A method for adding an overhead floor to the first floor of a building without a basement by strengthening its foundation

Abstract

A method for adding an elevated floor to the first floor of a building without a basement foundation reinforcement, comprising the following steps: preliminarily determining the supporting structure to be used for the elevated floor; establishing a calculation model for the first-floor elevated floor structure; calculating the vertical reaction force at the column bottom; applying the vertical reaction force at the column bottom as an increment to the overall calculation model of the original structure to verify whether the original foundation meets the requirements; preliminarily determining the specifications of the anchor piles that need to be added and the characteristic value of the vertical bearing capacity of a single pile; preliminarily determining the position and number of the anchor piles; calculating the vertical reaction force at the column bottom; and finally determining the calculation model for the elevated floor structure. The present invention avoids the reinforcement of the original foundation beams and foundation of such buildings, adopts the method of adding a load support point in the middle of the elevated slab, and provides a design method for adding an elevated slab to the first floor of such buildings by considering the stress conditions of the elevated slab at different construction stages. This method avoids the reinforcement of the original foundation beams and foundation, and has a clear force transmission path, a simple and easy-to-operate structure, and can be promoted and used after being tested in engineering practice.

Description

Technical Field

[0001] The invention relates to the field of structural reinforcement and reconstruction, and in particular to a design method for adding an overhead floor to the first floor of a building without a basement, which can avoid reinforcing the original foundation beams and foundation. Background Art

[0002] Among the existing buildings, there are a large number of public buildings with no basements and no elevated slabs on the first floor, and their foundations are pile foundations (the surface soil of such buildings is generally poor). Due to changes in usage requirements or excessive consolidation and settlement of the soil under the indoor ground, it is necessary to add elevated slabs on the ground in the indoor backfill area to solve the problem of safe use in the future. The deadweight and live load of the added elevated slabs will inevitably cause an increase in the overall structural load. The conventional treatment method is to add cast-in-place elevated slabs and reinforce the original structural foundation beams and foundations supporting the floor slabs. Since the original foundation beams and foundations are buried in the backfill, excavation operations are required for reinforcement, and the excavation depth must reach the bottom surface of the foundation or the bottom surface of the foundation beam to facilitate reinforcement construction. The construction is very inconvenient and the reinforcement operation space is narrow, the construction quality is difficult to guarantee, and it is easy to cause safety hazards. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above-mentioned shortcomings and to propose a method for adding an elevated floor to the first floor without reinforcing the foundation of a building without a basement.

[0004] To achieve the above object, the present invention is implemented through the following technical solution: a design method for adding an overhead floor to the first floor to avoid foundation reinforcement of a building without a basement, comprising the following steps:

[0005] (1) Review the height of the original structure's indoor elevation from the foundation surface and foundation beam surface, and preliminarily determine whether the proposed overhead floor will adopt a beam, slab, column support structure or a slab, column support structure. That is, if the foundation surface under the original structure column meets the conditions for setting up the new foundation beam, the proposed overhead floor will adopt a beam, slab, column support structure; if the foundation surface under the original structure column is close to the finished surface of the overhead slab and it is impossible to set up the new foundation beam, the proposed overhead floor will adopt a slab, column support structure.

[0006] The beam, slab, and column support structure described in this invention refers to the support structure consisting of the original structural columns with foundations, the newly added foundation beams between the original structural columns with foundations, the newly added elevated slab enclosed by the newly added foundation beams, and the newly added support points (new anchor piles and pile caps) in the middle of the newly added elevated slab. The slab and column support structure refers to the support structure consisting of the original structural columns with foundations, the newly added elevated slab, and the newly added support points (new anchor piles and pile caps) in the middle of the newly added elevated slab. The newly added elevated slab refers to the elevated slab installed on the ground floor of a building without a reinforced basement foundation.

[0007] (2) Taking the foundation with structural columns in the original design as the support point, a calculation model of the first-floor elevated layer structure is established according to the scope of the proposed additional elevated slab.

[0008] (3) Calculate the vertical reaction force at the base of the column based on the constant and live loads under normal use conditions input into the model.

[0009] (4) The calculated vertical reaction force at the base of the column is added as an increment to the overall calculation model of the original structural design to verify whether the original foundation meets the requirements.

[0010] (5) Based on the geological report within the plane range of the elevated floor, the specifications of the anchor piles that need to be added and the characteristic values ​​of the vertical bearing capacity of the single pile are preliminarily determined.

[0011] (6) Based on the review results of (4) and (5), the increment of the original column bottom reaction force is controlled according to the principle of not reinforcing the original foundation, and the position and number of anchor piles are preliminarily determined.

[0012] (7) Based on the result of (6), the anchor piles are assumed to be columns (the column cross-section size is the same as the anchor pile cross-section size) and are arranged as new support points in the first-floor elevated layer structure model to recalculate the vertical reaction force at the column base.

[0013] (8) Repeat steps (4), (6), and (7) until the bearing capacity of the original structure foundation meets the requirements (no reinforcement is required).

[0014] (9) Determine the calculation model of the overhead structure based on the results of (8).

[0015] (10) The load calculation is input according to the calculation model of (9). At this time, the calculation of the mezzanine floor only considers the load during the construction period, including the self-weight of the mezzanine floor and the live load required for the anchor pile construction.

[0016] (11) The reaction force value of the newly added support point is obtained based on the calculation result of (10). The temporary independent column foundation area, treatment range, and independent column foundation height are calculated based on the foundation bearing capacity obtained after local treatment of the surface foundation soil at the support point. The independent column foundation area here should deduct the area of ​​the anchor pile hole to be reserved.

[0017] (12) According to the calculation model of (9), the temporary independent column foundation size determined in (11) is input into the calculation model as the column cap and the size and height of the column cap are calculated to check whether they meet the shear or shear requirements. When the column base area and height calculated in (11) do not meet the requirements, the concrete strength can be increased or the column cap can be increased to meet the calculation requirements. The range and elevation of the surface layer obtained in (11) that need to be processed are adjusted according to the final column cap size and height.

[0018] (13) Based on the structural model of (12), the constant and live loads of the mezzanine floor under normal use are input to calculate the column base vertical reaction value of the newly added support point and the mezzanine floor reinforcement. The column base vertical reaction value is the final required single pile vertical bearing capacity characteristic value. When designing the specific pile length, in addition to considering the influence of the soil's side and end resistance on the pile, the influence of the pile's vertical stiffness in the soil (i.e., the K value) should also be considered.

[0019] (14) According to the structural model of (12), the calculation of the elevated floor only considers the load during the construction period, including the self-weight of the elevated floor and the live load required for the construction of anchor piles, and the secondary reinforcement of the elevated floor is calculated.

[0020] (15) The actual reinforcement of the overhead layer is the envelope value of reinforcement one and reinforcement two calculated in (13) and (14).

[0021] Furthermore, the characteristic value of the vertical bearing capacity of a single anchor pile and the number of anchor piles can be adjusted according to the on-site soil conditions and the bearing capacity of the foundations under each column of the original structure.

[0022] Furthermore, before the anchor pile head is sealed and stressed, the pile cap serves as an independent column base and acts as a temporary fulcrum.

[0023] Furthermore, after the construction of anchor piles, the long-term consolidation of the soil below the newly added elevated layer may cause the elevated plate to separate from the soil. When the anchor piles take effect, the pile cap can ensure that the reverse shearing of the anchor piles meets the requirements, while ensuring that the forward shearing of the elevated plate along the edge of the pile cap meets the requirements.

[0024] Furthermore, if the plane dimensions of the foundation surface under the original structural column meet the requirements for the length of the newly added foundation beam, the newly added foundation beam supporting the newly added overhead slab can avoid the original structural column and be directly placed above the foundation surface under the column to avoid planting reinforcement.

[0025] Furthermore, if the new foundation beam supporting the newly added elevated slab avoids the original structural column and is placed directly above the foundation surface under the column, the impact of the eccentric placement of the beam on the original foundation needs to be considered (input the eccentric bending moment load in the overall calculation model of the original structural design).

[0026] Furthermore, if the foundation surface under the original structural column is close to the finished surface of the elevated slab and it is impossible to set up a new foundation beam, the position and number of anchor piles can be flexibly adjusted to form a slab and column supporting structure to meet the design requirements.

[0027] The present invention also provides a construction method for adding an overhead floor to the first floor without reinforcing the foundation of a building without a basement, the construction method comprising the following steps:

[0028] (1) Treat the surface foundation soil within the column cap range according to the column cap positioning and size, and improve the foundation bearing capacity within the column cap range to meet the temporary foundation bearing capacity design requirements during construction;

[0029] (2) Excavate the foundation trench according to the shape of the soil surface of the overhead layer and pour the cushion layer. The cushion layer uses a 100mm thick C15 cushion layer;

[0030] (3) Tie the steel bars of the overhead layer components according to the overhead layer reinforcement diagram provided by the design;

[0031] (4) Reserve holes for anchor pile construction and pour concrete for the overhead layer;

[0032] (5) After the concrete strength grade meets the requirements, partially remove the cushion layer at the reserved hole and carry out anchor pile construction;

[0033] (6) After the anchor pile construction is completed, the reserved construction hole for the anchor pile shall be closed according to the design requirements.

[0034] This invention avoids the need to reinforce the foundation beams and foundations of such buildings. Instead, it adds a load-bearing fulcrum in the middle of the elevated slab. By considering the stresses on the elevated slab at different construction stages, this design method for adding a first-floor elevated slab to such buildings is presented. This method avoids reinforcing the existing foundation beams and foundations, and features a clear force transmission path, a simple and easy-to-operate structure, and has been proven in engineering practice, indicating widespread adoption. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A plan layout of the overhead floor for the supporting structure of beams, slabs and columns;

[0036] Figure 2 The plan layout of the elevated floor for the slab and column supporting structure;

[0037] Figure 3 for Figure 1 、 Figure 2 AA cross-section of

[0038] Figure 4 for Figure 1 、 Figure 2 BB cross-section diagram;

[0039] Figure 5 for Figure 1 CC cross-section diagram;

[0040] Figure 6 for Figure 2 DD cross-section diagram. DETAILED DESCRIPTION

[0041] The present invention is further described below with reference to the accompanying drawings and specific implementation examples. The accompanying drawings are for illustrative purposes only and are schematic, not physical, representations. They should not be construed as limiting this patent. To better illustrate the embodiments of the present invention, some components in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the dimensions of actual products. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted from the accompanying drawings.

[0042] like Figure 1-6 As shown, the present invention includes: original structure foundation 1, newly added foundation beam 2, newly added overhead plate 3, newly added anchor pile 4, newly added pile cap 5, pile cap reinforcement 6, newly added overhead plate reinforcement 7, anchor pile construction opening 8, newly added foundation beam reinforcement 9, original structure foundation beam 10, original structure column 11, cushion layer 12, brick membrane 13.

[0043] The present invention provides a design method for adding an overhead floor to the first floor to avoid foundation reinforcement of a building without a basement, comprising the following steps:

[0044] (1) Review the height of the original structure's indoor elevation from the foundation surface and foundation beam surface, and preliminarily determine whether the proposed overhead floor will adopt a beam, slab, column support structure or a slab, column support structure.

[0045] The beam, slab, and column support structure consists of newly added foundation beams between the structural columns originally designed with foundations, a newly added overhead slab enclosed by the newly added foundation beams, the original foundation supporting the newly added foundation beams, and newly added support points (new anchor piles and pile caps) in the middle of the newly added overhead slab.

[0046] The slab and column supporting structure consists of the newly added elevated slab, the original designed foundation supporting the newly added elevated slab, and the newly added supporting points in the middle of the newly added elevated slab (newly added anchor piles and pile caps).

[0047] (2) Taking the foundation with structural columns in the original design as the support point, a calculation model of the first-floor elevated layer structure is established according to the scope of the proposed additional elevated slab.

[0048] (3) Calculate the vertical reaction force at the base of the column based on the constant and live loads under normal use conditions input into the model.

[0049] (4) The calculated vertical reaction force at the base of the column is added as an increment to the original design calculation model to verify whether the original foundation meets the requirements.

[0050] (5) Based on the geological report within the plane range of the elevated floor, the specifications of the anchor piles that need to be added and the characteristic values ​​of the vertical bearing capacity of the single pile are preliminarily determined.

[0051] (6) Based on the review results of (4) and (5), the increment of the original column bottom reaction force is controlled according to the principle of not reinforcing the original foundation, and the position and number of anchor piles are preliminarily determined.

[0052] (7) Based on the result of (6), the anchor piles are assumed to be columns (the column cross-section size is the same as the anchor pile cross-section size) and are arranged as new support points in the first-floor elevated layer structure model to recalculate the vertical reaction force at the column base.

[0053] (8) Repeat steps (4), (6), and (7) until the bearing capacity of the original structure foundation meets the requirements (no reinforcement is required).

[0054] (9) Determine the calculation model of the overhead structure based on the results of (8).

[0055] (10) The load calculation is input according to the calculation model of (9). At this time, the calculation of the mezzanine floor only considers the load during the construction period, including the self-weight of the mezzanine floor and the live load required for the anchor pile construction.

[0056] (11) The reaction force value of the newly added support point is obtained based on the calculation result of (10). The temporary independent column foundation area, treatment range, and independent column foundation height are calculated based on the foundation bearing capacity obtained after local treatment of the surface foundation soil at the support point. The independent column foundation area here should deduct the area of ​​the anchor pile hole to be reserved.

[0057] (12) According to the calculation model of (9), the temporary independent column foundation size determined in (11) is input into the calculation model as the column cap and the size and height of the column cap are calculated to check whether they meet the shear or shear requirements. When the column base area and height calculated in (11) do not meet the requirements, the concrete strength can be increased or the column cap can be increased to meet the calculation requirements. The range and elevation of the surface layer obtained in (11) that need to be processed are adjusted according to the final column cap size and height.

[0058] (13) Based on the structural model of (12), the constant and live loads of the mezzanine floor under normal use are input to calculate the column base vertical reaction value of the newly added support point and the mezzanine floor reinforcement condition 1. The column base vertical reaction value is the final required single pile vertical bearing capacity characteristic value. When designing the specific pile length, in addition to considering the influence of the soil on the side and end resistance of the pile, the influence of the vertical stiffness of the pile in the soil (i.e., the K value) should also be considered.

[0059] (14) According to the structural model of (12), the calculation of the elevated floor only considers the load during the construction period, including the self-weight of the elevated floor and the live load required for the construction of anchor piles, and the calculation results in the second situation of the elevated floor reinforcement.

[0060] (15) The actual reinforcement of the overhead layer is the envelope value of reinforcement one and reinforcement two calculated in (13) and (14).

[0061] The vertical bearing capacity characteristic value of a single anchor pile and the number of anchor piles can be adjusted according to the on-site soil conditions and the bearing capacity arrangement of the foundations under each column of the original structure.

[0062] Before the anchor pile head is closed and stressed, the pile cap acts as an independent column base and acts as a temporary fulcrum.

[0063] After the construction of anchor piles, the long-term consolidation of the soil under the newly added elevated layer may cause the elevated plate to separate from the soil. When the anchor piles take effect, the pile cap can ensure that the reverse shear of the anchor piles meets the requirements, and at the same time ensure that the forward shear of the elevated plate along the edge of the pile cap meets the requirements.

[0064] If the plane size of the foundation surface under the original structural column meets the requirements for the length of the newly added beam, the newly added foundation beam supporting the newly added overhead slab can avoid the original structural column and be placed directly above the foundation surface under the column to avoid planting reinforcement.

[0065] If the new foundation beams added to support the newly added elevated slab avoid the original structural columns and are placed directly above the foundation surface under the columns, the impact of the eccentric placement of the beams on the original foundation must be considered (input the eccentric bending moment load in the overall calculation model of the original structural design).

[0066] If the foundation surface under the original structural column is close to the finished surface of the elevated slab and it is impossible to set up a new foundation beam, the position and number of anchor piles can be flexibly adjusted to form a slab and column supporting structure to meet the design requirements.

[0067] Examples, such as Figure 1 、 Figure 2 As shown, for a public building without a basement and an elevated floor on the first floor, it is necessary to add an elevated slab 3 in the indoor backfill area due to changes in usage requirements or excessive consolidation settlement of the soil under the indoor ground.

[0068] The present invention provides a design method for adding an overhead floor to the first floor to avoid foundation reinforcement of a building without a basement. The construction method comprises the following steps:

[0069] (1) Treat the surface foundation soil within the scope of the newly added pile cap 5 according to its location and size, and improve the foundation bearing capacity within the scope of the newly added pile cap 5 so that it meets the design requirements of the temporary foundation bearing capacity during construction.

[0070] (2) Excavate the foundation trench according to the size of the newly added foundation beam 2 and the newly added pile cap 5, pour the cushion layer 12, use a 100mm thick C15 cushion layer, and construct the brick membrane 13.

[0071] (3) Tie the overhead layer reinforcement according to the newly added pile cap reinforcement 6, newly added overhead slab reinforcement 7 and newly added foundation beam reinforcement 9 provided in the design.

[0072] (4) Reserve an opening 8 for the anchor pile construction and pour concrete for the newly added overhead slab 3.

[0073] (5) After the concrete strength grade meets the requirements, the cushion layer at the reserved hole is partially broken and the construction of the new anchor pile 4 is carried out.

[0074] (6) After the construction of the new anchor pile 4 is completed, the anchor pile construction hole 8 shall be closed as required, and a higher grade of micro-expansive concrete shall be used for construction.

Claims

1. A method for adding an overhead floor to the first floor of a building without a basement to avoid foundation reinforcement, characterized in that: The following steps are involved: (1) Review the height of the first floor indoor elevation from the foundation surface and foundation beam surface of the original structure, and preliminarily determine whether the proposed overhead floor will adopt a beam, slab and column support structure or a slab and column support structure; (2) Taking the foundation with structural columns in the original design as the support point, a calculation model of the first-floor overhead layer structure is established according to the scope of the proposed additional overhead slab; (3) Calculate the vertical reaction force at the base of the column based on the constant and live loads under normal use conditions inputted from the calculation model of the first-floor overhead structure; (4) Apply the calculated column bottom vertical reaction force as an increment to the original structure overall calculation model to verify whether the original foundation meets the requirements; (5) Calculate and preliminarily determine the specifications of the anchor piles that need to be added and the characteristic value of the vertical bearing capacity of the single pile based on the geological report within the plane range of the elevated floor; (6) Based on the results of steps (4) and (5), the original column bottom reaction force increment is controlled according to the principle of no reinforcement of the original foundation, and the position and number of anchor piles are preliminarily determined; (7) Based on the result of step (6), the anchor piles are assumed to be columns and arranged as new support points in the first-floor overhead structure model to recalculate the vertical reaction force at the column base; (8) Repeat steps (4), (6), and (7) until the bearing capacity of the original structure foundation meets the requirements; (9) Determine the calculation model of the overhead layer structure based on the results of step (8); (10) Input the load calculation according to the calculation model of step (9). At this time, the calculation of the overhead layer only considers the load during the construction period, including the deadweight of the overhead layer and the live load required for the anchor pile construction; (11) The reaction force value of the newly added support point is obtained based on the calculation result of step (10). The temporary independent column foundation area, treatment range and independent column foundation height are calculated by the foundation bearing capacity obtained by local treatment of the surface foundation soil at the support point. The independent column foundation area here should deduct the area of ​​the anchor pile hole to be reserved; (12) According to the calculation model of step (9), the temporary independent column foundation size determined in step (11) is input into the calculation model as the column cap and the size and height of the column cap are calculated to check whether they meet the shear or shear requirements. If the column base area and height calculated in step (11) do not meet the requirements, the concrete strength can be increased or the column cap can be increased to meet the calculation requirements. The range and elevation of the surface layer to be processed obtained in step (11) are adjusted according to the final determined column cap size and height. (13) After adjusting the surface area and elevation required to be processed obtained in step (11) according to the final column cap size and height in step (12), input the constant and live loads of the overhead layer in normal use, and calculate the column bottom vertical reaction value of the newly added support point and the overhead layer reinforcement. The column bottom vertical reaction value is the final required single pile vertical bearing capacity characteristic value. When designing the specific pile length, in addition to considering the influence of the soil on the side and end resistance of the pile, the influence of the vertical stiffness of the pile in the soil should also be considered. (14) After adjusting the surface treatment range and elevation obtained in step (11) according to the final column cap size and height in step (12), the calculation of the overhead layer only considers the load during construction, including the overhead layer self-weight and the live load required for anchor pile construction, and calculates the overhead layer reinforcement II; (15) The actual reinforcement of the overhead layer is the envelope value of reinforcement 1 and reinforcement 2 calculated in steps (13) and (14).

2. The method according to claim 1, wherein: The characteristic value of the vertical bearing capacity of a single anchor pile and the number of anchor piles are adjusted according to the on-site soil conditions and the bearing capacity of the foundations under each column of the original structure.

3. The method according to claim 1, wherein: Before the anchor pile head is sealed and loaded, the pile cap acts as a temporary fulcrum as an independent column base.

4. The method according to claim 1, wherein: If the plane size of the foundation surface under the original structural column meets the requirements for the length of the newly added foundation beam, the newly added foundation beam supporting the newly added overhead slab will avoid the original structural column and be placed directly above the foundation surface under the column to avoid planting reinforcement.

5. The method according to claim 4, characterized in that: If the new foundation beam supporting the newly added elevated slab avoids the original structural column and is placed directly above the foundation surface under the column, the impact of the eccentric placement of the beam on the original foundation needs to be considered.

6. The method according to claim 1, wherein: If the foundation surface under the original structural column is close to the finished surface of the elevated slab and it is impossible to set up a new foundation beam, the position and number of anchor piles can be flexibly adjusted to form a slab and column supporting structure to meet the design requirements.

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