Flexural Creep Effects On Permanent Wood Foundation Made Of Structural Insulated Foam-Timber Panels (Thesis) (original) (raw)
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Flexural Creep Effects on Permanent Wood Foundation Made of Structural Insulated Foam-Timber Panels
CSCE 3rd International Structural Specialty Conference, 2012
The structural insulated panel (SIP) 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. PWF is subjected to gravity loads associated with lateral soil pressure. To use the available combined bending and axial compression equation for PWF design, it was observed that the soil pressure would cause short-term and long-term flexural creep deflection of the wall that would decrease the wall capacity. Information on the long-term creep behaviour of SIPs under sustained triangular loading, simulating soil pressure, is as yet unavailable. As such, this paper presents a summary of flexural creep tests conducted to determine the increase in SIP deflection under soil pressure over a period of eight months. Using the experimental data, the available mathematical and mechanical creep models were evaluated to predict the flexural creep constant (K) of SIP foundation wall subjected to soil pressure over a service life up to 75 years. A flexural creep constant was then proposed to determine the long-term eccentricity of gravity loading in the available combined bending and axial compression equation for PWF design.
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.
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.
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.
Structural behaviour of insulated foam-timber panels under gravity and lateral loading
2021
A Structural Insulated Panel (SIP) is a structural element of expanded polystyrene insulation (EPS) core sandwiched between two oriented-strand boards (OSB). This research proposes SIPs in low-rise residential construction (i.e. houses and low-residential building), replacing the traditional conventional joist floors and stud walls. This research investigates (i) developing expressions for flexural, compression, monotonic racking and cyclic lateral load capacities of SIPs as compared to the joist/stud wall construction. In this study, the proposed design of SIPs was based on (i) generally established theory for analysis, (ii) assessment of full-scale SIP panels by a loading tester, and (iii) computer modeling using the finite-element modeling. The research program included (i) testing SIP walls in axial compression and bending, (ii) racking and cyclic testing on SIP shear walls, (iii) development of finite-element computer models of the tested SIP panels and verifying those using ex...
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...
Experimental study on the flexural behavior of structural insulated sandwich timber panels
2021
A series of flexural test and creep tests were conducted on 53 OSB structural insulated sandwich timber panels to predict their behavior when subjected to gravity loading when used in residential and low rise nonresidential buildings. The experiments were designed and performed to test full-scale panels for roof and floor residential construction. The structural adequacy of the developed sandwich panel system is investigated with respect to the effectiveness of the foam core in providing composite action required to meet both strength and serviceability limit-state design reruirements per Canadian Standards for timber design. Strength requirements included flexure and shear, while serviceability check included limiting deflection under operating conditions as well as creep performance under sustained loading. Results from experimental testing were used to draw conclusions with respect the structural qualifications for these SIPs to be "as good as" the structural capacity o...
2010
A Structural Insulated Panel (SIP) is a panel composed of foam insulation core laminated between two oriented-strand boards (OSB). SIPs deliver building efficiencies by replacing several components of traditional residential and commercial construction, including: (i) studs; (ii) insulation; (iii) vapour barrier; and (iv) air barrier. A SIP-based structure offers superior insulation, exceptional strength, and fast installation. Besides those benefits, the total construction costs are less with SIPs compared to wood-framed homes, especially when considering speed of construction, less expensive HVAC equipment required, reduced site waste, reduction construction financing costs, more favorable energy-efficient mortgages available, and the lower cost of owning a home built with SIPs. This paper presents a summary of the experimental testing on selected SIP sizes to investigate their long-term flexural creep behavior under sustained triangular loading. The subject panels are proposed to be used as basement walls in residential construction where the walls carry the gravity loading from the building in addition to lateral soil pressure. Two SIP sizes were considered in this study, 2.7 m and 3.0 m height, respectively, with 1200 width and 210 mm thick. The experiment study performed in a manner to comply with applicable ASTM test methods and Canadian Codes. It should be noted that the long-term creep tests were performed over nine months and resulted to determine 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.
Effects of Variable Climate Conditions on the Behavior of Post-Tensioned Mass Timber Wall Panels
World Conference on Timber Engineering (WCTE 2023)
Post-tensioned (PT) mass timber rocking walls are innovative lateral force-resisting systems used in resilient seismic design. The system relies on an initial tensioning of wall panels using high-strength steel rods. However, tension losses are known to occur in PT systems over time, especially when these systems are exposed to variable climate conditions. In mass timber rocking wall designs, existing creep models do not allow for reliable prediction of long-term PT losses. Thus, the purpose of this research is to characterize the long-term behaviour of PT mass-timber wall panels exposed to variable climate conditions and to develop a model for reliable prediction of the effects of such exposures. The mass timber panels consist of ANSI PRG 320 approved cross-laminated timber (CLT) and mass ply panels (MPP). The components of the complex effect of long-term variable climate exposure are isolated by comparing data collected on similar panel specimens exposed to controlled humidity cycles in post-tensioned and unloaded conditions with those collected on loaded specimens exposed to a constant environment. Panel in-plane deformations, loads, and moisture content in the tested systems are continuously monitored. These tests provide data for the development of an in-plane creep model for mass timber panels that will be validated on two monitored full-scale 9.1 m tall post-tensioned rocking walls, exposed to naturally varying indoor conditions in a large-scale structural testing laboratory for 12 months. This paper summarizes the experimental data collected from specimens in the environment with controlled humidity cycles and the constant environment and some lessons learned. The data shows the following trends: (1) it appears that, during the test time frame and under the imposed changing environmental conditions, the PT system's response is dominated by the in-plane shrinkage and swelling of the specimens, (2) the MC profiles of the PT panels have a significant effect on the panel's strain behaviour, and (3) under constant environmental conditions, the CLT panels experienced more viscoelastic creep compared to the MPP panels.
Timber frame houses resistant to dynamic loads - seismic analysis
MATEC Web of Conferences, 2018
The aim of the article is to present results of seismic analysis results of two real-sized timber frame buildings subjected to seismic excitations. The first model was insulated with mineral wool, the second one with polyurethane foam. Technology and specifications involved in both models construction is based on the previously conducted experimental research on timber frame houses, including wall panels tests, wall numerical models and study on material properties and precisely reflect results of the those research. During the seismic analysis reference node located in buildings were selected. In selected node displacement values were measured and compared between two analyzed models. The results of the numerical analysis presented in the article indicate that the application of polyurethane foam for a skeleton filling of the timber-frame building leads to the increase in stiffness as well as damping of the whole structure, which results in a considerable increase in the seismic resistance of the structure.