Selection of space frame structure (I)

 Factors affecting the selection of space frames mainly include space frame production, installation methods, steel indicators, span size, stiffness requirements, plane shape, support conditions, and so on.

space frame

1、If the nodes are welded, the space frame composed of a plane truss system is more convenient to make than the space frame composed of the quadrangular cone; the two-way orthogonal space frame is more convenient than the two-way diagonal space frame, and three-way space frame; the quadrangular cone space frame is more convenient than the triangular cone space frame.

2, when the installation method of the space frame is not used as a whole lift or hoisting, but the use of strip or block installation, or the use of high-altitude skidding method, the choice of the two-way orthogonal orthogonal space frame, orthogonal orthogonal cone space frame, orthogonal orthogonal four-cone space frame, four-cone space frame and other three types of orthogonal orthogonal space frame than the choice of inclined to put the kind of space frame is advantageous. The latter is slitting or block lifting, often due to insufficient rigidity or geometric variability and to set up additional temporary support, which is not cost-effective.

3, the space frame itself with steel index is an important symbol to measure the selection of space frame. Such as peripheral support and the plane close to the square space frame, through the full stress optimization design comparison, diagonally placed quadrangular cone space frame, and checkerboard-shaped quadrangular cone space frame steel consumption is more provincial. Because of these two kinds of space frame of the upper chord mesh is small, the rod is short, compression rod stability calculation cross-section folding reduction, and material utilization rate is high; The lower chord mesh is large, the tensile rod is long, the number of nodes and rods is small, so the steel consumption is provincial. If the side length ratio is greater than 1.5, due to the distribution of internal forces, the orthogonal orthogonal space frame in the same conditions as the diagonal put class space frame of steel saves some. Some of the pumping angle cone space frame of the amount of steel is generally more than not pumping cone space frame to save; but pumping angle cone space frame of the rod internal force than not pumping when the magnitude of change is large, on the node design and selection of rod is unfavorable.

4, the calculation shows that the size of the span (for network structure, more than 60m can be called a large span, 30m can be called a small spanand, 30 ~ 60m for a medium span) on the space frame selection of the impact is not great. However, the large-span frame is generally an important building. At present, in our country, we use more two-way orthotropic frames, two-way orthotropic diagonal frames three-way frames, and other kinds of plane trusses to form the frame structure. Because the design and construction experience of these large-span space frames is rich and the technology is skillful, three-way space frames, triangular cone space frames, and hexagonal cone space frames are generally more complicated in structure and use a large amount of steel, so it is better to be used in small and medium-sized spans.