Compressive behaviour and design of prestressed steel elements

Abstract

The tensile performance of the chords of steel trusses can be considerably enhanced through the addition of prestressed cables. However, under compression, which may arise due to wind uplift, the prestressing may have a detrimental effect. The behaviour and design of prestressed steel elements in compression is examined presently. Eight experiments on prestressed elements were carried out, where the key variables examined were the initial prestress level, the presence of grout and the member slenderness. Cross-sectional behaviour and member buckling behaviour are examined analytically, numerically and experimentally, with good correlation achieved between the three approaches. The benefit of adding grout to bond the prestressing steel to the encasing tube is also investigated and design approaches for both non-grouted and grouted prestressed elements are proposed.

Axial behaviour of prestressed high strength steel tubular members

“…Prestressing was found to reduce the compressive resistance of the system, but the reduction in strength was shown to be much less than the applied prestress due to the absence of second order bending moments. FE models, validated against the experiments, were employed in order to generate parametric results for the assessment of a modified Perry-Robertson design method [4]. Buckling curve a 0 adopted in EC3 [8] was shown to yield some unsafe predictions for the S460 0.5P opt and P opt members, but was safely applicable to the S690 members.…”

“…The design of cable-in-tube systems under compression has been studied in Gosaye et al [4], where a method based on the Perry-Robertson approach [7] for conventional column design was developed, and termed the modified Perry-Roberston approach. The method employs the same framework as Eurocode 3 [8] for column design, but accounts for the prestressing cables and grout, as expressed in Eqs (2)- (7), where the symbols are consistent with those used in Eurocode 3 [8].…”

“…(7) is the buckling resistance of the steel tube), the cable will slacken before the member fails, hence the design is equivalent to the case without prestressing, which leads to P i = 0 and k  = 1in Eqs (4) and (5). , respectively, to assess the design curves determined from the modified PerryRobertson approach [4]. In general, this approach can provide a good estimation of the compressive resistance of cable-in-tube systems.…”

“…Cable-in-tube systems, whereby the steel cables are housed within hollow structural sections, are one way to achieve these structural forms. The performance of cable-in-tube systems in normal strength steelwork has been studied in [3,4]. This paper focuses on the behaviour of such systems in high strength steels (HSS).…”

Prestressed cold-formed steel beams: Concept and mechanical behaviour

“…However, while in the case of concrete structures the aim is to impose compressive stresses on parts of the cross-section to overcome the intrinsically weak tensile performance and thus prevent cracking, in the proposed prestressed cold-formed steel beams, the purpose is to enhance the performance of the members by applying tensile stresses on parts of the cross-section that are prone to instability. Previous research studies on prestressed steel structures focused on the application of prestress to hot-rolled steel elements, including bare steel beams [2,3,4,5], composite beams [6,7,8,9,10,11,12], steel trusses [1,13,14], tubular members [15,16,17], stayed columns [18,19,20,21,22] and steel arches [23,24]; considerable enhancements in load-carrying capacities and reductions in deflections of these members and systems have been reported.…”