Control method for staged synchronous beam falling after multi-point pushing of large-span steel truss beam

Abstract

The application discloses a kind of large-span steel truss beam multi-point post-pushing grading synchronous beam falling control method, belong to bridge construction technical field.The application solves the problem of poor synchronism, local overload or void caused by strong coupling of each support load and displacement in the existing beam falling control method, and the problem of insufficient control accuracy caused by lack of real-time correction of slip, angle and temperature parameters.The method comprises: setting a multi-degree-of-freedom adaptive support seat between the jack and the beam body and installing gap, displacement, pressure and strain sensors;grading the beam falling process;before each stage of beam falling, input the slip amount, angle amount and strain data into the prediction model to calculate the corrected bending moment, then calculate the theoretical jacking force and preset the initial value;when the deviation of the jacking force of a certain jack from the average value of its group exceeds the limit during beam falling, only suspend the group and adjust to normal to restore synchronization;repeat until the entire stroke is completed.The application is mainly used for large-span steel truss beam multi-point post-pushing beam falling construction.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology. More specifically, this invention relates to a method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking. Background Technology

[0002] In the construction of long-span steel truss beams, the multi-point jacking method is widely used due to its advantages such as not requiring large-scale water or ground lifting equipment and minimal impact on traffic. After jacking into place, the steel truss beam needs to be smoothly lowered from the temporary jacking support to the permanent support, which is the "beam lowering" process.

[0003] Currently, traditional methods for controlling the lowering of truss beams typically involve simultaneously lowering multiple jacks or relying solely on the operator's experience to adjust each support point in stages and batches. However, for large-span flexible steel truss beams, this traditional method has the following problems: As the structural system of the beam changes continuously during the beam lowering process, the redistribution of its internal forces is complex. In addition, the strong coupling between the load and displacement of each support point makes it difficult for traditional methods to coordinate and control the jacking force and lowering stroke of all jacks in real time and accurately. This can easily lead to overloading or detachment of individual support points, which in turn causes large additional stress and deformation in the beam. Existing control methods generally lack effective monitoring and correction of complex operating parameters such as support slippage and beam rotation, as well as compensation mechanisms to cope with environmental factors such as temperature changes, making it difficult to guarantee the synchronicity and structural safety of the beam dropping process.

[0004] Therefore, it is necessary to propose a beam drop control method that can achieve multi-dimensional real-time monitoring, hierarchical precise control, and fault tolerance to solve the above problems. Summary of the Invention

[0005] One objective of this invention is to provide a method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking, comprising the following steps: A multi-degree-of-freedom adaptive support is set between the jack at each jacking support point and the steel truss beam. The support includes a spherical crown-shaped support head and an arc-shaped base that matches the support head. A self-lubricating wear-resistant layer is provided at the contact surface between the support head and the arc-shaped base. A gap sensor is also provided. Displacement sensors and pressure sensors are installed at each jacking support point, and strain sensors are installed at at least one key node of the steel truss beam. Determine the total beam drop height and divide the beam drop process into 3 to 5 stages, with each stage dropping 20% ​​to 35% of the total beam drop height; Before each stage of beam drop begins, the slippage amount collected by the gap sensor is... S and angle measurementi The strain data collected by the strain sensor is input into the built-in real-time thrust prediction model. Calculate the uncorrected bending moment using the strain data. M 0 Then calculate the corrected bending moment. M 1 = M 0 - K 1 × i - K 2 × S ,in K 1 This is the corner correction factor. K 2 This is the slip correction factor, and then according to M 1 Calculate the theoretical jacking force of each jack. F t And accordingly, the initial thrust of each jack is adjusted in advance; During the current stage of beam lowering, each jack is controlled to simultaneously execute one lowering stroke, and the jacking force of each jack is monitored in real time through the pressure sensor. When any... i The jacking force of the jack F i The average jacking force of all jacks in its synchronous control group F avg The difference Δ F Satisfying the formula |Δ F |> F avg × d At that time, only the beam lowering operation of the synchronous control group to which the over-limit jack belongs is paused, and the jacking force of the over-limit jack is adjusted until the difference returns to within the specified range. Then, the pause is lifted, and synchronous lowering with other groups resumes. F avg This is the arithmetic mean of the jacking forces of all jacks within the synchronous control group. d The value range is 5% to 15%; Repeat the above steps until all jacks have completed their entire descent.

[0006] Preferably, the real-time thrust prediction model calculates the uncorrected bending moment in the following manner. M 0 Theoretical top thrust F t : The model utilizes real-time strain data acquired by the strain sensor at at least the mid-span position and the 1 / 4 span position. e k ,in k Number the strain sensor; Through formula M 0 = f(e 1 , e 2 , …, e k , E , I Calculate the uncorrected bending moment of the steel truss beam. M 0 ,in, E The elastic modulus of the beam material. I The moment of inertia of the beam section; Through formula F t = g ( M 1 , x , L Calculate the position coordinates. x The theoretical jacking force at the location F t ,in, L The total span of the steel truss beam is given.

[0007] Preferably, the steps for adjusting the jacking force of the over-limit jack include: Identify overloaded jacks whose jacking force exceeds the allowable range, and lock the current beam-dropping height of the overloaded jacks; A reverse micro-lift command is sent to the over-limit jack, controlling the over-limit jack to perform a micro-lifting action in the opposite direction to the beam dropping direction. The stroke ΔH of the reverse micro-lift is in the range of 0.5~1.0mm. After performing the reverse micro-lift action, the jacking force of the over-limit jack is re-acquired through the pressure sensor and compared with the jacking forces of other jacks in the synchronous control group to which the over-limit jack belongs, to determine whether the jacking force difference has recovered to |Δ F |> F avg × d Within the specified range.

[0008] Preferably, after each stage of beam lowering is completed, a data verification step is also included: The measured final displacement values ​​of each of the aforementioned jacks D a Based on the modified bending moment M 1 Calculated theoretical displacement valuesD t Compare the two; if the deviations satisfy | D a - D t |> D th ,in D th If the value range is 1~5mm, then before the next stage of beam lowering begins, a fine-tuning lifting step is added by the jack to reduce the displacement deviation to within 1.5mm before proceeding to the next stage of beam lowering.

[0009] Preferably, a temperature correction step is included in the steps before each stage of beam lowering: Temperature deformation data of the beam is collected by 3 to 5 temperature sensors arranged along the length of the steel truss beam. Based on the temperature deformation data, the formula is used... F c = F t ×(1+ α ×Δ T ) for the theoretical top thrust F t Make corrections, where Δ T This represents the temperature change value. α This is a temperature correction factor. α The value range is 0.5~2% of the theoretical thrust for each temperature change per ℃.

[0010] Preferably, a backup control mode is also included in case of gap sensor malfunction: When the gap sensor signal is detected to be abnormal or lost, the system automatically switches to the backup control mode, suspends the predictive adjustment function at the support point, and enables the guaranteed jacking force control based on a preset safety factor. The guaranteed jacking force is the average jacking force at the support point during the previous stage of beam lowering multiplied by the predetermined safety factor.

[0011] Preferably, at the beam end support of the steel truss beam, the spacing between two adjacent jacking supports is... S e The distance between two adjacent jacking supports in the mid-span region of the steel truss beam is less than the distance between them. S m .

[0012] Preferably, during each stage of beam lowering, the execution speed of one downward stroke of the jack located in the beam end support area is... V e The execution speed is less than the single drop stroke of the jack located in the mid-span region.V m And the speed difference between the two ( V m - V e ) / V m The value range is 0.15 to 0.25.

[0013] Preferably, after all beam lowering operations are completed, the final elevation collaborative verification and overall adjustment steps are performed: Measure the final elevation at all jacking points; Calculate the elevation deviation Δ between any two adjacent support points. H f ; If any Δ H f Exceeding the allowed range H lim ,in H lim If the value range is 3~8mm, then a fine-tuning jacking operation is performed on the jacks at the support points where the elevation is too low, and the jacking amount Δ at each support point is... H l The value range is 1~3mm.

[0014] Preferably, after all beam lowering operations are completed, a final stress-based verification step is also included: Collect the final strain data of all strain sensors after the beam is lowered to this stage. e f ; Based on the final strain data e f According to the calculation of the uncorrected bending moment M 0 In the same manner, the actual residual bending moments of the steel truss beam at each critical node were calculated. M r ; The actual residual bending moment at each of the key nodes M r Theoretical residual bending moment based on design profile M th Compare, and through | M r - M th Calculate the residual bending moment deviation Δ at each node. M ; When the residual bending moment deviation at any node Δ M Greater than the preset allowable bending moment deviation M all At that time, among themM all The value range is 1% to 3% of the design bending moment. Based on the structural stiffness matrix of the steel truss beam, the residual bending moment deviation Δ is adjusted by simultaneously adjusting the lifting or lowering displacement of multiple jacks. M Reduce to the allowable bending moment deviation M all the following.

[0015] The present invention has at least the following beneficial effects: First, this invention sets up a multi-degree-of-freedom adaptive support base and installs displacement, pressure, and strain sensors at each support point to monitor the slippage, rotation, and internal force state of the beam in real time. At the same time, based on a real-time jacking force prediction model, the theoretical jacking force is corrected according to the monitoring data before each stage of beam lowering. During the beam lowering process, a component-based synchronous correction strategy is adopted (only pausing the group containing the overload jacks). This can effectively solve the problem of local overload or detachment caused by the strong coupling of load and displacement at each support point in traditional methods, thereby significantly improving the synchronicity and structural safety of the beam lowering process.

[0016] Secondly, this invention monitors the slippage amount by introducing a gap sensor. S and rotation angle i By correcting the bending moment and compensating for the theoretical jacking force using temperature deformation data collected by temperature sensors, the interference of environmental factors such as non-ideal support constraints and temperature changes on the accuracy of beam lowering control can be effectively eliminated, making the jacking force of the jacks closer to the actual working conditions and realizing precise control of the beam's stress and deformation.

[0017] Third, during the beam lowering process, when an excessive thrust of a jack is detected, only the synchronous control group of the jack with the excessive thrust is paused for adjustment, while the jacks in other groups can continue to fall. This avoids a global shutdown caused by a local problem, thereby significantly reducing the number of repeated start-stop operations during construction, improving the construction efficiency of beam lowering operations, and reducing the risk of fatigue damage to the beam structure caused by frequent start-stop operations.

[0018] Fourth, the control method of the present invention not only sets up a backup control mode (activating the bottom thrust control based on the preset safety factor) when the gap sensor is abnormal, ensuring that the system can still operate safely when the sensor fails; but also sets up displacement deviation verification and fine adjustment and final elevation and residual bending moment verification and adjustment steps after each stage of beam placement and after all beams are placed, so that the entire beam placement process has multi-level quality control capabilities from local to overall, ensuring that the internal force and alignment accuracy of the final beam placement meet the design requirements.

[0019] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the experimental methods described in the following implementation plan are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified.

[0021] This invention provides a method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking, comprising the following steps: At each jacking support point, a multi-degree-of-freedom adaptive support is installed between the jack and the steel truss beam. Each support includes a spherical crown-shaped support head and an arc-shaped base matching the support head. A self-lubricating wear-resistant layer is provided at the contact surface between the support head and the arc-shaped base, and a gap sensor is also installed. Specifically, the spherical crown-shaped support head can be made of high-carbon chromium bearing steel through forging and precision grinding, with a surface roughness controlled below Ra0.8μm. The arc-shaped base can be made of cast steel through casting and machining, with the radius of curvature of its concave spherical surface matching the radius of curvature of the support head. The gap between the two can be controlled between 0.1 and 0.5 mm. The self-lubricating wear-resistant layer can be made of polytetrafluoroethylene composite material or modified ultra-high molecular weight polyethylene material. This self-lubricating wear-resistant layer can be fixed to the concave surface of the arc-shaped base by hot pressing or bonding. Its thickness can be set to 2-5 mm. The gap sensor can be an inductive displacement sensor or a capacitive displacement sensor. The gap sensor can be installed on the side of the arc-shaped base and near the edge of the spherical crown support head. The sensor probe contacts the side of the support head and is used to measure the amount of horizontal slippage of the support head relative to the base in real time. S and the angle of rotation about the horizontal axis i ; Displacement sensors and pressure sensors are installed at each jacking support point, and strain sensors are installed at at least one key node of the steel truss beam. Specifically, the displacement sensor can be a wire-type displacement sensor or a magnetostrictive displacement sensor, which can be installed on the side of the jack cylinder, with its wire end or magnetic ring end connected to the piston rod or jacking bracket of the jack, for measuring the extension stroke of the jack. The pressure sensor can be a strain gauge pressure sensor or a hydraulic pressure sensor, which can be installed at the oil inlet or outlet of the jack, for measuring the jacking force of the jack. The strain sensor can be a resistance strain gauge or a fiber Bragg grating strain sensor, which can be attached to the surface of the lower chord at the mid-span position and the surface of the upper chord at the quarter-span position of the steel truss beam, for measuring the bending strain of the steel truss beam during the beam lowering process. The total beam drop height is determined, and the beam drop process is divided into 3 to 5 stages, with each stage dropping 20% ​​to 35% of the total beam drop height. Specifically, the total beam drop height can be determined by measuring the difference between the actual elevation of the steel truss beam after jacking and the design elevation. For example, when the total beam drop height is 120mm, it can be divided into 4 stages, with each stage dropping 30mm, or into 5 stages, with the first stage dropping 12mm (10%) and the subsequent four stages dropping 27mm (22.5%). However, it is more preferable that the drop height is evenly distributed across each stage. For example, when divided into 4 stages, each stage drops 30mm (30mm accounts for 25% of 120mm, which is within the 20%-35% range), or into 5 stages, with each stage dropping 24mm (20%). The specific values ​​for each stage can be determined in the construction plan based on the structural stiffness of the steel truss beam and the stroke capacity of the jacks. Before each stage of beam drop begins, the slippage amount collected by the gap sensor is... S and angle measurement i The strain data collected by the strain sensor is input into the built-in real-time thrust prediction model. Calculate the uncorrected bending moment using the strain data. M 0 Then calculate the corrected bending moment. M 1 = M 0 - K 1 × i - K 2 × S ,in K 1 This is the corner correction factor. K 2 This is the slip correction factor, and then according to M 1 Calculate the theoretical jacking force of each jack. F t Based on this, the initial jacking force of each jack is adjusted in advance; specifically, the rotation angle correction coefficient... K 1 The value range can be 0.8 to 1.5 times the bending moment correction per degree of rotation; for example, it can be set to 1.0 times, which is the slip correction coefficient. K 2 The value range can be 0.2 to 0.4 times the bending moment correction per millimeter of slippage. For example, it can be set to 0.3 times, and the corrected bending moment... M 1 Through formula M 1 = M0 - K 1 × i - K 2 × S Calculations show that the negative sign in the formula indicates that when the support exhibits positive rotation and positive slippage, the direction of the additional bending moment on the beam is different from the direction of the uncorrected bending moment. M 0 The directions are opposite, so it is necessary to start from... M 0 Subtract from the middle, and finally based on the corrected bending moment. M 1 The theoretical jacking force of each jack is calculated by determining the coordinates of its support position under the steel truss beam, solving the static equilibrium equations, or using a pre-established matrix relating support reactions and bending moments. F t ; During the current stage of beam lowering, each jack is controlled to simultaneously execute one lowering stroke, and the jacking force of each jack is monitored in real time through the pressure sensor. When any... i The jacking force of the jack F i The average jacking force of all jacks in its synchronous control group F avg The difference Δ F Satisfying the formula |Δ F |> F avg × d At that time, only the beam lowering operation of the synchronous control group to which the over-limit jack belongs is paused, and the jacking force of the over-limit jack is adjusted until the difference returns to within the specified range. Then, the pause is lifted, and synchronous lowering with other groups resumes. F avg This is the arithmetic mean of the jacking forces of all jacks within the synchronous control group. d The value range is 5% to 15%; specifically, all jacks can be divided into multiple synchronous control groups according to their position in the longitudinal direction of the steel truss beam. For example, each group can contain 2 to 4 adjacent jacks. dThe value can be set to 10%. That is, when the jacking force of a certain jack deviates from the average value of its group by more than 10%, the jack is determined to be an over-limit jack. The control unit of the system immediately sends a pause descent command to the group to which the over-limit jack belongs through the hydraulic valve, but the jacks of other groups continue to descend. During the pause, the control unit performs adjustment actions such as reverse micro-lifting or forward speed-up on the over-limit jack, so that its jacking force gradually approaches the average value of its group. At this time, since other groups are still falling synchronously, the overall displacement of the beam will change continuously. However, each adjustment (reverse micro-lifting 0.5~1.0mm) is of the same order of magnitude as the descent stroke of other groups (a single descent stroke is usually 1~2mm). Moreover, the system operates in a high-frequency monitoring-adjustment cycle (sampling period <0.1s). Therefore, the force disturbance of the paused group during the adjustment process can be converged through subsequent iterations. When the deviation value recovers to less than or equal to 10% of the average value, the control unit releases the pause state of the group and resumes its synchronous descent with other groups. Repeat the above steps until all jacks have completed their entire descent.

[0022] The above method enables precise control of the stress and deformation of the beam during the lowering process after multi-point jacking of a large-span steel truss beam. This method releases the local rotation and translation constraints of the beam through multi-degree-of-freedom adaptive support seats, corrects the bending moment for slippage and rotation angle through a real-time jacking force prediction model, making the theoretical jacking force closer to the actual working conditions. At the same time, through a component-based synchronous correction strategy, only one set of jacks is suspended when the local jacking force exceeds the limit, rather than the entire machine is shut down, which significantly improves construction efficiency and reduces the risk of fatigue damage to the beam structure caused by repeated start-stop operations.

[0023] In another technical solution, the real-time thrust prediction model calculates the uncorrected bending moment in the following manner. M 0 Theoretical top thrust F t : The model utilizes real-time strain data acquired by the strain sensor at at least the mid-span position and the 1 / 4 span position. e k ,in k Number the strain sensor; Through formula M 0 = f(e 1 , e 2 , …, e k , E , I Calculate the uncorrected bending moment of the steel truss beam.M 0 ,in, E The elastic modulus of the beam material. I The moment of inertia of the beam section; Through formula F t = g ( M 1 , x , L Calculate the position coordinates. x The theoretical jacking force at the location F t ,in, L The total span of the steel truss beam; Specifically, resistance strain gauges or fiber Bragg grating strain sensors can be used. One strain sensor is attached to the surface of each of the upper and lower chords at the mid-span and 1 / 4 span positions, for a total of four strain sensors, numbered as follows: e 1 to e 4 The elastic modulus of the beam material E You can look up the value in the material handbook based on the steel grade. For example, the elastic modulus of Q345 steel can be taken as 206 gigapascals, and the moment of inertia of the beam section... I It can be calculated based on the structural design drawings of the steel truss beam. For a steel truss beam with a variable cross-section, I can be taken as the moment of inertia at the mid-span section, and the function... f The mapping relationship can be calculated using the bending moment formula based on the plane section assumption in mechanics of materials, i.e. M 0 =(E×I× e k ) / y k ,in y k For the first k The distance from each strain sensor to the neutral axis of the beam can be used to calculate the uncorrected bending moment at each key section. For continuous beams with multiple supports, this can be achieved by combining influence lines or finite element methods, substituting the strain data from multiple measuring points into a pre-established multi-point bending moment calculation formula. M 0 ,function g The mapping relationship can be calculated using the support reaction formula based on static equilibrium, that is, based on the corrected bending moment. M 1 and the coordinates of the jack's position x By solving the support reaction equations of the continuous beam, the theoretical jacking force at each support point can be obtained. F t .

[0024] In another technical solution, the steps for adjusting the jacking force of the over-limit jack include: Identify overloaded jacks whose jacking force exceeds the allowable range, and lock the current beam-dropping height of the overloaded jacks; A reverse micro-lift command is sent to the over-limit jack, controlling the over-limit jack to perform a micro-lifting action in the opposite direction to the beam dropping direction. The stroke ΔH of the reverse micro-lift is in the range of 0.5~1.0mm. After performing the reverse micro-lift action, the jacking force of the over-limit jack is re-acquired through the pressure sensor and compared with the jacking forces of other jacks in the synchronous control group to which the over-limit jack belongs, to determine whether the jacking force difference has recovered to |Δ F |> F avg × d Within the specified range; Specifically, when the control system determines that a jack is over-limit, it reads the current height of the jack through the displacement sensor and locks it as the reference height. Then, it sends a reverse micro-lift command to the jack through the hydraulic proportional valve, causing the piston rod of the jack to rise by about 0.8mm. This process lasts for about 0.5 to 1 second. After the micro-lift is completed, the hydraulic system briefly stabilizes for about 1 to 2 seconds to wait for the pressure sensor reading to stabilize. Then, the control unit rereads the pressure values ​​of the over-limit jack and other jacks in its group, calculates the deviation between the current jack's thrust and the average value in the group. If the deviation has recovered to less than or equal to 10% of the average value, the jack's pause state is released. If the deviation is still over-limit, the above reverse micro-lift action can be repeated. Each micro-lift stroke can be increased by 0.1 to 0.2mm, but the total reverse micro-lift stroke should not exceed 3mm to avoid excessive impact on adjacent support points.

[0025] In another technical solution, a data verification step is also included after each stage of beam lowering is completed: The measured final displacement values ​​of each of the aforementioned jacks D a Based on the modified bending moment M 1 Calculated theoretical displacement values D t Compare the two; if the deviations satisfy | D a - D t |> D th ,in D thIf the value range is 1~5mm, then before the next stage of beam lowering begins, a fine-tuning lifting step is added by the jack to reduce the displacement deviation to within 1.5mm before proceeding to the next stage of beam lowering. Specifically, theoretical displacement values D t The bending moment can be calculated using a finite element model, with the corrected bending moment input into the finite element model. M 1 And based on the current descent height of the beam, calculate the expected displacement at each support point. D t The setting can be 3mm. When the deviation between the measured displacement and the theoretical displacement exceeds 3mm, the control unit starts the fine-tuning program, selects the jack corresponding to the support point with the smaller measured displacement, and performs fine-tuning lifting. The stroke of fine-tuning lifting can be determined according to the size of the deviation value. For example, if the deviation value is 4mm, the fine-tuning lifting stroke can be set to 2~3mm. After the fine-tuning lifting is completed, the displacement at the support point is measured again. If the deviation has been reduced to within 1.5mm, the next stage of beam lowering begins. If the deviation is still greater than 1.5mm, fine-tuning lifting is performed again until the requirements are met.

[0026] In another technical solution, a temperature correction step is also included in the process before each stage of beam lowering: Temperature deformation data of the beam is collected by 3 to 5 temperature sensors arranged along the length of the steel truss beam. Based on the temperature deformation data, the formula is used... F c = F t ×(1+ α ×Δ T ) for the theoretical top thrust F t Make corrections, where Δ T This represents the temperature change value. α This is a temperature correction factor. α The value range is 0.5% to 2% of the theoretical thrust for each temperature change per ℃. Specifically, thermocouple temperature sensors or platinum resistance temperature sensors can be selected as the temperature sensors. Four temperature sensors can be installed on the surface of the lower chord at the beam ends, 1 / 4 span, mid-span, and 3 / 4 span positions of the steel truss beam, respectively, to measure the actual temperature of the beam and the temperature change value Δ. T It can be taken as the difference between the current temperature and the temperature before the previous beam drop began, or the difference between the current temperature and the reference temperature at 6:00 AM. α It can be set that the adjustment range of the jacking force for each degree Celsius temperature change is 1% of the theoretical jacking force. That is, if the temperature rises by 10°C, the adjusted jacking force will be...F c = F t ×1.1, an increase of 10%.

[0027] Another technical solution also includes a backup control mode in case of gap sensor malfunction: When the gap sensor signal is detected to be abnormal or lost, the system automatically switches to the backup control mode, suspends the predictive adjustment function at the support point, and enables the guaranteed jacking force control based on a preset safety factor. The guaranteed jacking force is the average jacking force at the support point during the previous stage of beam lowering multiplied by the predetermined safety factor. Specifically, the control unit continuously monitors the communication status and the validity of the output values ​​of each gap sensor. When it detects that the output value of a gap sensor remains zero for a long time, the output value suddenly exceeds a preset threshold, or the communication is interrupted for more than 5 seconds, it determines that the sensor is abnormal. The control unit immediately removes the data of the gap sensor corresponding to that fulcrum from the prediction model and calculates the slip at that fulcrum. S and rotation angle i By forcibly setting it to zero, the amount of bending moment correction at the location of that support point is calculated when calculating the corrected bending moment M1. K 1 × i and K 2 × S All values ​​are set to zero. Simultaneously, the theoretical jacking force at that fulcrum is... F t The average jacking force during the previous stage of beam lowering is multiplied by a safety factor, which can be taken as 1.1. In the standby mode, since the slippage and rotation data of this support point are missing, the average thrust of the previous stage at this support point is used as the basis for applying the safety factor as the fixed jacking force, and is combined with the dynamic adjustment of other support points to ensure that the overall coordination will not be seriously deteriorated.

[0028] In another technical solution, the distance between two adjacent jacking supports at the beam end supports of the steel truss beam is... S e The distance between two adjacent jacking supports in the mid-span region of the steel truss beam is less than the distance between them. S m Specifically, the beam end support area refers to the area within 5m of the centerline of the permanent support, and the distance between two adjacent launching points in this area is... S e The distance can be set to 2-3m. The mid-span region refers to the area in the middle of the beam that is far from the support. The distance between two adjacent launching supports in this region is... S mThe spacing can be set to 6~10m. For example, for a steel truss beam with a span of 60m, four jacking supports with a spacing of 3m can be set within a 12m range at each end of the beam, and four jacking supports with a spacing of 9m can be set within a 36m range in the middle.

[0029] In another technical solution, during each stage of beam lowering, the execution speed of one downward stroke of the jack located in the beam end support area is... V e The execution speed is less than the single drop stroke of the jack located in the mid-span region. V m And the speed difference between the two ( V m - V e ) / V m The value range is 0.15~0.25; specifically, the falling speed of the jack in the mid-span area. V m The descent speed of the jacks in the beam end area can be set to 10 mm / min. V e It can be set to 8mm / min, at which point the speed difference is 2mm per minute, and the speed difference ratio is 0.2, which falls within the range of 0.15~0.25. This speed difference can be achieved by setting independent flow control valves for the jacks in different areas of the hydraulic system, that is, the opening degree of the flow control valve in the beam end area is smaller than that in the mid-span area.

[0030] In another technical solution, after all beam lowering operations are completed, a final elevation collaborative verification and overall adjustment step is performed: Measure the final elevation at all jacking points; Calculate the elevation deviation Δ between any two adjacent support points. H f ; If any Δ H f Exceeding the allowed range H lim ,in H lim If the value range is 3~8mm, then a fine-tuning jacking operation is performed on the jacks at the support points where the elevation is too low, and the jacking amount Δ at each support point is... H l The value range is 1~3mm; Specifically, the final elevation can be measured using a total station or a level. The measurement should be taken when each jack is still bearing the load of the beam but is close to the final placement (i.e., before the last stage of beam placement is completed, and the beam is not yet fully placed on the permanent supports). The measurement point can be set on the support plate where the lower chord of the steel truss beam contacts the jack. H lim The setting can be 5mm. When the elevation deviation between two adjacent support points exceeds 5mm, for example, if the measured elevation of the left support point is 6mm lower than that of the right support point, then the jack at the left support point is finely adjusted and lifted. The lifting amount can be set to 2mm. After the lifting is completed, the elevation of the support point and the elevation of its adjacent support points are remeasured. If the deviation is less than 5mm at this time, the adjustment is completed. If it still exceeds the limit, the fine adjustment continues until the requirements are met.

[0031] In another technical solution, after all beam lowering operations are completed, a final verification step based on stress is also included: Collect the final strain data of all strain sensors after the beam is lowered to this stage. e f ; Based on the final strain data e f According to the calculation of the uncorrected bending moment M 0 In the same manner, the actual residual bending moments of the steel truss beam at each critical node were calculated. M r ; The actual residual bending moment at each of the key nodes M r Theoretical residual bending moment based on design profile M th Compare, and through | M r - M th Calculate the residual bending moment deviation Δ at each node. M ; When the residual bending moment deviation at any node Δ M Greater than the preset allowable bending moment deviation M all At that time, among them M all The value range is 1% to 3% of the design bending moment. Based on the structural stiffness matrix of the steel truss beam, the residual bending moment deviation Δ is adjusted by simultaneously adjusting the lifting or lowering displacement of multiple jacks. M Reduce to the allowable bending moment deviation M all the following; Specifically, allowable bending moment deviation M allThe allowable deviation can be set to 2% of the design bending moment value. For example, if the design bending moment value is 10000 kN·m, the allowable deviation is 200 kN·m. When the residual bending moment deviation exceeds 200 kN·m, the control system retrieves the structural stiffness matrix of the steel truss beam pre-stored in the control unit. This stiffness matrix describes the correspondence between the unit displacement change at each support and the bending moment change at each key node. The displacement of the jacks that need to be adjusted is obtained by solving the linear equation system. Then, the control unit simultaneously issues lifting or lowering commands to all jacks that need to be adjusted. The displacement adjustment can be performed at 60% of the calculated value to avoid overshoot. After the adjustment is completed, the strain data is re-acquired to calculate the residual bending moment. The above process is repeated until the residual bending moment deviation of all nodes is within the allowable range.

[0032] <Example> After the 120m span steel truss bridge is constructed using the multi-point jacking method, the beam needs to be lowered from the temporary jacking support to the design elevation, with a total lowering height of 120mm.

[0033] Construction is carried out using the graded synchronous beam dropping control method of the present invention: Multi-degree-of-freedom adaptive support seats are installed between the jacks and the steel truss beams at each jacking support point. The support seats include a spherical crown-shaped support head and an arc-shaped base. The contact surfaces are provided with a self-lubricating and wear-resistant layer, and gap sensors are installed to monitor the slippage in real time. S and rotation angle i At each support point, wire-type displacement sensors and strain-type pressure sensors are installed. Meanwhile, fiber Bragg grating strain sensors are attached to the surface of the lower chord at the mid-span and 1 / 4 span position to collect bending strain data. Based on the beam stiffness and jack stroke capacity, the beam lowering process is divided into 4 stages, with each stage having a height of 30mm evenly distributed, and each stage accounting for 25% of the total height. Before each stage of beam lowering begins, the slippage amount collected by the gap sensor is... S and rotation angle i Along with strain data collected by strain sensors, the data is input into the built-in real-time thrust prediction model, which uses strain data at mid-span and 1 / 4 span to calculate the uncorrected bending moment. M 0 Then through the formula M 1 = M 0 - K 1 × i - K 2 × S Calculate the corrected bending moment, where K 1 Take 1.0, K2 Take 0.3, and then calculate the theoretical jacking force of each jack based on the corrected bending moment and the coordinates of each jack's position. F t The initial jacking force was pre-adjusted, and temperature deformation data was collected using four temperature sensors arranged along the beam, according to the formula. F c = F t ×(1+ α ×Δ T Perform temperature correction. α Take 1% / ℃, and ΔT is the difference between the current temperature and the reference temperature at 6:00 AM; During the beam lowering process, all jacks are controlled to simultaneously execute one lowering stroke (each stroke is 30mm, completed in multiple small strokes), and the thrust of each jack is monitored in real time. The jacks are divided into 4 synchronous control groups along the longitudinal direction (each group consists of 2-3 adjacent jacks). d The setting is 10%. When the deviation of the thrust of a certain jack from the average value of its group exceeds 10%, only the synchronous control group of the jack that exceeds the limit is suspended, and a reverse micro-lifting action (stroke 0.8mm) is performed on it. After adjustment, the deviation is restored to within ±10% of the average value, and then the suspension is lifted and the synchronous descent with other groups is resumed. During the entire beam lowering process, the system operates at a high frequency with a sampling period of 0.1s. Through the above group correction strategy, local overload or detachment is effectively avoided, and no global shutdown occurs. After each stage of beam lowering is completed, data verification is performed: the measured displacement of each jack is recorded. D a Compared with modified bending moment M 1 Calculated theoretical displacement D t contrast, D t The initial setting was 3mm, and the actual measured deviation did not exceed 3mm, so no additional fine-tuning was needed. After all four levels of beam lowering were completed, a final elevation collaborative verification was performed: the elevation at all support points was measured using a total station (at this time, the beam was still supported by jacks), and the maximum elevation deviation between adjacent support points was 4mm, which is less than... H lim The 5mm adjustment requires no fine-tuning. Then, the final data from the strain sensor is collected to calculate the actual residual bending moment. M r The residual bending moment deviations at each key node were all less than 2% of the design bending moment value (for example, the residual bending moment deviation at mid-span was 1.5% of the design value), meeting the allowable deviation requirements. Finally, the beam was smoothly placed on the permanent support, with a smooth alignment and uniform internal forces. The construction efficiency was improved by about 30% compared to the traditional method, and no safety accidents occurred.

[0034] This embodiment demonstrates that the method of the present invention achieves high precision, high synchronization, and high safety in the process of lowering large-span steel truss beams through multi-degree-of-freedom adaptive support, real-time jacking force prediction model, group synchronous correction, and multi-level verification and adjustment, and has significant technical effects.

[0035] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking, characterized in that... Includes the following steps: A multi-degree-of-freedom adaptive support is set between the jack at each jacking support point and the steel truss beam. The support includes a spherical crown-shaped support head and an arc-shaped base that matches the support head. A self-lubricating wear-resistant layer is provided at the contact surface between the support head and the arc-shaped base. A gap sensor is also provided. Displacement sensors and pressure sensors are installed at each jacking support point, and strain sensors are installed at at least one key node of the steel truss beam. Determine the total beam drop height and divide the beam drop process into 3 to 5 stages, with each stage dropping 20% ​​to 35% of the total beam drop height; Before each stage of beam drop begins, the slippage amount collected by the gap sensor is... S and angle measurement θ The strain data collected by the strain sensor is input into the built-in real-time thrust prediction model. Calculate the uncorrected bending moment using the strain data. M 0 Then calculate the corrected bending moment. M 1 = M 0 - K 1 × θ - K 2 × S ,in K 1 This is the corner correction factor. K 2 This is the slip correction factor, and then according to M 1 Calculate the theoretical jacking force of each jack. F t And accordingly, the initial thrust of each jack is adjusted in advance; During the current stage of beam lowering, each jack is controlled to simultaneously execute one lowering stroke, and the jacking force of each jack is monitored in real time through the pressure sensor. When any... i The jacking force of the jack F i The average jacking force of all jacks in its synchronous control group F avg The difference Δ F Satisfying the formula |Δ F |> F avg × δ At that time, only the beam lowering operation of the synchronous control group to which the over-limit jack belongs is paused, and the jacking force of the over-limit jack is adjusted until the difference returns to within the specified range. Then, the pause is lifted, and synchronous lowering with other groups resumes. F avg This is the arithmetic mean of the jacking forces of all jacks within the synchronous control group. δ The value range is 5% to 15%; Repeat the above steps until all jacks have completed their entire descent.

2. The method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking as described in claim 1, characterized in that, The real-time thrust prediction model calculates the uncorrected bending moment in the following manner. M 0 Theoretical top thrust F t : The model utilizes real-time strain data acquired by the strain sensor at at least the mid-span position and the 1 / 4 span position. ε k ,in k Number the strain sensor; Through formula M 0 = f(ε 1 , ε 2 , …, ε k , E , I Calculate the uncorrected bending moment of the steel truss beam. M 0 ,in, E The elastic modulus of the beam material. I The moment of inertia of the beam section; Through formula F t = g ( M 1 , x , L Calculate the position coordinates. x The theoretical jacking force at the location F t ,in, L The total span of the steel truss beam is given.

3. The method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking as described in claim 1, characterized in that... The steps for adjusting the jacking force of an over-limit jack include: Identify overloaded jacks whose jacking force exceeds the allowable range, and lock the current beam-dropping height of the overloaded jacks; A reverse micro-lift command is sent to the over-limit jack to control the over-limit jack to perform a micro-lifting action in the opposite direction to the beam dropping direction. The stroke ΔH of the reverse micro-lift is in the range of 0.5~1.0mm. After performing the reverse micro-lift action, the jacking force of the over-limit jack is re-acquired through the pressure sensor and compared with the jacking forces of other jacks in the synchronous control group to which the over-limit jack belongs, to determine whether the jacking force difference has recovered to |Δ F |> F avg × δ Within the specified range.

4. The method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking as described in claim 1, characterized in that... After each stage of beam placement is completed, a data verification step is also included: The measured final displacement values ​​of each of the aforementioned jacks D a Based on the modified bending moment M 1 Calculated theoretical displacement values D t Compare the two; if the deviations satisfy | D a - D t |> D th ,in D th If the value range is 1~5mm, then before the next stage of beam lowering begins, a fine-tuning lifting step is added by the jack to reduce the displacement deviation to within 1.5mm before proceeding to the next stage of beam lowering.

5. The method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking as described in claim 1, characterized in that... The steps preceding each stage of beam lowering also include a temperature correction step: Temperature deformation data of the beam is collected by 3 to 5 temperature sensors arranged along the length of the steel truss beam. Based on the temperature deformation data, the formula is used... F c = F t ×(1+ α ×Δ T ) for the theoretical top thrust F t Make corrections, where Δ T This represents the temperature change value. α This is the temperature correction factor. α The value range is 0.5~2% of the theoretical thrust for each temperature change per ℃.

6. The method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking as described in claim 1, characterized in that, It also includes a backup control mode in case of gap sensor malfunction: When the gap sensor signal is detected to be abnormal or lost, the system automatically switches to the backup control mode, suspends the predictive adjustment function at the support point, and enables the guaranteed jacking force control based on a preset safety factor. The guaranteed jacking force is the average jacking force at the support point during the previous stage of beam lowering multiplied by the predetermined safety factor.

7. The method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking as described in claim 1, characterized in that... The distance between two adjacent jacking supports at the beam end supports of the steel truss beam. S e The distance between two adjacent jacking supports in the mid-span region of the steel truss beam is less than the distance between them. S m .

8. The method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking as described in claim 7, characterized in that... During each stage of beam lowering, the execution speed of one downward stroke of the jack located in the beam end support area. V e The execution speed is less than the single drop stroke of the jack located in the mid-span region. V m And the speed difference between the two ( V m - V e ) / V m The value range is 0.15 to 0.

25.

9. The method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking as described in claim 1, characterized in that, After all beam lowering operations are completed, the final elevation collaborative verification and overall adjustment steps will be performed: Measure the final elevation at all jacking points; Calculate the elevation deviation Δ between any two adjacent support points. H f ; If any Δ H f Exceeding the allowed range H lim ,in H lim If the value range is 3~8mm, then a fine-tuning jacking operation is performed on the jacks at the support points where the elevation is too low, and the jacking amount Δ at each support point is... H l The value range is 1~3mm.

10. The method for controlling the staged synchronous lowering of a large-span steel truss beam after multi-point jacking as described in claim 2, characterized in that, After all beam lowering operations are completed, a final verification step based on stress is also included: Collect the final strain data of all strain sensors after the beam is lowered to this stage. ε f ; Based on the final strain data ε f According to the calculation of the uncorrected bending moment M 0 In the same manner, the actual residual bending moments of the steel truss beam at each critical node were calculated. M r ; The actual residual bending moment at each of the key nodes M r Theoretical residual bending moment based on design profile M th Compare, and through | M r - M th Calculate the residual bending moment deviation Δ at each node. M ; When the residual bending moment deviation at any node Δ M Greater than the preset allowable bending moment deviation M all At that time, among them M all The value range is 1% to 3% of the design bending moment. Based on the structural stiffness matrix of the steel truss beam, the residual bending moment deviation Δ is adjusted by simultaneously adjusting the lifting or lowering displacement of multiple jacks. M Reduce to the allowable bending moment deviation M all the following.