The effect of adhesive type and ply number on the compressive strength retention of CLT at elevated temperatures

Abstract

This paper describes novel experiments to identify the reduction in compressive strength of crosslaminated timber (CLT) at elevated temperatures. The adhesive type and number of timber plies was varied between CLT samples to allow an assessment of the CLT 'system', rather than timber only. Samples were subjected to steady state and transient heating conditions and their ultimate load bearing capacities were measured. At ambient reference temperatures, a statistically significant difference in ultimate compressive strength was observed between ply numbers but not between adhesive types. For transiently heated samples, capacity was reduced at 100 °C for CLT bonded with polyurethane adhesive type as compared to samples bonded with melamine formaldehyde. The presented results indicate that the composition of CLT can influence the whole system structural response, both at ambient temperature and under fire conditions.

Probabilistic Models for Temperature-Dependent Compressive and Tensile Strengths of Timber

“…In fact, as concluded in a literature review conducted by Gerhards (1982) and in various subsequent works (Manríquez Figueroa et al 2015;Östman 1985;Wiesner et al 2021), moisture content has a strong influence on timber strength at high temperatures. However, the influence that other factors and their possible interactions might have on the variability of the experimental data remains uncertain.…”

“…Of the 30 studies selected from the literature review, 13 provided experimental data at elevated temperatures on timber compressive strength (Goodrich et al 2010;Kollmann 1940Kollmann , 1951Manríquez Figueroa et al 2015;Dias De Moraes 2010, 2016;Sulzberger 1953;Wiesner et al 2021;Young and Clancy 2001;Zaben et al 2020); 10 on timber tensile strength (Do and Springer 1983;Frangi et al 2012;Klippel et al 2014;Kollmann and Schulz 1944;Kuronen et al 2021;Lau and Barrett 1997;Manríquez Figueroa 2008;Nielsen and Olesen 1982;Östman 1985;White et al 1993;White 1996;Yue et al 2021;Zelinka et al 2019); and seven on both compressive and tensile strengths (Glos and Henrici 1990;Khmelidze 1986;Knudson and Schniewind 1975;Nyman 1980;Rykov 1980;Schaffer 1973Schaffer , 1984. According to the publications for which information was available, data were obtained from experimental tests performed on clear specimens (Knudson and Schniewind 1975;Kollmann 1940;Manríquez Figueroa 2008;Manríquez Figueroa et al 2015;Dias De Moraes 2010, 2016;Nyman 1980;Östman 1985;Schaffer 1973Schaffer , 1984…”

“…Except for the experimental tests conducted by Wiesner et al (2021) on cross-laminated timber (CLT) specimens, all experimental data collected come from solid timber specimens. As can be observed in Table 1, wood specimens of multiple densities, moisture contents, and dimensions were assumed in the different experimental tests.…”

“…Concerning the heating of the specimens, with the exception of the experimental tests carried out by Wiesner et al (2021), heating was carried out prior to loading and, hence, under unstressed conditions. The information collected shows that, in general, specimens reached steady-state conditions in the experimental tests conducted by the different authors; however, transient conditions were also assumed by several authors (Glos and Henrici 1990;White 1996;White et al 1993;Wiesner et al 2021).…”

“…Multiple published studies have provided experimental data on the reduction of timber strength at high temperatures. As indicated by Kuronen et al (2021), Manríquez Figueroa and Dias De Moraes (2016), Wiesner et al (2021), and Zaben et al (2020), this topic is of major concern, especially with the advent of mass timber construction. Recently, several sources have collated the experimental data reported in the literature (LaMalva and Hopkin 2021; Naser 2019), revealing a large variability among these.…”