Method and system for predicting axial compression stable bearing capacity of truss column by considering influence of initial stress and creep

Abstract

The invention discloses a method and a system for predicting the axial pressure stable bearing capacity of a trussed column by considering the influence of initial stress and creep, belongs to the technical field of trussed mixed structures, and solves the problem of low precision of predicting the axial pressure stable bearing capacity of the trussed column due to the fact that the influence of initial stress and creep is not considered. The method comprises the steps of determining basic parameters, considering the influence of shear deformation of the trussed column on initial stress, considering the influence of shear deformation of the trussed column on creep, calculating a stability coefficient, calculating the stable bearing capacity of the trussed column and the like. According to the model, an equilibrium differential equation is established based on the mechanics principle, mathematical calculation and derivation are carried out by applying the stability theory, and the influence of shear deformation, initial stress and creep on the axial pressure stable bearing capacity of the truss type column is comprehensively considered, so that the stable bearing capacity prediction method of the truss type column is provided. The method is suitable for predicting the axial pressure stable bearing capacity influenced by the initial stress and creep of the trussed column.

Description

Technical Field

[0001] Truss columns have many advantages such as high bearing capacity and superior overall performance, and are widely used in the main structures of major infrastructure, such as super high-rise buildings, cement kiln tails, heavy industrial plant columns, etc. At the same time, with the development of engineering construction and the deepening of theoretical research, truss columns will also be widely used in large cantilever structures, offshore platforms and other structures.

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

[0003] During the service life of truss columns, long-term loads will have a significant impact on the mechanical properties of truss columns. Due to the aging effect of the core concrete, the steel tube concrete produces creep. When the long-term load is considered alone, the ultimate bearing capacity of the steel tube concrete medium-length column decreases by 13.1%. Since the truss column needs to consider shear deformation, the effect of creep on the ultimate bearing capacity of the truss column with shear deformation is still unknown. Therefore, it is urgent to propose a method for predicting the stable bearing capacity of the truss column with shear deformation by considering concrete creep.

[0004] Essentially, due to the initial stress of the steel tube during the construction process, the elastic stage of the steel tube of the truss column is shortened and enters the elastoplastic stage ahead of time, the sleeve effect is delayed, and the shear deformation amplifies this effect, thereby reducing the ultimate bearing capacity of the component. The long-term deformation of the core concrete in the load-bearing stage increases, the internal force is redistributed, and the influence of shear deformation reduces the ultimate bearing capacity of the component. Therefore, it is urgent to form a prediction method for the axial compressive stability bearing capacity of truss columns that considers 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 truss column axial compression stability bearing capacity prediction method due to failure to consider the influence of initial stress and creep, and to provide a truss column axial compression stability bearing capacity prediction method and system considering the influence of initial stress and creep.

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

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

[0008] 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;

[0009] 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;

[0010] 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;

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

[0012] Furthermore, 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 single limb and entire cross section, linear stiffness ratio of single limb and web member, and geometric slenderness ratio.

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

[0014]

[0015] 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 empty steel tube truss column.

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

[0017]

[0018] 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; is the unit shear angle of the trussed column.

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

[0020]

[0021] 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.

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

[0023]

[0024] 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.

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

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

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

[0028] In a second aspect, the present invention provides a system for predicting the axial compressive stability bearing capacity of a truss column taking into account the effects of initial stress and creep, the system comprising:

[0029] Basic parameter determination module, used to determine the basic parameters that affect the stable bearing capacity of trussed columns throughout their lifespan;

[0030] 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;

[0031] 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;

[0032] 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;

[0033] The module for obtaining the axial compression stable bearing capacity of truss columns is used to obtain the axial compression stable bearing capacity of truss columns by using the stability coefficient of the truss columns after considering the initial stress and creep.

[0034] In a third aspect, the present invention provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, and when the processor runs the computer program stored in the memory, the steps of the method for predicting the axial compressive stability bearing capacity of a truss column considering the effects of initial stress and creep as described above are executed.

[0035] In a fourth aspect, the present invention provides a computer-readable storage medium storing a plurality of computer instructions, wherein the plurality of computer instructions are used to enable a computer to execute the method for predicting the axial compressive stability bearing capacity of a truss column considering the effects of initial stress and creep as described above.

[0036] Beneficial effects of the present invention:

[0037] The present invention provides a method for predicting the axial compressive stable bearing capacity of a truss column considering the influence of initial stress and creep, and a method for calculating the axial compressive stable bearing capacity of a truss column under the influence of shear deformation on initial stress and creep based on the principle of mechanics and stability theory. Specifically, on the basis of fully considering the basic parameters that affect the full-life bearing capacity of the truss column, in terms of the influence of initial stress, a method for calculating the initial stress influence magnification factor of the truss column is proposed; in terms of the influence of creep, a method for calculating the creep influence magnification factor of the truss column is proposed; using the stability theory, a method for calculating the stability coefficient is obtained by the Perry formula, and then the axial compressive 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 trussed columns considering the influence of initial stress and creep by considering the influence of shear deformation on initial stress and creep. In the model, the initial stress and creep amplification coefficient of the trussed column are obtained by correcting the Euler critical force and slenderness ratio under the influence of shear deformation. The equilibrium differential equation is solved from the static equilibrium equation 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 trussed column is solved. By establishing a mechanical model, applying stability theory, and performing mathematical operations, the formula for the stable bearing capacity of the trussed column is rigorously derived, and a method for predicting the axial compression stable bearing capacity of the trussed column considering the influence of initial stress and creep is proposed. Overall, this prediction method has the following advantages:

[0039] (1) The previous models did not consider the influence of shear deformation on initial stress. The present invention analyzes the shear deformation of truss columns based on basic mechanical principles and proposes an initial stress influence amplification factor based on existing research experience.

[0040] (2) The previous model did not consider the influence of shear deformation on creep. The present invention proposed a creep influence amplification factor by studying and analyzing the shear deformation of truss columns. Thus, a more scientific method for predicting the axial compressive stable bearing capacity of truss columns considering the influence of initial stress and creep is proposed, and the axial compressive stable bearing capacity of truss columns under the influence of initial stress and creep can be accurately predicted.

[0041] Different from single-leg columns that consider initial stress and creep, trussed columns need to consider the influence of shear deformation on initial stress and creep. The prediction model solves the complex problem that shear deformation is not easy to consider in the influence of creep and initial stress. The model can accurately predict the axial compressive stability bearing capacity of trussed columns affected by initial stress and creep, and at the same time shows broad applicability and wide application.

[0042] (3) The method of the present invention has simple steps, reasonable design and clear concept, which can solve the complex problem that shear deformation is not easy to consider in initial stress and creep, and is convenient for designers to calculate and analyze.

[0043] (4) The truss columns described in the model include but are not limited to steel tube concrete truss columns. They are also applicable to truss columns made of other materials. They are also applicable to steel tube concrete truss columns made of ultra-high performance concrete (UHPC) and FRP-wrapped truss columns. The model is also applicable to various truss column forms, such as rectangular steel tube concrete, special-shaped steel tube concrete, and hollow steel tube, and the web members are angle steel, steel section, steel plate, steel bar, hollow steel tube, etc. The model shows wide applicability and broad development potential.

[0044] The present invention is suitable for predicting the axial compression stable bearing capacity of truss columns under the influence of initial stress and creep. Compared with the traditional single-leg steel tube concrete, the stable bearing capacity prediction method of the present invention considers the influence of initial stress and creep. The truss column needs to consider the influence of shear deformation on initial stress and creep. It 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

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

[0047] Figure 2 Schematic diagram of the elevation and section of the truss column according to the embodiment of the present invention;

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

[0049] Figure 4 The front view and cross-sectional view of the truss column for experimental verification of the method for predicting the axial compressive stability bearing capacity of the truss column considering the initial stress and creep effects according to the embodiment of the present invention;

[0050] Figure 5 This is a comparison chart of the experimental measured results of the method for predicting the axial compressive stability bearing capacity of trussed columns taking into account the influence of initial stress and creep and the prediction results of the model.

[0051] In the figure, 1-column steel pipe; 2-web member; 3-column concrete; 4-end plate. DETAILED DESCRIPTION

[0052] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0053] Embodiment 1: A method for predicting the axial compressive stability bearing capacity of a trussed column considering the effects of initial stress and creep, the method comprising:

[0054] Step 1: Determine the basic parameters that affect the stable bearing capacity of the truss column throughout its life;

[0055] 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;

[0056] 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;

[0057] 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;

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

[0059] This implementation method takes into account the influence of shear deformation in truss columns and is used to calculate and analyze the stable bearing capacity of truss columns under the influence of initial stress and creep. Starting from the principle of mechanics, using stability theory and mathematical derivation, the influence of shear deformation of truss columns on initial stress and creep is comprehensively considered, and a prediction method for the stable bearing capacity of truss columns under the influence of initial stress and creep is proposed.

[0060] This implementation method fully considers the influence of shear deformation that must be considered in the calculation of the stable bearing capacity of truss columns with initial stress and creep. It is necessary to derive complex formulas based on mechanical principles and relevant theories, consider the amplifying effect of shear deformation on initial stress and creep, and propose initial stress and creep amplification coefficients considering the influence of shear deformation respectively. It is technically difficult to predict the stable bearing capacity of truss columns with initial stress and creep. This prediction method solves the complex problem that shear deformation is not easy to consider in initial stress and creep, and thus innovatively proposes a prediction method for the stable bearing capacity of truss columns under the influence of initial stress and creep.

[0061] Embodiment 2: This embodiment further defines the method for predicting the axial compressive stability bearing capacity of trussed columns considering the effects of initial stress and creep as described above. In this embodiment, the basic parameters in step 1 are further defined, specifically including:

[0062] 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 single limb and entire cross section, linear stiffness ratio of single limb and web member, and geometric slenderness ratio.

[0063] In this implementation, the linear stiffness ratio of a single limb and the entire cross-section and the linear stiffness ratio of a single limb and the web member are used as basic parameters affecting the stable bearing capacity of the truss column over its entire life cycle. This allows for a relatively simple and convenient calculation of the unit shear angle of the truss column and the unit shear angle of the empty steel tube truss column, thereby avoiding complicated formula calculations and facilitating the control and comparative analysis of the parameter range.

[0064] Implementation method 3: This implementation method is a further limitation on the method for predicting the axial compressive stability bearing capacity of trussed columns considering the effects of initial stress and creep as described above. In this implementation method, the initial stress influence magnification factor in step 2 is further limited, specifically including:

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

[0066]

[0067] 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 empty steel tube truss column.

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

[0069] Embodiment 4: This embodiment further limits the method for predicting the axial compressive stability bearing capacity of trussed columns considering the effects of initial stress and creep as described above. In this embodiment, the creep influence magnification factor in step 3 is further limited, specifically including:

[0070] In step 3, the calculation formula of the creep influence amplification coefficient is:

[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 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; is the unit shear angle of the trussed column.

[0073] The calculation method of creep influence magnification coefficient of this embodiment proposes creep magnification of truss columns considering the influence of shear deformation on creep, and takes into account the influence of shear deformation existing in truss columns, and can calculate and analyze the creep influence of truss columns. This calculation method calculates and analyzes creep magnification under the influence of shear deformation by considering the influence of shear deformation existing in truss columns on creep. This embodiment can solve the problem that the stable bearing capacity of truss columns with creep is difficult to calculate, and can more accurately calculate and predict the stable bearing capacity of truss columns with creep, providing technical theoretical support for actual engineering design and calculation.

[0074] Embodiment 5: This embodiment further limits the method for predicting the axial compressive stability bearing capacity of trussed columns considering the influence of initial stress and creep as described above. In this embodiment, in step 4, the stability coefficient of the trussed column after considering initial stress and creep is further limited, specifically including:

[0075] In step 4, the calculation formula of the stability coefficient of the trussed column after considering the initial stress and creep is:

[0076]

[0077] 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.

[0078] The calculation method of this embodiment can obtain a wider range of application space. The two calculation methods are applicable to various steel tube concrete cross-section forms, including rectangles, polygons, etc.; in the process of formula derivation, based on the Perry formula, the initial stress and creep of the truss column can be easily taken into account in the formula, and no complex cross terms will be generated in the process of formula derivation. The derivation result is concise and easy for engineering design calculation; the stable bearing capacity of the truss column with initial stress and creep is calculated, and the calculation result is reliable and has high accuracy, and can more accurately predict the stable bearing capacity of the truss column under the influence of initial stress and creep.

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

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

[0081]

[0082] 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.

[0083] The calculation method of this embodiment can obtain a wider range of application space. The two calculation methods are applicable to various steel tube concrete cross-section forms, including rectangles, polygons, etc.; in the process of formula derivation, based on the Perry formula, the initial stress and creep of the truss column can be easily taken into account in the formula, and no complex cross terms will be generated in the process of formula derivation. The derivation result is concise and easy for engineering design calculation; the stable bearing capacity of the truss column with initial stress and creep is calculated, and the calculation result is reliable and has high accuracy, and can more accurately predict the stable bearing capacity of the truss column under the influence of initial stress and creep.

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

[0085] The types of truss columns include but are not limited to steel tube concrete truss columns or FRP wrapped truss columns;

[0086] The column limbs of the truss column include but are not limited to rectangular steel tube concrete, special-shaped steel tube concrete or empty steel tube;

[0087] The web members of the truss column include but are not limited to angle steel, steel section, steel plate, steel bar or hollow steel pipe.

[0088] This embodiment provides an applicable scope of the prediction method of the present application. All types of truss columns within the applicable scope can accurately predict the axial compressive stable bearing capacity of the truss columns through the above method.

[0089] Embodiment 8: This embodiment is based on Embodiment 1 of the method for predicting the axial compressive stability bearing capacity of a truss column considering the effects of initial stress and creep as described above, and specifically includes:

[0090] As Figure 2 Taking the two types of truss columns, the flat web member and the diagonal web member, as examples, the steel tube column limb 1 and the column limb concrete 3 are combined into a steel tube concrete column limb, the internal column limb concrete 3 plays a supporting role, and the external steel tube column limb 1 plays a restraining role, and coordinates the deformation and bearing with the web member 2 and the end plate 4. The two ends of the web member 2 are welded to the column limb steel tube 1, and the column limb steel tube 1 is filled with concrete to form the column limb concrete 3. The radius of the column limb concrete 3 is equal to the inner radius of the steel tube column limb 1, and the two ends of the column limb steel tube are fully welded to the end plate 4 to form a more typical truss column.

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

[0092] (1) According to Figure 1 The calculation process shown in the figure determines the basic parameters that affect the stable bearing capacity of the truss column throughout its life: initial stress ratio, slenderness ratio, steel content ratio, steel strength grade; long-term load grade, concrete strength grade; linear stiffness ratio of a single leg and the entire section, linear stiffness ratio of a single leg and web member, geometric slenderness ratio;

[0093] (2) Considering the influence of shear deformation of truss columns on initial stress: Considering the reduction of Euler critical force due to shear deformation of truss columns, the ratio of deflection under the influence of initial stress of shear deformation and initial deflection magnified by bending moment is calculated, i.e., initial stress influence magnification coefficient. The initial stress magnification coefficient is calculated to consider the influence of shear deformation of truss columns on initial stress;

[0094] This step considers the construction load N y When acting on the column steel pipe, Figure 3 As shown in the figure, 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 truss column considering the influence of the initial stress, and the steel pipe will enter the elastic stage earlier than the truss column that is not affected by the initial stress.

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

[0096] This step considers the influence of aging, such as Figure 3 As shown, the long-term load N L Acting 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 load gradually loaded from the construction load to the long-term load, and the CD section is the change of the long-term load sustained load.

[0097] (4) Calculate the stability coefficient of the trussed column after considering the initial stress and creep: According to the principle of mechanics, the equilibrium differential equation is listed and solved. The marginal yield criterion is adopted and the stability coefficient of the trussed column after considering the initial stress and creep is calculated according to the Perry formula;

[0098] (5) Calculation of stable bearing capacity of truss column: The stable bearing capacity of truss column is calculated according to the calculation formula of stable bearing capacity of truss column; the ultimate load N of the model on truss column u The above steps can be used to conveniently and accurately predict the axial compressive stability bearing capacity of truss columns considering the effects of initial stress and creep.

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

[0100] Furthermore, in step (2), the Euler critical force N of a single column limb under the shear deformation is considered separately. cr and Euler critical force of steel pipe column N y,cr The Euler critical force of the truss column is obtained by Euler critical force of truss column steel tube The influence of shear deformation of truss column on initial stress is considered, and the ratio of deflection of truss column considering initial stress to initial deflection after moment amplification is used to measure the amplification effect of initial stress on deflection of truss column.

[0101]

[0102] calculate;

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

[0104] Furthermore, in step (3), the shear deformation of the truss column is taken into account in the slenderness ratio of the truss column. In the column, the slenderness ratio λ sc Multiply by the shear deformation magnification factor to consider the effect of shear deformation on the creep of truss columns. Through mechanical analysis and calculation, the deflection under the influence of shear deformation and creep and the initial deflection after the bending moment is magnified are obtained respectively. The ratio of the two is the magnification of the initial deflection by the creep of the truss column. According to the formula

[0105]

[0106] calculate;

[0107] 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 column limb; N E is the Euler critical force of the truss column section (N); is the unit shear angle of the trussed column.

[0108] Furthermore, in step (4), the initial stress and creep, as well as the additional deflection caused by shear deformation and the deflection caused by bending deformation are superimposed to obtain the actual deflection y, and the equilibrium differential equation for the actual deflection y is listed. After solving the equilibrium differential equation, the sine half-wave function of the actual deflection y is obtained. The edge yield criterion is adopted, and the stability coefficient of the trussed column after considering the initial stress and creep is obtained by the Perry formula. According to the formula

[0109] calculate;

[0110] 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, which is usually taken as 0.25.

[0111] Furthermore, step (5) uses the calculation formula for the axial compressive stability bearing capacity of truss columns in the Code for Design of Concrete-Filled Steel Tube Structures GB50936-2014.

[0112]

[0113]

[0114] calculate;

[0115] Where N u is the stable bearing capacity of the truss column (N); is the stability coefficient of the truss column after considering initial stress and creep; N0 is the bearing capacity of the axially compressed 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 compressive strength of concrete-filled steel tube (MPa); n is the number of column members of the component.

[0116] Implementation method 9: This implementation method is based on the implementation method 2 of the method for predicting the axial compressive stability bearing capacity of truss columns considering the effects of initial stress and creep as described above, and specifically includes:

[0117] Truss column specimens, such as Figure 4 As shown, the initial stress β = 0.57, the specimen is a square section with a length and width of 0.4m, a column limb height of 2.4m, 6 internodes, and a calculated length of 0.38m for each internode. Both ends are provided with 60mm extension sections, the column limbs are made of φ80×3.0 steel pipes filled with C40 concrete, and the average compressive strength of the 28d concrete cube is 38.2MPa, and the elastic modulus is 3.21×10 4MPa. The flat and diagonal web members are made of φ48×2.0 hollow steel tubes. The two ends of the specimen are welded with end steel plates with a length and width of 600mm and a thickness of 35mm. The specimen is constructed as follows: Figure 4 As shown in the figure, the specimen steel is Q235 steel, and the measured elastic modulus of the steel is 2.00×10 5 MPa, the yield strength and tensile strength are 300MPa and 450MPa respectively.

[0118] The prediction method of axial compressive stable bearing capacity of truss columns considering the influence of initial stress and creep is used to calculate the basic parameters affecting the stable bearing capacity of truss columns over their entire life span determined by experiments. The calculation process is as follows:

[0119] (1) Determine the basic parameters that affect the stable bearing capacity of trussed columns throughout their lifespan: initial stress ratio 0.57, slenderness ratio of column limbs λ sc The measured yield strength and tensile strength of steel are 300MPa and 450MPa respectively; the average compressive strength of C40 concrete cube measured at 28d is 38.2MPa.

[0120] (2) Considering the influence of shear deformation of truss column on initial stress: Considering the reduction of Euler critical force due to shear deformation of truss column, the ratio of deflection under the influence of initial stress of shear deformation and initial deflection magnified by bending moment is calculated, that is, the initial stress influence magnification coefficient. The initial stress magnification coefficient is calculated to consider the influence of shear deformation of truss column on initial stress:

[0121]

[0122] (3) Considering the influence of shear deformation of truss columns on creep: Considering the amplifying effect of shear deformation of truss columns on the slenderness ratio of limb columns, the converted slenderness ratio of truss columns is obtained, and the ratio of deflection under the influence of shear deformation and creep to the initial deflection magnified by bending moment is calculated, that is, the creep influence amplification coefficient. The creep influence amplification coefficient is calculated to consider the influence of shear deformation of truss columns on creep;

[0123]

[0124] (4) Calculate the stability coefficient of the trussed column after considering the initial stress and creep: According to the principle of mechanics, list the equilibrium differential equation, solve the equilibrium differential equation, use the edge yield criterion, and follow the formula derived from Perry's formula

[0125] Calculation of stability factor of trussed column considering initial stress and creep:

[0126]

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

[0128]

[0129] The axial compressive stability bearing capacity of the truss column considering the initial stress and creep effect calculated by the prediction method of the present invention is compared with the experimental measured results. Figure 5 As shown, the results show that the prediction method of the axial compression stability bearing capacity of the truss column considering the influence of initial stress and creep of the present invention is relatively accurate.

[0130] The present invention starts from the principle of mechanics, establishes a balanced differential equation, solves the balanced differential equation, and uses stability theory for mathematical calculation and reasoning to establish a method for predicting the axial compressive stable bearing capacity of a trussed column considering the influence of initial stress and creep. In the model, the influence of shear deformation on 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 to scientifically propose a prediction model for the stable bearing capacity of a trussed column. The trussed columns described in the model include but are not limited to steel tube concrete trussed columns, and are also applicable to trussed columns made of other materials, including steel tube concrete trussed columns made of ultra-high performance concrete UHPC, and FRP-wrapped trussed columns. It is also applicable to various trussed column forms in which the column limbs are rectangular steel tube concrete, special-shaped steel tube concrete, and empty steel tubes, and the web members are angle steel, steel, steel plate, steel bar, empty steel tube, etc. This method can accurately predict the axial compressive stable bearing capacity of trussed columns affected by the initial stress and creep of steel tube concrete.

[0131] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use 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: Use the stability coefficient of the truss column after considering the initial stress and creep to obtain the axial compressive stability bearing capacity of the truss column.

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 single limb and entire cross section, linear stiffness ratio of single limb and web member, 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 2, the calculation formula of the initial stress influence amplification coefficient is: In the formula, is the initial stress influence amplification 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 initial shear stress; 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.

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 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; is the unit shear angle of the trussed column.

5. 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 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.

6. 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.

7. 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 6, characterized in that: The types of truss columns include but are not limited to steel tube concrete truss columns or 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 or empty steel tube; The web members of the truss column include but are not limited to angle steel, steel section, steel plate, steel bar or hollow steel pipe.

8. 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; The module for obtaining the axial compression stable bearing capacity of truss columns is used to obtain the axial compression stable bearing capacity of truss columns by using the stability coefficient of the truss columns after considering the initial stress and creep.

9. 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 7 are performed.

10. 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 7.

Images