Substation plane truss type frame beam structure and design method thereof

Abstract

The present application relates to the technical field of power engineering framework design, and particularly relates to a substation plane truss type framework beam structure and a design method thereof, which comprises a chord, a web and an end vertical fixed joint node, the two ends of the chord are vertically fixed with a substation framework column, and the chord is hingedly connected with the web, the plane type framework beam is used, the upper chord and the two side truss web are cancelled, and the two end fixed beam stress model is used for design in and out of the plane, so that the effect of saving the amount of steel is achieved.

Description

Technical Field

[0001] This invention relates to the technical field of power engineering framework design, specifically to a substation planar truss-type frame beam structure and its design method. Background Technology

[0002] Currently, there are two main types of truss beams: triangular lattice truss beams and rectangular lattice truss beams. Triangular lattice truss beams consist of one horizontal truss and two inclined trusses, while rectangular lattice truss beams consist of two horizontal trusses and two vertical trusses. Generally, triangular lattice truss beams are used when the load is smaller and the span is smaller, with chords typically using steel pipe sections and web members typically using angle steel sections. Rectangular lattice truss beams are used when the load is larger and the span is larger, with both chords and web members using steel pipe sections. In both types of truss beams, the web members and chords are connected by gusset plates to achieve the function of the truss unit.

[0003] Chinese utility model patent CN212201517U discloses a substation frame, including a first column, a second column, and a crossbeam. The first and second columns are spaced apart and connected to the foundation. The crossbeam is positioned between the first and second columns, with both ends connected to the first and second columns respectively. The first column includes four first legs, which are fixedly connected to the foundation. The second column includes two second legs, which are hinged to the foundation. A first truss structure is located on the side of the second column opposite to the first column, and a second truss structure is located on the adjacent side of the first truss structure. The steel consumption of the first truss structure is the same as that of the corresponding side of the first column. The load on the first truss structure is greater than that on the second truss structure, and the width of the first truss structure is greater than that of the second truss structure, thus saving steel consumption in the second column.

[0004] The aforementioned patent has the beneficial effect of saving steel usage in substation structures, but it only reduces the height of the ends of the structure beams, resulting in a relatively small reduction in steel usage. Summary of the Invention

[0005] To overcome the above problems, this invention proposes a planar truss-type frame beam structure for substations and its design method. It uses a planar frame beam, eliminating the top chord and the web members of the trusses on both sides, thus saving steel consumption.

[0006] The technical solution of the present invention is as follows:

[0007] A substation planar truss-type frame beam structure includes chord members and web members. The two ends of the chord members are vertically fixed to the substation frame columns, and the chord members are hinged to the web members.

[0008] A design method for a substation planar truss-type frame beam structure includes the following steps:

[0009] Step S10: Calculate the internal forces and deformations of the planar truss-type beam structure.

[0010] Step S20, cross-sectional design of the planar truss-type frame beam structure;

[0011] Step S30: Design of structural requirements for planar truss beam structures;

[0012] Step S40: Node design of the planar truss-type frame beam structure.

[0013] Furthermore, step S10 includes the following steps:

[0014] S11, calculate the internal forces and deformations of a planar truss-type beam structure under vertical loads. The vertical loads include self-weight and conductor vertical loads. The self-weight q and conductor vertical load F... y1 F y2 F y3 Under the action, the mid-span bending moment M of the chord yM Left end bending moment M yL Right end bending moment M yR Left end shear force V yL Right end shear force V yR Mid-span deflection f y They are respectively:

[0015] M yM =M yMf +M yMq

[0016] M yL =M yLf +M yLq

[0017] M yR =M yRf +M yRq

[0018] V yL =V yLf +V yLq

[0019] V yR =V yRf +V yRq

[0020] f y =f yf +f yq

[0021] Where: M yMf M is the mid-span bending moment of the lower chord under vertical conductor load; yMq M is the mid-span bending moment of the lower chord under its own weight;yLf M is the bending moment at the left end of the lower chord under the vertical load of the conductor; yLq M is the bending moment at the left end of the lower chord under its own weight; yRf M is the bending moment at the right end of the lower chord under the vertical load of the conductor; yRq V is the bending moment at the right end of the lower chord under its own weight; yLf V represents the shear force at the left end of the chord under the vertical load of the conductor; yLq V is the shear force at the left end of the lower chord under its own weight; yRf V represents the shear force at the right end of the chord under the vertical load of the conductor; yRq f is the shear force at the right end of the lower chord under its own weight; yf f is the mid-span deflection of the chord under vertical conductor load; yq Let be the mid-span deflection of the lower chord under its own weight.

[0022] S12, calculate the internal forces and deformations of a planar truss-type beam structure under horizontal loads, including wind loads and conductor horizontal loads. Under the action of wind loads and conductor horizontal loads, calculate the mid-span bending moment M of the truss. xM Left end bending moment M xL Right end bending moment M xR Left end shear force V xL Right end shear force V xR Mid-span deflection f x They are respectively:

[0023] M xM =M xMf +M xMp

[0024] M xL =M xLf +M xLp

[0025] M xR =M xRf +M xRp

[0026] V xL =V xLf +V xLp

[0027] V xR =V xRf +V xRp

[0028] f x =f xf +f xp

[0029] Where: M xMf M is the mid-span bending moment of the truss under a horizontal conductor load; xMp M is the mid-span bending moment of the truss under wind load;xLf M is the bending moment at the left end of the truss under a horizontal conductor load; xLp M is the bending moment at the left end of the truss under wind load; xRf M is the bending moment at the right end of the truss under a horizontal conductor load; xRp V is the bending moment at the right end of the truss under wind load; xLf V represents the shear force at the left end of the truss under a horizontal conductor load; xLp V represents the shear force at the left end of the truss under wind load; xRf V represents the shear force at the right end of the truss under a horizontal conductor load; xRp f represents the shear force at the right end of the truss under wind load; xf f is the mid-span deflection of the truss under a horizontal conductor load; xp This represents the mid-span deflection of the truss under wind load.

[0030] Furthermore, step S20 includes the design of the cross-section of the chord and the cross-section of the web members.

[0031] Furthermore, the cross-sectional design of the chord includes calculations of compressive and bending strength, shear strength, equivalent stress, and stability.

[0032] Bending strength verification:

[0033]

[0034] In the formula: A n W is the net cross-sectional area of ​​the chord member. nx γ is the net section modulus in the plane of action of the chord bending moment; x The plastic development coefficient of the chord section; f is the design value of the tensile, compressive and bending strengths of the steel; N, M y To verify the compressive and bending moment values ​​at the section of the chord member, they should be verified separately (N). M M yM ), (N L M yL ), (N R M yR 3 combinations;

[0035] Shear strength verification:

[0036]

[0037] In the formula: t w I is the web area of ​​the chord member; 1x S is the gross moment of inertia of the chord section in the plane of bending moment; S is the area moment of the gross section about the neutral axis at the calculated shear stress of the chord; f v V represents the design value of the shear strength of the steel. y To calculate the design value of the shear force acting along the web plane at the cross section, V is checked respectively. yL VyR ;

[0038] Calculation of equivalent stress:

[0039] At the edge of the calculated height of the web of the end chord, where both normal and shear stresses are present, a verification of the equivalent stress should also be performed.

[0040]

[0041] In the formula: y1 is the distance from the calculation point of the chord section to the neutral axis of the beam; N and M y V y To verify the values ​​of pressure, bending moment, and shear force at the section, the combined force (N) should be verified. L M yL V yL ), (N R M yR V yR ).

[0042] Stability check:

[0043] Since there are numerous web members acting as supports outside the plane of bending moment, no verification is required. The stability is controlled by the in-plane stability, which is calculated as follows:

[0044]

[0045]

[0046] In the formula: A is the gross cross-sectional area of ​​the chord; W 1x The gross section modulus of the fiber in the chord under maximum compression within the plane of bending moment. λ is the axial compression stability coefficient of the chord member in the plane of bending moment action; 1x β is the slenderness ratio of the chord member in the plane of bending moment action; mx The equivalent bending moment coefficients; N, M y To verify the compressive and bending moment values ​​at the section of the chord member, they should be verified separately (N). M M yM ), (N L M yL ), (N R M yR There are 3 combinations, where E is the elastic modulus of steel.

[0047] Furthermore, the cross-section of the web member is designed as an axially loaded member, with an axial force N. v for:

[0048]

[0049] In the formula: n is the number of web members with the same cross section, taken as 2 for intersecting web members and 1 for single web members; θ is the angle between the web member and the chord member; V x For the in-plane shear force acting on the horizontal truss, verify V respectively. xL V xR ; Obtain the axial force N of the web member v The strength and stability of the web members can then be verified as conventional axially compressed members.

[0050] Furthermore, step S30 includes deflection verification and slenderness ratio verification. The deflection of the planar truss beam in both the horizontal and vertical directions should meet the following requirements:

[0051]

[0052] In the formula: L is the length of the chord;

[0053] The slenderness ratio of a planar truss beam in the vertical direction can be converted into the slenderness ratio of the chord itself:

[0054]

[0055] In the formula: A is the gross cross-sectional area of ​​the chord, I 1x The gross moment of inertia of the chord member in the plane of bending moment action;

[0056] The slenderness ratio in the horizontal direction of a planar truss beam can be solved as for a lattice member:

[0057]

[0058] The slenderness ratio of a planar truss beam should satisfy the following in both the vertical and horizontal directions:

[0059] λ 1x ≤150,λ x ≤150.

[0060] Furthermore, step S40 includes the design of the fixed node at the end of the chord and the design of the hinge node between the web member and the chord. The end node is subjected to an axial force N along the longitudinal direction of the beam and a bending moment M in the vertical plane. y Vertical shear force V y Horizontal shear force 0.5V x It should satisfy:

[0061]

[0062] In the formula: m is the number of bolts; h is the vertical spacing of the bolt group; This represents the design value for the shear bearing capacity of high-strength bolts. N is the design value of the tensile bearing capacity of the high-strength bolt; N is the tensile force at the verification node; M yCheck the bending moment at the node; V x V y To verify the shear force values ​​in the x and y directions at the nodes, the combination (N) is verified. L M yL V yL V xL ), (N R M yR V yR V xR ).

[0063] The present invention has the following beneficial effects:

[0064] 1. This invention uses a planar frame beam, eliminating the top chord and the side truss web members, thus saving steel consumption.

[0065] 2. This invention rationally distributes the horizontal and vertical stiffness of the frame beam according to the magnitude of the horizontal and vertical loads it receives.

[0066] 3. Through node design, the stress model of the vertical chord member is a beam with fixed ends, which can reduce the deflection of the beam in the vertical direction.

[0067] 4. The design method proposed in this invention can be used entirely by hand, reducing the reliance on software modeling and calculation in engineering design and improving design efficiency. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of the structure of the present invention;

[0069] Figure 2 This is a force state diagram of the present invention;

[0070] Figure 3 This is a design flowchart of the present invention;

[0071] Figure 4 This is a force model of a chord under vertical load;

[0072] Figure 5 The bending moment diagram of the chord under its own weight;

[0073] Figure 6 The diagram shows the shear force of the chord under its own weight.

[0074] Figure 7 This is a force model of a chord under vertical load from a conductor;

[0075] Figure 8 For a chord member under a vertical load F from a single conductor y1 Bending moment diagram below;

[0076] Figure 9 For a chord member under a vertical load F from a single conductory1 Shear force diagram below;

[0077] Figure 10 The bending moment diagram of the chord under vertical load;

[0078] Figure 11 The diagram shows the shear force of the chord under vertical load;

[0079] Figure 12 This is the force model of the truss under horizontal load in this invention;

[0080] Figure 13 This is a simplified force model of the truss of the present invention under horizontal load;

[0081] Figure 14 This is a bending moment diagram of the truss of the present invention under wind load;

[0082] Figure 15 This is a shear force diagram of the truss of the present invention under wind load;

[0083] Figure 16 This is a simplified force model of the truss of the present invention under horizontal conductor load;

[0084] Figure 17 The truss of this invention is subjected to a horizontal load F on a single conductor. x1 Bending moment diagram below;

[0085] Figure 18 The truss of this invention is subjected to a horizontal load F on a single conductor. x1 Shear force diagram below;

[0086] Figure 19 This is a bending moment diagram of the truss of the present invention under horizontal load;

[0087] Figure 20 This is a shear force diagram of the truss of the present invention under horizontal load;

[0088] Figure 21 This invention provides a model for converting in-plane bending moments of the truss into internal forces in the chord members.

[0089] Figure 22 Force diagram of the vertical fixed joint at the end of the chord member;

[0090] Figure 23 This is a schematic diagram of the vertical fixed connection node at the end of the chord.

[0091] The attached image is labeled as follows:

[0092] 1. Chord member; 2. Web member; 3. Fixed joint. Detailed Implementation

[0093] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0094] like Figures 1-2 As shown, a substation planar truss-type frame beam structure includes a chord 1, a web member 2, and end vertical fixed nodes 3. The two ends of the chord 1 are vertically fixed to the substation frame columns through the end vertical fixed nodes 3, and the chord 1 and the web member 2 are hinged.

[0095] The planar truss-type frame beam adopts a structural form consisting of two chords 1 and web members 2 between the chords 1, eliminating the top chord and the web members on both sides of the truss. The end nodes of the chords 1 of the planar truss-type frame beam are fixed in the vertical direction, which can reduce the vertical deflection of the frame beam. The planar truss-type frame beam uses the chords 1 themselves for bending and shear resistance in the vertical direction, and the planar truss for bending and shear resistance in the horizontal direction. The chords 1 of the planar truss-type frame beam are compression-bending / tension-bending members, and the chords 1 are designed with steel sections with strong bending resistance in the vertical direction, such as I-beams. This invention uses a planar frame beam, eliminating the top chord and the web members on both sides of the truss, thus achieving the effect of saving steel consumption.

[0096] Planar truss-type frame beams are suitable for working conditions with small spans and small vertical loads, such as when applied to main variable frames (without suspended vertical loads);

[0097] like Figure 3 As shown, a design method for a substation planar truss-type frame beam structure includes the following steps:

[0098] Step S10: Calculate the internal forces and deformations of the planar truss-type beam structure.

[0099] Step S20, cross-sectional design of the planar truss-type frame beam structure;

[0100] Step S30: Design of structural requirements for planar truss beam structures;

[0101] Step S40: Node design of the planar truss-type frame beam structure.

[0102] like Figure 4 As shown, step S10 includes the following steps:

[0103] S11, calculate the internal forces and deformations of the planar truss-type frame beam structure under vertical loads. The vertical loads include self-weight and conductor vertical loads. The forces acting on the frame beam in the vertical direction can be simplified to the forces acting on a single chord member 1 itself.

[0104] like Figure 5-6 As shown, under the action of self-weight q, the mid-span bending moment M yMq and the bending moment M at the left end yLq Bending moment M at the right end yRq They are respectively:

[0105]

[0106] Left end shear force V yLq Shear force V at the right end yRq They are respectively:

[0107]

[0108] The mid-span deflection is:

[0109]

[0110] Where: M yMq M is the mid-span bending moment of the lower chord under its own weight; yLq M is the bending moment at the left end of the lower chord under its own weight; yRq V is the bending moment at the right end of the lower chord under its own weight; yLq V is the shear force at the left end of the lower chord under its own weight; yRq f is the shear force at the right end of the lower chord under its own weight; yq Let be the mid-span deflection of the lower chord under its own weight.

[0111] Where E is the elastic modulus of steel, I 1x Let be the moment of inertia of the section of a single chord member in the vertical plane;

[0112] like Figure 7-9 As shown, under the vertical load of the conductor:

[0113] A vertical load F on a conductor y1 Under the action, the mid-span bending moment M yMf1 and the bending moment M at the left end yLf1 Bending moment M at the right end yRf1 They are respectively:

[0114]

[0115] Left end shear force V yLf1 Shear force V at the right end yRf1 They are respectively:

[0116]

[0117] The mid-span deflection is:

[0118]

[0119] Where I 1x Let c1 be the moment of inertia of a single chord in the vertical plane, and c1 = min(a1, b1).

[0120] Similarly, we can obtain the chord at F y2 Mid-span bending moment M under action yMf2 Bending moment M at the left end yLf2Bending moment M at the right end yRf2 Shear force V at the left end yLf2 Shear force V at the right end yRf2 Mid-span deflection f yf2 ; the chord at F y3 Mid-span bending moment M under action yMf3 Bending moment M at the left end yLf3 Bending moment M at the right end yRf3 Shear force V at the left end yLf3 Shear force V at the right end yRf3 Mid-span deflection f yf3 .

[0121] By superimposing the loads, the vertical loads F of the frame beam along the three conductors can be obtained. y1 F y2 F y3 Mid-span bending moment M under action yMf Left end bending moment M yLf Right end bending moment M yRf Left end shear force V yLf Right end shear force V yRf Mid-span deflection f yf They are respectively:

[0122] M yMf =M yMf1 +M yMf2 +M yMf3

[0123] M yLf =M yLf1 +M yLf2 +M yLf3

[0124] M yRf =M yRf1 +M yRf2 +M yRf3

[0125] V yLf =V yLf1 +V yLf2 +V yLf3

[0126] V yRf =V yRf1 +V yRf2 +V yRf3

[0127] f yf =f yf1 +f yf2 +f yf3

[0128] Where: M yMfM is the mid-span bending moment of the lower chord under vertical conductor load; yMfi M is the mid-span bending moment of the chord under the vertical load of the i-th conductor; yLf M is the bending moment at the left end of the lower chord under the vertical load of the conductor; yLfi M is the bending moment at the left end of the chord under the vertical load of the i-th conductor; yRf M is the bending moment at the right end of the lower chord under the vertical load of the conductor; yRfi V is the bending moment at the right end of the chord under the vertical load of the i-th conductor; yLf V represents the shear force at the left end of the chord under the vertical load of the conductor; yLfi V represents the shear force at the left end of the chord under the vertical load of the i-th conductor; yRf V represents the shear force at the right end of the chord under the vertical load of the conductor; yRfi f is the shear force at the right end of the chord under the vertical load of the i-th conductor; yf f is the mid-span deflection of the chord under vertical conductor load; yfi Let be the mid-span deflection of the chord under the vertical load of the i-th conductor.

[0129] like Figure 10-11 As shown, in summary, under the combined action of its own weight and the vertical load of the conductor:

[0130] The chord members of the substation's planar truss-type frame beam are subjected to vertical loads, namely, self-weight q and conductor vertical load F. y1 F y2 F y3 Under the action of the mid-span bending moment M yM Left end bending moment M yL Right end bending moment M yR Left end shear force V yL Right end shear force V yR Mid-span deflection f y They are respectively:

[0131] M yM =M yMf +M yMq

[0132] M yL =M yLf +M yLq

[0133] M yR =M yRf +M yRq

[0134] V yL =V yLf +V yLq

[0135] V yR =V yRf +V yRq

[0136] f y =f yf +f yq

[0137] Where: M yM M is the mid-span bending moment of the lower chord under vertical load; yL M is the bending moment at the left end of the lower chord under vertical load; yR V is the bending moment at the right end of the lower chord under vertical load; yL V represents the shear force at the left end of the lower chord under vertical load; yR f is the shear force at the right end of the lower chord under vertical load; y This represents the mid-span deflection of the chord under vertical load.

[0138] like Figure 12-13 As shown in Figure S12, calculate the internal forces and deformations of the planar truss-type frame beam structure under horizontal loads, including wind loads and conductor horizontal loads. In the horizontal direction, the planar truss-type frame beam forms a bending-resistant system through planar trusses.

[0139] Considering the bending resistance at the ends of the truss, the planar truss beam is analyzed as a whole as a beam with fixed ends during the stress analysis:

[0140] like Figure 14-15 As shown, under a uniformly distributed wind load p, the mid-span bending moment M of the truss is easily obtained. xMp Bending moment M at the left end xLp Bending moment M at the right end xRp They are respectively:

[0141]

[0142] Left end shear force V xLp Shear force V at the right end xRp They are respectively:

[0143]

[0144] The mid-span deflection of the truss consists of bending deformation and shear deformation. The bending deformation can be calculated as a beam fixed at both ends, while the shear deformation is caused by the axial deformation of the web members. Therefore, the mid-span deflection is:

[0145]

[0146] In the formula: f xp I represents the mid-span deflection of the truss under wind load. x The moment of inertia of the planar truss beam in the horizontal direction; Let N be the axial force of the k-th web member when a unit load is applied at mid-span. pk Let l be the axial force of the k-th web member under wind load. kand A fk These are the length and cross-sectional area of ​​the k-th web member, respectively.

[0147] Let A be the cross-sectional area of ​​the chord and E be the elastic modulus of the steel, then the bending stiffness of the planar truss in the plane is:

[0148] EI x =EAH 2 / 2

[0149] Where H is the distance between the chord members.

[0150] like Figure 16-18 As shown, under the action of a horizontal load on the conductor:

[0151] This design technology considers the stress situation when the conductor load is asymmetrical. The conductor suspension point distribution is as follows: Figure 16 As shown, during the force analysis, F is respectively... x1 F x2 F x3 The analysis is performed, and internal forces and deformations are superimposed.

[0152] Under a horizontal load F on a conductor x1 Under the action, the mid-span bending moment M of the truss xMf1 and the bending moment M at the left end xLf1 Bending moment M at the right end xRf1 They are respectively:

[0153]

[0154] Left end shear force V xLf1 Shear force V at the left end xRf1 They are respectively:

[0155]

[0156] The mid-span deflection of the truss consists of bending deformation and shear deformation. The bending deformation can be calculated as a beam fixed at both ends, while the shear deformation is caused by the axial deformation of the web members. Therefore, the mid-span deflection is:

[0157]

[0158] Where I x Let c1 be the moment of inertia of the planar truss beam in the horizontal direction; c1 = min(a1, b1); N represents the axial force of the k-th web member under a unit load applied at mid-span. f1k For the horizontal load F on the conductor x1 Axial force of the k-th web member under action; l k Let A be the length of the k-th web member; fk Let be the cross-sectional area of ​​the k-th web member.

[0159] Similarly, we can obtain the truss at F x2 Mid-span bending moment M under action xMf2 Bending moment M at the left end xLf2 Bending moment M at the right end xRf2 Shear force V at the left end xLf2 Shear force V at the right end xRf2 Mid-span deflection f xf2 ; Truss in F x3 Mid-span bending moment M under action xMf3 Bending moment M at the left end xLf3 Bending moment M at the right end xRf3 Shear force V at the left end xLf3 Shear force V at the right end xRf3 Mid-span deflection f xf3 .

[0160] By superimposing the loads, the mid-span bending moment M of the frame beam truss under the action of three horizontal conductor loads can be obtained. xMf Left end bending moment M xLf Right end bending moment M xRf Left end shear force V xLf Right end shear force V xRf Mid-span deflection f xf They are respectively:

[0161] M xMf =M xMf1 +M xMf2 +M xMf3

[0162] M xLf =M xLf1 +M xLf2 +M xLf3

[0163] M xRf =M xRf1 +M xRf2 +M xRf3

[0164] V xLf =V xLf1 +V xLf2 +V xLf3

[0165] V xRf =V xRf1 +V xRf2 +V xRf3

[0166] f xf =f xf1 +f xf2 +f xf3

[0167] Where: MxMf M is the mid-span bending moment of the truss under a horizontal conductor load; xMfi M is the mid-span bending moment of the truss under the horizontal load of the i-th conductor; xLf M is the bending moment at the left end of the truss under a horizontal conductor load; xLfi M represents the bending moment at the left end of the truss under the horizontal load of the i-th conductor; xRf M is the bending moment at the right end of the truss under a horizontal conductor load; xRfi V is the bending moment at the right end of the truss under the horizontal load of the i-th conductor; xLf V represents the shear force at the left end of the truss under a horizontal conductor load; xLfi V represents the shear force at the left end of the truss under the horizontal load of the i-th conductor; xRf V represents the shear force at the right end of the truss under a horizontal conductor load; xRfi f represents the shear force at the right end of the truss under the horizontal load of the i-th conductor; xf f is the mid-span deflection of the truss under a horizontal conductor load; xfi Let be the mid-span deflection of the truss under the horizontal load of the i-th conductor.

[0168] like Figures 19-20 As shown, in summary, under the action of horizontal loads (wind load and conductor horizontal load), the mid-span bending moment M xM Left end bending moment M xL Right end bending moment M xR Left end shear force V xL Right end shear force V xR Mid-span deflection f x They are respectively:

[0169] M xM =M xMf +M xMp

[0170] M xL =M xLf +M xLp

[0171] M xR =M xRf +M xRp

[0172] V xL =V xLf +V xLp

[0173] V xR =V xRf +V xRp

[0174] f x =f xf +f xp

[0175] Where: M xM M is the mid-span bending moment of the truss under horizontal load; xL M is the bending moment at the left end of the truss under horizontal load; xR V is the bending moment at the right end of the truss under horizontal load; xL V represents the shear force at the left end of the truss under horizontal load. xR f represents the shear force at the right end of the truss under horizontal load. x This represents the mid-span deflection of the truss under horizontal load.

[0176] Furthermore, step S20 includes the cross-sectional design of the chord 1 and the cross-sectional design of the web member 2.

[0177] Under vertical loads, the stress on a planar truss beam can be transformed into stress on the chord members, which then become bending members. From the preceding analysis, the mid-span bending moment M of the chord member under vertical loads can be obtained. yM Left end bending moment M yL Right end bending moment M yR Left end shear force V yL Right end shear force V yR Under horizontal load, the mid-span bending moment M of the planar truss beam can be obtained from the aforementioned analysis. xM Left end bending moment M xL Right end bending moment M xR Left end shear force V xL Right end shear force V xR At this point, the web members resist shear and the chord members resist bending, and can both be simplified as axially loaded members.

[0178] like Figure 21 As shown, for chord 1:

[0179] It is easy to obtain from the characteristics of lattice members that the axial force N at the mid-span of the chord of a planar truss beam under horizontal load is... M 1. Axial force N at the left end L axial force N at the right end R They are respectively:

[0180]

[0181] Where: H is the distance between the chords of the planar truss.

[0182] The chord members of a planar truss beam are bending members under vertical loads and axial compression / tension members under horizontal loads. Therefore, the chord members are tension-bending / compression-bending members, and the strength and stability of the chord member sections can be calculated separately as compression-bending members.

[0183] Bending strength verification:

[0184]

[0185] In the formula: A n W is the net cross-sectional area of ​​the chord member. nx γ is the net section modulus in the plane of action of the chord bending moment; x The plastic development coefficient of the chord section; f is the design value of the tensile, compressive and bending strengths of the steel; N, M y To verify the compressive and bending moment values ​​at the section of the chord member, they should be verified separately (N). M M yM ), (N L M yL ), (N R M yR ) 3 combinations.

[0186] Shear strength verification:

[0187]

[0188] In the formula: t w I is the web area of ​​the chord member; 1x S is the gross moment of inertia of the chord section in the plane of bending moment; S is the area moment of the gross section about the neutral axis at the calculated shear stress of the chord; f v V represents the design value of the shear strength of the steel. y To calculate the design value of the shear force acting along the web plane at the cross section, V is checked respectively. yL V yR .

[0189] Calculation of equivalent stress:

[0190] At the edge of the calculated height of the web of the end chord, where both normal and shear stresses are present, a verification of the equivalent stress should also be performed.

[0191]

[0192] In the formula: y1 is the distance from the calculation point of the chord section to the neutral axis of the beam; N and M y V y To verify the values ​​of pressure, bending moment, and shear force at the section, the combined force (N) should be verified. L M yL V yL ), (N R M yR V yR ).

[0193] Stability check:

[0194] Since there are numerous web members acting as supports outside the plane of bending moment, no verification is required. The stability is controlled by the in-plane stability, which is calculated as follows:

[0195]

[0196]

[0197] In the formula: A is the gross cross-sectional area of ​​the chord; W 1x The gross section modulus of the fiber in the chord under maximum compression within the plane of bending moment. λ is the axial compression stability coefficient of the chord member in the plane of bending moment action; 1x β is the slenderness ratio of the chord member in the plane of bending moment action; mx The equivalent bending moment coefficients; N, M y To verify the compressive and bending moment values ​​at the section of the chord member, they should be verified separately (N). M M yM ), (N L M yL ), (N R M yR ) 3 combinations.

[0198] For the abdominal rod 2:

[0199] The web members of a horizontal truss primarily resist horizontal shear forces and are either axially compressed or axially tensioned, readily yielding the axial force N. v for:

[0200]

[0201] In the formula: n is the number of web members with the same cross section, taken as 2 for intersecting web members and 1 for single web members; θ is the angle between the web member and the chord member; V x For the in-plane shear force acting on the horizontal truss, verify V respectively. xL V xR ; Obtain the axial force N of the web member v The strength and stability of the web members can then be verified as conventional axially compressed members.

[0202] Step S30 includes the calculation of deflection and the calculation of slenderness ratio.

[0203] The deflection of a planar truss beam in both the horizontal and vertical directions should meet the following requirements:

[0204]

[0205] The slenderness ratio of a planar truss beam in the vertical direction can be converted into the slenderness ratio of the chord itself:

[0206]

[0207] The slenderness ratio in the horizontal direction of a planar truss beam can be solved as for a lattice member:

[0208]

[0209] The slenderness ratio of a planar truss beam should satisfy the following in both the vertical and horizontal directions:

[0210] λ 1x ≤150,λ x ≤150 (generally controlled by the slenderness ratio in the vertical direction)

[0211] like Figure 22-23 As shown, step S40 includes the design of the fixed node at the end of the chord and the design of the hinge node between the web member and the chord. The design of the hinge node between the web member and the chord can be based on existing technology and will not be described in detail.

[0212] To ensure that the chord members are fixed in the vertical direction, a high-strength bolt friction connection is proposed. The end nodes are subjected to a longitudinal axial force N and a bending moment M in the vertical plane. y Vertical shear force V y Horizontal shear force 0.5V x It should satisfy:

[0213]

[0214] m is the number of bolts; h is the vertical spacing of the bolt group; This represents the design value for the shear bearing capacity of high-strength bolts. N is the design value of the tensile bearing capacity of the high-strength bolt; N is the tensile force at the verification node; M y Check the bending moment at the node; V x V y To verify the shear force values ​​in the x and y directions at the nodes, the combination (N) is verified. L M yL V yL V xL ), (N R M yR V yR V xR ).

[0215] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A planar truss-type frame beam structure for a substation, characterized in that, The substation planar truss frame beam structure is a planar frame beam, with the top chord and the two side truss web members removed. The substation planar truss frame beam structure includes a chord (1), web members (2) and vertical fixed nodes (3) at the ends. The two ends of the chord (1) are vertically fixed to the substation frame column through the fixed nodes (3). The chord (1) and the web members (2) are hinged. The design method for the substation planar truss-type frame beam structure includes the following steps: Step S10: Calculate the internal forces and deformations of the planar truss-type beam structure. Step S20, cross-sectional design of the planar truss-type frame beam structure; Step S30: Design of structural requirements for planar truss beam structures; Step S40, node design of planar truss beam structure; Step S10 includes the following steps: S11, Calculate the internal forces and deformations of the planar truss-type beam structure under vertical loads. The vertical loads include self-weight and duct vertical loads. The mid-span bending moment of the chord under the action of vertical loads from conductors Left end bending moment Right end bending moment left end shear force Right end shear force Mid-span deflection They are respectively: In the formula: The mid-span bending moment of the chord under the vertical load of the conductor; The mid-span bending moment of the lower chord due to its own weight; The bending moment at the left end of the lower chord under the vertical load of the conductor; The bending moment at the left end of the lower chord is due to its own weight; The bending moment at the right end of the chord under the vertical load of the conductor; The bending moment at the right end of the lower chord is due to its own weight. The shear force at the left end of the chord under the vertical load of the conductor; The shear force at the left end of the lower chord is due to its own weight. The shear force at the right end of the chord under the vertical load of the conductor; The shear force at the right end of the lower chord is due to its own weight. The mid-span deflection of the chord under vertical conductor load; The mid-span deflection of the lower chord under its own weight; S12, calculate the internal forces and deformations of a planar truss beam structure under horizontal loads. Considering the bending capacity at the truss ends, the planar truss beam is analyzed as a beam with fixed ends during the stress analysis. The mid-span deflection of the truss consists of bending deformation and shear deformation. Bending deformation can be calculated as a beam with fixed ends, while shear deformation is caused by the axial deformation of the web members. The horizontal loads include wind loads and conductor horizontal loads. The mid-span bending moment of the truss under the action of horizontal conductor load. Left end bending moment Right end bending moment left end shear force Right end shear force Mid-span deflection They are respectively: In the formula: The mid-span bending moment of the truss under a horizontal conductor load; The mid-span bending moment of the truss under wind load; The bending moment at the left end of the truss under a horizontal conductor load; The bending moment at the left end of the truss under wind load; The bending moment at the right end of the truss under a horizontal conductor load; The bending moment at the right end of the truss under wind load; The shear force at the left end of the truss under a horizontal conductor load; The shear force at the left end of the truss under wind load; The shear force at the right end of the truss under a horizontal conductor load; The shear force at the right end of the truss under wind load; The mid-span deflection of the truss under a horizontal conductor load; The mid-span deflection of the truss under wind load.

2. The design method for a substation planar truss-type frame beam structure as described in claim 1, characterized in that, Step S20 includes the cross-sectional design of the chord (1) and the cross-sectional design of the web member (2).

3. The design method for a substation planar truss-type frame beam structure as described in claim 2, characterized in that, The cross-sectional design of the chord (1) includes calculations of compressive and bending strength, shear strength, equivalent stress, and stability. Bending strength verification: In the formula: Let be the net cross-sectional area of ​​the chord member (1); The net section modulus of the chord member (1) in the plane of bending moment action; is the plastic development coefficient of the section of the chord (1); These are the design values ​​for the tensile, compressive, and bending strengths of steel. , For the chord member (1), the pressure and bending moment values ​​at the section should be checked separately. , ), ( , ), ( , 3 combinations; Shear strength verification: In the formula: Let be the web area of ​​the chord (1); Let be the gross moment of inertia of the chord member (1) in the plane of bending moment action; Calculate the area moment of the gross section about the neutral axis at the shear stress point for the chord (1); This is the design value for the shear strength of the steel. To calculate the design value of the shear force acting along the web plane of the cross section, verification was performed respectively. , ; Calculation of equivalent stress: At the edge of the web of the end chord (1), which bears both large normal stress and shear stress, the equivalent stress should also be checked: In the formula: The distance from the calculation point of the chord section (1) to the neutral axis of the beam; , , To verify the values ​​of pressure, bending moment, and shear force at the cross-section, the combination ( , , ), ( , , ); Stability check: There are numerous web members (2) outside the plane of bending moment action, which can be ignored and are controlled by the stability within the plane of bending moment action. The stability within the plane of bending moment action is checked as follows: In the formula: Let be the gross cross-sectional area of ​​the chord (1); The gross section modulus of the fiber under maximum compression in the plane of bending moment (1); Let be the axial compression stability coefficient of the chord member (1) in the plane of bending moment action; Let be the slenderness ratio of the chord member (1) in the plane of bending moment action; This is the equivalent bending moment coefficient; , For the chord member (1), the pressure and bending moment values ​​at the section should be checked separately. , ), ( , ), ( , ) 3 combinations, This refers to the elastic modulus of steel.

4. The design method for a substation planar truss-type frame beam structure as described in claim 2, characterized in that, The cross-section of the web member (2) is designed as an axially loaded member, with axial force... for: In the formula: The number of web members (2) with the same cross section is 2 when there are intersecting web members (2) and 1 when there is a single web member (2); The angle between the web member (2) and the chord member (1); For the in-plane shear force acting on the horizontal truss, verify the following respectively. , ; The axial force of the web member (2) is obtained. Then, the strength and stability of the web member (2) can be verified as a conventional axially compressed member.

5. The design method for a substation planar truss frame beam structure as described in claim 1, characterized in that, Step S30 includes calculating the deflection and slenderness ratio, specifically the horizontal deflection of the planar truss beam. and vertical deflection All of the following should be satisfied: In the formula: L is the length of the chord (1); The slenderness ratio of a planar truss beam in the vertical direction can be converted into the slenderness ratio of the chord (1) itself: In the formula: Let be the gross cross-sectional area of ​​the chord (1). Let be the gross moment of inertia of the chord member (1) in the plane of bending moment action; The slenderness ratio in the horizontal direction of a planar truss beam can be solved as for a lattice member: In the formula: The distance between the chord members of a planar truss; The slenderness ratio of a planar truss beam should satisfy the following in both the vertical and horizontal directions: 。 6. The design method for a substation planar truss-type frame beam structure as described in claim 1, characterized in that, Step S40 includes the design of the vertical fixed connection node between the end of the chord member (1) and the frame column, and the design of the hinge connection node between the web member (2) and the chord member (1). The design of the hinge connection node between the web member (2) and the chord member (1) can be completed according to existing technology. The chord member end node is subjected to axial force along the longitudinal direction of the beam. Bending moment in the vertical plane Vertical shear force Horizontal shear force It should satisfy: In the formula: This refers to the number of bolts. The vertical spacing of the bolt group; This represents the design value for the shear bearing capacity of high-strength bolts. This represents the design value for the tensile bearing capacity of high-strength bolts. To verify the tensile force at the nodes; Check the bending moment at the nodes; , To verify the shear force values ​​in the x and y directions at the nodes, the combination ( , , , ), ( , , , ).

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