Evaluation of creep performance of structural insulated panels (SIPs): phase 2

Abstract

Structural insulated panels (SIPs) were creep-tested to determine the magnitude of long-term deflection and recovery, as well as changes to strength and stiffness, compared with a control group. This report documents the second phase of a two-phase testing process. The first phase was reported in FPL-RN-0332. In this second phase, 56 SIP control specimens were tested in static bending to failure. Of these, 28 were 12 in. wide by 12.25 in. deep by 19 ft long and 28 were 12 in. wide by 6.5 in. deep by 10 ft long. A matching set of 56 specimens were instrumented for deflection and subjected to 90 days of constant (creep) load, which was set at approximately one-third the average short-term breaking strength of their control group per industry practice. They were then monitored unloaded for 30 days for deflection recovery. For the 12.25-in.-deep specimens, the creep deflection was approximately 15% of the corresponding short-term deflection at failure, with a total 30-day recovery of 81%. The 6.5-in.-deep specimens had a creep deflection of 11% of the short-term failure deflection with a total 30-day recovery of 91%. After creep testing, the specimens were static-load-tested to failure. The 12.25-in.-deep specimens failed at about 90% of the non-creep-tested control failure load. The 6.5-in.-deep specimens failed at approximately the same load as the non-creep-tested control specimens. This report documents the findings of the testing of the SIP panels as well as issues of concern encountered during the testing process.