ISA Proposes New Wind Design Criteria for Freestanding Signs
Culminating a 7-year research effort, ISA and the Outdoor Advertising Association of America (OAAA) submitted a joint proposal on December 29, 2012, to revise the 2010 edition of the American Society of Civil Engineers /Structural Engineering Institute (ASCE/SEI) 7 standard. This standard specifies wind-load criteria for the designs of outdoor, commercial-type sign structures. These criteria are adopted and referenced in the International Building Code (IBC) which represents a key reference cited in local jurisdictions' building codes across the nation. If successful, the code change will reduce construction costs for freestanding sign structures while maintaining safety as a priority.
Changes to wind-load requirements originally adopted by the ASCE in 2005 (and repeated in the 2010 standard) substantially increase construction costs for freestanding sign structures of all types. When these requirements were originally adopted, ISA's Mechanical & Structural Subcommittee reviewed the changes and representatives of ISA and OAAA made presentations at ASCE headquarters to summarize concerns that the revised code might not be appropriate for commercial-type sign structures. The positions of ISA and OAAA suggest that, if the current ASCE requirements are found to incorporate certain elements that reflect over-design, this might create excessive project costs for sign construction projects in the U.S., while not resulting in improved performance.
ISA's initial outreach efforts attracted the interest and participation of OAAA whose members share a common interest in wind-load design standards. In 2007, ISA and OAAA made the decision to jointly sponsor research at the Texas Tech University Wind Science and Engineering (WISE) Research Center in Lubbock, Texas. The initial phase of this research launched in 2008 and the study involved construction and testing of both a full-scale, outdoor sign structure and various scale model signs analyzed in the Texas Tech wind tunnel lab.
The goal of this research and the corresponding ISA/OAAA proposal is to provide scientific data independently evaluating the current ASCE/SEI 7 design criteria and suggesting modifications. The ISA/OAAA research provides new data that supports improvements in design efficiency and safety of outdoor sign structures. For more information, contact Bill Dundas, ISA Director of Technical & Regulatory Affairs.