Axial behaviour of prestressed high strength steel tubular members

The axial behaviour and design of hot-finished high strength steel tubular elements with internal prestressing cables, representing the chord members in prestressed trusses, are examined in this paper. A comprehensive programme of experiments and numerical modelling was performed, the results of which were combined to develop resistance expressions for the design of prestressed high strength steel members. A total of 12 tensile and 10 compressive member tests were carried out, with the key variables examined being the steel grade (S460 and S690), the initial prestress level and the presence of grout. Numerical models were developed to replicate the structural response of the compressive member tests and subsequently used to generate parametric results, where the member slenderness, size of prestressing cable, applied prestress level, steel grade (S460 or S690), and grout condition (grouted and non-grouted), were varied. The presence of cables was shown to enhance the tensile capacity of the members, while the addition of prestress resulted in extended elastic range. In compression, the effect of prestress was detrimental, and a modified Perry-Robertson method, developed in [1], was extended to hot-finished high strength steel members.