Assessment of a timber structure in the “Ermida da Ascensão de Cristo” in Lisbon

This paper presents the assessment of a timber structure in service and the aspects that should be consider for its proper development. To assess wooden structures is necessary to know not only the material and its characteristics but also the degradation agents to what can be subject and the appropriate inspection and diagnosis techniques for each case. The case presented in this work is the last floor structure of the "Ermida da Ascensão de Cristo", situated in Bairro Alto, Lisbon, Portugal. An inspection plan to the structure was followed which included several techniques of assessment namely visual inspection, moisture content determination and the use of semi-destructive devices to know the drill resistance and the penetration resistance of the wood. The use of traditional and non-traditional methods allowed the conjugation of information and obtaining results. A survey of the existent normalization was realized which allows the grading of the timber, in both qualitative and quantitative terms: grades and strength classes. The Portuguese standard NP 4305:1995 was followed in the measurement and assessment of only three grading rules: knots, slope of grain and rate of growth. The extension of the damage suffered by the structure due to the attack of wood boring insects was also evaluated, and was determined the loss of section. By the standard EN 338:2009, the characteristic values were determined, which, following the methodology of standard EN 1995:2004, allowed the evaluation of the structure behaviour to bending, deformation and shear. The use of standard NP 4305:1995 in a simplified way allows its adaptation to a timber structure in service, characterization and assessment in order to be able to determine solutions to its rehabilitation.