Construction method for measuring and adjusting pre-camber of precast T-beam

Abstract

The application discloses a construction method for precise measurement and adjustment of pre-camber of a prefabricated T beam. The special device in the method comprises an adjusting device, a measuring device and a counterforce frame device, wherein the counterforce frame device is used in pairs with a beam support and a bearing ground beam to provide hydraulic downward pressure; the adjusting device controls lifting in the height direction by manual, electric or hydraulic mode to adjust the pre-camber of the prefabricated T beam; the measuring device measures the pre-camber of the prefabricated T beam by a laser displacement sensor, and the laser displacement sensor has a moving space in the length direction of the beam; the adjusting device and the measuring device are installed on the bearing ground beam with a spacing, and the number is multiple; through cooperation of the measuring device and the adjusting device, the pre-camber of the whole prefabricated T beam is adjusted, reasonable linear shape of the prefabricated T beam is obtained, the convenience and efficiency of adjustment are improved, and the labor intensity is obviously reduced.

Description

Technical Field

[0001] This invention relates to a construction method for measuring and adjusting the pre-camber of precast T-beams, belonging to the field of bridge construction technology. Background Technology

[0002] Pre-camber is a correction amount reserved during construction or manufacturing to offset the deflection of beams, arches, trusses, and other structures under load. In the field of bridges, bridge deflection is caused by two main factors: permanent load deflection and variable load deflection. Permanent load deflection includes the structural self-weight, the gravity of the bridge deck pavement and ancillary equipment, prestressing, concrete creep, and shrinkage. These are permanent and their deflection is related to the duration of the load, and can be divided into short-term and long-term deflection. Permanent load deflection can be offset by a pre-set reverse deflection, also known as pre-camber, during construction, ensuring the completed bridge achieves ideal linearity.

[0003] The pre-camber of prestressed concrete bridges is typically set as follows: When the long-term anti-camber value generated by prestressing is greater than the long-term deflection calculated based on the short-term load effect combination, pre-camber is not required; when the long-term anti-camber value of prestressing is less than the long-term deflection calculated based on the short-term load effect combination, pre-camber should be set, and its value should be based on the difference between the deflection of that load and the long-term anti-camber value of the prestressing. For bridges located on vertical curves, the pre-camber value should be appropriately increased depending on the convexity or concavity of the vertical curve, so that the linearity after completion closely matches the vertical curve. Although variable load deflection is temporary, its magnitude gradually changes with the movement of the variable load. The deflection reaches its maximum value at the most unfavorable load position and disappears once the vehicle leaves the bridge deck. Therefore, variable load deflection needs to be verified in bridge design to reflect the stiffness characteristics of the structure. Bridge pre-camber is a very important indicator in bridge construction, and there are strict requirements for its measurement.

[0004] Existing methods for measuring the pre-camber of bridge beams primarily involve placing the tensioned precast T-beam horizontally on the top surface of an I-beam, and measuring the height of the bottom of the T-beam at multiple points relative to the top surface of the I-beam using a measuring tape. This multi-point measurement constructs a complete model of the bridge's bottom surface. This method is cumbersome, and the accuracy of the measurement results varies with the frequency of operation. The fewer the measurement points, the higher the randomness of the results, leading to repetitive and tedious steps. Furthermore, it cannot accurately construct a complete model of the bridge's bottom camber, resulting in low practicality. Existing methods for adjusting the pre-camber of bridge beams mainly involve adding shims between the bottom of the precast T-beam and the top surface of the I-beam. The reaction force exerted by the shims on the bottom of the precast T-beam adjusts the pre-camber. However, this method requires lifting the precast T-beam and manually adding or removing shims, making it overly cumbersome, labor-intensive, and mechanically demanding. The adjustment accuracy is also uncontrollable, thus affecting the final bridge alignment. Furthermore, the existing measurement method is a static measurement, which cannot simulate loading on the precast T-beams during the measurement process, especially dynamic loading, such as periodic loading.

[0005] In view of this, this paper studies and improves upon existing problems, and provides a precast T-beam bottom pre-camber construction method that integrates measurement, dynamic loading, and camber adjustment. This method aims to solve the problems of cumbersome, inefficient, and inaccurate measurement and adjustment operations, and to improve the practical value of the technology. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a construction method for accurately measuring and adjusting the pre-camber of precast T-beams. This method eliminates the need for manual measurement of the height between the bottom of the precast T-beam and the horizontal plane of the I-beam, and accurately reflects the pre-camber value at every point on the bottom of the precast T-beam. This invention improves upon traditional methods for adjusting the pre-camber of precast T-beams, eliminating the need to lift the precast T-beam to add or remove shims during adjustment. This enhances the efficiency and convenience of the pre-camber adjustment method, ensuring the accuracy and reliability of the experiment.

[0007] The technical solution of the present invention is as follows:

[0008] A construction method for measuring and adjusting the pre-camber of a precast T-beam, comprising a specialized device including an adjustment device, a measuring device, and a reaction frame device. The reaction frame device is used in conjunction with the beam support and the load-bearing beam to provide hydraulic downward pressure. The adjustment device is controlled manually, electrically, or hydraulically to adjust the pre-camber of the precast T-beam. The measuring device measures the pre-camber of the precast T-beam using a laser displacement sensor, which has a movement range along the beam's length. Multiple adjustment and measuring devices are installed alternately on the load-bearing beam.

[0009] The steps are as follows:

[0010] Step 1: Place both ends of the precast T-beam on two beam supports. The middle and central position of the top surface of the precast T-beam is the distribution beam. Spread fine sand on the bottom surface of the distribution beam and the top of the precast T-beam. The distribution beam abuts against the precast T-beam under the action of a hydraulic jack to form a loading point.

[0011] Step 2: Adjust the pivot joint structure in the measuring device so that the sensing surface of the laser displacement sensor is perpendicular to the bottom of the precast T-beam. After confirmation, tighten the pivot joint structure and fix the laser displacement sensor. Start the laser displacement sensor, zero it, and select recording. Then, push the measuring device at a constant speed, causing the laser displacement sensor to move in a uniform linear motion along the length of the T-beam. The laser displacement sensor emits laser light towards the bottom of the precast T-beam and converts the reflected laser light into electrical signals in the laser displacement sensor. The collected electrical signals are converted into stable linear outputs by the built-in processor of the laser displacement sensor, generating a function curve corresponding to the pre-camber, which is displayed on the screen of the laser displacement sensor. Then, repeat the above operation for each measuring device one by one. Finally, summarize the pre-camber data of the precast T-beams measured for all segments, fit the interruption position of the adjusting device, complete the measurement operation of the precast T-beam pre-camber, and form a complete function curve along the length of the T-beam.

[0012] Based on the above measurement results, if the arch height H1 of the upper part of the T-beam span is greater than the design value H2 of the pre-camber, then proceed to step three.

[0013] If the arch height H1 of the upper part of the T-beam mid-span is less than the design value H2 of the pre-camber, then step four is required;

[0014] Step 3: Beam straightening. Slide the laser displacement sensor in the middle section of the precast T-beam along the guide rail to the bottom mid-span position of the precast T-beam and record the reading of the laser displacement sensor at this time. Then, start the hydraulic jack on the reaction frame device to apply pressure to the distribution beam. As the pressure F of the hydraulic jack on the mid-span of the precast T-beam increases, the reading on the laser displacement sensor will decrease accordingly. When the reading on the laser displacement sensor is less than or equal to the difference between H1 and H2, stop loading. After the reading stabilizes, the hydraulic jack maintains pressure. After N hours, the pressure of the hydraulic jack is slowly unloaded. After unloading, the precast T-beam rebounds slightly, and the precamber after rebound meets the design value requirements.

[0015] Step 4: Beam straightening. Move the laser displacement sensor along the guide rail to the position where the pre-camber needs to be adjusted and record the initial reading. Then, raise the height of the adjustment device, which generates an upward thrust F1 on the precast T-beam. While adjusting the adjustment device, observe the reading on the laser displacement sensor. When the displayed reading is H2, stop rotating. After the reading stabilizes, maintain this state for N hours. Then, adjust and control the adjustment device to lower, and observe the reading on the laser displacement sensor. If the reading after unloading remains at H2, the pre-camber of the precast T-beam meets the design requirements. If the reading after unloading is less than H2, it indicates that the bottom plate of the precast T-beam has rebounded. After rebound, use the secondary tensioning process to adjust the pre-camber of the precast T-beam. Install the anchor plate, anchorage, and connector according to the corresponding specifications, and start the tensioning machine. Observe the laser displacement sensor at this time. When the reading of the laser displacement sensor meets the design requirement H2, stop loading, record the tension stress corresponding to this program, and maintain this load intensity for N minutes. At this time, the pre-camber of the precast T-beam meets the design requirements, and stop the secondary tensioning.

[0016] In a more detailed configuration, the reaction frame device includes two steel columns perpendicular to the ground, arranged on the left and right sides of the space where the precast T-beam is placed. A crossbeam is set between the two steel columns, and the lower ends of the steel columns are fixed. Two beam supports are set in conjunction with the reaction frame device. A hydraulic jack is vertically installed on the crossbeam, with the piston of the hydraulic jack facing downward and a distribution beam fixedly installed on the piston.

[0017] In a more detailed configuration, the load-bearing ground beam is arranged along the length of the precast T-beam and is located in the space between the supports at both ends.

[0018] In a more detailed configuration, the adjustment device includes a base, a pad, a parallelogram lifting rod, a rotating rod, and a rotating wheel. The lower lifting rod is connected to the base, and a threaded rotating rod is inserted near the center of the hinge point between the lower and upper lifting rods. The pad is fixed to the top of the upper lifting rod, and a rotating wheel is welded to one end of the rotating rod.

[0019] For a more detailed configuration, the adjustment device is an electrically driven or manually driven scissor jack or a hydraulic jack.

[0020] In a more detailed configuration, the measuring device includes a sliding guide rail, on which a slider is movably connected. A plate is fixed above the slider, and the plate is provided with a slot and a handle. A vertical rod is fixed in the slot, and the top of the vertical rod is connected to a mounting plate via a pivot joint structure. A laser displacement sensor is fixedly mounted on the mounting plate.

[0021] A more detailed configuration is provided, with the number of measuring and adjusting devices increased or decreased according to the specifications of the precast T-beams.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention provides a construction method for measuring and adjusting the pre-camber of precast T-beams. The pre-camber of the precast T-beams can be accurately measured in micrometers using a laser displacement sensor, which greatly improves the measurement accuracy and reduces the errors caused by traditional measurement with a measuring tape. At the same time, the measured pre-camber value can be linearly output to the screen and converted into a function graph, avoiding the need for traditional manual drawing and greatly improving the efficiency of the test.

[0024] 2. The present invention is equipped with an adjustable pre-camber lifting device, which can be controlled by rotating wheels. Multiple lifting devices can work together to adjust the pre-camber of the entire precast T-beam, so as to obtain a rational precast T-beam shape. There is no need to repeatedly lift the precast T-beam to add or remove shims, which greatly improves the convenience and efficiency of adjustment and significantly reduces labor intensity.

[0025] 3. The measuring component of the present invention is installed next to the adjusting component, and the pre-camber can be adjusted according to the measurement results. This allows for coordinated measurement and adjustment, thereby achieving precise adjustment of the pre-camber.

[0026] 4. The present invention is equipped with a reaction frame device, which can simulate the dynamic loading process through hydraulic jacks. This can ensure the stability of the precast T-beam during the adjustment of the pre-camber and prevent the precast T-beam from overturning during the adjustment process, thus ensuring the safety of the test personnel. Attached image description:

[0027] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0028] Figure 2 This is the front view of the present invention.

[0029] Figure 3 This is a side view of the present invention.

[0030] Figure 4 This is a top view of the present invention.

[0031] Figure 5 This is a front view of the adjusting device of the present invention.

[0032] Figure 6 This is a structural diagram of the regulating device of the present invention.

[0033] Figure 7 This is a front view of the measuring device of the present invention.

[0034] Figure 8 This is a side view of the measuring device of the present invention.

[0035] Figure 9 This is a structural diagram of the measuring device of the present invention.

[0036] Figure 10 This is a structural diagram of the measuring device of the present invention from another perspective.

[0037] in:

[0038] 00T beam,

[0039] 10 Adjustment device, 11 Base, 12 Pad, 13 Parallelogram lifting rod, 14 Rotating rod, 15 Rotating wheel.

[0040] 20 Measuring device, 21 Sliding guide rail, 22 Slider, 23 Flat plate, 231 Slot, 232 Hand grip, 233 Vertical rod, 24 Pivot joint structure, 25 Mounting plate, 26 Laser displacement sensor

[0041] 30. Reaction frame device; 31. Steel column; 32. Crossbeam; 33. Beam support; 34. Hydraulic jack; 35. Distribution beam.

[0042] 40 load-bearing ground beam. Detailed Implementation

[0043] To facilitate understanding by those skilled in the art, the present invention will be further described below through embodiments and in conjunction with the accompanying drawings, but is not limited thereto.

[0044] Reference Figures 1 to 10 As shown, a construction method for measuring and adjusting the pre-camber of precast T-beams is introduced. This method is a specialized method, and the specialized equipment involved in the method consists of an adjustment device, a measuring device, and a reaction frame device.

[0045] The adjusting device 10 controls the lifting and lowering in the height direction by manual, electric or hydraulic transmission, and is used to adjust the pre-camber of the T-beam.

[0046] The measuring device 20 has the function of accurately measuring the pre-camber of the precast T-beam through a laser displacement sensor, and the laser displacement sensor has the function of moving in the longitudinal direction (length direction) of the beam.

[0047] The reaction frame device 30 is used in conjunction with the beam support to provide hydraulic downward pressure, which ensures the stability of the precast T-beam and has the function of adjusting the precamber through hydraulic jacks.

[0048] The following is in conjunction with the instruction manual. Figure 1 To be continued Figure 5 The construction process and special equipment of this embodiment are described in detail.

[0049] First, let's introduce the reaction frame device 30. This device includes two steel columns 31 perpendicular to the ground. These two columns 31 are arranged on either side of the space where the T-beam to be constructed will be placed. I-beams are preferred for these two columns due to their superior pull-out resistance. A crossbeam 32, composed of two channel steels welded to the highest point of the two columns 31, is erected at this height. The crossbeam 32 and the two columns form an H-shaped gantry frame. The lower ends of the steel columns 31 are fixed to the foundation using ground anchors. Two beam supports 33 are installed in conjunction with the reaction frame device. These supports can be either reinforced concrete or steel structures, providing high rigidity. A hydraulic jack 34 is vertically mounted on the crossbeam 32 of the reaction frame device. The piston of the hydraulic jack faces downwards, meaning it extends and retracts downwards. A distribution beam 35 is fixedly mounted on the piston. The distribution beam 35 is a rectangular steel section composed of four sides (top, bottom, left, and right). This steel section is horizontally positioned and acts on the upper end face of the T-beam 00, which is located in the center of the T-beam 00. External loads are applied via the hydraulic jack.

[0050] The loading process of the hydraulic jack described above should ensure that the loading force is increased slowly and gradually.

[0051] In conjunction with the aforementioned reaction frame device 30, there is also an I-beam bearing beam 40. The upper surface of the bearing beam is leveled to accommodate adjustment and measuring devices. The I-beam bearing beam 40 is arranged along the T-beam direction and is located in the space between the supports at both ends.

[0052] The above constitutes the external load loading structure.

[0053] Adjustment device 10, reference Figure 2 The device employs a manual scissor jack structure, comprising a base 11, a pad 12, parallelogram-shaped lifting rods 13 (upper and lower), a rotating rod 14, and a rotating wheel 15. The base 11 is connected to the horizontally symmetrical lower and upper lifting rods. A threaded rotating rod 14 is inserted near the hinge point of the lower and upper lifting rods. The pad 12 is fixed to the top of the upper lifting rod. A rotating wheel 15 is welded to one end of the rotating rod 14. The height of the device can be easily adjusted by operating the rotating wheel. The loading force of a single adjustment device is not less than 10T. Specifically, multiple adjustment devices 10 are installed between the load-bearing beam 40 and the T-beam 00, evenly spaced and symmetrically distributed along the length of the T-beam about its center.

[0054] The aforementioned adjustment device 10 can be explicitly replaced by an electrically driven scissor jack, a hydraulic jack, or other devices that can provide vertical lifting force.

[0055] In this embodiment, five adjustment devices 10 are provided along the length of the beam. The space between two adjustment devices is discontinuous and used to install measuring devices, so there are also multiple measuring devices.

[0056] The measuring device 20 is used to measure the bottom pre-camber of the T-beam. Specifically, the measuring device 20 includes a sliding guide rail 21, the length direction of which is consistent with the length direction of the T-beam, that is, the sliding guide rail provides the direction of sliding. A slider 22 is movably connected to the sliding guide rail 21 via small rollers. The slider is paired with the sliding guide rail 21 and can be a linear sliding guide rail assembly, which has high precision and smooth sliding.

[0057] A T-shaped plate 23 is fixedly installed above the slider 22. This plate has a slot 231 and a handle 232, the handle being a U-shaped structure that is inverted and snapped onto the plate. The slider can be moved by holding the handle with one hand. The slot 231 is a circular slot used to fix the upright 233, and is secured with screws. The top of the upright 233 is connected to a mounting plate 25 via a pivot joint structure 24. A laser displacement sensor 26 is fixedly installed on this mounting plate, allowing for rotation within ±45 degrees to adjust the angle of the laser displacement sensor.

[0058] The number of measuring devices and adjusting devices can be increased or decreased according to the specifications of the precast T-beams. The aforementioned adjusting devices and measuring devices are set at intervals.

[0059] The method for constructing T-beams using the aforementioned device, employing a post-tensioning method, comprises the following steps:

[0060] Step one: First, the user needs to fix the precast T-beam. Specifically, place both ends of the precast T-beam 00 stably on two beam supports 33 on the ground. The top of the beam support should be approximately 50cm above the ground. The distance between the two supports can be adjusted according to the length of the precast T-beam of different specifications, but it should be ensured that the two supports are symmetrical about the loading point. At the mid-span and center position of the top surface of the precast T-beam 00, a double-I-beam serves as a distribution beam 35. The distribution beam has dimensions of approximately 80cm × 40cm × 20cm and is used for applying downward pressure. Simultaneously, a layer of fine sand approximately 1cm thick is laid on the area where the bottom surface of the distribution beam contacts the top plate of the precast T-beam. This is to prevent damage to the precast T-beam during the adjustment of the pre-camber. The middle of the distribution beam 35 should be tightly attached to the hydraulic jack of the reaction frame.

[0061] Step two: After the user has fixed the precast T-beam, ensuring its stability, rotate the pivot joint structure located at the upright in the measuring device 20 so that the sensing surface of the laser displacement sensor 26 is perpendicular to the bottom of the precast T-beam. After confirmation, tighten the pivot joint structure and fix the laser displacement sensor. Then, start the laser displacement sensor 26, zero it, and select recording. Next, push the handle in the measuring assembly at a constant speed to make the slider move linearly along the sliding guide rail at a constant speed. This causes the upright to drive the laser displacement sensor 26 to move linearly at a constant speed. During the measurement process, the laser displacement sensor emits a laser beam towards the bottom of the precast T-beam. The emitted laser beam passes through every point on the bottom of the precast T-beam, and the laser beam reflected back from each point is converted into an electrical signal by the laser displacement sensor. The collected electrical signal is converted into a stable linear output by the built-in processor of the laser displacement sensor, generating a function curve corresponding to the pre-camber, which is displayed on the screen of the laser displacement sensor. During the measurement process, it is important to note that the handle should not be pushed too quickly, so as to ensure that the laser displacement sensor accurately and stably receives the emitted laser beam, thereby reducing measurement errors and improving adjustment accuracy. At this point, the pre-camber of the precast T-beam segment is measured. Then, the above operation is repeated for each measuring device to measure the pre-camber of the precast T-beam at other segments. Finally, the pre-camber data of the precast T-beams measured for all segments are summarized, and the interruption position of the adjustment device is fitted to complete the measurement operation of the precast T-beam pre-camber and generate a complete function curve along the length of the T-beam.

[0062] Based on the above measurement results, if the arch height H1 at the upper part of the T-beam span is greater than the design value H2 of the pre-camber, then step three needs to be performed.

[0063] The reason why the camber height H1 at the upper part of the mid-span of the beam is greater than the design value H2 of the pre-camber is that during the actual measurement of the pre-camber, as the age of the poured concrete gradually increases, the precast T-beam will gradually camber upward at the mid-span. According to the data results of multiple measurements, the shrinkage and creep of the concrete structure during the tensioning of the prestressed steel strands will cause the upper part of the mid-span of the beam to camber by about 2.1cm, while the design value of the pre-camber is 1cm, so the pre-camber at the mid-span needs to be reduced by about 1cm.

[0064] If the arch height H1 at the upper part of the mid-span of the T-beam is less than the design value H2 of the pre-camber, then step four is required.

[0065] The reason why the camber height H1 at the upper part of the T-beam mid-span is less than the design value H2 of the pre-camber is that sometimes due to insufficient tension, the pre-camber at the mid-span of the precast T-beam will be less than 1cm, which will have a significant impact on the bearing capacity of the precast T-beam. It is necessary to increase the pre-camber at the mid-span of the precast T-beam to meet the design requirements.

[0066] Step 3: Beam straightening. Slide the laser displacement sensor in the middle section along the guide rail to the bottom mid-span position of the precast T-beam and record the reading of the laser displacement sensor at this time. Then, start the hydraulic jack on the reaction frame to apply pressure to the distribution beam. The distribution beam transmits the pressure to the mid-span of the precast T-beam, loading a vertical downward force F onto the T-beam. As the pressure F of the hydraulic jack on the mid-span of the precast T-beam increases, the reading on the laser displacement sensor will decrease accordingly. When the reading on the laser displacement sensor is 1 cm less than the pre-camber design value, stop loading. After the reading stabilizes, maintain the pressure on the hydraulic jack for the designed time N hours. After N hours, slowly unload the pressure from the hydraulic jack. After unloading, the precast T-beam will rebound by about 1 cm. At this time, the pre-camber of the upper part of the mid-span of the precast T-beam is about 1 cm, which meets the design requirements.

[0067] Step 4: Beam straightening. Move the laser displacement sensor along the guide rail to the position where the pre-camber needs to be adjusted and record the initial reading. Then, rotate the rotating wheel in the adjustment device clockwise. The rotating wheel will drive the threaded rotating rod to rotate. As the rotating wheel rotates, the vertically symmetrical upper and lower lifting rods will move backward along the threaded rotating rod, thereby driving the support base to rise. The upward thrust F1 exerted by the support base on the precast T-beam will generate an upward bending moment in the T-beam. While rotating the rotating wheel in the adjustment device, observe the reading on the laser displacement sensor. When the displayed reading is 1cm, stop rotating. After the reading stabilizes, maintain this state for N hours, then slowly rotate counterclockwise. Rotate the rotating wheel in the adjustment device to slowly lower the support base. Observe the reading displayed on the laser displacement sensor. If the reading remains at 1cm after unloading, the pre-camber of the precast T-beam meets the design requirements. If the reading is less than 1cm after unloading, it indicates that the bottom plate of the precast T-beam has rebounded. In this case, a secondary tensioning process is needed to adjust the pre-camber of the precast T-beam. After installing the anchor plates, anchors, and connectors according to the relevant specifications, start the tensioning machine. Observe the laser displacement sensor again. When the reading of the laser displacement sensor meets the design requirements, for example, the pre-camber of the upper part of the mid-span of the precast T-beam is about 1cm, it meets the design value requirement. Stop loading, record the stress σ corresponding to this time, and maintain this load intensity for 2 minutes. At this point, the pre-camber of the precast T-beam meets the design requirements, and the secondary tensioning can be stopped.

[0068] In summary, the hydraulic jacks gradually load and unload, and the hydraulic jacks of the reaction frame can lower the pre-camber of the precast T-beam. The adjustment device can raise the pre-camber of the precast T-beam by lifting the base plate. By comparing the height displayed on the laser displacement sensor next to it, the three can work together to achieve the effect of precise adjustment of the pre-camber.

[0069] This invention uses a laser displacement sensor to accurately measure the pre-camber of precast T-beams in micrometers, greatly improving measurement accuracy and reducing errors caused by traditional tape measure methods. Furthermore, the measured pre-camber value can be linearly output to a function graph on the screen, avoiding manual drawing and significantly improving experimental efficiency.

[0070] This invention features an adjustable pre-camber lifting device, which can be controlled by rotating wheels. Multiple lifting devices can work together to adjust the pre-camber of the entire precast T-beam, resulting in a rational precast T-beam profile. This eliminates the need to repeatedly lift the precast T-beam to add or remove shims, greatly improving the convenience and efficiency of adjustment and significantly reducing labor intensity.

[0071] The measuring component of this invention is installed next to the adjusting component, and the pre-camber can be adjusted according to the measurement results. This allows for coordinated measurement and adjustment, achieving precise adjustment of the pre-camber.

[0072] By gradually loading the beam with hydraulic jacks, the laser displacement sensor can dynamically record the changes in the beam's camber during the dynamic loading process, thereby recording the data and guiding the beam's correction.

[0073] The embodiments described above are merely illustrative of the implementation of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements to the present invention by those skilled in the art should fall within the protection scope defined in the claims of the present invention.

Claims

1. A construction method for measuring and adjusting the pre-camber of precast T-beams, wherein the specialized equipment in the method includes an adjustment device, a measuring device, and a reaction frame device, wherein, The reaction frame device is used in conjunction with the beam support and the load-bearing beam to provide hydraulic downward pressure; the adjustment device controls the lifting and lowering in the height direction manually, electrically, or hydraulically to adjust the pre-camber of the precast T-beam; the measuring device measures the pre-camber of the precast T-beam using a laser displacement sensor, and the laser displacement sensor has a movement space in the length direction of the beam; the adjustment device and the measuring device are installed alternately on the load-bearing beam, and there are multiple such devices. The steps are as follows: Step 1: Place both ends of the precast T-beam on two beam supports. Set a distribution beam at the mid-span and center position of the top surface of the precast T-beam. Spread fine sand on the bottom surface of the distribution beam and the top of the precast T-beam. The distribution beam abuts against the precast T-beam to form a loading point under the action of a hydraulic jack. Step 2: Adjust the pivot joint structure in the measuring device so that the sensing surface of the laser displacement sensor is perpendicular to the bottom of the precast T-beam. After confirmation, tighten the pivot joint structure and fix the laser displacement sensor. Start the laser displacement sensor, zero it, and select recording. Then, push the measuring device at a constant speed, causing the laser displacement sensor to move in a uniform linear motion along the length of the T-beam. The laser displacement sensor emits laser light towards the bottom of the precast T-beam and converts the reflected laser light into electrical signals in the laser displacement sensor. The collected electrical signals are converted into stable linear outputs by the built-in processor of the laser displacement sensor, generating a function curve corresponding to the pre-camber, which is displayed on the screen of the laser displacement sensor. Then, repeat the above operation for each measuring device one by one. Finally, summarize the pre-camber data of the precast T-beams measured for all segments, fit the interruption position of the adjusting device, complete the measurement operation of the precast T-beam pre-camber, and form a complete function curve along the length of the T-beam. Based on the above measurement results, if the arch height H1 of the upper part of the T-beam span is greater than the design value H2 of the pre-camber, then proceed to step three. If the arch height H1 of the upper part of the T-beam mid-span is less than the design value H2 of the pre-camber, then step four is required; Step 3: Beam straightening. Slide the laser displacement sensor in the middle section of the precast T-beam along the guide rail to the bottom mid-span position of the precast T-beam and record the reading of the laser displacement sensor at this time. Then, start the hydraulic jack on the reaction frame device to apply pressure to the distribution beam. As the pressure F of the hydraulic jack on the mid-span of the precast T-beam increases, the reading on the laser displacement sensor will decrease accordingly. When the reading on the laser displacement sensor is 1 cm less than the precamber design value, stop loading. After the reading stabilizes, maintain the pressure with the hydraulic jack. After N hours, slowly unload the pressure from the hydraulic jack. After unloading, the precast T-beam will rebound by about 1 cm. The precamber after rebound meets the design value requirements. Step 4: Beam straightening. Move the laser displacement sensor along the guide rail to the position where the pre-camber needs to be adjusted and record the initial reading. Then, raise the height of the adjustment device, which generates an upward thrust F1 on the precast T-beam. While adjusting the adjustment device, observe the reading on the laser displacement sensor. When the displayed reading is H2, stop rotating. After the reading stabilizes, maintain this state for N hours, then adjust and control the adjustment device to lower, and observe the reading on the laser displacement sensor. If the reading after unloading remains at H2, the pre-camber of the precast T-beam meets the design requirements. If the reading after unloading is less than H2, it indicates that the bottom plate of the precast T-beam has rebounded. After rebound, use the secondary tensioning process to adjust the pre-camber of the precast T-beam. Install the anchor plate, anchor, and connector according to the corresponding specifications, start the tensioning machine, and observe the laser displacement sensor. When the reading of the laser displacement sensor meets the design requirement H2, stop loading, record the tension stress corresponding to this program, and maintain this load intensity for N minutes. At this time, the pre-camber of the precast T-beam meets the design requirements, and stop the secondary tensioning.

2. The construction method for measuring and adjusting the pre-camber of a precast T-beam according to claim 1, characterized in that, The reaction frame device includes two steel columns perpendicular to the ground, arranged on the left and right sides of the space where the precast T-beam is placed. A crossbeam is set between the two steel columns. The lower ends of the steel columns are fixed. Two beam supports are set in conjunction with the reaction frame device. A hydraulic jack is vertically installed on the crossbeam. The piston of the hydraulic jack faces downward and a distribution beam is fixedly installed on the piston.

3. The construction method for measuring and adjusting the pre-camber of a precast T-beam according to claim 1, characterized in that, The load-bearing ground beam is set along the length of the precast T-beam and is located in the space between the supports at both ends.

4. The construction method for measuring and adjusting the pre-camber of a precast T-beam according to claim 1, characterized in that, The adjustment device includes a base, a pad, a parallelogram lifting rod, a rotating rod, and a rotating wheel. The lower lifting rod is connected to the base, and a threaded rotating rod is inserted near the hinge point of the lower and upper lifting rods. The pad is fixed to the top of the upper lifting rod, and a rotating wheel is welded to one end of the rotating rod.

5. A construction method for measuring and adjusting the pre-camber of a precast T-beam according to claim 1, characterized in that, The adjustment device is an electrically driven or manually driven scissor jack or a hydraulic jack.

6. A construction method for measuring and adjusting the pre-camber of a precast T-beam according to claim 1, characterized in that, The measuring device includes a sliding guide rail, on which a slider is movably connected. A plate is fixed above the slider, and the plate is provided with a slot and a handle. A vertical rod is fixed in the slot, and the top of the vertical rod is connected to a mounting plate through a pivot joint structure. A laser displacement sensor is fixedly mounted on the mounting plate.

7. A construction method for measuring and adjusting the pre-camber of a precast T-beam according to claim 1, characterized in that, The number of measuring and adjusting devices may be increased or decreased according to the specifications of the precast T-beams.

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