Device and method for keeping bottom plates aligned in hanging basket construction of variable cross-section box girder

Abstract

The invention discloses a variable cross-section box girder hanging basket construction bottom plate alignment maintaining device and an alignment method, and relates to the field of building bridge engineering. The annular supporting plate surrounds the top plate of the concrete beam block which is formed by pouring; supporting plate top fixing bolts are mounted on the annular supporting plate and connected to a concrete beam block top plate; the concrete bottom formwork is mounted at the bottom of the concrete beam block top plate; the bottom plate pressing mold supporting plate is suitable for being upwards and movably connected to the bottom of the concrete bottom formwork in an abutting mode; the electric jack jacking group is upwards propped against the bottom plate pressing die supporting plate; the strain sensor is mounted at the bottom of the bottom plate pressing die supporting plate; and the controller is suitable for controlling the output ends of the electric jack jacking sets to move up and down, so that the technical problems that the bottom plates of the beam blocks cannot be well aligned, the staggering of the bottom plates is formed, and the appearance quality and attractiveness of the bridge are influenced are solved.

Description

Technical Field

[0001] The present invention belongs to the field of construction engineering and is suitable for the cantilever casting construction of variable cross-section concrete or steel-concrete composite beam bridges in bridge engineering. Specifically, it is a device and method for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket. Background Art

[0002] The beam slab mainly adopts the cantilever casting method, that is, the hanging basket construction. Since the hanging basket construction is carried out in segments according to the beam blocks, the bottom surface of the variable cross-section beam block is arc-shaped. During the construction process, due to the influence of various factors such as concrete pouring, vibration during construction, and tensioning, sometimes the bottom plate of the beam block cannot be well aligned, resulting in a step on the bottom plate, which affects the appearance quality and aesthetics of the bridge.

[0003] In the prior art, CN202321325244.8, a device for translating precast beam slabs of a bridge, can jack up the precast beam slabs through the first jack. After reaching a certain height, the pneumatic hydraulic driver pushes the limit plate to push the precast beam slabs into the limit groove for secondary fixation to ensure the stability during jacking and translation; finally, the second jack and the third jack can push the precast beam slabs to align and translate.

[0004] However, this is the docking of precast finished beam slabs, rather than the pouring method; during actual pouring, the change of the bottom beam formwork at the bottom is dynamic, and it is difficult to accurately maintain the bottom beam formwork. And the beam slabs formed by pouring have a good integral effect.

[0005] Therefore, we provide a device and method for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to make up for the deficiencies of the prior art and provide a device and method for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket to solve the above technical problems.

[0007] To solve the above technical problems, the present invention provides the following technical solutions:

[0008] A device for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket includes a hanging basket support;

[0009] Including:

[0010] An annular support plate that surrounds the top plate of the already cast concrete beam block; a fixing bolt for the top of the support plate is installed on the annular support plate and connected to the top plate of the concrete beam block;

[0011] A concrete bottom formwork installed at the bottom of the top plate of the concrete beam block;

[0012] The bottom plate die pressing support plate is adapted to move upward and abut against the bottom of the concrete bottom formwork;

[0013] The electric jack top group abuts upward against the bottom plate die pressing support plate;

[0014] The strain sensor is installed at the bottom of the bottom plate die pressing support plate;

[0015] The controller is adapted to control the up and down movement of the output end of the electric jack top group.

[0016] In a further technical solution, at least four fixing holes are provided at the top end of the annular support plate, and the fixing holes are located on the top plate of the concrete beam block that has been constructed;

[0017] Reserved holes are provided on the top plate of the concrete beam block, and are fixed to the top plate of the concrete beam block by installing the support plate top fixing bolts.

[0018] In a further technical solution, the electric jack top group includes a plurality of electric jacks, and each electric jack is electrically connected to the controller. The electrical connection includes a power connection and a signal connection;

[0019] Each electric jack is connected to the controller through wired communication. The electric jack is started, stopped or lowered by the power supply of the controller, and the controller is connected to the external power supply through a power cord.

[0020] In a further technical solution, the strain sensor is a resistive strain sensor and is bonded to the bottom of the bottom plate die pressing support plate;

[0021] When the bottom plate die pressing support plate deforms, the measurement data of the resistive strain sensor is transmitted to the controller through a signal line. The controller calculates the deformation amount and feeds it back to start or stop the electric jack.

[0022] In a further technical solution, a strain sensor is installed between the output ends of adjacent electric jacks;

[0023] The installation position of the strain sensor is at least more than 5 cm away from the output end of the adjacent electric jack.

[0024] In a further technical solution, an analog switch is included between the controller and the strain sensor; and an independent output button is provided on the controller, and the output button corresponds to the electric jack one by one.

[0025] In a further technical solution, the electric jacks are divided into 4, 6 or 8 groups; at least the two ends of the bottom of the bottom plate die pressing support plate are connected to the output ends of the electric jacks; at least two groups of the strain sensors are provided.

[0026] In a further technical solution, the electric jack and the controller are both installed on the inner bottom wall of the annular supporting plate; limiting plates are separately arranged on both sides of the inner bottom wall of the annular supporting plate;

[0027] The limiting plate at the bottom is hinged to the bottom plate die supporting plate; the output ends of the electric jacks are all set as arc ends; and a hinge interface is arranged at the bottom of the bottom plate die supporting plate, and the output ends of the electric jacks are rotatably connected to the hinge interface.

[0028] An alignment method for a bottom plate alignment device of a variable cross-section box girder hanging basket construction includes the following steps:

[0029] Step 1, according to the designed pouring sequence, the top plate of the concrete beam block is divided into multiple groups for pouring and forming; at least marked as block No. 0, block No. 1 and block No. 2;

[0030] Step 2, starting from block No. 0, four reserved holes need to be reserved at the end top plate of block No. 0 during construction;

[0031] When the pouring construction of block No. 0 is completed, an annular supporting plate processed according to the height of the beam block, the inner wall height of the annular supporting plate extends to the height under block No. 0, which is greater than the lowest output height of the electric jack;

[0032] Step 3, when the construction of block No. 0 is completed and reaches more than 75% of the designed strength, first move the hanging basket and install the concrete bottom formwork of block No. 1, and then install the bottom plate die supporting plate in claim 1;

[0033] The flatness requirement of the annular supporting plate is high. During processing, a spirit level is used for detection. Fixing holes are opened at the top of the annular supporting plate, and it is fixed to the top plate of block No. 0 that has completed construction by using a supporting plate top fixing bolt;

[0034] Step 3, install the electric jack top group and the controller at the bottom of the annular supporting plate, and the power supply of the controller is electrically connected to an external power supply; the bottom plate die supporting plate is installed on the top of the electric jack and tightly presses upward against the concrete bottom formwork;

[0035] A resistive strain sensor is pasted at the bottom of the bottom plate die supporting plate, the wires and signal lines are both connected to the input port of the controller, and multiple groups of strain sensor interfaces are arranged on the controller;

[0036] In the initial state, an electronic bubble is set inside the controller, and the controller adjusts the electronic bubble to be centered; then the controller starts and stops multiple groups of electric jacks to make the bottom plate die supporting plate tightly press the concrete bottom formwork; meanwhile, the strain sensor is set to the initial state and the deformation amount is 0;

[0037] Construction process: During the pouring of concrete on the concrete bottom formwork, the bottom formwork sinks, causing local deformation of the bottom formwork support plate; after the deformation amount is measured by the strain sensor, the data is uploaded to the controller; the controller feeds back to start or stop the corresponding electric jack according to the size of the deformation amount at the position of the strain sensor, so that the concrete bottom formwork returns to its original state and the strain returns to the initial 0 state;

[0038] Step 4: Then install the No. 2 block and No. 3 block. When the bottom height of the concrete beam block roof further decreases, and the maximum lifting height of the electric jack cannot meet the requirement of maintaining the concrete bottom formwork, replace the annular support plate so that the annular support plate has enough space at the bottom height of the concrete bottom formwork to meet the need for further adjustment.

[0039] Compared with the prior art, the following beneficial effects are achieved:

[0040] In the design of the present invention, the concrete beam block roof is poured in the concrete bottom formwork. After forming, the annular support plate is installed around it; multiple groups of electric jacks and strain sensors are installed on the annular support plate. The strain sensor senses the deformation amount of the concrete bottom formwork, and after sensing, transmits the signal to be processed in the controller. After judgment, the output end of the electric jack rises and falls, abutting and driving the bottom formwork support plate to support the concrete bottom formwork, so as to prevent the sinking of the concrete bottom formwork, reduce the probability of the problem that the bottom plate of the beam block cannot be aligned and form a stagger of the bottom plate, and ensure the appearance quality and beauty of the bridge. Description of the Drawings

[0041] Figure 1 Structural schematic diagram of the device for maintaining the alignment of the bottom plate during the construction of the variable cross-section box girder hanging basket of the present invention Figure 1 ;

[0042] Figure 2 Structural sectional view of the device for maintaining the alignment of the bottom plate during the construction of the variable cross-section box girder hanging basket of the present invention;

[0043] Figure 3 For Figure 2 Enlarged view of part A;

[0044] Figure 4 Side view of the alignment device of the present invention;

[0045] Figure 5 Front sectional view of the alignment device of Embodiment 2 of the present invention;

[0046] Figure 6 Connection schematic diagram of the controller, strain sensor and electric jack of Embodiment 2 of the present invention;

[0047] In the figure: 1, hanging basket support; 2, annular supporting plate; 3, top plate of concrete beam block; 4, fixing bolt at the top of the supporting plate; 5, concrete bottom formwork; 6, bottom plate pressing formwork support; 7, strain sensor; 8, controller; 9, fixing hole; 10, electric jack; 11, analog switch; 12, output button; 13, limiting plate; 14, hinge interface. Detailed implementation manners

[0048] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0049] Embodiment 1

[0050] Please refer to Figures 1-4 , a technical solution provided by the present invention, a device for keeping the bottom plate aligned during the construction of a variable cross-section box girder hanging basket, including a hanging basket support 1;

[0051] Including:

[0052] An annular supporting plate 2, the annular supporting plate 2 surrounds the top plate 3 of the already cast concrete beam block; a fixing bolt 4 at the top of the supporting plate is installed on the annular supporting plate 2 and connected to the top plate 3 of the concrete beam block;

[0053] A concrete bottom formwork 5, installed at the bottom of the top plate 3 of the concrete beam block;

[0054] A bottom plate pressing formwork support 6, the bottom plate pressing formwork support 6 is adapted to move upward and abut against the bottom of the concrete bottom formwork 5;

[0055] An electric jack top group, the electric jack top group abuts upward against the bottom plate pressing formwork support 6;

[0056] A strain sensor 7, the strain sensor 7 is installed at the bottom of the bottom plate pressing formwork support 6;

[0057] A controller 8, the controller 8 is adapted to control the up and down movement of the output end of the electric jack top group.

[0058] At least four fixing holes 9 are opened at the top end of the annular supporting plate 2, and the fixing holes 9 are located on the top plate 3 of the already constructed concrete beam block; as Figure 4 Only 2 groups are drawn, and multiple groups are symmetrically arranged.

[0059] A reserved hole is opened on the top plate 3 of the concrete beam block, and is fixed to the top plate 3 of the concrete beam block by installing a fixing bolt 4 at the top of the supporting plate.

[0060] The electric jack set includes a plurality of electric jacks 10, and each electric jack 10 is electrically connected to the controller 8. The electrical connection includes a power connection and a signal connection;

[0061] Each electric jack 10 is connected to the controller 8 through wired communication. The electric jack 10 is powered on and off or lowered through the controller 8, and the controller 8 is connected to an external power supply through a power cord.

[0062] The strain sensor 7 is a resistive strain sensor 7 and is bonded to the bottom of the bottom plate pressing die carrier 6;

[0063] When the bottom plate pressing die carrier 6 deforms, the measurement data of the resistive strain sensor 7 is transmitted to the controller 8 through a signal line. The controller 8 calculates the amount of deformation and feeds it back to start or stop the electric jack 10.

[0064] A strain sensor 7 is installed between the output ends of adjacent electric jacks 10;

[0065] The installation position of the strain sensor 7 is at least more than 5 cm away from the output end of the adjacent electric jack 10.

[0066] As Figure 3 shown, the electric jacks 10 are divided into 4, 6 or 8 groups; at least the two ends of the bottom of the bottom plate pressing die carrier 6 are connected to the output ends of the electric jacks 10; at least two groups of the strain sensors 7 are provided. Each electric jack 10 and the controller 8 have independent power ports. For a system with four electric jacks, it can be numbered as front left, front right, rear left, rear right. For a six-port system, add another group in the middle, and divide it into two parts before and after with the middle of the carrier as the boundary, and distinguish it as front left, front right, middle left, middle right, rear left, rear right.

[0067] If the length of the top plate of the concrete beam block is greater than 5 m, a wider carrier can be used with eight electric jacks and a controller 8. It is numbered in a matrix according to the length of the bottom plate pressing die carrier 6, numbered 11, 12, 21, 22, 31, 32, 41, 42 from left to right and from front to back, and evenly divided according to the length of the carrier. The controller 8 is also divided into four-channel, six-channel, and eight-channel types.

[0068] The controller 8 has multiple groups of strain sensor interfaces, and the numbers can be encoded according to the intervals of the electric jacks, such as front left - front right, front left - rear left, rear left - rear right, etc., or 11 - 12, 12 - 21, 21 - 22, 31 - 32, etc. The number of electric jack channels of the controller 8 needs to correspond to the number of encoded strain sensors.

[0069] An alignment method for an alignment device for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket includes the following steps:

[0070] Step 1: According to the designed pouring sequence, the top plate 3 of the concrete beam block is divided into multiple groups for casting and forming; at least marked as Block 0, Block 1, and Block 2, as shown in reference Figure 2 ; The specific size is the actual casting size, Figure 2 For illustration, the thickness is not necessarily the case.

[0071] Step 2: Starting from Block 0, four reserved holes need to be reserved at the end top plate of Block 0 during construction;

[0072] When the casting construction of Block 0 is completed, the annular supporting plate 2 processed according to the height of the beam block is used. The inner wall height of the annular supporting plate 2 extends to the height below Block 0, which is greater than the minimum output height of the electric jack 10;

[0073] Step 3: When the construction of Block 0 is completed and reaches more than 75% of the designed strength, first move the hanging basket and install the concrete bottom formwork 5 of Block 1, and then install the bottom plate pressing formwork support plate 6 in Claim 1;

[0074] The flatness requirement of the annular supporting plate 2 is high. During processing, a spirit level is used for detection. A fixing hole 9 is opened at the top of the annular supporting plate 2, and it is fixed to the top plate of the completed Block 0 by a supporting plate top fixing bolt 4;

[0075] Step 3: An electric jack top group and a controller 8 are installed at the bottom of the annular supporting plate 2. The power supply of the controller 8 is electrically connected to an external power supply; the bottom plate pressing formwork support plate 6 is installed on the top of the electric jack 10 and tightly presses upward against the concrete bottom formwork 5;

[0076] A resistive strain sensor 7 is pasted at the bottom of the bottom plate pressing formwork support plate 6. The wires and signal lines are both connected to the input port of the controller 8. Multiple groups of strain sensor 7 interfaces are set on the controller 8;

[0077] In the initial state, an electronic bubble is set inside the controller 8, and the controller 8 adjusts the electronic bubble to be centered; then the controller 8 starts and stops multiple groups of electric jacks 10 to make the bottom plate pressing formwork support plate 6 tightly press the concrete bottom formwork 5; at the same time, the strain sensor 7 is set to the initial state, and the deformation amount is 0;

[0078] During the construction process: Since the concrete bottom formwork 5 sinks during the concrete pouring process of the concrete bottom plate, causing local deformation of the bottom plate pressing formwork support plate 6; after the deformation amount is measured by the strain sensor 7, the data is uploaded to the controller 8; the controller 8 feeds back to start and stop the corresponding electric jack 10 according to the size of the deformation amount at the position of the strain sensor 7, so that the concrete bottom formwork 5 returns to its original state, and the strain returns to the initial 0 state;

[0079] Step 4: Then, install Block 2 and Block 3. When the bottom height of the concrete beam block top plate 3 further decreases, and the maximum lifting height of the electric jack 10 cannot meet the requirement of maintaining the concrete bottom formwork 5, replace the annular support plate 2 so that the annular support plate 2 has sufficient space at the bottom height of the concrete bottom formwork 5 to enable further adjustment.

[0080] Embodiment 2

[0081] As Figure 5 and 6 shown, this is another implementation scheme of the present invention. On the basis of Embodiment 1, as Figure 5 shown, both the electric jack 10 and the controller 8 are installed on the inner bottom wall of the annular support plate 2; limit plates 13 are respectively arranged on both sides of the inner bottom wall of the annular support plate 2;

[0082] The limit plate 13 at the bottom is hinged to the bottom plate pressing formwork support 6; the output ends of the electric jacks 10 are all set as arc ends; and a hinge interface 14 is arranged at the bottom of the bottom plate pressing formwork support 6, and the output ends of the electric jacks 10 are rotatably connected to the hinge interface 14.

[0083] As Figure 6 shown, an analog switch 11 is included between the controller 8 and the strain sensor 7; and an independent output button 12 is arranged on the controller 8, and the output buttons 12 correspond to the electric jacks 10 one by one.

[0084] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

[0085] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A device for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket, comprising a hanging basket support (1); It is characterized in that It includes: An annular support plate (2), which is surrounded by the top plate (3) of the cast and formed concrete beam block; a support plate top fixing bolt (4) is installed on the annular support plate (2) and connected to the top plate (3) of the concrete beam block; A concrete bottom formwork (5), which is installed at the bottom of the top plate (3) of the concrete beam block; A bottom plate pressing die support plate (6), which is adapted to move upward and abut against the bottom of the concrete bottom formwork (5); An electric jack top group, which abuts against the bottom plate pressing die support plate (6) upward; A strain sensor (7), which is installed at the bottom of the bottom plate pressing die support plate (6); A controller (8), which is adapted to control the up and down movement of the output end of the electric jack top group.

2. The device for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket according to claim 1, wherein: At least four fixing holes (9) are opened at the top end of the annular support plate (2), and the fixing holes (9) are located on the top plate (3) of the completed concrete beam block; A reserved hole is opened on the top plate (3) of the concrete beam block, and it is fixed to the top plate (3) of the concrete beam block by installing a support plate top fixing bolt (4).

3. A device for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket according to claim 1, characterized in that: The electric jack top group includes a plurality of electric jacks (10), and each electric jack (10) is electrically connected to the controller (8), and the electrical connection includes a power connection and a signal connection; Each electric jack (10) is connected to the controller (8) through wired communication, and the electric jack (10) is started, stopped or lowered by the controller (8) for power supply, and the controller (8) is connected to the external power supply wire through a power cord.

4. A device for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket according to claim 1, characterized in that: The strain sensor (7) is a resistive strain sensor (7), and is bonded to the bottom of the bottom plate pressing die support plate (6); When the bottom plate pressing die support plate (6) deforms, the measurement data of the resistive strain sensor (7) is transmitted to the controller (8) through a signal line, and the controller (8) calculates the deformation amount and feeds it back to the start or stop of the electric jack (10).

5. A device for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket according to claim 1, characterized in that: A strain sensor (7) is installed between the output ends of adjacent electric jacks (10); The installation position of the strain sensor (7) is at least more than 5 cm away from the output end of the adjacent electric jack (10).

6. The device for maintaining the alignment of the bottom slab during the construction of a variable cross-section box girder hanging basket according to claim 1, wherein: An analog switch (11) is included between the controller (8) and the strain sensor (7); and an independent output button (12) is provided on the controller (8), and the output button (12) corresponds to the electric jack (10) one by one.

7. A device for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket according to claim 1, characterized in that: The electric jacks (10) are divided into 4, 6 or 8 groups; at least the output ends of the electric jacks (10) are connected to both ends of the bottom of the bottom plate pressing die support plate (6); at least two groups of the strain sensors (7) are provided.

8. A device for maintaining the alignment of the bottom slab during the construction of a variable cross-section box girder hanging basket according to claim 1, characterized in that: The electric jacks (10) and the controller (8) are both installed on the inner wall of the bottom of the annular support plate (2); limit plates (13) are respectively arranged on both sides of the inner wall of the bottom of the annular support plate (2); The limiting plate (13) located at the bottom is hinged to the bottom plate die pressing plate (6); the output ends of the electric jacks (10) are all set as arc ends; and a hinge interface (14) is arranged at the bottom of the bottom plate die pressing plate (6), and the output ends of the electric jacks (10) are rotatably connected to the hinge interface (14).

9. Alignment method of an alignment device for maintaining the alignment of the bottom plate during the construction of a variable cross-section box girder hanging basket, characterized in that, It includes the following steps: Step 1, according to the designed pouring sequence, the top plates (3) of the concrete beam blocks are divided into multiple groups for casting and forming; At least marked as block No. 0, block No. 1 and block No. 2; Step 2, starting from block No. 0, four reserved holes need to be reserved at the end top plate during construction; When the casting construction of block No. 0 is completed, the annular supporting plate (2) processed according to the height of the beam block, the inner wall height of the annular supporting plate (2) extends to the height below block No. 0, which is greater than the lowest output height of the electric jack (10); Step 3, when the construction of block No. 0 is completed and reaches more than 75% of the designed strength, first move the hanging basket and install the concrete bottom formwork (5) of block No. 1, and then install the bottom plate die pressing plate (6) in Claim 1; The flatness requirement of the annular supporting plate (2) is high. During processing, a spirit level is used for detection. A fixing hole (9) is opened at the top of the annular supporting plate (2), and it is fixed to the top plate of block No. 0 that has been constructed by using the fixing bolt (4) at the top of the supporting plate; Step 3, an electric jack top group and a controller (8) are installed at the bottom of the annular supporting plate (2), and the power supply of the controller (8) is electrically connected to an external power supply; the bottom plate die pressing plate (6) is installed on the top of the electric jack (10) and tightly presses upwards against the concrete bottom formwork (5); A resistive strain sensor (7) is pasted at the bottom of the bottom plate die pressing plate (6), and the wires and signal lines are both connected to the input port of the controller (8), and multiple groups of strain sensor (7) interfaces are arranged on the controller (8); In the initial state, an electronic bubble is set inside the controller (8), and the controller (8) adjusts the electronic bubble to be centered; then the controller (8) starts and stops multiple groups of electric jacks (10) to make the bottom plate die pressing plate (6) tightly press the concrete bottom formwork (5); meanwhile, the strain sensor (7) is set to the initial state and the deformation amount is 0; During the construction process: Since the concrete bottom formwork (5) sinks during the process of pouring concrete on the concrete bottom plate, the bottom plate die pressing plate (6) is locally deformed; after the deformation amount is measured by the strain sensor (7), the data is uploaded to the controller (8); the controller (8) feedbacks to start and stop the corresponding electric jack (10) due to the size of the deformation amount at the position of the strain sensor (7), so that the concrete bottom formwork (5) returns to its original state and the strain amount returns to the initial 0 state; Step 4, then install block No. 2 and block No.

3. When the bottom height of the top plate (3) of the concrete beam block is further reduced, so that the maximum jacking height of the electric jack (10) cannot meet the requirement of maintaining the concrete bottom formwork (5), replace the annular supporting plate (2) so that the annular supporting plate (2) has a height space at the bottom of the concrete bottom formwork (5) to meet the requirement of readjustment.

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