Nonlinear Time-Dependent Behaviour of Concrete Insulated Panel

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.

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...

Composite Structures, 2018

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.

Composite Structures, 2017

Sandwich panels often need to be designed to sustain significant permanent loads, raising the need to accurately account for long-term creep deformation. However, the accurate prediction of creep in sandwich panels is not trivial, particularly owing to their composite multi-layered nature, the multitude of possible face and core material combinations, and the possible existence of through-thickness shear reinforcement (ribs/webs). This paper presents numerical investigations on the creep behaviour of composite sandwich panels produced by vacuum infusion with glass-fibre reinforced polymer (GFRP) faces and ribs, and polyurethane (PUR) and polyethylene terephthalate (PET) foam cores. Carrera Unified Formulation (CUF) is implemented, for the first time using 1D elements with an equivalent single layer (ESL) methodology, to model the creep response of simple and ribbed panels by adopting a Composite Creep Modelling (CCM) approach. Previous experimental results from creep tests carried out on such sandwich panels and their constituent materials are used to obtain time-dependent constitutive relations for the materials in various layers and validate the numerical results. Additionally, results from analytical beam models using Timoshenko beam theory (TBT) with multi-layered sections are used to further validate the numerical outputs obtained with CUF. The developed numerical models were able to predict the experimental creep behaviour of the full-scale sandwich panels with reasonable accuracy. Differences observed between the CUF and TBT models mainly stem from the inherent approximations concerning the shear correction factors used with TBT, which contrast with the solutions provided by CUF, where such factors do not need to be considered when higher degrees of approximation are used.

ACI Structural Journal, 2014

Relatively little research has been reported on the time-dependent in-service behaviour of composite concrete slabs with profi led steel decking as permanent formwork and little guidance is available for calculating long-term defl ections. The drying shrinkage profi le through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffi t, and this has only recently been quantifi ed. Based on an existing analytical model developed by the authors to calculate the time-dependent defl ection of composite slabs, a simplifi ed procedure, suitable for use in structural design, is proposed for calculating the time-dependent defl ection of composite concrete slabs that takes into account the time-dependent effects of creep and shrinkage. The method is illustrated by three examples and the results are compared with experimental data.

Journal of Mechanics of Materials and Structures, 2007

This paper deals with the buckling response and nonlinear behavior of sandwich panels with soft cores that have temperature-dependent mechanical properties and are subjected to thermally induced deformations and mechanical loads simultaneously. This study investigates the effects of the degradation of properties of the core as a result of rising temperature on the response of the sandwich panel. Analyses are carried out for cases of pure thermal loading, with either uniform or gradient temperature fields through the depth of the panel, as well as for thermal loading acting simultaneously with external mechanical loads. The formulation is based on variational principles along with the high-order sandwich panel approach. It takes into account the flexibility of the core in the vertical direction as well as the dependency of the mechanical core properties of the temperature distribution through the core depth. The stress and deformation fields of the core have been solved analytically, including the case where the temperature-dependent properties attain a complex pattern. The buckling equations are derived using the perturbation technique, yielding a set of nonlinear algebraic equations for the case of a simply-supported panel and a uniform temperature field. The critical temperatures and modes of wrinkling and global buckling are determined numerically for some foam types of core made by Rohacell and Divinycell. The nonlinear response caused by thermally induced deformations is presented for Divinycell foam core with different temperature distributions through the depth of the core. Finally, the nonlinear response caused by the simultaneous action of external mechanical loading and increased temperatures on the compressive or the tensile side of the panel, with a thermal gradient through the core depth, is presented. The interaction between elevated temperatures and mechanical loads changes the response from a linear into an unstable nonlinear one when the degradation of the mechanical properties due to temperature changes is considered and the panel is unrestrained. Moreover, the unstable nonlinear behavior becomes even more severe when the face, loaded in compression, is subjected to elevated temperatures. This study reveals that a reliable, realistic design of a sandwich panel that is subjected to elevated temperature (within working temperature range) and mechanical loads must take into account the degradation of the properties of the core as a result of the thermal field even at working temperature range, especially when cores made of foam are considered.

European Journal of Environmental and Civil engineering, 2011

Precast concrete panels are often used for the façades of modern warehouses and commercial malls. During the last two decades, they have generally been made of two concrete layers with interposed thermal insulating polystyrene boards. Traditionally, perimeter concrete ribs allow the weight of the external concrete layer to be transferred to the internal thus causing unavoidable thermal bridges which reduce the energy performance of the building. In the sandwich cladding panel, the two concrete layers can be linked by lowconductivity shear connectors crossing through the insulation layer, thus ensuring the overall thermal efficiency of the building. In this paper, the results of a wide numerical study on the behaviour of concrete sandwich panels realized with glass fibre-composite pultruded connectors are presented, focusing on the stresses and deformations caused by dead load, thermal actions and shrinkage.

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.

Australian Journal of Structural Engineering, 2014

Based on an existing analytical model developed by the authors to calculate the time-dependent deflection of composite slabs, a simplified procedure, suitable for use in structural design, is proposed for calculating the time-dependent deflection of composite concrete slabs taking into account the timedependent effects of creep and shrinkage. The method is illustrated by two examples and the results are compared with laboratory measurements and with values obtained from numerical analyses.