Peter L. Datin

Wind Loads on Single-Family Dwellings in Suburban Terrain — Comparing Field Data and Wind Tunnel Simulation

Components and cladding on residential structures continue to be damaged in high winds despite improvements to building codes. Modern wind design codes that are helping to prevent structural damage to buildings are not as effective in preventing building envelope failures. Since 1998, a unique collaborative effort between Clemson University, the University of Florida, and Florida International University called the Florida Coastal Monitoring Program (FCMP) has been collecting full-scale pressure and wind speed data on residential buildings in suburban areas. The program, sponsored by the Florida Department of Community Affairs (FDCA), was developed to increase our limited full-scale data available on wind loadings of low rise buildings – none of which was obtained during sustained hurricane force winds until this project. Another objective was to determine the validity of current design wind load values that are based on wind tunnel tests using open-country exposure. This serves as the primary motivation to study pressure variation on roofs of suburban houses. This paper presents results of the field data collection and analysis of pressure coefficient data from field experiments and wind tunnel results obtained at Clemson University’s atmospheric boundary layer wind tunnel.

Experimentally determined structural load paths in a 1/3-scale model of light-framed wood, rectangular building.

It has been speculated that much of the losses from hurricane damage to single-family wood-framed residential structures is due to design based on faulty understanding of the structural load paths in these buildings. This NSF-supported research presents a new approach to understanding load paths in wood-frame residential structures and establishes a relationship between spatially varying wind loads and structural load paths. A 1/3-scale wood frame gable roof building was constructed with geometrically scaled wood members, sheathing, and nails. The model scaled the flexural stiffness ( EI ) of the roof sheathing for wind loads applied normal to the surface. A dense grid of point loads were used to develop the influence coefficients (and surfaces) for 20 vertical reactions located at roof-to-wall and wall-to-foundation connections. The linear elastic structural response for roof-to-wall connections was limited on the roof surface to within two trusses of the applied load location. As expected there was a greater spread of load effect at the foundation level (6–8 trusses) because the exterior wood stud walls acted as stiff, vertical diaphragms. The influence functions were combined with wind tunnel pressure data for a similar shaped model from which the dynamic wind loads were estimated using a database-assisted design methodology. There was reasonable agreement between the dynamic reaction load traces with design loads obtained by components and cladding (C&C) design approach of ASCE7. Results also suggest the main wind force resisting system (MWFRS) method underestimates the design wind loads at roof-to-wall connections.