A new reinforced concrete cantilever balcony construction structure and construction method

Abstract

The application discloses a kind of newly added reinforced concrete cantilever balcony construction structure and construction method, belong to building construction technical field.Construction structure is based on original reinforced concrete beam, including temporary support component, beam widening reinforcement section, steel bar connecting framework and cantilever balcony board;Temporary support is located in indoor side, by vertical steel pipe and adjustable top support of upper and lower composition;Beam widening reinforcement section is located in original beam indoor side;Steel bar connecting framework includes implanting original column beam newly added longitudinal reinforcement, U-shaped reinforcement welded with original hoop, and anchor into cantilever plate stress reinforcement of widening section;Cantilever balcony board and widening section are integrally poured using micro-expansion concrete.The construction method includes original structure detection, support installation, chisel pretreatment, planting, steel bar binding, integral pouring and detection acceptance.The application realizes that original beam reinforcement and balcony are newly added simultaneously, with anchoring reliable, strong integrity, construction safety, and the advantages such as little damage to original structure.

Description

Technical Field

[0001] This invention belongs to the field of building engineering technology, specifically relating to a construction structure and construction method for a newly added reinforced concrete cantilever balcony. Background Technology

[0002] With the advancement of urban old residential area renovation projects in my country, a large number of old residential buildings built in the 1980s and 1990s are gradually entering the renovation and upgrading stage. These old residential buildings generally have problems such as small unit size, no external balcony, and insufficient functionality. Residents have an urgent need for new external balconies. At the same time, some industrial plants and warehouse buildings also have the need for renovation to add cantilevered operating platforms and storage platforms in order to improve space utilization and production convenience.

[0003] Currently, the main construction technique for adding cantilevered balconies to existing buildings is the direct rebar anchoring method. The core idea of ​​this method is to drill holes on the outside of the existing reinforced concrete beams, inject anchoring adhesive, and then insert the balcony's reinforcing bars into the holes. After the adhesive cures, the balcony's stirrups and distribution bars are tied, and ordinary concrete is poured after formwork is erected to form the cantilevered balcony structure. However, this traditional method has significant technical flaws in practical engineering applications, resulting in numerous safety accidents such as balcony cracking, detachment from the original beam connection, and even complete collapse, posing a serious threat to the lives and property of residents. Specific problems are as follows:

[0004] 1. Poor anchoring reliability, prone to sudden failure.

[0005] The anchoring effect of traditional direct rebar anchoring relies entirely on the bonding strength of the anchoring adhesive. However, the environment of older buildings is often subject to temperature changes, humidity fluctuations, and rain erosion. These factors accelerate the aging and degradation of the anchoring adhesive, leading to gradual debonding between the adhesive, rebar, and concrete. Furthermore, the original concrete beams in older buildings often exhibit some degree of carbonization, resulting in lower adhesion to the borehole walls after drilling, further reducing the anchoring reliability. When balconies are subjected to live loads, wind loads, or seismic forces, the anchored rebars are easily pulled out. This failure is sudden and without clear prior warning, posing an extremely high safety risk. In recent years, several accidents have occurred in various locations involving the complete detachment of balconies added later in older residential areas.

[0006] 2. Failure to simultaneously reinforce the original beams can easily lead to cracking and damage to the original structure.

[0007] The original beam design of the old building only considered the building's self-weight and indoor live load. Adding a cantilevered balcony will bring additional bending moment and shear force to the original beam, causing a sharp increase in local stress. The traditional direct rebar installation method only focuses on the reinforcement layout of the balcony itself, without any reinforcement treatment for the original beam. Under the action of the new load, the original beam is very prone to diagonal cracks, vertical cracks, and even shear failure of the beam. This not only affects the safety of the balcony but also causes irreversible damage to the overall structural safety of the original building.

[0008] 3. Poor overall structural integrity; gaps and leaks easily form at the joint surfaces.

[0009] In traditional construction methods, the new balcony is connected to the original beam only through rebar installation and concrete bonding. There is no effective mechanical interlocking or rigid rebar connection between the two. Under stress, shear stress concentration is prone to occur at the connection surface, leading to cracking of the concrete bonding layer and gaps between the balcony and the original beam. At the same time, the traditional method uses ordinary concrete to pour the balcony. The shrinkage deformation during the concrete hardening process will further widen the gaps at the connection surface. These gaps not only reduce the overall integrity of the structure, but also become channels for rainwater and moisture to penetrate, accelerating the corrosion of the original beam's rebar and the carbonation of the concrete, further reducing the service life of the structure.

[0010] 4. Lack of effective protection during construction may easily damage the original structure.

[0011] In traditional construction methods, the chiseling and drilling operations on the original beams and floor slabs do not involve the use of effective temporary supports. The vibrations and stress release generated during the chiseling process can easily cause micro-cracks in the original floor slabs and beams, and may even lead to deformation and sagging of the original floor slabs, damaging the structural safety of the original building. At the same time, the drilling process can easily damage the original steel bars in the original beams, further reducing the load-bearing capacity of the original beams.

[0012] To address these issues, some existing engineering practices simply increase the number and diameter of rebars, or thicken the balcony's cross-sectional dimensions. However, these methods only improve the balcony's load-bearing capacity to a limited extent and do not fundamentally solve the core defects of "anchoring relying on rebar adhesive, lack of reinforcement of the original beam, and poor structural integrity." The risks of balcony detachment and cracking of the original beam remain. Other practices employ precast balcony slabs, connected to the original beam via embedded parts. However, welding of these embedded parts can easily damage the original beam concrete, and the connection between the precast slab and the original beam lacks integrity, resulting in gaps and leaks. Furthermore, the precast slabs are heavier, placing a greater impact on the original beam's load and increasing construction costs.

[0013] In summary, the existing structures and construction techniques for adding cantilevered balconies to existing buildings suffer from technical problems such as unreliable anchoring, lack of simultaneous reinforcement of the original beams, poor structural integrity, and easy damage to the original structure during construction. These issues no longer meet the safety requirements and usage needs of renovating old residential communities. Therefore, there is an urgent need to develop a novel construction structure and method for adding reinforced concrete cantilevered balconies. This method involves constructing a steel reinforcement frame rigidly connected to the original beams, simultaneously reinforcing the original beams, using an integrated casting process to improve structural integrity, and simultaneously setting up temporary supports to protect the original structure. This approach fundamentally solves the various defects of traditional techniques and meets the safety requirements for adding balconies to old buildings. Summary of the Invention

[0014] The purpose of this invention is to overcome the defects of the prior art and provide a new reinforced concrete cantilever balcony construction structure and construction method, solving technical problems such as anchorage failure, detachment of the balcony from the original beam, and easy cracking of the original beam due to lack of reinforcement caused by the traditional direct rebar installation method.

[0015] The specific technical solution adopted by this invention is as follows:

[0016] A construction structure for a newly added reinforced concrete cantilever balcony is based on the existing reinforced concrete beams of the existing building, including temporary support components, beam widening and reinforcement sections, steel reinforcement connection skeletons and cantilever balcony slabs.

[0017] The temporary support assembly is installed on the indoor side of the original reinforced concrete beam, including a vertical support steel pipe and adjustable top supports respectively installed at the upper and lower ends of the vertical support steel pipe. The upper adjustable top support is pressed against the bottom of the original floor slab, and the lower adjustable top support is supported on the indoor ground.

[0018] The widened and reinforced section of the beam is cast on the indoor side of the original reinforced concrete beam;

[0019] The steel reinforcement connection skeleton includes newly added longitudinal reinforcing bars, U-shaped connecting bars, and cantilever slab reinforcing bars; the two ends of the newly added longitudinal reinforcing bars are inserted into the original reinforced concrete columns; the U-shaped connecting bars are welded and fixed to the original beam transverse stirrups; the inner ends of the cantilever slab reinforcing bars are bent and anchored into the widened and reinforced section of the beam.

[0020] The cantilevered balcony slab is cast on the outdoor side of the steel reinforcement frame, and is integrally cast with the widened and reinforced beam section using the same grade of micro-expansion fine aggregate concrete.

[0021] Preferably, the temporary support components are arranged at equal intervals along the length of the original reinforced concrete beam, with a spacing of 800mm to 1200mm.

[0022] Preferably, the newly added longitudinal reinforcing bars of the beam are hot-rolled ribbed steel bars with a diameter of 16mm to 22mm; the depth to which the newly added longitudinal reinforcing bars of the beam are implanted into the original reinforced concrete column is not less than 15d1, where d1 is the diameter of the newly added longitudinal reinforcing bars of the beam; the newly added longitudinal reinforcing bars of the beam are implanted using epoxy-based building anchoring adhesive, and the bonding strength of the anchoring adhesive is not less than 30MPa.

[0023] Preferably, the U-shaped connecting bars are hot-rolled ribbed steel bars with a diameter of 12mm to 16mm; multiple U-shaped connecting bars are arranged at equal intervals along the length of the original reinforced concrete beam, with a spacing of 150mm to 200mm; the U-shaped connecting bars are connected to the original beam's transverse stirrups by double-sided fillet welding, and the weld leg size is not less than 0.5 times the diameter of the U-shaped connecting bar.

[0024] Preferably, the reinforcing bars of the cantilever slab are hot-rolled ribbed steel bars with a diameter of 12mm to 18mm; the reinforcing bars of the cantilever slab are arranged at equal intervals along the cantilever direction of the balcony, with a spacing of 150mm to 200mm; the length of the reinforcing bars of the cantilever slab anchored into the widened and reinforced section of the beam is not less than 15d2, where d2 is the diameter of the reinforcing bars of the cantilever slab.

[0025] Preferably, the steel reinforcement connection skeleton further includes cantilever slab distribution bars; the cantilever slab distribution bars are hot-rolled plain round steel bars with a diameter of 8mm to 10mm, and their inner ends are implanted into the original reinforced concrete beam by rebar anchoring.

[0026] Preferably, the width of the widened and reinforced section of the beam is 150mm to 250mm, and the height is the same as that of the original reinforced concrete beam; the strength grade of the micro-expansion fine stone concrete is one grade higher than that of the original reinforced concrete beam, the expansion rate is 0.01% to 0.03%, and the coarse aggregate particle size is not greater than 10mm.

[0027] Preferably, the thickness of the cantilevered balcony slab is 100mm to 150mm, and the cantilever length is 1200mm to 2000mm; the slump of the micro-expansion fine aggregate concrete is controlled at 120mm to 140mm.

[0028] Furthermore, the present invention also provides a construction method for a newly added reinforced concrete cantilevered balcony. Based on the above-mentioned construction structure of the newly added reinforced concrete cantilevered balcony, the method includes the following steps:

[0029] S1. Construction preparation and original structure inspection: Determine the design parameters of the cantilever balcony, inspect the concrete strength, reinforcement configuration, carbonation degree and crack condition of the original reinforced concrete beam, assess the bearing capacity of the original structure and determine the size of the beam widening and reinforcement section;

[0030] S2. Temporary support installation: Install temporary support components on the indoor side of the original reinforced concrete beam, tighten the upper adjustable top support to the bottom of the original floor slab, and support the lower adjustable top support to the indoor ground;

[0031] S3. Pre-treatment of the original structure: Local chiseling is carried out at the beam-slab junction and bottom corner of the original reinforced concrete beam to expose the original beam's transverse stirrups. The chiseled surfaces are then roughened, cleaned, rinsed, and dried in sequence.

[0032] S4. Rebar installation and welding: Drill holes at the corresponding positions of the existing reinforced concrete columns, insert the new longitudinal reinforcing bars into the beam and wait for the rebar adhesive to cure; weld the open end of the U-shaped connecting bar to the original beam's transverse stirrups to form a rigid connection node.

[0033] S5. Reinforcement binding: Arrange the reinforcing bars of the cantilever slab and bind them to the newly added longitudinal reinforcing bars of the beam, so that the newly added longitudinal reinforcing bars of the beam, the U-shaped connecting bars and the reinforcing bars of the cantilever slab together form a reinforcement connection skeleton;

[0034] S6. Formwork and integral casting: Set up the casting formwork and seal it to prevent grout leakage. Use micro-expansion fine stone concrete with a strength grade one higher than the original reinforced concrete beam. Cast the widened and reinforced section of the beam and the cantilevered balcony slab in one piece. After casting, water curing shall be carried out for no less than 14 days.

[0035] S7. Support Removal and Inspection: After the concrete strength reaches the design strength, remove the temporary supports and formwork; conduct a visual inspection of the structure, concrete strength test, rebar pull-out test and static load test, and complete the construction after the test is passed.

[0036] Preferably, the integral casting adopts a layered casting method, with a layer thickness of no more than 300mm, and is compacted by using a small vibrator; after the concrete curing is completed, the load-bearing capacity of the balcony is verified to meet the design requirements through a static load test.

[0037] Compared with the prior art, the present invention has at least one of the following advantages or beneficial effects:

[0038] 1. Simultaneously reinforce the original beams and add balconies to prevent cracking of the original structure.

[0039] This invention increases the cross-sectional dimensions of the original beam by setting a widened and reinforced section, thereby improving the original beam's bending and shear bearing capacity. It can effectively bear the additional load brought by the new balcony, fundamentally solving the problem of the original beam being unreinforced and prone to cracking in traditional processes. It also avoids damage to the original structure caused by the new balcony and ensures the structural safety of the original building.

[0040] 2. Rigid steel reinforcement connection significantly improves anchorage reliability.

[0041] This invention abandons the traditional anchoring method that relies solely on rebar adhesive bonding. By welding U-shaped connecting bars to the original beam stirrups, the steel reinforcement frame of the balcony is rigidly connected to the original beam's steel reinforcement system. At the same time, the cantilever slab's load-bearing bars are bent and anchored into the widened section of the beam, forming a triple anchoring effect of steel reinforcement rigid connection + rebar anchoring + concrete bonding. Even if the rebar adhesive ages, the mechanical rigid connection structure can still ensure the balcony's anchoring reliability, effectively avoiding the safety hazard of balcony detachment.

[0042] 3. Integrated casting + micro-expansion concrete, resulting in excellent structural integrity.

[0043] This invention employs an integrated casting process, simultaneously casting the widened section of the beam and the cantilevered balcony slab. It also utilizes micro-expansion fine aggregate concrete, whose expansion deformation offsets the shrinkage deformation of the concrete, resulting in a seamless fit between the balcony and the original beam. This significantly improves the overall structural integrity, avoids gaps and leaks at the connection surface, prevents rainwater and moisture infiltration, and enhances the structure's durability and service life.

[0044] 4. Temporary support and protection ensure safe and reliable construction.

[0045] This invention incorporates temporary support components during construction, which are tightened against the bottom of the original floor slab to counteract vibrations and stress release during the chiseling process. This effectively prevents deformation and cracking of the original floor slab and beams during construction, protects the safety of the original structure, and solves the problem of damage to the original structure caused by traditional construction techniques.

[0046] 5. Simple construction, low cost, and strong adaptability.

[0047] The construction process of this invention adopts conventional building construction equipment and technology, without the need for prefabricated components. Steel bar processing, welding and pouring can be completed on site, resulting in high construction efficiency and low cost. At the same time, the structure is adaptable to original beams with different cross-sections, and the reinforcement and beam widening dimensions can be flexibly adjusted according to the load of the balcony. It is suitable for the addition and renovation of balconies or operating platforms in various existing buildings such as old residential buildings, industrial plants, and warehouse buildings, and has broad engineering application prospects. Attached Figure Description

[0048] Figure 1 This is a front view of the newly added reinforced concrete cantilever balcony construction structure in this embodiment of the invention;

[0049] Figure 2 This is a cross-sectional view of the newly added reinforced concrete cantilever balcony construction structure in this embodiment of the invention;

[0050] Figure 3 This is a top view of the steel reinforcement connection skeleton in an embodiment of the present invention;

[0051] Figure 4This is a bottom view of the steel reinforcement connection skeleton in an embodiment of the present invention;

[0052] Figure 5 This is a schematic diagram of the installation of the temporary support component of the present invention.

[0053] In the diagram: 1. Existing reinforced concrete beam; 11. Original beam transverse stirrups; 12. Existing reinforced concrete column; 13. Existing floor slab; 2. Temporary support components; 21. Vertical support steel pipe; 22. Adjustable top support; 3. Integrated steel reinforcement connection skeleton; 31. Newly added longitudinal reinforcement in the beam; 32. U-shaped connecting bars; 33. Cantilever slab reinforcement; 34. Cantilever slab distribution bars; 4. Beam widening and reinforcement section; 5. Cantilever balcony slab. Detailed Implementation

[0054] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "vertical," and "lateral," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention 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 the invention. The parameters of each component of this invention can be flexibly adjusted according to the actual engineering load and the original structural conditions. The core design concept is rigid steel reinforcement, synchronous beam reinforcement, integral casting, and temporary support protection. All structural improvements based on this concept fall within the protection scope of this invention.

[0056] Example 1:

[0057] like Figures 1-5 As shown, this embodiment provides a construction structure for a newly added reinforced concrete cantilever balcony, based on the existing reinforced concrete beam 1 of the existing building, including a temporary support component 2, a beam widening and reinforcement section 4, a steel reinforcement connection skeleton and a cantilever balcony slab 5.

[0058] Temporary support component 2 is a temporary protective structure for protecting the original structure during construction. It is set on the indoor side of the original reinforced concrete beam 1 and includes a vertical support steel pipe 21 and adjustable top supports 22 respectively set at the upper and lower ends of the vertical support steel pipe 21. The upper adjustable top support 22 is tightened against the bottom of the original floor slab 13, and the lower adjustable top support 22 is supported on the indoor ground. The vertical support steel pipe 21 is made of Φ48×3.5 scaffolding steel pipe and is arranged at equal intervals along the length of the original reinforced concrete beam 1 with a spacing of 800mm to 1200mm. The tightening force is controlled at 5kN to 10kN to offset the vibration and stress release during the chiseling operation, prevent the original floor slab and beam from deforming and cracking, and protect the construction safety of the original structure.

[0059] The aforementioned widened and reinforced section 4 is located on the indoor side of the original reinforced concrete beam 1, with a width of 150mm to 250mm and a height consistent with that of the original reinforced concrete beam 1. Its interior is filled with micro-expansion fine stone concrete of a higher strength grade than that of the original reinforced concrete beam 1, which encloses the steel reinforcement connection skeleton and fits tightly against the chiseled surface of the original reinforced concrete beam 1.

[0060] It should be noted that before pouring the widening and reinforcement section 4 of the beam, the original structure is pre-treated: at the beam-slab junction of the original reinforced concrete beam 1, a local concrete protective layer is chipped away to a depth of 20mm to 30mm to expose the original beam's transverse stirrups 11; at the bottom corner of the beam, a local concrete is chipped away to a depth of 15mm to 25mm to provide space for the reinforcement arrangement of the beam widening section; the floor slab is partially penetrated at the corresponding location while retaining the original reinforcement to avoid damaging the original floor slab's load-bearing system; the surface of the original beam after chipping is roughened using an angle grinder to form a chipped surface, enhancing the bond between the new and old concrete.

[0061] The widened and reinforced section 4 of the beam not only provides a reliable anchorage foundation for the reinforcing bars 33 of the cantilever slab, but also increases the cross-sectional dimensions of the original beam, improving the original beam's bending and shear bearing capacity. It can effectively bear the additional load brought by the new balcony and prevent the original beam from cracking and deforming.

[0062] The steel reinforcement cage is the core steel reinforcement structure that enables the rigid connection between the new balcony and the original beam. It includes the newly added longitudinal reinforcing bars 31, U-shaped connecting bars 32, cantilever slab reinforcing bars 33, and cantilever slab distribution bars 34. The newly added longitudinal reinforcing bars 31 have a diameter of 16mm to 22mm and are arranged along the length of the beam. Both ends are embedded into the reinforced concrete columns of the original building to a depth of not less than 15d1 (d1 is the diameter of the newly added longitudinal reinforcing bars 31). They are bonded and fixed to the column concrete with epoxy-based anchoring adhesive to bear the beam end bending moment generated by the balcony load and improve the bending bearing capacity of the original beam. The U-shaped connecting bars 32 have a diameter of 12mm to 16mm and are arranged at equal intervals along the length of the original reinforced concrete beam 1, with a spacing of 150mm to 200mm. The open end of the U-shaped connecting bars 32 is welded to the transverse stirrups 11 of the original beam using double-sided fillet welding, with the weld leg size not less than 0.5 times the diameter of the bar. The cantilevered section of the U-shaped connecting bars 32 extends to form the transverse stirrups of the cantilevered balcony slab 5, rigidly connecting the balcony steel reinforcement skeleton with the original beam steel reinforcement system to achieve uniform load transfer. The cantilever slab reinforcing bars 33 have a diameter of 12mm to 18mm and are arranged at equal intervals along the cantilever direction of the balcony, with a spacing of 150mm to 200mm. The inner end of the cantilever slab reinforcing bars 33 is bent at 90° and anchored into the beam widening and strengthening section 4, with an anchorage length of not less than 15d2 (d2 is the diameter of the cantilever slab reinforcing bars 33), and is tied and fixed to the reinforcing bars of the beam widening and strengthening section 4 to bear the tensile load of the balcony slab, avoiding the traditional process that relies solely on the single anchorage method of bar planting. The diameter of the cantilever slab distribution reinforcement 34 is 8mm to 10mm. It is arranged vertically along the cantilever slab main reinforcement 33 with a spacing of 200mm to 250mm. The inner end of the cantilever slab distribution reinforcement 34 is inserted into the original beam by means of rebar anchoring to fix the position of the cantilever slab main reinforcement 33 and improve the overall integrity of the cantilever slab.

[0063] The cantilevered balcony slab 5 is a cantilevered slab structure cast outside the reinforced concrete frame, with a thickness of 100mm to 150mm and a cantilever length of 1200mm to 2000mm. It is integrally cast using micro-expansion fine aggregate concrete of the same grade as the beam widening and strengthening section 4. The expansion rate of the micro-expansion fine aggregate concrete is 0.01% to 0.03%, the coarse aggregate particle size is no greater than 10mm, and the slump is controlled at 120mm to 140mm. The integral casting process makes the beam widening and strengthening section 4 and the cantilevered balcony slab 5 form a seamless integrated structure. The micro-expansion concrete can offset shrinkage deformation, avoid gaps at the connection surface, and significantly improve the overall structural integrity and waterproof performance.

[0064] This embodiment applies the above structure to the renovation project of adding balconies in an old town residential building. The building is a brick-concrete structure residential building built in 1995. The original reinforced concrete beam 1 is a C30 reinforced concrete rectangular beam with a cross-sectional dimension of 250mm × 500mm. The new balcony is a utility balcony with a design live load of 2.5kN / ㎡ and a cantilever length of 1500mm. After testing, the concrete strength of the original beam meets the requirements, but the load-bearing capacity is insufficient. Therefore, a beam widening and reinforcement section 4 is set.

[0065] The specific parameters for this embodiment are as follows:

[0066] Temporary support components: The vertical support steel pipes are Φ48×3.5 scaffolding steel pipes, arranged at 1000mm intervals along the beam length, with a total of 4 pipes; the upper adjustable top support has a tightening force of 8kN, and the lower adjustable top support is supported on the indoor ground.

[0067] Pre-treatment of the original structure: chisel to a depth of 25mm to expose the original beam's transverse stirrups; partially break through the floor slab while retaining the original reinforcing bars, and roughen the chiseled surface.

[0068] Reinforcing steel connection skeleton: The beam has 2 new longitudinal reinforcing bars with a diameter of 18mm, which are embedded 270mm into the original column; 10 U-shaped connecting bars with a diameter of 12mm and a spacing of 150mm; the cantilever slab has reinforcing bars with a diameter of 14mm, a spacing of 150mm, and an anchorage length of 210mm; the cantilever slab has distribution bars with a diameter of 8mm and a spacing of 200mm.

[0069] The beam widening and reinforcement section is 200mm wide and 500mm high, and is made of C35 micro-expansion fine stone concrete with an expansion rate of 0.02%.

[0070] Cantilevered balcony slab: 120mm thick, cast in one piece, slump 130mm.

[0071] Testing revealed that the structural connection surfaces of this embodiment are seamless and crack-free, and the concrete strength meets the standards; the ultimate bearing capacity of the balcony is three times the design value, and the bearing capacity of the original beam is increased by 35%; after six months of use, there is no deformation or cracking, meeting the requirements for residential use.

[0072] Example 2

[0073] This embodiment is basically the same as Embodiment 1, except that the newly added reinforced concrete cantilevered balcony construction structure is applied to the renovation project of the cantilevered operating platform in the machine shop. The original reinforced concrete beam is a C25 reinforced concrete rectangular beam with a cross-sectional dimension of 300mm × 600mm; the new operating platform is designed with a live load of 5.0kN / ㎡ and a cantilever length of 2000mm. Testing revealed that the original beam's concrete strength was insufficient and its carbonation depth was 5mm, necessitating the installation of a larger beam to widen and reinforce the section.

[0074] The specific parameters for this embodiment are as follows:

[0075] Temporary support components: Vertical support steel pipes are arranged at 800mm intervals along the beam length, with a total of 5 pipes; the upper adjustable top support has a tightening force of 10kN.

[0076] Pre-treatment of the original structure: chisel to a depth of 30mm to expose the original beam's transverse stirrups, and roughen the chiseled surface.

[0077] Reinforcing steel connection skeleton: The beam has 3 new longitudinal reinforcing bars with a diameter of 22mm, which are embedded 330mm into the original column; the U-shaped connecting bars have a diameter of 16mm and a spacing of 150mm, totaling 13 bars; the cantilever slab has reinforcing bars with a diameter of 18mm, a spacing of 150mm, and an anchorage length of 270mm; the cantilever slab has distribution bars with a diameter of 10mm and a spacing of 200mm.

[0078] The beam widening and reinforcement section is 250mm wide and 600mm high, and is made of C30 micro-expansion fine stone concrete with an expansion rate of 0.03%.

[0079] Cantilevered balcony slab: 150mm thick, cast in one piece, slump 120mm.

[0080] Testing showed that the load-bearing capacity of the original beam was increased by 45% in this embodiment, and the ultimate load-bearing capacity of the operating platform was 2.5 times the design value; the connection between the platform and the original beam was seamless and leak-free; after 12 months of use, there was no deformation or cracking, meeting the requirements for factory production operations.

[0081] Example 3:

[0082] This embodiment provides a construction method for a newly added reinforced concrete cantilever balcony for the above-mentioned structure, including the following steps:

[0083] S1. Construction preparation and original structure inspection: Based on the balcony design load and cantilever length, determine the cross-section, reinforcement and concrete strength parameters; inspect the concrete strength, reinforcement configuration, carbonation and crack conditions of the original beams and columns, assess the bearing capacity and determine the size of the beam widening and reinforcement section.

[0084] S2. Temporary support installation: Install temporary support components on one side of the existing reinforced concrete beam indoors. Vertical support steel pipes are arranged at equal intervals along the beam length. The upper adjustable top support is tightened to the bottom of the existing floor slab, and the lower adjustable top support is supported on the indoor ground to ensure that the original beam and slab do not deform during construction.

[0085] S3. Pre-treatment of original structure chiseling: Local chiseling is carried out at the junction of beam and slab and the bottom corner of beam to expose the original beam's transverse stirrups; the floor slab is partially penetrated while the original steel reinforcement is retained; the chiseled surface is roughened, cleaned, rinsed and dried.

[0086] S4. Installation of longitudinal reinforcement bars and welding of U-shaped connecting bars: Drill holes at the corresponding locations of the existing reinforced concrete columns, clean the dust from the holes, inject epoxy-based anchoring adhesive, and insert the new longitudinal reinforcement bars into the beam; after the anchoring adhesive has cured, perform pull-out tests to ensure that the design requirements are met. Fix the open end of the U-shaped connecting bar to the original transverse stirrups of the beam using double-sided fillet welds, ensuring that the weld is full and defect-free, forming a rigid connection joint.

[0087] S5. Reinforcement binding of cantilever slab: Arrange the main reinforcement of the cantilever slab and bend its inner end to anchor it into the widened section of the beam, and bind it to the newly added longitudinal main reinforcement of the beam; arrange the distribution reinforcement of the cantilever slab and fix its inner end with reinforcement to form a complete reinforcement connection skeleton.

[0088] S6. Formwork and Integrated Casting: Formwork shall be erected according to the dimensions of the widened beam section and the cantilevered balcony slab, and sealant shall be used to prevent grout leakage, ensuring the formwork support system is firm and stable. Micro-expansion fine aggregate concrete with a strength grade one higher than the original reinforced concrete beam shall be used. The widened and reinforced beam section and the cantilevered balcony slab shall be cast in layers, with each layer not exceeding 300mm in thickness, and compacted by vibration. After casting, water curing shall be carried out for no less than 14 days.

[0089] S7. Support Removal and Inspection: After the concrete strength reaches 100% of the design strength, remove the temporary supports and formwork; conduct a visual inspection of the structure, concrete strength test, rebar pull-out test and static load test, and complete the construction after the test is passed.

[0090] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A construction structure for a newly added reinforced concrete cantilever balcony, based on the existing reinforced concrete beams of an existing building, characterized in that: This includes temporary support components, beam widening and reinforcement sections, steel reinforcement connection frames, and cantilevered balcony slabs; The temporary support assembly is installed on the indoor side of the original reinforced concrete beam, including a vertical support steel pipe and adjustable top supports respectively installed at the upper and lower ends of the vertical support steel pipe. The upper adjustable top support is pressed against the bottom of the original floor slab, and the lower adjustable top support is supported on the indoor ground. The widened and reinforced section of the beam is cast on the indoor side of the original reinforced concrete beam; The steel reinforcement connection skeleton includes newly added longitudinal reinforcing bars, U-shaped connecting bars, and cantilever slab reinforcing bars; the two ends of the newly added longitudinal reinforcing bars are inserted into the original reinforced concrete columns; the U-shaped connecting bars are welded and fixed to the original beam transverse stirrups; the inner ends of the cantilever slab reinforcing bars are bent and anchored into the widened and reinforced section of the beam. The cantilevered balcony slab is cast on the outdoor side of the steel reinforcement frame and is integrally cast with the widened and reinforced beam section using the same grade of micro-expansion fine aggregate concrete.

2. The newly constructed reinforced concrete cantilever balcony structure according to claim 1, characterized in that, The temporary support components are arranged at equal intervals along the length of the original reinforced concrete beam, with a spacing of 800mm to 1200mm.

3. The construction structure for the newly added reinforced concrete cantilevered balcony according to claim 1, characterized in that, The newly added longitudinal reinforcing bars of the beam are hot-rolled ribbed steel bars with a diameter of 16mm to 22mm; the newly added longitudinal reinforcing bars of the beam are embedded to a depth of not less than 15d1 in the original reinforced concrete column, where d1 is the diameter of the newly added longitudinal reinforcing bars of the beam; the newly added longitudinal reinforcing bars of the beam are embedded using epoxy-based building anchoring adhesive, and the bonding strength of the anchoring adhesive is not less than 30MPa.

4. The construction structure for the newly added reinforced concrete cantilevered balcony according to claim 1, characterized in that, The U-shaped connecting bars are made of hot-rolled ribbed steel bars with a diameter of 12mm to 16mm; multiple U-shaped connecting bars are arranged at equal intervals along the length of the original reinforced concrete beam, with a spacing of 150mm to 200mm; the U-shaped connecting bars are connected to the original beam's transverse stirrups by double-sided fillet welds, and the weld leg size is not less than 0.5 times the diameter of the U-shaped connecting bar.

5. The newly added reinforced concrete cantilever balcony construction structure according to claim 1, characterized in that, The reinforcing bars of the cantilever slab are hot-rolled ribbed steel bars with a diameter of 12mm to 18mm; the reinforcing bars of the cantilever slab are arranged at equal intervals along the cantilever direction of the balcony, with a spacing of 150mm to 200mm; the length of the reinforcing bars of the cantilever slab anchored into the widened and reinforced section of the beam is not less than 15d2, where d2 is the diameter of the reinforcing bars of the cantilever slab.

6. The newly constructed reinforced concrete cantilever balcony structure according to claim 1, characterized in that, The steel reinforcement connection skeleton also includes cantilever slab distribution bars; the cantilever slab distribution bars are hot-rolled plain round steel bars with a diameter of 8mm to 10mm, and their inner ends are implanted into the original reinforced concrete beam by rebar installation.

7. The construction structure for the newly added reinforced concrete cantilevered balcony according to claim 1, characterized in that, The width of the widened and reinforced section of the beam is 150mm to 250mm, and the height is the same as that of the original reinforced concrete beam. The strength grade of the micro-expansion fine stone concrete is one grade higher than that of the original reinforced concrete beam, the expansion rate is 0.01% to 0.03%, and the coarse aggregate particle size is no greater than 10mm.

8. The newly constructed reinforced concrete cantilever balcony structure according to claim 1, characterized in that, The thickness of the cantilevered balcony slab is 100mm to 150mm, and the cantilever length is 1200mm to 2000mm; the slump of the micro-expansion fine aggregate concrete is controlled at 120mm to 140mm.

9. A method for constructing a newly added reinforced concrete cantilevered balcony, based on the newly added reinforced concrete cantilevered balcony construction structure as described in any one of claims 1 to 8, characterized in that, The method includes the following steps: S1. Construction preparation and original structure inspection: Determine the design parameters of the cantilever balcony, inspect the concrete strength, reinforcement configuration, carbonation degree and crack condition of the original reinforced concrete beam, assess the bearing capacity of the original structure and determine the size of the beam widening and reinforcement section; S2. Temporary support installation: Install temporary support components on the indoor side of the original reinforced concrete beam, tighten the upper adjustable top support to the bottom of the original floor slab, and support the lower adjustable top support to the indoor ground; S3. Pre-treatment of the original structure: Local chiseling is carried out at the beam-slab junction and bottom corner of the original reinforced concrete beam to expose the original beam's transverse stirrups. The chiseled surfaces are then roughened, cleaned, rinsed, and dried in sequence. S4. Rebar installation and welding: Drill holes at the corresponding positions of the existing reinforced concrete columns, insert the new longitudinal reinforcing bars into the beam and wait for the rebar adhesive to cure; weld the open end of the U-shaped connecting bar to the original beam's transverse stirrups to form a rigid connection node. S5. Reinforcement binding: Arrange the reinforcing bars of the cantilever slab and bind them to the newly added longitudinal reinforcing bars of the beam, so that the newly added longitudinal reinforcing bars of the beam, the U-shaped connecting bars and the reinforcing bars of the cantilever slab together form a reinforcement connection skeleton; S6. Formwork and integral casting: Set up the casting formwork and seal it to prevent grout leakage. Use micro-expansion fine stone concrete with a strength grade one higher than the original reinforced concrete beam. Cast the widened and reinforced section of the beam and the cantilevered balcony slab in one piece. After casting, water curing shall be carried out for no less than 14 days. S7. Support Removal and Inspection: After the concrete strength reaches the design strength, remove the temporary supports and formwork; conduct a visual inspection of the structure, concrete strength test, rebar pull-out test and static load test, and complete the construction after the test is passed.

10. The construction method for the newly added reinforced concrete cantilevered balcony according to claim 9, characterized in that, The integrated pouring adopts a layered pouring method, with a layer thickness of no more than 300mm, and is compacted by using a small vibrator; after the concrete curing is completed, the load-bearing capacity of the balcony is verified to meet the design requirements through a static load test.

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