Pre-tensioning method prestress horizontal warehouse ring beam stress-strain monitoring construction method

Abstract

The invention relates to a pre-tensioning method prestress horizontal warehouse ring beam stress strain monitoring construction method, and relates to the field of building prestress construction technology, and the method comprises the following steps: 1, tensioning pedestal construction: taking a prestress ring beam of a square warehouse as a tensioning pedestal; secondly, strain rod diagonal bracings are laid, and strain rods made of metal materials are installed between the tensioning pedestals in a diagonal bracing mode; step 3, tensioning the prestressed steel strand; 4, a stress strain gauge is pasted on the steel square tube; step 5, collecting stress strain gauge data by a background; sixthly, concrete pouring is conducted; and step 7, releasing. The system has the function of monitoring the prestress change state between the prestress ring beams in real time, and building safety can be guaranteed.

Description

Technical Field

[0001] The present application relates to the field of prestressed building construction technology, and in particular to a stress and strain monitoring construction method for prestressed flat warehouse ring beams using a pre-tensioning method. Background Art

[0002] Prestressed concrete refers to a method of pre-stressing concrete components during prefabrication to improve their crack resistance and avoid premature cracks in reinforced concrete components. The method of tensioning steel bars before pouring concrete is called pre-tensioning. The pre-tensioning method is to tension the prestressed tendons before pouring concrete, temporarily anchor the tensioned tendons on a pedestal or steel formwork, and then pour concrete. When the concrete reaches a curing strength of not less than 75% of the concrete design strength and sufficient bonding between the prestressed tendons and concrete is ensured, the tendons are relaxed and prestressed concrete is applied with the help of the bonding between the concrete and the tendons. The pre-tensioning method is generally only applicable to the production of small and medium-sized components and is produced in fixed prefabrication plants.

[0003] Pre-tensioned component production can utilize long-line pedestals, typically ranging in length from 50 to 150 meters, or the assembly line method within steel molds. Pre-tensioned component production involves the pedestal, tensioning equipment and fixtures, and the pre-tensioning process. The pedestal is the primary load-bearing component in pre-tensioned component production and must possess sufficient load-bearing capacity, rigidity, and stability to prevent loss of prestress due to deformation, overturning, or slippage, ensuring the quality of pre-tensioned components.

[0004] During actual construction, the applicant employed an arched slab flat warehouse roof structure with pre-tensioned prestressed arched structural panels. The roof consisted of multiple pre-tensioned arched panels. During the construction of the pre-tensioned ring beam, the concrete-cast ring beam served as a pedestal. Anchor piles were embedded within the ring beam to connect the prestressed iron anchor plates. Prestressed steel bars were then installed and secured, and then concrete for the roof arches was poured. Once the concrete met the design requirements, tension was released.

[0005] In view of the above working conditions, when the pre-tensioning method is directly applied to the construction of roof arch panels, it is impossible to detect the stress changes of the prestressed steel bars in the arch panels after tensioning, and there is no way to directly detect the concrete arch panels. Therefore, the stress conditions of the building arch panels after the construction of the pre-tensioned prestressed flat warehouse ring beams cannot be detected, and the safety of the building structure is not guaranteed. Summary of the Invention

[0006] The present application provides a construction method for monitoring stress and strain of a pre-tensioned prestressed flat warehouse ring beam.

[0007] The present application provides a stress and strain monitoring construction method for prestressed flat warehouse ring beams using the following technical solutions: A construction method for monitoring stress and strain of a pre-tensioned prestressed flat warehouse ring beam, comprising: Step 1: Construction of the tensioning pedestal, using the prestressed ring beam of the square warehouse as the tensioning pedestal; Step 2: Lay the strain rods to support each other, and install the metal strain rods between the tensioning pedestals; Step 3: tensioning the prestressed steel strands; Step 4: Post stress and strain gauges on the steel square tube; Step 5: Collect stress and strain gauge data in the background; Step six, concrete pouring; Step seven, place the card.

[0008] Optionally, step 1, the construction of the tensioning pedestal includes: (1) prefabricating the KB plate and the arch plate forming mold; (2) setting up a rack to form a prefabricated platform, with two horizontal steel pipe supports of the rack, namely the top horizontal steel pipe support and the middle steel pipe support, with the top horizontal steel pipe support spacing of 100mm and the middle steel pipe support spacing of 850mm; (3) during the ring beam casting process, vertical anchor plates for fixing prestressed tendons are embedded in the ring beam; The adjusting bolts at the ends of the horizontal steel pipes of the frame are single with two adjusting bolts, one end on the left and the other on the right, and the adjusting bolts press the ring beam tightly; the longitudinal horizontal steel pipes close to the roof ring beam should make the wooden slats close to the ring beam, and the gaps should be plugged with wooden wedges, and the longitudinal horizontal steel pipes and the transverse horizontal supporting steel pipes should be fastened with double fasteners, so that the wooden wedges, the longitudinal horizontal steel pipes and the transverse horizontal supporting steel pipes can jointly support the horizontal thrust of the roof ring beam.

[0009] Optionally, in step two, multiple strain rods are arranged at equal intervals along the depth direction of the square warehouse; the strain rods are square steel tubes, and the two ends of the strain rods are respectively abutted and fixed to the ring beams on both sides of the flat warehouse.

[0010] Optionally, the spacing between square steel tubes is 1500-1550mm.

[0011] Optionally, step three, prestressed steel strand tensioning, includes: (1) threading prestressed steel bars, fixing both ends of the prestressed steel bars on vertical anchor plates and pre-tensioning them once; (2) dividing and tying the bars, performing post-carpentry work, erecting and installing the arch slab formwork and KB board, and then dividing and tying the bars on the arch slab surface after forming; (3) secondary finishing drawing, with the elongation deviation of the finishing drawing controlled within 6%; (4) pouring the roof arch slab concrete, and removing the arch slab formwork within the specified time after completion.

[0012] Optionally, stress strain gauges are posted on the steel square tube, and the spacing between adjacent strain gauges is 1500-1580mm.

[0013] Optionally, three strain gauges are posted on the steel square tube, and the distance between the edge strain gauge and the ring beam is 350-450mm.

[0014] Optionally, the strain gauge is installed on a vertical plane in the length direction of the steel square tube.

[0015] In summary, this application has the following beneficial technical effects: The present application discloses a construction method for monitoring stress and strain of prestressed ring beams of flat warehouses using the pre-tensioning method. During the construction process of pouring prestressed ring beams and arch panels of flat warehouses, square steel pipes are arranged between the ring beams serving as tensioning pedestals before prestressing construction. The square steel pipes are subjected to prestressing applied by the ring beams simultaneously during the prestressing construction process. After the concrete is formed, strain gauges are installed to monitor stress changes in the square steel pipes, thereby indirectly monitoring changes in prestressing effect of the ring beam on the arch panels and roof parts. This method can assist in real-time monitoring of the prestressing condition of the building and ensure building safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present application; Figure 2 yes Figure 1 Schematic diagram of the top view structure.

[0017] Reference numerals: 1, ring beam; 2, arch plate; 3, lower chord plate; 4, bracing member; 5, strain gauge; 6, data collector. DETAILED DESCRIPTION

[0018] The following is combined with Figure 1-2 This application is described in further detail.

[0019] The present application discloses a method for monitoring the stress and strain of a prestressed flat warehouse ring beam using a pre-tensioning method. Figure 1 ,include: Step 1: Construction of the tensioning pedestal, that is, pouring of prestressed ring beam concrete.

[0020] (1) Prefabricate KB board and arch board formwork; (2) Build a prefabricated platform by laying out the frame. Lay out the construction plane according to the elevation as the arch slab construction plane and the ring beam support plane. The prefabricated platform serves as both the arch slab formwork support frame and the ring beam support frame. Two horizontal steel pipe supports are provided, one for the top layer and one for the middle layer. The spacing between the top layer and the middle layer is @100mm, and @850mm. The thickness of the bottom plate of the arch slab is only 45mm, so the flatness of the platform is very high. The horizontal error of the prefabricated platform surface must be controlled within ±5mm.

[0021] The arch slab's own load is not significant. The dimensions for the lower and middle sections of the steel pipe racks are: 850mm span between vertical poles along the horizontal racks and 850mm span between vertical poles along the vertical racks. The sweeping poles are 200mm above the ground, with a step height of 1600mm. The dimensions for the top section of the steel pipe racks are: 850mm span between vertical poles along the horizontal racks. The vertical support pipes supporting the concrete ring beams are arranged in a row with a span of 100mm. One Φ48×2.8 support pipe is added between the two rib beams.

[0022] Since the ring beam serves as a tensioning pedestal, the following points should be noted during the construction of the rack: ① The adjustment bolts at the ends of the horizontal steel pipes of the rack should be installed with one end on the left and the other on the right. The adjustment bolts should press against the ring beam to make the ring beam a pedestal for the high-altitude pre-tensioning method. ② When the steel pipes are erected, all horizontal rods must be butted together. They should be initially fixed, then the horizontal rods should be squeezed, and finally the fasteners should be tightened a second time. ③ The longitudinal horizontal steel pipes on the edge of the roof ring beam should make the wooden slats close to the ring beam, and the gaps should be plugged with wooden wedges. The longitudinal horizontal steel pipes and the horizontal horizontal support steel pipes should be fastened with double fasteners so that the wooden wedges, longitudinal horizontal steel pipes, and horizontal horizontal support steel pipes can jointly support the horizontal thrust of the roof ring beam.

[0023] (3) Construction measures for the roof ring beam: A 16mm thick vertical anchor plate is used to fix the prestressed tendons on the ring beam. The vertical anchor plate (material Q355) is 400mm high. The diameter of the steel wire hole on the vertical anchor plate is Φ7mm (the fixing bolt hole is Φ25mm), and a 10mm thick trapezoidal stiffening rib is added to the back of the vertical anchor plate. To prevent the concrete at the outer corners of the ring beam from being crushed, a full-length L75×6 angle steel is set according to the design requirements and fixed by welding. The upper part of the angle steel is punched to ensure that the concrete inside the angle steel is dense. Outside the ring beam, pre-buried anchor bolts (M20×320) are set at 90mm on the concrete gutter bottom plate. The spacing corresponds to the anchor plate holes to fix the anchor plate. The exposed thread length of the pre-buried anchor bolts is 55mm-65mm, which is convenient for tensioning the anchor plates and fixing them with nuts at both ends. The use of an improved, new, connected, integral tensioning iron plate eliminates the need for steel tie rods, effectively offsetting tensioning torque and protecting the integrity of the gutter plate. (Older, open-door iron anchor plates require tie rods to prevent instability.) The final ring beam serves as the tensioning pedestal, with pre-buried anchor piles used to connect and shape the tensioning iron anchor plate. Step 2: Lay strain rods to support (to resist prestress); refer to Figure 1 and Figure 2 Square steel tubes are installed between the tensioning pedestals as strain rods. Three strain rods are set equidistantly along the depth direction of the flat warehouse. The spacing between the square steel tubes is 1529mm, and the spacing between the square steel tubes close to the edge of the flat warehouse and the edge of the flat warehouse is 400mm.

[0024] Step 3: Prestressed steel strand tensioning (1) After installing the finalized tensioning iron anchor plate, start inserting the prestressed steel bars, first insert the beam bars and then the bottom plate bars, fix the clips, and perform the initial tensioning at one end. After the tensioning is fixed, proceed with the reinforcement, tying, and then carpentry, erecting and installing the arch plate formwork and KB plate. After the arch plate is formed, proceed with the reinforcement tying on the arch plate surface. After the above procedures are completed, proceed to the next procedure for secondary fine drawing. The elongation deviation of the fine drawing is controlled within 6%. After completion, the roof arch plate concrete is poured within the specified time. After completion, the arch plate formwork is removed within the specified time.

[0025] When pouring the roof ring beam concrete, two groups of test blocks must be made, one group for standard curing and the other group for curing under the same conditions. Prestressed tendons can only be tensioned after the roof ring beam concrete reaches 100% of the target strength.

[0026] The tensioning process is controlled by a dual-control method for prestressing the prestressed steel wires: prestressing is controlled using a prestressing control method, with tensioning elongation used for calibration. Due to the high workload of prestressing the prestressed steel wires, a secondary tensioning process is employed. This is primarily to account for potential prestress losses during construction that were not accounted for in the design, such as deviations from the CNC instrument, temperature effects, and deformation of the pedestal beam. The control stress for prestressing the prestressed steel wires is 5% higher than the design requirement. Under normal circumstances, a median value of approximately 1.099 tons is used (with 28 base plate bars and tie beam bars that can fluctuate 10%-15% above this median value, controlling the stress to approximately 0.9 tons). To facilitate construction, the normal tensioning process is followed, with initial tensioning and secondary finishing drawing. Concrete must be poured within 5-24 hours after the secondary drawing. The initial tensioning force is controlled at approximately 0.6 tons, primarily to facilitate rebar construction and arch formwork installation. Prestressed steel reinforcement requires a minimum of 20% tying. Ties must be kept small, loose, and tight to ensure stability and even distribution of stress during the secondary finishing process. After the secondary finishing process, the integrity and safety of the stress reinforcement must be ensured, and personnel movement must be minimized. During concrete pouring, concrete should be poured first at both ends to demagnetize the stress. Once safety is ensured, pour the concrete sequentially, either bottom-up or top-down (for open-hole casting in the base slab). For thin arch slabs, the tying of the reinforcement above should be controlled at approximately 50% to ensure stability. The requirements for arch plate formwork and demolding are that due to the special nature of the arch plate (convexity and concavity), the formwork can only be removed after the strength meets the specified strength between initial setting and intermediate setting under different temperature conditions (this is the best time for demolding) to ensure that the arch plate is intact and not damaged (at 1℃~10℃, the formwork can be removed after about 36 hours; at about 15℃, the formwork can be removed within 24 hours; at 30℃, the formwork can be removed within 12 hours). The demolding is carried out according to the pouring sequence.

[0027] Step 4: Post stress strain gauges on the steel square tube. Three strain gauges are set on the vertical surface along the length of the steel tube. The distance between the edge strain gauge and the ring beam is 500mm, and the distance between adjacent strain gauges is 1540mm.

[0028] Step 5: The background collects stress and strain gauge data, and uses deep learning to analyze the change pattern of the prestressed steel strand force data to provide real-time feedback on the ring beam deformation and monitor the safety of the concrete ring beam.

[0029] Step six: pouring concrete.

[0030] Concrete can only be poured after quality acceptance and hidden inspection are passed.

[0031] (1) Arch slab roof trusses are thin-walled components that are prefabricated on site and hoisted to high altitude for installation. Dry hard concrete should be used, and the slump of the concrete should be controlled within 1-3 cm according to the design requirements (a moderate slump should be used in actual construction). Commercial concrete should be used, with a small amount of fly ash and a moderate slump.

[0032] (2) Two groups of test blocks are prepared for each shift when pouring concrete, one of which provides a reference for shear reinforcement tensioning, and the test blocks in this group must be cured under the same conditions.

[0033] (3) The pouring sequence is first the lower chord plate, then the upper chord plate. The bottom plate and top plate should be poured symmetrically from both ends to the middle of the span. Each set of roof trusses should be poured in one go, and no construction joints (except for expansion joints) should be left. Use a portable vibrator to vibrate. When operating, lift the vibrator rod and do not vibrate the prestressed reinforcement and formwork with force. Vibrate the junction of the upper and lower chord formwork with the vibrator and then smooth it with a long-handled iron shovel.

[0034] Step seven, place the card.

[0035] After the concrete reaches the design requirements, tensioning is carried out and the end tensioning iron plates are removed.

[0036] Due to the unique characteristics of the arch slab (convexity and concavity), the optimal time for formwork removal is after the concrete reaches the specified initial and intermediate setting strengths, and after the project department issues a formwork removal notice. To ensure the arch slab is not damaged, the order of formwork removal is: first remove the side formwork, then the base plate, to better protect the upper chord arch slab. (Formwork should be removed within 36 hours between 1°C and 10°C, within 24 hours around 15°C, and within 12 hours at 30°C to minimize damage to corners.) After removal, the formwork should be rotated.

[0037] Maintenance and release Immediately after pouring concrete, cover with film and straw bags for curing to prevent shrinkage cracks. It can be opened only when the design strength reaches 100% or more or as required by the designer.

[0038] Prestressed tendon tensioning: The prestressed steel bars of the lower chord of the arch plate can only be relaxed and the inner frame removed after the concrete strength reaches 100%.

[0039] A. Order of placing cards The order of tensioning prestressed tendons shall be carried out in accordance with the following requirements: 1. The prestressed tendons in the area with smaller prestress should be released first, and then the prestressed tendons in the area with larger prestress should be released simultaneously; 2. The tensioning should be carried out in stages, symmetrically and staggered to prevent bending, cracking and rupture of the components and prestressed tendons during the tensioning process.

[0040] B. Release method The prestressed tendons should be released slowly to prevent impact. For this project, the following method can be used: Since the arch is tensioned integrally, 100% release is essential. Release should be performed symmetrically, either toward one side of the center seam or toward the center from the other side.

[0041] The implementation principle of the construction method for monitoring stress and strain in the ring beam of a prestressed bungalow warehouse disclosed in the embodiments of this application is as follows: It is mainly applicable to the construction structure of the lower chord plate of a high-standard bungalow warehouse roof. Conventional square tubes are pre-installed on the roof tensioning ring beam. After the roof prestressed steel bars are tensioned, stress and strain sensors installed on the steel tubes are used to collect deformation data of the square tubes. The data is processed and analyzed based on a deep learning model to obtain high-dimensional characteristics of the square tube stress and strain, thereby realizing the safety monitoring of the structure's tensioning ring beam. Real-time stress and strain monitoring of the prestressed ring beam ensures structural safety.

[0042] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A construction method for monitoring stress and strain of prestressed ring beams of pre-tensioned bungalows, characterized by: include, Step 1: Construction of the tensioning pedestal, using the prestressed ring beam of the square warehouse as the tensioning pedestal; Step 2: Lay the strain rods to support each other, and install the metal strain rods between the tensioning pedestals; Step 3: tensioning the prestressed steel strands; Step 4: Post stress and strain gauges on the steel square tube; Step 5: Collect stress and strain gauge data in the background; Step six, concrete pouring; Step seven, place the card.

2. The stress and strain monitoring construction method for prestressed prestressed ring beam of a flat warehouse according to claim 1, characterized in that: Step 1: Construction of the tensioning pedestal includes: (1) Prefabricate the KB plate and arch plate forming mold; (2) Set up the frame to form a prefabricated platform, and set up two horizontal steel pipe supports of the frame, namely the top horizontal steel pipe support and the middle steel pipe support. The spacing between the top horizontal steel pipe supports is 100mm, and the spacing between the middle steel pipe supports is 850mm; (3) Construction of the ring beam. During the casting of the ring beam, embed the vertical anchor plate for fixing the prestressed tendons in the ring beam; The adjusting bolts at the ends of the horizontal steel pipes of the frame are single with two adjusting bolts, one end on the left and the other on the right, and the adjusting bolts press the ring beam tightly; the longitudinal horizontal steel pipes close to the roof ring beam should make the wooden slats close to the ring beam, and the gaps should be plugged with wooden wedges, and the longitudinal horizontal steel pipes and the transverse horizontal supporting steel pipes should be fastened with double fasteners, so that the wooden wedges, the longitudinal horizontal steel pipes and the transverse horizontal supporting steel pipes can jointly support the horizontal thrust of the roof ring beam.

3. The stress and strain monitoring construction method for prestressed ring beams of flat warehouses according to claim 1 is characterized by: Step 2: multiple strain rods are set at equal intervals along the depth direction of the square warehouse; the strain rods are square steel tubes, and the two ends of the strain rods are respectively fixed to the ring beams on both sides of the flat warehouse.

4. The stress and strain monitoring construction method for pre-tensioned prestressed flat warehouse ring beam according to claim 3 is characterized by: The spacing between square steel tubes is 1500-1550mm.

5. The stress and strain monitoring construction method for pre-tensioned prestressed flat warehouse ring beam according to claim 1 is characterized by: Step 3: prestressed steel strand tensioning, including: (1) threading prestressed steel bars, fixing both ends of the prestressed steel bars on vertical anchor plates and pre-tensioning them once; (2) dividing the bars, tying them, doing carpentry work, erecting and installing the arch slab formwork and KB board, and then dividing and tying the bars on the arch slab surface after forming; (3) secondary fine drawing, with the elongation deviation of the fine drawing controlled at 6%; (4) pouring the roof arch slab concrete, and removing the arch slab formwork within the specified time after completion.

6. The stress and strain monitoring construction method for pre-tensioned prestressed flat warehouse ring beam according to claim 3, characterized in that: Stress strain gauges are posted on the steel square tube, and the spacing between adjacent strain gauges is 1500-1580mm.

7. The stress and strain monitoring construction method for pre-tensioned prestressed flat warehouse ring beam according to claim 6, characterized in that: There are three strain gauges posted on the steel square tube, and the distance between the edge strain gauge and the ring beam is 350-450mm.

8. The stress and strain monitoring construction method for pre-tensioned prestressed flat warehouse ring beam according to claim 7, characterized in that: The strain gauge is installed on a vertical plane in the length direction of the steel square tube.

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