046] Figure 12 This is a schematic diagram of the second joint assembly after prestressing has been applied to the corner brace.

[0047] Figure 13 This is a structural schematic diagram of the second connector assembly.

[0048] Figure 14 yes Figure 13 The exploded diagram.

[0049] Figure 15 This is a schematic diagram of the structure of the second pressure seat in the second connector assembly. Detailed Implementation

[0050] Example 1

[0051] See Figures 1-11 In the attached diagram, the first axis X extends horizontally, and the second axis Z extends vertically.

[0052] The first joint assembly 500, in this embodiment, is used to apply prestress to the horizontal support 513 erected on the capping beam 512, which is mounted on top of the retaining piles 511. The horizontal support 513 extends along the first axis. This horizontal support is a counter-bracing structure.

[0053] The first joint assembly 500 includes a first pressure seat 100 and a first transition member 200 spaced apart. In the figure, the first joint assembly is a schematic diagram after the prestressing is applied. There is a grouting block 300 between the first pressure seat 100 and the first transition member 200.

[0054] The first pressure seat 100 includes a pressure frame 13 extending along a first axis and a bearing plate 11 and an end plate 12 connected at both ends of the pressure frame along the first axis.

[0055] In this embodiment, the pressure frame 13 is formed by splicing two H-beams 131 extending along the first axis. The webs 132 of the two H-beams extend vertically and are parallel to each other. The upper flanges 133 of the two H-beams are welded together, and the lower flanges 134 are welded together, forming a rectangular cavity between the two H-beams. This rectangular cavity is the force application cavity 15. A piece is cut off from each of the opposite sides of the upper flanges of the two H-beams to form a rectangular inlet / outlet 14. The inlet / outlet is located on the upper side of the pressure frame and is used to enter and exit the force application cavity. Reinforcing plates 17 are detachably installed on the inlet / outlet using bolts.

[0056] A reinforcing plate 137 is welded to the outer side of the web 132. The two ends of the reinforcing plate along its first axis are welded to the bearing plate 11 and the end plate 12, respectively. A support plate 135 is horizontally welded to the lower side of the force-applying cavity. The jack 16 is located within the force-applying cavity 15 and is detachably mounted on the support plate 135. A concrete force-equalizing block 136 is poured into the inner side of the bearing plate 11, and the base 165 of the jack presses against this concrete block. The piston rod 161 of the jack can extend towards the end plate.

[0057] The concrete equalizing block 136 is formed by directly pouring concrete into the force application cavity, and the side of the concrete equalizing block facing the end plate is planar and perpendicular to the first axis. The base of the jack presses against the concrete equalizing block. It can be understood that, to maintain flatness, in another embodiment, a steel plate may also be laid on the side of the concrete equalizing block facing the end plate.

[0058] A piston hole 121 and a tension hole 122 are provided on the end plate 12. The piston hole 121 is square and faces the piston rod 161. The tension holes are arranged on the periphery of the end plate 12. A first bolt hole 111 is provided on the periphery of the pressure plate 11.

[0059] The first transition piece 200 includes an end plate 21, on the side of the end plate 21 away from the first pressure seat, two connecting plates 22 are welded together, the two connecting plates 22 are spaced apart, a reinforcing plate 23 is provided between the two connecting plates, and an end plate hole 211 for connecting tension bolts is provided on the end plate.

[0060] In this embodiment, the end plate and the end head plate are arranged opposite to each other and parallel to each other, with the end head plate perpendicular to the first axis. The end plate holes 211 and tension holes 122 are opposite to each other. The end plate holes are located between two adjacent reinforcing plates or between a connecting plate and an adjacent reinforcing plate, such that the space between two adjacent reinforcing plates and between a connecting plate and an adjacent reinforcing plate forms an operating space 213 for tightening the nut, that is, the space between two connecting plates forms an operating space for tightening the nut. A second bolt hole 221 is provided on the connecting plate.

[0061] The piston rod 161 of the jack 16 can extend along the first axis towards the first transition member, and after extending outward through the piston hole into the force application chamber, press against the first transition member to push it. The two ends of the tension bolt 40 pass through the tension hole 122 and the end plate hole 211 respectively and are connected to the first pressure seat and the first transition member.

[0062] Please also refer to Figures 7-10 In this embodiment, an anti-sticking component 18 is provided inside the first pressure seat. The anti-sticking component 18 includes a positioning ring 181 and a stretching ring 183. Both the positioning ring and the stretching ring are annular, and the outer diameter of the stretching ring is smaller than the inner diameter of the positioning ring. The positioning ring 181 is connected to the stretching ring 183 via an elastic membrane 182. The positioning ring is fixedly bonded to the edge of the piston hole facing the pressure plate. Viewed along the first axis, the stretching ring is located inside the positioning ring and within the piston hole. In this application, the elastic membrane is an annular rubber sheet. The outer circumferential end of the rubber sheet is bonded to the positioning ring, and the edge of the central hole of the rubber ring is bonded to the stretching ring. In this application, for ease of processing, the piston hole is square. Of course, in another embodiment, the piston hole can also be circular.

[0063] A stepped portion 163 is provided at the outer end of the piston rod 161 of the jack 16. The stepped portion 163 is formed by the radially outer end of the outer end face 162 of the piston rod being recessed axially. The stepped portion has an annular stepped surface 164. The axial depth H of the stepped portion 163 is 2mm larger than the diameter of the ring body of the drawing ring 183. This ensures that when the drawing ring presses against the stepped surface 164, the side of the drawing ring away from the pressure plate does not extend beyond the outer end face 162 of the piston rod. This prevents the drawing ring from directly pressing against the first transition member during the application of prestress, thus avoiding the smooth application of prestress.

[0064] When the piston rod extends outward, the stretching ring can be fitted onto the stepped portion and press against the stepped surface, stretching the elastic membrane to form a cylindrical shape that wraps around the outer circumference of the piston rod. In this embodiment, the elastic membrane is made of butadiene rubber. It is understood that in other embodiments, the elastic membrane can also be made of natural rubber, styrene-butadiene rubber, or nitrile rubber, or other rubber materials.

[0065] The first pressure seat and the first transition piece can be installed on one end of the horizontal support and the crown beam, respectively, so that the end plate and the end plate are set opposite each other. Then, the piston rod of the jack extends along the first axis toward the transition piece, and extends outward through the piston hole to the force application chamber and presses against the end plate to push the transition piece. After the push is completed, the nut tensions the tension bolt. After completion, high early strength grout is poured into the gap between the end plate and the end plate to form a grout casting block. The tension bolt passes through the grout casting block.

[0066] The following describes the method of applying prestress using the joint assembly in this embodiment. In this embodiment, prestress is applied to the horizontal support 513, which will also generate corresponding stress on the cap beam 512.

[0067] When applying prestress to the horizontal support 513 using the joint assembly in this embodiment, the specific steps are as follows:

[0068] (1) Using bolts, the first pressure seat is installed on the end of the horizontal support 513 facing the crown beam 512 through the first bolt hole 111 on the bearing plate, and the first transition piece 21 is installed on the side of the crown beam facing the horizontal support 513 through the second bolt hole 221. In this embodiment, the crown beam 512 is a reinforced concrete structure, specifically using H steel A as the outer frame, and concrete is poured inside the outer frame, with the concrete poured on the top of the support pile 511. The H steel A extends horizontally, and the flange of the H steel A is set horizontally. The connecting plate 22 of the first transition piece 21 is connected to the flange of the H steel A, and the connecting plate 22 is parallel to the web of the crown beam.

[0069] For ease of installation, the distance between the capping beam and the horizontal support should ideally be greater than the total length of the first pressure seat and the first transition piece along the first axis. In this embodiment, the distance between the capping beam and the horizontal support is 10mm greater than the total length of the first pressure seat and the first transition piece along the first axis. That is, after the installation of the first pressure seat and the first transition piece is completed, there is a 10mm gap between the end plate of the first pressure seat and the end plate of the first transition piece. The first pressure seat and the first transition piece need to be prefabricated, and the capping beam and the horizontal support are constructed later. There will always be some errors in the construction process, and sometimes the actual distance between the capping beam and the horizontal support will be less than the set distance. In this case, the installation of the first pressure seat and the first transition piece cannot be completed smoothly, and the first transition piece must be temporarily cut and modified, or the first transition piece must be remade. The distance between the capping beam and the horizontal support should exceed the total length of the first pressure seat and the first transition piece. This not only compensates for construction errors but also allows for faster installation of the first pressure seat and the first transition piece. However, the distance between the capping beam and the horizontal support should not be too large. After the first pressure seat and the first transition piece are installed, the gap between the end plates should be ≤100mm. However, if the gap between the end plate of the first pressure seat and the end plate of the first transition piece is too small, it will not be conducive to the rapid installation of the first pressure seat and the first transition piece. It is recommended that the distance between the capping beam and the horizontal support be 5-100mm larger than the total length of the first pressure seat and the first transition piece in the first axial direction.

[0070] A release varnish is applied to both sides of the end plate and the opposite side of the end plate. The release varnish can be applied before installation or after the jacking is completed in the subsequent step (2). The release varnish application only needs to be completed before the pouring of the high early strength grout. It is understood that in another embodiment, a release film can also be attached to the sides of the end plate and the opposite side of the end plate. The release film can be a thin metal sheet, a plastic film, or a plastic sheet, as long as it can reduce the bonding strength between the high early strength grout and the end plate and the end plate.

[0071] After the installation of the first pressure seat and the first transition piece is completed, the two ends of the tension bolt 40 are respectively inserted into the tension hole 122 and the end plate hole 211.

[0072] Place the jack 16 inside the force application chamber and install and fix it so that the base of the jack presses against the side of the concrete equalizing block facing the end plate, and the piston rod is directly opposite the piston hole.

[0073] (2) Start jack 16. After the piston rod of the jack extends outward into the force application chamber, it presses against the first transition piece and pushes the first transition piece to generate prestress in both the horizontal support and the crown beam until the pre-applied pressure generated by the push reaches the set value. In this embodiment, the set value of the pre-applied pressure is 1.08 times the set prestress of the horizontal support.

[0074] When the piston rod extends outward into the force application chamber, the stretching ring is fitted onto the stepped part of the piston rod and presses against the stepped surface. The stretching ring stretches the elastic membrane, causing the elastic membrane to form a cylindrical shape and wrap around the piston rod.

[0075] (3) Tighten the nut on the tension bolt to make the tension of the tension bolt reach 25MPa. That is, under the set tension of 25MPa, connect the two ends of the tension bolt to the first pressure seat and the first transition piece respectively. Then, pour high early strength grout between the end plate and the end plate. The high early strength grout is wrapped on the outer circumference of the piston rod through the elastic membrane and wrapped on the tension bolt. After curing, the high early strength grout forms a grout casting block 300 bonded to the tension bolt. That is, the tension bolt passes through the grout casting block and is bonded to the grout casting block.

[0076] The tension bolt is a single-ended bolt, with the bolt head located on the side of the end plate away from the end plate, and the nut on the tension bolt located on the side of the end plate away from the end plate.

[0077] Once the high early strength grout reaches the set strength of 25MPa, release the pressure from the jack, retract the piston rod into the force application chamber, and remove the jack.

[0078] Example 2

[0079] This embodiment is basically the same as Embodiment 1, but is a modification based on Embodiment 1, in order to apply prestress to different horizontal supports.

[0080] Please see Figures 12-14 The first axis X in the attached figure extends in the horizontal direction.

[0081] The second joint assembly 600 is used to apply prestress to the corner brace 613 erected on the waler 612, which is located inside the retaining pile A611. The corner brace 613 extends along the first axis X and is inclined relative to the waler, with a second included angle β of 45° between the corner brace and the waler. In actual construction, the second included angle β is allowed to deviate due to construction and processing errors, and this deviation needs to be controlled within ≤5°.

[0082] The second connector assembly 600 specifically includes a second pressure seat 621 and a second transition member 622.

[0083] The second pressure seat 621 has a structure basically the same as the first pressure seat. Specifically, the second pressure seat 621 includes a pressure frame A630 extending along the first axis, and a bearing plate A631 and an end plate A632 connected to both ends of the pressure frame A630 along the first axis. The first included angle α between the end plate A632 of the second pressure seat 621 and the first axis X is 45°. Other structural features of the second pressure seat A621 can be manufactured with reference to the first pressure seat. The second pressure seat 621 is mounted on the end of the corner brace 613 via the bearing plate A631.

[0084] The second transition piece 622 has a structure basically the same as the first transition piece. Specifically, it includes an end plate A641, which is parallel to and opposite to the end plate A632. A connecting plate A642 is welded to the side of the end plate A641 away from the end plate A632, and a second bolt hole A645 is provided on the connecting plate A642. Bolts connect the second transition piece 622 to the waler 612 through the second bolt hole A645. The waler 612 is made of H steel B with horizontally arranged flanges. The second transition piece 622 is connected to the flange of the H steel B, making the end plate A641 parallel to the web of the H steel B.

[0085] The two ends of the tension bolt A623 are connected to the end plate A641 and the end plate A632, respectively. After the jacking is completed using the jack A633 described below, high early strength grout is poured into the end plate A641 and the end plate A632 to form a grout casting block.

[0086] To ensure the piston rod of jack A633 smoothly pushes the second transition piece 622, a pushing component 644 is welded to the side of end plate A641 facing end plate A632. The pushing component 644 has a pushing surface 643, which is parallel to the end face of the piston rod, allowing the entire end face of the piston rod to press against the pushing surface to push the second transition piece 622. This pushing component is made of steel pipe, and a steel plate is welded to the side of the steel pipe facing end plate A632. The surface of the steel plate facing end plate A632 becomes the pushing surface.

[0087] In this embodiment, the anti-sticking component includes a positioning ring and a stretching ring, both of which are annular in shape, with the outer diameter of the stretching ring being smaller than the inner diameter of the positioning ring. The positioning ring is connected to the stretching ring via a telescopic membrane, and the positioning ring is fixedly bonded to the cylinder of the jack. The telescopic membrane is made of folded plastic film, which unfolds and wraps around the outer circumference of the piston rod when the stretching ring moves under the drive of the piston rod.

[0088] Although this embodiment sets the second included angle β between the corner brace and the waler to 45°, in actual construction, due to interference from other factors and errors in the construction itself, the angle of the second included angle β may increase or decrease. At the same time, the end plate A632 and the end plate A641 will no longer be parallel, resulting in a small angle. This small angle is best controlled within 5°. If it exceeds 5°, the position of the transition plate A on the waler needs to be adjusted, and the angle between the end plate A632 and the end plate A641 should be lowered and made as parallel as possible.

[0089] In this embodiment, the method for applying prestress to the corner brace can be the same as in Example 1.

[0090] Since the edge of the foundation pit is not always regular, depending on the specific needs, the first included angle α between the end plate A632 and the first axis X can also be 30°, 35°, 40°, 50° or 60°, or of course other angles between 30° and 60°.

[0091] In the two embodiments described above, the joint assembly is located between the support and the cap beam, and between the corner brace and the waler, respectively. However, depending on the specific construction conditions and ease of construction, the support or corner brace can also be divided into two support sections, and the joint assembly can be placed between the two support sections.

Claims

1. A joint assembly for applying prestress, characterized in that, The device includes a pressure seat and a transition piece arranged at intervals. The pressure seat includes a pressure frame extending along a first axis and a bearing plate and an end plate fixedly installed at both ends of the pressure frame along the first axis. A force-applying cavity is provided inside the pressure frame, and an inlet and outlet for entering and exiting the force-applying cavity are provided on one side of the pressure frame. A jack is detachably installed in the force-applying cavity, and a piston hole is provided on the end plate. The transition piece includes an end plate, which is arranged opposite to the end plate. The end plate and the end plate are parallel to each other or have an included angle of ≤5°. The two ends of a tension bolt are respectively connected to the pressure seat and the transition piece. The joint assembly can be installed between a horizontal support and a structural member to apply prestress to the horizontal support. When the joint assembly is used to apply prestress to the horizontal support, the piston rod of the jack pushes the transition member. After the push is completed, high early strength grout is poured into the gap between the end plate and the end plate to form a grout casting block. The horizontal support is either a brace or a corner brace. When the horizontal support is a brace, the end plate is perpendicular to the first axis. When the horizontal support is a corner brace, the angle between the end plate and the first axis is 30-60°.

2. The connector assembly according to claim 1, characterized in that, After the jacking is completed, the tension bolts are tensioned using nuts. Then, high early strength grout is poured into the gap between the end plate and the end plate to form a grout casting block. The tension bolts pass through the grout casting block.

3. The connector assembly according to claim 1, characterized in that, The pressure frame is made up of two H-beams extending along the first axis. The webs of the two H-beams are parallel to each other, and the flanges of the two H-beams are welded together to form a rectangular cavity between the two H-beams. This rectangular cavity is the force application cavity.

4. The connector assembly according to claim 1, characterized in that, Two spaced connecting plates are provided on the side of the end plate away from the pressure seat. End plate holes for connecting tension bolts are provided on the end plate. The space between the two connecting plates forms an operating space for tightening nuts.

5. The connector assembly according to claim 1, characterized in that, An anti-sticking component is provided inside the pressure seat. The anti-sticking component includes a positioning ring and a stretching ring. The stretching ring is circular. The positioning ring is connected to the stretching ring via an elastic membrane or a stretching membrane. The positioning ring is fixed on the pressure plate or sleeved on the cylinder of the jack. When viewed along the first axis, the stretching ring is located inside the positioning ring and inside the piston hole. A stepped portion is provided at the outer end of the piston rod of the jack. The stepped portion is formed by the radially outer end of the outer end face of the piston rod being recessed axially. The stepped portion has an annular stepped surface. The axial depth of the stepped portion is greater than or equal to the diameter of the stretching ring. When the piston rod extends outward, the stretching ring is sleeved on the stepped portion and presses against the stepped surface. The stretching ring stretches the elastic membrane or the stretching membrane, so that the elastic membrane or the stretching membrane wraps around the piston rod.

6. The connector assembly according to claim 1, characterized in that, There is a concrete equalizing block on the side of the force application cavity facing the pressure plate. The concrete equalizing block is formed by concrete poured directly into the force application cavity, and the base of the jack presses against the concrete equalizing block.

7. A method for applying prestress, characterized in that, The prestressing method, using the joint assembly according to any one of claims 1-6, comprises the following steps: (1) Install the pressure seat on the horizontal support via the pressure plate, install the transition piece on a structural member, and set the end plate opposite to the end plate; (2) Start the jack. The piston rod of the jack extends outward from the force application chamber and presses against the transition piece to push the transition piece until the pre-pressure produced by the push reaches the set value. (3) Connect the two ends of the tension bolt to the pressure seat and the transition piece respectively under the set tension. Then pour high early strength grout between the end plate and the end plate. When the high early strength grout reaches the set strength, release the pressure of the jack, retract the piston rod into the force application chamber, and remove the jack.

8. The prestressing application method according to claim 7, characterized in that, A release agent is applied or a release film is affixed to both the end plate and the opposite sides of the end plate.

9. The prestressing application method according to claim 7, characterized in that, An anti-sticking component is provided inside the pressure seat. The anti-sticking component includes a positioning ring and a stretching ring. The stretching ring is circular. The positioning ring is connected to the stretching ring via an elastic membrane or a stretching membrane. The positioning ring is fixed on the pressure plate or sleeved on the cylinder of the jack. When viewed along the first axis, the stretching ring is located inside the positioning ring and inside the piston hole. A stepped portion is provided at the outer end of the piston rod of the jack. The stepped portion is formed by the radially outer end of the outer end face of the piston rod being recessed axially. The stepped portion has an annular stepped surface. The axial depth of the stepped portion is greater than or equal to the diameter of the drawing ring. When the piston rod extends outward into the force application chamber, the stretching ring is fitted onto the stepped part of the piston rod and presses against the stepped surface. The stretching ring stretches the elastic membrane or telescopic membrane, so that the elastic membrane or telescopic membrane wraps around the piston rod. The high early strength grout is wrapped around the piston rod by the elastic membrane or telescopic membrane.

10. The prestressing application method according to claim 7, characterized in that, When the pressure seat and transition piece are installed on the horizontal support and structural piece respectively, the gap between the end plate and the end plate shall be ≤100mm.

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