Experimental study for non-destructive mechanical evaluation of ancient chestnut timber

Abstract

The paper deals with an experimental study for in situ mechanical characterization of ancient timber members using combined Non Destructive Testing (NDT) techniques. An experimental campaign, including non-destructive and destructive tests, was developed on timber structural elements and defect-free specimens, made of old chestnut wood (Castanea sativa Mill.). The following NDT methods were employed in the research activity: hygrometric tests to estimate wood moisture content; ultrasonic investigations to determine stress wave properties; sclerometric tests to assess material hardness and superficial consistence; resistographic measurements to detect internal defects and density variations. Destructive tests in compression parallel to grain and in bending were performed to assess stiffness and strength properties, post-elastic behaviour and collapse mechanisms of the timber elements. Experimental results are discussed and statistically analyzed. Correlations between non-destructive and destructive parameters are provided, based on linear regression models, for the prediction of the wood density, strength and modulus of elasticity of the tested old chestnut timber. The analysis shows that the use of NDT techniques is a useful supplement to the traditional visual grading, allowing a reliable mechanical identification of timber members in practical applications, leading to the appraisal of the timber structures safety and integrity.