PSI - Issue 55

Dulce Franco Henriques et al. / Procedia Structural Integrity 55 (2024) 214–221 Henriques et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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3. Case Study: Inspection and assessment of a floor structure beam A campaign was carried out to apply the principles of inspection in situ to an ancient building. The building, originally built at the last quarter of the 19 th century, made of masonry and pine wood (Pinus spp.), is located in the historic center of Lisbon. The evaluation of beam V1 (Fig. 2), which is part of a floor, involved the following test methods: • Survey of the wood member's moisture content. • Identification of the geometric conditions and state of conservation of the structural members. • Characterization of surface hardness of structural members with penetration resistance tests. • Extraction of cores for laboratory study. • Grading of some representative beams using the VSG methods. 3.1. Physical and mechanical characterization 3.1.1. By visual inspection Beam V1 comprises part of the second floor of the building. Visual analysis identified two critical sections SC1 and SC2 (Fig. 2 (b)), which can be defined as having a combination of knots and being close to the mid-span, i.e., in areas with high stress levels (Cruz et al., 2015). The inspection was carried out as follow: the visual analysis showed that both the beam and the adjacent ones were of poor quality, poorly squared and very irregularly cut, with several occurrences of single or double wane, combination of knots, fissures, and woodworm or wood boring beetle damage. The dimensions of beam V1 were surveyed (Fig. 2 (a)), and it was found that the cross-section varied considerably along its length. Fig. 2 (c) shows the beam in profile, highlighting the double wane. As for the beam water content, seven measurements were taken, of which the highest and lowest were rejected. Measurements showed that the wood was perfectly dry. There were also no signs of high moisture in the wood in the past. Possible signs of degradation by biological agents have been looked for. No degradation by subterranean termites or rot fungi was detected. However, there were signs of xylophagous beetle infestation quite intensely on the edges and face of the beam. It is known that this type of degradation is limited to sapwood in pinus spp species (EN 350:2016) and is generally superficial in the wooden element. This was confirmed by the tests carried out, so a continuous strip of around 1 to 2 cm on both the edges and the face could be considered useless. On the other hand, the strong blurring, usually double, reducing the dimensions of the edge and face to less than 2/3 of the dimensions of the piece, also means that only part of the section was useful. Thus, deducting the effect of biological degradation and shrinkage from the section, an effective (residual) cross-section of 8.5 x 13 cm was obtained for beam V1, as shown in Fig. 2 (a). It is worth noting the presence of cracks, generally radial and visible from the lower edge. These cracks did not run through the thickness and were between 1.0 and 1.5 m long.

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Fig. 2. (a) Beam cross-section; (b) The floor and beam V1 with critical cross-sections; (c) Beam V1 in the zone of critical cross-section 2.