Steel bar connecting device for detecting uplift bearing capacity of foundation pile

Abstract

The utility model provides a reinforcing steel bar connecting device for detecting the uplift bearing capacity of a foundation pile, which comprises a connecting unit arranged between a longitudinal bar of a concrete pile and an upper reinforcing steel bar, the connecting unit comprises an upper connecting piece and a lower connecting piece which are connected through a positioning piece, the upper connecting piece and the lower connecting piece both comprise a baffle and an anchorage device which are connected, and the baffle is connected with the anchorage device. And the concrete pile longitudinal bars and the upper reinforcing steel bars are inserted into anchorage devices. The connecting unit is light in weight and convenient and fast to connect with concrete pile longitudinal bars and upper steel bars, a power source, special equipment and professional technicians are not needed, the environmental adaptability is high, and the steel bar connecting time is far shorter than that of a welding connecting method, a mechanical connecting method and a sleeve grouting material connecting method; the connecting unit can be recycled, provides pre-tensile stress, ensures that the reinforcing steel bars of the concrete piles are stressed uniformly and reliably, is suitable for connection of a plurality of longitudinal bars of the concrete piles, and is low in total cost.

Description

Technical Field

[0001] The utility model belongs to the technical field of foundation pile construction, and specifically relates to a steel bar connecting device for detecting the uplift bearing capacity of foundation piles. Background Technique

[0002] The steel bar connection methods mainly include binding and lapping technology, mechanical connection technology, sleeve grouting material connection technology, and steel bar welding connection technology. The main engineering characteristics of the steel bar connection methods in the detection of the bearing capacity of foundation piles are as follows:

[0003] 1. The steel bar connection mainly bears vertical tension, so the binding and lapping connection method cannot be used.

[0004] 2. In the detection of the bearing capacity of each tested pile, it is necessary to connect one or four longitudinal steel bars of the concrete pile. The steel bar connection workload is small. The connected steel bars are embedded in the concrete pile, and it is difficult to thread the steel bar joints. Therefore, the mechanical connection method is not suitable.

[0005] 3. The steel bar connection part is exposed to the environment and is affected by temperature. Especially at negative temperatures, the sleeve grouting material steel bar connection method is not suitable.

[0006] 4. The service time of the steel bar connection is synchronized with the load duration, generally 24-36 hours, and the service time is much shorter than that of the steel bar connection in other structures.

[0007] Based on the above engineering characteristics, in the detection of the bearing capacity of foundation piles, the welding connection method with little influence from the external environment and reliable force is generally adopted for steel bar connection. However, the engineering problems encountered in the welding connection method also restrict the work progress of the detection of the bearing capacity of foundation piles. The main influencing factors are as follows:

[0008] 1. The detection of the bearing capacity of foundation piles is generally carried out in the initial stage of the construction of the construction project. The conditions for introducing power to the foundation pit are insufficient, and there is a lack of technical personnel specialized in welding work.

[0009] 2. The steel bar connection needs to adopt double-sided lap welding, and the lap length of the steel bar is relatively large. After the detection of the bearing capacity of the foundation pile is completed and the loading equipment is removed, the steel bar needs to be cut off, resulting in waste of steel bar connection materials.

[0010] 3. Before loading the foundation pile, the welding connection fails to provide effective pre-tensile stress, and the stress of the steel bar connection is uneven during the loading process of the detection of the bearing capacity of the foundation pile.

[0011] A fixture for vertical uplift static load test of a foundation pile, as disclosed in a Chinese invention patent with the application publication number CN109797785A, includes a support frame disposed above the foundation pile. A driving member is provided on the support frame, and a weight is provided above the driving member. A connecting steel bar passes through the weight in the vertical direction, and an abutting sleeve is fixedly sleeved in the middle of the connecting steel bar. A pair of hoop fasteners are detachably connected to both sides of the foundation pile. A horizontally arranged connecting plate is fixedly provided on the hoop fastener, and support plates are fixedly provided on both sides of the connecting plate. The support plates are arranged vertically and fixedly connected to the hoop fastener. The bottom end of the connecting steel bar passes through the connecting plate, and the abutting sleeve abuts against the connecting steel bar. The hoop fastener arranged around the foundation pile is connected to the upper connecting steel bar.

[0012] In the above prior art, the following problems exist:

[0013] 1. The versatility of this connection method is relatively poor. The size of the hoop fastener needs to be customized according to the cross-sectional size of the foundation pile, and foundation piles with different cross-sectional sizes require hoop fasteners with different specifications;

[0014] 2. Except for precast piles, the cross-sectional shape of the foundation pile is not completely regular. Therefore, even if insertion blocks are provided on the inner side wall of the hoop fastener, vertical slippage of the hoop fastener may still occur, resulting in the failure of the detection work;

[0015] 3. If the hoop fastener is installed too close to the pile top, it is easy to cause cracking of the pile head under the action of the pulling load;

[0016] 4. The insertion block generates local pressure on the local part of the pile body, which may cause cracking of the pile body, and generates tensile force on the hoop fastener in the circumferential direction, which may cause the hoop fastener to break.

[0017] Therefore, how to effectively solve the problems of poor versatility and reliability in the connection between the longitudinal bars of the foundation pile and the upper steel bars, low detection efficiency, low detection quality, high detection cost, and high labor intensity is a technical problem to be solved urgently. Utility Model Content

[0018] In view of the deficiencies in the above background technology, the present utility model proposes a steel bar connection device for detecting the uplift bearing capacity of a foundation pile, which solves the problems of poor versatility and reliability in the connection between the longitudinal bars of the foundation pile and the upper steel bars, low detection efficiency, low detection quality, high detection cost, and high labor intensity.

[0019] The technical solution of the present application is as follows:

[0020] A steel bar connection device for detecting the uplift bearing capacity of a foundation pile includes a connection unit disposed between the longitudinal bars of a concrete pile and the upper steel bars. The connection unit includes an upper connection member and a lower connection member connected by a positioning member. Both the upper connection member and the lower connection member include a baffle and an anchor connected to each other. Both the longitudinal bars of the concrete pile and the upper steel bars are inserted into the anchor.

[0021] Furthermore, bolt holes are provided at both ends of the baffle, and the positioning member includes bolts, and the bolts sequentially pass through the bolt holes of adjacent baffles and are in threaded cooperation with nuts.

[0022] Furthermore, the positioning member includes screw rods, and the screw rods respectively pass through the bolt holes of adjacent baffles and are in threaded cooperation with nuts.

[0023] Furthermore, the nut is a double nut.

[0024] Furthermore, the upper connecting member and the lower connecting member have the same structure.

[0025] Furthermore, the upper connecting member and the lower connecting member are symmetrically arranged.

[0026] Furthermore, the anchor is arranged at the center of the baffle.

[0027] Furthermore, the longitudinal bars of the concrete pile and the upper reinforcement are arranged on the same straight line, and the tensile stress of the upper reinforcement is transmitted to the longitudinal bars of the concrete pile.

[0028] Furthermore, the anchors of the upper connecting member and the lower connecting member are coaxial.

[0029] Furthermore, the width of the baffle is greater than the diameter of the anchor.

[0030] Specific beneficial effects of the present utility model include:

[0031] 1. The connection unit is relatively light in weight, and the connection with the longitudinal bars of the concrete pile and the upper reinforcement is convenient and fast. It does not require power supply, special equipment, and professional technical personnel, has strong environmental adaptability, and the steel bar connection time is much less than that of welding connection method, mechanical connection method, and sleeve grouting material connection method;

[0032] 2. The connection unit can be recycled and provides pre-tensile stress, ensuring uniform and reliable stress of the steel bars of the concrete pile, being applicable to the connection of multiple longitudinal bars of concrete piles, and having a low overall cost;

[0033] 3. The bearing capacity calculation and design method of the connection unit are detailed and clear, ensuring that no damage occurs during the detection of the bearing capacity of the foundation pile;

[0034] 4. The specification of the connection unit is only related to the diameter of the steel bar, and is not affected by the pile diameter and the grade of the longitudinal bar, having strong versatility;

[0035] 5. The bolts, baffles, and anchors used in the connection unit are easily available in the market, do not require special customization and processing, and the manufacturing precision requirements for the connection unit are not high. Description of the Drawings

[0036] To more clearly illustrate the embodiments of the present utility model, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0037] Figure 1 Schematic diagram of the use state of the present invention;

[0038] Figure 2 For Figure 1 Enlarged view at position A in

[0039] Figure 3 Schematic diagram of the connection unit in the present invention;

[0040] Figure 4 Schematic diagram of the baffle and the anchor in the present invention;

[0041] Figure 5 Side view of the connection unit in the present invention.

[0042] Explanation of the reference numerals in the drawings:

[0043] 1. Tested foundation pile; 3. Connection unit;

[0044] 5. Pier; 6. Steel beam;

[0045] 7. Jack; 8. Top plate;

[0046] 31. Longitudinal bars of concrete pile; 32. Upper steel bars;

[0047] 301. Baffle; 302. Anchor;

[0048] 33. Bolt; 34. Nut. Specific embodiments

[0049] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, rather than 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 efforts belong to the scope of protection of the present utility model.

[0050] To explore the steel bar connection method applicable to the bearing capacity detection of reinforced concrete piles, it is first necessary to analyze its engineering characteristics. The main engineering characteristics are as follows:

[0051] 1. The steel bar connection mainly provides vertical tensile stress, so the binding lap joint connection method cannot be used;

[0052] 2. In the bearing capacity test of each inspected pile, it is necessary to connect the longitudinal steel bars of one or four reinforced concrete piles. The amount of steel bar connection work is small. The connected steel bars are embedded in the inspected pile, and it is difficult to thread the steel bar joints. Therefore, the mechanical threading connection method is not suitable.

[0053] 3. During the static load test of the reinforced concrete pile, the steel bar connection part is exposed to the environment and affected by temperature. Especially at negative temperatures, the sleeve grouting material steel bar connection method is not suitable.

[0054] 4. The service time of the steel bar connection is synchronized with the load duration in the bearing capacity test of the reinforced concrete pile, generally 24 to 36 hours, and the service time is much shorter than that of the steel bar connection in other structures.

[0055] Based on the above engineering characteristics, in the bearing capacity test of the reinforced concrete pile, the welding connection method with little influence from the external environment and reliable force is generally adopted for the steel bar connection. However, the engineering problems encountered in the welding connection method also restrict the work progress of the bearing capacity test of the reinforced concrete pile. The main influencing factors are as follows:

[0056] 1. The bearing capacity test of the reinforced concrete pile is generally carried out in the initial stage of the construction preparation of the construction project. The condition of introducing power to the foundation pit is insufficient, and there is a lack of technical personnel specialized in carrying out welding work.

[0057] 2. Double-sided lap welding is required for the steel bar connection. The lap length of the steel bar is relatively large. After the test is completed and the loading equipment is removed, the steel bars need to be cut off, resulting in material waste.

[0058] 3. Before the static load test of the reinforced concrete pile is loaded, the connection between the longitudinal steel bars and the upper steel bars of the inspected pile fails to provide effective pre-tensile stress, and the stress of the steel bar connection is uneven during the loading process of the bearing capacity test of the reinforced concrete pile. This is also the main reason for the failure of the uplift pile or the anchor pile method.

[0059] Example 1. In order to overcome the limitations of the application of the welding connection, according to the engineering characteristics of the steel bar connection in the bearing capacity test of the foundation pile, a steel bar connection device for the uplift bearing capacity test of the foundation pile is proposed, which includes a connection unit 3 arranged between the longitudinal steel bars 31 of the concrete pile and the upper steel bars 32. The connection unit 3 includes an upper connecting piece and a lower connecting piece connected by a positioning piece. Both the upper connecting piece and the lower connecting piece include a baffle 301 and an anchor 302 connected to each other. The longitudinal steel bars 31 of the concrete pile and the upper steel bars 32 are both inserted into the anchor 302, and the anchor 302 is a prior art.

[0060] The usage method of the connection device includes the following steps:

[0061] S1: Select the connection unit 3 according to the diameter and tensile strength of the longitudinal steel bars 31 of the concrete pile;

[0062] S2: Prefabricate the upper steel bars 32 according to the height of the reaction force platform. The upper steel bars 32 are preferably high-strength deformed steel bars.

[0063] S3: Install the connecting unit 3 at the top of the longitudinal steel bars 31 of the concrete pile and at the bottom of the upper steel bars 32 respectively, and conduct the bearing capacity test of the foundation pile.

[0064] S4: After the bearing capacity test of the foundation pile is completed, remove the reaction force platform, the connecting unit 3 of the upper steel bars 32, the upper steel bars 32, and the connecting unit 3 of the longitudinal steel bars 31 of the concrete pile. The connecting unit 3 at the end of the longitudinal steel bars 31 of the concrete pile can be removed by hammering for recycling.

[0065] On the basis of the above embodiment, bolt holes are provided at both ends of the baffle 301. The positioning member includes bolts 33, and the bolts 33 sequentially pass through the bolt holes of adjacent baffles 301 and are in threaded cooperation with nuts 34.

[0066] Specifically, one bolt hole is provided at each end of the baffle 301. The bolt holes are as close as possible to the anchor 302. The anchor 302 is welded or integrally made with the baffle 301. The baffle 301 and the bolts 33 are fixed by nuts 34. The purpose is to ensure the rigid connection between the anchor 302 and the baffle 301, and between the baffle 301 and the bolts 33. By tightening the nuts 34, the bolts 33 generate pre-tensile stress, and the pre-tensile stress is transmitted to the longitudinal steel bars 31 of the concrete pile, as Figure 3 shown.

[0067] Specifically, the nut 34 can also be set as a double nut. Each group of double nuts is arranged on the upper and lower sides of the baffle 301 to enhance the stability of the connecting unit 3.

[0068] On the basis of the above embodiment, the upper connecting member and the lower connecting member have the same structure, and both include a connected baffle 301 and an anchor 302. The anchor 302 is arranged at the center of the baffle 301, and one bolt hole is provided at each end of the baffle 301.

[0069] Specifically, the shape of the baffle 301 can be rectangular, circular, etc.

[0070] On the basis of the above embodiment, the upper connecting member and the lower connecting member are symmetrically arranged.

[0071] On the basis of the above embodiment, the anchor 302 of the upper connecting member and the anchor 302 of the lower connecting member are coaxial. The longitudinal steel bars 31 of the concrete pile and the upper steel bars 32 are arranged on the same straight line, and the tensile stress of the upper steel bars 32 is transmitted to the longitudinal steel bars 31 of the concrete pile.

[0072] Specifically, the design value of the tensile bearing capacity of the upper steel bar 32 is greater than that of the longitudinal steel bar 31 of the concrete pile, that is, the design value of the tensile bearing capacity of the connecting steel bar is greater than that of the connected steel bar.

[0073] Specifically, the total design value of the tensile bearing capacity of the bolt 33 is not less than the design value of the tensile bearing capacity of the connected steel bar.

[0074] Specifically, a bolt hole is provided at each end of the baffle 301, and the total design value of the tensile bearing capacity of the two bolts 33 is not less than the design value of the tensile bearing capacity of the connected steel bar:

[0075] N ≥ F / 2 (1)

[0076] In formula (1), N is the design value of the tensile bearing capacity of a single bolt, with the unit of kN;

[0077] F is the design value of the tensile bearing capacity of the connected steel bar.

[0078] In the uplift test of the bearing capacity of the foundation pile, it is required that the maximum tension provided by the steel bar is 1.2 times the ultimate bearing capacity of the foundation pile. Using the design value in formula (1) has a large safety margin and takes into account the uneven force of the two bolts in the tensile test of the connector.

[0079] On the basis of the above embodiment, the width of the baffle 301 is greater than the diameter of the anchor 302.

[0080] Specifically, as Figure 4 shown, the length of the baffle 301 is:

[0081] L = 2(d1 + d2 + d3 + d A / 2),

[0082] In the formula, d1 is the distance from the edge of the bolt hole to the outer edge of the baffle 301;

[0083] d2 is the diameter of the bolt hole;

[0084] d3 is the distance from the edge of the bolt hole to the outer edge of the anchor 302;

[0085] d A is the outer diameter of the anchor 302.

[0086] Specifically, the shear strength of the baffle 301 is greater than the maximum shear stress exerted on it by the bolt 33. The connecting unit 3 cannot fail before the upper steel bar 32 or the longitudinal steel bar 31 of the concrete pile. The baffle 301 mainly undergoes shear failure, and the shear strength of the baffle 301 is greater than the maximum shear stress exerted on it by the bolt 33:

[0087]

[0088] In the formula, fv is the design value of the shear strength of the baffle 301;

[0089] h is the thickness of the baffle 301;

[0090] d n is the net width of the baffle 301, and d n = d A - d2.

[0091] Specifically, the diameter and grade of the connected steel bars are known. From this, the grades and diameters of the upper steel bars 32 and bolts 33 can be determined, and the corresponding anchor fittings 302 can be selected. The width of the baffle 301 is determined by the outer diameter of the anchor fitting 302 and should not be less than the diameter of the anchor fitting 302; the length, thickness, and steel grade of the baffle 301 are determined by the design value of the bearing capacity of the connection unit 3.

[0092] The technical and economic comparison of the present utility model is shown in Table 1:

[0093] Table 1 Technical and Economic Comparison

[0094]

[0095] Note: ① The connection time refers to the connection time of a single steel bar; ② For the anchor fitting - bolt connection method, the connection cost refers to the cost of the connecting parts used for a single steel bar, including the material cost and cost of the baffle, anchor fitting, and bolt. For the welding connection method, the connection cost mainly includes the electrode material cost, electricity cost, and labor cost, etc.

[0096] Specifically, as Figure 1 shown, a connection unit composed of bolts 33, nuts 34, baffles 301, and anchor fittings 302 is prefabricated; before the foundation pile detection, several vertical concrete pile longitudinal steel bars 2 are exposed at the top of the foundation pile 1 to be detected. There are symmetrically arranged piers 5 on both sides of the foundation pile 1 to be detected. A steel beam 6 is erected on the tops of the two piers 5. A jack 7 is arranged at the middle position of the steel beam 6, and the jack 7 is jacked under the top plate 8. The concrete pile longitudinal steel bar 31 and the upper steel bar 32 are both connected through the connection unit.

[0097] Embodiment 2, as a preferred embodiment, is different from Embodiment 1 in that it includes a connection unit 3 arranged between the concrete pile longitudinal steel bar 31 and the upper steel bar 32. The connection unit 3 includes an upper connector and a lower connector connected through a positioning member. Both the upper connector and the lower connector include a connected baffle 301 and anchor fitting 302. The concrete pile longitudinal steel bar 31 and the upper steel bar 32 are both inserted into the anchor fitting 302. The anchor fitting 302 is a prior art. The positioning member includes a screw rod, and the screw rod respectively passes through the bolt holes of adjacent baffles 301 and is in threaded cooperation with a nut 34.

[0098] Specifically, the nut 34 can be a double nut, and each set of double nuts is arranged on the upper and lower sides of the baffle 301 to enhance the stability of the connecting unit 3.

[0099] The details not described in this utility model are all conventional technical means well known to those skilled in the art.

[0100] The above content shows and describes the basic principle, main features and beneficial effects of this utility model. The above description is only a preferred embodiment of this utility model and is not intended to limit this utility model. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this utility model shall be included in the protection scope of this utility model.

Claims

1. A steel bar connection device for detecting the pull-out bearing capacity of pile foundations, characterized in that: The invention comprises a connection unit (3) arranged between a concrete pile longitudinal reinforcement (31) and an upper reinforcement (32), the connection unit (3) comprising an upper connection member and a lower connection member connected by a positioning member, the upper connection member and the lower connection member both comprising a connected baffle (301) and an anchor (302), the concrete pile longitudinal reinforcement (31) and the upper reinforcement (32) both being inserted into the anchor (302).

2. The steel bar connection device for detecting the pull-out bearing capacity of pile foundation according to claim 1, characterized in that: Bolt holes are provided at both ends of the baffle plate (301), and the positioning member comprises bolts (33). The bolts (33) pass through the bolt holes of adjacent baffle plates (301) in sequence and are threadably matched with nuts (34).

3. The steel bar connection device for detecting the pull-out bearing capacity of pile foundation according to claim 2, characterized in that: The positioning member comprises a screw rod, which passes through the bolt holes of adjacent baffles (301) and is threadably matched with a nut (34).

4. The steel bar connection device for detecting the pull-out bearing capacity of pile foundation according to claim 2 or 3, characterized in that: The nut (34) is a double nut.

5. The steel bar connection device for detecting the pull-out bearing capacity of pile foundation according to any one of claims 1 to 3, characterized in that: The upper connecting member has the same structure as the lower connecting member.

6. The steel bar connection device for detecting the pull-out bearing capacity of pile foundation according to any one of claims 1 to 3, characterized in that: The upper connecting member and the lower connecting member are symmetrically arranged.

7. The steel bar connection device for detecting the pull-out bearing capacity of pile foundation according to any one of claims 1 to 3, characterized in that: The anchor (302) is arranged at the center of the baffle (301).

8. The steel bar connection device for detecting the pull-out bearing capacity of pile foundation according to any one of claims 1 to 3, characterized in that: The anchor (302) of the upper connecting member is coaxial with the anchor (302) of the lower connecting member.

9. The steel bar connection device for detecting the pull-out bearing capacity of pile foundation according to any one of claims 1 to 3, characterized in that: The concrete pile longitudinal reinforcement (31) and the upper reinforcement (32) are arranged on the same straight line.

10. The steel bar connection device for detecting the pull-out bearing capacity of pile foundation according to any one of claims 1 to 3, characterized in that: The width of the baffle (301) is greater than the diameter of the anchor (302).

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