Experimental study and numerical analysis of composite strengthened timber columns under lateral cyclic loading

To develop a new composite material column for modern timber buildings and propose a reliable strengthening method for existing timber columns, wrapped carbon fiber reinforced polymer (CFRP) strips and near-surface mounted (NSM) steel bars reinforced timber columns were studied. Five composite strengthened timber columns were designed, fabricated and tested under lateral cyclic loading. The experimental results showed that all specimens exhibited tensile rupture failure of the timber grain. The hysteretic curves showed that the proposed method could enhance the load-bearing capacity and deformation performance of the strengthened timber columns. With an increase in the number of CFRP strips, there was a marked improvement in the hysteretic performance of the specimens. Based on the experimental study, a finite element model of a composite strengthened timber column was developed using the OpenSees software application, the reliability of which was evident from the test results. A parametric study was then conducted to investigate the influence of the axial load, bar diameter, and the number and location of steel bars. This study aimed to provide a reference for seismic design and the practical application of the composite reinforcement method.