Abstract
Behaviour of composite steel‐concrete elements in various loading stages is quite well analysed by theoretical investigations and experiments. Concrete‐Filled Steel Tube (CFST) is one of many composite elements used at present in civil engineering. Different approaches and design philosophies were adopted in different design codes for it. But for hollow CFST elements, which are more effective than ordinary CFST, any code does not provide information about how to design these elements. Further investigations of hollow composite CFST elements are needed. In loading stage, when a particular level of stresses exists, an interaction between steel tube and concrete core appears and therefore a complex stress state of element takes place, which increases the load‐bearing capacity of the whole composite element. This interaction between components of CFST elements is reached because of different material properties, such as Poisson's ratio, elasticity modulus etc. In this article reasons of the above‐mentioned complex stress state appearance and behaviour of hollow CFST element components in different load stages of compressed stub structural member are analysed. The test results are presented in diagrams, tables. Previous researches of other investigators are summarised. Differences and similarities in behaviour of solid concrete and composite elements and hollow members with different number of concrete core layers are discussed.
Highlights
Steel members have the advantages of high tensile strength and ductility, while concrete members may be advantageous in compressive strength and stiffness
It is considered that the steel tube becomes bi-axially and solid concrete core triaxially stressed [10, 11], but for the hollow Concrete-Filled Steel Tube (CFST) 3D
For the improvement that in hollow CFST elements during loading the stresses are redistributed in a complex way as mentioned above, there were manufactured and axially compressed specimens of annular cross-section: single- (1CFST) and double-layered (2CFST) CFST members (Fig 5c), single- (1CT) and double-layered (2CT) concrete members (Fig 5b) and empty steel tubes ST (Fig 5a)
Summary
Steel members have the advantages of high tensile strength and ductility, while concrete members may be advantageous in compressive strength and stiffness. Hollow CFTS members can be produced with a concentrically layered concrete core (double layered, triple layered etc) that increases the strength capacity of the whole member [2] These composite columns can be used for the resisting outside pressure, such as ocean waves, ice; in seismic regions because of excellent earthquake-resistant properties such as high strength, high ductility, and large energy absorption capacity. The Eurocode 4, being a dedicated code for composite construction, combined the design approach of both structural steelwork and reinforced concrete columns. All these codes provide a design procedure just for CFST, CES composite columns and any code does not mention hollow CFST elements.
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