Device for preventing beam end of T beam from cracking after initial tensioning
By designing the beam end movable bottom mold tooling, the shear stress during initial tensioning is concentrated under the support plate, the problem of cracking of the initial tensioning of the prefabricated rear tensioning of the simple-supported T-beam at the rear beam end is solved, and the safety and quality of construction are improved.
Patent Information
- Application Number
- CN202420636847.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-29
- Publication Date
- 2025-03-07
- Estimated Expiration
- 2034-03-29
AI Technical Summary
After the prefabricated, the prefabricated simply supported T-beam is prone to fissure when the bottom web chamfer about 2 cm away from the end of the beam.
A beam end movable bottom mold tooling is designed, including the bottom mold, the movable upper plate, the fixing lower plate and the adjustment bolts. The movable upper plate can be disengaged from the T-beam, and the adjustment bolts concentrate the force under the support plate by fixing the lower plate to prevent cracking of the beam end.
By concentrating the shear stress during initial tensioning below the support plate, cracking at the end of the T beam is effectively prevented and the safety and quality of construction are improved.
Smart Images
Figure CN222571180U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a manufacturing device for a T-beam and belongs to the technical field of bridge construction. Background Art
[0002] As an important part of bridge engineering, prefabricated post-tensioned simply supported T-beam has a huge construction volume. The following common problems are common in the construction process:
[0003] After the initial tensioning of the prefabricated post-tensioned simply supported T-beam, the bottom web chamfer about 2cm away from the beam end has cracking phenomenon. Specific situation: The anti-arch of the bottom formwork of the prefabricated T-beam is set to 40mm. During the initial tensioning, the beam body is arched upward from both ends to the mid-span due to the prestressing action, and the support force at both ends of the beam body increases, and a large shear force is generated at the support points at both ends of the beam body. During the initial tensioning process of the prefabricated T-beam, due to the prestressing action, the beam body is compressed and displaced toward the mid-span (according to actual measurements, the compression amount of the beam body before and after the initial tensioning is 2mm~4mm), and the end of the beam and the bottom formwork have a large friction resistance, resulting in cracking and damage. The steel bars at the end of the prefabricated T-beam are too dense, and it is easy to contact and squeeze with the end formwork when closing the formwork, resulting in displacement of the steel bars at the end of the beam, resulting in a weak point caused by the excessive thickness of the protective layer, making the beam end more prone to cracking. Summary of the invention
[0004] In order to solve the problem of cracking at the bottom web chamfer about 2 cm away from the beam end after initial tensioning, the present invention proposes a movable bottom formwork tooling for the beam end, which has been proven in practice to be able to effectively prevent cracking of prefabricated post-tensioned simply supported T-beams after initial tensioning.
[0005] The technical solution of the present invention:
[0006] A device for preventing the end of a T-beam from cracking after initial tensioning comprises a bottom mold, the end portion of the bottom mold is cut to form a movable upper plate, a fixed lower plate and adjusting bolts are arranged below the movable upper plate, the fixed lower plate is connected to a strip foundation; the adjusting bolts pass through screw holes of the fixed lower plate and are pressed below the movable upper plate.
[0007] Before initial tensioning, the movable upper plate is adjusted to separate from the T-beam by adjusting the bolts.
[0008] The lower plate is fixed into a π shape, with both ends fixed on the strip foundation and screw holes in the middle.
[0009] The length of the movable upper plate is 30cm.
[0010] Beneficial effects of the present invention:
[0011] During the initial tensioning, the movable blocks are removed and the beam body within 30 cm of the end is suspended, thereby concentrating the shear stress generated during the initial tensioning under the support plate to prevent cracking of the beam end.
[0012] By analyzing the causes of common quality defects and safety risks, and taking a problem-oriented approach, based on the idea of "tooling ensures process, process ensures quality, and quality ensures safety", we have developed and designed practical tooling with "stuck, limited, precise, and clever" as the control principles through research and development, forming a complete set of practical tooling and process technology of first positioning → then assisting → then lifting, which is mainly suitable for the construction of prefabricated post-tensioned simply supported T-beams in highway, municipal and railway engineering projects. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 It is a structural schematic diagram of the device. DETAILED DESCRIPTION
[0014] A 30cm long bottom mold movable block is set at the end of the beam. When the initial tension is carried out, the movable block is removed, and the beam body within 30cm of the end is suspended, so that the shear stress generated during the initial tension is concentrated under the support plate to prevent cracking of the beam end. Figure 1 As shown: it includes a movable upper plate 2, a fixed lower plate 3 and an adjusting bolt 4. The movable upper plate 2 is formed by cutting the end portion of the bottom mold; the fixed lower plate 3 is connected to the strip foundation and mainly plays a supporting role; the adjusting bolt 4 connects the movable upper plate 2 and the fixed lower plate 3, and mainly plays a role in adjusting the height of the movable upper plate 2 and transmitting the force on the movable upper plate 2 to the fixed lower plate 3.
[0015] Movable bottom formwork construction process: first install the bottom formwork and the movable upper plate 2, measure and level them, then use the adjusting bolts 4 to support the movable upper plate, pour the T-beam concrete, then remove the side formwork, remove the movable upper plate 2 by adjusting the bolts 4, and then perform prestressing.
[0016] Installation of movable plate: set a transverse support channel steel 2cm lower than the bottom formwork at the end of the movable block, set two bolts with a diameter of φ20mm on the channel steel, and support and fix the movable block with two bolts with a diameter of 20mm before hoisting the bottom web reinforcement.
[0017] Measurement and leveling: Use a level to measure the movable block, and adjust the flatness of the movable block at the beam end by lifting 2 φ20mm bolts. The flatness should be controlled within 2mm.
[0018] Removing the movable block: After the T-beam is prefabricated and the side formwork is removed, the two φ20mm bolts should be loosened in time to allow the movable block at the beam end to fall off.
[0019] Initial prestressing: Initial prestressing can only be carried out after the movable blocks are removed. After the prestressing is completed, check whether there are cracks at the chamfers of the beam ends.
Claims
1. A device for preventing the end of a T-beam from cracking after initial tensioning, comprising a bottom mold, characterized in that: The end portion of the bottom mold is cut to form a movable upper plate (2); a fixed lower plate (3) and an adjusting bolt (4) are arranged below the movable upper plate (2); the fixed lower plate (3) is connected to the strip foundation (5); the adjusting bolt (4) passes through the screw hole of the fixed lower plate (3) and is pressed below the movable upper plate (2); before initial tensioning, the movable upper plate (2) is adjusted by the adjusting bolt (4) to be separated from the T-beam.
2. The device for preventing the end of a T-beam from cracking after initial tensioning according to claim 1 is characterized in that: The lower plate (3) is fixed into a π shape, with both ends fixed on the strip foundation (5), and a screw hole is provided in the middle.
3. The device for preventing the end of a T-beam from cracking after initial tensioning according to claim 1 is characterized in that: The length of the movable upper plate (2) is 30 cm.