Prestressed roof truss beam tensioning method

Abstract

The invention discloses a prestressed roof truss beam tensioning method which comprises the following steps: S1, prefabricating a component: binding a steel reinforcement framework, mounting an embedded part, setting a reserved hole channel, and pouring and maintaining concrete in sequence to form a roof truss beam concrete component with the reserved hole channel; the prestressed steel strand is penetrated into the reserved hole channel, the prestressed steel strand is an intelligent sensing steel strand, the structure of the prestressed steel strand is that an optical fiber rope is replaced or merged into the center wire position or the stranded rope core of the prestressed steel strand, at least a plurality of optical fiber sensors are packaged in the optical fiber rope, and the optical fiber sensors are arranged in the optical fiber rope; and a plurality of steel wires are uniformly arranged outside the optical fiber rope or the central wire. According to the method, the tensioning quality is improved from'result verification 'to'process controllability and result knowing', the controllability and precision of the tensioning process are achieved, the problem that prestress application is unqualified due to unsmooth hole channels, equipment errors and the like is solved, and it is guaranteed that the initial state of the structure is healthy.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, specifically to a method for tensioning prestressed roof truss beams. Background Technology

[0002] Prestressed concrete polygonal roof trusses are core load-bearing roof components in large-span industrial plants, warehouses, public buildings, and other industrial and civil buildings. Their core principle is to introduce compressive stress into the concrete beam beforehand by tensioning high-strength steel strands to counteract the tensile stress generated by service loads, thereby improving the structure's crack resistance and load-bearing capacity. Therefore, prestressing tensioning is a crucial process that determines the final load-bearing performance of the roof truss beam and even the overall safety of the building.

[0003] Currently, traditional prestressed tensioning construction mainly relies on "dual control" of hydraulic pressure gauge readings and steel strand elongation values. This method has significant limitations: 1. Discrete process control: Hydraulic pressure gauge readings reflect the pressure of the jack cylinders, not the actual tension of the steel strands, and are affected by equipment friction and calibration errors; measuring elongation values ​​only shows the overall deformation at both ends of the steel strands, and cannot determine whether the force is transmitted evenly and effectively along the length of the duct. Especially when there is high friction in the duct or unexpected blockage, it is very easy to cause the actual effective prestress to deviate from the design value. 2. Lack of process traceability: The data of the tensioning process is instantaneous and isolated, and cannot fully reconstruct the establishment and distribution process of the internal force of each steel strand during the tensioning process. Once a problem occurs, it is difficult to accurately trace the cause. 3. Long-term quality hazards: Inaccurate prestressing may lead to early cracking of roof trusses, excessive deflection, or insufficient load-bearing capacity. These hazards are difficult to detect during construction acceptance, but pose a significant risk to the long-term safety of the building.

[0004] Furthermore, as a permanent load-bearing structure, the prestressed roof truss beam undergoes dynamic stress changes throughout its decades-long service life and is continuously subjected to various erosion factors: 1. Long-term load effects: continuous application of dead loads and repeated impacts and changes from live loads (such as snow loads, dust accumulation, and equipment hoisting); 2. Time-varying material effects: shrinkage and creep of concrete lead to continuous loss of prestress over time, and stress relaxation may occur in the reinforcing steel; 3. Environmental effects: temperature cycles (seasonal and diurnal temperature variations) cause thermal expansion and contraction stresses, and corrosive environments (industrial atmospheres, humid environments) may corrode the steel strands and concrete; 4. Accidents and aging: uneven foundation settlement, use exceeding design loads, natural material aging, and accidental impacts. These factors combined can lead to continuous prestress decay, stress redistribution, and even localized stress exceeding limits and microcrack propagation, ultimately threatening structural safety.

[0005] However, current technology is almost entirely lacking in long-term stress monitoring of roof trusses. Conventional manual periodic inspections (such as visual inspections and impact tests) cannot detect internal stress changes; traditional point sensors, such as resistance strain gauges, have low survival rates, poor durability, are difficult to install long-term, and involve complex wiring. Therefore, operators often only discover problems when visible cracks, excessive deformation, or other severe symptoms appear, by which time the structure has often entered a period of accelerated damage, resulting in high repair costs and safety risks. For locations with high internal storage value and dense personnel and equipment, such as grain silos, logistics centers, and large workshops, as well as public buildings with high population density, such as stadiums and exhibition halls, sudden failure of roof trusses can lead to catastrophic consequences. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the existing defects and provide a prestressed roof truss beam tensioning method, which realizes the improvement of tensioning quality from "result verification" to "process controllability and result knowability", realizes the controllability and precision of the tensioning process, avoids the problem of unqualified prestressing application caused by poor duct, equipment error, etc., and ensures the healthy initial state of the structure, which can effectively solve the problems in the background technology.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for tensioning prestressed roof truss beams, comprising the following steps: S1. Component prefabrication: The steel reinforcement cage is tied, the embedded parts are installed, the reserved ducts are set, and the concrete is poured and cured in sequence to form a roof truss beam concrete component with reserved ducts. S2, threading: thread the prestressed steel strand into the reserved channel, wherein the prestressed steel strand is an intelligent sensing steel strand, the structure of which is: at the center wire position of the prestressed steel strand or in the stranded core, an optical fiber rope is replaced or incorporated, the optical fiber rope is encapsulated with at least a number of optical fiber sensors, and a number of steel wires are evenly arranged on the outside of the optical fiber rope or the center wire. S3. Intelligent tensioning: The prestressed steel strand is tensioned. During the tensioning process, the fiber optic sensor collects and feeds back the strain or stress data of each key point along the length of the prestressed steel strand in real time to monitor the application process of the tensioning force, verify the tensioning synchronization, and check the final tensioning effect. S4. Grouting and Sealing: After tensioning, the ducts are grouted and the anchorage area is sealed. During sealing, a protective shell and inspection port are installed for the fiber optic signal transmission cable led out from the end of the prestressed steel strand, and an energy module and a data communication module are configured.

[0008] As a preferred embodiment of the present invention, the optical fiber sensor is a fiber optic grating sensor or a distributed optical fiber sensor based on Brillouin / Rayleigh scattering.

[0009] As a preferred embodiment of the present invention, the outer surface of the optical fiber rope is provided with a reinforcing protective layer.

[0010] As a preferred embodiment of the present invention, a number of isolation ropes are uniformly arranged between the outer side of the optical fiber rope and the steel wire.

[0011] As a preferred embodiment of the present invention, the energy module is an external solar panel with a built-in rechargeable battery, a replaceable battery compartment, or a reserved interface.

[0012] As a preferred embodiment of the present invention, the data communication module is a wireless transmission module or a wired transmission interface.

[0013] As a preferred technical solution of the present invention, in step S4, the protective shell is made of waterproof and corrosion-resistant material and is fixed to the end or side of the roof truss beam, and its inspection port is sealed with a sealing cover.

[0014] As a preferred embodiment of the present invention, the following steps are also included: S5. Long-term monitoring: After the roof truss beam is put into use, its stress changes are continuously monitored by the fiber optic sensor. The data is transmitted to the external monitoring system through the data communication module to realize long-term assessment of the structural health status and safety early warning.

[0015] As a preferred embodiment of the present invention, the following steps are also included: S6. Termination of Monitoring: When long-term monitoring is not required, the end of the intelligent sensing steel strand can be cut off before the anchor is closed, the sensing connection can be disconnected, and subsequent grouting and closure can be carried out according to the conventional prestressed tendons.

[0016] This invention also provides a long-term health monitoring system for roof trusses, characterized in that the prestressed roof trusses constructed using the above-mentioned prestressed roof truss tensioning method are used. The system includes: at least one bundle of prestressed steel strands embedded in the roof truss, equipped with optical fiber ropes and optical fiber sensors; a data acquisition instrument connected to the optical fiber sensors; an energy module for powering the acquisition instrument; a communication module for remote data transmission; and a remote monitoring center software platform for receiving and processing data, performing safety assessments, and issuing early warnings.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: An optical fiber cable with a built-in optical fiber sensor is integrated at the core position (usually the center wire) of the prestressed steel strand. During the tensioning construction of the roof truss beam, by connecting to an external optical fiber demodulator, strain data at key points along the prestressed steel strand can be read in real time and converted into stress. This allows for real-time display of the establishment and distribution process of tension force within the steel strand, facilitating the judgment of tension synchronization (when multiple strands are tensioned simultaneously). Simultaneously, it can accurately verify whether the final effective prestress value meets design requirements, especially verifying the actual stress after duct friction loss. This method improves the tensioning quality from "result verification" to "process controllability and result predictability," achieving controllability and precision in the tensioning process. It avoids problems such as unqualified prestressing application due to duct blockage or equipment errors, ensuring the healthy initial state of the structure.

[0018] This method also enables long-term monitoring of the health status of roof truss beam structures. Fiber optic sensors offer advantages such as resistance to electromagnetic interference, corrosion resistance, small size, ease of embedding, and distributed measurement capabilities. With a lifespan of several decades, matching the lifespan of the building structure, they perfectly solve the durability and reliability challenges of long-term monitoring. Embedding fiber optic sensors as part of the engineering materials during the construction phase avoids the high costs and secondary disturbances to the structure caused by later reinforcement and installation of the monitoring system—a one-time investment with lifelong benefits. Furthermore, the large amount of structural stress data accumulated during long-term monitoring can be used for scientific research, optimization of similar engineering designs, and, more importantly, provides operating units with a real-time dashboard of structural safety status, transforming "passive emergency response" into "proactive early warning," thus improving the safety management level of critical infrastructure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the reserved duct and prestressed steel strand structure of the present invention; Figure 2 This is a schematic diagram of the cross-sectional structure of the prestressed steel strand of the present invention.

[0020] In the figure: 1 Fixed end extrusion anchor, 2 Additional pad, 3 Roof truss embedded plate, 4 End expansion section tapered cylinder of the duct, 5 Prestressed steel strand, 51 Steel wire, 52 Fiber optic rope, 53 Fiber optic sensor, 54 Reinforced protective layer, 55 Isolation rope, 6 Plastic exhaust tile and lead-out plastic pipe, 7 Metal corrugated pipe, 8 Joint sleeve, 9 Tensioning end clamp anchor. Detailed Implementation

[0021] 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.

[0022] Please see Figure 1-2 This invention provides a technical solution: a method for tensioning prestressed roof truss beams, comprising the following steps: S1. Component Prefabrication: Proceed according to standard procedures: Tie the roof truss beam reinforcement cage; install embedded anchor plates, spiral reinforcement, and other embedded parts, ensuring accurate positioning; install corrugated metal pipes 7 to form reserved channels, and securely fix them with steel reinforcement supports at 800mm intervals; pour C55 concrete and cover and cure to design strength. During this stage, it is important to plan the path of future fiber optic signal cables leading from the beam ends when laying the corrugated pipes to avoid severe bending by the reinforcement.

[0023] Before laying the metal corrugated pipe, inspect its appearance for oil stains, holes, irregular wrinkles, and cracks at the seams. Unqualified materials can be removed in advance to prevent grout leakage from the source. During the laying process, avoid welding sparks that could burn the pipe wall to reduce the risk of corrugated pipe breakage during construction. If pipe wall damage is found, immediately repair it with plastic tape (width ≥ 50 mm), with ≥ 3 layers to ensure a complete seal at the damaged area. This prevents mortar from seeping into the duct during concrete pouring, ensures unobstructed flow in the duct, and provides a foundation for subsequent threading, tensioning, and grouting.

[0024] The metal corrugated pipe 7 is connected and fixed by a connector sleeve 8; several plastic exhaust tiles and plastic outlet pipes 6 are installed on the metal corrugated pipe 7.

[0025] S2. Threading: Fabrication of the intelligent sensing steel strand: Order or customize Φs15.2 low-relaxation steel strand conforming to national standards. During its production, a flexible fiber optic cord 52 (approximately 3mm in diameter, with an external high-strength polymer protective layer) containing multiple fiber Bragg grating sensors connected in series replaces the original central steel wire and is stranded together with the other six steel wires to ultimately form the intelligent sensing steel strand. Before leaving the factory, the entire sensing steel strand is calibrated to establish a precise relationship between strain and grating wavelength drift.

[0026] Alternatively, fiber optic cable 52 can be incorporated into the original central steel wire.

[0027] After the concrete strength of the roof truss beams reaches 100% of the design strength, the prestressed steel strands 5 are threaded into the reserved metal corrugated pipe channels using a winch or manually. Care should be taken to protect the fiber optic patch cord connectors extending from the ends of the steel strands during threading.

[0028] The structure of the prestressed steel strand 5 is as follows: at the center wire position or in the stranded core of the prestressed steel strand 5, an optical fiber rope 52 is replaced or incorporated. The optical fiber rope 52 is encapsulated with at least a number of optical fiber sensors 53. Several steel wires 51 are evenly arranged on the outside of the optical fiber rope 52 or the center wire. The outer surface of the optical fiber rope 52 is provided with a reinforcing protective layer 54, which can be a stainless steel flexible tube or spiral armor, etc., to effectively prevent the optical fiber rope 52 from scratching, squeezing and abrading the inner wall of the corrugated pipe channel, the steel bar support or other steel strands during the threading and tensioning process, avoid the optical fiber from breaking due to direct force, and at the same time disperse the stress from external point or local impacts, protecting the internal optical fiber from damage when bent, knotted or accidentally pulled.

[0029] Optionally, several strands of isolation rope 55 are evenly arranged between the outer side of the fiber optic rope 52 and the steel wire 51. The isolation rope 55 can be selected as polyester fiber rope, flexible plastic strip, rubber strip, or braided sleeve impregnated with lubricant, etc., to provide a uniform flexible buffer and physical isolation layer for the fiber optic rope 52 with built-in sensor, further dispersing the radial extrusion force and contact friction generated by the steel wire during stranding and under load, thereby reducing the risk of failure of fiber optic sensor 53 due to local stress concentration or wear, and ensuring the long-term stability and accuracy of monitoring signal.

[0030] S3, Intelligent Tensioning: System Connection: Connect the fiber optic patch cords at both ends of the prestressed steel strand 5 to two fiber Bragg grating demodulators via extension cables. Position the tensioning equipment, including jacks and oil pumps.

[0031] Tensioning process: Start the tensioning program (e.g., 0→10%σcon→100%σcon→103%σcon, hold the load for 5 minutes and anchor). During the tensioning process, the demodulator reads and displays the strain values ​​at the locations of each fiber Bragg grating sensor in real time.

[0032] Process monitoring: Operators can observe in real time whether the tension force is transmitted evenly. For example, the sensor reading near the tensioning end should rise first, and the sensor reading at the far end should follow. If the stress at the far end is consistently significantly lower, it indicates abnormal duct friction.

[0033] Result Verification: When tensioned to 103%σcon holding load, record the stable stress values ​​of each sensor. By calculating the average value and comparing it with the theoretical tension force, the actual effective prestress of this bundle of steel strands is directly obtained. If the stress value at a certain point deviates from the average value by more than ±5%, an early warning can be issued in this step, and supplementary tensioning can be considered.

[0034] S4. Grouting and Sealing: Within 48 hours after tensioning, vacuum grouting of the ducts shall be carried out in accordance with the specifications to ensure that the grout tightly wraps the prestressed steel strands.

[0035] Outside the anchor, fiber optic patch cords are connected to a dedicated protective housing. This housing integrates a miniature fiber optic demodulation and acquisition board (data acquisition and communication module), a rechargeable lithium battery pack (energy module), and a 4G or 5G wireless transmission unit. The housing is made of aluminum alloy, achieving an IP67 protection rating, and is bolted to the side of the roof truss beam end. An inspection port with a rubber seal is provided on the side of the housing for future battery replacement or module upgrades. The power supply can also be designed with pre-drilled slots and wiring interfaces for installing small solar panels on the top of the housing, enabling green energy, energy conservation, and emission reduction, particularly suitable for powering roof truss beams.

[0036] Data transmission can also use conventional wired transmission, which is more stable and suitable for buildings that require long-term security monitoring, such as grain warehouses, logistics centers, large workshops and other places with high internal storage value and dense personnel and equipment, as well as public buildings with a high concentration of people, such as stadiums and exhibition halls.

[0037] S5. Long-term monitoring: After the roof truss beam is put into use, the integrated system automatically collects stress data of each sensor point according to a preset cycle (such as once per hour) and uploads it to the cloud monitoring platform through the 4G or 5G network.

[0038] Routine monitoring: The platform displays real-time stress distribution cloud maps of each roof truss beam and records daily and quarterly stress change curves.

[0039] Safety Warning: Set multiple alarm thresholds. Level 1 Alarm (Warning): When the stress at a certain point changes abruptly by more than ±10% from the long-term reference value (which may indicate local overload or damage); Level 2 Alarm (Alarm): When the stress value continues to develop in an unfavorable direction (such as a continuous increase in tensile stress), or approaches 80% of the material's allowable stress limit.

[0040] Performance assessment: By analyzing data from several years, the rate of prestress loss caused by concrete creep and shrinkage can be quantified, providing key data support for assessing the remaining life of the structure and whether future prestressing reinforcement is necessary.

[0041] S6. Termination of Monitoring: For projects that do not require long-term monitoring, after tensioning and calibration but before grouting, the fiber optic jumpers at both ends of the intelligent sensing steel strand can be cut directly, and then it can be used as a regular steel strand for grouting and anchoring. This solution only utilizes the value of this invention in construction quality control.

[0042] The fiber optic sensor 53, jack, oil pump, miniature fiber optic demodulation and acquisition board, rechargeable lithium battery pack, wireless transmission module, solar panel and related equipment used in this application are all commonly used electronic components in the prior art. Their specific structures, working principles, control methods and circuit connections are all well-known technologies and will not be described in detail here.

[0043] In the preferred technical solution, the fiber optic sensor 53 is a fiber optic grating sensor or a distributed fiber optic sensor based on Brillouin / Rayleigh scattering, which realizes continuous or quasi-distributed real-time measurement of the stress state of the prestressed steel strand 5 along its entire length. This breaks through the limitations of traditional point measurement technology and can obtain the distribution gradient and abnormal points of force during the transmission process, providing full-dimensional data for tensioning process optimization and long-term health diagnosis.

[0044] Both ends of the metal corrugated pipe 7 are provided with roof truss embedded plates 3 and duct end expansion section tapered cylinders 4. The fixed end of the metal corrugated pipe 7 is provided with a fixed end extrusion anchor 1, and the fixed end of the metal corrugated pipe 7 is also provided with an additional pad plate 2. The tensioning end of the metal corrugated pipe 7 is provided with a tensioning end clamping anchor 9.

[0045] The present invention also provides a long-term health monitoring system for roof trusses, characterized in that the prestressed roof trusses constructed using the above-mentioned prestressed roof truss tensioning method are used. The system includes: at least one bundle of prestressed steel strands 5 embedded in the roof truss, equipped with optical fiber ropes 52 and optical fiber sensors 53; a data acquisition instrument connected to the optical fiber sensors 53; an energy module for powering the acquisition instrument; a communication module for remote data transmission; and a remote monitoring center software platform for receiving and processing data, performing safety assessments and early warnings.

[0046] All parts not disclosed in this invention are prior art, and their specific structures, materials, and working principles will not be described in detail. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for tensioning prestressed roof truss beams, characterized in that, Includes the following steps: S1. Component prefabrication: The steel reinforcement cage is tied, the embedded parts are installed, the reserved ducts are set, and the concrete is poured and cured in sequence to form a roof truss beam concrete component with reserved ducts. S2, threading: thread the prestressed steel strand (5) into the reserved channel, wherein the prestressed steel strand (5) is an intelligent sensing steel strand, the structure of which is: at the center wire position of the prestressed steel strand (5) or in the stranded core, a fiber optic rope (52) is replaced or incorporated, the fiber optic rope (52) is encapsulated with at least a number of fiber optic sensors (53), and a number of steel wires (51) are evenly arranged on the outside of the fiber optic rope (52) or the center wire. S3, Intelligent tensioning: The prestressed steel strand (5) is tensioned. During the tensioning process, the strain or stress data of each key point along the length direction of the prestressed steel strand (5) is collected and fed back in real time through the fiber optic sensor (53) to monitor the application process of the tensioning force, verify the tensioning synchronization, and check the final tensioning effect. S4. Grouting and sealing: Grouting is carried out in the duct after tensioning and the anchorage area is sealed. During sealing, a protective shell and inspection port are set for the optical fiber signal transmission cable led out from the end of the prestressed steel strand (5), and an energy module and a data communication module are configured.

2. The method for tensioning prestressed roof truss beams according to claim 1, characterized in that: The fiber optic sensor (53) is a fiber optic grating sensor or a distributed fiber optic sensor based on Brillouin / Rayleigh scattering.

3. The method for tensioning prestressed roof truss beams according to claim 1, characterized in that: The outer surface of the optical fiber rope (52) is provided with a reinforced protective layer (54).

4. A method for tensioning prestressed roof truss beams according to claim 1 or 3, characterized in that: Several strands of isolation rope (55) are evenly arranged between the outer side of the optical fiber rope (52) and the steel wire (51).

5. The method for tensioning prestressed roof truss beams according to claim 1, characterized in that: The energy module is an external solar panel with a built-in rechargeable battery, a replaceable battery compartment, or a reserved interface.

6. The method for tensioning prestressed roof truss beams according to claim 1, characterized in that: The data communication module is a wireless transmission module or a wired transmission interface.

7. The method for tensioning prestressed roof truss beams according to claim 1, characterized in that: In step S4, the protective shell is made of waterproof and corrosion-resistant materials and is fixed to the end or side of the roof truss beam. Its inspection port is sealed with a sealing cover.

8. The method for tensioning prestressed roof truss beams according to claim 1, characterized in that: It also includes the following steps: S5. Long-term monitoring: After the roof truss beam is put into use, its stress change is continuously monitored by the fiber optic sensor (53). The data is transmitted to the external monitoring system through the data communication module to realize long-term assessment of the structural health status and safety early warning.

9. The method for tensioning a prestressed roof truss beam according to claim 8, characterized in that: It also includes the following steps: S6. Termination of Monitoring: When long-term monitoring is not required, the end of the intelligent sensing steel strand can be cut off before the anchor is closed, the sensing connection can be disconnected, and subsequent grouting and closure can be carried out according to the conventional prestressed tendons.

10. A long-term health monitoring system for roof truss beams, characterized in that, The prestressed roof truss beam constructed using any of the methods described in claims 1-9, the system comprising: at least one bundle of prestressed steel strands (5) embedded in the roof truss beam and equipped with an optical fiber rope (52) and an optical fiber sensor (53), a data acquisition instrument connected to the optical fiber sensor (53), an energy module for powering the acquisition instrument, a communication module for remote data transmission, and a remote monitoring center software platform for receiving and processing data and performing safety assessments and early warnings.

Images