Abstract
Temperature in timber roof trusses structures can reach 60°C and significantly affect wood strength, compromising the structural mechanical performance. This study aimed at quantifying the influence of exposure time to the mentioned temperature in wood strength by monitoring shear parallel to grain ( f v0 ) of Pinus taeda and Pinus elliottii from planted forests. Exposure times at 60°C, in controlled oven, consisted of zero, 168, 456 and 720 hours. ANOVA results indicated that temperature (60°C) influences significantly, in the four exposure times, f v0 for both Pinus wood species. For Pinus taeda , slightly more resinous, strength in shear parallel to grain presented successive reductions, related to reference condition (zero hour) for exposure times 168 and 456 hours; and increase for 456 hours to 720 hours. Different behavior was observed for Pinus elliottii , where f v0 successively showed increases from reference condition for the other temperatures. Even with varied behavior of Pinus wood referring to the influence of exposure times at temperature 60°C, shear strength was significantly affected.
Highlights
Timber is a renewable material, of expressive abundance, based on premises of reforestation policies and forest management adopted nowadays
This study evaluated strength in shear parallel to the grain of the species Pinus elliottii and Pinus taeda subject to heat treatment, time variation in kiln at 60oC, to assess if the influence of temperature and exposure time significantly affect wood strength
Pieces of Pinus elliottii and Pinus taeda, from where specimens were taken in experimental procedures, were properly stored in the dependencies of LaMEM (Wood and Timber Structures Laboratory) of the Department of Structural Engineering (SET), São Carlos Engineering School (EESC), University of São Paulo (USP)
Summary
Timber is a renewable material, of expressive abundance, based on premises of reforestation policies and forest management adopted nowadays. It has considerable value as a raw material in building industry, applied in several components, as well as structural parts, due to its good relationship between strength and density (Kollmann & Côté, 1968; Hodousek, 2017; Osuji & Nwankwo, 2017). Using wood for structures requires knowledge of its physical and mechanical properties, as they interfere in design (Bodig & Jayne, 1982, Güntekin & Aydin, 2016). It can be mentioned shear parallel to grain (whose rupture is fragile), present in the vast majority of structures, especially on connections by notches and/or metal. Technology, v. 40, e30913, 2018 pins (nails, screws and bolts) in roof trusses (Green et al, 1999)
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