SMA self-adaptive bridge pier reinforcing-monitoring integrated structure and construction method

Abstract

The invention discloses an SMA self-adaptive bridge pier reinforcing-monitoring integrated structure and a construction method, the SMA self-adaptive bridge pier reinforcing-monitoring integrated structure comprises an exoskeleton vertical frame, the exoskeleton vertical frame is provided with an SMA strap system, an FBG sensing and collecting system and a heating control system, an SMA self-tightening exoskeleton and FBG monitoring integrated structure is adopted, and self-adaptive prestress control and real-time state monitoring of bridge pier reinforcing are achieved; the SMA strap system is provided with an SMA strap, a bolt clamp, a friction gasket, a high-strength bolt and a nut; the FBG sensing and acquisition system is provided with an FBG sensor, an optical fiber signal line, a protective sleeve and a data acquisition module; the heating control system is provided with an electric heating wire and a temperature control device; the FBG sensing and acquisition system monitors the stress state of the SMA strap and the local strain of the bridge pier, the FBG sensor is adhered to the outer surface of the SMA strap and is connected with the data acquisition module through an optical fiber signal line, and the signal line along the way is arranged in the protective sleeve. The bridge pier reinforcing effect and the maintenance efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of civil engineering structure reinforcement and health monitoring technology, and to an integrated structure and construction method for SMA adaptive bridge pier reinforcement and monitoring. In particular, it relates to a bridge pier exoskeleton reinforcement structure and construction method that uses shape memory alloy (SMA) to achieve a self-tightening effect and combines fiber optic grating (FBG) sensing technology. Background Technology

[0002] As bridges age, their piers develop defects such as cracking, steel reinforcement corrosion, and strength degradation. Common reinforcement methods include steel sleeves, CFRP fabric wrapping, and thickened concrete sleeves. These methods require extensive on-site work during construction, and the prestress after reinforcement is difficult to adjust, leading to insufficient monitoring capabilities.

[0003] There is currently a bridge pier reinforcement scheme using steel hoops and bolts, but its preload decreases significantly over time and requires regular testing with the help of external equipment, lacking real-time monitoring capabilities.

[0004] In summary, existing bridge pier reinforcement and monitoring technologies have the following problems: 1. Prestress is not self-adjustable: tensioning of steel hoops requires manual force and must be designed according to the cross-sectional characteristics of the pier column, which leads to loosening and corrosion over time; 2. Insufficient monitoring capabilities: There is no real-time strain / stress data, making it impossible to dynamically evaluate the reinforcement effect; 3. Difficult maintenance: The reinforcement components are fixed to the bridge pier and cannot be disassembled, resulting in low reuse rate and high construction costs.

[0005] Therefore, it is necessary to develop new bridge pier reinforcement and monitoring technologies to overcome the above problems. Summary of the Invention

[0006] Purpose of the invention: To address the shortcomings and defects of existing technologies, this invention provides an integrated structure and construction method for SMA adaptive bridge pier reinforcement and monitoring. It provides an integrated structure of "SMA self-tightening exoskeleton + FBG monitoring" to achieve adaptive prestress control and real-time status monitoring of bridge pier reinforcement, thereby improving the reinforcement effect and maintenance efficiency of bridge piers.

[0007] Technical Solution: This invention discloses an integrated SMA adaptive bridge pier reinforcement-monitoring structure, comprising an exoskeleton vertical frame. The exoskeleton vertical frame is equipped with an SMA hoop system, an FBG sensing and acquisition system, and a heating control system. It adopts an integrated structure of "SMA self-tightening exoskeleton + FBG monitoring" to achieve adaptive prestress control and real-time status monitoring of bridge pier reinforcement. The SMA hoop system includes SMA hoops, bolt clamps, friction washers, high-strength bolts, and nuts. The FBG sensing and acquisition system includes FBG sensors, fiber optic signal lines, a protective sleeve, and a data acquisition module. The heating control system includes heating wires and a temperature control device. The FBG sensing and acquisition system monitors the stress state of the SMA hoops and the local strain of the bridge pier. The FBG sensor is attached to the outer surface of the SMA hoop and connected to the data acquisition module via a fiber optic signal line, with the signal line placed inside the protective sleeve.

[0008] The exoskeleton vertical frame includes two high-strength T-shaped steel columns, which are respectively arranged on both sides of the pier as anti-bending components. The bottom steel base of the exoskeleton vertical frame is embedded in the pier cap, and the longitudinally welded horizontal stiffening ribs enhance the stability of the columns and provide a lateral support interface for the bolt clamps.

[0009] The SMA hoop system provides circumferential active prestress to reinforce the bridge pier. The SMA hoop consists of two symmetrical semi-circular shape memory alloy strips, which are heated and wrapped around the outside of the bridge pier. After cooling, they retract to apply prestress. The ends of the SMA hoop are fixed by bolt clamps. The bolt clamps are equipped with friction pads to enhance the reliability of the anchorage. The final clamping is achieved by high-strength bolts and nuts.

[0010] The bolt clamp includes two high-strength steel pressure plates. The outer ear plate of the bolt clamp is connected to the T-shaped steel column to form a stable force transmission path. Friction pads are pasted on the inner side of the bolt clamp to enhance the friction between the SMA band and the bolt clamp. High-strength bolts and nuts are passed through the clamp holes for pre-tightening and clamping, so that the SMA band is stably anchored after cooling and shrinking.

[0011] The FBG sensor is attached to the outer surface of the SMA hoop and arranged circumferentially. The data acquisition module is installed on the top or bottom of the column or the upper platform of the pier, supporting signal conditioning, remote communication and real-time recording.

[0012] The heating control system is used to stimulate the shape memory effect of SMA material during construction. The heating wire is attached to the outer surface of the SMA band or embedded inside it. It is connected to the temperature control device through the power cord to achieve local heating, precise temperature control and safe start and stop, and ensure that the SMA is heated uniformly to the austenitic phase transformation temperature.

[0013] The heating wire is powered by a power supply wire laid in the path of the column, and the temperature control device is integrated into the top of the exoskeleton or in an external control box.

[0014] The present invention discloses a construction method for an integrated SMA adaptive pier reinforcement-monitoring structure, characterized by comprising the following steps:

[0015] 1) Prefabricated exoskeleton vertical frame: Horizontal stiffening ribs are longitudinally welded onto high-strength T-shaped steel columns. After the prefabricated exoskeleton vertical frame is positioned on both sides of the pier, the base is embedded into the pier cap and fixed.

[0016] 2) Precast semi-circular SMA hoops are spliced ​​together circumferentially to wrap around the surface of the pier to form a strip-shaped whole, and the longitudinal spacing of the reinforcement should be more than 300mm;

[0017] 3) Bolt clamps are used to anchor the SMA hoops to the vertical frame of the exoskeleton at the circumferential splice joints. Friction pads, high-strength bolts and nuts are provided between two adjacent SMA hoops in the circumferential direction.

[0018] 4) The SMA hoop is heated to the austenitic phase transformation temperature by heating wire and temperature control device. After the SMA hoop cools to room temperature, self-tightening pressure is formed.

[0019] 5) Attach the FBG sensor to each semi-circular SMA hoop, bundle the fiber optic signal lines into the protective sleeve, and set the protective sleeve inside the vertical frame of the exoskeleton for protection. Connect the fiber optic signal lines to the data acquisition module for initial calibration and record the initial tensile stress.

[0020] 6) Remove the heating wire and temperature control device, perform on-site protection of the data acquisition module and enable real-time monitoring to record the stress on the bridge piers online;

[0021] 7) If the tensile stress is lower than the design value, repeat the above steps.

[0022] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: This invention provides an integrated structure of "SMA self-tightening exoskeleton + FBG monitoring," enabling adaptive prestress control and real-time status monitoring for bridge pier reinforcement. It eliminates the need to design the geometric dimensions of reinforcement components based on the bridge pier cross-section, improving reinforcement effectiveness and maintenance efficiency. This invention provides long-term stable adaptive prestress reinforcement, increasing the longitudinal and circumferential stiffness of the bridge pier; it enables real-time monitoring of stress and deformation, enhancing structural safety; the frame is modularly disassembled, resulting in high reusability; and the amount of engineering construction is reduced by more than 30%, significantly improving maintenance efficiency. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the bridge pier SMA exoskeleton reinforcement according to the present invention;

[0024] Figure 2 This is a schematic cross-sectional view of the bridge pier SMA exoskeleton reinforcement structure of the present invention;

[0025] Figure 3 This is a schematic diagram showing the detailed structure of the SMA band and connection of the present invention;

[0026] Figure 4 This is a layout diagram of the FBG sensing and acquisition system and the heating control system of the present invention;

[0027] In the figure, 1 is the vertical frame of the exoskeleton; 2 is the SMA hoops; 3 is the bolt clamps; 4 is the friction pads; 5 is the high-strength bolts and nuts; 6 is the FBG sensor; 7 is the fiber optic signal line; 8 is the protective sleeve; 9 is the data acquisition module; 10 is the heating wire; and 11 is the temperature control device. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0029] The SMA adaptive pier reinforcement-monitoring integrated structure of the present invention includes:

[0030] The exoskeleton vertical frame 1 consists of two high-strength T-shaped steel columns, which are respectively arranged on both sides of the pier to serve as the bending-resistant components of this system. The steel base at its bottom is pre-embedded in the pier cap, and horizontal stiffening ribs are welded longitudinally to enhance the stability of the column and provide a lateral support interface for the bolt clamps.

[0031] SMA hoop system: used to provide circumferential active prestressing reinforcement for bridge piers. SMA hoop 2 consists of two symmetrical semi-circular shape memory alloy strips, which are heated and wrapped around the outside of the bridge pier, and then retracted after cooling to apply prestress. The ends of the hoop are fixed by bolt clamps 3, with friction pads 4 inside the clamps to enhance anchoring reliability, and finally clamped by high-strength bolts and nuts 5.

[0032] FBG Sensing and Acquisition System: Used to monitor the stress state of the SMA bands and the local strain of the piers. FBG sensors 6 are attached to the outer surface of the SMA and connected to the data acquisition module 9 via fiber optic signal lines 7. The signal lines are protected within protective sleeves 8. This system supports multi-point deployment and remote monitoring, ensuring the ability to perceive the structural condition.

[0033] Heating control system: used to activate the shape memory effect of SMA material during construction. Heating wire 10 is attached to the outer surface of SMA or embedded inside it, and connected to temperature control device 11 through power cord to achieve local heating, precise temperature control and safe start and stop, ensuring that SMA is uniformly heated to the austenitic phase transformation temperature (about 100°C).

[0034] The SMA adaptive pier reinforcement-monitoring integrated structure of this invention has the following component connection and positional relationships:

[0035] The exoskeleton vertical frame 1 is installed on both sides of the bridge pier and pre-embedded in the bearing platform via a bottom steel base. Multiple stiffening ribs are welded longitudinally to the T-shaped steel columns to enhance the rigidity of the columns and provide a stable support platform for the SMA bolt clamps 3.

[0036] SMA hoop system: The SMA hoop 2 consists of two semi-circular alloy strips, which overlap and wrap around the outer surface of the pier, then are inserted into the bolt clamp 3. The bolt clamp consists of two high-strength steel pressure plates, with their outer lugs rigidly connected to the T-shaped steel column to form a stable force transmission path. Friction pads 4 are attached to the inside of the clamp to enhance the friction between the SMA and the clamp. High-strength bolts and nuts 5 are pre-tightened through the clamp holes to ensure stable anchoring of the SMA strip after cooling and shrinkage.

[0037] FBG Sensing and Acquisition System: FBG sensors 6 are circumferentially arranged and attached to the outer surface of the SMA hoop 2 to sense its deformation and prestress state. The sensors are connected to the data acquisition module 9 via fiber optic signal lines 7. The signal lines are laid along the column or pier and pass through protective sleeves 8 to prevent external mechanical damage. The data acquisition module 9 is installed on the top or bottom of the column or on the upper platform of the pier, supporting signal conditioning, remote communication, and real-time recording.

[0038] Heating control system: The heating wire 10 is attached to or embedded in the outer surface of the SMA belt. During heating, it is powered by a power wire laid in the column path. The wire is connected to the temperature control device 11, which is integrated into the top of the exoskeleton or in an external control box. The temperature control device can precisely control the heating temperature and time to ensure that the SMA belt reaches the austenitic phase transformation temperature and achieves prestress application.

[0039] Example:

[0040] The SMA adaptive pier reinforcement-monitoring integrated structure in this embodiment:

[0041] Pier parameters: diameter 1m, height 5m.

[0042] Exoskeleton frame: 2 uprights, each made of Q355B steel with a cross-section of 150mm×100mm, and fixed at the bottom with adjustable wedges.

[0043] SMA ties: 100mm wide, 5mm thick, spaced 0.5m apart, with a prestress of approximately 50-80MPa;

[0044] FBG sensing system: Two FBG sensors are installed on each band, with an accuracy of 10με and a sampling frequency of 1Hz.

[0045] The construction method includes the following steps:

[0046] 1) The prefabricated exoskeleton vertical frame 1 is made by longitudinally welding horizontal stiffening ribs onto high-strength T-shaped steel columns. After positioning the prefabricated exoskeleton vertical frame 1 on both sides of the pier, the base is embedded into the pier cap and fixed.

[0047] 2) Precast semi-circular SMA hoops 2, circumferentially spliced ​​and wrapped around the surface of the pier to form a strip-shaped whole, with a longitudinal spacing of more than 300mm for reinforcement;

[0048] 3) At the circumferential splicing point of the SMA hoop 2, bolt clamps 3 are used to anchor it to the vertical frame 1 of the exoskeleton. Friction pads 4 and high-strength bolts and nuts 5 are provided between two adjacent circumferential SMA hoop 2.

[0049] 4) The SMA hoop 2 is heated to the austenitic phase transformation temperature by the heating wire 10 and the temperature control device 11. After the SMA hoop 2 cools to room temperature, a self-tightening hoop pressure is formed.

[0050] 5) Attach the FBG sensor 6 to each semi-circular SMA hoop 2, bundle the fiber optic signal line 7 into the protective sleeve 8, and set the protective sleeve 8 inside the vertical frame 1 of the exoskeleton for protection. Connect the fiber optic signal line 7 to the data acquisition module 9 for initial calibration and record the initial tensile stress.

[0051] 6) Remove the heating wire 10 and temperature control device 11, perform on-site protection on the data acquisition module 9 and start real-time monitoring to record the stress on the bridge pier online;

[0052] 7) If the tensile stress is lower than the design value, repeat the above steps.

[0053] Testing revealed that this invention provides an integrated structure of "SMA self-tightening exoskeleton + FBG monitoring," enabling adaptive prestress control and real-time status monitoring for bridge pier reinforcement. It eliminates the need to design reinforcement component geometry based on pier cross-sections, improving reinforcement effectiveness and maintenance efficiency. This invention provides long-term stable adaptive prestress reinforcement, increasing the longitudinal and circumferential stiffness of bridge piers; it enables real-time monitoring of stress and deformation, enhancing structural safety; the frame is modularly disassembled, resulting in high reusability; and the amount of construction work is reduced by more than 30%, significantly improving maintenance efficiency.

Claims

1. An integrated SMA adaptive pier reinforcement-monitoring structure, characterized in that: The system includes an exoskeleton vertical frame (1), which is equipped with an SMA hoop system, an FBG sensing and acquisition system, and a heating control system. It adopts an integrated structure of "SMA self-tightening exoskeleton + FBG monitoring" to realize adaptive prestress control and real-time status monitoring of bridge pier reinforcement. The SMA hoop system is equipped with SMA hoop (2), bolt clamps (3), friction pads (4), and high-strength bolts and nuts (5). The FBG sensing and acquisition system is equipped with an FBG sensor (6), an optical fiber signal line (7), a protective sleeve (8), and a data acquisition module (9). The heating control system is equipped with an electric heating wire (10) and a temperature control device (11). The FBG sensing and acquisition system monitors the stress state of the SMA hoop (2) and the local strain of the bridge pier. The FBG sensor (6) is attached to the outer surface of the SMA hoop (2) and connected to the data acquisition module (9) through the optical fiber signal line (7). The signal line along the way is placed inside the protective sleeve (8).

2. The SMA adaptive pier reinforcement-monitoring integrated structure according to claim 1, characterized in that: The exoskeleton vertical frame (1) includes two high-strength T-shaped steel columns, which are respectively arranged on both sides of the pier as anti-bending components. The bottom steel base of the exoskeleton vertical frame (1) is embedded in the pier cap. The longitudinal welding of horizontal stiffening ribs enhances the stability of the columns and provides a lateral support interface for the bolt clamp (3).

3. The SMA adaptive pier reinforcement-monitoring integrated structure according to claim 1, characterized in that: The SMA hoop system provides circumferential active prestress to reinforce the bridge pier. The SMA hoop (2) consists of two symmetrical semi-circular shape memory alloy strips. After heating, it is wrapped around the outside of the bridge pier and then retracted after cooling to apply prestress. The ends of the SMA hoop (2) are fixed by bolt clamps (3). The bolt clamps (3) are equipped with friction pads (4) to enhance the reliability of the anchorage. The final clamping is achieved by high-strength bolts and nuts (5).

4. The SMA adaptive pier reinforcement-monitoring integrated structure according to claim 3, characterized in that: The bolt clamp (3) includes two high-strength steel pressure plates. The outer ear plate of the bolt clamp (3) is connected to the T-shaped steel column to form a stable force transmission path. Friction pads (4) are pasted on the inner side of the bolt clamp (3) to enhance the friction between the SMA band (2) and the bolt clamp (3). The high-strength bolt and nut (5) pass through the clamp hole for pre-tightening and clamping, so that the SMA band (2) is stably anchored after cooling and shrinkage.

5. The SMA adaptive pier reinforcement-monitoring integrated structure according to claim 1, characterized in that: The FBG sensor (6) is attached to the outer surface of the SMA hoop (2) and arranged in a circumferential manner. The data acquisition module (9) is installed on the top or bottom of the column or the upper platform of the pier, supporting signal conditioning, remote communication and real-time recording.

6. The SMA adaptive pier reinforcement-monitoring integrated structure according to claim 1, characterized in that: The heating control system is used to stimulate the shape memory effect of SMA material during construction. The heating wire (10) is attached to the outer surface of the SMA band (2) or embedded inside it. It is connected to the temperature control device (11) through the power wire to realize local heating, precise temperature control and safe start and stop, and ensure that the SMA is uniformly heated to the austenitic phase transformation temperature.

7. The SMA adaptive pier reinforcement-monitoring integrated structure according to claim 6, characterized in that: The heating wire (10) is powered by a power wire laid in the path of the column when it is heated, and the temperature control device (11) is integrated in the top of the exoskeleton or in the external control box.

8. A construction method for an integrated SMA adaptive pier reinforcement-monitoring structure, characterized in that: Includes the following steps: 1) Prefabricated exoskeleton vertical frame (1), with horizontal stiffening ribs welded longitudinally on high-strength T-shaped steel columns, and the prefabricated exoskeleton vertical frame (1) positioned on both sides of the pier, and the base embedded in the pier cap and fixed. 2) Precast semi-circular SMA hoops (2), circumferentially spliced ​​and wrapped around the surface of the pier to form a strip-shaped whole, and the longitudinal spacing of the reinforcement should be more than 300mm; 3) Bolt clamps (3) are used to anchor the SMA bands (2) to the vertical frame (1) of the exoskeleton at the circumferential splice. Friction pads (4) and high-strength bolts and nuts (5) are provided between two adjacent SMA bands (2) in the circumferential direction. 4) The SMA hoop (2) is heated to the austenitic phase transformation temperature by heating wire (10) and temperature control device (11). After the SMA hoop (2) cools to room temperature, a self-tightening hoop pressure is formed. 5) Attach the FBG sensor (6) to each semi-circular SMA hoop (2), bundle the fiber optic signal line (7) into the protective sleeve (8), set the protective sleeve (8) inside the vertical frame (1) of the exoskeleton for protection, connect the fiber optic signal line (7) to the data acquisition module (9) for initial calibration, and record the initial tensile stress. 6) Remove the heating wire (10) and temperature control device (11), perform on-site protection on the data acquisition module (9) and start real-time monitoring to record the stress on the bridge pier online; 7) If the tensile stress is lower than the design value, repeat the above steps.

9. The construction method of the SMA adaptive pier reinforcement-monitoring integrated structure according to claim 8, characterized in that: Obtain the SMA adaptive pier reinforcement-monitoring integrated structure as described in any one of claims 1-8.

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