Prediction method and system for axial compression stability bearing capacity of truss columns considering initial stress and creep effects

Abstract

Prediction method and system for axial compression stability bearing capacity of truss columns considering initial stress and creep effects, belonging to the technical field of truss hybrid structures, solve the problem of low accuracy in predicting the axial compression stability bearing capacity of truss columns due to the lack of consideration of initial stress and creep effects. The method of the present invention includes steps such as determining basic parameters, considering the influence of shear deformation of truss columns on initial stress, considering the influence of shear deformation of truss columns on creep, calculating the stability coefficient, and calculating the stability bearing capacity of truss columns. Starting from the mechanical principle, this model establishes an equilibrium differential equation, conducts mathematical calculations and derivations using the stability theory, comprehensively considers the influence of shear deformation, initial stress, and creep on the axial compression stability bearing capacity of truss columns, and proposes a prediction method for the stability bearing capacity of truss columns. The present invention is applicable to predicting the axial compression stability bearing capacity affected by initial stress and creep of truss columns.

Description

Technical Field

[0001] The truss column has many advantages such as high bearing capacity and excellent overall performance, and is widely used in the main structures of major infrastructure, such as super high-rise buildings, the tail of cement kilns, columns of heavy industrial factories, etc. At the same time, with the development of engineering construction and the in-depth theoretical research, the truss column will also be widely used in structures such as large cantilever structures and offshore platforms.

[0002] In actual engineering, the initial stress of the truss column will have a great influence on the mechanical properties and ultimate bearing capacity of the truss column. For a single concrete-filled steel tube column with an initial stress load ratio greater than 0.6, the decrease in the ultimate bearing capacity due to the initial stress exceeds 20%. Due to the influence of shear deformation of the truss column, the reduction effect of the initial stress on the bearing capacity of the member is more obvious. Therefore, it is necessary to consider the influence of the initial stress on the truss column with shear deformation, so as to accurately predict the stable bearing capacity of the member to ensure the structural safety and building use function.

[0003] During the service process of the truss column, the long-term load will have a great influence on the mechanical properties of the truss column. Due to the aging effect of the core concrete, creep occurs in the concrete-filled steel tube. When considering the long-term load alone, the ultimate bearing capacity of the long column in the concrete-filled steel tube decreases by 13.1%. Since the truss column needs to consider shear deformation, the influence of creep on the ultimate bearing capacity of the truss column with shear deformation is unknown, so it is urgent to propose a method for predicting the stable bearing capacity of the truss column with shear deformation considering concrete creep.

[0004] Essentially, due to the initial stress of the steel tube during the construction process of the truss column, the elastic stage of the member steel tube is shortened and it enters the elastoplastic stage in advance, and the confinement effect appears later. Coupled with the amplification of this effect by shear deformation, the ultimate bearing capacity of the member is reduced. The long-term deformation of the core concrete increases during the load-bearing stage, and the internal force is redistributed. Coupled with the influence of shear deformation, the ultimate bearing capacity of the member is reduced. Therefore, it is urgent to form a method for predicting the axial compression stable bearing capacity of the truss column considering the influence of initial stress and creep. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem of low prediction accuracy of the existing method for predicting the axial compression stable bearing capacity of the truss column due to the lack of consideration of the influence of initial stress and creep, and to provide a method and system for predicting the axial compression stable bearing capacity of the truss column considering the influence of initial stress and creep.

[0006] The present invention is realized through the following technical solutions. On the one hand, the present invention provides a method for predicting the axial compression stable bearing capacity of the truss column considering the influence of initial stress and creep, and the method includes:

[0007] Step 1: Determine the basic parameters affecting the stable bearing capacity of the truss column throughout its life cycle;

[0008] Step 2: According to the reduction effect of the shear deformation of the truss column on the Euler critical force, calculate the ratio of the deflection considering the influence of the initial stress due to shear deformation to the initial deflection with moment amplification, which is denoted as the initial stress influence amplification coefficient;

[0009] Step 3: According to the amplification effect of the shear deformation of the truss column on the slenderness ratio of the limb column, obtain the equivalent slenderness ratio of the truss column, and calculate the ratio of the deflection considering the influence of shear deformation and creep to the initial deflection with moment amplification, which is denoted as the creep influence amplification coefficient;

[0010] Step 4: Utilize the initial stress influence amplification coefficient and the creep influence amplification coefficient to obtain the stability coefficient of the truss column considering the initial stress and creep;

[0011] Step 5: Utilize the stability coefficient of the truss column considering the initial stress and creep to obtain the axial compression stability bearing capacity of the truss column.

[0012] Furthermore, in Step 1, the basic parameters include the initial stress ratio, slenderness ratio, steel ratio, steel strength grade, long-term load grade, concrete strength grade, line stiffness ratio of a single limb to the entire cross-section, line stiffness ratio of a single limb to the web member, and geometric slenderness ratio.

[0013] Furthermore, in Step 2, the calculation formula for the initial stress influence amplification coefficient is:

[0014]

[0015] In the formula, is the initial stress influence amplification coefficient of the truss column, which is the amplification of the initial deflection under the influence of shear deformation and initial stress; δ′ is the deflection of the truss column considering the amplification coefficient of shear initial stress influence; δ is the initial deflection after moment amplification; N y is the construction load borne by the steel pipe of the truss column during the construction stage; is the Euler critical force of the truss column; is the Euler critical force of the steel pipe of the truss column; N cr is the Euler critical force of a single column limb; N y,cr is the Euler critical force of the steel pipe column; is the unit shear angle of the truss column; is the unit shear angle of the empty steel pipe truss column.

[0016] Furthermore, in Step 3, the calculation formula for the creep influence amplification coefficient is:

[0017]

[0018] In the formula, ξ * is the creep influence amplification coefficient of the truss column, which is the amplification of the initial deflection under the influence of shear deformation and creep; is the equivalent slenderness ratio of the truss column; n L is the axial compression ratio of the component; β α is the steel ratio coefficient of the component; is the creep coefficient of the component concrete; E s is the elastic modulus of the steel; E c is the elastic modulus of the concrete; α is the steel ratio; λ sc is the slenderness ratio of the limb column; N E is the Euler critical force of the truss column section; is the unit shear angle of the truss column.

[0019] Furthermore, in step 4, the calculation formula for the stability coefficient of the truss column considering initial stress and creep is:

[0020]

[0021] In the formula, is the stability coefficient of the truss column considering initial stress and creep; is the amplification coefficient of the influence of the initial stress of the truss column; ξ * is the amplification coefficient of the influence of the creep of the truss column; is the equivalent slenderness ratio of the truss column; K is the initial defect coefficient of the component.

[0022] Furthermore, in step 5, the calculation formula for the axial compression stability bearing capacity of the truss column is:

[0023]

[0024] In the formula, N u is the stability bearing capacity of the truss column; is the stability coefficient of the truss column considering initial stress and creep; N0 is the bearing capacity of the truss column under axial compression section; A sci is the cross-sectional area of each column limb; f sc is the design value of the compressive strength of concrete-filled steel tube; n is the number of column limbs of the component.

[0025] Furthermore, the types of the truss column include but are not limited to concrete-filled steel tube truss column or FRP-wrapped truss column;

[0026] The column limbs of the truss column include but are not limited to rectangular concrete-filled steel tube, special-shaped concrete-filled steel tube or empty steel tube;

[0027] The web members of the truss column include but are not limited to angle steel, section steel, steel plate, steel bar or empty steel tube.

[0028] In the second aspect, the present invention provides a prediction system for the axial compression stability bearing capacity of a truss column considering the influence of initial stress and creep, and the system includes:

[0029] A basic parameter determination module for determining the basic parameters that affect the stable bearing capacity of a truss column throughout its service life;

[0030] An initial stress influence amplification factor calculation module for calculating, based on the reduction effect of the shear deformation of the truss column on the Euler critical force, the ratio of the deflection and the magnified initial deflection of the bending moment considering the influence of the initial stress under shear deformation, denoted as the initial stress influence amplification factor;

[0031] A creep influence amplification factor calculation module for obtaining the equivalent slenderness ratio of the truss column based on the amplification effect of the shear deformation of the truss column on the slenderness ratio of the limb column, and calculating the ratio of the deflection and the magnified initial deflection of the bending moment under the influence of shear deformation and creep, denoted as the creep influence amplification factor;

[0032] A stability coefficient acquisition module for obtaining the stability coefficient of the truss column considering the initial stress and creep by using the initial stress influence amplification factor and the creep influence amplification factor;

[0033] A truss column axial compression stable bearing capacity acquisition module for obtaining the truss column axial compression stable bearing capacity by using the stability coefficient of the truss column considering the initial stress and creep.

[0034] In a third aspect, the present invention provides a computer device, including a memory and a processor. A computer program is stored in the memory. When the processor runs the computer program stored in the memory, it executes the steps of the method for predicting the axial compression stable bearing capacity of a truss column considering the influence of initial stress and creep as described above.

[0035] In a fourth aspect, the present invention provides a computer-readable storage medium. Multiple computer instructions are stored in the computer-readable storage medium. The multiple computer instructions are used to cause a computer to execute the method for predicting the axial compression stable bearing capacity of a truss column considering the influence of initial stress and creep as described above.

[0036] Advantages of the present invention:

[0037] The present invention provides a method for predicting the axial compression stable bearing capacity of a truss column considering the influence of initial stress and creep, which is a calculation method for the axial compression stable bearing capacity of a truss column considering the influence of shear deformation on initial stress and creep based on mechanical principles and stability theory. Specifically, on the basis of fully considering the basic parameters that affect the bearing capacity of a truss column throughout its service life, in terms of the influence of initial stress, a calculation method for the initial stress influence amplification factor of a truss column is proposed; in terms of the influence of creep, a calculation method for the creep influence amplification factor of a truss column is proposed; by using the stability theory, a calculation method for the stability coefficient is obtained from the Perry formula, and then the axial compression stable bearing capacity of the truss column is calculated.

[0038] Compared with the prior art, the present invention proposes a method for predicting the stable bearing capacity of a truss column considering the initial stress and creep by taking into account the influence of shear deformation on the initial stress and creep. In the model, the Euler critical force and slenderness ratio under the influence of shear deformation are corrected to obtain the amplification coefficients of the initial stress and creep of the truss column. From the static equilibrium equation, the equilibrium differential equation is solved to obtain the stability coefficient considering the initial stress and creep under the influence of shear deformation, and then the stable bearing capacity of the truss column is solved. By establishing a mechanical model, applying the stability theory, and performing mathematical operations, the formula for the stable bearing capacity of the truss column is derived more rigorously, and a method for predicting the axial compression stable bearing capacity of the truss column considering the initial stress and creep is proposed. Generally speaking, the prediction method has the following advantages:

[0039] (1) The previous models did not consider the influence of shear deformation on the initial stress. Starting from the basic mechanical principles, the present invention analyzes the shear deformation of the truss column and, combined with the existing research experience, proposes an amplification coefficient for the influence of the initial stress.

[0040] (2) The previous models did not consider the influence of shear deformation on creep. Through the research and analysis of the shear deformation of the truss column, the present invention proposes an amplification coefficient for the influence of creep. Thus, a method for predicting the axial compression stable bearing capacity of the truss column considering the initial stress and creep is proposed more scientifically, and the axial compression stable bearing capacity of the truss column under the influence of the initial stress and creep can be accurately predicted.

[0041] Different from a single-column considering the initial stress and creep, a truss column needs to consider the influence of shear deformation on the initial stress and creep. The prediction model solves the complex problem that it is not easy to consider shear deformation in the influence of creep and initial stress. The model can accurately predict the axial compression stable bearing capacity of the truss column affected by the initial stress and creep, and at the same time shows broad applicability and wide application.

[0042] (3) The method steps of the present invention are simple, the design is reasonable and the concept is clear, solving the complex problem that it is not easy to consider shear deformation in the initial stress and creep at present, and at the same time facilitating the calculation and analysis of designers.

[0043] (4) The truss column described in the model includes but is not limited to a concrete-filled steel tube truss column, and is also applicable to truss columns made of other materials. It has good applicability to concrete-filled steel tube truss columns made of ultra-high performance concrete UHPC, and truss columns wrapped with FRP, etc. The model is also applicable to various truss column forms where the column limbs are rectangular concrete-filled steel tubes, special-shaped concrete-filled steel tubes, empty steel tubes, and the web members are angle steels, section steels, steel plates, steel bars, empty steel tubes, etc. The model shows broad applicability and broad development potential.

[0044] The present invention is applicable to predicting the axial compression stability bearing capacity affected by the initial stress and creep of truss columns. Compared with the traditional single-limb concrete-filled steel tube considering the influence of initial stress and creep, the stability bearing capacity prediction method of the present invention needs to consider the influence of shear deformation on the initial stress and creep for truss columns, which will provide a calculation basis for truss columns under the influence of initial stress and creep, and further promote the academic research and engineering application of steel-concrete composite columns. Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0046] Figure 1 It is a calculation flow chart of the prediction method for the axial compression stability bearing capacity of a truss column considering the influence of initial stress and creep according to the present invention;

[0047] Figure 2 It is a schematic diagram of the elevation and section of a truss column according to an embodiment of the present invention;

[0048] Figure 3 It is a schematic diagram of a typical load-displacement curve of a truss column considering the influence of initial stress and creep according to an embodiment of the present invention;

[0049] Figure 4 It is a front view and sectional view of a test-verified truss column for the prediction method of the axial compression stability bearing capacity of a truss column considering the influence of initial stress and creep according to an embodiment of the present invention;

[0050] Figure 5 It is a comparison diagram of the test measured results and the model prediction results of the prediction method for the axial compression stability bearing capacity of a truss column considering the influence of initial stress and creep according to the present invention.

[0051] In the figure, 1 - steel tube of column limb; 2 - web member; 3 - concrete of column limb; 4 - end plate. Specific Embodiments

[0052] The following details the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0053] Embodiment 1. A prediction method for the axial compression stability bearing capacity of a truss column considering the influence of initial stress and creep, the method includes:

[0054] Step 1: Determine the basic parameters affecting the stability bearing capacity of the truss column throughout its life;

[0055] Step 2: According to the reduction effect of the shear deformation of the truss column on the Euler critical force, calculate the ratio of the deflection considering the influence of the initial stress due to shear deformation to the initial deflection with magnification of the bending moment, denoted as the magnification coefficient of the initial stress influence;

[0056] Step 3: According to the magnification effect of the shear deformation of the truss column on the slenderness ratio of the limb column, obtain the equivalent slenderness ratio of the truss column, and calculate the ratio of the deflection considering the influence of shear deformation and creep to the initial deflection with magnification of the bending moment, denoted as the magnification coefficient of creep influence;

[0057] Step 4: Utilize the magnification coefficient of the initial stress influence and the magnification coefficient of creep influence to obtain the stability coefficient of the truss column considering the initial stress and creep;

[0058] Step 5: Utilize the stability coefficient of the truss column considering the initial stress and creep to obtain the axial compression stability bearing capacity of the truss column.

[0059] This embodiment considers the influence of the shear deformation existing in the truss column and is used to calculate and analyze the stability bearing capacity of the truss column under the influence of the initial stress and creep. Starting from the mechanical principle, by applying the stability theory and mathematical derivation, the influence of the shear deformation of the truss column on the initial stress and creep is comprehensively considered, and a prediction method for the stability bearing capacity of the truss column under the influence of the initial stress and creep is proposed.

[0060] This embodiment fully considers the influence of the shear deformation that must be considered in the calculation of the stability bearing capacity of the truss column with initial stress and creep. It is necessary to conduct complex formula derivation based on the mechanical principle and relevant theories, consider the magnification effect of the shear deformation on the initial stress and creep, and respectively propose the magnification coefficients of the initial stress and creep considering the influence of the shear deformation. Therefore, it is of great technical difficulty to predict the stability bearing capacity of the truss column with initial stress and creep. This prediction method solves the complex problem that it is not easy to consider the shear deformation in the initial stress and creep at present, and thus innovatively proposes a prediction method for the stability bearing capacity of the truss column under the influence of the initial stress and creep.

[0061] Embodiment 2: This embodiment further limits the prediction method for the axial compression stability bearing capacity of the truss column considering the influence of the initial stress and creep as described above. In this embodiment, the basic parameters in Step 1 are further limited, specifically including:

[0062] In Step 1, the basic parameters include the initial stress ratio, slenderness ratio, steel ratio, steel strength grade, long-term load grade, concrete strength grade, the ratio of the linear stiffness of a single limb to the entire cross-section, the ratio of the linear stiffness of a single limb to the web member, and the geometric slenderness ratio.

[0063] In this embodiment, the linear stiffness ratio of a single limb and the entire cross-section, and the linear stiffness ratio of a single limb and a web member are used as the basic parameters affecting the stable bearing capacity of the truss column during its entire service life. The unit shear angle of the truss column and that of the hollow steel pipe truss column can be calculated more simply and conveniently, avoiding complex formula calculations. At the same time, it is convenient for controlling the parameter range and comparative analysis.

[0064] Embodiment 3: This embodiment further limits the prediction method for the axial compression stable bearing capacity of the truss column considering the influence of initial stress and creep as described above. In this embodiment, the amplification coefficient of the influence of the initial stress in step 2 is further limited, specifically including:

[0065] In step 2, the calculation formula for the amplification coefficient of the influence of the initial stress is:

[0066]

[0067] In the formula, is the amplification coefficient of the influence of the initial stress of the truss column, which is the amplification of the initial deflection under the influence of shear deformation and initial stress; δ′ is the deflection of the truss column considering the amplification coefficient of the influence of shear initial stress; δ is the initial deflection after moment amplification; N y is the construction load borne by the steel pipe of the truss column during the construction stage; is the Euler critical force of the truss column; is the Euler critical force of the steel pipe of the truss column; N cr is the Euler critical force of a single column limb; N y,cr is the Euler critical force of the steel pipe column; is the unit shear angle of the truss column; is the unit shear angle of the hollow steel pipe truss column.

[0068] The calculation method of the amplification coefficient of the influence of the initial stress in this embodiment proposes the initial stress amplification considering the influence of shear deformation on the initial stress of the truss column, that is, considering the influence of the shear deformation existing in the truss column, and the influence of the initial stress of the truss column can be calculated and analyzed. This calculation method calculates and analyzes the initial stress amplification under the influence of shear deformation by considering the influence of the shear deformation existing in the truss column on the initial stress. This embodiment can solve the problem that it is difficult to calculate the stable bearing capacity of the truss column with initial stress, and can calculate and predict the stable bearing capacity of the truss column with initial stress more accurately, providing technical theoretical support for actual engineering design and calculation.

[0069] Embodiment 4: This embodiment further limits the prediction method for the axial compression stable bearing capacity of the truss column considering the influence of initial stress and creep as described above. In this embodiment, the amplification coefficient of the influence of creep in step 3 is further limited, specifically including:

[0070] In Step 3, the calculation formula for the creep influence amplification factor is as follows:

[0071]

[0072] In the formula, ξ * is the creep influence amplification factor of the truss column, which is the amplification of the initial deflection under shear deformation and creep influence; is the equivalent slenderness ratio of the truss column; n L is the axial compression ratio of the member; β α is the steel ratio coefficient of the member; is the creep coefficient of the member's concrete; E s is the elastic modulus of the steel; E c is the elastic modulus of the concrete; α is the steel ratio; λ sc is the slenderness ratio of the limb column; N E is the Euler critical force of the truss column section; is the unit shear angle of the truss column.

[0073] The calculation method of the creep influence amplification factor in this embodiment proposes the creep amplification considering the influence of shear deformation on creep for the truss column, takes into account the influence of shear deformation existing in the truss column, can calculate and analyze the creep influence of the truss column, and calculates and analyzes the creep amplification under the influence of shear deformation by considering the influence of shear deformation existing in the truss column on creep. This embodiment can solve the problem that it is not easy to calculate the stable bearing capacity of the truss column with creep, can calculate and predict the stable bearing capacity of the truss column with creep more accurately, and provides technical theoretical support for the actual engineering design and calculation.

[0074] Embodiment 5 is a further limitation on the prediction method for the axial compression stability bearing capacity of the truss column considering initial stress and creep as described above. In this embodiment, for Step 4, the stability coefficient of the truss column considering initial stress and creep is further limited, specifically including:

[0075] In Step 4, the calculation formula for the stability coefficient of the truss column considering initial stress and creep is as follows:

[0076]

[0077] In the formula, is the stability coefficient of the truss column considering initial stress and creep; is the initial stress influence amplification factor of the truss column; ξ * is the creep influence amplification factor of the truss column; is the equivalent slenderness ratio of the truss column; K is the initial defect coefficient of the member.

[0078] The calculation method of this embodiment can have a wider application space. These two calculation methods are applicable to various cross-sectional forms of concrete-filled steel tubular columns, including rectangular, polygonal, etc.; in the process of formula derivation, based on the Perry formula, it is relatively easy to consider the initial stress and creep of the truss column in the formula, and no complex cross terms will be generated during the formula derivation process. The derivation result is concise and easy for engineering design calculation; when calculating the stability bearing capacity of the truss column with initial stress and creep, the calculation result is reliable and has a high accuracy, and it can relatively accurately predict the stability bearing capacity of the truss column under the influence of initial stress and creep.

[0079] Embodiment 6. This embodiment further limits the prediction method for the axial compression stability bearing capacity of the truss column considering the influence of initial stress and creep as described above. In this embodiment, for step 5, the axial compression stability bearing capacity of the truss column is further limited, specifically including:

[0080] In step 5, the calculation formula for the axial compression stability bearing capacity of the truss column is:

[0081]

[0082] In the formula, N u is the stability bearing capacity of the truss column; is the stability coefficient of the truss column considering initial stress and creep; N0 is the bearing capacity of the cross-section of the truss column under axial compression; A sci is the cross-sectional area of each column limb; f sc is the design value of the compressive strength of concrete-filled steel tube; n is the number of column limbs of the member.

[0083] The calculation method of this embodiment can have a wider application space. These two calculation methods are applicable to various cross-sectional forms of concrete-filled steel tubular columns, including rectangular, polygonal, etc.; in the process of formula derivation, based on the Perry formula, it is relatively easy to consider the initial stress and creep of the truss column in the formula, and no complex cross terms will be generated during the formula derivation process. The derivation result is concise and easy for engineering design calculation; when calculating the stability bearing capacity of the truss column with initial stress and creep, the calculation result is reliable and has a high accuracy, and it can relatively accurately predict the stability bearing capacity of the truss column under the influence of initial stress and creep.

[0084] Embodiment 7. This embodiment further limits the prediction method for the axial compression stability bearing capacity of the truss column considering the influence of initial stress and creep as described above. In this embodiment, the types of the truss columns are further limited, specifically including:

[0085] The types of the truss columns include, but are not limited to, concrete-filled steel tubular truss columns or truss columns wrapped with FRP;

[0086] The column members of the truss column include, but are not limited to, rectangular concrete-filled steel tubes, special-shaped concrete-filled steel tubes, or hollow steel tubes;

[0087] The web members of the truss column include, but are not limited to, angle steels, section steels, steel plates, steel bars, or hollow steel tubes.

[0088] This embodiment provides the applicable scope of the prediction method of the present application. For all types of truss columns within this applicable scope, the axial compression stability bearing capacity of the truss column can be accurately predicted through the above-mentioned method.

[0089] Embodiment 8. This embodiment is an example 1 of the prediction method for the axial compression stability bearing capacity of a truss column considering the influence of initial stress and creep, and specifically includes:

[0090] Taking Figure 2 two types of truss columns with flat web members and diagonal web members as shown as an example, the steel tube column member 1 and the column member concrete 3 are combined into a concrete-filled steel tube column member. The internal column member concrete 3 plays a supporting role, and the external steel tube column member 1 plays a constraining role, and deforms in coordination with the web member 2 and the end plate 4 to bear the load. Both ends of the web member 2 are welded to the column member steel tube 1. The column member steel tube 1 is filled with concrete to form the column member concrete 3. The radius of the column member concrete 3 is equal to the inner radius of the steel tube column member 1. Both ends of the column member steel tube are fully welded to the end plate 4 to form a relatively typical truss column.

[0091] A prediction method for the axial compression stability bearing capacity of a truss column considering the influence of initial stress and creep specifically includes the following steps:

[0092] (1) According to the calculation process as Figure 1 shown, determine the basic parameters affecting the full-life stability bearing capacity of the truss column: initial stress ratio, slenderness ratio, steel ratio, steel strength grade; long-term load grade, concrete strength grade; ratio of the linear stiffness of a single limb to the entire cross-section, ratio of the linear stiffness of a single limb to the web member, geometric slenderness ratio;

[0093] (2) Consider the influence of the shear deformation of the truss column on the initial stress: Consider the reduction of the Euler critical force due to the shear deformation of the truss column, calculate the ratio of the deflection considering the influence of the shear deformation on the initial stress to the initial deflection with the moment amplification, that is, the initial stress influence amplification coefficient, and calculate the initial stress amplification coefficient to consider the influence of the shear deformation of the truss column on the initial stress;

[0094] In this step, consider that when the construction load N y acts on the column member steel tube, as Figure 3 shown, due to the amplification effect of the shear deformation of the truss column on the initial stress, the vertical displacement y2 of the truss column is behind y1. The AB section is the influence of the initial stress on the truss column. The steel tube will enter the elastic stage earlier than the truss column without the influence of the initial stress.

[0095] (3) Consider the influence of the shear deformation of the truss column on creep: Considering the amplification effect of the shear deformation of the truss column on the slenderness ratio of the limb column, the equivalent slenderness ratio of the truss column is obtained, and the ratio of the deflection and the magnified initial deflection of the bending moment under the influence of shear deformation and creep is calculated, that is, the creep influence amplification coefficient, and the creep influence amplification coefficient is calculated to consider the influence of the shear deformation of the truss column on creep;

[0096] This step considers the influence of aging effect, such as Figure 3 shown, the long-term load N L acts on both ends of the truss column, the bearing capacity of the truss column basically does not change, and the vertical displacement develops from y3 to y4. The BC section is the change of the load gradually increasing from the construction load to the long-term load, and the CD section is the change of the long-term load holding and loading.

[0097] (4) Calculate the stability coefficient of the truss column considering initial stress and creep: According to the mechanical principle, list the equilibrium differential equation, solve the equilibrium differential equation, and adopt the edge yield criterion to calculate the stability coefficient of the truss column considering initial stress and creep derived from the Perry formula;

[0098] (5) Calculate the stable bearing capacity of the truss column: Calculate the stable bearing capacity of the truss column according to the stable bearing capacity calculation formula of the truss column; The model predicts the ultimate load N u of the truss column. By using the above steps, the axial compression stable bearing capacity of the truss column considering initial stress and creep can be predicted conveniently and accurately.

[0099] Furthermore, the truss column described in step (1) includes but is not limited to the concrete-filled steel tube truss column, and is also applicable to truss columns made of other materials, including the concrete-filled steel tube truss column made of ultra-high performance concrete UHPC, and the truss column wrapped with FRP, etc. It is also applicable to various truss column forms where the column limbs are rectangular concrete-filled steel tubes, special-shaped concrete-filled steel tubes, hollow steel tubes, and the web members are angle steels, section steels, steel plates, steel bars, hollow steel tubes, etc.

[0100] Furthermore, in step (2), the reduction effect of shear deformation on the Euler critical force N cr of a single column limb and the Euler critical force N y,cr of the steel pipe column is considered respectively, and the Euler critical force of the truss column and the Euler critical force of the steel pipe of the truss column are obtained respectively to consider the influence of the shear deformation of the truss column on the initial stress, and the ratio of the deflection of the truss column considering the influence of the initial stress to the initial deflection after the bending moment is magnified is used to measure the amplification effect of the initial stress on the deflection of the truss column, and is calculated according to the formula

[0101]

[0102] ;

[0103] In the formula, is the amplification coefficient of the initial stress of the truss column, which is the amplification of the initial deflection under shear deformation and initial stress; δ′ is the deflection (mm) of the truss column considering shear deformation and initial stress; δ is the initial deflection (mm) after moment amplification; N y is the construction load (N) borne by the steel pipe of the truss column during the construction stage; is the Euler critical force (N) of the truss column; is the Euler critical force (N) of the steel pipe of the truss column; N cr is the Euler critical force (N) of a single column limb; N y,cr is the Euler critical force (N) of the steel pipe column; is the unit shear angle of the truss column; is the unit shear angle of the empty steel pipe truss column.

[0104] Furthermore, in step (3), the shear deformation of the truss column is considered in the equivalent slenderness ratio of the truss column. By multiplying the slenderness ratio λ sc of the column limb by the amplification coefficient of shear deformation, the influence of shear deformation on the creep of the truss column is considered. Through mechanical analysis and calculation, the deflections under the influence of shear deformation and creep and the initial deflection after moment amplification are obtained respectively. The ratio of the two is the amplification of the initial deflection by the creep of the truss column. Calculate according to the formula

[0105]

[0106] ;

[0107] In the formula, ξ * is the amplification coefficient of the creep influence of the truss column, which is the amplification of the initial deflection under shear deformation and creep influence; is the equivalent slenderness ratio of the truss column; n L is the axial compression ratio of the member; β α is the steel content coefficient of the member; is the creep coefficient of the member's concrete; E s is the elastic modulus of the steel; E c is the elastic modulus of the concrete; α is the steel content; λ sc is the slenderness ratio of the column limb; N E is the Euler critical force (N) of the cross-section of the truss column; is the unit shear angle of the truss column.

[0108] Furthermore, in step (4), the additional deflection caused by the initial stress, creep, and shear deformation is superimposed with the deflection caused by the bending deformation to obtain the actual deflection y. The equilibrium differential equation for the actual deflection y is listed, and the sine half-wave function of the actual deflection y is obtained after solving the equilibrium differential equation. Using the edge yield criterion, the stability coefficient of the truss column considering the initial stress and creep is obtained from the Perry formula, and the calculation is carried out according to the formula

[0109] ;

[0110] In the formula, is the stability coefficient of the truss column considering the initial stress and creep; is the amplification coefficient of the influence of the initial stress of the truss column; ξ * is the amplification coefficient of the influence of creep of the truss column; is the equivalent slenderness ratio of the truss column; K is the initial defect coefficient of the component, usually taken as 0.25.

[0111] Furthermore, in step (5), the calculation formula for the axial compression stability bearing capacity of the truss column in the "Code for Design of Concrete-Filled Steel Tubular Structures" GB50936-2014 is followed, and the calculation is carried out according to the formula

[0112]

[0113]

[0114] ;

[0115] In the formula, N u is the stability bearing capacity of the truss column (N); is the stability coefficient of the truss column considering the initial stress and creep; N0 is the bearing capacity of the axially compressed cross-section of the truss column (N); A sci is the cross-sectional area of each column limb (mm 2 ); f sc is the design value of the compressive strength of concrete-filled steel tube (MPa); n is the number of column limbs of the component.

[0116] Embodiment 9. This embodiment is an embodiment 2 of the prediction method for the axial compression stability bearing capacity of a truss column considering the influence of initial stress and creep as described above, and specifically includes:

[0117] A truss column specimen, as Figure 4 shown, with an initial stress ratio β = 0.57. The specimen has a square cross-section with a length and width of 0.4 m, a column limb height of 2.4 m, 6 internodes, and a calculated length of 0.38 m for each internode. There are 60-mm extended sections at both ends. The column limbs are made of φ80×3.0 steel pipes filled with C40 concrete. The average measured 28-day cube compressive strength of the concrete is 38.2 MPa, and the elastic modulus is 3.21×10 4MPa. The horizontal and diagonal braces are made of φ48×2.0 hollow steel pipes. At both ends of the specimen, end plates with a length and width of 600 mm and a thickness of 35 mm are welded. The specimen structure is as Figure 4 shown. The steel used for the specimen is Q235 steel, and the measured elastic modulus of the steel is 2.00×10 5 MPa, and the yield strength and tensile strength are 300 MPa and 450 MPa respectively.

[0118] Using the prediction method for the axial compression stability bearing capacity of truss columns considering the initial stress and creep effects, the basic parameters affecting the full-life stability bearing capacity of truss columns measured by experiments are used for calculation. The calculation process is as follows:

[0119] (1) Determine the basic parameters affecting the full-life stability bearing capacity of truss columns: the initial stress ratio is 0.57, the slenderness ratio λ sc of the column limb is 14.885, the steel ratio α is 0.169, the measured yield strength and tensile strength of the steel are 300 MPa and 450 MPa respectively; the average value of the measured 28-day cube compressive strength of C40 concrete is 38.2 MPa.

[0120] (2) Consider the influence of the shear deformation of the truss column on the initial stress: Considering the reduction of the Euler critical force caused by the shear deformation of the truss column, calculate the ratio of the deflection considering the influence of the initial stress under the shear deformation and the initial deflection amplified by the bending moment, that is, the initial stress influence amplification coefficient, and calculate the initial stress amplification coefficient to consider the influence of the shear deformation of the truss column on the initial stress:

[0121]

[0122] (3) Consider the influence of the shear deformation of the truss column on creep: Considering the amplification effect of the shear deformation of the truss column on the slenderness ratio of the limb column, obtain the equivalent slenderness ratio of the truss column, and calculate the ratio of the deflection considering the influence of the shear deformation and creep and the initial deflection amplified by the bending moment, that is, the creep influence amplification coefficient, and calculate the creep influence amplification coefficient to consider the influence of the shear deformation of the truss column on creep;

[0123]

[0124] (4) Calculate the stability coefficient of the truss column considering the initial stress and creep: According to the mechanical principle, list the equilibrium differential equation, solve the equilibrium differential equation, and adopt the edge yield criterion, which is derived from the Perry formula

[0125] Calculation of the stability coefficient of the truss column considering the initial stress and creep:

[0126]

[0127] (5) Calculation of the stable bearing capacity of the truss column: Calculate the stable bearing capacity of the truss column according to the formula for calculating the stable bearing capacity of the truss column;

[0128]

[0129] The axial compression stable bearing capacity of the truss column considering the initial stress and creep effects calculated by the prediction method of the present invention is compared with the test measured results as Figure 5 shown. The results show that the results of the prediction method for the axial compression stable bearing capacity of the truss column considering the initial stress and creep effects of the present invention are relatively accurate.

[0130] Starting from the mechanical principle, the present invention establishes a balance differential equation, solves the balance differential equation, conducts mathematical calculations and inferences using the stability theory, and establishes a prediction method for the axial compression stable bearing capacity of the truss column considering the initial stress and creep effects. In the model, the influence of shear deformation on the initial stress and creep is considered separately and integrated into the stability coefficient, and then the shear deformation, initial stress, and creep are comprehensively considered, and a prediction model for the stable bearing capacity of the truss column is scientifically proposed. The truss column described in the model includes, but is not limited to, the concrete-filled steel tube truss column, and is also applicable to truss columns made of other materials, including the concrete-filled steel tube truss column made of ultra-high performance concrete UHPC, and the truss column wrapped with FRP, etc. It is also applicable to various truss column forms where the column limbs are rectangular concrete-filled steel tubes, special-shaped concrete-filled steel tubes, hollow steel tubes, and the web members are angle steels, section steels, steel plates, steel bars, hollow steel tubes, etc. This method can accurately predict the axial compression stable bearing capacity of the truss column affected by the initial stress and creep of the concrete-filled steel tube.

[0131] The embodiments of the present invention disclosed above are only used to help explain the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. According to the content of this specification, many modifications and changes can be made. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the relevant technical field can understand and utilize the present invention well.

Claims

1. A method for predicting the axial compressive stability bearing capacity of trussed columns considering the effects of initial stress and creep, characterized in that: The method comprises: Step 1: Determine the basic parameters that affect the stable bearing capacity of the truss column throughout its life; Step 2: According to the effect of shear deformation of trussed columns on reducing the Euler critical force, the ratio of the deflection under the influence of initial stress of shear deformation and the initial deflection amplified by the bending moment is calculated and recorded as the initial stress influence amplification coefficient; Step 3: According to the magnification effect of the shear deformation of the truss column on the slenderness ratio of the limb column, the converted slenderness ratio of the truss column is obtained, and the ratio of the deflection under the influence of shear deformation and creep to the initial deflection magnified by the bending moment is calculated and recorded as the creep influence magnification coefficient; Step 4: Using the initial stress influence magnification factor and the creep influence magnification factor, obtain the stability coefficient of the trussed column after considering the initial stress and creep; Step 5: Using the stability coefficient of the truss column after considering the initial stress and creep, obtain the axial compressive stable bearing capacity of the truss column; In step 2, the calculation formula of the initial stress influence amplification coefficient is: In the formula, is the initial stress influence magnification factor of the truss column, which is the amplification of the initial deflection under the influence of shear deformation and initial stress; δ′ is the deflection of the truss column after considering the amplification factor of the shear initial stress influence; δ is the initial deflection after the bending moment is amplified; N y It is the construction load borne by the truss column steel pipe during the construction stage; is the Euler critical force of the truss column; is the Euler critical force of the truss column steel tube; N cr is the Euler critical force of a single column; N y,cr is the Euler critical force of the steel column; is the unit shear angle of the trussed column; is the unit shear angle of the hollow steel tube truss column; In step 3, the calculation formula of the creep influence amplification coefficient is: In the formula, ξ * is the creep influence amplification factor of the truss column, which is the amplification of the initial deflection under the influence of shear deformation and creep; is the converted slenderness ratio of the truss column; n L is the component axial compression ratio; β α is the steel content coefficient of the component; is the creep coefficient of concrete; E s is the elastic modulus of steel; E c is the elastic modulus of concrete; α is the steel content; λ sc is the slenderness ratio of the limb column; N E is the Euler critical force of the truss column section.

2. The method for predicting the axial compressive stability bearing capacity of truss columns considering the effects of initial stress and creep according to claim 1 is characterized in that: In step 1, the basic parameters include initial stress ratio, slenderness ratio, steel content, steel strength grade, long-term load grade, concrete strength grade, linear stiffness ratio of a single limb to the entire cross section, linear stiffness ratio of a single limb to the web, and geometric slenderness ratio.

3. The method for predicting the axial compressive stability bearing capacity of truss columns considering the effects of initial stress and creep according to claim 1 is characterized in that: In step 4, the calculation formula of the stability coefficient of the trussed column after considering the initial stress and creep is: In the formula, is the stability factor of the trussed column after considering initial stress and creep; is the initial stress amplification factor of the truss column; ξ * is the creep influence amplification factor of truss column; is the converted slenderness ratio of the truss column; K is the initial defect coefficient of the component.

4. The method for predicting the axial compressive stability bearing capacity of truss columns considering the effects of initial stress and creep according to claim 1, characterized in that: In step 5, the calculation formula of the axial compressive stability bearing capacity of the truss column is: Where N u is the stable bearing capacity of the truss column; is the stability coefficient of the truss column after considering the initial stress and creep; N0 is the bearing capacity of the axially compressed section of the truss column; A sci is the cross-sectional area of ​​each column limb; f sc is the design value of the compressive strength of concrete-filled steel tubes; n is the number of column members in the component.

5. The method for predicting the axial compressive stability bearing capacity of a truss column considering the effects of initial stress and creep according to any one of claims 1 to 4, characterized in that: The types of truss columns include but are not limited to steel tube concrete truss columns and FRP wrapped truss columns; The column limbs of the truss column include but are not limited to rectangular steel tube concrete, special-shaped steel tube concrete and empty steel tube; The web members of the truss column include but are not limited to angle steel, steel sections, steel plates, steel bars and hollow steel pipes.

6. A truss column axial compression stability bearing capacity prediction system considering the effects of initial stress and creep, characterized by: The system comprises: Basic parameter determination module, used to determine the basic parameters that affect the stable bearing capacity of trussed columns throughout their lifespan; The initial stress influence magnification coefficient calculation module is used to calculate the ratio of the deflection under the influence of the initial stress of the shear deformation and the initial deflection magnified by the bending moment according to the reduction effect of the shear deformation of the truss column on the Euler critical force, which is recorded as the initial stress influence magnification coefficient; The creep influence magnification coefficient calculation module is used to obtain the converted slenderness ratio of the truss column according to the magnification effect of the shear deformation of the truss column on the slenderness ratio of the limb column, and calculate the ratio of the deflection under the influence of shear deformation and creep to the initial deflection magnified by the bending moment, which is recorded as the creep influence magnification coefficient; The stability coefficient acquisition module is used to obtain the stability coefficient of the trussed column after considering the initial stress and creep by using the initial stress influence magnification factor and the creep influence magnification factor; A module for obtaining the axial compressive stable bearing capacity of truss columns is used to obtain the axial compressive stable bearing capacity of truss columns by using the stability coefficient of truss columns after considering initial stress and creep; The calculation formula of the initial stress influence amplification coefficient is: In the formula, is the initial stress influence magnification factor of the truss column, which is the amplification of the initial deflection under the influence of shear deformation and initial stress; δ′ is the deflection of the truss column after considering the amplification factor of the shear initial stress influence; δ is the initial deflection after the bending moment is amplified; N y It is the construction load borne by the truss column steel pipe during the construction stage; is the Euler critical force of the truss column; is the Euler critical force of the truss column steel tube; N cr is the Euler critical force of a single column; N y,cr is the Euler critical force of the steel column; is the unit shear angle of the trussed column; is the unit shear angle of the hollow steel tube truss column; The calculation formula of the creep influence magnification factor is: In the formula, ξ * is the creep influence amplification factor of the truss column, which is the amplification of the initial deflection under the influence of shear deformation and creep; is the converted slenderness ratio of the truss column; n L is the component axial compression ratio; β α is the steel content coefficient of the component; is the creep coefficient of concrete; E s is the elastic modulus of steel; E c is the elastic modulus of concrete; α is the steel content; λ sc is the slenderness ratio of the limb column; N E is the Euler critical force of the truss column section.

7. A computer device comprising a memory and a processor, wherein a computer program is stored in the memory, wherein: When the processor runs the computer program stored in the memory, the steps of the method according to any one of claims 1 to 5 are performed.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a plurality of computer instructions, and the plurality of computer instructions are used to enable a computer to execute the method according to any one of claims 1 to 5.

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