Modeling Structural Insulated Panel (SIP) Flexural Creep Deflection

Abstract

Creep testing of oriented strand board/foam structural insulated panels (SIPs) was conducted to measure the midspan creep deflections of SIP beams loaded in quarter point and to test the effects of SIP thickness, load duration, as well as core shear stress. A relative deflection relationship was generated for both the expanded polystyrene (EPS) and urethane SIPs from the faw creep deflection data that had been screened based on previously determined limits of viscoelastic linearity. A five element, four element, and three element viscoelastic model along with a power model were all used in the validation procedure to predict the three month relative creep deflection. EPS SIPs were tested at the 2/3 stress level for six months to determine the model capability in predicting relative deflections beyond the experimental time span. Both the five element and the power model were recommended for predicting the EPS and urethane SIP relative deflections for the three month load duration.