Boxed connection horizontal joint with built-in self-regulating pre-press device

Abstract

The application discloses a box type connection horizontal joint node with built-in self-adjusting pre-pressing device, which is suitable for assembly type prefabricated shear walls. The node is provided with a built-in pre-pressing device below a connecting box or near a horizontal joint based on a traditional box type connection, and the pre-pressing device is composed of a steel support plate and a wedge-shaped block or a screw rod jack assembly. The pre-pressing device cooperates with vertical stress reinforcement and box type connecting pieces, and does not participate in the main bending reinforcement. The structure converts the test rule that 'increasing the axial compression ratio can enhance the joint shear resistance' into a local and adjustable mechanical pre-pressing means, realizes active control of effective normal pressure of the box type connection horizontal joint, significantly improves the interface friction shear bearing capacity and long-term stability, and solves the problem that the construction of the existing prefabricated shear wall horizontal joint is difficult to guarantee the normal pressure.

Description

Technical Field

[0001] This invention relates to the field of prefabricated concrete structure engineering technology, specifically to a box-type connection node structure suitable for precast shear walls, and particularly to a built-in self-adjusting preloading device and its application node that is arranged near the horizontal joint of the box-type connection and can actively adjust the effective normal pressure of the horizontal joint during construction and use. Background Technology

[0002] Precast concrete shear wall structures have been widely adopted in recent years due to their advantages such as saving formwork, accelerating construction speed, and facilitating industrialized production. For precast shear walls, the horizontal joints between the upper and lower wall segments are critical areas for shear and hysteretic energy dissipation, and their mechanical properties directly affect the overall seismic safety and durability of the structure. Current design codes for precast shear walls generally adopt the "shear friction" design method, which expresses the shear capacity of the horizontal joint as the sum of the tensile contribution of the vertical reinforcement passing through the joint surface and the contribution of the normal compressive force. For example, some local standards recommend the following calculation formula: ,in, This refers to the design value of the tensile strength of the reinforcing bar or bolt that passes perpendicularly through the joint surface. This refers to the cross-sectional area of ​​this type of steel reinforcement. The design value for the normal pressure perpendicular to the joint interface. This is a coefficient that takes into account the roughness of the interface. As can be seen from the formula, increasing the vertical normal pressure within a certain range is beneficial to significantly improve the shear capacity and frictional energy dissipation capacity of the joint.

[0003] Numerous experimental and theoretical studies have demonstrated that, under the same reinforcement conditions, increasing the axial compression ratio or applying prestress can significantly improve the shear capacity and initial stiffness of the joints, and enhance the fullness of the hysteresis curve. For example, prestressed self-resetting shear walls with bottom horizontal joints achieve self-resetting after tension and high shear capacity by arranging vertical prestressing tendons. Friction performance tests on prestressed slab-column joints also show that increasing the applied prestress can significantly improve the frictional bearing capacity of the joint interface. Furthermore, many scholars have conducted low-cycle reciprocating loading tests on precast shear walls, composite walls, and steel-concrete shear walls under different axial compression ratios, systematically analyzing the impact of axial pressure on the failure mode, bearing capacity, and energy dissipation capacity of the walls.

[0004] In engineering practice and existing patented technologies, various structural forms have been developed for the connection of prefabricated shear walls. For example, a horizontal bolt connection structure for prefabricated shear walls is adopted, using rolled-edge channel steel, T-shaped high-strength bolts, and steel plates with elongated holes to connect the wall panels and ensure the force transmission of the horizontal joints; some patents propose to improve the shear resistance of horizontal and vertical joints through measures such as concealed steel columns, shear keys, and keyways; and many technical specifications require the installation of rough surfaces, shear keys, anchor bars, or grouting sleeves at horizontal joints to enhance mechanical interlocking and interfacial bonding strength. While the aforementioned technologies help improve the shear resistance of joints, they share the following characteristics: 1) Passive source of normal pressure: The normal pressure at the joint interface mainly relies on the overall structural axial force or vertical prestressing tendons. Designers can only indirectly affect the normal pressure of the joint by adjusting the wall cross-section dimensions, the arrangement of vertical reinforcing bars, or the number and tension of prestressing tendons; 2) Prestressing cannot be locally and adjustablely controlled: Prestressed shear walls often have prestressing tendons arranged along the entire height of the wall limb, resulting in a large pressure range, which is not conducive to localized and precise control of horizontal joints near the box-type connection; at the same time, once tensioning is completed, the degree of prestress is difficult to flexibly adjust during the service stage. 3) Uncertainty of normal pressure during construction and long-term condition: The construction quality of horizontal joint concrete (or grouting material), interface bonding, and long-term effects such as shrinkage and creep in the project will directly affect the actual normal pressure; however, existing structures rarely provide measurable and adjustable built-in components to control this "effective normal pressure"; 4) Existing loading devices are mostly external devices for testing: such as precast component joint shear strength testing devices, shear wall seismic performance testing loading frames, etc., usually apply vertical pressure to the specimen through external hydraulic jacks, and are only used in the laboratory to simulate working conditions with different axial compression ratios, and are not built-in structures that can be left in actual projects for a long time.

[0005] On the other hand, with the development of prefabricated high-rise buildings, box-type shear walls are widely used due to their excellent vertical reinforcement anchorage and assembly precision. Box-type connections typically involve pre-embedded steel boxes, reinforcing steel plates, and longitudinal reinforcement, combined with grouting or cast-in-place concrete to connect the upper and lower wall segments. The horizontal joints are often located at the points where the bending and shear forces on the wall segments are most significant. Current improvements to box-type connections focus more on the shape of the steel boxes, reinforcement anchorage, and shear key design. There is a lack of solutions that include locally installed, long-term, and repeatedly adjustable built-in pre-stressing devices near the box-type connection to actively control the effective normal pressure at the horizontal joint interface, thereby directly improving frictional shear resistance.

[0006] In summary, while existing technologies recognize the importance of normal pressure on the shear resistance of joints and have proposed a series of methods such as axial compression ratio control, prestressed tendon arrangement, shear keys, and rough interfaces, the following prominent problems still exist: 1) Normal pressure relies entirely on the overall axial force or prestress, and cannot be locally and adjustablely controlled for horizontal joints in box-type connections; 2) There is a lack of built-in mechanical prestressing devices that can be repeatedly adjusted during construction and use and work permanently as an integral part of the wall; 3) It is difficult to guarantee the interface bonding quality during construction and the stability of normal pressure during long-term service, resulting in significant uncertainty in the frictional shear bearing capacity of horizontal joints; 4) Existing test loading devices related to joint shear resistance are external tools and are not permanent node structures that can be extended to practical engineering applications.

[0007] Therefore, it is necessary to propose a built-in prestressing device that is integrated with box-type connections, can be locally arranged near the horizontal joint, and has adjustable and monitorable functions. This would enable designers, construction and operation and maintenance personnel to actively control the effective normal pressure of the joint, and transform the research conclusion of "increasing the axial compression ratio" into a structural measure at the node level, thereby improving the frictional shear bearing capacity and long-term safety of the horizontal joint of the prefabricated shear wall. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing precast shear wall box-type horizontal joint nodes, where the normal pressure relies entirely on the overall axial force, is difficult to control precisely locally, and cannot be flexibly adjusted during use, and to provide a box-type horizontal joint node with a built-in self-adjusting pre-compression device.

[0009] By arranging a built-in prestressing device below the box-type connection or near the horizontal joint, this invention achieves the following technical effects: 1) It transforms the experimental conclusion that "increasing the axial compression ratio can enhance the shear bearing capacity of the joint" into a mechanical prestressing method that can be implemented locally at the node, forming "locally adjustable prestressing" rather than "overall passive axial compression"; 2) It constructs a built-in prestressing system near the horizontal joint that can be left for a long time and adjusted multiple times during construction and use, transforming the node normal pressure from an "uncontrollable variable" into a "monitorable, designable, and maintainable" structural parameter; 3) The prestressing device works in conjunction with the vertical reinforcing steel and the box-type connector but functions independently, without changing the original bending reinforcement system. It significantly improves the interface friction shear bearing capacity through additional normal pressure, reducing the sensitivity of the joint bonding quality and long-term shrinkage and creep; 4) It limits the prestressing range to the horizontal joint area near the box-type connection, avoiding the application of unnecessary additional prestress to the entire wall, making the control more precise, and facilitating selective configuration at specific high-rise key nodes.

[0010] To achieve the above objectives, the technical solution proposed by this invention is summarized as follows:

[0011] 1) Based on the traditional box-type connection, a steel support plate arranged along the wall thickness is pre-embedded in the lower wall limb. This support plate is reliably anchored to the concrete by shear studs, bolts, or anchor bars to support the reaction force generated by the built-in preloading device. The steel support plate can be located directly below the bottom of the box-type connection box, or slightly off-center from the horizontal joint, but it must ensure that the connection path between it and the bottom surface of the upper wall limb has high rigidity to effectively transmit the vertical clamping force.

[0012] 2) An internal preloading device is installed between the steel support plate and the bottom surface of the upper wall limb. This internal preloading device can be a wedge block assembly, a screw jack assembly, or a combination of both. The wedge block assembly changes its overall height by sliding pairs of wedges relative to each other, thereby applying vertical clamping force to the upper wall limb. The screw jack assembly generates controllable preloading by tightening the screw, causing its top plate to press against the bottom surface of the upper wall limb. Both types can be driven using operating ends on the side of the wall or the floor slab for convenient construction and subsequent maintenance.

[0013] 3) Provide guide holes or openings in the connection box to guide the pressure application end of the built-in preloading device to a reachable location outside the wall. The guide holes should be fitted with waterproof sleeves, water-stop rings, and sealing structures to ensure that the preloading device can be operated multiple times without affecting the structure and waterproofing performance.

[0014] 4) Install pressure sensors and / or displacement gauges near the preloading device to monitor the preloading value and joint deformation. Specifically: pressure sensors can be placed on the wedge contact surface, top pressure plate, or support plate to directly or indirectly measure the applied vertical pressure; displacement gauges can be placed on the scale positions on both sides of the horizontal joint or inside the guide hole to monitor the opening of the horizontal joint, slippage, or the working displacement of the preloading device.

[0015] The above monitoring methods can be used to accurately control the initial preload value during the construction phase and continuously monitor the working status of nodes during the structural use phase.

[0016] 5) At the structural design level, the additional normal pressure provided by the built-in preloading device will be incorporated. Incorporating this into shear friction design calculations, for example, the shear capacity of a horizontal joint can be approximated as: ,in, The coefficient of interfacial friction, The normal pressure is generated by the structure's self-weight and vertical loads. Additional normal pressure provided for the built-in preload device, The shear capacity contributed by the tensile reinforcement horizontally passing through the joint surface. This is determined through reasonable allocation. This can improve the shear capacity of horizontal joints without significantly increasing the cross-section and reinforcement of the wall limbs.

[0017] 6) During the construction phase, implement the following steps: When prefabricating or casting the lower wall limbs, embed steel support plates, box-type connectors, and guide holes; hoist the upper wall limbs, aligning their bottom surfaces with the top of the lower wall limbs and the box-type connectors, and complete the longitudinal reinforcement butt joints or grouting connections; through the operating end of the guide hole, drive the built-in pre-stressing device to apply pre-tightening force to achieve the designed pre-stressing value; use a pressure sensor or displacement gauge to verify the pre-stressing effect, and protect and waterproof the operating end.

[0018] 7) During the structural use phase, when the horizontal joint opening or slippage exceeds the set threshold, or when the preload decay is found to be significant according to periodic inspections, the built-in preload device can be driven again through the operating end, such as by tightening the screw jack or replacing it with a larger wedge block, to restore or increase the normal pressure, thereby enhancing the shear resistance and deformation control capability of the joint.

[0019] Through the above technical solution, the present invention achieves active, local, and adjustable control of the effective normal pressure of the horizontal joint of the box-type connection, filling the gap in this aspect of the existing prefabricated shear wall node structure. Attached Figure Description

[0020] To more clearly illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings. The accompanying drawings are used to illustrate one or more preferred embodiments of the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0021] Figure 1 This is a schematic diagram (elevation section view) of the overall structure of the box-type horizontal joint node with built-in self-adjusting pre-compression device of the present invention.

[0022] Figure 2 This is a schematic diagram of a built-in preload device in the form of a wedge block assembly.

[0023] Figure 3 This is a schematic diagram of a built-in preload device in the form of a screw jack assembly.

[0024] Figure 4 This is a schematic diagram of the pre-compression operation end and guide hole structure of the node of the present invention at the floor slab.

[0025] Figure 5 This is a schematic diagram of node monitoring and adjustment according to the present invention. Detailed Implementation

[0026] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention; without departing from the essence of the present invention, those skilled in the art can make various modifications or substitutions to the component dimensions, materials, arrangement positions and transmission methods as needed, and all such modifications or substitutions should fall within the scope of protection of the present invention.

[0027] Example 1: Box-type horizontal joint node in the form of wedge block preloading device

[0028] 1. Overall Node Structure

[0029] like Figure 1 , Figure 2 As shown, the box-type horizontal joint node in this embodiment includes a lower wall limb 1, an upper wall limb 2, a horizontal joint 3 located between the two, and a box-type connecting steel reinforcement connection box 4 arranged in the joint area. The vertical connecting steel reinforcement 5 has a pre-reserved protruding section when the lower wall limb 1 is precast or cast in place, and the corresponding sleeve or steel reinforcement in the connection box 4 is embedded in the upper wall limb 2, and a reliable connection is achieved with the lower wall limb steel reinforcement by means of grout injection or welding.

[0030] Inside the lower wall segment 1, a steel support plate 6 is pre-embedded near the horizontal joint 3. The steel support plate 6 is basically continuous along the thickness direction of the wall segment, and its length is the same as or slightly shorter than the horizontal length of the wall segment. It forms a combined force with the concrete by arranging shear studs, studs or rebars to ensure that it does not produce obvious slippage or local damage when bearing the preload reaction force transmitted from the upper wall segment 2.

[0031] An internal preloading device 7 is arranged between the steel support plate 6 and the bottom surface of the upper wall limb 2. In this embodiment, a wedge block assembly is used. To facilitate the application and adjustment of preloading, a guide hole 8 is provided on one side of the wall limb. A waterproof sleeve and a sealing layer 9 are fitted outside the guide hole 8. A wedge block drive screw 15 or a tie rod is inserted into the guide hole, so that the wedge block assembly can be applied to the wall from the outside.

[0032] A pressure sensor 10 and a displacement gauge 11 are installed near the horizontal joint 3 or near the steel support plate 6. The pressure sensor 10 can be arranged on the upper surface of the support plate 6 or at the wedge contact surface to reflect the upward clamping force of the wedge; the displacement gauge 11 can monitor the relative displacement of the upper and lower wall segments or the wedge stroke, thereby indirectly evaluating the compression and opening status of the horizontal joint.

[0033] 2. Structure and working principle of the wedge block assembly

[0034] like Figure 2 As shown, the wedge block assembly mainly includes: a lower wedge seat 12 fixed on a steel support plate 6; an upper wedge block 13 that can slide relative to the upper wedge block in a basically vertical direction (with slight inclination for self-locking); a pad plate 18 disposed between the upper wedge block 13 and the bottom surface of the upper wall limb 2; a wedge block drive screw 15 connected to the upper wedge block 13 through a guide hole 8; and an exposed operating head 16.

[0035] The upper surface of the lower wedge 12 is machined into an inclined surface, or is composed of two or more inclined surfaces, and the lower surface of the upper wedge 13 forms a matching inclined surface 14. The upper surface of the upper wedge 13 is provided with a top pressure surface 17, and directly contacts the bottom concrete of the upper wall limb 2 through a pad plate 18. The pad plate 18 can be made of thickened steel plate or locally enlarged bearing plate as needed to avoid local concrete crushing.

[0036] One end of the wedge drive screw 15 is fixedly connected to the upper wedge 13 or connected via a pin, and the other end extends along the guide hole 8 to the outside of the wall, forming an operating head 16. The operating head 16 can be made into a hexagonal nut, a square head, or a spline head that mates with a special socket wrench. Construction or maintenance personnel can rotate the operating head 16 to drive the wedge drive screw 15 to move along the wall thickness direction, thereby causing the upper wedge 13 to slide along the wedge-shaped inclined surface 14.

[0037] When the upper wedge 13 slides upward along the inclined plane 14, the overlap between it and the lower wedge seat 12 increases, causing the pad 18 to press upward against the bottom surface of the upper wall limb 2, thus increasing the vertical clamping force between the upper and lower wall limbs. Conversely, if the upper wedge 13 slides downward along the inclined plane 14, the preload decreases. By changing the wedge slope angle, the coefficient of friction, and the transmission ratio of the drive screw 15, a larger preload amplification effect can be obtained with a smaller operating force.

[0038] To ensure the stability and safety of preloading, anti-slip teeth or a high-friction coefficient surface treatment can be provided between the inclined surface 14 of the wedge block and the lower wedge seat 12; alternatively, a limiting pin or a two-way stop can be added between the upper wedge block 13 and the lower wedge seat 12 to limit the maximum sliding stroke of the upper wedge block 13 and avoid excessive local compressive stress in the wall due to misoperation.

[0039] 3. Preloading Implementation Steps during Construction Phase

[0040] (1) Precast or cast-in-place lower wall segments

[0041] When prefabricating or casting the lower wall segment 1 in the factory, pre-embed box-type connecting steel reinforcement boxes 4 and vertical connecting steel reinforcement 5 according to design requirements, and simultaneously pre-embed steel support plates 6 and lower wedge seats 12. Arrange shear studs or studs near the steel support plate 6 to form a reliable bond with the concrete. Reserve the position of guide holes 8 and install waterproof sleeves 9.

[0042] (2) Hoist the wall-mounted components and complete the box-type connection.

[0043] After the lower wall segment concrete reaches its design strength, the upper wall segment 2 is hoisted into place, with its bottom surface adhering to the top of the lower wall segment 1. At the same time, the vertical connecting steel bars 5 and the corresponding positions of the connecting box 4 are aligned, and the grouting or welding connection is completed. At this time, the horizontal joint 3 is formed, and the upper and lower wall segments have a certain contact pressure under their own weight.

[0044] (3) Install the upper wedge and drive mechanism

[0045] Install the wedge drive screw 15 in the guide hole 8, and insert the upper wedge 13 from the side or from bottom to top between the lower wedge seat 12 and the pad 18, so that its lower surface mates with the inclined surface 14 of the lower wedge seat 12, and its upper surface contacts the bottom surface of the upper wall member 2 through the pad 18. Check the relative position and movement space between the wedge assembly and the guide hole 8.

[0046] (4) Apply preload

[0047] Using a torque wrench or special tool, rotate the operating head 16 to drive the upper wedge 13 to slowly slide upwards along the inclined plane 14 until the pressure value reflected by the pressure sensor 10 or the deformation reflected by the displacement gauge 11 reaches the design preload value. At this time, the horizontal joint 3 between the upper and lower wall limbs obtains a large effective normal pressure under the combined action of the overall self-weight and the preload of the wedge.

[0048] (5) Locking and Protection

[0049] After the pre-pressure target is reached, a locking nut or wedge self-locking device can be added to the drive screw 15 to ensure that the wedge will not automatically retract under normal vibration and temperature changes; then, the outside of the guide hole 8 is sealed and waterproofed, and a protective cover or decorative shield is installed without affecting subsequent maintenance operations.

[0050] 4. Monitoring and secondary adjustment during the usage phase

[0051] During the structural service phase, the working status of the horizontal joint 3 is monitored in real time or periodically using pressure sensor 10 and displacement gauge 11. Maintenance personnel may consider secondary adjustment of the preload if any of the following conditions are observed: displacement gauge 11 shows a significant increase in the opening or slippage of the horizontal joint, approaching or exceeding the design allowable value; pressure sensor 10 shows a significant long-term decay of the preload value, falling below a certain percentage of the initial preload; or the structure has experienced a rare earthquake, requiring re-application of preload to restore the shear resistance of the joints.

[0052] The secondary adjustment is similar to the construction phase. Maintenance personnel open the protective cover and use a special wrench through the guide hole 8 to rotate the operating head 16 again, causing the upper wedge 13 to continue sliding upwards along the slope 14, increasing the preload. In addition, if the wedge stroke is close to its limit, it can be replaced with a wedge with a larger slope or height after removing part of the preload to obtain new preload adjustment space.

[0053] Example 2: Node in the form of a screw jack preloading device

[0054] 1. Structural Composition

[0055] like Figure 3As shown, in this embodiment, the built-in preload device 7 is replaced with a screw jack assembly. Its main components include: steel support plate 6, pressure bearing seat 19, screw 20, top pressure pad 21, reinforcing pad or locally thickened area 22, and wall-side operating end 23.

[0056] The bearing seat 19 is fixedly welded to the steel support plate 6, and together with it, forms a combination with the concrete of the lower wall limb 1 through anchoring components. A threaded hole is machined inside the bearing seat 19 for threaded engagement with the screw 20. The screw 20 is arranged vertically or nearly vertically, with its lower end threadedly connected to the bearing seat 19, and its upper end in contact with a localized area of ​​the bottom surface of the upper wall limb 2 through a top pressure pad 21. To avoid excessive local compressive stress, a reinforcing pad or a locally thickened area 22 can be provided between the top pressure pad 21 and the upper wall limb 2.

[0057] One end of the screw 20 extends through the guide hole 8 to the side of the wall or the floor slab to form the operating end 23. It can be made into the form of a hexagonal head, socket joint, etc., so that it can be tightened or loosened using a torque wrench or power tool.

[0058] 2. Pre-compression application and adjustment

[0059] During the construction phase, after the upper wall segment 2 and the lower wall segment 1 are connected in a box-like manner, the screw 20 is raised relative to the bearing seat 19 by rotating the operating end 23. Its top pressure pad 21 presses upward against the bottom surface of the upper wall segment 2, thereby creating additional vertical normal pressure at the horizontal joint 3. The preload value can be precisely controlled by controlling the tightening torque or rotation angle, combined with the readings of the pressure sensor 10 or displacement gauge 11.

[0060] During use, if it is necessary to increase or restore the preload, simply tighten the screw 20 again via the operating end 23; if it is necessary to appropriately reduce the preload, the screw 20 can be rotated in the opposite direction to release part of the preload force. The advantages of this embodiment are that it is intuitive in construction, allows for continuous adjustment, and can achieve a large preload range.

[0061] To ensure long-term safety, anti-loosening washers, double nuts, or mechanical locking devices can be added between the pressure seat 19 and the screw 20 to prevent the screw 20 from loosening on its own under load cycles or vibration.

[0062] Example 3: Integrated Monitoring and Multi-Point Preloading Arrangement

[0063] In practical engineering applications, in order to improve the safety redundancy of key nodes in high-rise shear walls, the built-in preloading device of this invention can be arranged in a multi-point manner, that is, multiple wedge block components or screw jack components are set at the same node along the wall thickness direction or wall length direction, and coordinated control is achieved through a unified or grouped monitoring and adjustment system.

[0064] like Figure 5As shown, data from multiple pressure sensors 10 and displacement gauges 11 can be connected to the data acquisition unit 26. The warning threshold setting module 27 compares the data with the design limits. When a pre-compression point is found to have significantly lower pressure or excessive slippage on one side, maintenance suggestions or alarm signals are automatically issued to prompt maintenance personnel to adjust the corresponding pre-compression device. The pre-compression adjustment suggestion output or recording module 28 can generate simple operation suggestions based on the monitoring data, such as "adjust the left wedge of node A by 2 scales" or "tighten the jack screw of node B by 1 / 4 turn," to assist on-site operations.

[0065] By using a multi-point preloading and monitoring system, the normal pressure distribution in the node area can be further balanced, avoiding local stress concentration caused by single-point preloading, and improving the redundancy and robustness of the system in the event of local component damage or failure.

[0066] Example 4: Coordination with structural design and code calculations

[0067] In the implementation of this invention, structural designers can utilize the additional normal pressure provided by the built-in preloading device. Explicitly incorporated into the design of horizontal joint shear friction bearing capacity. For example, for applications using the recommended formula in the code: In this case, it can be Decomposed into axial force components generated by the overall structural load Additional normal pressure provided by the pre-compression device ,Right now: ,in: It is calculated based on the axial compression ratio and vertical load combination; The pre-compression device is designed and provided with a certain margin in consideration of expected losses (such as creep, relaxation, temperature, etc.).

[0068] To ensure safety, a reduction factor can be used in the design. right After reduction, the effective additional normal pressure used in actual design is: This ensures the safety and reliability of the shear design of the horizontal joint, taking into account preload attenuation and construction deviations.

[0069] As can be seen from the above embodiments, the present invention, by setting a built-in adjustable preloading device near the horizontal joint of the box-type connection, transforms the traditional "passive normal pressure" that relies on overall axial pressure into "local and controllable mechanical preloading". Without changing the main bending reinforcement system, it effectively improves the friction shear bearing capacity and long-term stability of the horizontal joint of the box-type connection of the precast shear wall, which has significant novelty and creativity and good engineering application prospects.

Claims

1. A box-type horizontal joint node with a built-in self-adjusting preload device, characterized in that, include: A lower wall segment and an upper wall segment form a horizontal joint between them; a concrete box-type connector is provided at the horizontal joint, including a steel rebar connector box embedded in the lower wall segment and / or the upper wall segment and the connecting steel bars therein; a steel support plate is provided in the lower wall segment, located below the box-type connector or near the horizontal joint; an internal preloading device is provided between the steel support plate and the bottom surface of the upper wall segment for applying vertical clamping force to the upper wall segment, the internal preloading device including a wedge block assembly and / or a screw jack assembly; a guide hole or connector box opening leading the preloading operation end to the side of the wall or the floor slab for applying pressure and adjusting the internal preloading device during construction and use; wherein, in the activated state, the internal preloading device generates controllable effective normal pressure at the interface of the horizontal joint to improve the frictional shear bearing capacity of the box-type connection horizontal joint.

2. The node according to claim 1, characterized in that, The wedge block assembly includes: a lower wedge seat fixed to the steel support plate; an upper wedge block that can slide relative to the wall in a vertical or slightly inclined direction, the upper surface of the upper wedge block abutting against the bottom surface of the upper wall limb; a wedge block driving mechanism connected to the upper wedge block through a lateral operating hole in the wall, the wedge block driving mechanism including at least one of a screw, a pull rod, or an eccentric cam; and the adjustment of the normal pressure of the horizontal seam is achieved by driving the upper wedge block to slide relative to the lower wedge seat to change the wedge stack height.

3. The node according to claim 1, characterized in that, The screw jack assembly includes: a bearing seat fixed to the steel support plate; a screw threaded into the bearing seat and vertically extendable, with a top pressure pad at the upper end of the screw abutting against the bottom surface of the upper wall limb; and a force-applying end disposed on the side of the wall or floor and drivenly connected to the screw, wherein the force-applying end applies pre-tightening force through a hexagonal nut, sleeve, or special wrench; the screw jack assembly can be tightened again during the node use stage to restore or increase the normal pressure of the horizontal joint.

4. The node according to any one of claims 1 to 3, characterized in that, The steel support plate is reliably anchored to the concrete of the lower wall limb by shear nails, studs or rebar, and is basically continuous along the thickness direction of the wall limb, so as to uniformly transfer the reaction force generated by the built-in preloading device to the lower wall limb.

5. The node according to any one of claims 1 to 4, characterized in that, A pressure sensor and / or displacement gauge are installed at the horizontal joint or near the built-in pre-compression device. The pressure sensor is used to monitor the normal pressure applied by the built-in pre-compression device, and the displacement gauge is used to monitor the opening, slippage, or compression deformation of the horizontal joint.

6. The node according to any one of claims 1 to 5, characterized in that, The vertical and shear bars inside the box-type connector independently bear the vertical force and shear resistance. The built-in preloading device does not serve as a bending longitudinal reinforcement, but only provides additional normal pressure to improve the interfacial friction shear bearing capacity.

7. The node according to any one of claims 1 to 6, characterized in that, A waterproof sleeve and sealing structure are provided around the guide hole or the opening of the connecting box to prevent water seepage and corrosion of steel components along the pre-compression operation end channel.

8. A method for construction and use of the node according to any one of claims 1 to 7, characterized in that, include: 1) Embed steel support plates, box-type connectors, and guide holes during the prefabrication or cast-in-place stage of the lower wall limb; 2) Hoist the upper wall limb and connect it with the box-type connector to achieve rebar butt joint or grout injection connection to form a horizontal joint; 3) Drive the wedge block assembly and / or screw jack assembly through the operating end on the side of the wall or the floor slab to apply preload to the upper wall limb so that the horizontal joint generates the normal pressure required by the design; 4) Check or fine-tune the preload value through pressure sensors or displacement monitoring methods. 5) During the structural use phase, the monitoring data is read periodically or as needed. When the width of the horizontal seam increases or the slippage exceeds the set threshold, the built-in pre-compression device is driven again through the operating terminal to increase the normal pressure and restore or enhance the shear resistance of the horizontal seam.

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