A method for converting a thick plate design

Abstract

The application discloses a kind of conversion thick plate design methods, it is related to building engineering technical field, to improve that concrete can be based on in multiaxial compression state compression strength and shear bearing capacity, with shear span ratio as reference index, conversion thick plate section punching, shear checking method is improved;Improved slab strip division method and the method for calculating internal force considering two-way bending moment and torsional moment combination effect is used.Compared with conventional technology, the application fully taps the potential of shear bearing capacity improvement of concrete in multiaxial compression state, realizes the optimization of conversion plate thickness, and the thickness of conversion plate can be optimized by 50% under extreme conditions;The slab strip division of the application is clearer, more reasonable, and the design result is safer with deformation control and reinforcement structure requirements.

Description

Technical Field

[0001] This invention relates to the field of building engineering technology, specifically a method for designing thick plates. Background Technology

[0002] Thick plate transfer structures began to be used in the 1970s. However, due to insufficient research in my country, there are strict restrictions on thick plate transfer structures, which has affected their widespread use.

[0003] The biggest problem with current transfer slab design is that the slab thickness is too large, which leads to the concentration of mass in the transfer layer and is not conducive to the seismic resistance of the structure. The reinforcement design of the transfer slab is based on the transfer beam structure, which leads to complex construction, a large increase in material usage, and fails to make full use of the favorable conditions of the thick slab space for stress, thus failing to reflect the advantages of the slab transfer structure in terms of simple construction and convenient construction. Summary of the Invention

[0004] The purpose of this invention is to provide a design method for converting thick plates in order to solve existing problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for designing thick plates, comprising:

[0006] S1: Estimation of the thickness of the transfer slab. The initial height of the cross-section of the thicker transfer slab can be taken as 0.2 to 0.3 times the clear span of the shorter side of the floor slab.

[0007] S2: Using an elastic design method, the internal forces and deformation distribution of the transfer plate are calculated and analyzed through a three-dimensional spatial model;

[0008] S3: Check the allowable vertical deformation of the transfer plate and the suitability of its bending, shear, and punching shear sections;

[0009] S4: After the plate thickness is determined, the plate strips can be divided according to the finite element analysis results for design. The plate strips are divided into column mid-span plate strips, column edge plate strips and mid-span plate strips according to their relative positional relationship with the column support, and the internal forces of the plate strips are calculated respectively.

[0010] S5: Substitute the slab strips, etc., into rectangular beams for reinforcement calculation;

[0011] S6: Draw the reinforcement diagram of the transfer slab and check the structural requirements.

[0012] As a further aspect of the present invention: the conversion thick plate is designed as a thick floor slab in a building structure to support the vertical components above it that cannot be directly grounded, and to transfer the relevant loads to the vertical components and foundation below it.

[0013] As a further aspect of the present invention: the span-to-thickness ratio of the conversion plate is not greater than 5, and the span-to-thickness ratio is the ratio of the net span of the short side of the floor slab to the thickness of the floor slab.

[0014] As a further aspect of the present invention: in the three-dimensional spatial model, the conversion plate should be a three-dimensional shell unit that can take into account lateral shear deformation.

[0015] As a further aspect of the present invention: the allowable value of vertical deformation of the conversion plate should not exceed 1 / 800 of the calculated span of the long side of the floor slab, and the deformation calculation should deduct the influence of the support compression deformation.

[0016] As a further aspect of the present invention: the calculation span is l 0, its calculated value is l n + min(0.5) S w 0.5 h s ),in S w The width of the supporting column or wall. h s This refers to the thickness of the conversion plate.

[0017] As a further aspect of the present invention: the reinforcement ratio of longitudinal bending steel bars when estimating the thickness of the transfer slab. ρ s The thickness of the transfer plate should not exceed 1%, and when estimating the shear span ratio of the calculated section, it should be no greater than 1%. λ When the shear span ratio is less than 2.5, a section shear resistance check is performed; when the section shear span ratio is calculated... λ When the value is greater than 2.5, the cross-section punching shear resistance is checked.

[0018] As a further embodiment of the present invention: the column center plate strip refers to a strip-shaped area with the same width as the column cross-section along the center line of the column; the column side plate strip refers to a strip-shaped area of ​​a certain width distributed on one side of the side column and both sides of the center column, taking the larger value of 1m or half the plate thickness; and the mid-span plate strip is a strip-shaped area located between the column side plate strips.

[0019] As a further aspect of the present invention: the internal force of the slab strip is the bending moment design value after comprehensively considering the combined effect of the bidirectional bending moment and torque of the floor slab, and is the design basis for the bending moment reinforcement of the thick plate section.

[0020] As a further embodiment of the present invention: the width of the rectangular beam is equal to the width of the slab, the height is equal to the thickness of the slab, and the stirrups of the rectangular beam can be tie bars.

[0021] As a further aspect of this invention: the design internal force of the slab strip in the column can be taken from the column edge or the influence of the rigid zone can be considered, which can achieve the effect of peak reduction. The reinforcement of the slab strip in the column and the slab strip at the column edge are both based on the envelope result of the two. The reinforcement of the slab strip in the middle span can be directly based on the internal force envelope result of each slab strip in the middle span, or it can be reinforced separately according to the internal force calculation result of each slab strip. The width range of the peak bending moment reinforcement of the slab strip should not be less than the thickness of the slab. The bending moment calculation of the slab strip should comprehensively consider the combined effect of the two-way bending moment and torque of the floor slab.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. The advantages of this invention lie in its consideration of improving the compressive strength and shear capacity of the concrete between the shear wall and column support supported by the transfer slab under triaxial or biaxial compression conditions. By using the shear span ratio of the calculated section as a control condition, the potential of the concrete's shear capacity under different compression conditions is explored, thereby optimizing the thickness of the transfer slab. This solves the problem of excessively thick transfer slabs caused by conventional designs that do not differentiate between concrete stress states and use a uniform standard for punching shear calculations. Compared with conventional technologies, the thickness of the transfer slab can be optimized by 50% under extreme conditions.

[0024] 2. Another advantage of this invention is that it refines the slab strip division rules and adopts slab strip design bending moment, splitting the "column-top slab strip" in conventional technology into "column-center slab strip" and "column-edge slab strip," and performing an envelope design; the width of the "mid-span slab strip" is limited to not exceeding the slab thickness. Compared with conventional technology, the slab strip division basis is clearer and more reasonable; the method of calculating internal forces considering the combined effect of bidirectional bending moment and torque of the floor slab is used, resulting in a more comprehensive consideration of structural internal force calculations and a safer design result.

[0025] 3. The technology of this invention can effectively reduce the thickness of the conversion plate and the amount of material used, reduce the difficulty of node construction, and achieve significant overall benefits.

[0026] 4. The conversion plate structure in this invention reduces the constraints on the arrangement of the upper structure, helps to improve product quality, and has broad prospects for promotion. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the conversion structure in the conversion thick plate design method described in this invention;

[0028] Figure 2 This is a schematic diagram of the strip division method in the thick plate design method of the present invention;

[0029] Figure 3 This is a design flowchart of a thick plate conversion design method according to the present invention;

[0030] Figure 4This is a schematic diagram of unit stress in a thick plate conversion design method described in this invention.

[0031] In the diagram: 1. Superstructure; 2. Transfer plate; 3. Transfer column; 21. Column mid-slab strip; 22. Column edge plate strip; 23. Mid-span plate strip. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this invention, it should be noted that unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," and "set up" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The following describes embodiments of the invention based on its overall structure.

[0034] Reference Figures 1 to 3 In the embodiments of the present invention:

[0035] Example 1

[0036] A method for designing thick plates, comprising:

[0037] S1: Estimation of the thickness of the transfer slab. The initial height of the cross-section of the thicker transfer slab can be taken as 0.2 to 0.3 times the clear span of the shorter side of the floor slab.

[0038] S2: Using an elastic design method, the internal forces and deformation distribution of the transfer plate are calculated and analyzed through a three-dimensional spatial model;

[0039] S3: Check the allowable vertical deformation of the transfer plate and the suitability of its bending, shear, and punching shear sections;

[0040] S4: After the plate thickness is determined, the plate strips can be divided according to the finite element analysis results for design. The plate strips are divided into column mid-span plate strips, column edge plate strips and mid-span plate strips according to their relative positional relationship with the column support, and the internal forces of the plate strips are calculated respectively.

[0041] S5: Substitute the slab strips, etc., into rectangular beams for reinforcement calculation;

[0042] S6: Draw the reinforcement diagram of the transfer slab and check the structural requirements.

[0043] A transfer slab is a floor slab within a building structure designed as a thick slab to support vertical members that cannot directly touch the ground above it, and to transfer related loads to the vertical members and foundation below. The span-to-thickness ratio of the transfer slab should not exceed 5, which is the ratio of the clear span of the shorter side of the slab to its thickness. In the 3D spatial model, the transfer slab should use 3D shell elements capable of considering lateral shear deformation. The allowable vertical deformation of the transfer slab should not exceed 1 / 800 of the calculated span of the longer side of the slab, and the deformation calculation should deduct the influence of support compression deformation. The calculated span... l 0, its calculated value is l n + min(0.5) S w 0.5 h s ),in S w The width of the supporting column or wall. h s The thickness of the transfer slab; the reinforcement ratio of longitudinal bending steel bars when estimating the thickness of the transfer slab. ρ s The thickness of the transfer slab should not exceed 1% when calculating the shear span ratio of the cross-section. λ When the shear span ratio is less than 2.5, a section shear resistance check is performed; when the section shear span ratio is calculated... λ When the value is greater than 2.5, the punching shear resistance of the section should be checked. The slab strip in the column refers to the strip-shaped area with the same width as the side length of the column section along the center line of the column. The slab strip on the edge of the column refers to the strip-shaped area of ​​a certain width distributed on one side of the edge column and both sides of the middle column. The value is taken as the larger of 1m or half the thickness of the slab. The slab strip in the middle span is the strip-shaped area located between the slab strips on the column and the edge of the column. The internal force of the slab strip is the design value of the bending moment after comprehensively considering the combined effect of the two-way bending moment and torque of the floor slab. It is the design basis for the bending moment reinforcement of the thick slab section. The width of the rectangular beam is equal to the width of the slab strip, and the height is equal to the thickness of the slab. The stirrups of the rectangular beam can be tie bars.

[0044] Example 2

[0045] The Wood-Hammer rule states that if the torque per unit width of the strip in the finite element analysis is... mxx , m yy and m xy The bending moment value is expressed algebraically, and the reinforcement of the floor slab should be respectively along... x Xianghe y To be configured to resist circumvention y Xianghe x Ultimate bending moment per unit width M x and M y The details are as follows:

[0046] For bottom reinforcement, it should generally be calculated using the following formula:

[0047]

[0048]

[0049] If the calculation yields ,or Then it should be calculated according to the following formula:

[0050] if ,make ,but

[0051] if ,make ,but

[0052] If it still exists or If so, it means that the bottom of the slab in the corresponding direction does not need to be reinforced with bending steel bars as calculated.

[0053] For the top reinforcement, it should generally be calculated using the following formula:

[0054]

[0055]

[0056] If the calculation yields or Then it should be calculated according to the following formula:

[0057] if ,make ,but

[0058] if ,make ,but

[0059] If it still exists or If so, it means that the top of the slab in the corresponding direction does not need to be reinforced with bending steel bars as calculated.

[0060] Example 3

[0061] The deformation, bending, shear, and punching shear resistance of the transfer slab were verified using three-dimensional shell element calculation software capable of considering transverse shear deformation. Under quasi-permanent load combinations, the maximum vertical deformation of the transfer slab should deduct the influence of support deformation, and the relative deformation calculated based on the longer span should not exceed 1 / 800. The reinforcement ratio of the longitudinal reinforcement for bending of the transfer slab should not exceed 1.0%. The maximum principal shear stress obtained from finite element stress analysis should not exceed 0.25. ( (This refers to the design value of the axial compressive strength of concrete). When the shear span ratio of the calculated section is greater than 2.5, punching shear verification of the column or shear wall on the transfer slab should be performed, and the average shear stress of the calculated section should not exceed 1.2. ( (Design value of axial tensile strength of concrete); Based on the finite element analysis results, the slab is divided into column strip, column edge strip and mid-span strip; the strip bending moment calculation adopts the calculation method that comprehensively considers the combined effect of bidirectional bending moment and torque of the floor slab; according to the strip internal force calculation results, the bending and shear reinforcement of the section is calculated and the reinforcement diagram is drawn, and the reinforcement structure is checked;

[0062] This method for designing transfer slabs fully considers the stress characteristics of concrete under multi-directional stress, resulting in a rational design. In terms of flexural design, it comprehensively considers the combined effects of bidirectional bending moment and torque on the floor slab, making the slab strip design safer than conventional methods. For shear and punching shear design, it incorporates the influence of the shear span ratio, providing a clearer mechanical concept than conventional methods and effectively reducing the thickness of the transfer slab. The introduction of column-edge slab strips in slab strip division, along with precise requirements for mid-span slab strip division, makes it safer and more economical than conventional designs.

[0063] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for designing thick plates, characterized in that, include: S1: Estimation of the thickness of the transfer slab. The cross-sectional height of the thicker transfer slab is taken as 0.2 to 0.3 times the clear span of the shorter side of the floor slab. S2: Using an elastic design method, the internal forces and deformation distribution of the transfer plate are calculated and analyzed through a three-dimensional spatial model; S3: Check the allowable vertical deformation of the transfer plate and the suitability of its bending, shear, and punching shear sections; S4: After the plate thickness is determined, the plate strips are divided according to the finite element analysis results for design. The plate strips are divided into column mid-span plate strips, column edge plate strips and mid-span plate strips according to their relative positional relationship with the column support. The internal forces of the plate strips are calculated separately. S5: Substitute the slab strips, etc., into rectangular beams for reinforcement calculation; S6: Draw the reinforcement diagram for the transfer slab and check the structural requirements; The allowable value of vertical deformation of the conversion plate shall not exceed 1 / 800 of the calculated span of the long side of the floor slab, and the deformation calculation shall deduct the influence of the support compression deformation. The calculation span is l0, and its calculation value is l. n +min(0.5S) w 0.5h s ), where S w h is the width of the support column or wall. s The thickness of the conversion plate; The reinforcement ratio ρ of the longitudinal bending reinforcement was used when estimating the thickness of the transfer slab. s For the thickness estimation of the conversion plate, if the calculated section shear span ratio λ is less than 2.5, a section shear resistance check is performed; if the calculated section shear span ratio λ is greater than 2.5, a section punching shear resistance check is performed. When calculating the internal forces of the slab strip in S4, the combined effect of the bidirectional bending moment and torque of the floor slab is comprehensively calculated. The column center strip refers to a strip-shaped area with the same width as the column cross-section along the column centerline; the column side strip refers to a strip-shaped area distributed on one side of the side column and on both sides of the central column; and the mid-span strip is a strip-shaped area located between the column side strips. The width of the rectangular beam is equal to the width of the slab, and the height is equal to the thickness of the slab. The upper part of the conversion plate is the superstructure, and the lower part of the conversion plate is the conversion column, which is arranged at intervals below the conversion plate.

2. The method for designing a thick plate according to claim 1, characterized in that, The span-to-thickness ratio of the conversion plate is no greater than 5, and the span-to-thickness ratio is the ratio of the net span of the short side of the floor slab to the thickness of the floor slab.

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