In the past 30 years, various types of large-span steel structures have developed rapidly in developed countries and regions such as the United States, Japan, Europe, and Australia. Their spans and scales have become larger and larger, and the application of new materials and technologies has become more and more extensive. Lots of magnificent and characteristic large-span buildings have become symbolic or iconic cultural landscapes in local. Throughout the design and construction of these modern large-span steel structures, the main features are presented as follows.
picture1- large span steel structure
The modern large-span space steel structure is not limited to a traditional single structural form. New structural forms and various combined structural forms are constantly emerging. Let’s take some famous Chinese buildings as examples, the Water Cube adopts a polyhedral space rigid frame structure based on foam theory, the Bird's Nest uses a complex twisted space truss structure, the Olympic badminton hall uses the world's largest chord-supported dome structure, and the Guangzhou International Convention and Exhibition Center uses a truss string structure.
Due to the needs of architectural functions, the span of modern steel structures is getting larger and larger. For example, the Birds Nest’s span is 296m, the national swimming center’s span is 177m, and the Nanjing Olympic Sports Center stadium arch’s span is 360m. As a result, the National over-limit Expert review Committee specially compiled the provisions for over-limit review of large-span structures. These large span steel structures are made of a large amount of high strength grade steel such as Q390C, Q420C, Q460E, etc., and the thickness of the steel plates is very thick, and some even exceed 100mm.
As a new technology, prestress has been fully applied, and new structural forms such as cable domes, tensegrity structures and cable-membrane structures have emerged. The Olympic Badminton Stadium adopts the world's largest chord-supported dome structure. The National Gymnasium uses the world's largest two-way beam string structure.
Most modern steel structures adopt imitation ecological buildings, which adopts a variety of node forms to meet the architectural shape, such as cast steel nodes, forged steel nodes, and spherical hinge nodes.
Generally speaking, such large-scale projects are composed of tens of thousands of components, even more than 100,000 components, and the cross-sectional form, size and length of these components are different. This brings great difficulties for the construction team, and special tests and research are required to complete some bending and torsion members.
This kind of project belongs to the national key project with high project quality requirements. The quality could be reached by requirements only by improving the machining accuracy of components. And the requirement of first-class welds brings great difficulty to the construction.
In order to ensure construction accuracy, these projects need to be pre-assembled, and the welding workload on-site is particularly large. In order to ensure economy and safety, advanced construction techniques must be used to successfully complete the installation.