Fire-retardant treated plywood (FRTP) has been used as roof sheathing in approximately one million dwelling units throughout the eastern United States. In the mid and late 1980's a significant number of structures began to exhibit severe thermal degradation of FRTP as a result of absorbed solar energy. Due to a variety of factors, it is not possible to predict how FRTP will perform in any particular structure. Currently, there is no nondestructive test that satisfies the need for a rapid and accurate method to quantitatively evaluate the condition of FRTP. Visual inspection is still the most common method of assessing FRTP, yet significant strength loss can occur before there is any visual evidence. A method is proposed to evaluate FRTP in-siru which involves the relationship between mechanical impulse and the physical properties of materials. Specifically, a number of low energy mechanical impacts are delivered to the FRTP and the impulse record (force over time) is measured and analyzed as an indicator of residual panel strength . The Phase I research demonstrated the feasibility of using impulse testing to provide a direct measurement of residual strength. Phase II will refine the test method for applicability to a wide range of in-siru conditions.
Anticipated Results:The goal is to provide a fast, simple method which can be used by an inspector to reliably assess the current condition of in-siru FRTP. The method would provide a go/no go output, allowing an immediate determination if sheathing replacement is necessary. Available to building owners, builders, FRTP treaters, county and city officials, engineers, architects and insurers, the proposed method would allow a rational, orderly approach to rectifying a very large and costly problem. As a result, financial and resource savings should be achieved through accurate and objective decision making.
