Post-tensioning of glulam timber with steel tendons

•Four-point bending of reinforced and post-tensioned glulam timber with steel tendons.•Strength and stiffness increased for reinforced timber compared to unreinforced.•Strength and stiffness further increased for post-tensioned compared to reinforced.•Active reinforcement offers additional benefits over the commonly used passive form.•Preliminary long-term tests show no excessive losses in post-tensioning force. This paper describes a series of four-point bending tests that were conducted, under service loads and to failure, on unreinforced, reinforced and post-tensioned glulam timber beams, where the reinforcing tendon used was 12mm diameter toughened steel bar. The research was designed to evaluate the benefits offered by including an active reinforcement in contrast to the passive reinforcement typically used within timber strengthening works, in addition to establishing the effect that bonding the reinforcing tendon has on the materials performance. The laboratory investigations established that the flexural strength and stiffness increased for both the reinforced and post-tensioned timbers compared to the unreinforced beams. The flexural strength of the reinforced timber increased by 29.4%, while the stiffness increased by 28.1%. Timber that was post-tensioned with an unbonded steel tendon showed a flexural strength increase of 17.6% and an increase in stiffness of 8.1%. Post-tensioned beams with a bonded steel tendon showed increases in flexural strength and stiffness of 40.1% and 30% respectively.