Construction method for converting secondary beam into main beam in reinforcement project

Abstract

The invention discloses a construction method for transforming a secondary beam into a main beam in a reinforcing project, which comprises the following steps of: transforming an old building to enlarge a space, calculating according to a structural load, enlarging the section of an original secondary beam, transforming the original secondary beam into the main beam, namely a reinforcing beam, dismantling three middle columns positioned below the reinforcing beam, and enlarging the bearing surfaces of bearing columns positioned at two ends of the beam; the construction method comprises the following steps: (1) removing related loads; (2) reinforcing a support before beam construction; (3) cutting a middle column head; (4) original house structural plate parts on the two sides of the beams are dismantled, and original roof structural plates from the original secondary beams to the reinforcing beam area are dismantled; (5) mounting a beam bottom die, a beam side die and a beam upturning part template, and erecting a supporting system; (6) reinforcing beam steel bar connection; (7) concrete pouring and curing are conducted on the beam lower hanging part and the beam upper turning part; and (8) the formwork is removed, wherein the formwork is removed after the concrete strength reaches 100%. By means of the modularized steel supporting system, staged pouring and the precise column cutting technology, safe, rapid and economical structural transformation is achieved.

Description

Technical Field

[0001] This invention relates to the field of building structure renovation technology, specifically to a construction method for reinforcement projects in the renovation of old buildings, and particularly to a construction method for converting secondary beams into main beams in reinforcement projects. Background Technology

[0002] In the process of urbanization, many old buildings suffer from declining structural safety and outdated functionality. To meet new usage demands, it is often necessary to remove some load-bearing columns to expand space. Traditional reinforcement methods are time-consuming, costly, and have a significant impact on the original structure. Among existing technologies, the beam-supported column removal technique has some applications, but the load transfer control during construction is not precise, which can easily lead to structural safety hazards, and the construction period is long with significant material waste.

[0003] Especially in the renovation of old brick-concrete buildings, the limited size and strength of the original structural components place higher demands on the design of temporary support systems, joint construction, and the reliability of the bonding between new and old concrete during construction. Existing technologies often suffer from insufficient rigidity of the support system, unreliable connections with the original structure, and unclear sequences for demolition and pouring, which can easily lead to safety hazards such as cracking and deformation during the renovation. Therefore, there is an urgent need for a safe, efficient, and cost-controllable construction method for converting secondary beams into main beams to achieve load redistribution and structural system optimization. Summary of the Invention

[0004] The present invention aims to address the shortcomings of the prior art and provide a construction method for reinforcing secondary beams to convert them into main beams. Through a modular steel support system, staged casting, and precise column cutting technology, a safe, fast, and economical structural transformation can be achieved.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this invention is: a construction method for converting secondary beams into main beams in a reinforcement project. In the renovation of old buildings to expand space, based on structural load calculations, the cross-section of the original secondary beams is enlarged, converting them into main beams, also known as reinforcement beams. The three intermediate columns located under the reinforcement beams are removed, and the load-bearing columns at both ends of the beams are enlarged. The construction method is as follows: ① Removal of relevant loads: Since the reinforcement beam is a roof beam, all relevant roof structural layers need to be removed during construction to unload and clear the roof; ② Supports before reinforcement beam construction: The original secondary beams located in front of, behind, left of, and right of each intermediate column are supported by... Supporting steel columns are installed under the main beams, or cantilever beams are installed at the front end of the original main beams, with diagonal supporting steel columns installed under the cantilever beams; ③ Cut the column heads of the intermediate columns, cutting them to the height of the designed position; ④ Remove the original roof structural slabs on both sides of the beams, and remove the original roof structural slabs in the area from the original secondary beams to the reinforced beams; ⑤ Install the bottom formwork, side formwork, and formwork for the beams, and erect the support system; ⑥ Connect the reinforcing bars of the reinforced beams; ⑦ Pour and cure the concrete for the lower and upper parts of the beams; ⑧ Remove the formwork after the concrete strength reaches 100%.

[0006] Preferably, the original secondary beam has a cross-section of 300*600mm, and the reinforcing beam has a cross-section of 800*200mm.

[0007] Preferably, the original load-bearing columns at both ends of the beam have a cross-section of 500*400mm, and the cross-section of the load-bearing columns after enlargement is 1000*900mm.

[0008] Preferably, a first supporting steel column made of 300*300 H-beams is installed under the original main beam, a second supporting steel column made of 200*200 H-beams is installed under the original secondary beam, and a diagonal supporting steel column made of 20# I-beams is installed under the cantilever beam. U-shaped brackets at the top of the first and second supporting steel columns respectively cooperate with the corresponding original main beam and original secondary beam and are fixed with expansion bolts. Jacks are installed between the circumferential column brackets at the lower ends of the first and second supporting steel columns and the pad steel plates fixed to the original building base. After the jacking is completed, steel plate wedges are inserted between the lower end seat plate of the steel column and the pad steel plate. The U-shaped brackets at the top of the diagonal supporting steel columns cooperate with the corresponding cantilever beams and are fixed with expansion bolts. The connecting plate fixed to the lower end of the diagonal supporting steel columns is fixed to the original intermediate column by expansion bolts.

[0009] Preferably, the step of cutting the intermediate column head is to mark the original intermediate column from the bottom of the original secondary beam -30mm to the bottom of the reinforcement beam -105mm, cut at the marked position, and after cutting, the part of the original intermediate column head connected to the original secondary beam is wrapped in the reinforcement beam.

[0010] Preferably, for the erection of the beam bottom formwork, grout is placed on the original structural base plate corresponding to the reinforced beam. Before the grout has fully set, 16# I-beams are laid at 450mm intervals perpendicular to the span of the reinforced beam. Φ32mm steel bars are evenly welded onto the 16# I-beams. The lower end of the uprights is fitted with sleeves over the uprights. Adjustable supports are installed at the top of the uprights, and ground bracing is installed at the bottom of the uprights. The uprights are spaced 450mm apart along the beam span. Wooden pads are placed at the bottom of the upright supports on both sides of the beam bottom. Bases are installed at the bottom of the uprights, and adjustable supports are installed at the top. For the installation of the beam side formwork, 15mm thick covered plywood formwork is used. The beam side formwork is reinforced with tie rods and double steel pipes, and the inner ribs of the beam side formwork are hung below. The formwork consists of 6 pairs of 40*70mm timber, with outer ribs made of Φ48.3*3.6mm double steel pipes spaced 450mm apart. A Φ14 tie rod is added between the outer ribs on both sides of the bottom beam formwork for reinforcement. At the beam-slab junction, Φ48*2.8mm steel pipes are used to brace the beam side formwork at a 45° angle. The formwork for the upturned part of the beam is erected after the concrete strength of the lower beam reaches 100%. The formwork uses 15mm thick covered plywood formwork. The beam side formwork is reinforced with tie rods and double steel pipes. The inner ribs of the upturned beam side formwork consist of 6 pairs of 40*70mm timber, with outer ribs made of Φ48.3*3.6mm double steel pipes spaced 450mm apart. Two Φ14mm tie rods are installed between the outer ribs on both sides.

[0011] Preferably, the reinforcement bars of the strengthening beam are connected by mechanical connection, and the joints are of the first-class type. The key bars are Φ12@200 and are evenly distributed along the length of the original secondary beam. The key bars are connected to the original secondary beam by anchoring, with an implantation depth of 100mm and an exposed length of 150mm. When the reinforcement bars encounter 200*200 H-beams, holes are made in the web of the H-beams according to the size, position and elevation of the reinforcement bars. At the edge column, one row of bottom reinforcement bars is anchored into the original structural column by 10d, and the two rows of reinforcement bars do not extend into the original structural column.

[0012] Preferably, the concrete grade of the under-beam and the up-beam is increased by one grade. When pouring concrete, the under-beam or the up-beam is poured in layers from the middle of the span to both sides. The pouring height of each layer does not exceed 450mm. The upper layer of concrete is poured before the initial setting of the lower layer of concrete. The concrete is kept moist for no less than 28 days. Beneficial effects

[0013] The modular steel support system enables rapid unloading and precise column cutting, reducing the construction period to 15-45 days, which is significantly shorter than the traditional process (3-6 months). The steel supports have a 90% reuse rate, reducing material waste. During construction, only local nodes are reinforced, and the original building facade is completely preserved, making it suitable for the protection of historical buildings; By employing phased pouring and load control, structural safety is ensured and the risk of accidents is reduced.

[0014] The present invention also has the following beneficial effects: By using modularly designed H-beam supports (such as 200×200mm and 300×300mm) and their dedicated U-shaped brackets, top support platforms, and wedge plug systems, a close fit with the original beams and slabs and reliable force transmission are achieved. The support stiffness and stability are far higher than those of traditional steel pipe scaffolding, ensuring safety during the column cutting process.

[0015] By employing a phased pouring process of "first pouring the lower section, and then pouring the upper section after the strength reaches 100%", the already solidified lower beam and the original roof structure slab are cleverly used to jointly bear the construction load of the upper section, optimizing the load transfer path, reducing the load on the formwork support system, and improving construction safety.

[0016] By setting keyed reinforcing bars (Φ12@200) on the original secondary beam and adopting the rebar installation process, as well as the precise drilling and penetration of reinforcing bars through the web of the H-shaped steel, the effective connection and coordinated stress between the new and old concrete components were ensured, and the load was transferred smoothly and reliably from the original secondary beam to the reinforced main beam. Attached Figure Description

[0017] Figure 1 This is a schematic diagram showing the location of the beam reinforcement support system of the present invention; Figure 2 This is a partially enlarged structural schematic diagram of the beam reinforcement and support system of the present invention; Figure 3 This is a schematic diagram of the original main beam support and backfill structure of the present invention; Figure 4 This is a schematic diagram of the primary and secondary beam support and backfill structure of the present invention; Figure 5 An enlarged structural diagram showing the steel plate wedge inserted into the lower end of the supporting steel column; Figure 6 This is a schematic diagram of the installation and support system structure of the reinforced beam formwork of the present invention; Figure 7 This is a schematic diagram of the steel reinforcement connection structure between the original secondary beam and the reinforced beam. Detailed Implementation

[0018] A construction method for reinforcing secondary beams to transfer main beams in engineering projects, using... Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 As shown in the example, this embodiment takes a four-story brick-concrete structure building as an example. The original conference room needs to be expanded. The 300×600mm secondary beam is converted into an 800×2000mm reinforcing beam, and three intermediate columns are removed.

[0019] Step 1: Dismantle, unload, and position the lines. Remove all structural layers of the roof to unload and remove the roof structure. Then, position and lay out the lines, draw a positioning diagram according to the construction plan, and accurately determine the positions of the unloading support steel, the support system uprights 17, and the horizontal I-beams 16 under the beams in the span direction.

[0020] Step 2: Support before construction of reinforcement beam 2 This step uses a modular steel support system for precise unloading.

[0021] (1) Support for the original secondary beam 1: A second supporting steel column 9 is set on each side at a distance of 875mm from a specific axis (such as axis 22, axis 23, axis 24). The steel column is made of 200×200×8×12mm H-beam. A U-shaped bracket 10 with a thickness of 15mm is welded to the top of the column at the contact surface with the beam. The steel plate is 360mm wide, 260mm long, and 200mm high on the side. A rectangular steel plate with a thickness of 20mm and a size of 200×200mm is welded to the bottom of the H-beam at the contact surface with the plate. On the web of the H-beam, a top support platform is fully welded at a position 280mm from the bottom. The platform is made of a rectangular steel plate with a thickness of 15mm and a size of 200*350mm and two right-angled trapezoidal steel plates with a thickness of 15mm.

[0022] During the jacking construction, grout is first applied to the H-beam position on the original structural base plate. After the grout has reached sufficient strength, a 900*500mm, 15mm thick steel plate 12 is laid. The assembled second support steel column 9 system is then positioned, structural adhesive is applied between the bottom of the beam and the U-shaped bracket 10, and it is fixed with expansion bolts. Subsequently, two 20t jacks 13 are used to symmetrically jack the H-beam. After the jacking is completed, steel wedges 14 are inserted between the steel plate 12 and the bottom steel plate of the steel column and fully welded for fixation.

[0023] (2) Original main beam 4 support: The first support steel column 8 is made of 300×300×10×15mm H-beams. Its manufacturing and top support process is similar to that of the second support steel column 9. The U-shaped support 10 is 600mm long, with a bottom steel plate thickness of 30mm and a size of 300×300mm. The top support platform is welded to the flange plate.

[0024] (3) Support for cantilever beam 5: The inclined support steel column 6 is made of 20# I-beams. Its top end is fixed to the cantilever beam 5 through U-shaped bracket 10, and the connecting plate 15 fixed at the bottom end is fixed to the original intermediate column 3 through expansion bolts. The embedded plate (-16*350*600) is fixed to the original structure with chemical anchors (M20 G5.8 grade). The bonding surface is pressure-injected with structural adhesive to increase friction. All welding must be full welding.

[0025] (4) Backfilling measures: If the upper supporting steel column is located in an unfavorable structure (such as a window opening) or a position with insufficient bearing capacity in the lower layer, H-beams of the same specification should be backfilled at the corresponding position in the lower layer to form a continuous and reliable load transfer path.

[0026] Step 3: Cut the intermediate support column head Mark the original intermediate column 3, from 30mm below the bottom of the original secondary beam 1 to 105mm below the bottom of the reinforcement beam 2, and cut at the marked positions using static cutting equipment. The cutting sequence should proceed from the intermediate column to the two side columns. After cutting, the column head portion of the original intermediate column 3 (approximately 880*400*500mm) is encased in the subsequently poured concrete of the reinforcement beam 2.

[0027] Step 4: Remove the original roof structural slabs on both sides of the beam. The original roof structure slabs in the area from the first side of the original secondary beam to the second side of the reinforcement beam were removed, and the contact surfaces of the original concrete structure were roughened to ensure a good bond between the old and new concrete.

[0028] Step 5: Installation of bottom formwork and side formwork for beams, and erection of the support system. (1) Support system erection: Grouting is applied to the original structural base plate corresponding to the reinforced beam 2. Before the grouting material sets, 16# I-beams 16 are laid perpendicular to the span direction of the reinforced beam 2 at 450mm intervals. Φ32mm steel bars are welded evenly on the I-beams, and the sleeves at the lower ends of the uprights 17 are fitted over the steel bars. The uprights 17 are spaced 450mm apart along the beam span direction, with wooden pads, bases 19, and longitudinal and transverse ground bracing at the bottom, and adjustable supports 20 at the top. The upright joints adopt a butt joint method with a special outer sleeve, with the outer sleeve opening facing downwards. The support frame is rigidly connected to the intermediate support column to form a "frame column", and scissor bracing is installed as required. The bottom formwork of the beam is arched by two-thousandths of the span (21600mm) (43.2mm).

[0029] (2) Template installation: The bottom formwork and side formwork 21 of the beam are made of 15mm thick covered plywood formwork. The secondary ribs of the bottom formwork are 5 x 40*40*2.5mm square steel bars, and the main ribs are φ48×2.8mm steel pipes with a spacing of 450mm. The inner ribs of the side formwork 21 are 6 pairs of 40×70mm timber, and the outer ribs are φ48.3×3.6mm double steel pipes with a spacing of 450mm. A Φ14 tie bolt 22 is added between the outer ribs on both sides of the bottom formwork for reinforcement, and φ48×2.8mm steel pipes 23 are used as 45° diagonal bracing at the junction of the beam and slab.

[0030] Step 6: Reinforcement connection of beam 2 The reinforcement bars of the reinforced beam 2 are connected mechanically, using Class I joints. Dowel-key reinforcement bars 24 (Φ12@200) are evenly distributed along the length of the original secondary beam 1, connected to the original secondary beam 1 using a rebar anchoring method, with an anchoring depth of 100mm and an exposed length of 150mm. When the reinforcement bars conflict with the 200×200 H-beams, holes are precisely drilled in the web of the H-beams according to the size, position, and elevation of the reinforcement bars. At the edge columns, one row of bottom reinforcement bars (15C18) is anchored 10d into the original structural column, while the second row of bottom reinforcement bars (11C18) does not extend into the original structural column.

[0031] Step 7: Concrete pouring and curing of the lower and upper sections of the beam. (1) Concrete pouring for the under-beam section: The concrete grade is increased by one level. During pouring, the concrete is poured in layers from the middle of the span to both sides, with each layer not exceeding 450mm in height. The upper layer of concrete is poured before the lower layer of concrete has initially set.

[0032] (2) Formwork erection and concrete pouring for the upturned section of the beam: After the concrete strength of the lower beam reaches 100%, the formwork for the upturned section of the beam is erected and the concrete is poured. This is to utilize the lower beam, which has reached its strength, and the original roof structure slab to jointly bear the load of the upturned section of concrete. The pouring method is the same as that for the lower beam.

[0033] (3) Concrete curing: A designated person shall be responsible for the moisturizing curing of reinforced beam 2, and the moisturizing curing period shall not be less than 28 days.

[0034] Step 8: Formwork Removal After the concrete reaches 100% strength, the side formwork is removed first, followed by the bottom formwork and support frame. After demolding, the H-beams supporting the original secondary beam 1 are statically cut and removed, and the reinforced beam 2 is then finished with grinding, plastering, and other finishing treatments.

[0035] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A construction method for reinforcing secondary beams to convert main beams in engineering projects, characterized by: To expand the space of the old building renovation, according to the structural load calculation, the cross section of the original secondary beam (1) is enlarged and the original secondary beam (1) is converted into the main beam, also known as the reinforcement beam (2). The three intermediate columns (3) located under the reinforcement beam are removed, and the load-bearing columns at both ends of the beam are enlarged. The construction method is as follows: ① Remove the relevant loads. The reinforcement beam (2) is a roof beam. During construction, the relevant roof structural layers need to be removed so that the roof can be unloaded and cleaned up; ② Support before the reinforcement beam (2) is constructed. Support steel columns are set under the original main beam (4) located in front, behind, left and right of each intermediate column (3), or on the original main beam. (4) A cantilever beam (5) is set at the front end, and a diagonal support steel column (6) is set under the cantilever beam (5); ③ Cut the column head of the intermediate column (3) according to the height of the designed position of the column head of the intermediate column (3); ④ Remove the original roof structure board on both sides of the beam, and remove the original roof structure board in the area from the original secondary beam (1) to the reinforcement beam (2); ⑤ Install the bottom formwork, side formwork and the formwork of the beam and the support system; ⑥ Connect the reinforcement bars of the reinforcement beam; ⑦ Pour and cure the concrete of the lower part of the beam and the upper part of the beam; ⑧ Remove the formwork after the concrete strength reaches 100%.

2. The construction method for reinforcing a secondary beam to a main beam in an engineering project according to claim 1, characterized in that: The original secondary beam (1) has a cross-section of 300*600mm, and the reinforced beam (2) has a cross-section of 800*200mm.

3. The construction method for reinforcing a secondary beam to a main beam according to claim 1, characterized in that: The original cross-section of the load-bearing columns at both ends of the beam was 500*400mm, and the cross-section of the load-bearing column (7) after the increase was 1000*900mm.

4. The construction method for reinforcing a secondary beam to a main beam according to claim 1, characterized in that: the original... The main beam (4) is supported by a first supporting steel column (8) made of 300*300 H-beams. The secondary beam (1) is supported by a second supporting steel column (9) made of 200*200 H-beams. The cantilever beam (5) is supported by a diagonal supporting steel column (6) made of 20# I-beams. The U-shaped brackets (10) at the top of the first supporting steel column (8) and the second supporting steel column (9) are respectively matched with the corresponding primary beam (4) and secondary beam (1) and fixed with expansion bolts. (8) A jack (13) is installed between the circumferential column support (11) at the lower end of the second supporting steel column (9) and the pad steel plate (12) fixed on the original building base plate. After the jacking is completed, a steel plate wedge (14) is inserted between the lower end seat plate of the steel column and the pad steel plate (12). The U-shaped support (10) at the top of the inclined supporting steel column (6) is matched with the corresponding cantilever beam (5) and fixed with expansion bolts. The connecting plate (15) fixed at the lower end of the inclined supporting steel column (6) is fixed to the original intermediate column (3) by expansion bolts.

5. The construction method for reinforcing a secondary beam to a main beam according to claim 1, characterized in that: The steps for cutting the intermediate column head are as follows: mark the original intermediate column (3) from the bottom of the original secondary beam (1) -30mm to the bottom of the reinforcement beam (2) -105mm, cut at the marked position, and after cutting, the part of the original intermediate column head connected to the original secondary beam (1) is wrapped in the reinforcement beam (2).

6. The construction method for reinforcing a secondary beam to a main beam according to claim 1, characterized in that: The bottom formwork of the beam is erected, and grout is placed on the original structural base plate corresponding to the reinforced beam (2). Before the grouting material is fully set, 16# I-beams (16) are laid at 450mm intervals in the direction perpendicular to the span of the reinforced beam (2). Φ32mm steel bars are welded evenly on the 16# I-beams (16). The sleeve of the upright (17) is sleeved on the outside of the upright (17). An adjustable support (20) is set at the top of the upright (17), and a sweeping bar is set at the bottom of the upright (17). The uprights (17) are spaced 450mm apart along the span of the beam. Wooden pads are set at the bottom of the upright supports on both sides of the beam bottom. A base (19) is set at the bottom of the column (18), and an adjustable support (20) is set at the top. The side formwork of the beam is installed. The side formwork of the beam is made of 15mm thick covered plywood formwork. Tie rods (22) are set on the side formwork of the beam. The lower beam side formwork is reinforced with double steel pipes. The inner ribs of the lower beam side formwork are 6 pairs of 40*70mm timber, and the outer ribs are Φ48.3*3.6mm double steel pipes with a spacing of 450mm. A Φ14 tie rod (22) is added between the outer ribs on both sides of the bottom beam formwork (21) for reinforcement. At the beam-slab junction, Φ48*2.8mm steel pipe (23) is used to support the beam side formwork (21) at a 45° angle. The formwork for the upper part of the beam is erected. After the concrete strength of the lower beam reaches 100%, the formwork is erected. The formwork is made of 15mm thick covered plywood formwork. The beam side formwork is reinforced with tie rods (22) and double steel pipes. The inner ribs of the upper beam side formwork are 6 pairs of 40*70 timber, and the outer ribs are Φ48.3*3.6mm double steel pipes with a spacing of 450mm. Two Φ14mm tie rods (22) are set between the outer ribs on both sides.

7. The construction method for reinforcing a secondary beam to a main beam in an engineering project according to claim 1, characterized in that: The reinforcement of the beam (2) is connected by mechanical connection. The joint is a first-class joint. The key reinforcement Φ12@200 is evenly distributed along the length of the original secondary beam (1). The key reinforcement (24) is connected to the original secondary beam (1) by anchoring. The implantation depth is 100mm and the exposed length is 150mm. When the reinforcement encounters a 200*200 H-beam, holes are made in the web of the H-beam according to the size, position and elevation of the reinforcement. At the edge column, one row of bottom reinforcement is anchored into the original structural column for 10d. The two rows of reinforcement do not extend into the original structural column.

8. The construction method for reinforcing a secondary beam to a main beam according to claim 1, characterized in that: For the concrete pouring of the lower and upper sections of the beam, the concrete grade should be increased by one level. When pouring the concrete, the lower or upper beam should be poured in layers from the middle of the span to both sides. The pouring height of each layer should not exceed 450mm. The upper layer of concrete should be poured before the lower layer of concrete has initially set. The concrete should be kept moist for no less than 28 days.

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