CN102587492B - Simplification method for preliminary design of lattice frame structure - Google Patents

Abstract

The invention discloses a simplification method for a preliminary design of a lattice frame structure. The simplification method comprises the steps of: simplifying a complex lattice frame structure into a frame structure consisting of a small number of beams and columns; and rapidly estimating to obtain the internal force of each rod member which forms a lattice component. The simplification method has the characteristics of convenience for modeling, high calculation speed and higher calculation result precision and is in particular suitable for structural arrangement and section size determination in a preliminary design stage of a large lattice frame structure. An equivalent stiffness calculation formula is adopted in the method, the method has the overall characteristics on the design of a lattice structure scheme, the required work load of regulating the structure scheme can be reduced, the concept intention of a designer is easily reflected in the overall design process, an overall optimal design result is obtained, and the precision obtained through the design of the method can meet the calculation demand of the lattice frame structure in the preliminary design stage very well.

Description

The method for simplifying of lattice type portal frame structure preliminary design

Technical field

The method for simplifying that the present invention relates to a kind of lattice type portal frame structure preliminary design, belongs to civil engineering technical field.

Background technology

In recent years, the develop rapidly of electrical network designing technique, power transformation engineering electrical wiring form and equipment are pursued the development trend of compact Layout, are impelling the technological innovation of power transformation Civil Specialities, and " lattice type portal frame structure " becomes the designing technique receiving much concern.Lattice type portal frame structure is a kind of space lattice frame structure, by lattice girder, lattice column, by being combined to form frame construction, bears external load.Owing to mainly bearing the effect of wind load, its lattice girder, lattice column mainly bear the effect of Bending Moment.This class formation has the advantages that rod member quantity is many, load case is various, structure stress is complicated.Latticed members is being subject to when curved, and the chord member pressurized of a side, opposite side chord member tension form the interior moment of flexure of opposing Moments; When being cut, the horizontal component of lattice member diagonal web member axle power is by balance shearing.Because the distribution of stressed material is away from neutral axis, the ability of its bearing load is strong, rigidity is large.In traditional design cycle, first, tentatively determine the cross section of each root rod member, then adopt the methods such as leverage finite element to calculate the response of structure under load case effect, mainly comprise the maximum internal force that integrally-built distortion and each root rod member bear; After obtaining the internal force of each rod member, according to the strength and stability of Related Formula checking computations rod member.If strength and stability can not meet the demands, strengthen the cross section of primary election rod member; And if strength and stability all has very large having more than needed, suitably reduce the cross section of primary election rod member; After the change of primary election rod member, re-establish computation model, repeat internal force calculating and supporting capacity checking computations also and then revise primary election cross section.Because the variation of bar cross section each time all can bring the variation of the rigidity of structure and distribution thereof, and and then affect the distribution of internal force, till therefore above-mentioned iterative process need to be performed until selected cross section and no longer adjusts.

In addition, for lattice type portal frame structure, owing to mainly bearing wind action, and there is direct relation in the size of wind load and the cross section of each rod member, and therefore, cross section is each time adjusted, and also brings corresponding load adjustment, makes computational process more complicated.

As mentioned above, under traditional lattice type portal frame design cycle, employing be the iterative process that checking computations-cross section, primary election cross section-cross section is adjusted.There is the shortcoming of following three aspects in this process:

1, in a complete design process, such iteration may need to carry out several times, and when the model of structure relates to tens thousand of rod members, iteration and design process cannot be imagined;

2, too pay close attention to Local Members, design result does not have globality.Because design checking computations are based on the single rod member of each root, and easily ignore, structural performance is played to prior factor, such as the root of lattice beam column open, the structure scheme such as step pitch.And the needed modeling process of the arrangement that restructures again after several times iterative computation is complicated and heavy;

3, likely only can obtain local optimal solution.Traditional design process is the technical scheme of a kind of " treat the head when the head aches, pin bitterly cure pin " generally, and the structural response that in engineering structures, the stiffness change of some parts may bring impact is whole, the overall situation, even if therefore obtain a result that meets stress performance according to traditional scheme iteration optimization, can not guarantee the optimality of this result.

Summary of the invention

The object of the invention is be the lattice type portal frame structure design that overcomes prior art too complicated, too pay close attention to Local Members, design result does not have globality, likely only can obtain local optimal solution, can not guarantee it is the problem of overall optimal solution.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A method for simplifying for lattice type portal frame preliminary design, is characterized in that: comprise the following steps:

Step (1), tentatively determines each lattice girder of lattice member to be measured and the size of lattice column and rod member parameter in lattice type portal frame structure;

Step (2), the type of lattice member in judgement lattice type portal frame structure, if plane lattice member execution step (3), if it is empty between lattice member execution step (4);

Step (3), each lattice girder of determining according to step (1) and size and the rod member parameter of lattice column, calculate the elastic modulus E that obtains lattice member chord member _c, web member elastic modulus E _t, single limb chord member bending resistance moment of inertia I _c, sectional area A _c, web member cross-sectional area A _t, diagonal web member length l _t, diagonal web member interlamellar spacing step pitch h, the tilt angle theta of diagonal web member, the length H parameter value in lattice member inflection point, execution step (5) then, wherein Vierendeel girder, post, the length H in inflection point is taken as half of whole lattice member length;

Step (4), each lattice girder of determining according to step (1) and size and the rod member parameter of lattice column, calculate the elastic modulus E that obtains lattice member chord member _c, web member elastic modulus E _t, single limb chord member bending resistance moment of inertia I _c, sectional area A _c, web member cross-sectional area A _t, diagonal web member length l _t, diagonal web member interlamellar spacing step pitch h, diagonal web member tilt angle theta, the length H in lattice member inflection point in the value of both direction, wherein Vierendeel girder, post, the length in inflection point is taken as half of whole lattice member length, and calculates parameter a, b, A _t,a, A _t,b, θ _a, θ _bvalue, execution step (6) then, wherein a is that the root of a direction is opened size, the root that b is other direction is opened size, A _t,aand A _t,bbe respectively the single web member area being parallel on a, b both direction, θ _aand θ _bbe respectively the angle of slope that is parallel to web member on a, b both direction, and meet formula (1), (2),

$\cos {\mathrm{\θ}}_a=\frac{a}{\sqrt{a^2+h^2}}---\left(1\right)$

$\cos {\mathrm{\θ}}_b=\frac{b}{\sqrt{b^2+h^2}}---\left(2\right)$

Step (5), by the described parameter substitution of step (3) lattice member etc. for bending rigidity influence coefficient formula (3) and (4),

${\mathrm{\α}}^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\θ}}{4{\cos }^2\mathrm{\θ}}){\mathrm{hl}}_t}(\frac{4}{E_c{A}_c}+\frac{h^2{\tan }^2\mathrm{\θ}}{E_c{I}_c})---\left(3\right)$

${\mathrm{\α}}_1^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\θ}}{4{\cos }^2\mathrm{\θ}}){\mathrm{hl}}_t}\left(\frac{h^2{\tan }^2\mathrm{\θ}}{E_c{I}_c}\right)---\left(4\right)$

Show that the grade of lattice member is for bending rigidity influence coefficient α, α ₁, and by α, α ₁and the parameter substitution lattice member confirmed of step (3) etc. for bending rigidity design formulas (5),

${\left(\mathrm{EI}\right)}_0=\frac{2E_c{I}_c}{1-\frac{{\mathrm{\α}}_1^2}{{\mathrm{\α}}^2}(1+\frac{3\tanh \left(\mathrm{\α}\right)}{{\mathrm{\α}}^3}-\frac{3}{{\mathrm{\α}}^2})}---\left(5\right)$

Calculate the grade of lattice member for bending rigidity (EI) ₀;

Step (6), by the grade of the described parameter substitution of step (4) lattice member for bending rigidity influence coefficient formula (3) and (4),

${\mathrm{\α}}^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\θ}}{4{\cos }^2\mathrm{\θ}}){\mathrm{hl}}_t}(\frac{4}{E_c{A}_c}+\frac{h^2{\tan }^2\mathrm{\θ}}{E_c{I}_c})---\left(3\right)$

${\mathrm{\α}}_1^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\θ}}{4{\cos }^2\mathrm{\θ}}){\mathrm{hl}}_t}\left(\frac{h^2{\tan }^2\mathrm{\θ}}{E_c{I}_c}\right)---\left(4\right)$

Show that the grade of lattice member is for bending rigidity influence coefficient α, α ₁, and by α, α ₁and the parameter substitution lattice member confirmed of step (4) etc. for bending rigidity design formulas (5),

${\left(\mathrm{EI}\right)}_0=\frac{2E_c{I}_c}{1-\frac{{\mathrm{\α}}_1^2}{{\mathrm{\α}}^2}(1+\frac{3\tanh \left(\mathrm{\α}\right)}{{\mathrm{\α}}^3}-\frac{3}{{\mathrm{\α}}^2})}---\left(5\right)$

Calculate respectively the lattice member etc. of two major axes orientations for bending rigidity (EI) ₀, and according to lattice member etc. for torsional rigidity design formulas (6),

${\left(\mathrm{GJ}\right)}_0=E_{t}h(\frac{b^2}{a}{A}_{t,a}{\cos }^3{\mathrm{\θ}}_a+\frac{a^2}{b}{A}_{t,b}{\cos }^3{\mathrm{\θ}}_b)---\left(6\right)$

Show that the grade of lattice member is for torsional rigidity (GJ) ₀;

Step (7), according to step (5) or step (6), obtain etc. for bending rigidity (EI) ₀or both direction etc. for bending rigidity (EI) ₀with wait for torsional rigidity (GJ) ₀, according to the axis of lattice member, set up and simplify framework computation model;

Step (8), load application on the described framework computation model of step (7), calculates internal force and the deformation response of Equivalent Beam and equivalent post in framework computation model;

Step (9), the equivalent beam column internal force calculating according to step (8), bears moment of flexure, web member according to chord member and bears the principle of shear and torsion and calculate the rod member internal force needing, and the rod member internal force that described different internal force calculates superposes;

Step (10), observe the distortion of framework computation model and the lattice frame structural member internal force of estimation, if intensity, stable or distortion do not meet the regulation of existing < < Code for design of steel structures > >, return to step (1) and again structural configuration or rod member are selected and adjusted.

The method for simplifying of aforesaid lattice type portal frame structure preliminary design, is characterized in that: step (3) or step (4) are calculated E _c, E _t, I _c, A _c, A _t, l _t, h, θ, a, b parameter value while changing on longitudinally along member, adopt weighted average to calculate.

Beneficial effect of the present invention: the present invention is the frame construction for being comprised of simple beam, post by the lattice type portal frame designs simplification being comprised of lattice girder and lattice column of complexity, can calculate fast the rod member internal force that forms lattice type portal frame framework, have that modeling is convenient, computational speed is fast, the feature that computational solution precision is higher, is specially adapted to large-scale lattice space frame structure and carries out the definite calculating of structural configuration and cross section in the concept phase.By employing, wait for Rigidity Calculation formula, lattice structural concept is carried out to design of overall importance, can reduce structural concept and adjust needed workload, more easily in whole design process, embody designer's concept intention, obtain the design result of global optimization, the precision obtaining by this method design is enough to meet the calculation requirement of lattice type portal frame structure in the concept phase.

Accompanying drawing explanation

Fig. 1 is that frame construction of the present invention is the structural representation of plane lattice member.

Fig. 2 is that frame construction of the present invention is the structural representation of space lattice member.

Fig. 3 is the left side lattice column of specific embodiments of the invention and the horizontal distortion figure of equivalent post.

Fig. 4 is the right side lattice column of specific embodiments of the invention and the horizontal distortion figure of equivalent post.

The specific embodiment

Below in conjunction with Figure of description, the present invention is further illustrated.

The method for simplifying of lattice type portal frame structure preliminary design provided by the invention, by the designs simplification of complicated lattice type portal frame structure, be by the few beam of quantity, the frame construction that post forms, can calculate fast the internal force that forms each rod member of lattice member, there is modeling convenient, computational speed is fast, the feature that computational solution precision is higher, be specially adapted to large-scale lattice space frame structure in the layout of concept phase structure and determining of cross section, and employing etc. is for Rigidity Calculation formula, to the design of lattice structural concept, have of overall importance, can reduce structural concept and adjust needed workload, specific implementation comprises the following steps:

The first step, tentatively determines each lattice girder of lattice member to be measured and the size of lattice column and rod member parameter in lattice type portal frame structure;

Second step, the type of lattice member in judgement lattice type portal frame structure, if plane lattice member is carried out the 3rd step, if it is empty between lattice member carry out the 4th step;

The 3rd step, lattice member is plane lattice member, its structural representation as shown in Figure 1, calculates the elastic modulus E that obtains lattice member chord member _c, web member elastic modulus E _t, single limb chord member bending resistance moment of inertia I _c, sectional area A _c, web member cross-sectional area A _t, diagonal web member length l _t, diagonal web member interlamellar spacing step pitch h, the tilt angle theta of diagonal web member, the length H parameter value in lattice member inflection point, then carry out the 5th step, wherein Vierendeel girder, post, the length H in inflection point is taken as half of whole lattice member length;

The 4th step, lattice member is space lattice member, its structural representation as shown in Figure 2, calculates the elastic modulus E that obtains lattice member chord member _c, web member elastic modulus E _t, single limb chord member bending resistance moment of inertia I _c, sectional area A _c, web member cross-sectional area A _t, diagonal web member length l _t, diagonal web member interlamellar spacing step pitch h, diagonal web member tilt angle theta, the length H in lattice member inflection point in the value of both direction, wherein Vierendeel girder, post, the length in inflection point is taken as half of whole lattice member length, and calculates parameter a, b, A _t,a, A _t,b, θ _a, θ _bvalue, the 6th step then, wherein a is that the root of a direction is opened size, the root that b is other direction is opened size, A _t,aand A _t,bbe respectively the single web member area being parallel on a, b both direction, θ _aand θ _bbe respectively the angle of slope that is parallel to web member on a, b both direction, and meet formula (1), (2),

$\cos {\mathrm{\&theta;}}_a=\frac{a}{\sqrt{a^2+h^2}}---\left(1\right)$

$\cos {\mathrm{\&theta;}}_b=\frac{b}{\sqrt{b^2+h^2}}---\left(2\right)$

The 5th step, by the grade of parameter substitution lattice member described in the 3rd step for bending rigidity influence coefficient formula (3) and (4),

${\mathrm{\&alpha;}}^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\&theta;}}{4{\cos }^2\mathrm{\&theta;}}){\mathrm{hl}}_t}(\frac{4}{E_c{A}_c}+\frac{h^2{\tan }^2\mathrm{\&theta;}}{E_c{I}_c})---\left(3\right)$

${\mathrm{\&alpha;}}_1^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\&theta;}}{4{\cos }^2\mathrm{\&theta;}}){\mathrm{hl}}_t}\left(\frac{h^2{\tan }^2\mathrm{\&theta;}}{E_c{I}_c}\right)---\left(4\right)$

Obtain the grade of lattice member for bending rigidity influence coefficient α, α ₁, and by α, α ₁with the grade of other parameter substitution lattice member of the 3rd pacing amount for bending rigidity design formulas (5),

${\left(\mathrm{EI}\right)}_0=\frac{2E_c{I}_c}{1-\frac{{\mathrm{\&alpha;}}_1^2}{{\mathrm{\&alpha;}}^2}(1+\frac{3\tanh \left(\mathrm{\&alpha;}\right)}{{\mathrm{\&alpha;}}^3}-\frac{3}{{\mathrm{\&alpha;}}^2})}---\left(5\right)$

Calculate the grade of lattice member for bending rigidity (EI) ₀;

The 6th step, by the grade of parameter substitution lattice member described in the 4th step for bending rigidity influence coefficient formula (3) and (4),

${\mathrm{\&alpha;}}^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\&theta;}}{4{\cos }^2\mathrm{\&theta;}}){\mathrm{hl}}_t}(\frac{4}{E_c{A}_c}+\frac{h^2{\tan }^2\mathrm{\&theta;}}{E_c{I}_c})---\left(3\right)$

${\mathrm{\&alpha;}}_1^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\&theta;}}{4{\cos }^2\mathrm{\&theta;}}){\mathrm{hl}}_t}\left(\frac{h^2{\tan }^2\mathrm{\&theta;}}{E_c{I}_c}\right)---\left(4\right)$

Show that the grade of lattice member is for bending rigidity influence coefficient α, α ₁, and by α, α ₁with the grade of other parameter substitution lattice member of the 4th pacing amount for bending rigidity design formulas (5),

${\left(\mathrm{EI}\right)}_0=\frac{2E_c{I}_c}{1-\frac{{\mathrm{\&alpha;}}_1^2}{{\mathrm{\&alpha;}}^2}(1+\frac{3\tanh \left(\mathrm{\&alpha;}\right)}{{\mathrm{\&alpha;}}^3}-\frac{3}{{\mathrm{\&alpha;}}^2})}---\left(5\right)$

Calculate respectively the lattice member etc. of two major axes orientations for bending rigidity (EI) ₀, and according to lattice member etc. for torsional rigidity design formulas (6),

${\left(\mathrm{GJ}\right)}_0=E_{t}h(\frac{b^2}{a}{A}_{t,a}{\cos }^3{\mathrm{\&theta;}}_a+\frac{a^2}{b}{A}_{t,b}{\cos }^3{\mathrm{\&theta;}}_b)---\left(6\right)$

Show that the grade of lattice member is for torsional rigidity (GJ) ₀;

The 7th step, according to the 5th step or the 6th step, obtain etc. for bending rigidity (EI) ₀or both direction etc. for bending rigidity (EI) ₀with wait for torsional rigidity (GJ) ₀, according to the axis of lattice member, set up and simplify framework computation model;

The 8th step, load application on framework computation model described in the 7th step, calculates internal force and the deformation response of Equivalent Beam and equivalent post in framework computation model;

The 9th step, the equivalent beam column internal force calculating according to the 8th step, bears moment of flexure, web member according to chord member and bears the principle of shear and torsion and calculate the rod member internal force needing, and the rod member internal force that different internal force calculates superposes;

The tenth step, observe the distortion of framework computation model and the lattice frame structural member internal force of estimation, if intensity, stable or distortion do not meet the relevant regulations in existing < < Code for design of steel structures > > GB50017, return to the first step and again structural configuration or rod member are selected and adjusted, until intensity, stable or distortion meet industry standard.

The E that described third and fourth step calculates _c, E _t, I _c, A _c, A _t, l _t, h, θ, a, b parameter value while changing on longitudinally along member, adopt weighted average to calculate.

In order to simplify calculation process, while there is straight web member in latticed members, ignore the effect of straight web member; When unidirectional layout that diagonal web member is rigidity, the A in corresponding design formulas _tget half, when being rectangle lattice member, according to be subject to cross section parameter in curved plane and determine corresponding parameter, i.e. I _c, A _cand A _tnumerical value be respectively 2 times of single rod member, but wait the equivalent bending stiffness on both direction for member to calculate respectively; For frame column, half that H is floor height, for Vierendeel girder, half that H is span.

One specific embodiment of the method for simplifying of lattice type portal frame structure preliminary design of the present invention is: a lattice frame, and the chord member of lattice member is L125*10mm, moment of inertia is 3.617*10-6m ⁴, area is 2.4*10-3m ², web member adopts L63*5mm, and area is 6.05*10 ^-4m ².Lattice girder chord member adopts L125*8mm, moment of inertia 2.962*10 ^-6m ⁴, area 1.936*10 ^-3m ², web member is L56*5mm, area 5.35*10 ^-4m ².Between lattice column chord member, spacing is 1.53m, and interval is 1.73m.Between lattice girder chord member, spacing is 1.75m, and interval is 1.3m near bearing, near span centre, is 1.6m.Lattice column height overall 30.01m, lattice girder central span is 28m, left side lattice column bears the horizontal distributed load of 50kN/m.As shown in Figures 3 and 4, contrasted respectively the horizontal distortion of left side and right side lattice column and equivalent post, it is 6526kN that method for simplifying according to the present invention obtains left side post bottom chord axle power, web member axle power is 870kN, right side post bottom chord axle power is 3454kN, web member axle power is 228kN, and according to finite element method, above-mentioned numerical value is respectively 6055kN, 851kN, 3573kN and 245kN, under contrast, its precision is enough to be used in the concept phase, uses this method to greatly reduce the complexity of design.

In sum, the present invention is the frame construction for being comprised of simple beam, post by the lattice type portal frame designs simplification being comprised of lattice girder and lattice column of complexity, can calculate fast the rod member internal force that forms lattice type portal frame framework, have that modeling is convenient, computational speed is fast, the feature that computational solution precision is higher, is specially adapted to large-scale lattice space frame structure and carries out the definite calculating of structural configuration and cross section in the concept phase.By employing, wait for Rigidity Calculation formula, lattice structural concept is carried out to design of overall importance, can reduce structural concept and adjust needed workload, more easily in whole design process, embody designer's concept intention, obtain the design result of global optimization, the precision obtaining by this method design is enough to meet the calculation requirement of lattice type portal frame structure in the concept phase.

More than show and described basic principle of the present invention, principal character and advantage.The technician of the industry should understand; the present invention is not restricted to the described embodiments; that in above-described embodiment and manual, describes just illustrates principle of the present invention; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications, and these changes and improvements all fall in the claimed scope of the invention.The claimed scope of the present invention is defined by appending claims and equivalent thereof.

Claims (2)

1. the method for simplifying of lattice type portal frame structure preliminary design, is characterized in that: comprise the following steps:

Step (1), tentatively determines each lattice girder of lattice member to be measured and the size of lattice column and rod member parameter in lattice type portal frame structure;

Step (2), the type of lattice member in judgement lattice type portal frame structure, if plane lattice member execution step (3), if it is empty between lattice member execution step (4);

Step (3), each lattice girder of determining according to step (1) and size and the rod member parameter of lattice column, calculate the elastic modulus E that obtains lattice member chord member _c, web member elastic modulus E _t, single limb chord member bending resistance moment of inertia I _c, sectional area A _c, web member cross-sectional area A _t, diagonal web member length l _t, diagonal web member interlamellar spacing step pitch h, the tilt angle theta of diagonal web member, the length H parameter value in lattice member inflection point, execution step (5) then, wherein Vierendeel girder, post, the length H in inflection point is taken as half of whole lattice member length;

Step (4), each lattice girder of determining according to step (1) and size and the rod member parameter of lattice column, calculate the elastic modulus E that obtains lattice member chord member _c, web member elastic modulus E _t, single limb chord member bending resistance moment of inertia I _c, sectional area A _c, web member cross-sectional area A _t, diagonal web member length l _t, diagonal web member interlamellar spacing step pitch h, diagonal web member tilt angle theta, the length H in lattice member inflection point in the value of both direction, wherein Vierendeel girder, post, the length in inflection point is taken as half of whole lattice member length, and calculates parameter a, b, A _t,a, A _t,b, θ _a, θ _bvalue, execution step (6) then, wherein a is that the root of a direction is opened size, the root that b is other direction is opened size, A _t,aand A _t,bbe respectively the single web member area being parallel on a, b both direction, θ _aand θ _bbe respectively the angle of slope that is parallel to web member on a, b both direction, and meet formula (1), (2),

$\cos {\mathrm{\&theta;}}_a=\frac{a}{\sqrt{a^2+h^2}}---\left(1\right)$

$\cos {\mathrm{\&theta;}}_b=\frac{b}{\sqrt{b^2+h^2}}---\left(2\right)$

Step (5), by the grade of the described parameter substitution of step (3) lattice member for bending rigidity influence coefficient formula (3) and (4),

${\mathrm{\&alpha;}}^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\&theta;}}{4{\cos }^2\mathrm{\&theta;}}){\mathrm{hl}}_t}(\frac{4}{E_c{A}_c}+\frac{h^2{\tan }^2\mathrm{\&theta;}}{E_c{I}_c})---\left(3\right)$

${\mathrm{\&alpha;}}_1^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\&theta;}}{4{\cos }^2\mathrm{\&theta;}}){\mathrm{hl}}_t}\left(\frac{h^2{\tan }^2\mathrm{\&theta;}}{E_c{I}_c}\right)---\left(4\right)$

Show that the grade of lattice member is for bending rigidity influence coefficient α, α ₁, and by α, α ₁and the parameter substitution lattice member that obtains of step (3) etc. for bending rigidity design formulas (5),

${\left(\mathrm{EI}\right)}_0=\frac{2E_c{I}_c}{1-\frac{{\mathrm{\&alpha;}}_1^2}{{\mathrm{\&alpha;}}^2}(1+\frac{3\tanh \left(\mathrm{\&alpha;}\right)}{{\mathrm{\&alpha;}}^3}-\frac{3}{{\mathrm{\&alpha;}}^2})}---\left(5\right)$

Calculate the grade of lattice member for bending rigidity (EI) ₀;

Step (6), by the grade of the described parameter substitution of step (4) lattice member for bending rigidity influence coefficient formula (3) and (4),

${\mathrm{\&alpha;}}^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\&theta;}}{4{\cos }^2\mathrm{\&theta;}}){\mathrm{hl}}_t}(\frac{4}{E_c{A}_c}+\frac{h^2{\tan }^2\mathrm{\&theta;}}{E_c{I}_c})---\left(3\right)$

${\mathrm{\&alpha;}}_1^2=\frac{E_t{A}_t{H}^2}{4(0.5+\frac{\sin \mathrm{\&theta;}}{4{\cos }^2\mathrm{\&theta;}}){\mathrm{hl}}_t}\left(\frac{h^2{\tan }^2\mathrm{\&theta;}}{E_c{I}_c}\right)---\left(4\right)$

Show that the grade of lattice member is for bending rigidity influence coefficient α, α ₁, and by α, α ₁and the parameter substitution lattice member that obtains of step (4) etc. for bending rigidity design formulas (5),

${\left(\mathrm{EI}\right)}_0=\frac{2E_c{I}_c}{1-\frac{{\mathrm{\&alpha;}}_1^2}{{\mathrm{\&alpha;}}^2}(1+\frac{3\tanh \left(\mathrm{\&alpha;}\right)}{{\mathrm{\&alpha;}}^3}-\frac{3}{{\mathrm{\&alpha;}}^2})}---\left(5\right)$

Calculate respectively the lattice member etc. of two major axes orientations for bending rigidity (EI) ₀, and according to lattice member etc. for torsional rigidity design formulas (6),

${\left(\mathrm{GJ}\right)}_0=E_{t}h(\frac{b^2}{a}{A}_{t,a}{\cos }^3{\mathrm{\&theta;}}_a+\frac{a^2}{b}{A}_{t,b}{\cos }^3{\mathrm{\&theta;}}_b)---\left(6\right)$

Show that the grade of lattice member is for torsional rigidity (GJ) ₀;

Step (7), according to step (5) or step (6), obtain etc. for bending rigidity (EI) ₀or both direction etc. for bending rigidity (EI) ₀with wait for torsional rigidity (GJ) ₀, according to the axis of lattice member, set up and simplify framework computation model;

Step (8), load application on the described framework computation model of step (7), calculates internal force and the deformation response of Equivalent Beam and equivalent post in framework computation model;

Step (9), the equivalent beam column internal force calculating according to step (8), bears moment of flexure, web member according to chord member and bears the principle of shear and torsion and calculate the rod member internal force needing, and the rod member internal force that described different internal force calculates superposes;

Step (10), observe the distortion of framework computation model and the lattice frame structural member internal force of estimation, if intensity, stable or distortion do not meet the regulation in existing < < Code for design of steel structures > >, return to step (1) and again structural configuration or rod member are selected and adjusted.

2. the method for simplifying of lattice type portal frame structure preliminary design according to claim 1, is characterized in that: step (3) or step (4) are calculated E _c, E _t, I _c, A _c, A _t, l _t, h, θ, a, b parameter value while changing on longitudinally along member, adopt weighted average to calculate.

Images