Prestress losses in spruce timber

Abstract

Prestressing force and its change is one of the key factors that affect wooden constructions, especially those using methods of transverse prestressing. To achieve a description of a prestress force (P) in transversally prestressed wooden constructions a simulated experiment was done. Prestressing force, external temperature, and moisture were measured during 669 days. The main goal of this article was to model the primary losses of the prestress force at the spruce element of the 138 x 138 mm cross-section with the sensor installed. For this purpose, all measurements were statistically analyzed and the period of primary loss was found. During this period the prestress force was decreasing with time mainly and the influence of temperature and moisture could be omitted. Based on this analysis a mathematical model of losses of the prestress force was found as P = 8.538-0.014.day.

Influence of the External Environment on the Moisture Spectrum of Norway Spruce (Picea abies (L.) KARST.)

“…The experiment utilized a compact profile of Norway spruce (Picea abies (L.) KARST.) wood with cross-sectional dimensions of 138 mm × 138 mm and a length of 273 mm, as described in [10,27]. To determine the essential characteristics and ensure the quality of the timber, we measured its average density (oven-dry density) according to the ČSN 49 0108 standard.…”

“…Wood's excellent strength-to-weight ratio allows for efficient load-bearing capacities, while its cellular structure, consisting of lignocellulosic fibers, provides inherent strength and resilience against bending and compression forces [7][8][9][10][11]. Additionally, the unique fiber arrangement of wood enables it to resist lateral loads [12], making it suitable for constructing durable frameworks capable of withstanding various environmental conditions.…”

“…An excessive moisture content can lead to undesirable consequences, such as swelling, warping, and loss of strength, compromising the performance and longevity of wood-based products [8,[20][21][22]. Conversely, insufficient moisture content can result in shrinkage, cracking, and brittleness, further compromising the material's mechanical properties [8,10,20,23,24]. Therefore, understanding the intricate relationship between wood's moisture content and its mechanical behavior is vital for designing durable and reliable wood structures.…”

“…In the field of timber construction, our study builds upon the findings of two influential research papers. The first paper delved into the primary losses of prestressing force in spruce timber used in transversally prestressed wooden constructions [10]. For 669 days, a simulated experiment was conducted to measure prestressing force, external temperature, and moisture.…”