Notched-beam creep of Douglas fir and white fir in outdoor conditions: Experimental study

Abstract

The impact of variations of relative humidity, temperature and moisture content on the creep of notched beams of Douglas fir and white fir are investigated. Indoor static 4-points bending tests are followed by outdoor creep tests of notched beams designed to trigger the breakage mode associated with the use of notched ends. The dimensions of wood specimens follow Eurocode requirements. The maximum load applied to outdoor creep tests is derived from the failure load obtained during indoor instantaneous tests. The results show that the variations of the relative humidity and temperature, coupled with the loading, play a key role in the lifetime of timber, as they accelerate its aging. In addition, the link between the changes of climatic parameters and the damage of the beams and the limit of their lifetime as structure is shown.

Analytical Assessment of Creep Behavior of European Species in Outdoor Conditions

“…Wood is defined as a material whose the mechanical behavior in structure depending on the fluctuation of its internal moisture content [1][2]. It is also known that the internal changes of humidity, coupling with long term loading bring in many times, the initiation and the propagation of cracks, which are directly an impact on the total deflection measured on the wood until its collapse [3][4]. These cracks are amplified by the geometric singularities available on the wood and are at the origin of the total collapse of the structure.…”

“…These cracks are amplified by the geometric singularities available on the wood and are at the origin of the total collapse of the structure. In this case, a specific experimental device has been built to assess the effects of moisture content in the mechanical behavior of wood [4]. The device takes, also into account, the effects of long term loading and the crack propagations.…”

“…The experimental campaign of creep loading is composed of two types of European species (Pseudotsuga Menziesii and Abies Alba Mil) tested as presented by [4]. During the experimental campaign the deflection of the notched beam, measured by LVDT sensor placed under the center of the beam, is considered as the principal parameter followed (Figure 1a).…”

Experimental assessment of the annual growth ring’s impact on the mechanical behavior of temperate and tropical species

“…Both tropical and temperate species are commonly used in structure for heavy and light frameworks, glulam, paper pulp, fiber panels, in cooperage, packaging, maritime work, and luxury furniture (Adamopoulos et al 2009;Treml and Jeske 2012;Sopushynskyy et al 2017). In France there were more than 170 Mm 3 of white fir and 93 Mm 3 of Douglas fir in 2009 (Pambou Nziengui et al 2019). The chosen tropical species are the most widespread species in the tropical forest of Gabon and also among the most exported and used species in the field of timber structures (Odounga et al 2018).…”

Moisture Monitoring Data of Mass Timber Elements During Prolonged Construction Exposure: The Case of the Forest Science Complex (Peavy Hall) at Oregon State University

“…Changes in the moisture content in the hygroscopic range (typically between 0 and 28%) affect nearly every physical and mechanical property of the material, from strength and stiffness to thermal conductivity, and physical dimensions (Glass and Zelinka, 2010). Importantly, mechano-sorptive effects imply reduced stiffness and increased viscoelastic and plastic deformation with higher moisture contents during loading (Holzer et al, 1989;Pambou Nziengui et al, 2019). When applied at the global scale, these changes can impact building tolerances and serviceability.…”