| Self-drilling screws are used for attaching roof and wall panels to structural framing and are often subjected to tensile loads caused by negative wind pressures. A failure mode often associated with this loading condition is pullover, which occurs when a fastener pulls through the sheet but remains attached to the structural framework underneath.; The American Iron and Steel Institute (AISI) has developed several standard tests for pullover. Previous research at the University of Florida has focused on one particular test and has found that it is unconservative, providing fastener load capacities 2.5 times greater than load capacities measured in an actual installation. Given this discovery, a proposal was made to AISI in 1993 requesting further study of pullover and its effects by testing a wider range of variables and providing a reduction factor for the standard test. The proposal was approved and research began in May 1994.; In order to determine the reduction factor for the standard test, simulated tests were performed in addition to the standard tests. While initially using the simulated testing apparatus, many difficulties were encountered and adjustments were made to improve the simulated data. From these adjustments a new and improved apparatus for the simulated test (the vacuum box test) was developed and proposed to AISI in the summer of 1995. The proposal was approved and a new series of simulated tests were included. Rather than testing single components alone, this new series included system testing, which modeled the actual conditions more realistically. For these reasons, the system tests proved most valuable when determining reduction factors for the standard test.; The purpose of the research was to provide a better understanding of pullover. The first approach was to determine a reduction factor for the standard test specified in the AISI Cold Formed Steel Design Manual. The second approach was to develop both theoretical and empirical methods for designing through-fastened metal panel systems that resist pullover. |
