Thesis
Span Rating of Wood-Plastic Composite Decking
Washington State University
Master of Science (MS), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004593
Handle:
https://hdl.handle.net/2376/118667
Abstract
Wood-plastic composite (WPC) deck boards are span-rated in accordance with ASTM International D7032: Standard Specification for Establishing Performance Ratings for Wood-Plastic and Plastic Lumber Deck Boards, Stair Treads, Guards, and Handrails. While this standard requires a 750 lb concentrated load check (300 lb design load multiplied by a safety factor of 2.5) to establish WPC stair tread span ratings, there is no such requirement for deck boards intended for normal use. Deck boards commonly experience concentrated loads in service, mainly from footfall of deck occupants. Under reasonably anticipated dynamic actions on decks such as walking or running, the vertical load of occupants is amplified beyond their static weight.
This study critically reviews the ASTM D7032 standard for a concentrated load requirement and testing procedures for WPC deck boards as well as the effects of load amplification of occupant loads realized under dynamic occupant behaviors on light-frame wood construction. This study also investigates and quantifies the effects of partial fixity for WPC deck boards fastened with composite deck screws or hidden fastener systems.
The findings of this study support a recommendation to update ASTM D7032 for the addition of a 300 lb concentrated design load requirement alongside the current strength checks to establish span ratings for WPC deck boards. The concentrated load is to be applied over a 25 in2 square area at midspan of one span, tested in a two-span configuration, to represent the footprint of a large adult on a continuous deck board. The value of 300 lb is determined from a static weight of 220 lb for a large adult multiplied by a dynamic load amplification factor of 1.35.
The findings of this study also support a recommendation to update ASTM D7032 for the inclusion of a 30% increase in the bending strength of WPC deck boards spanning multiple supports when fastened with composite deck screws or manufacturer-approved hidden fastener systems. Tests conducted in this study suggest the increase in bending strength due to partial fixity is significant and should be incorporated in establishing the span ratings of WPC deck boards.
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Details
- Title
- Span Rating of Wood-Plastic Composite Decking
- Creators
- Ruvim Sergeyevich Yerokhin
- Contributors
- Donald A Bender (Advisor)Adam R Phillips (Committee Member)James D Dolan (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 104
- Identifiers
- OCLC#: 1371058767; 99900898939301842
- Language
- English
- Resource Type
- Thesis