Hip and Valley Support Location in Wood Framing

Wood Light frame construction is one of the most common types of construction methods for residential and light commercial building in North America and parts of Europe. The typical roof framing for wood framed building is sloped and consists of several structural members such as rafters, hips, and valleys which are connected to the ridge and ceiling joists. The common slopes for roofs are 3/12, 8/12, and 12/12. Wood framed residential roof failure is most commonly caused by wind damage in such buildings. In the recent study, one of the weaknesses of wood framed roofs is long unsupported structural member lengths, such as hips and valleys. The purpose of this research is to find the critical support location for long hips and valleys with different slopes. ForteWeb software is used to find the critical location. The analysis results demonstrating the maximum unbraced hip and valley length are from 8.5 to 10.25 ft. dependent on the slope and roof type.





References:
[1] Amini, M. O. & van de Lindt, J. W., “Quantitative insight into rational tornado design wind speeds for residential wood-frame structures using fragility approach,” Journal of Structural Engineering, 140(7), 2014.
[2] Standohar-Alfano, C. D. & van de Lindt, J. W., “Tornado risk analysis for residential wood-frame roof damage across the United States,” Journal of Structural Engineering, 142(1), 2016.
[3] Graettinger, A. J., Ramseyer, C. C. E., Freyne, S., Prevatt, D. O., Myers, L., Dao, T., Floyd, R. W., Holliday, L., Agdas, D., Haan, F. L., Richardson, J., Gupta, R., Emerson, R. N. & Alfano, C., “Tornado Damage Assessment in the aftermath of the May 20th 2013 Moore Oklahoma Tornado,” Tuscaloosa, AL: The University of Alabama.
[4] Changnon, S. A., “Tornado losses in the United States,” Natural Hazards Review, 10(4), pp. 145-150.
[5] Madan L Mehta, Walter Scarborough, Diane Armpriest, Building Construction: Principles, Materials, & Systems (Book Style), New York 2018, pp. 343-404.
[6] American Forest & Paper Association, Washington, DC, 2001.
[7] International Building Code, Washington, DC, 2018.
[8] International Residential Code, Washington, DC, 2018.
[9] National Design Specification for Wood Construction, Virginia, 2018.
[10] Sarah A. Stevenson, Gregory A. Kopp and Ayman M. El Ansary, “Framing Failures in Wood-Frame Hip Roofs under Extreme Wind Loads,” (Dissertation Style), Western University, 2017.
[11] Simmons, K. M., Kovacs, P. & Kopp, G. A., 2015. Tornado damage mitigation: benefitcost analysis of enhanced building codes in Oklahoma. Weather, Climate, and Society, 7(2), pp. 169-178.
[12] van de Lindt, J. W., Pei, S., Dao, T., Graettinger, A., Prevatt, D. O., Gupta, R. & Coulbourne, W., 2013. Dual-objective-based tornado design philosophy. Journal of Structural Engineering, 139(2), pp. 251-263.