Technical analysis of space frame structure production and the meaning of main symbols

 The space frame structure is a high-order statically indeterminate structure system. In the analysis of slab space frames, it is generally assumed that the joints are hinged, and the external load is applied to the joints according to the principle of static equivalent. The calculation can be carried out according to the space truss displacement method, that is, the hinged rod system finite element method. The space frame structure can use simplified calculation methods such as the cross-beam differential analysis method and the pseudo-plate method to calculate the internal force and displacement. The nodes of single-layer shell-type space frames are generally assumed to be rigidly connected and should be calculated according to the finite element method of rigid-connected rods; double-shell space frames can be calculated according to the finite element method of hinged rods. Both single-layer and double-layer shell space frames can also use the pseudo-shell method to simplify calculations.

The bar design and node structure of the bar section of the space frame structure should be determined according to the strength and stability calculations. In order to reduce the calculated length of the compression rod and increase its stability, measures such as adding sub-rods and supporting rods can be adopted. The joints of the plate space frame and double-shell space frame made of steel mainly have three forms: cross plate joints, welded hollow spherical joints and bolted spherical joints.

The cross plate node is suitable for the space frame structure of the section steel rod. The connection of the rod and the point plate of the section space frame structure is connected by welding or high-strength bolts. Hollow ball joints and bolted ball joints are suitable for the space frame structure of steel pipe rods. The nodes of the single-layer shell-type space frame should be able to withstand bending internal forces. Generally, the steel consumption of the nodes accounts for 15-20% of the steel consumption of the entire steel space frame structure.

 

Gi——the representative value of the gravity load of the i-th node of the space frame;

Gk——the permanent load standard value of the space frame; 　

Gok——The standard value of the total dead weight of the space frame;

Gok——the standard value of the self-weight of the space frame;

He——post height;

H——the height of the space frame;

I——Simplified to the converted moment of inertia of the cross beam system;

Ke——The horizontal stiffness of the cantilever column;

Ab——the cross-sectional area of the lower chord of the space frame;

At——the cross-sectional area of ​​the upper chord of the space frame;

Am——the arithmetic mean value of the cross-sectional area of ​​the plane chord of the support (upper or lower bearing);

Aeff——the effective cross-sectional area of ​​high-strength bolts;

D——The converted bending stiffness of the space frame; the diameter of the steel ball;

D—— outer diameter of steel pipe;

D1, d2——the outer diameter of the steel pipe forming the angle θ; bolt diameter;

Ds——pin diameter;

E——The modulus of elasticity;

Ec——The elastic modulus of the column material;

FEK——the standard value of the total horizontal seismic action of the grid structure;

FEVKi——the standard value of vertical seismic action acting on the i-th node of the space frame;

Ft——Total starting traction;

Ft1, Ft2——The standard value of the pulling force of the lifting pulley block;

F——design value of steel strength; ——design value of tensile strength of high-strength bolts after heat treatment;

L1——The long span of the space frame;

L2——The short span of the space frame;

I——geometric length of rod;

M——Design value of bending moment of pseudo-sandwich plate;

Ηt——the coefficient of improving the bearing capacity of the hollow ball and ribs under tension;

Θ——The included angle between any two pipes converging on the ball joint; the small included angle between two bolts;

Μ1——The sliding friction coefficient;

μ2——Rolling friction coefficient;

ΡW——deflection coefficient; —dimensionless bending moment coefficient;

Φ——the angle between the oblique web rod and the lower chord plane;

Nb——The design value of the axial force of the lower chord of the space frame;

Nc——The design value of the axial force of the inclined rod of the space frame, the design value of the axial pressure of the compressed hollow ball;

Nt——The design value of the axial force of the upper chord of the grid, the design value of the axial tension of the hollow ball under tension; —The design value of the tension of the high-strength bolt;

NV——The design value of the axial force of the vertical rod of the space frame;

Qw——the standard value of roof load or floor load other than the self-weight of the space frame;

R1——The outer diameter of the roller;

R——The radius of the shaft;

S——the length of the upper and lower chords;

U——displacement;

Ω——Deflection;

Α——The linear expansion coefficient of the grid material;

Ηc——The coefficient of improving the bearing capacity of the ribbed hollow ball under pressure;

space frame