Steel-concrete composite beam flexural capacity optimization design calculation method based on plastic design theory

Abstract

The invention belongs to the technical field of bridge design, particularly relates to a plastic design theory-based steel-concrete composite beam flexural capacity optimization design calculation method, and aims to carry out section optimization analysis on a steel-concrete composite beam according to a principle that a bending moment design value of the steel-concrete composite beam is equal to plastic flexural capacity as optimal control, so as to obtain the optimal flexural capacity of the steel-concrete composite beam. And the optimal section size of the steel-concrete composite beam is obtained. The calculation method has the advantages that the standard is relatively unified, the potential of the material can be relatively well exerted, and the method is not too conservative.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge design, and in particular relates to an optimization design calculation method for the bending bearing capacity of a steel-concrete composite beam based on plastic design theory. Background Art

[0002] In Article 7.2 of the "Design and Construction Specifications for Highway Steel-Concrete Composite Beams" (JTG / T D64-01-2015), it is stipulated that the elastic design method is used to calculate the bending bearing capacity of steel-concrete composite beams. The above elastic design method is relatively conservative and cannot give full play to the potential of the material.

[0003] On the other hand, different provisions on bending capacity in relevant specifications mean that designers have no unified calculation standard when designing.

[0004] So to sum up, there is an urgent need for a relatively unified optimization design and calculation method for the flexural bearing capacity of steel-concrete composite beams based on plastic design theory. Summary of the invention

[0005] The present invention provides a calculation method for optimizing the bending capacity of a steel-concrete composite beam based on plastic design theory. The purpose of the calculation method is to optimize the cross-section of the steel-concrete composite beam according to the principle that the bending moment design value of the steel-concrete composite beam is equal to the plastic bending capacity as the optimal control, and obtain the optimal cross-section size of the steel-concrete composite beam. The advantages of the calculation method include: the standard is relatively unified, and the potential of the material can be relatively well exerted without being too conservative.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problem is: an optimization design calculation method for the bending bearing capacity of a steel-concrete composite beam based on plastic design theory. The purpose of the calculation method is to perform cross-sectional optimization analysis of the steel-concrete composite beam according to the principle that the bending moment design value of the steel-concrete composite beam is equal to the plastic bending bearing capacity for optimal control, so as to obtain the optimal cross-sectional size of the steel-concrete composite beam.

[0007] A further preferred technical solution is that the calculation method is applicable to I-beam-concrete composite beams and open steel box-concrete composite beams.

[0008] A further preferred technical solution is that in the calculation method, according to the change in the position of the plastic neutral axis corresponding to the steel-concrete composite beam, the plastic bending bearing capacity of the composite beam is calculated according to three situations: the plastic neutral axis is located in the concrete bridge deck, the plastic neutral axis is located in the top plate of the steel main beam, and the plastic neutral axis is located in the web of the steel main beam.

[0009] A further preferred technical solution is that: the plastic neutral axis of the steel-concrete composite beam is located in the concrete bridge deck, corresponding to the calculation method of the plastic bending bearing capacity of the actual structure under the positive bending moment load; The plastic neutral axis of the steel-concrete composite beam is located in the top plate and the web of the steel main beam. The plastic bending bearing capacity of the steel-concrete composite beam is calculated in two cases: the actual structure is subjected to positive bending moment and the actual structure is subjected to negative bending moment.

[0010] A further preferred technical solution is that under the action of positive moment load, the plastic bending bearing capacity calculation method with the plastic neutral axis located in the concrete bridge deck is: , in, M pla is the plastic bending capacity (N∙mm); σ conu,c is the ultimate compressive stress of bridge deck concrete (MPa); A con,c is the concrete cross-sectional area in the compression zone (mm 2 ); ZZCEN con,c is the distance from the concrete centroid to the plastic centroid in the compression zone (mm), determined according to the position of the plastic centroid; σ stey is the yield stress of steel beam steel (MPa); A ste is the cross-sectional area of ​​the steel main beam (mm 2 ); ZZCEN ste,t is the distance from the centroid of the steel beam in the tension zone to the plastic centroid (mm), which is determined according to the position of the plastic centroid. A con,c Determine according to the following formula, ; The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: , in, b slab is the effective width of the concrete bridge deck (mm).

[0011] A further preferred technical solution is that under the action of positive moment load, the calculation method of the plastic bending bearing capacity of the composite beam with the plastic neutral axis located in the top plate of the steel beam is: , in,A slab is the cross-sectional area of ​​the bridge deck concrete (mm 2 ); A ste,c is the cross-sectional area of ​​the steel main beam in the compression zone (mm 2 ), determined according to the position of the plastic centroid; ZZCEN ste,c is the distance from the centroid of the steel beam in the compression zone to the plastic centroid (mm), determined according to the position of the plastic centroid; A ste,t is the cross-sectional area of ​​the steel main beam in the tension zone (mm 2 ), determined according to the position of the plastic centroid, The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: , in, h slab is the height of the concrete bridge deck (mm); h p is the support height (mm); b uf For I-beam-concrete composite beams, it is the width of the steel main beam top plate (mm); for open steel box-concrete composite beams, it is the width of the steel main beam top plate (mm).

[0012] A further preferred technical solution is that under the action of negative moment load, the calculation method of the plastic bending bearing capacity of the composite beam with the plastic neutral axis located in the top plate of the steel beam is: , in, σ reby is the yield stress of bridge deck reinforcement (MPa); A reb,i is the total area of ​​the i-th layer of steel bars (mm 2 ); ZZCEN rebi is the distance from the centroid of the i-th layer of steel bars to the plastic centroid (mm), determined according to the position of the plastic centroid, The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: .

[0013] A further preferred technical solution is that under the action of positive bending moment load, the calculation method of the plastic bending bearing capacity of the composite beam with the plastic neutral axis located in the web of the steel beam is: , The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: , in, h is the total height of the main beam section (mm); t lf is the thickness of the bottom plate of the steel main beam (mm); b lf is the bottom plate width of the steel main beam (mm); t w For I-beam-concrete composite beams, it is the thickness of the steel main beam web (mm); for open steel box-concrete composite beams, it is the sum of the thickness of the steel main beam web (mm).

[0014] A further preferred technical solution is that under the action of negative moment load, the calculation method of the plastic bending bearing capacity of the composite beam with the plastic neutral axis located in the web of the steel beam is: , The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: . BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram corresponding to the method for calculating the plastic bending bearing capacity of the steel-concrete composite beam under positive bending moment load in the present invention, with the plastic neutral axis located in the concrete bridge deck.

[0016] Figure 2 It is a schematic diagram corresponding to the calculation method of the plastic bending bearing capacity of the steel-concrete composite beam under the positive bending moment load in the present invention, where the plastic neutral axis is located in the top plate of the steel beam.

[0017] Figure 3 It is a schematic diagram corresponding to the calculation method of the plastic bending bearing capacity of the composite beam of the steel-concrete composite beam under the negative bending moment load in the present invention, where the plastic neutral axis is located in the top plate of the steel beam.

[0018] Figure 4 It is a schematic diagram corresponding to the calculation method of the plastic bending bearing capacity of the steel-concrete composite beam under the positive bending moment load in the present invention, where the plastic neutral axis is located in the web of the steel beam.

[0019] Figure 5 It is a schematic diagram corresponding to the calculation method of the plastic bending bearing capacity of the steel-concrete composite beam under negative bending moment load in the present invention, where the plastic neutral axis is located in the web of the steel beam. DETAILED DESCRIPTION

[0020] The following descriptions are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention.

[0021] As attached Figure 1-5 As shown in the figure, an optimization design calculation method for the flexural bearing capacity of a steel-concrete composite beam based on the plastic design theory is provided. The purpose of the calculation method is to optimize the cross-section of the steel-concrete composite beam according to the principle that the bending moment design value of the steel-concrete composite beam is equal to the plastic flexural bearing capacity as the optimal control, and obtain the optimal cross-section size of the steel-concrete composite beam.

[0022] The calculation method is applicable to I-beam-concrete composite beams and open steel box-concrete composite beams.

[0023] In the calculation method, according to the change in the position of the plastic neutral axis corresponding to the steel-concrete composite beam, the plastic bending bearing capacity of the composite beam is calculated according to three situations: the plastic neutral axis is located in the concrete bridge deck, the plastic neutral axis is located in the top plate of the steel main beam, and the plastic neutral axis is located in the web of the steel main beam.

[0024] The plastic neutral axis of the steel-concrete composite beam is located in the concrete bridge deck, which corresponds to the calculation method of the plastic bending bearing capacity of the actual structure under the action of positive bending moment load; the plastic neutral axis of the steel-concrete composite beam is located in the top plate of the steel main beam and the web of the steel main beam, and the plastic bending bearing capacity of the steel-concrete composite beam is calculated according to two situations: the actual structure is subjected to positive bending moment and negative bending moment.

[0025] As attached Figure 1 As shown in the figure, under the action of positive bending moment load, the calculation method of plastic bending bearing capacity when the plastic neutral axis is located in the concrete bridge deck is: , in, M pla is the plastic bending capacity (N∙mm); σ conu,c is the ultimate compressive stress of bridge deck concrete (MPa); A con,c is the concrete cross-sectional area in the compression zone (mm 2 ); ZZCEN con,c is the distance from the concrete centroid to the plastic centroid in the compression zone (mm), determined according to the position of the plastic centroid; σ stey is the yield stress of steel beam steel (MPa); A ste is the cross-sectional area of ​​the steel main beam (mm 2 ); ZZCEN ste,t is the distance from the centroid of the steel beam in the tension zone to the plastic centroid (mm), which is determined according to the position of the plastic centroid. A con,c Determine according to the following formula, ; The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: , in, b slab is the effective width of the concrete bridge deck (mm).

[0026] As attached Figure 2 As shown in the figure, under the action of positive bending moment load, the calculation method of the plastic bending bearing capacity of the composite beam with the plastic neutral axis located in the top plate of the steel beam is: , in, A slab is the cross-sectional area of ​​the bridge deck concrete (mm 2 ); A ste,c is the cross-sectional area of ​​the steel main beam in the compression zone (mm 2 ), determined according to the position of the plastic centroid; ZZCEN ste,c is the distance from the centroid of the steel beam in the compression zone to the plastic centroid (mm), determined according to the position of the plastic centroid; A ste,t is the cross-sectional area of ​​the steel main beam in the tension zone (mm 2 ), determined according to the position of the plastic centroid, The location of the plastic centroid is given by ZZ pla Sure, ZZ plais the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: , in, h slab is the height of the concrete bridge deck (mm); h p is the support height (mm); b uf For I-beam-concrete composite beams, it is the width of the steel main beam top plate (mm); for open steel box-concrete composite beams, it is the width of the steel main beam top plate (mm).

[0027] As attached Figure 3 As shown in the figure, under the action of negative moment load, the calculation method of the plastic bending bearing capacity of the composite beam with the plastic neutral axis located in the top plate of the steel beam is: , in, σ reby is the yield stress of bridge deck reinforcement (MPa); A reb,i is the total area of ​​the i-th layer of steel bars (mm 2 ); ZZCEN rebi is the distance from the centroid of the i-th layer of steel bars to the plastic centroid (mm), determined according to the position of the plastic centroid, The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: .

[0028] As attached Figure 4 As shown in the figure, under the action of positive bending moment load, the calculation method of the plastic bending bearing capacity of the composite beam with the plastic neutral axis located in the web of the steel beam is: , The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: , in, h is the total height of the main beam section (mm); t lf is the thickness of the bottom plate of the steel main beam (mm); b lf is the bottom plate width of the steel main beam (mm);t w For I-beam-concrete composite beams, it is the thickness of the steel main beam web (mm); for open steel box-concrete composite beams, it is the sum of the thickness of the steel main beam web (mm).

[0029] As attached Figure 5 As shown in the figure, under the action of negative moment load, the calculation method of the plastic bending bearing capacity of the composite beam with the plastic neutral axis located in the web of the steel beam is: , The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: .

[0030] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various modifications can be made within the knowledge of ordinary technicians in the technical field without departing from the purpose of the present invention. These are all non-creative modifications and are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. The optimization design calculation method of the bending bearing capacity of steel-concrete composite beams based on plastic design theory is characterized by The purpose of the calculation method is to perform cross-sectional optimization analysis of the steel-concrete composite beam according to the principle that the bending moment design value of the steel-concrete composite beam is equal to the plastic bending bearing capacity as the optimal control, and obtain the optimal cross-sectional size of the steel-concrete composite beam.

2. The method for optimizing the design and calculation of the bending bearing capacity of steel-concrete composite beams based on plastic design theory according to claim 1 is characterized in that: The calculation method is applicable to I-beam-concrete composite beams and open steel box-concrete composite beams.

3. The method for optimizing the design and calculation of the bending bearing capacity of steel-concrete composite beams based on plastic design theory according to claim 1 is characterized in that: In the calculation method, according to the change in the position of the plastic neutral axis corresponding to the steel-concrete composite beam, the plastic bending bearing capacity of the composite beam is calculated according to three situations: the plastic neutral axis is located in the concrete bridge deck, the plastic neutral axis is located in the top plate of the steel main beam, and the plastic neutral axis is located in the web of the steel main beam.

4. The method for optimizing the design and calculation of the bending bearing capacity of steel-concrete composite beams based on plastic design theory according to claim 3 is characterized in that: The plastic neutral axis of the steel-concrete composite beam is located in the concrete bridge deck, corresponding to the calculation method of the plastic bending bearing capacity of the actual structure under the positive bending moment load; The plastic neutral axis of the steel-concrete composite beam is located in the top plate and the web of the steel main beam. The plastic bending bearing capacity of the steel-concrete composite beam is calculated in two cases: the actual structure is subjected to positive bending moment and the actual structure is subjected to negative bending moment.

5. The method for optimizing the design and calculation of the bending bearing capacity of steel-concrete composite beams based on plastic design theory according to claim 4 is characterized in that Under the action of positive bending moment load, the calculation method of plastic bending bearing capacity with the plastic neutral axis located in the concrete bridge deck is: ， in, M pla is the plastic bending capacity (N∙mm); σ conu,c is the ultimate compressive stress of bridge deck concrete (MPa); A con,c is the cross-sectional area of ​​concrete in the compression zone (mm 2 ); ZZCEN con,c is the distance from the concrete centroid to the plastic centroid in the compression zone (mm), determined according to the position of the plastic centroid; σ stey is the yield stress of steel beam steel (MPa); A ste is the cross-sectional area of ​​the steel main beam (mm 2 ); ZZCEN ste,t is the distance from the centroid of the steel beam in the tension zone to the plastic centroid (mm), which is determined according to the position of the plastic centroid. A con,c Determine according to the following formula, ； The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: ， in, b slab is the effective width of the concrete bridge deck (mm).

6. The method for optimizing the design and calculation of the bending bearing capacity of steel-concrete composite beams based on plastic design theory according to claim 4 is characterized in that Under the action of positive bending moment load, the calculation method of the plastic bending bearing capacity of the composite beam with the plastic neutral axis located in the top plate of the steel beam is: ， in, A slab is the cross-sectional area of ​​the bridge deck concrete (mm 2 ); A ste,c is the cross-sectional area of ​​the steel main beam in the compression zone (mm 2 ), determined according to the position of the plastic centroid; ZZCEN ste,c is the distance from the centroid of the steel beam in the compression zone to the plastic centroid (mm), determined according to the position of the plastic centroid; A ste,t is the cross-sectional area of ​​the steel main beam in the tension zone (mm 2 ), determined according to the position of the plastic centroid, The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: ， in, h slab is the height of the concrete bridge deck (mm); h p is the support height (mm); b uf For I-beam-concrete composite beams, it is the width of the steel main beam top plate (mm); for open steel box-concrete composite beams, it is the width of the steel main beam top plate (mm).

7. The method for optimizing the design and calculation of the bending bearing capacity of steel-concrete composite beams based on plastic design theory according to claim 4 is characterized in that Under the action of negative bending moment load, the calculation method of the plastic bending bearing capacity of the composite beam with the plastic neutral axis located in the top plate of the steel beam is: ， in, σ reby is the yield stress of bridge deck reinforcement (MPa); A reb,i is the total area of ​​the i-th layer of steel bars (mm 2 ); ZZCEN rebi is the distance from the centroid of the i-th layer of steel bars to the plastic centroid (mm), determined according to the position of the plastic centroid, The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: 。 8. The method for optimizing the design and calculation of the bending bearing capacity of steel-concrete composite beams based on plastic design theory according to claim 4 is characterized in that Under the action of positive bending moment load, the calculation method of the plastic bending bearing capacity of the composite beam with the plastic neutral axis located in the web of the steel beam is: ， The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: ， in, h is the total height of the main beam section (mm); t lf is the thickness of the bottom plate of the steel main beam (mm); b lf is the bottom plate width of the steel main beam (mm); t w For I-beam-concrete composite beams, it is the thickness of the steel main beam web (mm); for open steel box-concrete composite beams, it is the sum of the thickness of the steel main beam web (mm).

9. The method for optimizing the design and calculation of the bending bearing capacity of steel-concrete composite beams based on plastic design theory according to claim 4 is characterized in that Under negative moment load, the calculation method of plastic bending capacity of composite beam with plastic neutral axis located in the web of steel beam is: ， The location of the plastic centroid is given by ZZ pla Sure, ZZ pla is the distance from the plastic centroid to the top edge of the section (mm), determined by the following formula: 。

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