Effects of Variable Climate Conditions on the Behavior of Post-Tensioned Mass Timber Wall Panels (original) (raw)
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The use of cross-laminated timber panels (CLT) made of low-grade structural timber has steadily increased in developing countries. These panels usually present several natural defects, which can cause a high local variation of their orthotropic elastic properties, generating future structural serviceability problems. Our work aims to estimate the local variability of the elastic properties in low-grade CLT panels by combining nondestructive transverse vibration testing, numerical simulations, and regional sensitivity analysis (RSA). Four three-layer Radiata pine CLT panels were subjected to transverse vibration tests with supports at four points. Besides, a series of numerical simulations of the panels, considering the local variability of the elastic properties of the panels in eight zones, were carried out using the finite element method. Then, RSA analysis was performed to study in which ranges of values the panels’ elastic properties generated lower differences between the measu...
Behaviour of Cross-Laminated Timber Panels under Cyclic Loads
Materials and Joints in Timber Structures, 2014
In this paper, the behaviour of cross-lam (CLT) wall systems under cyclic loads is examined. Experimental investigations of single walls and adjacent wall panels (coupled walls) in terms of cyclic behaviour under lateral loading carried out ìn Italy at IVALSA Trees and Timber Institute and in Canada at FPInnovations are presented. Different classifications of the global behaviour of CLT wall systems are introduced. Typical failure mechanisms are discussed and provisions for a proper CLT wall seismic design are given. The influences of different types of global behaviour on mechanical properties and energy dissipation of the CLT wall systems are critically discussed. The outcomes of this experimental study provides better understanding of the seismic behaviour and energy dissipation capacities of CLT wall systems.
Effect of Temperature and Relative Humidity on Creep Deflection for Permanent Wood Foundation Panels
CSCE 3rd Specialty Conference on Material Engineering & Applied Mechanics, 2013
The structural insulated panel is an engineered composite product composed of an insulating foam core sandwiched to provide the insulation and rigidity, and two face-skin materials to provide durability and strength. SIPs can also be used as permanent wood foundation (PWF) for basements in low-rise residential construction to save in the energy cost. The maximum deflection equation specified in the Canadian Standard for Engineering Design of Wood, CAN/CSA-O86.09 specifies expressions for the effects of short-term bending deflection on the PWF timber stud walls. Information on the long-term creep behavior of SIPs under sustained triangular loading, simulating soil pressure, including effect of the change in ambient temperature and relative humidity is as yet unavailable. The long-term creep deflection for permanent wood foundation panels that is characterized as viscoelastic materials is highly affected by the change in ambient temperature and relative humidity. This paper reported the results from flexural creep experiments performed on two sets of different sizes of PWF made of structural-insulated foam-timber panels. In these tests, deflection, temperature and relative humidity were tracked for an eight-month period. The experimental findings were examined against existing creep models in the literature. Then, a creep model incorporating the effects of temperature and relative humidity on creep deflection was developed. Correlation between the proposed model and the experimental findings provides confidence of using the proposed model in the determination of the capacity of the PWF under combined gravity loading and sustained soil pressure.
Stress-wave velocity of wood-based panels: Effect of moisture, product type, and material direction
2006
The effect of moisture on longitudinal stress-wave veloc ity (SWV), bending stiffness. and bending strength of com mercial oriented strandboard, plywood. particleboard. and southern pine lumber was evaluated. It was shown that the stress-wave verocity decreased in general with increases in panel moisture content (MC). At a given MC level. SWV var ied with panel type and test directions. Regression equations relating SWV to MC and bending properties (modulus of elas ticity [MOE] and modulus of rupture [MOR]) were estab lished for various products. Both MOE and MOR at different MCs can be estimated by observing the speed of propagation of a longitudinal wave. This information is useful for devel oping moisture correction factors on the stress-wave related properties for wood-based panel products.
2011
A Permanent Wood Foundation (PWF) is a panel composed of expanded polystyrene insulation and preserved stud cores laminated between oriented-strand boards and preserved plywood. This thesis presents the experimental testing on selected PWFs' sizes to investigate their long-term creep behaviour under sustained soil pressure. The long-term creep tests were performed over eight months, followed by loading the tested panels to destruction to determine their axial compressive strength. The ultimate load test results showed that the structural qualification of PWF is "as good as" the structural capacity of the conventional wood-frame buildings. The obtained experimental ultimate compressive resistance and flexural resistance, along with the developed long-term creep deflection of the wall under lateral soil pressure can be used in the available Canadian Wood Council (CWC) force-moment interaction equation to establish design tables of such wall panels under gravity loading and soil pressure.
Laboratory and Field Exposures of FRT Plywood: Part 2�MECHANICAL PROPERTIES1
2010
Our understanding of how to interpret the laboratory-induced degradation data to real-world in-service performance of fire-retardant (FR) systems is currently limited because we are unable to correlate laboratory steady-state experiments with actual in-service field performance. Current model studies have generally been limited to isothermal rate studies with selected model FR chemicals. Other factors also play a major role in the degradation of FR-treated wood. These factors, which have not been studied in any detail, include RH/MC cycles and thermally induced evolution of ammonia from ammonium phosphates to provide phosphoric acid. Because there exists no known direct comparison of matched samples with one exposed to high-temperature laboratory conditions and the other exposed for an extended period of time as traditionally used in North American light-framed construction, the objective of this study was to determine the relationship for FR model compounds between laboratory and field results based on strength-temperature-RH (MC)-FR chemical interactions. The impact of the variables was evaluated by measuring bending strength properties and comparing matched laboratory and field exposure samples. The physical test data show the positive effects of adding a buffering system to model FR compounds when exposed to high moisture environments and the negative effects of increasing the moisture in the in-service environment during exposure.
The First International Symposium on Jointless & Sustainable Bridges
The structural insulated panel (SIP) is a sandwich structured composite that is prefabricated by attaching a lightweight thick core made of Expanded Polystyrene (EPS) foam laminated between two thin, and stiff face skins made of Oriented Strand Board (OSB). The use of sandwich panels provides key benefits over conventional materials including: very low weight; high stiffness; durability and; production and construction cost savings. The facing skins of the sandwich panel can be considered as the flanges for the I-beam carrying bending stresses in which one face skin is subjected to tension, and the other is in compression. The core resists the shear loads and stabilizes the skin faces together giving uniformly stiffened panel. OSB is wood product that shrinks when dry and swells when adsorb moisture either due to liquid or vapor from the surrounding atmosphere. The relative combination of relative humidity and temperature is introduced into the equilibrium moisture content (EMC) that increases with the increase of the relative humidity and with decreasing temperature. Experimental test matrix includes testing 2.44 m (8’) and 4.88 m (16’) long SIPs for 5 years under different sustained loads and weather resistive barriers (WRBs), recording creep deflection, relative humidity and temperature. After creep recovery, the SIPs are loaded to-collapse to determine their flexural strength.
Creep Behavior of Structural Insulated Panels (SIPS): Results from a Pilot Study
2014
This publication is also available online at www.fpl.fs.fed.us. Laboratory publications are sent to hundreds of libraries in the United States and elsewhere. The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. The use of trade or firm names in this publication is for reader information and does not imply endorsement by the United States Department of Agriculture (USDA) of any product or service. The USDA prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.
2010
A Stressed-Skinned Structural made of a wood-composite panel with foam insulation core laminated between two oriented-strand boards of 7/16” thickness , are called Structural Insulated Panel if OSB are in both faces, and Permanent Wood Foundation if one face contains preserved Plywood of 5/8” thickness, SIPs /PWF Foundation SIPs deliver building efficiencies by replacing several components of traditional residential and commercial construction. ..... Two PWFs sizes were considered in this study, 9’ and 10’ height, respectively, with 4’ width and approx ± 230 mm thick. The experiment study performed in a manner to comply with applicable ASTM test methods and Canadian Codes for Limit State Design. It should be noted that the long-term creep tests were performed over a nine months, followed by loading the tested panels to destruction. The long-term creep test results established the increase in panel total deflection with time. The long-term creep test results led to an empirical creep constant that can be used to obtain the long-term deflection over a specified period of time. The ultimate load test results showed that the structural qualification of PWF is “as good as” the structural capacity of the conventional wood-frame buildings. The obtained experimental ultimate compressive loading as well as the long term deflection of the wall under lateral soil pressure / Equivalent Fluid Pressure (EFP) will be used in the force-moment interaction equation to establish the design tables of such wall panels under gravity loading and soil pressure.
2016
The structural insulated panel (SIP) is a sandwich structured composite that is prefabricated by attaching a lightweight thick core made of Expanded Polystyrene (EPS) foam laminated between two thin, and stiff face skins made of Oriented Strand Board (OSB). The use of sandwich panels provides key benefits over conventional materials including: very low weight; high stiffness; durability and; production and construction cost savings. The facing skins of the sandwich panel can be considered as the flanges for the I-beam carrying bending stresses in which one face skin is subjected to tension, and the other is in compression. The core resists the shear loads and stabilizes the skin faces together giving uniformly stiffened panel. OSB is wood product that shrinks when dry and swells when adsorb moisture either due to liquid or vapor from the surrounding atmosphere. The relative combination of relative humidity and temperature is introduced into the equilibrium moisture content (EMC) tha...