BIM-based prestressed beam cutting construction process

Abstract

The application discloses a prestressed beam cutting construction process based on BIM, and the process steps are as follows: first, collecting bridge completion drawings and prestressed system data, establishing a BIM model and marking the position of steel beam; then, through model analysis, dividing small beam sections, planning cutting surfaces and quantifying safety distances; then, pre-disassembling non-core components such as side wings and face plates, deploying support systems, track-type rope saw cutting machines and infrared cameras; when debugging the equipment, setting large-diameter cutting operation holes and precise water cooling parameters; finally, remotely controlling the cutting machine, superimposing infrared images and BIM models, identifying steel bars and steel beams by using material thermal conductivity differences, and intervening in real time to avoid risks; when cutting the end of the beam, multiple cutting machines are simultaneously arranged to work cooperatively, so that the stress balance of the beam is guaranteed. The process realizes cutting digitization, visualization and unmanned operation, improves construction safety and efficiency, and provides a reliable technical scheme for the removal of prestressed beams.

Description

Technical Field

[0001] This invention relates to the technical field of bridge structure demolition construction methods, specifically to a BIM-based prestressed beam cutting construction process. Background Technology

[0002] Traditional bridge demolition methods include blasting and mechanical hoisting. The former causes significant disturbance to the surrounding environment, while the latter makes it difficult to precisely control the stress on large components, neither of which is suitable for complex prestressed beam structures. In recent years, however, prestressed beams have been increasingly used in bridge systems. Therefore, how to safely and effectively dismantle the prestressed beams in bridges that need to be demolished is a crucial aspect of bridge demolition engineering.

[0003] Traditional prestressed beam dismantling processes, for continuous prestressed beams, require prestressing the prestressed steel strands at their structural anchorage ends using specialized equipment. This transforms the prestressed beam into a regular reinforced concrete beam before subsequent demolition, dismantling, and transportation. However, for beams with short prestressed steel strands, since the prestressed strands are anchored at both ends within a single beam segment or within the same bridge section, prestressing each segment individually is complex, costly, and can cause localized damage to the beam, making it difficult to implement. In such cases, existing methods often involve pre-cutting the entire bridge into multiple small, internally prestressed beams for demolition. Specifically, this involves: first, identifying and marking the positions of the prestressed steel strands in the beams based on the drawings; then, erecting a support system such as scaffolding or a lifting system to avoid cutting into the steel strands, transferring the weight and prestressed system of the beams to the temporary scaffolding or lifting system; finally, cutting the beams into smaller segments; and finally, transporting the complete small beams away from the site using transportation equipment for subsequent demolition, dismantling, and removal of the remaining beams.

[0004] The traditional cutting methods described above suffer from multiple technical bottlenecks: First, the positioning and cutting process of prestressed steel strands mainly rely on drawings and manual experience, lacking digital visualization support, making it difficult to address the issue of steel strand position deviation caused by construction errors. Second, temporary support systems are mostly fixed structures, unable to dynamically adjust the support strength according to the beam load, easily leading to risks such as beam subsidence and displacement during the cutting process. Third, the cutting process lacks real-time monitoring methods, making it impossible to promptly identify steel strand approach signals, and relying on close-range operation by personnel poses significant safety hazards. If the position of the prestressed steel strands within the beam is misassessed, or if the cutting surface is not effectively monitored during the cutting process, it is easy to accidentally cut the prestressed steel strands. In this case, the energy stored in the prestressed system will be released instantly, causing minor damage to the entire concrete beam, making subsequent cutting operations and beam relocation difficult and increasing construction complexity; in severe cases, some concrete may explode due to the release of energy from the prestressed steel strands (such as in bonded prestressed systems), or the steel strands may be rapidly ejected (such as in unbonded prestressed systems), causing concrete blocks, metal fragments, etc., to fly around the construction site, resulting in serious construction safety hazards and even posing a fatal danger to on-site personnel. Furthermore, traditional cutting processes are inefficient, cannot achieve multi-equipment collaborative operation, and the simultaneous cutting of non-core components and the main body can easily cause process interference, further extending the construction period. Therefore, if the position of the prestressed beam steel strands can be more intuitively and accurately located as a guide for the cutting surface, a dynamically stable support system can be constructed, and the cutting process can be effectively monitored to achieve remote, unmanned prestressed beam cutting, the risks associated with prestressed beam cutting can be effectively prevented and avoided, further ensuring the safety and efficiency of the prestressed beam demolition process. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a BIM-based prestressed beam cutting construction process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a BIM-based prestressed beam cutting construction process, comprising the following steps:

[0007] Step S1: Data collection and BIM modeling: Obtain engineering drawings of the structure containing the prestressed beam to be demolished, extract the prestressing system data, construct the BIM model of the structure and mark the position of the prestressed steel strands in the beam;

[0008] Step S2: Model Analysis and Cutting Surface Planning: Based on the BIM model, analyze the distribution pattern of prestressed steel strands, divide the beam into cutting units in combination with the integrity of the prestressed system, and plan the cutting area between units;

[0009] Step S3: Construction preparation and pretreatment: Deploy lifting equipment and wire saw cutting machine, cut and dismantle non-load-bearing auxiliary structures of the beam and transfer them off-site by lifting equipment;

[0010] Step S4: Deployment of support system, automated operation and monitoring equipment: Set up temporary support devices below the cutting area, install a track on the beam surface and assemble a wire saw cutting machine with a remote control module, and install an infrared camera for real-time acquisition of images of the cut surface.

[0011] Step S5: Equipment debugging and water cooling parameter setting: Pre-set the cutting operation holes in the cutting area and assemble the cutting components. Set up the water cooling system aligned with the cutting area and adjust the water flow speed to ensure the function of the infrared camera; start the equipment and check the operating status.

[0012] Step S6: Remote Cutting and Real-time Monitoring: After the construction personnel have left, the cutting of the beam cutting unit divided in Step S2 is started through the remote control module; the image data collected by the infrared camera is fused with the BIM model to dynamically monitor the cutting process. If steel bars are detected, an alarm is triggered, and the cutting parameters or path are adjusted based on the alarm and monitoring results.

[0013] Step S7: Cutting unit completion and equipment transfer: After cutting is completed, the equipment is shut down via remote control module, the operators dismantle the cutting components and transfer the equipment to the corresponding area of ​​the next cutting unit; the beam unit is separated and transferred to the designated area using temporary support devices.

[0014] Preferably, the bridge where the prestressed beam is located includes a beam and piers. The beam includes side wings, a panel, a bottom plate, and a web containing prestressed steel strands. The prestressed system data in step S1 includes beam dimensions, pier dimensions, beam reinforcement layout, prestressed steel strand positions, and concrete grade. During BIM modeling, the positions of the prestressed steel strands in the beam are highlighted with color.

[0015] Preferably, the beam cutting unit division based on the integrity of the prestressed system in step S2 specifically involves dividing the beam into several small beam segments according to the principle that each prestressed steel strand is an independent and complete prestressed system; the cutting area planning needs to avoid the prestressed steel strand anchorage area and the bent-up section, and meet the safety distance requirements with the prestressed anchorage end; based on the planned cutting surface, the wire saw cutting process can be simulated through the BIM model, and the three-dimensional view and sectional view of the cutting surface can be extracted and integrated to generate a file containing the cutting position number.

[0016] Preferably, the safety distance is as follows: for bonded prestressed steel strands, the safety distance is not less than 30cm; for unbonded prestressed steel strands, the safety distance is greater than the maximum possible retraction length Ls of the steel strand at the fracture point, where Ls=(Δσ×L) / E, Δσ is the effective stress of the steel strand in MPa, L is the length from the anchor end to the cutting point in m, and E is the elastic modulus of the steel strand in MPa.

[0017] Preferably, the non-load-bearing auxiliary structure of the beam in step S3 includes a side wing. During the cutting and dismantling, the side wing is cut along the direction parallel to the bridge span and perpendicular to the bridge span respectively. During the cutting, cutting holes are first drilled at the connection position between the side wing and the main body of the beam. After setting up the wire saw cutting machine, it is cut into small pieces that meet the load of the lifting equipment before being lifted away. Step S3 also includes a pre-cutting step for the beam panel and bottom plate. Specifically, cutting holes are drilled at both ends of the cutting range of the panel and bottom plate. The wire saw cutting machine is set up and cut along the direction perpendicular to the bridge span, so that the panel and bottom plate are separated from the column pier first. This pre-cutting does not affect the normal operation of the prestressed system inside the web of the beam.

[0018] Preferably, the number of tracks in step S4 corresponds to the number of web plates of the beam. The tracks are laid at a position perpendicular to the cutting area and aligned with the bridge deck corresponding to the center of the cutting area. Each track is disconnected and spliced ​​at the beam cutting point. The remote control module can realize the track movement, start and stop control, feed speed adjustment and position locking functions of the wire saw cutting machine. The infrared camera is installed at the bottom of the beam on the non-cutting surface, with the lens facing the cutting surface. It can collect the temperature data of the cutting surface in real time and transmit it to the operating room. It can capture temperature changes exceeding 1°C and perform linear verification on the temperature data change process.

[0019] Preferably, the temporary support device in step S4 includes a modular vehicle equipped with a lifting system and a bracket for temporary support erected at the column pier position. After the modular vehicle drives into the area below the cutting zone, the lifting system lifts and aligns with the beam support position for unloading and moving the cut beam.

[0020] Preferably, during the equipment debugging stage (step S5), the cutting operation hole adopts a large-diameter structure to meet the flexible adjustment requirements of the wire saw position when adjusting the cutting surface. The water flow rate of the water cooling system is quantitatively determined based on the principle of thermal balance. A reasonable value range is set in combination with the working power and energy conversion characteristics of the wire saw cutter to ensure that the water flow rate matches the cutting heat load. At the same time, the water cooling system aims to ensure the recording effect of the infrared monitoring equipment and avoid overheating failure of the cutting equipment, and controls the temperature of the cut surface after cooling within a preset range.

[0021] Preferably, in step S6, the cutting status is identified by fusing the image data collected by the infrared camera with the BIM model. Specifically, the BIM model section with a matching angle is selected and superimposed with the infrared image. The difference in thermal conductivity between concrete and steel strands is used to distinguish between ordinary steel bars and prestressed steel strands by combining the temperature field distribution and characteristic stripe conditions of the superimposed image. When the prestressed steel strand signal is identified, the corresponding avoidance adjustment operation is performed. When cutting the end of the same beam section, multiple wire saw cutting machines equipped with independent control and monitoring units can be deployed simultaneously to ensure that each web of the beam is cut off synchronously through collaborative operation to avoid uneven local stress.

[0022] The present invention has the following beneficial effects:

[0023] 1. By integrating multi-dimensional data such as beam dimensions, reinforcement layout, and concrete grade using BIM technology, a visual model is created and the steel strands are highlighted with key colors. This not only visually displays the internal structure of the beam and the location of the steel strands, but also allows for simulation of the cutting process and extraction of cut surface views within the model, generating precise work guidance documents. Compared to traditional methods of positioning based on drawings and experience, the digital nature of the model enables virtual simulations before construction, reducing rework caused by data discrepancies, lowering the technical threshold for construction personnel, and significantly improving the efficiency of safe cutting location positioning.

[0024] 2. On-site, the wire saw cutting machine is precisely guided by a track, and a real-time monitoring link is established with infrared cameras. The difference in thermal conduction between concrete and steel strands is used to identify structural changes on the cutting surface. Temperature field images are overlaid and compared with the BIM model to achieve remote prediction and intervention in the cutting process. This combination of precise track guidance, real-time infrared monitoring, and remote control completely realizes unmanned operation on the cutting site; at the same time, it forms a closed-loop mechanism for anomaly identification, machine shutdown and adjustment, and rework, significantly reducing the risk of miscutting of steel strands.

[0025] 3. The water flow velocity of the water cooling system is quantitatively calculated through the heat balance equation to ensure that the temperature of the cut surface after cooling meets the requirements of the infrared camera. At the same time, it avoids the wire saw from failing due to overheating, thus achieving an organic unity of cooling effect, equipment protection and monitoring accuracy, which meets the dual requirements of green construction and efficient operation. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a BIM-based prestressed beam cutting construction process according to the present invention.

[0027] Figure 2 This is a construction site layout diagram for a BIM-based prestressed beam cutting construction process according to the present invention.

[0028] Figure 3 This is a schematic diagram of the side cutting operation of a BIM-based prestressed beam cutting construction process according to the present invention.

[0029] Figure 4 This is a schematic diagram of the panel and bottom plate cutting construction operation of a BIM-based prestressed beam cutting construction process according to the present invention.

[0030] Figure 5 This is a schematic diagram of the web cutting operation of a BIM-based prestressed beam cutting construction process according to the present invention.

[0031] In the attached diagram: 1. Beam; 11. Side wing; 12. Panel; 13. Base plate; 14. Web plate; 15. Prestressed steel strand; 2. Column pier; 3. Small crane; 4. Cutting hole; 5. Wire saw; 6. Support frame; 7. Track; 8. Infrared camera; Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0033] Reference Figure 1-5 In a specific embodiment of the present invention, the implementation scenario involves using a modular vehicle combined with a lifting system to disassemble and transport the entire bridge beam. The bridge includes a beam 1 and piers 2. The beam 1 includes side wings 11, a panel 12, a bottom plate 13, and a web 14 containing prestressed steel strands 15. The specific implementation steps of the present invention are as follows:

[0034] Step S1: Data Collection and BIM Modeling: Collect the as-built drawings of the bridge to be demolished on-site. Based on the relevant data on the prestressed system in the as-built drawings, establish BIM models of each span of the bridge, and highlight the location of the prestressed steel strands 15 within beam 1 with color coding. By integrating multi-dimensional engineering data to construct a digital model, the scattered technical parameters are transformed into an intuitive visual carrier. This process can accurately locate the steel strand positions that are difficult to identify in traditional construction. It not only completely solves the industry pain point of the "invisible" prestressed steel strands 15, but also provides a unified digital benchmark for subsequent construction, effectively reducing rework caused by data deviations and significantly improving the planning efficiency and accuracy in the early stages of construction.

[0035] In step S1, the relevant data includes the dimensions of beam 1, the dimensions of column pier 2, the reinforcement layout of beam 1, the location of prestressed steel strands 15, and the concrete grade. The completeness of this data directly determines the accuracy of the BIM model. Complete data support enables the model to realistically reproduce the structural characteristics of the bridge, providing a reliable basis for subsequent cutting surface planning, equipment selection, etc., avoiding construction risks caused by missing data, and ensuring the scientific and safe implementation of the process.

[0036] Step S2: Model Analysis and Cutting Surface Planning: Based on the BIM model created in Step S1, examine and analyze the distribution of prestressed steel strands 15 within beam 1. Divide beam 1 into several small beam segments, treating each prestressed steel strand 15 as a separate and complete prestressing system. Select cutting surfaces at the locations between these segments. Dividing units based on the integrity of the prestressed system maximizes the stability of the steel strands under stress. Avoiding anchorage zones and bends in the cutting process effectively prevents structural damage caused by sudden stress changes in the steel strands during cutting, ensuring the stability of the bridge structure during construction. The cutting surfaces can be numbered, and they should avoid the anchorage zones and bends of the prestressed steel strands 15.

[0037] For concrete sections with large dimensions where there are no prestressed steel strands 15 between small beam segments, the selected cutting surface can further consider the safety distance from the prestressed anchorage end. The safety boundary of the unbonded steel strand is calculated using the quantitative formula Ls=(Δσ×L) / E, combined with the fixed standards for bonded steel strands, forming a differentiated safety control system. This precise quantitative method breaks away from the reliance on experience in traditional construction, making the setting of safety distances more scientific, significantly reducing the risks of steel strand breakage and structural cracking, and drawing a clear safety red line for cutting operations. Specifically, for bonded prestressed steel strands 15, the safety distance is not less than 30cm; for unbonded prestressed steel strands 15, the safety distance is greater than the maximum possible retraction length Ls of the steel strand at the breakage point, where Ls=(Δσ×L) / E, where Δσ is the effective stress of the steel strand in MPa, L is the length from the anchorage end to the cutting point in m, and E is the elastic modulus of the steel strand in MPa.

[0038] Based on the selected cutting surface, the wire saw cutting process is simulated. The 3D and sectional views of the cutting surface are directly extracted from the BIM model and integrated to generate a file containing cutting location numbers. Utilizing the model's visualization capabilities, the construction process is simulated in advance, transforming the abstract cutting plan into a concrete technical document. This facilitates precise execution of tasks by on-site personnel, reduces human error, provides a clear framework for construction handover, and improves the efficiency of workflow coordination.

[0039] The BIM model's images can more intuitively display the internal structure of beam 1 and the location and anchorage of prestressed steel strands 15, thereby better locating safe cutting positions and solving the problem of the steel strands in prestressed beam 1 being "invisible". This visualization method lowers the technical threshold for construction personnel, enabling on-site workers to quickly grasp the core construction points, reduce safety accidents caused by misjudgment of location, and provide double protection for construction safety.

[0040] Step S3: Construction Preparation and Pre-treatment: Lifting equipment (a small crane 3 is used in this embodiment) is deployed on the bridge, and a wire saw cutting machine 5 is set up. The side wing 11 is cut along both the direction parallel to the bridge span and the direction perpendicular to the bridge span. After the side wing 11 is removed, it is lifted off the site by the lifting equipment. For the non-load-bearing side wing 11 structure, a segmented cutting and precise lifting method is adopted. This ensures dismantling efficiency while controlling the construction load, avoiding impact on the main structure of the beam 1. Segmented processing also makes lifting more convenient and reduces the difficulty of operating large equipment. In specific operation, the lifting equipment hook is attached to the side wing 11 structure via a traction rope. Cutting holes 4 are drilled at the connection point between the side wing 11 and the main beam 1. The wire saw cutting machine 5 is set up, and the wire saw is inserted into the cutting holes 4 to cut the side wing 11 into small pieces that meet the load requirements of the lifting equipment, thus completing the lifting and dismantling.

[0041] Side wing 11 does not contain a prestressed system and is an additional part of beam 1. It is often equipped with municipal guardrails and other accessories. Removing this part helps to reduce the self-weight of beam 1. By stripping non-core components, the main load is reduced, which not only improves the stability of subsequent cutting and hoisting processes, but also optimizes the construction site space, creates favorable conditions for the core process, and ensures the balance of the center of gravity of the main body of web 14.

[0042] Furthermore, in step S3, for structures where the prestressed steel strands 15 exist only in the web 14, the face plate 12 and bottom plate 13 of the beam 1 can be pre-cut: cutting holes 4 are drilled at both ends of the cutting range of the face plate 12 and bottom plate 13, a wire saw cutting machine 5 is set up and cut along the direction perpendicular to the bridge span, so that the face plate 12 and bottom plate 13 are separated from the column pier 2 first. Pre-treating the face plate 12 and bottom plate 13, which are less related to the core load, and completing the separation without touching the prestressing system, can avoid hindering the subsequent cutting of the web 14, disperse construction tasks, shorten the overall construction period, and ensure the rationality of the structural stress during construction. This pre-cutting does not affect the normal operation of the prestressing system inside the web 14 and can reduce its interference with the subsequent formal cutting process of the web 14.

[0043] Step S4: Deployment of Support System, Automated Operation, and Monitoring Equipment: The modular vehicle equipped with the lifting system is driven below the cutting surface position described in Step S2. The lifting system is used to lift and align the beam 1 with the support area. Simultaneously, a temporary support bracket 6 is erected at the column pier 2 position to form a temporary support system. This dual support mode of "modular vehicle + bracket" allows for dynamic adjustment of the support strength according to the load on the beam 1. Combined with the guidance of the tracks 7 matching the number of web plates 14, this makes the cutting machine operate more precisely. It not only effectively distributes the weight of the beam 1, preventing sinking or shifting during cutting, but also improves the operating accuracy of the cutting machine, ensuring a flat cut surface and laying the foundation for subsequent splicing or processing. Tracks 7 are installed on the upper surface of beam 1 along the direction parallel to the bridge span. The number of tracks 7 corresponds to the number of web plates 14. Each track 7 is laid at a position perpendicular to the cutting surface and is disconnected and spliced ​​at the cutting point of beam 1. A wire saw cutting machine 5 is slidably installed on the tracks 7 and equipped with a remote control module. This module can realize the movement, start and stop control, feed speed adjustment and position locking functions of the track 7 of the wire saw cutting machine 5. Several infrared cameras 8 are fixedly installed at the bottom of beam 1 on the non-cutting surface, with the lenses facing the cutting surface, to record the cutting surface image in real time and transmit it to the control room. A real-time monitoring link is established through remote equipment, allowing operators to stay away from high-risk work areas, ensuring personnel safety, and enabling timely detection and intervention of cutting abnormalities, thereby improving construction controllability.

[0044] In this embodiment, the infrared camera 8 is selected to capture temperature changes exceeding 1°C, and the wire saw is made of diamond material to ensure cutting efficiency and monitoring accuracy. Through the track 7, remote control module, and infrared camera 8 in step S4, remote control and real-time monitoring of the wire saw cutting process can be realized. This "mechanized operation + remote management" mode breaks the spatial limitations of traditional construction, significantly reduces the safety risks of on-site workers, and improves construction efficiency and accuracy, providing technical support for standardized construction.

[0045] Step S5: Equipment Debugging and Water Cooling Parameter Setting: Drill cutting holes 4 at both ends of the cutting surface selected in Step S2 on beam 1. The hole diameter should be greater than 10cm to facilitate flexible adjustment of the wire saw position during subsequent cutting surface adjustments. Insert the wire saw into the cutting holes 4, and install cooling water pipes on beam 1, aligning them with the cutting surface to form a water cooling system. The reserved large-diameter cutting holes provide redundant space for construction adjustments. Combined with the water cooling system designed based on the thermal balance equation, the cutting temperature and equipment status can be precisely controlled. This not only reduces the construction risks caused by positioning deviations but also prevents the wire saw from being damaged by overheating, extending the equipment's service life. At the same time, it ensures that the monitoring effect of the infrared camera 8 is not affected by temperature.

[0046] The outlet water flow rate of the water cooling system is determined by calculation using the heat balance equation, satisfying Qw=Qr / (ΔTw×Cp×ρ), where Qr is the cutting heat load in kW, ΔTw is the temperature difference between the inlet and outlet cooling water in °C, Cp is the specific heat capacity of water in kJ / (kg·°C), ρ is the density of water in kg / m³, and Qr=W×thermal conversion efficiency (W is the power of the wire saw cutting machine motor 5, and the thermal conversion efficiency is taken as 80%). Based on industry experience, the cooling water flow rate needs to be above 25L / min; therefore, the actual outlet water flow rate ranges from 25L / min to the calculated value Qw. In this embodiment, the ambient temperature during construction is around 30℃, and the temperature of the non-cutting surface concrete is maintained between 30-40℃. The motor power of the wire saw cutting machine is selected as 30kW, resulting in a calculated Qr = 24kW. To ensure cooling effect and monitoring accuracy, the cooling water outlet temperature is set to not exceed 45℃, so ΔTw is taken as 15℃, Cp as 4.186kJ / (kg·℃), and ρ as 1000kg / m³. The final calculated Qw = 38.2L / min, and the on-site cooling water flow rate is taken as 25L / min-38.2L / min. This precise and quantitative flow control method balances cooling effect and energy consumption, avoiding the impact of insufficient cooling on construction quality and preventing water waste, thus achieving a unity of green construction and efficient operation.

[0047] The water cooling system must ensure that the temperature of the cutting surface reaches above 40°C after cooling to guarantee the recording effect of the infrared camera 8 and prevent the wire saw from overheating and failing. After completing the above setup, the equipment should be started in advance to check whether the wire saw cutter 5, the remote control module, and the infrared camera 8 are working properly. A comprehensive pre-debugging process can identify equipment faults in advance, reduce downtime for maintenance during construction, ensure smooth workflow, and improve overall construction efficiency.

[0048] Step S6: Remote Cutting and Real-time Monitoring: After equipment debugging is completed, on-site personnel evacuate, and the operator takes their position in the control room. Using the remote control module, the wire saw cutter 5 is locked in its current position, and the wire saw cutter 5 is started to begin cutting. Simultaneously, the infrared image and BIM model overlay are monitored, allowing for real-time intervention during the cutting process. This operating mode achieves physical isolation between the operator and the work site, using image overlay technology to provide real-time feedback on the cutting status. This fundamentally avoids personnel exposure to high-altitude, dusty, and other high-risk environments, ensuring operational safety. Simultaneously, the real-time intervention mechanism can quickly handle emergencies, effectively reducing construction errors.

[0049] During the cutting operation, the continuous friction between the wire saw and the concrete is the core principle for achieving the cut, and this process generates high temperatures. Infrared camera 8 can accurately record the temperature changes on the cut surface and create a temperature field image. Technicians can then process the data to verify whether the temperature change process follows a linear heating law. It is worth noting that the heat generated by the wire saw cutting mainly comes from the conversion of motor power. This high temperature is conducted through the concrete to the more thermally conductive steel bars, causing the concrete around the steel bars to be preheated. This characteristic provides crucial evidence for structural identification.

[0050] Based on this principle, the difference in thermal conductivity between concrete and steel strands—prestressed steel strands heat up faster and are more sensitive to thermal reactions than concrete—can be utilized to combine infrared monitoring with BIM models, forming a precise structural identification system. This non-contact monitoring method does not interfere with normal cutting operations, yet it can accurately locate the steel strands and reinforcing bars, avoiding structural risks caused by miscutting and significantly improving construction safety and reliability. The specific observation and operation procedures are as follows:

[0051] Step S61: Select a BIM model section at the same angle as the infrared image and overlay it to establish an accurate digital reference benchmark for subsequent temperature field analysis.

[0052] Step S62: After completing the image overlay, the focus is on analyzing the distribution characteristics of the temperature field in the overlay image. The core judgment indicator is the presence of thin, bright stripes. Different temperature field characteristics correspond to drastically different operating conditions and processing methods.

[0053] If the temperature field image is uniform, showing a continuous bright band, and the temperature data changes linearly, this indicates that the wire saw is only acting on the concrete and there is no risk of cutting the prestressed steel strand 15. In this case, the operator only needs to adjust the wire saw feed speed via the remote control module to continue cutting along the predetermined route. This method of quickly determining the working status through temperature field characteristics eliminates the need for machine shutdown for inspection, maintaining construction continuity, improving work efficiency, and ensuring that cutting always takes place within a safe area. From the perspective of heat conduction, in this situation, heat will concentrate at the cutting seam and gradually diffuse to both sides of the concrete. Due to the influence of the crushed stone aggregate inside the concrete, point-like thermal images may appear. This phenomenon further confirms that the wire saw has not contacted the reinforcing steel or the prestressed steel strand 15, and construction can continue as planned.

[0054] If the temperature field image is distorted, with thin, bright stripes appearing near the cut surface, and the stripe brightness increasing as the cutting distance decreases, while the temperature change deviates from a linear pattern, it indicates the presence of reinforcing bars or prestressed steel strands 15 near the cut surface. In this case, the cutting speed must be immediately reduced, and the stripe positions should be precisely matched using the BIM model annotations to clearly distinguish between ordinary reinforcing bars and prestressed steel strands 15. Promptly slowing down and investigating after anomalies are detected, and accurately identifying the structural type through model matching, can effectively prevent damage to prestressed steel strands 15 or reinforcing bars due to blind cutting, preventing structural collapse and ensuring construction safety and project quality. The direction indicated by the thin, bright stripes indicates the actual location of the ordinary reinforcing bars or prestressed steel strands 15.

[0055] Step S63: Based on the above analysis results, perform corresponding operations on the wire saw cutting machine 5 through the remote control module to form a closed-loop control: If it is determined that the thin, bright stripe corresponds to the prestressed steel strand 15, the wire saw cutting machine 5 must first be stopped. After releasing the wire saw, adjust the position of the cutting machine through the remote control module so that the wire saw moves within the cutting hole 4 to a safe position that avoids the prestressed steel strand 15 and surrounding reinforcing bars, and then restart the equipment; if adjusting the position still cannot avoid the steel strand, all equipment operations on site must be stopped, and the cutting area must be replanned in step S2, a new cutting hole 4 must be drilled, and the equipment debugging and water cooling parameter settings must be completed according to the requirements of step S5 before restarting the cutting process. This closed-loop control mechanism of "identifying problems - precise adjustment - rework" can minimize the losses caused by construction errors, ensure that every step of cutting meets safety standards, and guarantee the stability of project quality.

[0056] To improve efficiency and ensure structural safety, multiple wire saw cutting machines 5 can be deployed simultaneously for the end cutting of the same beam 1 section, depending on the number of cutting areas. Each cutting machine requires an independent remote control module and dedicated monitoring personnel. Synchronous cutting operations are achieved through collaborative scheduling, ensuring that all webs 14 of beam 1 are removed simultaneously. This multi-equipment collaborative operation mode, through dedicated management, ensures operational synchronization, significantly shortening cutting time and improving construction efficiency. It also fundamentally avoids construction risks such as beam 1 deformation and structural damage caused by uneven local stress, thus ensuring structural integrity.

[0057] The implementation of the remote-controlled cutting process achieved dual core values: on the one hand, it ensured the full monitoring of the beam 1 cutting process, enabling timely prediction and adjustment of the cutting surface condition, effectively avoiding the risk of concrete collapse caused by cutting the prestressed steel strand 15 or accidentally damaging the reinforcing steel; on the other hand, it completely realized unmanned operation at the cutting site, so that even in the extreme case of the prestressed steel strand 15 being accidentally cut, resulting in concrete collapse, personnel casualties could be completely avoided, greatly improving construction safety.

[0058] Step S7: Finishing of Cutting Unit and Equipment Transfer: After cutting is completed, the wire saw cutting machine 5 is stopped via remote control module. Workers enter the construction site to remove the wire saw and move the wire saw cutting machine 5 along track 7 to the vicinity of the next cutting surface. The equipment debugging and water cooling parameter setting in step S5 are repeated, along with subsequent steps. For the cut beam 1 unit, it is unloaded from the column pier 2 using the jacking system positioned at the bottom of the beam and the modular vehicle, and then transported outside the construction site for further processing. The standardized post-processing procedure achieves efficient connection between equipment transfer and beam 1 transport, which not only reduces waiting time between processes and improves construction continuity, but also protects beam 1 unit and surrounding structures through stable transport, avoiding collision damage, while optimizing the construction site environment and facilitating subsequent processes.

[0059] Through the complete construction steps S1 to S7 described above, this invention successfully solves multiple technical challenges in the traditional prestressed beam 1 cutting construction: First, by utilizing BIM modeling and visual annotation, the core pain point of the prestressed steel strands 15 being "invisible and difficult to locate" is completely resolved, providing precise data support for the cutting operation; Second, by scientifically dividing the cutting units and quantifying safety distance standards, the risk of structural collapse caused by instability of the prestressed system and breakage of steel strands during the cutting process is effectively avoided; Third, the safety hazards of close-range operation by personnel and the problems of low cutting accuracy and poor efficiency in traditional construction are overcome. At the same time, this process brings significant beneficial effects: the integrated application of BIM technology with infrared monitoring and remote control realizes the digitalization, visualization, and unmanned operation of the cutting process, greatly improving construction safety; standardized process flow and multi-equipment collaborative operation mode effectively shorten the construction period and reduce human error; the pre-removal of non-core components and the construction of a precise support system ensure the structural integrity of beam 1, reduce construction losses, and provide an efficient, safe, and reliable technical solution for the cutting construction of prestressed beam 1.

[0060] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A BIM-based prestressed beam cutting construction process, characterized in that, Includes the following steps: Step S1: Data collection and BIM modeling: Obtain engineering drawings of the structure containing the prestressed beam to be demolished, extract the prestressing system data, construct the BIM model of the structure and mark the position of the prestressed steel strands in the beam; Step S2: Model Analysis and Cutting Surface Planning: Based on the BIM model, analyze the distribution pattern of prestressed steel strands, divide the beam into cutting units in combination with the integrity of the prestressed system, and plan the cutting area between units; Step S3: Construction preparation and pretreatment: Deploy lifting equipment and wire saw cutting machine, cut and dismantle non-load-bearing auxiliary structures of the beam and transfer them off-site by lifting equipment; Step S4: Deployment of support system, automated operation and monitoring equipment: A temporary support device is set up below the cutting area, a track is erected on the beam surface and a wire saw cutting machine with a remote control module is installed, and an infrared camera for real-time acquisition of images of the cutting surface is installed at the same time; the number of tracks corresponds to the number of web plates of the beam, the tracks are laid at a position perpendicular to the cutting area and aligned with the bridge deck corresponding to the center of the cutting area, and each track is disconnected and spliced ​​at the beam cutting point; The remote control module can realize the track movement, start and stop control, feed speed adjustment and position locking functions of the wire saw cutting machine; the infrared camera is installed at the bottom of the beam on the non-cutting surface, with the lens facing the cutting surface, and can collect the cutting surface temperature data in real time and transmit it to the operating room. It can capture temperature changes of more than 1°C and perform linear verification on the temperature data change process. Step S5: Equipment debugging and water cooling parameter setting: Pre-set the cutting operation holes in the cutting area and assemble the cutting components. Set up the water cooling system aligned with the cutting area and adjust the water flow speed to ensure the function of the infrared camera; start the equipment and check the operating status. Step S6: Remote Cutting and Real-time Monitoring: After the construction personnel have evacuated, the cutting of the beam cutting units defined in Step S2 is initiated through the remote control module. The image data collected by the infrared camera is fused with the BIM model to dynamically monitor the cutting process. If steel reinforcement is detected, an alarm is triggered, and the cutting parameters or path are adjusted based on the alarm and monitoring results. Specifically, the BIM model section with a matching angle is superimposed with the infrared image. The difference in thermal conductivity between concrete and steel strands is used to distinguish between ordinary steel reinforcement and prestressed steel strands by combining the temperature field distribution and characteristic stripe patterns of the superimposed image. When a prestressed steel strand signal is detected, the corresponding avoidance adjustment operation is executed. When cutting the end of the same beam section, multiple wire saw cutting machines with independent control and monitoring units can be deployed simultaneously to ensure that each web of the beam is cut off synchronously through collaborative operation to avoid uneven local stress. Step S7: Cutting unit completion and equipment transfer: After cutting is completed, the equipment is shut down via remote control module, the operators dismantle the cutting components and transfer the equipment to the corresponding area of ​​the next cutting unit; the beam unit is separated and transferred to the designated area using temporary support devices.

2. The BIM-based prestressed beam cutting construction process according to claim 1, characterized in that, The bridge containing the prestressed beam includes the beam and the pier. The beam includes the side wings, the panel, the bottom plate, and the web containing the prestressed steel strands. The prestressed system data in step S1 includes the beam dimensions, the pier dimensions, the reinforcement layout of the beam, the location of the prestressed steel strands, and the concrete grade. When modeling with BIM, the location of the prestressed steel strands in the beam is highlighted with color.

3. The BIM-based prestressed beam cutting construction process according to claim 1, characterized in that, In step S2, the beam cutting unit is divided based on the integrity of the prestressed system. Specifically, the beam is divided into several small beam segments according to the principle that each prestressed steel strand is an independent and complete prestressed system. The cutting area planning needs to avoid the prestressed steel strand anchorage area and the bent-up section, and meet the safety distance requirements with the prestressed anchorage end. Based on the planned cutting surface, the wire saw cutting process can be simulated through the BIM model, and the three-dimensional view and sectional view of the cutting surface can be extracted and integrated to generate a file containing the cutting position number.

4. The BIM-based prestressed beam cutting construction process according to claim 3, characterized in that, The specific safety distance is as follows: for bonded prestressed steel strands, the safety distance is not less than 30cm; for unbonded prestressed steel strands, the safety distance is greater than the maximum possible retraction length Ls of the steel strand at the fracture point, where Ls=(Δσ×L) / E, Δσ is the effective stress of the steel strand in MPa, L is the length from the anchoring end to the cutting point in m, and E is the elastic modulus of the steel strand in MPa.

5. The BIM-based prestressed beam cutting construction process according to claim 1, characterized in that, The non-load-bearing auxiliary structure of the beam in step S3 includes side wings. During the cutting and dismantling, the side wings are cut along the direction parallel to the bridge span and perpendicular to the bridge span respectively. During the cutting, cutting holes are first drilled at the connection position between the side wings and the main body of the beam. After setting up the wire saw cutting machine, it is cut into small pieces that meet the load of the lifting equipment before being lifted away. Step S3 also includes a pre-cutting step for the beam panel and bottom plate. Specifically, cutting holes are drilled at both ends of the cutting range of the panel and bottom plate. The wire saw cutting machine is set up and cut along the direction perpendicular to the bridge span, so that the panel and bottom plate are separated from the column pier first. The pre-cutting does not affect the normal operation of the prestressed system inside the web of the beam.

6. The BIM-based prestressed beam cutting construction process according to claim 1, characterized in that, The temporary support device mentioned in step S4 includes a modular vehicle equipped with a lifting system and a temporary support bracket erected at the column pier position. After the modular vehicle drives into the area below the cutting zone, the lifting system lifts and aligns with the beam support position for unloading and moving the beam after cutting.

7. The BIM-based prestressed beam cutting construction process according to claim 1, characterized in that, In step S5, the cutting hole adopts a large-diameter structure to meet the flexible adjustment requirements of the wire saw position when adjusting the cutting surface. The water flow rate of the water cooling system is quantitatively determined based on the principle of thermal balance. A reasonable value range is set in combination with the working power and energy conversion characteristics of the wire saw cutter to ensure that the water flow rate matches the cutting heat load. At the same time, the water cooling system aims to ensure the recording effect of the infrared monitoring equipment and avoid overheating failure of the cutting equipment, and controls the temperature of the cut surface after cooling within a preset range.

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