1、 Terminology

1.Strength: the ability of the cross-section material or connection to resist failure.Strength calculation is to prevent structural members or connections from being damaged due to material strength being exceeded.

2.Bearing capacity: the maximum internal force that a structure or component can bear without damage due to strength, stability or fatigue; or the maximum internal force when the failure mechanism is formed by plastic analysis; or the internal force when the deformation is not suitable for continuous bearing.

3.Brittle fracture: it generally refers to the sudden brittle fracture of steel structure without warning plastic deformation under tensile stress state.

4.Standard value of strength: yield point (yield strength) or tensile strength of steel specified in national standards.

5.Design value of strength: the standard value of strength of steel or connection divided by the corresponding partial coefficient of resistance.

6.First order elastic analysis: without considering the influence of the second-order deformation on the internal force of the structure, the equilibrium condition is established according to the undeformed structure, and the internal force and displacement of the structure are analyzed according to the elastic stage.

7.Second order elastic analysis: considering the influence of the second-order deformation on the internal force of the structure, the equilibrium condition is established according to the structure after displacement, and the internal force and displacement of the structure are analyzed according to the elastic stage.

8.Buckling: under the action of axial pressure, bending moment and shear force alone or jointly, the member or plate will lose stability due to large deformation inconsistent with the original stress state.

9.Web post buckling strength: the web can continue to bear load after buckling.

10.General height thickness ratio: a parameter whose value is equal to the square root of the quotient of the yield strength of the steel in bending, shear or compression divided by the corresponding bending, shear or local compressive elastic buckling stress of the web.

11.Overall stability: under the action of external load, whether the whole structure or member can be buckled or not

Evaluation of instability.

12.Effective width: the width in the calculation of section strength and stability.Suppose the plate is effective

13.Effective width coefficient: the ratio of effective width to actual width.

14.Effective length: the equivalent length obtained by multiplying the geometric length of the member between its effective restraint points by the coefficient considering the deformation of the rod end and the load condition, so as to calculate the slenderness ratio of the member.The weld length used to calculate the weld joint strength.

15.Slenderness ratio: the ratio of the effective length of the member to the radius of rotation of the member section.

16.Conversion slenderness ratio: in the overall stability calculation of axial compression members, according to the principle of equal critical force, the slenderness ratio of lattice members is converted into solid web members for calculation, or the slenderness ratio used when converting bending torsional and torsional instability into bending instability.

17.Support force: the lateral force required to be applied to the shear center of the member (or the compression flange) in the buckling direction of the supported member (or the compression flange) at the lateral support set to reduce the free length of the compression member (or the compression flange of the member).

18.Unbraced pure frame: a frame which can resist lateral load depending on the flexural capacity of members and joints.

19.Strong braced frame: in the braced frame, the lateral stiffness of the supporting structure (supporting truss, shear wall, elevator shaft, etc.) is large, so the frame can be regarded as the frame without lateral displacement.

20.Weak braced frame: in the braced frame, the lateral stiffness of the braced structure is weak, so the frame can not be regarded as the frame without lateral displacement.

21.Swing column: columns with hinged ends in the frame that can not resist lateral load.

22.Column web node area: the area where the column web is within the beam height range at the rigid joint of frame beam and column.

23.Spherical steel bearing: the steel ball surface that enables the structure to rotate in any direction at the support can be used as the hinged bearing or movable bearing for force transmission.

24.Rubber bearing: rubber, steel sheet and other composite products meeting the requirements of bearing displacement are used as the bearing to transfer the bearing reaction force.

25.Main pipe: in the steel pipe structural member, the pipe fittings continuously connected at the joint, such as the chord in the truss.

26.Branch pipe: in the steel pipe structure, the pipe fittings which are disconnected at the node and connected with the main pipe, such as the web member connected with the main pipe in the truss.

27.Clearance node: the joint where the toe of two branches is away from a certain distance.

28.Lap joint: at the joint of steel pipe, two branch pipes overlap each other.

29.Plane pipe node: the node where the branch pipe and the main pipe are connected in the same plane.

30.Space pipe node: the pipe node formed by connecting branch pipe and main pipe in different plane.

31.Composite member: a member composed of more than one steel plate (or section steel) connected with each other, such as I-section or box section composite beam or column.

32.Steel and concrete composite beam: it is composed of concrete wing plate and steel beam through shear connectors, which can bear overall force.

2、 Symbols

1.Design value of action and action effect

F — concentrated load;

H — horizontal force;

M — bending moment;

N — axial force;

P — pretension of high strength bolt;

Q — gravity load;

R — support reaction force;

V — shear force.

2Calculation index

E — elastic modulus of steel;

EC — elastic modulus of concrete;

G — shear modulus of steel;

Nat — design value of tensile bearing capacity of anchor bolts;

NBT, NBV, NBC — design values of tensile, shear and bearing capacity of a bolt;

NRT, NRV, NRC — design values of tensile, shear and bearing capacity of a rivet;

NCV — design value of shear bearing capacity of a shear connector in composite structure;

Npjtnpjc — design value of bearing capacity of tension and compression branch pipe at pipe joint;

Sb — lateral stiffness of supporting structure (horizontal force generating unit roll angle);

F — design value of tensile, compressive and flexural strength of steel;

FV — design value of shear strength of steel;

FCE — design value of end bearing strength of steel;

FST — design value of tensile strength of reinforcement;

FY — yield strength (or yield point) of steel;

Fat — design value of tensile strength of anchor bolt;

Fbtfbvfbc — design value of tensile, shear and bearing strength of bolts;

Frtfrvfrc — design value of tensile strength, shear strength and bearing strength of rivet;

Fwtfwvfwc — design value of tensile, shear and compressive strength of butt weld;

FWT — design value of tensile, shear and compressive strength of fillet weld;

FC — design value of concrete compressive strength;

Δ U — story displacement of the floor;

[ν q] – the allowable value of deflection caused by the standard value of variable load only;

[ν t] – allowable value of deflection caused by both permanent and variable load standard values;

σ – normal stress; 

σ C — local compressive stress;

σ F — the stress perpendicular to the length direction of fillet weld and calculated according to the effective section of weld;

Δ σ — stress amplitude or reduced stress amplitude of fatigue calculation;

Δ σ – equivalent stress amplitude of variable amplitude fatigue;

[Δ σ] – allowable fatigue stress amplitude;

Σ Cr σ c.cr τ Cr — the critical stress of a plate under the action of bending stress, local compressive stress and shear stress alone;

τ – shear stress; 

τ F — shear stress calculated according to effective section of weld along the length direction of fillet weld;

ρ — mass density. 

3Geometric parameters

A — gross section area;

An — net section area;

H — height of column;

H1, H2, H3 — the height of the upper, middle (or lower) and lower segments of the stepped column;

I — moment of inertia of gross section;

It — torsional moment of inertia of gross section;

IW — fan inertia moment of gross section;

In — moment of inertia of net section;

S — moment of gross section area;

W — gross section modulus;

Wn — net section modulus;

WP — plastic gross section modulus;

Wpn — plastic net section modulus;

Ag — spacing, clearance;

B — the width of the plate or the free overhanging width of the plate;

Bo — unsupported width of flange plate of box section between webs; width of top of concrete slab bracket;

BS — extension width of stiffener;

Be — effective width of plate;

D — diameter;

De — effective diameter;

Do — pore diameter;

E — eccentricity;

H — full height of section; floor height;

HC1 – thickness of concrete slab;

HC2 – thickness of concrete slab support;

He — calculated thickness of fillet weld;

HF — weld leg size of fillet weld;

H ω – height of web.

Ho — calculated height of web plate;

I — section radius of gyration;

L – length or span;

Ll — the distance between the lateral supports of the compression flange of the beam; the connection length of the bolt (or rivet) in the stress direction;

Lo — the effective length of bending buckling;

L ω – effective length of torsional buckling;

LW — the calculated length of weld;

LZ — the assumed distribution length of concentrated load on the edge of calculated height of web;

S — the shortest distance from the root of groove of partial penetration butt weld to the weld surface;

T — thickness of plate; wall thickness of main pipe;

TS — thickness of stiffener;

Tw — thickness of web plate;

α – included angle; 

θ – included angle; stress diffusion angle; 

γ B — general height thickness ratio of beam web in bending calculation;

γ s — general height thickness ratio of beam web in shear calculation;

γ C — general height thickness ratio of beam web under local pressure calculation;

γ – slenderness ratio; 

γ o, γ YZ, γ Z, γ UZ — conversion slenderness ratio,

4Calculation coefficient and others

C — dimensional parameter for fatigue calculation,

K1k2 — the ratio of member linear stiffness;

KS — shear buckling coefficient of member;

OV — branch overlap rate of pipe joint;

N — number of bolts, rivets or connectors; number of stress cycles:

NL — the number of bolts (or rivets) on the calculated section;

NF — the number of friction surfaces of high strength bolt;

NV — number of shear planes of bolt or rivet;

α – linear expansion coefficient; coefficient for calculating lateral force caused by crane swing,

α e — ratio of elastic modulus of steel to concrete;

α e — reduction coefficient of beam section modulus considering effective width of web plate;

α F — equivalent coefficient of under load effect in fatigue calculation;

α o – nonuniform coefficient of stress distribution of column web;

α Y — influence coefficient of steel strength;

α L — the coefficient adopted when the beam web is planed and the top is tight;

α 2I — the augmentation factor of lateral displacement moment of members in the first floor of frame considering second-order effect;

β – the ratio of the outer diameter of the branch pipe to the main pipe; the parameter used to calculate the fatigue strength; 

β B — equivalent critical moment coefficient of beam overall stability;

β F — increase coefficient of strength design value of front fillet weld;

β m, β T — the equivalent moment coefficient for the stability of compression and bending members:

β L — increase coefficient of strength setting value of reduced stress;

γ – strength yield ratio of stud steel; 

γ O — importance coefficient of structure:

γ x, γ Y — cross section plastic development coefficient for principal axis X and Y;

η – adjustment coefficient;

η B — asymmetric influence coefficient of beam section;

η 1, η 2 — parameters used to calculate the effective length of stepped column;

μ — anti sliding coefficient of friction surface of high strength bolt; effective length coefficient of column;

μ 1, μ 2, μ 3 — the effective length coefficients of the upper, middle (or lower) and lower segments of the stepped column;

ξ — the parameter used to calculate the overall stability of the beam;

ρ – effective width coefficient of Web compression zone;

φ – stability coefficient of axial compression member;

φ B, φ ‘B – the overall stability coefficient of the beam;

ψ – increasing coefficient of concentrated load;

ψ n, ψ a, ψ D — parameters used to calculate the bearing capacity of direct welded steel pipe joints.