A new and old concrete interface beam and plate component handover structure and construction method thereof

Abstract

The present invention discloses a new and old concrete interface beam, plate component intersection structure and construction method thereof, comprising an existing beam-type component, a force transmission beam and a newly built plate-type component, wherein the force transmission beam is connected to the end of the newly built plate-type component and casted integrally therewith, the outer side surface of the force transmission beam is fixed to the new and old concrete bonding surface of the existing beam-type component, the new and old concrete bonding surface is roughened, and an interface steel bar is provided between the force transmission beam and the existing beam-type component, one end of the interface steel bar is anchored into the force transmission beam, and the other end is implanted into the existing beam-type component through the new and old concrete bonding surface. The present invention arranges a force transmission beam between the existing beam-type component and the newly built plate-type component, increases the bonding area of ​​the new and old concrete interface, significantly improves the mechanical bite force, van der Waals force and other interface forces of the new and old concrete interface, improves the force transmission effect of the new and old concrete interface, ensures the construction quality, and facilitates the construction. An interface steel bar is provided between the force transmission beam and the existing beam-type component, which improves the interface shear bearing capacity.

Description

Technical Field

[0001] The invention relates to a new-old concrete interface beam and plate component handover structure and a construction method thereof. Background Art

[0002] Concrete structure is the most common structural form in my country's industrial and civil buildings. Concrete reinforcement has been gradually carried out since the 1950s. Appropriate reinforcement technology and practices ensure the safety of existing building structures and extend their service life. Among the concrete reinforcement practices, the handover treatment between new and old concrete is one of the most common reinforcement practices. It is common to add new beams and new slabs to existing concrete columns; add new beams and new slabs to existing concrete walls; add new beams and new slabs to existing concrete beams, etc.

[0003] like Figure 1 , 2 As shown in the figure, the conventional treatment of the bonding surface between the new and old concrete is roughening treatment, that is, roughening 4 is performed on the bonding surface 2 between the new and old concrete of the existing beam-type component 1, the newly-built plate-type component 3 is connected with the existing beam-type component 1 on the bonding surface 2 between the new and old concrete, and the transverse reinforcement of the newly-built plate-type component 3 is implanted into the existing beam-type component 1 through the reinforcement hole 5. Although the roughening and reinforcement implantation increase the bite degree of the new and old concrete to a certain extent, with the continuous accumulation of engineering experience, this method of single roughening treatment of the interface between the new and old concrete has the following defects:

[0004] ⑴ At present, there are no clear regulations on the roughening depth and roughening rate of most new and old concrete bonding surfaces in engineering, resulting in uneven roughening quality during actual construction, which brings unsafe factors to the reinforcement quality.

[0005] (2) From the research on the bonding mechanism of new and old concrete in recent years, it is known that the bonding strength of the new and old concrete interface is much lower than the body strength of the new and old concrete respectively, which is about 0.4 times of the complete cast-in-place component. Therefore, when the interface between the new and old concrete is subjected to excessive load, direct shear failure is prone to occur. Summary of the invention

[0006] The first purpose of the present invention is to provide a new and old concrete interface beam and plate component handover structure which has a simple structure, is convenient to construct, has a low cost, can improve the force transmission effect of the new and old concrete interface, and ensure the construction quality.

[0007] The first object of the present invention is achieved through the following technical scheme: a new and old concrete interface beam and plate component intersection structure, characterized in that: it includes an existing beam-type component, a force transmission beam and a newly built plate-type component, the force transmission beam is connected to the end of the newly built plate-type component and is cast integrally with it, the outer side surface of the force transmission beam is fixed to the new and old concrete bonding surface of the existing beam-type component, the new and old concrete bonding surface is roughened, and an interface steel bar is provided between the force transmission beam and the existing beam-type component, one end of the interface steel bar is anchored in the force transmission beam, and the other end passes through the new and old concrete bonding surface and is implanted into the existing beam-type component.

[0008] The present invention sets a force-transfer beam between the existing beam-type component and the newly-built plate-type component, thereby increasing the bonding area of ​​the interface between the new and old concrete, significantly improving the mechanical bite force, van der Waals force and other interface forces at the interface between the new and old concrete, improving the force transmission effect at the interface between the new and old concrete, ensuring the construction quality, and convenient construction, simple structure, low cost, and easy implementation. Interface steel bars are provided between the force-transfer beam and the existing beam-type component, and the number of interface steel bars at the interface between the new and old concrete can be increased according to calculation requirements, greatly improving the shear bearing capacity of the interface. In addition, since the present invention adopts a force-transfer beam, the interface steel bars and the beam surface steel bars are easy to stagger, effectively ensuring the quality of the embedded steel bars, and making the construction quality controllable. The boundary of the newly-built plate-type component of the present invention can be selected as fixed connection or hinged connection according to design requirements, thereby increasing the flexibility of the design.

[0009] As a preferred embodiment of the present invention, the width of the force transmission beam is greater than or equal to 200 mm, and the width of the force transmission beam is determined according to the force requirements of the newly built plate-type component, and should meet the reinforcement anchoring requirements of the newly built plate-type component. The height of the force transmission beam is determined according to the interface force requirements, and the height of the force transmission beam is greater than twice the thickness of the newly built plate-type component, and greater than or equal to 300 mm.

[0010] The cross-sectional shear bearing capacity of the force transmission beam of the present invention is calculated according to the following formula:

[0011] V=cA c +μ(A v f y +P c )……………………………………(1)

[0012] V ≥ K1f c A c , V=K1f c A c ………………………………(2)

[0013] V≥K2A c , V = K2A c ……………………………………(3)

[0014] in:

[0015] A c —The bonding surface area of ​​new and old concrete;

[0016] c—Roughness coefficient, the overall specimen is 2.80Mpa, the horizontal plate roughening specimen is 1.96Mpa, and the other roughening specimens are 1.96Mpa.

[0017] The rough specimen is 1.68Mpa, and the unroughened specimen is 0.525Mpa;

[0018] A v — Area of ​​embedded reinforcement;

[0019] μ—friction coefficient, the overall specimen is 1.4, the horizontal plate roughened specimen is 1.0, and the other roughened specimens are 1.0.

[0020] For the specimen without chiseling, the value is 0.6;

[0021] f y — steel bar yield (or design) strength;

[0022] P c — horizontal stress;

[0023] f c —Average compressive strength of new and old concrete;

[0024] K1—concrete section shear bearing capacity coefficient, the integral specimen is taken as 0.25, the horizontal plate roughening specimen is taken as 0.3,

[0025] The value for other roughened specimens is 0.25, and the value for non-roughened specimens is 0.2;

[0026] K2—concrete ultimate shear strength coefficient, the integral specimen is 10.5, the horizontal plate roughening specimen is 12.6,

[0027] The value for other roughened specimens is 10.5, and the value for non-roughened specimens is 5.6.

[0028] As a recommended implementation mode of the present invention, the reinforcement ratio of the force transmission beam is greater than or equal to 0.15%, and the stirrups are greater than or equal to C6@200mm (symbol C refers to grade 3 steel, the same below).

[0029] In order to ensure that the force transfer beam effectively transmits the interface force, the connection between the steel bars of the newly built plate-type components and the force transfer beam must meet the design anchorage requirements; interface steel bars must be provided at the interface between the force transfer beam and the existing concrete component, and the steel bar area must meet the interface force (bending and shear) requirements and be greater than or equal to C10@200mmx200mm; the interface steel bars anchored in the force transfer beam must meet the tensile anchorage requirements, and the interface steel bars implanted in the existing concrete component must meet the steel bar pull-out resistance requirements.

[0030] In order to improve the mechanical bite force of the bonding surface of new and old concrete, the bonding surface of new and old concrete is roughened with a depth of 6 to 10 mm and a roughening rate greater than 90%. The roughening rate = the area of ​​the roughened portion of the bonding surface / the total area of ​​the bonding surface × 100%.

[0031] The second object of the present invention is to provide a construction method for the above-mentioned new and old concrete interface beam and plate component intersection structure.

[0032] The second object of the present invention is achieved by the following technical solution: A construction method for the above-mentioned new and old concrete interface beam and plate component intersection structure, characterized by comprising the following steps:

[0033] ⑴ Carry out roughening treatment on the bonding surface of new and old concrete of existing beam-type components;

[0034] (2) Tie the reinforcement of the newly built plate-type components and force-transfer beams, where the reinforcement of the end of the newly built plate-type components is tied together with the reinforcement of the force-transfer beams, and the interface reinforcement is tied so that one end of the interface reinforcement is anchored in the force-transfer beam and the other end is embedded in the existing beam-type components;

[0035] ⑶Build pouring formwork;

[0036] (4) Pour concrete into the casting formwork and cast the new plate-type components and load-transfer beams in one piece;

[0037] ⑸ After the concrete reaches a certain strength, remove the casting formwork and it is done.

[0038] As a preferred embodiment of the present invention, the concrete grade of the newly constructed plate-type components and force-transfer beams is at least one grade higher than the concrete grade of the existing beam-type components.

[0039] In order to strengthen the bonding surface and provide as much van der Waals force as possible, the present invention comprises the following steps (1) after roughening, removing loose fragments and scum on the bonding surface of the new and old concrete, and then rinsing and moistening the bonding surface of the new and old concrete without leaving any visible water; and (4) adding a micro-expansion agent to the poured concrete to compensate for the shrinkage of the concrete of the new component, so that the interface is dense and seamless.

[0040] Compared with the prior art, the present invention has the following significant effects:

[0041] (1) The present invention arranges a force transmission beam between the existing beam-type component and the newly built plate-type component, thereby increasing the bonding area of ​​the new and old concrete interface, significantly improving the mechanical bite force, van der Waals force and other interface forces of the new and old concrete interface, improving the force transmission effect of the new and old concrete interface, ensuring the construction quality, and facilitating the construction.

[0042] (2) The present invention provides interface reinforcement between the force-transmitting beam and the existing beam-type component, and can increase the number of interface reinforcements at the interface between new and old concrete according to calculation requirements, thereby greatly improving the shear bearing capacity of the interface.

[0043] ⑶ Since the present invention adopts a force-transmitting beam, the interface steel bars and the beam surface steel bars are easy to stagger, which effectively ensures the quality of the embedded steel bars and makes the construction quality controllable.

[0044] (4) The boundaries of the newly-built plate-type components of the present invention can be fixed or hinged according to design requirements, thereby increasing the flexibility of the design.

[0045] (5) The present invention has a simple structure, low construction cost, and convenient construction, and is suitable for wide promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] Figure 1 It is a schematic diagram of the junction structure between the existing beam-type components and the newly built plate-type components;

[0048] Figure 2 It is a schematic diagram of the explosion structure where the existing beam-type components and the newly built plate-type components meet;

[0049] Figure 3 It is a schematic diagram of the structure of the present invention;

[0050] Figure 4 It is a schematic diagram of the explosion structure of the present invention;

[0051] Figure 5 is along Figure 3 Section view along line AA. DETAILED DESCRIPTION

[0052] Example 1

[0053] like Figures 3 to 5 As shown, it is a new and old concrete interface beam and plate component intersection structure of the present invention, which includes an existing beam-type component 6, a force-transmitting beam 7 and a newly built plate-type component 8. The steel bars of the force-transmitting beam 7 and the steel bars of the newly built plate-type component 8 are tied together and cast as a whole to form the force-transmitting beam 7 and the newly built plate-type component 8. The outer side of the force-transmitting beam 7 is fixed on the new and old concrete bonding surface 9 of the existing beam-type component 6. The new and old concrete bonding surface 9 is roughened to a depth of 6 to 10 mm, and the roughening rate is greater than 90%. An interface steel bar 10 is provided between the force-transmitting beam 7 and the existing beam-type component 6. One end of the interface steel bar 10 is anchored into the force-transmitting beam 7, and the other end passes through the anchor hole 11 on the new and old concrete bonding surface 9 and is anchored into the existing beam-type component 6.

[0054] The width of the force transmission beam is determined according to the force requirements of the newly built plate-type components and should meet the reinforcement anchorage requirements of the newly built plate-type components. The width of the force transmission beam 7 is greater than or equal to 200mm, and the height of the force transmission beam is determined according to the interface force requirements. The height of the force transmission beam is greater than 2 times the thickness of the newly built plate-type components and greater than or equal to 300mm.

[0055] The cross-sectional shear bearing capacity of the force transmission beam is calculated according to the following formula:

[0056] V=cA c +μ(A v f y +P c )……………………………………(1)

[0057] V ≥ K1f c A c , V=K1f c A c ………………………………(2)

[0058] V≥K2A c , V = K2A c ……………………………………(3)

[0059] in:

[0060] A c —The bonding surface area of ​​new and old concrete;

[0061] c—Roughness coefficient, the overall specimen is 2.80Mpa, the horizontal plate roughened specimen is 1.96Mpa, other roughened specimens are 1.68Mpa, and the non-roughened specimen is 0.525Mpa;

[0062] A v — Area of ​​embedded reinforcement;

[0063] μ—friction coefficient, 1.4 for the whole specimen, 1.0 for the horizontal plate roughened specimen, 1.0 for other roughened specimens, and 0.6 for the non-roughened specimen;

[0064] f y — steel bar yield (or design) strength;

[0065] P c — horizontal stress;

[0066] f c —Average compressive strength of new and old concrete;

[0067] K1—concrete section shear bearing capacity coefficient, 0.25 for the integral specimen, 0.3 for the horizontal plate roughened specimen, 0.25 for other roughened specimens, and 0.2 for the non-roughened specimen;

[0068] K2—Ultimate shear strength coefficient of concrete, 10.5 for integral specimens, 12.6 for roughened horizontal plate specimens, 10.5 for other roughened specimens, and 5.6 for non-roughened specimens.

[0069] The reinforcement ratio of the force transfer beam is greater than or equal to 0.15%, and the stirrups are greater than or equal to 6@200.

[0070] In order to ensure that the force transfer beam effectively transmits the interface force, the connection between the steel bars of the newly built plate-type components and the force transfer beam must meet the design anchorage requirements; interface steel bars must be provided at the interface between the force transfer beam and the existing concrete component, and the steel bar area must meet the interface force (bending and shear) requirements and be greater than or equal to C10@200mmx200mm; the interface steel bars anchored in the force transfer beam must meet the tensile anchorage requirements, and the interface steel bars implanted in the existing concrete component must meet the steel bar pull-out resistance requirements.

[0071] In this embodiment, the newly built plate-type component 8 is a newly built floor slab, and the boundary of the newly built floor slab is calculated as hinged. The existing concrete component 6 is an existing reinforced concrete beam with a cross-sectional size of 300×600, a protective layer thickness of 20mm, a concrete grade of C20, and fc=9.6N / mm 2 ; New floor thickness 100mm, concrete grade C25, fcv = 2ft = 2.54N / mm 2 .

[0072] According to the structural requirements, the size of the force transmission beam 7 is selected to be 200mm×300mm.

[0073] A 1-meter slab is selected as the calculation unit, and only the interface is roughened and chiseled. The direct shear bearing capacity is 0.4×2.8×80×1000=89.6kN; after setting the force transfer beam, the direct shear bearing capacity is 1.68×280×1000=470.4kN; for the intact cast-in-place integral component, the direct shear bearing capacity is 2.8×80×1000=224.0kN.

[0074] It can be seen that after setting the load transfer beam, the direct shear bearing capacity meets the bearing capacity requirements of intact cast-in-place components. The interface reinforcement is set according to the structure. The interface reinforcement is C10@200mmx200mm, and the anchorage depth and implantation depth meet the structural requirements.

[0075] The example shows that the bearing capacity of the interface after roughening is about 40% of that of the cast-in-place integral component. After the force transmission beam and the structural interface reinforcement are set on the interface, the bearing capacity is greater than the direct shear bearing capacity requirement of the cast-in-place integral component. It can be seen that after the force transmission beam is set, the force transmission of the interface meets the design requirements well.

[0076] A construction method for the above-mentioned new and old concrete interface beam and plate component handover structure comprises the following steps:

[0077] (1) Perform roughening treatment on the bonding surface 9 of the new and old concrete of the existing beam-type component 6, remove the loose fragments and scum on the bonding surface 9 of the new and old concrete, and then rinse and wet the bonding surface 9 of the new and old concrete without leaving any visible water;

[0078] (2) Tie the steel bars of the newly built plate-type component 8 and the force-transfer beam 7, wherein the steel bars of the newly built plate-type component 8 include surface bars 12 and bottom bars 13, and the steel bars of the force-transfer beam 7 include stirrups 14 and longitudinal bars 15. Tie the steel bars at the end of the newly built plate-type component 8 and the steel bars of the force-transfer beam 7 together, and tie the interface steel bars 10, so that one end of the interface steel bars 10 is anchored into the force-transfer beam 7, and the other end is implanted into the existing beam-type component 6;

[0079] ⑶Build pouring formwork;

[0080] (4) Pour concrete into the casting formwork, add micro-expansion agent into the poured concrete, and the concrete grade of the newly built plate-type component 8 and force-transmitting beam 7 is at least one grade higher than the concrete grade of the existing beam-type component 6. Cast the newly built plate-type component 8 and force-transmitting beam 7 in one piece;

[0081] ⑸ After the concrete reaches a certain strength, remove the casting formwork and it is done.

[0082] Example 2

[0083] The difference between this embodiment and embodiment 1 is that the floor slab boundary is calculated as fixed connection, and the existing reinforced concrete beam has a cross-sectional size of 300×600, a protective layer thickness of 20mm, a concrete grade of C20, and fc=9.6N / mm 2 ; New floor thickness 100mm, concrete grade C25, fcv = 2ft = 2.54N / mm 2 . According to the fixed connection calculation, the plate edge bending moment M = 8kN·m / m.

[0084] According to the structural requirements, the size of the force transmission beam was selected as 200mm×300mm.

[0085] A 1-meter slab was selected for calculation, and only the interface was roughened and chiseled. The direct shear capacity was 0.4×2.8×80×1000=89.6kN. After setting the force transfer beam, the direct shear capacity was 1.68×280×1000=470.4kN. For the intact cast-in-place integral component, the direct shear capacity was 2.8×80×1000=224.0kN.

[0086] The interface reinforcement is selected as C12@200mm×200mm. The bearing capacity requirement is verified by the plate edge bending moment, and the maximum tensile force of the interface reinforcement is calculated according to the formula N=M·y i / (n·∑y i 2 )=8×10 6 ×200 / (5×200 2)=80kN, the selected steel bar tension is 40kN, which is not satisfied. Reselect the steel bar as C12@120mm×200mm, the maximum tensile force of the interface steel bar, according to the formula N=M·y i / (n·∑y i 2 )=8×10 6 ×240 / (5×(240 2 +120 2 ))=5.3kN<40kN, meets the requirements.

[0087] The example shows that by setting the force transfer beam and interface reinforcement at the interface, the plate member can be designed as a fixed connection. It can be seen that after setting the force transfer beam and configuring the interface reinforcement, not only the interface shear force can be transmitted, but also the interface bending moment can be transmitted, which greatly enhances the design flexibility.

[0088] The implementation methods of the present invention are not limited to this. Based on the above content of the present invention, according to the common technical knowledge and customary means in the field, without departing from the above basic technical ideas of the present invention, the present invention also has various forms of modification, replacement or change, all of which fall within the scope of protection of the present invention.

Claims

1. A new and old concrete interface beam and plate component connection structure, characterized in that: It includes an existing beam-type component, a force-transmitting beam and a newly-built plate-type component. The force-transmitting beam is connected to the end of the newly-built plate-type component and cast integrally therewith. The outer side surface of the force-transmitting beam is fixed to the new and old concrete bonding surface of the existing beam-type component. The new and old concrete bonding surface is roughened. Interface steel bars are arranged between the force-transmitting beam and the existing beam-type component. One end of the interface steel bars is anchored into the force-transmitting beam, and the other end passes through the new and old concrete bonding surface and is implanted into the existing beam-type component. The width of the force-transmitting beam is greater than or equal to 200 mm, and the height of the force-transmitting beam is greater than twice the thickness of the newly-built plate-type component and greater than or equal to 300 mm.

2. The new and old concrete interface beam and plate member connection structure according to claim 1 is characterized in that: The cross-sectional shear bearing capacity of the force transmission beam is calculated according to the following formula: V=cA c +μ(A v f y +P c ) (1) V≥K1f c A c ,V=K1f c A c (2) V≥K2A c ,V=K2A c (3) in: A c —The bonding surface area of ​​new and old concrete; c—Roughness coefficient, the overall specimen is 2.80Mpa, the horizontal plate roughened specimen is 1.96Mpa, other roughened specimens are 1.68Mpa, and the non-roughened specimen is 0.525Mpa; A v — Area of ​​embedded reinforcement; μ—friction coefficient, 1.4 for the whole specimen, 1.0 for the horizontal plate roughened specimen, 1.0 for other roughened specimens, and 0.6 for the non-roughened specimen; f y —steel yield strength or steel design strength; P c — horizontal stress; f c —Average compressive strength of new and old concrete; K1—concrete section shear bearing capacity coefficient, 0.25 for the integral specimen, 0.3 for the horizontal plate roughened specimen, 0.25 for other roughened specimens, and 0.2 for the non-roughened specimen; K2—Ultimate shear strength coefficient of concrete, 10.5 for integral specimens, 12.6 for roughened horizontal plate specimens, 10.5 for other roughened specimens, and 5.6 for non-roughened specimens.

3. The new and old concrete interface beam and plate member connection structure according to claim 2 is characterized in that: The reinforcement ratio of the force-transfer beam is greater than or equal to 0.15%, and the stirrups are greater than or equal to C6@200mm.

4. The new and old concrete interface beam and plate member connection structure according to claim 3 is characterized in that: The steel bar area of ​​the interface steel bars arranged on the interface between the force transmission beam and the existing concrete member is greater than or equal to C10@200mmx200mm.

5. The new and old concrete interface beam and plate member connection structure according to claim 4 is characterized in that: The roughening depth is 6 to 10 mm, and the roughening rate is greater than 90%.

6. A construction method for the new and old concrete interface beam and plate member junction structure as claimed in claim 1, characterized in that The following steps are involved: ⑴ Carry out roughening treatment on the bonding surface of new and old concrete of existing beam-type components; (2) Tie the reinforcement of the newly built plate-type components and force-transfer beams, where the reinforcement of the end of the newly built plate-type components is tied together with the reinforcement of the force-transfer beams, and the interface reinforcement is tied so that one end of the interface reinforcement is anchored in the force-transfer beam and the other end is embedded in the existing beam-type components; ⑶Build pouring formwork; (4) Pour concrete into the casting formwork, and cast the new plate-type components and load-transmitting beams in one piece; ⑸ After the concrete reaches a certain strength, remove the casting formwork and it is done.

7. The construction method according to claim 6, characterized in that: The concrete grade of the newly-built plate-type components and force-transfer beams is at least one grade higher than the concrete grade of the existing beam-type components.

8. The construction method according to claim 7, characterized in that: In the step (1), after roughening, loose fragments and scum on the bonding surface of the new and old concrete are removed, and then the bonding surface of the new and old concrete is rinsed and moistened without leaving any visible water.

9. The construction method according to claim 8, characterized in that: In the step (4), a micro-expansion agent is added to the poured concrete.

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