On the use of prestress for structural strengthening of timber beams: assessment with numerical support and experimental validation

The use of prestress for the structural strengthening of timber elements is not new and has been used before to increase the load capacity and ductility of timber beams. The work presented herein aims to develop, analyze, and test possible strengthening solutions to be applied on common structures and compare them with more the traditional ones (e.g., prestress cables). For this purpose, three different strengthening solutions were tested with the application of prestress by making use of (i) steel plates, (ii) steel rebars, and (iii) steel cables. All systems were previously modeled with finite elements with the objective of predicting the experiments that could help in the design of the strengthening elements as well as to quantify the prestress forces to be applied, taking into account allowable stress levels in the wood. The work performed allowed for the conclusion that the numerical analysis carried out to support the design of the experiments was crucial for the success of the research. Moreover, the overall objectives were achieved: increase of the load-carrying capacity at rupture (up to 286%) as well as for serviceability limit states (up to 886%). Finally, the structural strengthening systems proposed were effective in preventing fragile failure modes.