Dimensional behavior of nail-laminated timber-concrete composite caused by changes in ambient air, and correlation among temperature, relative humidity, and strain

Abstract

A timber-concrete composite (TCC) slab composed of nail-laminated timber (NLT) and topping concrete (TC) was developed for flooring applications. The NLT was laminated alternately with lumber and plywood. To investigate the nonstructural dimensional behavior of the TCC slab, the temperature, relative humidity (RH), and dimensional changes of the slab exposed to outdoor air were monitored for 205 days. Temperature change was transmitted directly to both components, and RH change was transmitted gradually to the NLT. Concrete pouring caused a sharp increase in NLT width, which was the laminating direction of the nails. This resulted from swelling of the wood owing to the moisture in the concrete mixture and loosening of the nail lamination. The member composition for the nail-laminating system, fastener type, and concrete volume help to secure the dimensional stability of the NLT. Cracks in the TC caused width deformation, which was recovered by drying shrinkage of the TC. Correlation analysis among temperature, RH, and strain indicated that dimensional changes in NLT correlated strongly with RH, while those in TC correlated strongly with temperature. The correlation between longitudinal strain in the TC and strain in the three directions of the NLT was attributed to the notches designed for mechanical connection.

Long-Term Behavior of Timber–Concrete Composite Structures: A Literature Review on Experimental and Numerical Investigations

“…Hwang et al [91] reported the moisture content (MC) of the NLT-concrete composite floor exposed to outdoor environments. It was found that the MC of NLT increased with the increase in the ambient RH and the pouring of wet concrete.…”

Investigation of NIR spectroscopy and electrical resistance-based approaches for moisture determination of logging residues and sweet sorghum

“…Three or more consecutive points within a distance of 0.1 from a data point are considered a cluster. Hwang et al (2023). "Moisture of biomass feedstocks," BioResources 18(1), 2064-2082.…”

“…As with the MC measurements, the increase in bulk density contributed to the creation of continuous paths for charge travel. Hwang et al (2023). "Moisture of biomass feedstocks," BioResources 18(1), 2064-2082.…”

“…Although the reliable range of moisture determination is limited, most portable commercial moisture meters for biomass are based on electrical resistance. Electrical methods must include control of wood species, internal stress, preservatives, and distance between electrodes for precise moisture determination of solid wood (Lahtela et al 2014;Dietsch et al 2015;Hwang et al 2023). However, to measure biomass moisture, the compression of the fine material to create the charge travel path must be considered first (Govett et al 2010).…”