Bending capacity of composite strengthened timber columns

This study investigated the seismic performance of timber columns reinforced with embedded steel bars and an externally bonded carbon fibre reinforced polymer (CFRP) fabric. Ten circular and rectangular timber column specimens were tested under a low-cycle reverse cyclic loading applied at a height of 1770 mm and a constant axial pressure of 43 kN to evaluate their lateral behaviour. The composite strengthened timber columns included circular columns with a diameter of 300 mm and rectangular columns with a cross-sectional dimension of 270 mm × 270 mm and all with a height of 2600 mm. The specimens exhibited different internal reinforcement configurations and CFRP reinforcement levels. Experimental results show that the composite strengthened method significantly increased the peak lateral load-carrying capacity by up to 60.4 %, improved ductility, and increased energy dissipation compared to those of the unreinforced columns. The specimens with full CFRP cladding and optimized reinforcement configurations exhibited best overall performance, with ultimate displacements of up to 180.1 mm. Additionally, a theoretical method for predicting the transverse load capacity based on strain compatibility and cross-section analysis was developed, and the predicted transverse load capacity shows good agreement with the experimental results within ± 22.0 %, validating the accuracy of the analytical model. These results confirm the effectiveness of combined internal steel and external CFRP reinforcement in improving the seismic performance of timber columns and provide a reliable analytical method for the engineering design of composite strengthened timber structures for seismic applications.