## 2 Experimental Procedure  
A total of 24 pieces of wood have been compression tested to breaking point. Of those pieces, 18 were reinforced through confinement using three kinds of FRP fabric attached to the exterior using epoxy resins. Carbon fiber fabric and two basalt fiber fabrics featuring the same mechanical characteristics but with very different grammage were used. Six pieces were tested without reinforcement in order to serve as a benchmark. To able to identify the pieces of wood, a PAB\(\beta\gamma\delta\) type code was used, where P remains constant in all of the test pieces; AB indicates the reinforcement status and type, WR is used for test pieces without reinforcement, FB is used for test pieces reinforced with basalt fiber, and FC is used for test pieces reinforced with carbon fiber; and \(\beta\gamma\delta\) is, in the reinforced test pieces, the grammage of the fabric in g/m\({}^{2}\). In order to carry out the tests, wild pinewood was used from Valsain, in the Sierra de Guadarrama region (Spain). This type of wood was used in many of the pillars in existing buildings in Spain constructed up to the beginning of the 20 th century. Before reinforcing and testing the wooden elements, a visual classification was performed in line with regulation UNE 56544 [67] so as to have prior knowledge of the individual characteristics of each of the pieces and check that the sample composed of the 24 pieces was homogeneous. In order to carry out this classification, and as specified in the regulation, the following characteristics were observed and measured: density, size of the knots and the cracks, and angle of inclination of the fibers. All of the pieces feature knots on one of their faces, and they have thick cracks and contain the pith. None of the pieces feature ring shakes, resin ducts, ingrown bark, gems, or biological changes of any kind. Three types of fabric were used to reinforce the pieces--two composed of basalt fiber and the third composed of carbon fiber. The grammage of the carbon fiber fabric is 300 gr/m\({}^{2}\), while the basalt fiber fabrics have two different grammages, 280 gr/m\({}^{2}\) and 600 gr/m\({}^{2}\). All of the fabrics are unidirectional with the fibers pointing in a longitudinal direction. In order to join the fabrics to the pieces of wood, epoxy resin was used, having previously applied a primer so as to improve the adhesion between the reinforcement and the surface of the wood. Table 1 shows the geometrical and mechanical characteristics of the different fabrics used, where G is the grammage, t is the thickness, \(\sigma_{\text{f}}\) is the ultimate tensile strength of the fibers, E\({}_{\text{f}}\) their modulus of elasticity, F\({}_{\text{f}}\) the breaking strength that the fabric is capable of reaching per unit of length, and K\({}_{\text{f}}\) the rigidity of the fabric per unit of length. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & **G (g/m\({}^{2}\))** & **t (mm)** & \(\sigma_{\text{f}}\) **(N/mm\({}^{2}\))** & **E\({}_{\text{f}}\) (GPa)** & **F\({}_{\text{f}}\) (N/mm)** & **K\({}_{\text{f}}\) (N/mm)** \\ \hline FC300 & 300 & 0.167 & 4900 & 230 & 818 & 38,410 \\ FB280 & 280 & 0.103 & 4000 & 84 & 412 & 8652 \\ FB600 & 600 & 0.222 & 4000 & 84 & 888 & 18,648 \\ \hline \end{tabular}
\end{table} 
Table 1: Geometrical and mechanical characteristics of the fabrics used. Overall, 24 wooden pieces with a cross section measuring 158 mm \(\times\) 158 mm and a height of 300 mm were tested to compression until breaking point. Prior to being tested, the pieces were kept in laboratory conditions (a temperature of 21 \({}^{\circ}\)C and relative humidity of 55%) until a constant weight was obtained in the test pieces, with the pieces reaching an average humidity content of 19% at that point. Tests were performed on six unreinforced pieces (PWR), six pieces reinforced with 600 g/m\({}^{2}\) basalt fiber (PFB600), six pieces reinforced with 280 g/m\({}^{2}\) basalt fiber (PFB280), and six pieces reinforced with carbon fiber (PFC300).