Theoretical models for T-stubs in contact with intermediate layer. (May 2022)

• Record Type: Journal Article
• Authors: Couchaux, M.; Madhouni, M.
• Is Part Of: Journal of constructional steel research. Volume 192(2022)
• Publication Date: 2022-05
• Subjects: T-stubs -- Prying effect -- Thermal break; Steel, Structural -- Periodicals; Building, Iron and steel -- Periodicals; Acier de construction -- Périodiques; Construction métallique -- Périodiques; 624.1821
• DOI: 10.1016/j.jcsr.2022.107158
• Languages: English
• ISSNs: 0143-974X

Abstract

Abstract: During the last decade, simple solutions of thermal breaks have been developed for steel structures that consist in inserting an intermediate insulating layer (composed of PVC, plywood, elastomer, FRP…) between a bolted end-plate and a steel/concrete support. Experimental tests highlighted that failure modes under bending moment are similar to that of conventional bolted connections particularly in the tensile area, whereas the ultimate resistance decreases. For standard bolted connections loaded by a bending moment, the T-stub concept is used to model the tensile area. This model, extensively used in Eurocode 3, assumes that the end-plate is in contact with a rigid foundation or concrete/grout. T-stub can potentially be used to model the tensile area of bolted connections in presence of intermediate insulating layer. However the current model cannot be directly applied as the end-plate rests on a flexible support. In the present paper, a mechanical model is proposed to firstly model the elastic behaviour of T-stubs in contact with a flexible intermediate layer. The model relies on the Timoshenko beam theory in contact with a Winkler foundation modelling respectively the end-plate and the intermediate layer. The contact pressure distribution being almost linear, simplifications are proposed in this sense. It is demonstrated that simplifications can be considered for standard material used as intermediate layer such as PVC or FRP. An analytical model is also given to calculate the ultimate resistance of T-stubs considering yielding of the intermediate layer. These results are validated by comparison to finite element analysis results performed with ANSYS code using solid and contact elements. This FE analysis highlights a clear distinction between the elastic and elasto-plastic behaviors of these T-stubs particularly concerning prying effects. Highlights: Elastic and ultimate models for T-stub in contact with an intermediate layer Linear contact pressure distribution for the elastic range of behaviour Significant modification of prying effect for flexible layer after yielding