Combining NDT and visual strength grading to assess ancient timber beams stiffness to evaluate strengthening interventions suitability

Ancient timber beams strengthening is sometimes required by current safety standards, to sustain a safe working load or in order to reduce bending deflection. One of the fundamental information that structural engineers need to know to strengthen structural wooden elements is actual MOE. Through a settled procedure, outlined by a special Italian Standard (UNI 11119:2004) for the diagnosis of ancient timber members, mechanical properties can be assessed. The aim of this work is to evaluate if combining visual strength grading and NDT data might give a better MOE assessment. According to UNI 11119 all the grading characteristics values were recorded and 13 old timber beams of Fir wood (Abies alba Mill.) were graded. Beams were tested through Pilodyn 6J in order to assess wood density. Afterwards dynamic and static MOE values were respectively estimated by means of NDTs (longitudinal and bending vibration, stress wave transmission time) and mechanical tests. Possible MOE assessment improvements obtained combining data from visual strength grading and NDTs is showed.