Non-grouting welded connecting device for precast pipe pile static load test

Abstract

This utility model provides a grout-free welded connection device for static pull-out load testing of precast pipe piles, comprising: a pile under test, a hollow steel pipe, a support base, a crossbeam, a lifting device, a welding plate, and tensile reinforcement. The support bases are symmetrically arranged on both sides of the pile under test. The crossbeam spans across the pile under test, with both ends fixed to the corresponding support bases. The lifting device is coaxially mounted on the crossbeam above the pile under test. The welding plate is horizontally mounted on the drive end of the lifting device. The hollow steel pipe is coaxially and vertically welded to the end plate of the pile under test. The tensile reinforcement is evenly distributed around the hollow steel pipe and on both sides of the crossbeam, with one end welded to the hollow steel pipe and the other end welded to the corresponding position on the welding plate. This utility model uses a fully welded structure (hollow steel pipe, bent reinforcement, etc.) to replace traditional core-filling grouting, shortening the construction period and reducing costs. Furthermore, the structure is disassembled and recyclable, the pull-out force transmission is stable, and the test data is highly reliable.

Description

Technical Field

[0001] This utility model relates to the field of pipe pile pull-out testing, and in particular to a grout-free welding connection device for static pull-out testing of precast pipe piles. Background Technology

[0002] Prestressed concrete pipe piles have been widely used in pile foundation engineering due to their advantages such as fast construction speed, lower overall cost, and ease of on-site management. They are also increasingly used as tension piles. After the prestressed concrete pipe piles have been driven or completed and the rest period has been met, a static tensile load test is required to detect their vertical tensile ultimate bearing capacity. Furthermore, the tensile friction of the pile is determined by testing the internal forces and deformation of the prestressed concrete pipe pile. The reliability of the tensile testing device directly determines the validity of the data and the safety of the project.

[0003] However, existing technologies have some problems: In the static pull-out load test of prestressed pipe piles, the pull-out static load test equipment using the welded core filling method is often used for testing. This connection method requires pre-embedding reinforced concrete cores before testing (when the test load is >1000kN, the pull-out test technology mainly uses the core filling grouting method). During testing, the pre-embedded steel bars are anchored to the reaction bearing plate above the jack by welding steel bars, and then the jack loading system applies a lifting load to the reaction bearing steel plate. When using this reaction force transmission connection method, since the pipe pile must be filled with concrete before the test, and the concrete curing also requires a certain period (pouring concrete and curing for 14-21 days), the test time is relatively long, which cannot meet the current demand for rapid testing. In addition, to meet the test load (twice the design value), 30% more steel bars and high-grade micro-expansion concrete (C40-C50) are required, increasing the cost of a single pile by more than 40%.

[0004] In summary, traditional pull-out test devices rely on concrete core grouting, which has problems such as long curing period, material waste, and uneven force transmission. At the same time, there are also safety hazards in the existing welding process. If the welding accuracy and firmness cannot be guaranteed, the weld may detach during the test, which will lead to damage to the pipe pile and forced termination of the test, resulting in test failure. Utility Model Content

[0005] In view of this, the purpose of this utility model is to provide a grout-free welded connection device for static pull-out load testing of precast pipe piles. By using a fully welded structure (hollow steel pipe, bent steel bar, etc.) to replace the traditional core filling grouting, the construction period is shortened and the cost is reduced. At the same time, the welded structure can be disassembled and recycled, the pull-out force transmission is stable, and the reliability of the test data is improved.

[0006] The technical solution adopted by this utility model to solve its technical problem is:

[0007] A grout-free welding connection device for static load testing of precast pipe piles is provided, comprising: the pile under test, a hollow steel pipe, a support base, a crossbeam, a lifting device, a welding plate, and tensile reinforcement; the support bases are symmetrically arranged on both sides of the pile under test, and the crossbeam is arranged across the top of the pile under test, with both ends fixed to the corresponding support bases;

[0008] The lifting device is coaxially mounted on the crossbeam above the pile under inspection. The welding plate is horizontally mounted on the drive end of the lifting device and can be moved upward by the lifting device. The hollow steel pipe is coaxially and vertically welded to the end plate of the pile under inspection. The tensile steel bars are evenly distributed around the hollow steel pipe and distributed on both sides of the crossbeam. One end of the tensile steel bar is welded to the hollow steel pipe, and the other end is welded to the corresponding position on the welding plate.

[0009] Preferably, the inner diameter of the hollow steel pipe is larger than the inner diameter of the pile under inspection, and both the inner and outer sides of the lower end of the hollow steel pipe are welded and fixed to the end plate of the pile under inspection.

[0010] Preferably, the hollow steel pipe is a hollow circular steel pipe made of Q235B material, and the thickness and diameter of the hollow steel pipe are designed according to the specifications of the pipe pile and the test load.

[0011] Preferably, when the diameter of the inspected pile is 600mm, the diameter of the hollow steel pipe is 400mm, and the thickness of the hollow steel pipe is 5mm.

[0012] Preferably, the number of tensile steel bars is 10-20, and the tensile steel bars are ribbed steel bars with a diameter of 16mm or 18mm, and are evenly distributed on both sides of the crossbeam.

[0013] Preferably, when the diameter of the pile under test is 600mm and the test load is 1400kN, the number of tensile steel bars is 16 and they are evenly distributed on the side of the hollow steel pipe.

[0014] Preferably, the welding plate is a circular plate, and the diameter of the circular plate is greater than the width of the crossbeam. The upper end of the tensile steel bar is bent to form a bend, which can overlap with the upper surface of the welding plate. The lower end of the tensile steel bar is bent into a "7" shape, and the bending direction is opposite to that of the upper end. The lower end of the tensile steel bar is welded and fixed to the outer circumference of the hollow steel pipe and the upper surface of the pile end plate under inspection.

[0015] Preferably, the upper end of the tensile steel bar is bent at an angle of 30° to 45°, and the lower end is welded to the outer circumference of the hollow steel pipe and the upper surface of the end plate of the pile under inspection.

[0016] Preferably, symmetrical support blocks are arranged on the crossbeams on both sides of the lifting device, and the upper end of the support blocks abuts against the lower surface of the welding plate.

[0017] Preferably, the lifting device is a jack, the axis of which coincides with the axis of the pile under inspection, and the top of the jack is in complete contact with the bottom surface of the welding plate. The support base is a concrete pier, and the crossbeam is a steel beam.

[0018] The beneficial effects of this utility model are:

[0019] The precast pipe pile pull-out static load test device provided by this utility model completely eliminates the traditional core-filling grouting process by using a fully welded force transmission system of hollow steel pipe and tensile steel reinforcement. This significantly shortens the test preparation period from 14-21 days to 1 day, and reduces the cost of a single pile test by more than 40% due to the reduction of micro-expansion concrete, steel reinforcement and curing procedures. The force transmission path of the fully welded structure is direct. Combined with the 30° to 45° bending and welding design of the tensile steel reinforcement and the double-sided full welding process, it ensures stable pull-out force transmission, displacement monitoring accuracy of 0.01mm and significantly improves data reliability. All components of the device can be disassembled, recycled and reused, and avoids the structural damage to the pile body caused by traditional processes. It is efficient, economical and practical. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural diagram of the precast pipe pile pull-out static load test non-grouting welding connection device according to Embodiment 1 of this utility model.

[0021] Figure 2 This is a reference diagram showing the usage status of the precast pipe pile pull-out static load test grout-free welding connection device according to Embodiment 1 of this utility model.

[0022] In the diagram: 1. Pile under inspection; 2. Hollow steel pipe; 3. Tensile steel reinforcement; 4. Support base; 5. Crossbeam; 6. Support block; 7. Lifting device; 8. Welded plate.

[0023] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the present invention in any way, but rather to illustrate the concept of the present invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] Example 1

[0026] like Figure 1 and Figure 2As shown, the precast pipe pile pull-out static load test non-grouting welding connection device includes: the pile under test 1, hollow steel pipe 2, support seat 4, crossbeam 5, jacking device 7, welding plate 8 and tensile steel bar 3; the support seat 4 is symmetrically arranged on both sides of the pile under test 1, and the crossbeam 5 is arranged across the pile under test 1, with both ends fixed to the corresponding support seat 4.

[0027] The lifting device 7 is coaxially mounted on the crossbeam 5 above the pile under inspection 1. The welding plate 8 is horizontally mounted on the drive end of the lifting device 7 and can be moved upward by the pushing of the lifting device 7. The hollow steel pipe 2 is coaxially and vertically welded to the end plate of the pile under inspection 1. The tensile steel bars 3 are evenly distributed around the hollow steel pipe 2 and distributed on both sides of the crossbeam 5. One end of the tensile steel bars 3 is welded to the hollow steel pipe 2, and the other end is welded to the corresponding position of the welding plate 8.

[0028] It should be noted that the symmetrical arrangement of the support base 4 and the crossbeam 5 forms a reaction frame. The lifting device 7 is coaxially installed above the crossbeam 5, and the welded plate 8 at its driving end can be pushed upward. The hollow steel pipe 2 is coaxially welded to the end plate of the pile under test 1. The tensile steel bars 3 are evenly distributed around the steel pipe and welded to the steel pipe and the welded plate 8 at both ends, forming a rigid force transmission chain of "steel pipe-steel bar-welded plate 8". The load transmission efficiency is high and the axial force deviation is small. When the lifting device 7 applies an upward load, the pull-out force is transmitted to the pile under test 1 through the tensile steel bars 3 and the hollow steel pipe 2, realizing the pull-out static load test. The traditional core-filling process is abandoned, which greatly shortens the test preparation cycle, reduces material and construction costs, and the device can be disassembled, recycled and reused. The force transmission path is direct and stable, which improves the reliability of the test data.

[0029] The inner diameter of the hollow steel pipe 2 is larger than the inner diameter of the pile under inspection 1, and the inner and outer sides of the lower end of the hollow steel pipe 2 are welded and fixed to the end plate of the pile under inspection 1.

[0030] It should be noted that by matching the inner diameter, the internal space of the pipe pile is ensured to be unobstructed, so that the central hole of the tested pile 1 is wrapped inside the hollow steel pipe for protection, without affecting the original function of the pile body. At the same time, the double-sided welding on the inner and outer sides forms a ring weld, and the pull-out force is transmitted to the hollow steel pipe 2 through the inner and outer sides of the end plate simultaneously, avoiding welding failure caused by unilateral stress. The double-sided welding doubles the cross-sectional area of ​​the weld, enhances the connection rigidity and strength between the hollow steel pipe 2 and the end plate, avoids the hidden dangers of false welding and missing welding of traditional single-sided welding, and enhances the overall stability of the device.

[0031] The hollow steel pipe 2 is a hollow circular steel pipe made of Q235B material, and the thickness and diameter of the hollow steel pipe 2 are designed according to the specifications of the pipe pile and the test load.

[0032] It should be noted that by utilizing the moderate yield strength and good weldability of Q235B steel, the hollow steel pipe 2 can withstand the corresponding load in the pull-out test without buckling or plastic deformation. Furthermore, the use of common Q235B steel reduces material costs, and the design of the steel pipe parameter lifting device is based on the actual working conditions to avoid material waste. In addition, the circular hollow structure facilitates on-site installation and welding, enhancing the versatility and economy of the device.

[0033] When the diameter of the tested pile 1 is 600mm and the test load is 1400kN, the diameter of the hollow steel pipe 2 is 400mm and the thickness of the hollow steel pipe 2 is 5mm; when the number of tensile steel bars 3 is 16, and the tensile steel bars 3 are ribbed steel bars with a diameter of 18mm, they are evenly distributed on the sides of the hollow steel pipe 2 on both sides of the crossbeam 5.

[0034] It should be noted that, based on the diameter of the tested pile 1 and the design dimensions of the hollow steel pipe 2 for the test load (e.g., when the pile diameter is 600mm, the steel pipe diameter is 400mm and the thickness is 5mm), a force transmission core adapted to the pile body is formed, providing parameter references for standardized design and ensuring the reliability of test data.

[0035] The welding plate 8 is a circular plate, and the diameter of the circular plate is greater than the width of the crossbeam 5. The upper end of the tensile steel bar 3 is bent to form a bend, and the upper bend of the tensile steel bar 3 can overlap with the upper surface of the welding plate 8. The lower end of the tensile steel bar 3 is bent into a "7" shape, and the bending direction is opposite to that of the upper end. The lower end of the tensile steel bar 3 is welded and fixed to the outer circumference of the hollow steel pipe 2 and the upper surface of the end plate of the inspected pile 1.

[0036] It should be noted that by expanding the stress-bearing surface with a circular plate, the welding area of ​​the tensile steel bar 3 extends beyond the edge of the crossbeam 5 to avoid interference, effectively reducing local stress concentration in the welding plate 8. The upper and lower ends of the steel bar are bent to form a three-dimensional welding structure, which increases the weld length, increases the welding contact area, and forms a stable force transmission path, improving the connection stiffness and load transmission uniformity. Furthermore, the upper bent part allows the tensile steel bar 3 to overlap on the upper welding plate 8 during welding, reducing the support force required for the tensile steel bar 3 and reducing the welding difficulty.

[0037] The upper end of the tensile steel bar 3 is bent at an angle of 45°, and the lower end is welded to the outer circumference of the hollow steel pipe 2 and the upper surface of the end plate of the pile under inspection 1.

[0038] It should be noted that by bending the upper end at a specific angle, the load transmission path of the steel bar under tension is made closer to the axial direction, reducing the influence of lateral force components. It also effectively avoids the risk of weld failure caused by unreasonable angle or insufficient welding area at the weld joint of the steel bar, ensuring reliable pull-out force transmission. At the same time, it improves the accuracy of data monitoring during the test and the reusability of the device.

[0039] Support blocks 6 are symmetrically arranged on the crossbeams 5 on both sides of the lifting device 7, and the upper end of the support blocks 6 abuts against the lower surface of the welding plate 8.

[0040] It should be noted that the load applied to the welded plate 8 by the symmetrical support block 6 is shared by the lifting device 7, forming an auxiliary force transmission path of "lifting device 7 - welded plate 8 - support block 6 - crossbeam 5". This disperses the concentrated force on the crossbeam 5, reduces the bending deformation of the crossbeam 5 caused by concentrated force, and at the same time restricts its downward concave deformation by abutting the lower surface of the welded plate 8, ensuring the flatness of the welded plate 8, avoiding test errors caused by eccentric loading, and improving the stability of pull-out force transmission.

[0041] The lifting device 7 is a jack, whose axis coincides with the axis of the pile under inspection 1, and the top of the jack is completely in contact with the bottom surface of the welding plate 8. The support base 4 is a concrete pier, and the crossbeam 5 is a steel beam.

[0042] It should be noted that jacks, concrete supports, and steel beams are common materials, easy to construct, and the entire device can be reused, reducing testing costs.

[0043] The working principle and usage of the precast pipe pile pull-out static load test non-grouting welded connection device in this embodiment:

[0044] The precast pipe pile pull-out static load test grout-free welding connection device provided in this embodiment forms a reaction frame through symmetrically arranged support seats 4 and a transverse beam 5. The lifting device 7 is coaxially installed above the beam 5 and the driving end is connected to a horizontal welding plate 8. The hollow steel pipe 2 is coaxially and vertically welded to the end plate of the pile under test 1. The tensile steel bars 3 are evenly distributed around the hollow steel pipe 2 and welded to the hollow steel pipe 2 and the welding plate 8 at both ends respectively. When the lifting device 7 pushes the welding plate 8 upward, the pull-out force is transmitted to the hollow steel pipe 2 through the bent welding structure of the tensile steel bars 3, and then transmitted to the pile under test 1 through the double-sided welding of the inner and outer sides of the hollow steel pipe 2 and the end plate of the pile under test 1. This forms a fully welded rigid force transmission chain of "reaction frame - lifting device 7 - welding plate 8 - tensile steel bars 3 - hollow steel pipe 2 - pile under test 1". It does not require traditional concrete core grouting and curing processes. The efficient transmission of load in the pull-out static load test is achieved through the welding connection and synergistic effect of each component.

[0045] When in use, first level the ground on both sides of the pile under inspection to prevent the two foundations used to set the support base 4 (concrete support), and place the crossbeam 5 (steel beam) on the support base 4 to form a reaction frame.

[0046] Subsequently, the lifting device 7 (jack) is placed coaxially on the crossbeam 5 directly above the pile under inspection 1, and the welding plate 8 is placed horizontally on the top of the jack piston. At the same time, support blocks 6 are symmetrically set on the crossbeams 5 on both sides of the jack to temporarily support the welding plate 8 and prevent it from shaking.

[0047] Next, clean the surface of the end plate of the pile under inspection 1, and place the hollow steel pipe 2 with the matching inner diameter vertically and coaxially in the center of the end plate. After precise adjustment of the position (adjusting the verticality and horizontality error within ±2mm), use double-sided full welding process to firmly weld and fix its lower end to the end plate of the pile under inspection 1.

[0048] Subsequently, according to the design requirements, a specified number (16) and specification (18mm diameter) of ribbed tensile steel bars 3 are evenly arranged around the hollow steel pipe 2. The lower end of each steel bar is pre-bent into a specific shape (such as a "7") and tightly attached to the outer circumference of the hollow steel pipe 2 and the upper surface of the end plate, and then double-sided full welding is performed for fixation. At the same time, the upper end of the steel bar is bent into a certain angle (45° in the opposite direction to the lower end). The bent part of the upper end of the steel bar is overlapped with the corresponding outer circumference area on the upper surface of the welding plate 8, and the lower end of the tensile steel bar 3 is welded. The entire device is finely adjusted to ensure that the jack, welding plate 8, hollow steel pipe 2 and the pile under inspection are strictly coaxial (axis deviation within ±1mm). It is confirmed that the upper end of the support block 6 is tightly abutting against the lower surface of the welding plate 8 to provide support. At the same time, the upper end of the steel bar is welded and fixed to the outer circumference of the upper surface of the welding plate 8 to form a complete rigid force transmission structure.

[0049] Finally, the load was applied in stages using jacks, and the upward pull-out load was applied in stages according to the specifications (increasing from 200kN to 1400kN per stage, with each stage held for 30 minutes). After each stage of load was applied, the load was kept stable for a period of time. During the loading and holding process, the upward displacement of the tested pile 1 was monitored and recorded synchronously and in real time (usually using a high-precision displacement sensor). The displacement sensor was used to record the data, and the load was continuously applied until the preset termination conditions of the test were reached (such as reaching the maximum test load, the displacement exceeding the allowable value, or pile failure, etc.), thus completing the static pull-out load test.

[0050] Finally, it should be noted that the above description is only a preferred embodiment of this utility model and is used only to illustrate the technical solution of this utility model, and is not intended to limit the protection scope of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model are included within the protection scope of this utility model.

[0051] In the description of this utility model, it should be understood that the terms "upper", "lower", "upper end", "lower end", "upper surface", "lower surface", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0052] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

Claims

1. A grout-free welded connection device for static pull-out load testing of precast pipe piles, comprising: The test pile (1), hollow steel pipe (2), support base (4), crossbeam (5), jacking device (7), welded plate (8), and tensile steel bar (3); the support base (4) is symmetrically arranged on both sides of the test pile (1), and the crossbeam (5) is arranged across the test pile (1) with both ends fixed to the corresponding support base (4); its characteristic is: The lifting device (7) is coaxially mounted on the crossbeam (5) above the pile under inspection (1). The welding plate (8) is horizontally mounted on the driving end of the lifting device (7) and can be moved upward by the lifting device (7). The hollow steel pipe (2) is coaxially and vertically welded to the end plate of the pile under inspection (1). The tensile steel bars (3) are evenly distributed around the hollow steel pipe (2) and distributed on both sides of the crossbeam (5). One end of the tensile steel bars (3) is welded to the hollow steel pipe (2), and the other end is welded to the corresponding position of the welding plate (8).

2. The precast pipe pile pull-out static load test grout-free welding connection device as described in claim 1, characterized in that: The inner diameter of the hollow steel pipe (2) is larger than the inner diameter of the pile under inspection (1), and the inner and outer sides of the lower end of the hollow steel pipe (2) are welded and fixed to the end plate of the pile under inspection (1).

3. The precast pipe pile pull-out static load test grout-free welding connection device as described in claim 2, characterized in that: The hollow steel pipe (2) is a hollow circular steel pipe made of Q235B material. The thickness and diameter of the hollow steel pipe (2) are designed according to the specifications of the pipe pile and the test load.

4. The precast pipe pile pull-out static load test grout-free welding connection device as described in claim 3, characterized in that: When the diameter of the inspected pile (1) is 600mm, the diameter of the hollow steel pipe (2) is 400mm, and the thickness of the hollow steel pipe (2) is 5mm.

5. The precast pipe pile pull-out static load test grout-free welding connection device as described in claim 1, characterized in that: The number of tensile steel bars (3) is 10-20, and the tensile steel bars (3) are ribbed steel bars with a diameter of 16mm or 18mm, and are evenly distributed on both sides of the crossbeam (5).

6. The precast pipe pile pull-out static load test grout-free welding connection device as described in claim 5, characterized in that: When the diameter of the tested pile (1) is 600mm and the test load is 1400kN, the number of tensile steel bars (3) is 16 and they are evenly distributed on the side of the hollow steel pipe (2).

7. The precast pipe pile pull-out static load test grout-free welding connection device as described in claim 1, characterized in that: The welding plate (8) is a circular plate, and the diameter of the circular plate is greater than the width of the crossbeam (5). The upper end of the tensile steel bar (3) is bent to form a bend, and the upper bend of the tensile steel bar (3) can overlap with the upper surface of the welding plate (8). The lower end of the tensile steel bar (3) is bent into a "7" shape, and the bending direction is opposite to that of the upper end. The lower end of the tensile steel bar (3) is welded and fixed to the outer circumference of the hollow steel pipe (2) and the upper surface of the end plate of the inspected pile (1).

8. The precast pipe pile pull-out static load test grout-free welding connection device as described in claim 7, characterized in that: The upper end of the tensile steel bar (3) is bent at an angle of 30° to 45°, and the lower end is welded to the outer circumference of the hollow steel pipe (2) and the upper surface of the end plate of the pile under inspection (1).

9. The precast pipe pile pull-out static load test grout-free welding connection device as described in claim 7, characterized in that: Support blocks (6) are symmetrically arranged on the crossbeams (5) on both sides of the lifting device (7), and the upper end of the support blocks (6) abuts against the lower surface of the welding plate (8).

10. The precast pipe pile pull-out static load test grout-free welding connection device as described in claim 1, characterized in that: The lifting device (7) is a jack, whose axis coincides with the axis of the pile under inspection (1), and the top of the jack is completely in contact with the bottom surface of the welding plate (8). The support base (4) is a concrete support pier, and the crossbeam (5) is a steel beam.

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