Construction method of short embedded cold extrusion lengthening wall tie

Abstract

This invention discloses a construction method for pre-embedded cold-extruded extension of wall tie bars, belonging to the field of building construction technology. The method includes the following steps: S1, pre-embedding tie bars in the main concrete, with the tie bars extending to the outside of the main concrete; the tie bars are made of 6mm diameter HRB400E steel bars; S2, inserting one end of the tie bar located on the outside of the main concrete into a connecting sleeve and connecting it using a hydraulic cold extrusion device; S3, inserting a connecting steel bar into the other end of the connecting sleeve and connecting it using a hydraulic cold extrusion device; the connecting steel bar is also made of 6mm diameter HRB400E steel bar; S4, lapping and binding the connecting steel bar with the tie bars of the infill wall to form a complete connection structure between the infill wall and the main structure. This invention firmly connects the tie bars, connecting sleeve, and connecting steel bars into a single unit through cold extrusion. Pull-out tests show that the sleeve has no cracks, the steel bars have no slippage, the anchorage quality is high, and the seismic and pull-out resistance is stable and reliable.

Description

Technical Field

[0001] This invention belongs to the field of building construction technology, and specifically relates to a construction method for pre-embedded cold extrusion extension of short reinforcing bars in wall tie bars. Background Technology

[0002] Infill wall tie bars are crucial components connecting the main concrete structure (such as frame columns and shear walls) to the masonry infill walls. Their installation quality directly affects the overall seismic performance of the building and the stability of the walls. In current building construction, traditional methods for constructing wall tie bars mainly include long bar pre-embedding, chemical anchoring, and welding of pre-embedded connectors. However, these traditional techniques each have their own insurmountable technical drawbacks in practical applications. 1. The long-reinforcement pre-embedding method requires that long tie bars meeting the specified length requirements be tied and fixed before the main structure concrete is poured, and that these bars be exposed through the main structure formwork. Because the tie bars extend quite far (usually not less than 500 mm), they are prone to jamming during formwork installation, especially during dismantling operations. This not only makes formwork removal extremely difficult and increases the labor intensity for workers, but also often causes rows of wooden formwork to tear mechanically and become unusable, greatly shortening the lifespan of the formwork and significantly increasing construction costs.

[0003] 2. Chemical anchoring, as a post-anchoring technology, requires mechanical drilling, hole cleaning, injection of chemical anchoring adhesive, and insertion of rebar after the main structure has been demolded. This method is highly susceptible to damaging critical main reinforcement bars or stirrups within the main structure during drilling, thus weakening the structure's safety margin. Furthermore, the seismic resistance and pull-out resistance of the anchored rebar fluctuate significantly under complex site conditions. Chemical anchoring adhesives become brittle after seismic disturbances, resulting in a sharp decrease in bonding strength and a tendency for unexpected brittle fracture. Moreover, it commonly suffers from drawbacks during construction and subsequent use, such as the release of toxic gases, aging failure, and poor fire resistance, failing to meet the requirements of modern green building and environmentally friendly construction.

[0004] 3. The embedded part welding method requires on-site welding of long bars on the embedded steel plates or steel bar ends. This process involves a large number of hot work operations at height or in confined spaces. The strong light radiation and welding fumes generated during arc welding operations pose significant health hazards to construction workers. The quality of operation is significantly affected by the skill level of the workers, and on-site open flame operations bring great fire safety hazards to the construction of high-rise buildings.

[0005] Therefore, how to provide a wall tie bar installation and connection scheme that can ensure the quality of tie bar anchorage connection, eliminate safety and environmental hazards, effectively reduce construction operation difficulty, significantly reduce formwork consumption, and is economical and efficient is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] One object of the present invention is to provide a construction method for pre-embedded cold-extruded extension of short reinforcing bars in wall tie bars, comprising the following steps: S1. Tie bars are pre-embedded in the main concrete, and the tie bars extend to the outside of the main concrete. The tie bars are made of HRB400E steel bars with a diameter of 6mm. S2. The end of the tie bar located on the outside of the main concrete is inserted into one end of the connecting sleeve and connected by a hydraulic cold extrusion device; S3. The other end of the connecting sleeve is inserted into the connecting steel bar and connected by a hydraulic cold extrusion device. The connecting steel bar is a 6mm diameter HRB400E steel bar. S4. The connecting steel bars and the tie bars of the infill wall are lapped and tied to form a complete connection structure between the infill wall and the main structure.

[0007] Preferably, the connecting sleeve is made of 20# carbon structural steel, with a length of 35mm, an inner diameter of 8mm, an outer diameter of 11mm, and a wall thickness of 1.5mm. The inner diameter of the connecting sleeve is chosen to be 8mm to facilitate the insertion of the deformed ends of the reinforcing bars after they have been cut by a rebar cutter on the construction site into the sleeve.

[0008] Preferably, the tie bar has a length of 200mm on the inner side of the main concrete and a length of 100mm on the outer side of the main concrete, and is made of 6mm HRB400E steel bar; this type of steel bar has threads, which is beneficial for cold extrusion connection.

[0009] Preferably, the length of the connecting steel bar is ≥600mm.

[0010] Preferably, the length of overlap between the connecting steel bars and the tie bars of the infill wall is 400mm.

[0011] Preferably, the tie bars of the infill wall are HPB300 steel bars (plain round steel bars) with a diameter of 6mm.

[0012] The present invention has the following beneficial effects: This invention pre-embeds short, exposed tie bars of only 100mm in the main concrete structure. When the main formwork is subsequently removed, the exposed short bars will not cause obstruction, effectively preventing the difficulties in demolding and the mechanical tearing and scrapping of wooden formwork caused by traditional long bar pre-embedding, thus extending the service life of the formwork.

[0013] This invention employs pre-embedded and mechanical pressing technology, avoiding damage to the internal main reinforcement or stirrups caused by on-site mechanical drilling. The pre-embedded tie bars, connecting sleeves, and connecting steel bars are firmly connected into one unit using a small hydraulic cold extrusion device. The test tensile force of the connector after pressing can reach 1.11 times the design value of the tensile bearing capacity of 6mm HPB300 steel bars. Furthermore, the pull-out test shows that the connecting sleeve has no cracks, the steel bars have no slippage, the anchoring quality is high, and the seismic and pull-out resistance is stable and reliable.

[0014] This invention avoids the drawbacks of chemical anchoring adhesives, such as the volatilization of toxic gases, easy aging, and poor fire resistance, and meets the requirements of green construction. At the same time, it eliminates the need for on-site open flame high-altitude operations such as electric arc welding, which not only eliminates fire safety hazards at the construction site, but also avoids the health hazards of strong light radiation and welding fumes to construction workers. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the wall tie bar structure in this invention.

[0016] In the diagram: 1. Main concrete; 2. Tie bar; 3. Connecting sleeve; 4. Connecting steel bar; 5. Tie bar for infill wall; 6. Auxiliary steel bar; 7. Infill wall. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] This invention discloses a construction method for pre-embedded cold-extruded extension of short reinforcing bars in wall tie bars. S1: Embed tie bars 2 in the main concrete.

[0019] Before pouring the main concrete 1, two tie bars 2 with a nominal diameter of 6mm are pre-embedded in parallel pairs according to the design, taking into account the horizontal mortar joint height requirements of the infill wall masonry. The main concrete 1 specifically refers to the frame column or shear wall. In this embodiment, the tie bars 2 are 6mm HRB400E steel bars.

[0020] The horizontal and vertical spacing of the two pre-embedded tie bars 2 is precisely positioned using the parallel through holes on the positioning component. The total length of the tie bar 2 is 300mm, of which the anchorage length embedded inside the main concrete 1 is 200mm, and the exposure length extending to the outside of the main concrete 1 is 100mm. The anchorage length meets the requirements of the "Masonry Infill Wall Structure Construction" 22G614-1 drawing set, and also ensures that the exposed short bars will not cause any obstruction when the main formwork is removed later, preventing the phenomenon of tearing the wooden formwork during demolding. S2: One-time extrusion connection.

[0021] After the formwork of the main concrete 1 is removed and before the infill wall is built, the construction workers use a small hydraulic cold extrusion device to insert the exposed tie bar 2 located on the outside of the main concrete 1 into one end of the connecting sleeve 3 up to half the total length of the sleeve. The small hydraulic cold extrusion device is started so that the hydraulic jaws mechanically press the end of the connecting sleeve 3 with the tie bar 2 inserted into it to complete the first extrusion, so that the pre-embedded tie bar 2 and the connecting sleeve 3 are firmly connected as one.

[0022] The connecting sleeve 3 is made of 20# carbon structural steel, with a length of 35mm, an inner diameter of 8mm, an outer diameter of 11mm, and a wall thickness of 1.5mm.

[0023] After crimping, the test tensile strength of the connector can reach 1.11 times the design value of the tensile bearing capacity of 6mm HPB300 steel bars. The inner diameter of the connecting sleeve 3 is selected as 8mm to facilitate the smooth insertion of the steel bar end into the connecting sleeve 3 after deformation when the steel bar is cut by a steel bar cutter on the construction site.

[0024] S3: Secondary extrusion connection.

[0025] One end of a connecting steel bar 4 with a nominal diameter of 6mm and a total length of 600mm is inserted into the uncompressed cavity on the other side of the connecting sleeve 3, which has already undergone one compression. The connecting steel bar 4 is a 6mm HRB400E steel bar.

[0026] The small hydraulic cold extrusion equipment is restarted to press the outer wall of the connecting sleeve 3 on this side, completing the second extrusion. At this point, the tie bar 2, which was originally only 100mm exposed, has been extended by 600mm with high strength through the connecting sleeve 3. Step S4: Overlap and tie with the tie bar 5 of the infill wall.

[0027] When constructing the infill wall, the extended connecting steel bar 4 is laid flat in the horizontal mortar layer of the masonry and horizontally overlapped and tied with the ordinary infill wall tie bar 5 configured in the infill wall to form a strong connection.

[0028] The tie bar 5 in the infill wall is a 6mm HPB300 steel bar as required by the specifications and design.

[0029] The overlap and binding length of the connecting steel bar 4 and the infill wall tie bar 5 is set to 400mm, while the remaining free length of the connecting steel bar 4 without overlap is 200mm, and the ratio of the two lengths is 2:1. Step S5: Vertically lock the auxiliary reinforcing bars.

[0030] Within the length range of the lapped binding of the connecting steel bar 4 and the tie bar 5 of the infill wall, at least three auxiliary steel bars 6 are used for vertical bridging and binding. The auxiliary steel bars 6 are perpendicular to the connecting steel bar 4, which improves the overall shear resistance and external thrust resistance of the infill wall 7 under seismic loads.

[0031] Pull-out test: Clause 9.2.3 of the "Code for Acceptance of Construction Quality of Masonry Structures" (GB50203-2011) specifies a non-destructive bearing capacity test value of 6.0 kN for chemically bonded rebar pull-out tests. This is less than the design tensile bearing capacity of 7.64 kN for 6mm HPB300 rebar. This invention uses the standard yield tensile strength of 8.5 kN for 6mm HPB300 rebar as the non-destructive bearing capacity test value for cold-extruded joints, significantly improving the safety redundancy of wall tie bars. This is because the connected rebar is HRB400, whose design tensile bearing capacity can reach 10.18 kN. The purpose of choosing the 8.5 kN test value is to reduce the wall thickness and length of the sleeve, facilitating the use of smaller extrusion equipment.

[0032] Twenty-seven cold-extruded joint specimens were fabricated using a connecting sleeve and two 6mm HRB400E connecting steel bars. Pull-out tests were conducted according to Clause 9.2.3 of the "Code for Acceptance of Construction Quality of Masonry Structures" GB50203-2011, with 8.5KN as the test value. All 27 tests met the requirements, showing no cracks in the sleeve, no slippage in the steel bars, and no macroscopic damage. The test results are shown in Table 1. Table 1. Record of tensile test results for wall tie bar compression connection 1 8.54 8.15 (Load value reduction not exceeding 5%) none 2 8.52 8.17 (Load value reduction not exceeding 5%) none 3 8.52 8.12 (Load value reduction not exceeding 5%) none 4 8.56 8.2 (Load value reduction not exceeding 5%) none 5 8.5 8.15 (Load value reduction not exceeding 5%) none 6 8.5 8.13 (Load value reduction not exceeding 5%) none 7 8.54 8.15 (Load value reduction not exceeding 5%) none 8 9.04 8.61 (Load value reduction not exceeding 5%) none 9 9.02 8.65 (Load value reduction not exceeding 5%) none 10 8.56 8.19 (Load value reduction not exceeding 5%) none 11 8.52 8.19 (Load value reduction not exceeding 5%) none 12 8.56 8.22 (Load value reduction not exceeding 5%) none 13 8.5 8.11 (Load value reduction not exceeding 5%) none 14 8.52 8.11 (Load value reduction not exceeding 5%) none 15 8.52 8.22 (Load value reduction not exceeding 5%) none 16 8.56 8.18 (Load value reduction not exceeding 5%) none 17 8.54 8.16 (Load value reduction not exceeding 5%) none 18 8.52 8.18 (Load value reduction not exceeding 5%) none 19 8.52 8.12 (Load value reduction not exceeding 5%) none 20 8.54 8.20 (Load value reduction not exceeding 5%) none 21 8.5 8.17 (Load value reduction not exceeding 5%) none 22 8.53 8.15 (Load value reduction not exceeding 5%) none 23 8.52 8.18 (Load value reduction not exceeding 5%) none 24 8.5 8.19 (Load value reduction not exceeding 5%) none 25 8.54 8.15 (Load value reduction not exceeding 5%) none 26 8.5 8.08 (Load value reduction not exceeding 5%) none 27 8.52 8.11 (Load value reduction not exceeding 5%) none The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A construction method of short bar embedded cold extrusion lengthening wall tie, characterized in that, Includes the following steps: S1. Tie bars are pre-embedded in the main concrete, and the tie bars extend to the outside of the main concrete. The tie bars are made of HRB400E steel bars with a diameter of 6mm. S2. The end of the tie bar located on the outside of the main concrete is inserted into one end of the connecting sleeve and connected by a hydraulic cold extrusion device; S3. The other end of the connecting sleeve is inserted into the connecting steel bar and connected by a hydraulic cold extrusion device. The connecting steel bar is a 6mm diameter HRB400E steel bar. S4. The connecting steel bars and the tie bars of the infill wall are lapped and tied to form a complete connection structure between the infill wall and the main structure.

2. The construction method of short-rib embedded cold-extruded lengthened wall tie as claimed in claim 1, wherein, The connecting sleeve is made of 20# carbon structural steel, with a length of 35mm, an inner diameter of 8mm, an outer diameter of 11mm, and a wall thickness of 1.5mm.

3. The construction method for pre-embedded cold-extruded extension of short reinforcing bars in wall tie bars as described in claim 1, characterized in that, The tie bar has a length of 200mm on the inner side of the main concrete and a length of 100mm on the outer side of the main concrete.

4. The construction method for pre-embedded cold-extruded extension of short reinforcing bars in wall tie bars as described in claim 1, characterized in that, The length of the connecting steel bar is ≥600mm.

5. The construction method for pre-embedded cold-extruded extension of short reinforcing bars in wall tie bars as described in claim 1, characterized in that, The length of overlap between the connecting steel bars and the tie bars of the infill wall is 400mm.

6. The construction method for pre-embedded cold extrusion splicing of short reinforcing bars in wall tie bars as described in claim 1, characterized in that, The tie bars for the infill wall are HPB300 steel bars with a diameter of 6mm.

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