Design of Large Span Steel Structure Building (Part 1)

1、Development of large span steel structure buildings

As an important part of the large span steel structure, the space frame structure has been applied in my country since the 1960s. After decades of development, large, medium and small span space frame structures have spread all over the place. Take the Bird’s Nest of the 2008 Beijing Olympic Games as an example, which combines traditional Chinese culture with modern architecture. The amount of steel used in the Bird’s Nest reaches more than 90,000 tons.

Now,hybrid structures composed of two or more different steel structural forms are also being used more and more widely. Large span steel structures can be used not only for roof structures, but also for floor structures, wall structures and special structures. More and more enterprises in the automobile, machinery, chemical and other industries use large span steel structure design in their factory buildings.In addition, more and more public buildings also use large span steel structures. The introduction of modern prestressing technology into large span steel structure buildings can make the structure more abundant, more economical and reasonable.

2、Classification and characteristics of large span steel structures

Large span steel structures are mainly divided into space frame structure, truss structure and portal rigid frame. These types of steel structures will be discussed below.

2.1 Space frame structure

The space frame structure is a space structure formed by splicing multiple rods. It has the advantages of light weight, high rigidity and good seismic performance. From the appearance, we can divide it into double-layer plate-type space frame structure, single-layer and double-layer shell-type space frame structure. Among them, the rods used in the double-layer plate space frame and the double-layer shell type space frame are divided into three types: the upper chord, the lower chord of the space frame and the web rod. They mainly play the role of bearing tension and pressure; while the single-layer shell type The rods used in the space frame are not only subject to tension and pressure, but also bending moments and shearing forces. At present, most of the space frame structures in our country use double-layer panel space frame structures. From the perspective of composition, the space structure is mainly divided into the following three categories: one is a space frame composed of a plane truss system, which specifically includes two-way orthogonal upright placement, two-way orthogonal oblique placement, and two-axis oblique placement. Cross-oblique placement and three-way space frame; the second is the space frame composed of quadrangular pyramid units, which are specifically divided into positive quadrangular pyramid, positive evacuated quadrangular pyramid, oblique quadrangular pyramid, checkerboard-shaped quadrangular pyramid and star-shaped There are five types of quadrangular pyramids; the third is a space frame composed of triangular pyramid units, which can be divided into three forms: triangular pyramid, evacuated pyramid and honeycomb pyramid. The steel frame structure has a wide range of applications and can be used in the design of gymnasiums, waiting halls, industrial plants, theaters, exhibition halls and other buildings. But the fly in the ointment is that it uses a large number of rods and the construction is more complicated.

2.2 Truss structure

A truss is a truss beam, which is a latticed beam structure. Its structural arrangement is relatively flexible, and it can be applied in a very wide range. The flexural strength of the truss beam is relatively large, which can fully exert the strength of the material. In addition, it is more meaningful that it allows us to intuitively understand the distribution and transmission of forces, which facilitates structural changes and combinations. According to the shape of the truss, we can divide the truss mechanism into three types: parallel chord truss, folded chord truss and triangular truss. Among them, the parallel chord truss is conducive to the arrangement of double-layer structures and can be standardized production; the material of folded chord trusses is more economical, But the structure is complicated; the triangular trusses are helpful for the drainage of the roof, but the distribution of the rod force is not uniform, and the structural arrangement is difficult. From the perspective of truss geometric composition, truss structures can be divided into three types: simple truss, complex truss and joint truss. In addition, it can be divided into two categories according to whether it is subject to horizontal thrust: beam truss without thrust and arch truss with thrust. The non-thrust beam truss chord is not easy to bend, the force is more reasonable and the material is economical; the arch truss with thrust has better integrity of the arch ring and the upper structure of the arch, the construction is easier, and the spanning ability is strong. relatively economical. Truss structures are often used in public buildings such as large span workshops, gymnasiums, and bridges.

2.3 Portal frame structure

Portal frame structure is a relatively traditional structural system, and its upper main frame mainly includes rigid frame inclined beams, supports, purlins, tie rods, etc. It has a series of characteristics such as simple force bearing, clear force transmission direction, easy production, easy processing, short construction period, sturdy and durable structure, high quality and low price, and obvious economic benefits. Due to the above characteristics, the portal frame structure is widely used in civil buildings such as industrial plants, cultural and entertainment public facilities, and private supermarkets.