Effect of slenderness on the performance of steel-reinforced glulam radiata pine timber columns: Experimental evaluation

Recent years have seen the implementation of mass timber as a structural system for buildings. However, meeting the structural demands for tall columns and long-span beams poses a challenge for mass-timber systems, with their required sizes becoming prohibitive. To meet this challenge, the hybridisation of such elements with internal steel bar reinforcement has been shown to significantly increase their strength and stiffness. Understanding the effect of slenderness on the behaviour of such hybrid columns is of prime importance to enable designers to maximise the benefits of the steel reinforcement in hybrid timber–steel encased columns. This paper systematically investigates this via a comprehensive testing program including 85 Radiata pine ( Pinus radiata ) column specimens of varying slenderness, section size and reinforcing ratio. The key contributions of this work are threefold: (i) The impact of hybrid columns’ slenderness on the peak loads, failure modes and buckling behaviour, and the effectiveness of the steel reinforcement in each configuration are elucidated; (ii) Suitability of current buckling curves and provisions in design standards from Australia (AS1720.1), Europe (Eurocode 5 - EN1995-1-1), and America (NDS) are assessed against the obtained test results, and conclusions are drawn; (iii) An analytical model is proposed to take into account the steel reinforcement in calculation of slenderness for AS1720.1, EN1995-1-1 and NDS. The investigation found that current buckling curves in these design codes are conservative for high slenderness hybrid columns but overestimate the peak load of intermediate slenderness hybrid columns. • Behaviour of steel-reinforced glued laminated timber column is experimentally studied • Influence of slenderness on the load carrying capacity of the columns is critically evaluated • Change in variability of peak load and failure modes due to steel reinforcement is discussed • Application of current timber codes for design of reinforced timber columns is assessed.