Method for reinforcing perforated raft through steel plate
By equivalently raft slabs to reinforced concrete elastic foundation beams and adding steel plate skeletons to the opening position to form a new raft slab, the problems of uneven bottom of raft slabs, difficulty in binding steel bars and uneven stress in the prior art are solved. It has achieved simplification of construction and improved stress reliability.
Patent Information
- Application Number
- CN202411540500.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-31
- Publication Date
- 2025-02-18
AI Technical Summary
When the prior art is used to open holes in the raft foundation, the bottom of the raft is uneven, the steel bars are difficult to tie, the construction is complicated, and the local thickening leads to uneven stress, which affects the actual effect of the project.
By equivalently rafting without holes to reinforced concrete elastic foundation beams, the parameters of the steel plate skeleton are calculated, and the steel plate skeleton is added within the preset range of the opening position to form a new rafting plate and the stiffness of the new rafting plate is equivalent. It is the stiffness of steel-branched concrete beams.
The construction process is simplified, the construction difficulty and cost are reduced, the stress reliability of the raft is improved, and the uniformity of the overall stiffness and stress performance are ensured.
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Figure CN119466054A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of construction engineering, and in particular to a method for reinforcing a raft slab with a hole using a steel plate. Background Art
[0002] In current construction projects, when the raft foundation needs to be partially opened and lowered due to reasons such as elevator foundation pits, the existing common treatment measures are mainly to thicken the bottom of the raft to ensure that the overall thickness of the raft at any position is not reduced, such as Figure 1 As shown, the total height of the raft is H, and the depth of the opening is h. However, this treatment has obvious disadvantages: 1. The bottom of the raft is uneven: due to the local slope and thickening of the bottom of the raft, the surface of the bottom of the raft is uneven, which increases the difficulty and complexity of construction. 2. Difficulty in tying steel bars: The uneven bottom of the raft brings great difficulties to the tying of the bottom reinforcement of the raft, and it is difficult for workers to accurately arrange and fix the steel bars according to the design requirements. 3. The excavation interface of the raft foundation and the bearing layer bedrock of the foundation pit requires more precise and complex operations, causing construction difficulties. 4. The locally thickened raft causes the overall force of the raft to be complex and uneven, and the theoretical calculation is inconsistent with the actual engineering force. This is particularly evident for thick rafts. Summary of the invention
[0003] The purpose of the invention is to provide a method for reinforcing a raft slab with a hole by using a steel plate, so as to improve the stress-bearing reliability of the raft slab and simplify the construction process and reduce the cost.
[0004] The present invention provides a method for reinforcing a raft slab with a hole by using a steel plate, comprising:
[0005] The original raft slab without openings is equivalent to a reinforced concrete elastic foundation beam, and the stiffness of the original raft slab area to be opened is provided by the equivalent concrete beam, wherein the influence of the steel bars in the original raft slab on the moment of inertia and stiffness is not considered;
[0006] A steel plate skeleton is added within a preset range of the opening position of the opening raft slab to form a new raft slab, wherein the stiffness of the new raft slab is equivalent to the stiffness of a steel-reinforced concrete beam, and the stiffness of the new raft slab is provided by the concrete under the opening raft slab and the steel plate skeleton therein;
[0007] The original raft slab and the new raft slab are replaced by equivalent linear stiffness, and the parameters of the steel plate skeleton are calculated.
[0008] Optionally, the moment of inertia of the original raft is c satisfy: Its equivalent span is considered as 3 times the opening length B;
[0009] The stiffness of the original raft is E c *I c ;
[0010] Among them, E c is the elastic modulus of concrete, H is the original raft thickness, and B is the length of the hole on the raft.
[0011] Optionally, the steel plate skeleton includes two upper and lower reinforcing steel plates and a web connecting the two reinforcing steel plates, and the two reinforcing steel plates are provided with a concrete protective layer with a thickness of 150 mm;
[0012] The distance d between the two reinforcing steel plates satisfies: d = (h-2t f -150);
[0013] Moment of inertia of steel frame I s_part satisfy:
[0014] The stiffness of the steel plate skeleton is E s *I s_part ;
[0015] Among them, the elastic modulus of steel is E s , h is the raft thickness at the opening position, b f is the flange width of the reinforcing steel plate, t f is the thickness of the reinforcing steel plate, t w is the thickness of the web.
[0016] Optionally, the moment of inertia of the concrete part of the opening position of the opening raft slab is I c_part satisfy Its equivalent span is considered according to the opening width B;
[0017] The combined stiffness of the steel-reinforced concrete is E c I c_part +E s I s_part .
[0018] Optionally, the formula for replacing the equivalent beam line stiffness of the original raft slab with the new raft slab is:
[0019]
[0020] Optionally, the thickness of the reinforcing steel plate is f The thickness of the web t w Satisfy: t f / t w =1.0~3.0.
[0021] Optionally, the flange width b of the reinforcing steel plate f The length of the opening is equal to that of the opening in the raft slab.
[0022] Optionally, the length of the opening of the raft slab with a hole is equal to the width of the opening of the raft slab with a hole.
[0023] Optionally, the thickness of the web is w The value requirement is: t w ≥h / 250.
[0024] Optionally, the steel plate skeleton further includes bolts welded to corners of the reinforcing steel plates, and the bolts extend toward the concrete protective layer.
[0025] Compared with the prior art, the method of reinforcing the raft slab with a hole with a steel plate in this scheme adopts the equivalent line stiffness conversion method to convert the original raft slab into a reinforced concrete elastic foundation beam, whose stiffness is provided by the concrete and the original steel bars. The load is transferred to the foundation through the synergistic effect of the concrete and the original steel bars. Since the raft slab steel bars at the hole position do not change the original specification setting, the original raft slab and the new raft slab do not consider the influence of the steel bars on the overall stiffness in the conversion process. For the new raft slab whose thickness is weakened due to the hole, a steel plate is added within the preset range of the hole to enhance its stiffness. The weakened raft slab with a hole and the steel plate skeleton together form a structure similar to steel-framed concrete. The steel plate skeleton and the raft slab with a hole jointly bear the load, thereby ensuring the overall stiffness and force performance of the new raft slab. Through the equivalent line stiffness replacement method of the original raft slab and the new raft slab, the design parameters of the steel plate skeleton are obtained, and then the corresponding steel plate skeleton is set. The equivalent stiffness conversion method can reasonably calculate the required thickness of the steel plate and ensure the reinforcement effect. While simplifying the construction process and reducing construction difficulty and cost, the overall reliability of the raft's force is effectively guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 It is a schematic diagram of the method of thickening the bottom of the raft slab with a hole in the prior art;
[0027] Figure 2 This is a plan view of the raft opening arrangement for this scheme;
[0028] Figure 3 Structural diagram of adding steel plate skeleton to the raft with holes;
[0029] Figure 4 It is a partial cross-sectional schematic diagram of a steel plate skeleton;
[0030] Figure 5 It is a cross-sectional schematic diagram of setting short bolts on the reinforcing steel plate. DETAILED DESCRIPTION
[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0032] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be a connection between the two components. For ordinary technicians in this field, the specific meanings of the terms in the present invention can be understood according to specific circumstances.
[0033] The invention discloses a method for reinforcing a raft slab with a steel plate, the method comprising the following steps:
[0034] S1, the original raft slab without opening is equivalent to a reinforced concrete elastic foundation beam, the stiffness of the original raft slab in the area to be opened is provided by the stiffness of the equivalent concrete beam, wherein the influence of the steel bars in the original raft slab on the moment of inertia and stiffness is not considered;
[0035] S2, adding a steel plate skeleton within a preset range of the opening position of the opening raft slab to form a new raft slab, wherein the stiffness of the new raft slab is equivalent to the stiffness of a steel-reinforced concrete beam, and the stiffness of the new raft slab is provided by the concrete under the opening raft slab and the steel plate skeleton therein;
[0036] S3. Replace the original raft slab with the new raft slab by equivalent linear stiffness, and calculate the parameters of the steel plate skeleton.
[0037] The method of reinforcing the raft slab with holes with steel plates in this scheme adopts the equivalent line stiffness conversion method to convert the original raft slab into a reinforced concrete elastic foundation beam, whose stiffness is provided by the concrete and the original steel bars. The load is transferred to the foundation through the synergistic effect of the concrete and the original steel bars. Since the original specification setting of the raft slab steel bars at the hole position does not change, the influence of the steel bars on the overall stiffness of the original raft slab and the new raft slab is not considered in the conversion process. For the new raft slab whose thickness is weakened due to the hole, a steel plate is added within the preset range of the hole to enhance its stiffness. The weakened raft slab with holes and the steel plate skeleton together form a structure similar to steel-framed concrete. The steel plate skeleton and the raft slab with holes bear the load together, thereby ensuring the overall stiffness and force performance of the new raft slab. The design parameters of the steel plate skeleton are obtained by replacing the equivalent line stiffness of the original raft slab and the new raft slab, and then the corresponding steel plate skeleton is set. The equivalent stiffness conversion method can reasonably calculate the required thickness of the steel plate to ensure the reinforcement effect. While simplifying the construction process and reducing construction difficulty and cost, the overall reliability of the raft's force is effectively guaranteed.
[0038] Specifically, the moment of inertia of the original raft is I c satisfy: Its equivalent span is considered as 3 times the opening length B; Figure 2-3 As shown in the figure, the length of the foundation pit opening on the raft slab is B and the width is b. Since the raft slab is regarded as an elastic foundation beam lying on the bearing layer of the foundation, its force and deformation are different from those of ordinary slabs. In order to consider the influence of the raft slab within the influence range of the opening, the width of the opening and the width of the extended opening on each side are taken as the span of the original raft slab.
[0039] The stiffness of the original raft is E c *I c ;
[0040] Among them, E c is the elastic modulus of concrete, H is the original raft thickness, and B is the length of the hole on the raft.
[0041] Specifically, the steel plate skeleton includes two upper and lower reinforcing steel plates and a web or transverse ribs connecting the two reinforcing steel plates. The two reinforcing steel plates are provided with a 150mm thick concrete protective layer. It should be noted that the thickness of the bottom reinforcement protective layer of the general foundation raft slab is not less than 40mm. Considering the double-layer steel mesh, the diameter of the thick raft slab steel bar is generally not less than 20. At the same time, in order to facilitate the construction, steel bar binding is reserved, so 75mm is reserved at the top and bottom.
[0042] See also Figure 4 , the distance d between the two reinforcing steel plates satisfies: d = (h-2t f -150)
[0043] Moment of inertia of steel frame I s_part Equal to the width b f, the moment of inertia of a rectangle with a height of (h-150) minus the width of (b f -t w ), height is (h-2t f -150) rectangular moment of inertia (see Figure 4 ), we can get:
[0044]
[0045] The stiffness of the steel plate skeleton is E s *I s_part ;
[0046] Among them, the elastic modulus of steel is E s , h is the raft thickness at the opening position, b f is the flange width of the reinforcing steel plate, t f is the thickness of the reinforcing steel plate, t w is the thickness of the web.
[0047] Specifically, the moment of inertia of the concrete part of the opening position of the opening raft slab is I c_part satisfy Its equivalent span is considered according to the opening width B;
[0048] The combined stiffness of the equivalent steel reinforced concrete beam is E c I c_part +E s I s_part .
[0049] The linear stiffness of a beam is the bending stiffness of a beam per unit length. The calculation formula is: Linear stiffness (i) = bending stiffness (EI) / beam span (L), where the beam span is calculated as the equivalent span, L = 3B for the original raft, and L = B for the new raft.
[0050] Then for the original raft:
[0051] For new raft:
[0052] Specifically, the formula for replacing the equivalent beam line stiffness of the original raft slab with the new raft slab is:
[0053] i 原 =i 新 ,
[0054]
[0055] Here, it is calculated based on the linear stiffness of the beam and an equivalent calculation is performed based on the assumption that the linear stiffness of the original raft slab and the raft slab with steel plate are equal.
[0056] Specifically, the thickness t of the reinforcing steel plate is fThe thickness of the web t w Satisfy: t f / t w =1.0~3.0. The flange thickness of the I-beam is generally 1~2.5 times the web thickness. Considering the concrete filling in the middle, it can be relaxed to 3.0.
[0057] Specifically, the flange width b of the reinforcing steel plate is f The length of the opening is equal to that of the opening in the raft slab.
[0058] Specifically, the length of the opening of the raft with a hole is equal to the width of the opening of the raft with a hole.
[0059] Specifically, the thickness of the web is w The value requirement is: t w ≥h / 250. The thickness of the web of the combined steel structure can be To estimate, t w ≥h / 250 is sufficient.
[0060] See also Figure 5 The steel plate skeleton also includes bolts welded to the corners of the reinforcing steel plate, and the bolts extend toward the concrete cover. In order to ensure the close connection between the steel plate and the concrete, enhance the bonding force between the steel plate and the concrete, enable the two to work better together, prevent slippage or separation between the steel plate and the concrete, and effectively transfer shear force, short welded bolts can be set at the corners of the reinforcing steel plate, and the spacing and number of the bolts are determined according to calculations.
[0061] The method of reinforcing a raft slab with a hole with a steel plate of the present invention can be applied to the field of construction engineering. In the raft foundation of buildings such as super-high-rise buildings, super-deep underground garages, subway stations, etc., the method of the present invention can be applied to reinforce the raft slab with a hole, thereby ensuring the safety and convenience of the raft foundation design and construction.
[0062] Case Description:
[0063] The foundation type adopted by a super high-rise building is a raft foundation, with bedrock underneath. The raft thickness is 4.0m, the concrete strength is C35, the elevator pit is 1500mm deep, and the elevator pit size is 3000mmx3000mm.
[0064] 1. Determination of relevant parameters:
[0065] The elastic modulus of concrete E c =3.15×10 4 N / mm 2 :.
[0066] Elastic modulus of steel E s =2.1×10 5 N / mm 2 .
[0067] The original raft slab thickness is 4000mm, and the weakened raft slab thickness is 2500mm.
[0068] The width of the opening of the raft elevator foundation pit is B=b=3000mm.
[0069] Flange width b f =3000mm.
[0070] Web thickness t w =16mm.
[0071] Flange thickness: To be calculated.
[0072] 2. Calculate the stiffness of ordinary concrete "beam" (original raft slab):
[0073]
[0074] 3. Calculate the stiffness of the weakened "steel reinforced concrete beam" (weakened raft with steel plate):
[0075] Moment of inertia of the raft concrete portion after weakening:
[0076] Moment of inertia of steel frame
[0077]
[0078] Substitute into
[0079]
[0080] By numerically solving the one-variable multi-time equation, we can get t f =55.6mm, the thickness of the reinforcing steel plate can be 56mm.
[0081] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.
Claims
1. A method for reinforcing a raft slab with a steel plate, characterized in that: include: The original raft slab without openings is equivalent to a reinforced concrete elastic foundation beam, and the stiffness of the original raft slab in the area to be opened is provided by the stiffness of the raft slab equivalent concrete beam, wherein the influence of the steel bars in the original raft slab on the moment of inertia and stiffness is not considered; A steel plate skeleton is added within a preset range of the opening position of the opening raft slab to form a new raft slab, wherein the stiffness of the new raft slab is equivalent to the stiffness of a steel-reinforced concrete beam, and the stiffness of the new raft slab is provided by the concrete under the opening raft slab and the steel plate skeleton therein; The original raft slab and the new raft slab are replaced by beam equivalent line stiffness, and the parameters of the steel plate skeleton are calculated.
2. The method for reinforcing a raft slab with a hole by a steel plate according to claim 1, characterized in that: The moment of inertia of the original raft is I c satisfy: Its equivalent span is considered as 3 times the opening length B; The stiffness of the original raft is E c *I c ; Among them, E c is the elastic modulus of concrete, H is the original raft thickness, and B is the length of the hole on the raft.
3. The method for reinforcing a raft slab with a hole by a steel plate according to claim 2, characterized in that: The steel plate skeleton includes two upper and lower reinforcing steel plates and a web connecting the two reinforcing steel plates, and the two reinforcing steel plates are provided with a concrete protective layer with a thickness of 150 mm; The distance d between the two reinforcing steel plates satisfies: d = (h-2t f -150); Moment of inertia of steel frame I s_part satisfy: The stiffness of the steel plate skeleton is E s *I s_part ; Among them, the elastic modulus of steel is E s , h is the raft thickness at the opening position, b f is the flange width of the reinforcing steel plate, t f is the thickness of the reinforcing steel plate, t w is the thickness of the web.
4. The method for reinforcing a raft slab with a hole by using a steel plate according to claim 3, characterized in that: The moment of inertia of the concrete part of the opening position of the opening raft is I c_part satisfy Its equivalent span is considered according to the opening width B; The combined stiffness of the steel-reinforced concrete is E c I c_part +E s I s_part .
5. The method for reinforcing a raft slab with a hole by using a steel plate according to claim 4, characterized in that: The formula for replacing the equivalent beam line stiffness of the original raft slab with the new raft slab is:
6. The method for reinforcing a raft slab with a hole by a steel plate according to claim 3, characterized in that: The thickness of the reinforcing steel plate is f The thickness of the web t w Satisfy: t f / t w =1.0~3.
0.
7. The method for reinforcing a raft slab with a hole by a steel plate according to claim 3, characterized in that: The flange width b of the reinforcing steel plate f The length of the opening is equal to that of the opening in the raft slab.
8. The method for reinforcing a raft slab with a hole by a steel plate according to claim 3, characterized in that: The length of the opening of the raft slab with a hole is equal to the width of the opening of the raft slab with a hole.
9. The method for reinforcing a raft slab with a hole by a steel plate according to claim 3, characterized in that: The thickness of the web is t w The value requirement is: t w ≥h / 250.
10. The method for reinforcing a raft slab with a hole by a steel plate according to claim 3, characterized in that: The steel plate frame also includes bolts welded to the corners of the reinforcing steel plates, and the bolts extend toward the concrete protective layer.