Determining the Efficacy of a Retrofit Technique for Residential Buildings Using Holistic Testing

Abstract

Failure of roof-to-wall connectors in residential buildings, in the form of metal clips, during strong windstorms and hurricanes are often reported as a major cause of roof failures. Nonintrusive fiber reinforced polymer (FRP) connections are considered useful replacements or retrofitting alternatives for intrusive metal connectors for roof-to-wall connections (RTWC) in residential buildings. FRP connections are advantageous as they are nonintrusive and corrosion resistant as opposed to metal connectors. To investigate their wind performance, FRP connections in a large-scale low-rise building were tested at the wall of wind (WOW), a large open jet wind testing facility capable of simulating hurricane winds at different speeds and up to 70 m/s, which represents a Category 5 hurricane. Prior to the WOW experiments, the FRP sheets were individually tested in the structures lab to determine their pull-out strengths. Based on the results, FRP sheets were used as RTWC in a 1:4 scaled model of a typical wooden residential house with a gable roof. The model was exposed to wind speeds ranging between 27 m/s and 54 m/s at the mean roof height. Initial results showed that the uplift load capacity of the FRP connection is adequate for resisting wind induced loads at high wind speeds (up to 52 m/s, Category 3 hurricane). In addition, the WOW tests were also used to experimentally estimate the failure wind speed of the connection in comparison to the theoretical calculation. A close agreement was obtained between the theoretical and experimental failure wind speeds. It was concluded that theoretical failure wind speeds, obtained from the strength equation of the connection, for a given roof configuration can be accurately estimated from component level testing for the uplift capacity of the connection and aerodynamic loads calculated based on current building standards (such as ASCE 7). The effective design and development of nonintrusive roof to wall connections can significantly reduce property losses in tropical storms and hurricanes, thus positively impacting the economy of the U.S. and the safety of its citizens.

Fiber Reinforced Polymer as Wood Roof-to-Wall Connections to Withstand Hurricane Wind Loads

“…The experimental results revealed that the load capacity of the FRP tie exceeded the load capacity of hurricane clips. On the other hand, Azzi et al [23] experimentally studied the behavior of roof-to-wall connections strengthened with FRP under simulated hurricane conditions. It was found that FRP sheets were more effective than metal connectors in terms of strength.…”