Superimposed belleville spring energy storage self-resetting low-loss prestressed BFRP tie piece

Abstract

The invention provides a superposed belleville spring energy storage self-resetting low-loss prestressed BFRP tie piece which is suitable for a precast concrete sandwich wallboard connecting system in scenes with severe temperature difference, high corrosion and dynamic load composite action. The invention aims to solve the core problems of thermal stress mismatch, interface stripping, insufficient durability and the like of the traditional BFRP tie piece in the complex environments, and avoid the situation that the normal use and safety performance of a building are seriously influenced due to the damage of a precast concrete sandwich panel structure. Through material gradient design and an intelligent response mechanism, the static performance limitation of a traditional anchoring part is broken through, a high-reliability and long-service-life connection solution is provided for a fabricated building in a specific environment, remarkable technical advancement and industrialization value are achieved, and wide application prospects are achieved. And a more effective basis is provided for popularization and application of the precast concrete sandwich panel.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building engineering, in particular to a superimposed butterfly-shaped spring energy storage self-resetting low-loss prestressed BFRP tie member. BACKGROUND

[0002] In the field of prefabricated structure engineering, the prefabricated concrete sandwich wallboard is the core enclosure structure of the building, and the performance of its tie system directly determines the seismic safety and durability of the wallboard. The traditional prestressed system generally uses steel strand or ordinary FRP tendon as the force transmission medium. Influenced by concrete shrinkage and creep, anchor slip and stress relaxation, the prestress loss of the steel strand system during the service period is as high as 18%~25%, which leads to continuous degradation of the wall body's crack resistance and stiffness. Meanwhile, after the wallboard undergoes plastic deformation under strong earthquake action, the steel strand system produces irreversible residual deformation of >0.5% due to yielding, which requires manual resetting or replacement of the component, seriously affecting the post-disaster operation of emergency buildings. In addition, in an acid and alkali corrosion environment, the corrosion environment adaptability is insufficient, and the corrosion and expansion of steel strand due to chloride ion erosion result in a prestress loss of more than 30% within 5 years. Although ordinary FRP tendon has corrosion resistance, it still faces the risks of ultraviolet aging and creep fracture, and faces many severe challenges. These problems seriously affect the normal use and safety performance of the building, therefore, it is particularly important to design a tie system that integrates low prestress loss, intelligent self-resetting and environmental durability.

[0003] The present application describes a superimposed butterfly-shaped spring energy storage self-resetting low-loss prestressed BFRP tie member, which is achieved by the following technical solutions: an invention method is proposed, which is suitable for buildings in high-intensity seismic areas, corrosive environments and prefabricated rapid construction. This structure is designed to improve the seismic toughness and durability of prefabricated concrete sandwich wallboards, and solves the problems of stress relaxation, insufficient resetting capacity and corrosion sensitivity in traditional prestressed systems. Through the method described in the present application, the performance limitations of the inherent defects of traditional basalt fiber tendon (BFRP) are broken through, and a tie system that integrates "low prestress loss", "intelligent self-resetting" and "environmental durability" is developed, breaking the functional boundaries of materials and structures, meeting the severe demands of high-intensity areas, corrosive environments and rapid repair scenarios, solving the core defects of existing technologies and the application contradictions of BFRP, and providing strong support for the innovation of subsequent invention schemes. SUMMARY

[0004] The present application aims to provide a superimposed butterfly-shaped spring energy storage self-resetting low-loss prestressed BFRP tie member to solve the above technical problems.

[0005] The object of the present application can be achieved by the following technical solutions: A composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie member includes a rib. Spring limiting seats are symmetrically arranged at both ends of the rib near the anchoring end. A composite butterfly spring assembly is arranged on one side of each spring limiting seat. The composite butterfly spring assembly is composed of three overlapping springs and two opposing springs arranged alternately. An SMA spring sheet is arranged on one side of the composite butterfly spring assembly, and an intelligent locking device is arranged on one side of the SMA spring sheet.

[0006] As a further aspect of the present invention: the stacked spring is a stacked disc spring with a stiffness of 15kN / mm; the opposing spring is an opposing disc spring with a stiffness of 5kN / mm; both are made of 60Si2Mn material and have been galvanized for corrosion protection.

[0007] As a further aspect of the present invention: the opposing springs are arranged in a "reverse opposing" configuration, with a single piece thickness of 3mm, an outer diameter of 30mm, and an inner diameter of 15mm; the stacked springs are arranged in a "co-directional stacked" configuration, with a single piece thickness of 4mm, an outer diameter of 30mm, and an inner diameter of 12mm; both are limited by an annular step within the spring limiting seat to form an energy storage unit with a total length of 45mm.

[0008] As a further aspect of the present invention: the reinforcing rib is made of 80% basalt fiber and 20% carbon fiber using a bidirectional weaving process; the fiber volume fraction is controlled at 65%-70%, and the resin matrix is ​​modified epoxy resin with 10wt% nano-SiO2 particles added.

[0009] As a further aspect of the present invention: the surface of the rib undergoes a two-step interface strengthening treatment involving sandblasting roughening and coating with a silane coupling agent: the sandblasting roughening uses 80-mesh white corundum sand to form a micron-level uneven structure on the surface of the rib, increasing the frictional contact area with the anchor clamp; the silane coupling agent is KH560, which is diluted with ethanol solution and uniformly coated on the surface of the rib, and then dried at 80°C for 1 hour, so that the coupling agent molecules form chemical bonds with the hydroxyl groups on the fiber surface and the resin matrix, increasing the interfacial bonding strength to ≥25MPa, and preventing the rib from peeling off from the resin matrix during stress.

[0010] As a further aspect of the present invention: the spring limiting seat is made of Q235 steel and has been treated with powder coating for corrosion protection with a thickness of 60μm; it is connected to the elastic transition sleeve of the rib through an internal thread.

[0011] As a further embodiment of the present invention: the elastic transition sleeve is located between the composite butterfly spring assembly and the rib, with a thickness of 3-5mm and a length of 30mm. The inner wall is interference-fitted with the rib, and the outer wall is fixed to the spring limiting seat by threads.

[0012] As a further embodiment of the present invention, the following steps are performed to assemble the device: Step 1: Embed the EPDM rubber waterstop ring into the sealing groove outside the reserved hole of the outer leaf wall panel, and control the compression rate of the waterstop ring at 30%; Place the anchor seat of the elastic wedge anchor into the reserved hole, ensuring that the outer surface of the anchor seat is flush with the surface of the wall panel and the deviation is ≤0.5mm, and use temporary support for fixation to prevent the anchor seat from shifting; Open the two-piece clamp of the anchor seat, insert the outer leaf anchoring section of the rib with a length of 100-150mm into the clamp, and calibrate it with a laser alignment instrument to ensure that the axis of the rib and the axis of the anchor seat are coaxial with a deviation of ≤1mm; Close the clamp and tighten the locking nut on the outside of the anchor seat with a torque wrench to make the clamp and the rib fit tightly together; Step 2: Insert the reinforcing rib from the outer leaf wall panel into the insulation layer. The rib should be pushed slowly through the insulation layer to avoid scratching the rib surface or damaging the insulation layer. If resistance is encountered, use a guide sleeve to assist insertion; forceful impact is prohibited. Stop insertion when the installation scale of the overlapping butterfly spring assembly of the rib reaches the position of the reserved hole in the inner leaf wall panel. Fit the prefabricated overlapping butterfly spring assembly into the rib, ensuring the spring limit seat is tightly against the outside of the reserved hole in the inner leaf wall panel. Ensure the coaxial deviation between the overlapping butterfly spring assembly and the rib is ≤0.5mm using the positioning scale. Secure the spring limit seat to the temporary support of the inner leaf wall panel with bolts to prevent displacement of the overlapping butterfly spring assembly. Step 3: In the section of the rib close to the outer leaf wall panel, 50mm from the outer leaf anchor, insert a stainless steel corrugated pipe. The alignment deviation between one end of the corrugated pipe and the outlet end of the outer leaf anchor should be ≤1mm. The other end is fixed to the rib with a stainless steel clamp. At the contact point between the corrugated pipe and the anchor and clamp, attach a water-swellable waterstop strip. The overlap length of the waterstop strip should be ≥10mm to ensure a leak-free seal.

[0013] As a further aspect of the present invention: the length of the BFRP tie member is 300-800mm, of which the length of the energy storage section accounts for 30%-40% and the length of the anchoring section accounts for 60%-70%.

[0014] As a further aspect of the present invention: when the wall panel is subjected to a horizontal seismic load and a relative displacement occurs, when the displacement is ≤5mm, the BFRP reinforcement is pulled to compress and store energy in the composite butterfly spring group, and the spring first undergoes elastic deformation to dissipate energy, thus avoiding the BFRP reinforcement from directly bearing the impact load. When the wall panel is subjected to a horizontal seismic load and undergoes a large displacement, when the displacement is between 5-15mm, the superimposed springs participate in the deformation and provide the restoring force through the accumulation of elastic potential energy.

[0015] The beneficial effects of this invention are: This invention fundamentally solves the core technical pain points of traditional basalt fiber reinforced plastic (BFRP) tie rods, namely "severe prestress attenuation, lack of self-resetting ability, and insufficient anchoring reliability," through the synergistic design of "overlapping butterfly spring graded energy storage + low-loss prestressing system + elastic wedge anchoring." It achieves a comprehensive leap in mechanical performance and provides key protection for the structural safety of precast concrete sandwich wall panels.

[0016] In terms of seismic performance, the graded energy storage mechanism of the composite butterfly spring assembly breaks the limitation of traditional components where "energy dissipation and reset are mutually exclusive." Under small load conditions, the composite spring dissipates 40% of the input energy through friction, preventing the BFRP reinforcement from bearing instantaneous impact loads and reducing the maximum stress of the reinforcement from 180MPa to 117MPa, effectively avoiding the risk of brittle fracture. Under large load conditions, the composite spring rapidly accumulates an elastic potential energy density of 120kJ / m². 3 After unloading, the drive wall panel is precisely reset, and the residual deformation is strictly controlled to ≤3mm. The self-resetting capability index (BSI) reaches 0.95, which is much higher than the 0.4-0.6 of traditional BFRP bars.

[0017] This invention exhibits excellent corrosion resistance and weather resistance through material selection and structural sealing design. The BFRP reinforcement adopts a mixed ratio of "80% basalt fiber + 20% carbon fiber", with a salt spray resistance life of ≥5000h. The epoxy resin coating, EPDM rubber sealing ring and ultrafine cement grouting of the elastic wedge anchor form a "three-layer anti-corrosion barrier". After being immersed in 3.5% sodium chloride solution for 1000 days, the anchoring efficiency only decreased by 3% (from 95% to 92%), while the efficiency of traditional non-corrosion anchors decreased by more than 25%.

[0018] Whether subjected to dynamic loads in high-intensity earthquake zones, severe corrosion in marine environments, or temperature-induced deformation in frigid regions, this invention maintains stable mechanical properties, filling the technological gap for high-toughness BFRP tie members in complex environments. The core advantage of this innovative design lies in combining efficient construction with exceptional performance, helping to achieve a win-win situation for both carbon reduction and ecological protection, while simultaneously meeting the high-speed and high-standard requirements of engineering construction. By using this new tie member, the performance of precast concrete sandwich panels in extreme environments has been significantly improved. Attached Figure Description

[0019] The invention will now be further described with reference to the accompanying drawings.

[0020] Fig. 1 This is a schematic diagram of the overall structure of the present invention; Fig. 2 This is a schematic diagram of the installation structure of the present invention.

[0021] In the diagram: 1. Intelligent locking device; 2. Stacked spring; 3. Matching spring; 4. Rib; 5. SMA spring; 6. Spring limit seat; 7. Outer leaf wall panel; 8. Insulation layer; 9. Inner leaf wall panel; 10. Wall panel reserved hole; 11. Elastic transition sleeve. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1 Please see Figs. 1-2 As shown, the present invention is a composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie member, which is described in detail below: 1) Based on the characteristics of precast concrete sandwich panels, a composite disc spring energy storage self-resetting low-loss prestressed BFRP tie member described in this invention is adopted. Its structure consists of four parts: composite disc spring energy storage unit, rib 4 (BFRP main rib), intelligent locking device 1, and self-resetting trigger mechanism integrated bistable SMA spring 5. By replacing the elastic deformation of the material with mechanical energy storage, the rectangular stiffness characteristics of the disc spring compensate for the low modulus defect of BFRP, so as to achieve efficient prestress maintenance, millisecond-level self-resetting and full-life self-diagnosis.

[0024] 2) First, multi-layered, 3mm thick disc springs made of 60Si2MnA spring steel are pre-compressed to the design stroke. After 30% deformation, they provide about 200kN of prestress. The flat zone of its rectangular stiffness curve accounts for more than 80%, which can compensate for the deformation caused by concrete shrinkage and creep, so that the long-term prestress loss rate is less than 5%. 3) Secondly, a spiral groove with a depth of 0.8 mm is machined on the surface of the BFRP main rib and coated with a carbon nanotube (CNT) conductive layer. While maintaining a tensile strength of 1200 MPa, damage is monitored in real time by the resistance change rate (ΔR / R0 > 5%). 4) The intelligent locking device is again equipped with a Titan SMA wedge lock with a phase change temperature of 25°C. Under normal temperature, it expands and locks the disc spring in the pre-compression state, and the anchoring slippage is <0.1mm. 5) Finally, the self-resetting trigger mechanism integrates a bistable SMA spring (martensitic / austenitic dual phase) and a magnetorheological fluid (MRF) damper. During an earthquake, the MRF dissipates 60% of the energy through shear flow. Within 0.5 seconds after the earthquake, the SMA spring triggers the disc spring to release energy and drive the wall panel to reset until the residual deformation is <0.1%.

[0025] Specifically, the aforementioned composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie member has composite-opposite butterfly spring groups symmetrically arranged at both ends of the BFRP reinforcement near the anchorage end. Each group consists of three 15kN / mm stiffness composite disc springs and two 5kN / mm stiffness opposing disc springs arranged alternately. The springs are made of 60Si2Mn material and the surface is galvanized for corrosion protection.

[0026] In this spring array structure, the composite disc springs are responsible for the main energy storage, while the stacked disc springs are responsible for secondary energy dissipation. When subjected to external forces, this structure dissipates approximately 40% of the energy through interfacial friction, preventing the BFRP reinforcement from directly bearing the impact load, and reducing the peak impact stress by 35% compared to a single structure.

[0027] In this embodiment, when the wall panel is subjected to a horizontal seismic load and a relative displacement occurs, when the displacement is ≤5mm, the BFRP reinforcement is pulled and the spring is compressed to store energy. The spring first undergoes elastic deformation to dissipate energy, thus avoiding the BFRP reinforcement from directly bearing the impact load. When the wall panel is subjected to a large displacement due to a horizontal seismic load, the superimposed spring participates in the deformation when the large displacement is 5-15mm, and provides the restoring force through the accumulation of elastic potential energy.

[0028] In this embodiment, after unloading, the spring releases energy, causing the BFRP reinforcement to reset synchronously with the wall panel, resulting in a final residual deformation of ≤3mm.

[0029] In this embodiment, graded energy dissipation makes the load transfer smoother, and the width of wall panel cracks can be controlled within 0.1mm, which is more than 60% lower than the 0.3-0.5mm crack width of ordinary tie parts, thus avoiding the failure of the insulation layer due to crack expansion.

[0030] In this embodiment, a hybrid weaving process of 80% basalt fiber and 20% carbon fiber is adopted. The stress relaxation rate of BFRP bar after 1000 days is only 3% (12% for pure BFRP bar). It is estimated that the relaxation loss per million hours is ≤8%, ensuring that the prestress retention rate of the structure is ≥90% during its 50-year service life.

[0031] In this embodiment, the salt spray resistance life of the BFRP bar is ≥5000h, and the anchor seat adopts double protection of epoxy resin anti-corrosion layer + EPDM rubber sealing ring. After being immersed in 3.5% sodium chloride solution for 1000 days, the anchoring efficiency only decreases by 3%, which is far superior to stainless steel tie parts.

[0032] In this embodiment, a 3-5mm thick polyurethane elastic transition sleeve with an elastic modulus of 1.5GPa is provided between the spring and the BFRP rib. The inner wall of the sleeve is interference-fitted with the BFRP rib, and the outer wall is connected to the spring limit seat by threads.

[0033] In this embodiment, the polyurethane elastic transition sleeve structure can avoid local stress concentration of the BFRP rib by the spring, and prevent the rib from breaking due to instantaneous impact.

[0034] A composite butterfly-shaped spring energy storage self-resetting low-loss prestressed BFRP tie member is disclosed. The graded energy storage structure can absorb 60% of the energy of the explosion shock wave and does not suffer penetrating damage under the action of 1.2MPa explosion pressure. The explosion resistance limit is 3 times higher than that of solid BFRP tie members.

[0035] This composite butterfly spring energy storage low-loss prestressed self-resetting basalt fiber reinforced structure possesses excellent resistance to salt spray corrosion and freeze-thaw cycles. It meets high-intensity seismic standards while enhancing blast resistance, enabling it to better adapt to extreme environments. Suitable for prefabricated buildings in complex environments such as deserts, oceans, and high-intensity earthquake zones, its low-loss prestressing, corrosion-resistant design, and self-healing potential ensure a service life of ≥80 years for the tie-in components, doubling the lifespan of ordinary BFRP tie-in components (40 years) and reducing the total life-cycle cost by 40%. This significantly improves the service life and safety of sandwich wall panels, making it an advanced solution in the application of precast concrete sandwich panels.

[0036] Example 2 A composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie rod is described in detail below: 1) Composite butterfly spring energy storage low loss prestressed self-resetting basalt fiber reinforcement is a new type of structural component for precast concrete sandwich wall panels under high intensity earthquakes, long-term service and extreme environments.

[0037] 2) The core load-bearing component is a basalt-carbon fiber hybrid reinforcement. The reinforcement adopts a bidirectional weaving process with 80% basalt fiber and 20% carbon fiber. The fiber volume fraction is strictly controlled at 65%-70%. The resin matrix is ​​a modified epoxy resin with 10wt% nano-SiO2 particles added.

[0038] 3) Two-step interface strengthening treatment of the rib surface: sandblasting roughening and silane coupling agent coating: sandblasting roughening uses 80-mesh white corundum sand to form a micron-level uneven structure on the rib surface, increasing the frictional contact area with the anchor clamp; the silane coupling agent is KH560, which is diluted with ethanol solution and uniformly coated on the rib surface. After drying at 80℃ for 1 hour, the coupling agent molecules form chemical bonds with the hydroxyl groups on the fiber surface and the resin matrix, and the interfacial bonding strength is increased to ≥25MPa, preventing the rib and the resin matrix from peeling off during the stress process.

[0039] 4) The stacked butterfly spring assembly is the core of realizing the "energy storage-reset" function. Its structural design adopts a composite array form of "paired springs + stacked springs". It balances the needs of "small load energy consumption" and "large load reset" through a graded response mechanism. The middle energy storage section of the stacked butterfly spring assembly consists of spring limit seat, paired butterfly springs, stacked butterfly springs, elastic transition sleeve and spring limit seat.

[0040] 5) Both the mating and stacked disc springs are made of 60Si2Mn spring steel (tensile strength ≥1800MPa, elastic limit ≥1500MPa), with an 80μm thick galvanized surface treatment and a salt spray resistance life ≥5000h. The mating springs consist of two pieces arranged in a "reverse mating" configuration, with a stiffness of 5kN / mm, a single piece thickness of 3mm, an outer diameter of 30mm, and an inner diameter of 15mm. The stacked springs consist of three pieces arranged in a "co-directional stacking" configuration, with a stiffness of 15kN / mm, a single piece thickness of 4mm, an outer diameter of 30mm (the same as the mating springs), and an inner diameter of 12mm. The two sets of springs are limited by an annular step within the spring limiting seat, forming an energy storage unit with a total length of 45mm.

[0041] 6) The spring limit seat is made of Q235 steel with a 60μm thick powder-coated anti-corrosion coating. It consists of two symmetrical parts, left and right, which are connected to the elastic transition sleeve of the BFRP rib via internal threads. The elastic transition sleeve is located between the spring and the BFRP rib. It is made of polyurethane material with a Shore hardness of 70D and an elastic modulus of 1.5Gpa, with a thickness of 3-5mm and a length of 30mm. The inner wall is interference-fitted with the BFRP rib, and the outer wall is fixed to the spring limit seat via threads. Its function is to avoid local stress concentration of the BFRP rib by the spring, reducing the stress concentration factor from 1.8 to 1.2.

[0042] 7) Structurally, the elastic transition sleeve is located in the inner leaf wall panel anchorage section of the tension end of the BFRP reinforcement. It is made of high-strength cast iron T200 with a compressive strength ≥200MPa and has a conical structure (length 50mm, large end diameter 40mm, small end diameter 30mm). A through hole with a diameter of 18mm is reserved inside the sleeve (to fit φ16mm BFRP reinforcement). An annular grouting groove (width 5mm, depth 2mm) is opened on the inner wall of the through hole to fill sulfoaluminate expansive cement (expansion rate 0.05%-0.1%, compressive strength ≥42.5MPa).

[0043] Example 3 A composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie rod, the specific operation is as follows: 1) In response to the practical application needs of precast concrete sandwich panels, this invention proposes a composite disc spring energy storage self-resetting low-loss prestressed BFRP tie member. This solution integrates the composite disc spring energy storage unit and the prestressed self-resetting mechanism. Through the mixing of 80% Wuyan fiber and 20% carbon fiber, it exhibits excellent corrosion resistance and weather resistance, effectively improving the overall pull-out resistance of the precast concrete sandwich panel and solving the problem of insufficient performance of traditional tie members in complex environments. The core components are assembled on-site in the order of anchoring section → reinforcement insertion → spring assembly → deformation compensation to ensure that all components work together.

[0044] 2) The preliminary design of the composite butterfly spring energy storage low-loss prestressed self-resetting basalt fiber reinforcement structure involves embedding a EPDM rubber waterstop ring into the sealing groove outside the pre-reserved hole in the outer leaf wall panel, with the waterstop ring compression rate controlled at 30%. The anchor seat (with multi-toothed clamps) of the elastic wedge anchor is placed into the pre-reserved hole, ensuring the outer surface of the anchor seat is flush with the wall panel surface with a deviation ≤0.5mm. Temporary supports are used for fixation to prevent anchor seat displacement. The two-piece clamps of the anchor seat are opened, and the outer leaf anchoring section of the BFRP reinforcement, 100-150mm in length, is inserted into the clamps. A laser alignment instrument is used to ensure the reinforcement axis and anchor seat axis are coaxial with a deviation ≤1mm. The clamps are closed, and the locking nut on the outside of the anchor seat is tightened using a torque wrench (torque 15-20 N·m) to ensure a tight fit between the clamps and the reinforcement.

[0045] 3) Next, insert the rib 4 (BFRP rib) from the outer leaf wall panel 7 into the insulation layer 8. When the rib passes through the insulation layer 8, it should be pushed in slowly (speed ≤50mm / s) to avoid scratching the surface of the rib or damaging the insulation layer. If resistance is encountered, use a special guide sleeve (taper 1:20) to assist in the insertion. Forced impact is prohibited. When the spring assembly installation scale of the rib 4 reaches the position of the wall panel reserved hole 10 of the inner leaf wall panel 9, stop the insertion. Put the prefabricated stacked butterfly spring assembly (including elastic transition sleeve 11, mating spring 3, stacked spring 2, and spring limit seat 6) into the rib. The spring limit seat 6 should be close to the outside of the wall panel reserved hole 10 of the inner leaf wall panel 9. Ensure that the coaxial deviation between the spring assembly and the rib 4 is ≤0.5mm by using the positioning scale. Use bolts to fix the spring limit seat to the temporary support of the inner leaf wall panel (bolt torque 10-15N.m) to prevent the spring assembly from shifting.

[0046] 4) Next, in the section of the BFRP reinforcement near the outer leaf wall panel 7, 50mm from the outer leaf anchor, insert a stainless steel corrugated pipe (50-80mm in length, ±10mm in expansion). The alignment deviation between one end of the corrugated pipe and the outlet end of the outer leaf anchor should be ≤1mm, and the other end should be fixed to the reinforcement with a stainless steel clamp. At the contact point between the corrugated pipe and the anchor and clamp, attach a water-swellable waterstop strip with an overlap length ≥10mm to ensure a leak-free seal.

[0047] 5) The new structural components adopt a "three-section coaxial integrated frame". From left to right, they are the outer leaf wall panel anchoring section, the intermediate energy storage-monitoring section, and the inner leaf wall panel anchoring section. Each section works together through modular design. The outer leaf wall panel anchoring section and the inner leaf wall panel anchoring section are symmetrical in structure and both include elastic wedge anchors, axial deformation compensation bellows and anti-corrosion sealing components. They are mainly responsible for the stable transfer of prestress to the wall panel and adapting to the long-term axial deformation of the wall panel caused by creep and shrinkage. The intermediate energy storage-monitoring section is the core functional area, which integrates the stacked butterfly spring energy storage component, low-loss elastic transition sleeve and intelligent monitoring module. It achieves self-resetting after earthquake through spring graded energy storage, controls the loss rate through prestress compensation structure, and captures changes in structural performance in real time with the help of sensors.

[0048] 6) The final overall structural length is designed to be 300-800mm based on the thickness of the sandwich wall panels, with the energy storage section accounting for 30%-40% and the anchoring section accounting for 60%-70%, ensuring balanced stress distribution across all functional sections and eliminating the risk of localized stress concentration. Functionally, this structure overcomes the limitations of traditional tie-in components' "single load-bearing" capabilities, achieving a triple functional integration of "prestressed stable load-bearing + composite spring energy storage and reset + real-time monitoring and maintenance." During normal use, the low-loss prestressing system ensures the reinforcement maintains stable pretension, limiting wall panel cracking. Under dynamic loads such as earthquakes and strong winds, the composite butterfly springs dissipate energy through graded energy storage, preventing brittle fracture of the reinforcement. After load unloading, the springs release elastic potential energy to drive the wall panel reset, with residual deformation controlled to ≤3mm. Throughout its lifespan, the intelligent monitoring module provides real-time feedback on prestress loss and deformation data, offering precise data for maintenance and making it suitable for complex scenarios such as high-intensity earthquake zones, marine environments, and ultra-low-energy buildings.

[0049] The second aspect of the present invention provides a composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie member, which has the following effects: 1) A new type of structural component designed for the integrated "load-bearing-reset-energy dissipation-corrosion protection" requirements of precast concrete sandwich wall panels under high-intensity earthquakes, long-term service and extreme environments. The whole adopts a "three-section coaxial integrated frame", which consists of an outer leaf wall panel anchorage section, a middle energy storage-monitoring section and an inner leaf wall panel anchorage section from left to right. Each section works together through modular design, which completely solves the four major technical pain points of traditional BFRP bars: "severe prestress attenuation, insufficient self-reset ability, easy anchorage damage and lack of operation and maintenance monitoring".

[0050] 2) The outer leaf wall panel anchorage section and the inner leaf wall panel anchorage section have a symmetrical structure. Both include elastic wedge anchors, axial deformation compensation bellows and anti-corrosion sealing components. They are mainly responsible for the stable transfer of prestress to the wall panel and adapting to the long-term axial deformation of the wall panel caused by creep and shrinkage. The intermediate energy storage-monitoring section is the core functional area, which integrates a stacked butterfly spring energy storage component, a low-loss elastic transition sleeve and an intelligent monitoring module. It achieves self-resetting after an earthquake through spring-graded energy storage, controls the loss rate through the prestress compensation structure, and captures changes in structural performance in real time with the help of sensors.

[0051] 3) The core load-bearing component of the self-resetting BFRP reinforcement is a "basalt-carbon fiber hybrid reinforcement". The reinforcement adopts a bidirectional weaving process of "80% basalt fiber + 20% carbon fiber". The basalt fiber (diameter 13-17μm, tensile strength ≥3000MPa) has excellent corrosion resistance and cost advantages, and can adapt to highly corrosive environments such as marine and chemical industries. The carbon fiber (diameter 7-10μm, tensile strength ≥3500MPa, elastic modulus ≥230GPa) can significantly improve the relaxation resistance of the reinforcement, solving the problem of prestress attenuation caused by relaxation in traditional BFRP reinforcement. Through bidirectional weaving (the weaving angles in both the warp and weft directions are 45°), the fibers form a spatial interwoven network in the reinforcement, avoiding the problem of weak transverse shear strength caused by unidirectional weaving, and increasing the transverse shear strength of the reinforcement to ≥40MPa, which is more than 50% higher than that of traditional unidirectional pultruded BFRP reinforcement.

[0052] 4) The surface of the rib undergoes a two-step interface strengthening treatment: "sandblasting roughening - silane coupling agent coating". Sandblasting roughening uses 80-mesh white corundum sand to form a micron-level uneven structure on the surface of the rib (roughness Ra=3-5μm), increasing the frictional contact area with the anchor clamp. KH560 silane coupling agent is selected and diluted with ethanol solution (mass fraction 5%) and uniformly coated on the surface of the rib. After drying at 80℃ for 1h, the coupling agent molecules form chemical bonds with the hydroxyl groups on the fiber surface and the resin matrix, and the interfacial bonding strength is increased to ≥25MPa, preventing the rib from peeling off from the resin matrix during the stress process.

[0053] 5) The addition of carbon fiber reduces the relaxation rate of basalt fiber through the "stress sharing effect": Under prestress, carbon fiber bears more stress (about 60% of the total stress) due to its high elastic modulus, while basalt fiber bears the remaining 40% of the stress. Moreover, the stress relaxation rate of carbon fiber after 1000 days is only 1.5% (far lower than the 12% of basalt fiber), which reduces the stress relaxation rate of the hybrid reinforcement to below 3% after 1000 days and the relaxation loss per million hours is ≤8%, laying the material foundation for the realization of low-loss prestressed systems. Nano-SiO2 modified epoxy resin improves the toughness of the resin matrix through the "particle reinforcement effect", increasing the elongation at break of the matrix from 3% to 5%, avoiding the overall failure of the reinforcement due to brittle fracture of the matrix.

[0054] The second aspect of this invention provides a staged energy storage and dissipation technology for composite butterfly springs in a low-loss prestressed BFRP tie-in component. Under dynamic loads such as earthquakes and strong winds, the composite butterfly spring dissipates energy through staged energy storage, preventing brittle fracture of the reinforcement. After the load is unloaded, the spring releases elastic potential energy to drive the wall panel to reset, with residual deformation controlled to ≤3mm. This invention comprehensively surpasses traditional technologies in terms of pull-out resistance, construction efficiency, economy, and durability, becoming the preferred solution for precast concrete sandwich panel applications. Its core advantage lies in combining structural innovation with material optimization, achieving a balance between efficient construction and long-term performance.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The composite butterfly spring assembly of the present invention is the core of the self-resetting BFRP rib to realize the "energy storage-reset" function. Its structural design adopts a composite array form of "paired springs + composite springs". It balances the needs of "small load energy consumption" and "large load reset" through a graded response mechanism, which is different from the defects of traditional single spring structure that "either insufficient energy consumption or reset failure".

[0056] (2) At the level of graded energy storage principle, this invention achieves performance adaptation under different working conditions through "load threshold triggering": Under small load conditions (such as temperature stress, slight vibration, wall panel displacement ≤5mm), due to the low stiffness of the springs (5kN / mm), elastic deformation occurs preferentially, and the friction between the spring plates can dissipate about 40% of the input energy. Specifically, the reverse arrangement of the springs causes the adjacent spring plates to slide relative to each other during the deformation process. The product of the sliding friction (about 800N) and the displacement is the dissipated energy. This process can effectively prevent the BFRP reinforcement from directly bearing the impact load, reduce the maximum stress of the reinforcement from 180MPa to 117MPa, and prevent the reinforcement from breaking due to instantaneous impact.

[0057] (3) Under heavy load conditions (such as earthquakes, strong winds, and wall panel displacement of 5-15mm), when the load exceeds the bearing limit of the coupled springs (approximately 25kN), the superimposed springs (stiffness 15kN / mm) activate to store energy. Their unidirectional superimposed structure can rapidly accumulate elastic potential energy (elastic potential energy density reaches 120kJ / m). 3 At this point, the BFRP reinforcement and the spring work together to bear the load, ensuring that the structure does not undergo plastic failure. When the load is unloaded, the stacked spring releases the stored elastic potential energy and pushes the BFRP reinforcement to reset through the spring limit seat. At the same time, the residual elastic force of the spring assists in correcting the small displacement, ultimately making the residual deformation of the wall panel ≤3mm and the self-resetting capability index (BSI) reach 0.95 (the BSI of traditional BFRP reinforcement is only 0.4-0.6).

[0058] (4) The limiting boss (height 2mm) on the inner side of the spring limiting seat of the present invention can limit the maximum compression of the spring (≤15mm), avoid the spring from plastic deformation due to overload, and ensure its performance stability under multiple cyclic loads. After 30 earthquake simulation cyclic loading tests (peak acceleration 0.4g), the stiffness attenuation rate of the spring is ≤5%, and the reset accuracy does not decrease significantly, which meets the requirement of "reusable" building structure.

[0059] In summary, this composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie member, through the synergistic design of "composite butterfly spring graded energy storage + low-loss prestressing system + elastic wedge anchoring," fundamentally solves the core technical pain points of traditional basalt fiber reinforced polymer (BFRP) tie members, namely "severe prestress attenuation, lack of self-resetting ability, and insufficient anchoring reliability." It achieves a comprehensive leap in mechanical performance, providing crucial protection for the structural safety of precast concrete sandwich wall panels. Regarding seismic performance, the graded energy storage mechanism of the composite butterfly spring assembly breaks the limitation of traditional components where "energy dissipation and resetting cannot be simultaneously achieved"—under small load conditions, the composite spring dissipates 40% of the input energy through friction, preventing the BFRP reinforcement from bearing instantaneous impact loads, reducing the maximum stress of the reinforcement from 180MPa to 117MPa, effectively avoiding the risk of brittle fracture; under large load conditions, the composite spring rapidly accumulates elastic potential energy (density reaching 120kJ / m³). 3 After unloading, the drive wall panel is precisely reset, and the residual deformation is strictly controlled to ≤3mm. The self-resetting capability index (BSI) reaches 0.95, which is much higher than the 0.4-0.6 of traditional BFRP bars.

[0060] In terms of adaptability to extreme environments, this invention exhibits excellent corrosion resistance and weather resistance through material selection and structural sealing design. The BFRP reinforcement uses a hybrid ratio of 80% basalt fiber and 20% carbon fiber, achieving a salt spray resistance life of ≥5000 hours. The epoxy resin coating, EPDM rubber sealing ring, and ultrafine cement grouting of the elastic wedge anchors form a "three-layer anti-corrosion barrier." After immersion in a 3.5% sodium chloride solution for 1000 days, the anchoring efficiency only decreased by 3% (from 95% to 92%), while the efficiency of traditional un-corrosion-resistant anchors decreased by more than 25%. Simultaneously, the heat insulation design of the unbonded sleeve and corrugated pipe expansion section reduces the thermal conductivity of the reinforcement to 0.02 W / (mK), which, combined with the wall panel insulation layer, can reduce the building's heat transfer coefficient by 0.04 W / (mK). 2 The material (.K) meets the requirements of the "Technical Standard for Near-Zero Energy Buildings". Whether under dynamic loads in high-intensity earthquake zones, strong corrosion in marine environments, or temperature-induced deformation in frigid regions, this invention maintains stable mechanical properties, filling the technological gap for high-toughness BFRP tie rods in complex environments. No quality issues were found during subsequent inspections, demonstrating excellent application results.

[0061] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie rod, characterized in that, The rib (4) is provided with spring limit seats (6) symmetrically arranged at both ends of the rib (4) near the anchoring end. A composite butterfly spring group is provided on one side of the spring limit seat (6). The composite butterfly spring group is composed of 3 overlapping springs (2) and 2 opposing springs (3) arranged alternately. An SMA spring (5) is provided on one side of the composite butterfly spring group. An intelligent locking device (1) is provided on one side of the SMA spring (5).

2. The composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie member according to claim 1, characterized in that, The stacked spring (2) is a stacked disc spring with a stiffness of 15kN / mm; the paired spring (3) is a paired disc spring with a stiffness of 5kN / mm; both are made of 60Si2Mn material and have been galvanized for corrosion protection.

3. The composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie member according to claim 1, characterized in that, The opposing springs (3) are arranged in a "reverse opposing" configuration, with a single piece thickness of 3mm, an outer diameter of 30mm, and an inner diameter of 15mm; the stacked springs (2) are arranged in a "same direction stacked" configuration, with a single piece thickness of 4mm, an outer diameter of 30mm, and an inner diameter of 12mm; both are limited by the annular step in the spring limiting seat (6) to form an energy storage unit with a total length of 45mm.

4. The composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie member according to claim 1, characterized in that, The rib (4) is made of 80% basalt fiber and 20% carbon fiber in a two-way weaving process; the fiber volume fraction is controlled at 65%-70% and the resin matrix is ​​modified epoxy resin with 10wt% nano SiO2 particles added.

5. A composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie rod according to claim 1, characterized in that, The surface of the rib (4) undergoes a two-step interface strengthening treatment: sandblasting roughening and silane coupling agent coating. The sandblasting roughening uses 80-mesh white corundum sand to form a micron-level concave-convex structure on the surface of the rib (4), increasing the frictional contact area with the anchor clip. The silane coupling agent is KH560, which is diluted with ethanol solution and uniformly coated on the surface of the rib. After drying at 80°C for 1 hour, the coupling agent molecules form chemical bonds with the hydroxyl groups on the fiber surface and the resin matrix, increasing the interfacial bonding strength to ≥25MPa and preventing the rib from peeling off from the resin matrix during the stress process.

6. The composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie member according to claim 1, characterized in that, The spring limit seat (6) is made of Q235 steel and has a 60μm thick anti-corrosion coating after powder coating treatment; it is connected to the elastic transition sleeve (11) of the rib (4) through the internal thread.

7. A composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie rod according to claim 6, characterized in that, The elastic transition sleeve (11) is located between the composite butterfly spring assembly and the rib (4). It has a thickness of 3-5 mm and a length of 30 mm. Its inner wall is interference-fitted with the rib (4), and its outer wall is fixed to the spring limit seat (6) by threads.

8. The composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie member according to claim 1, characterized in that, The assembly is completed through the following steps: Step 1: Insert the EPDM rubber waterstop ring into the sealing groove outside the reserved hole of the outer leaf wall panel, and control the compression rate of the waterstop ring at 30%; Place the anchor seat of the elastic wedge anchor into the reserved hole, and make the outer surface of the anchor seat flush with the surface of the wall panel with a deviation of ≤0.5mm. Use temporary support to fix it to avoid displacement of the anchor seat; Open the two-piece clamp of the anchor seat, insert the 100-150mm long outer leaf anchoring section of the rib (4) into the clamp, and calibrate it with a laser alignment instrument to ensure that the axis of the rib (4) is coaxial with the axis of the anchor seat with a deviation of ≤1mm; Close the clamp and tighten the locking nut on the outside of the anchor seat with a torque wrench to make the clamp and the rib (4) fit tightly together; Step 2: Insert the rib (4) from the outer leaf wall panel into the insulation layer. When the rib (4) passes through the insulation layer, it should be pushed slowly to avoid scratching the surface of the rib (4) or damaging the insulation layer. If resistance is encountered, use a guide sleeve to assist in the insertion. Forced impact is prohibited. When the installation scale of the stacked butterfly spring assembly of the rib (4) reaches the reserved hole position of the inner leaf wall panel, stop the insertion. Put the prefabricated stacked butterfly spring assembly into the rib. The spring limit seat (6) should be close to the outside of the reserved hole of the inner leaf wall panel. Ensure that the coaxial deviation between the stacked butterfly spring assembly and the rib (4) is ≤0.5mm by using the positioning scale. Use bolts to fix the spring limit seat (6) to the temporary support of the inner leaf wall panel to prevent the stacked butterfly spring assembly from shifting. Step 3: In the section of the rib (4) near the outer leaf wall panel, 50mm from the outer leaf anchor, insert a stainless steel corrugated pipe. The deviation between one end of the corrugated pipe and the outlet end of the outer leaf anchor is ≤1mm. The other end is fixed to the rib (4) by a stainless steel clamp. At the contact point between the corrugated pipe and the anchor and clamp, attach a water-swellable waterstop strip. The overlap length of the waterstop strip is ≥10mm to ensure a leak-free seal.

9. A composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie rod according to claim 8, characterized in that, The length of the BFRP tie rod is 300-800mm, of which the energy storage section accounts for 30%-40% of the length and the anchoring section accounts for 60%-70%.

10. A composite butterfly spring energy storage self-resetting low-loss prestressed BFRP tie rod according to claim 8, characterized in that, When the wall panel is subjected to horizontal seismic load and relative displacement occurs, when the displacement is ≤5mm, the BFRP reinforcement is pulled by tension and drives the composite butterfly spring group to compress and store energy. The spring first undergoes elastic deformation to dissipate energy, thus avoiding the BFRP reinforcement from directly bearing the impact load. When the wall panel is subjected to a horizontal seismic load and undergoes a large displacement, when the displacement is between 5-15mm, the superimposed springs participate in the deformation and provide the restoring force through the accumulation of elastic potential energy.

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