Jason A. Partain, P.E.

This article covers adjustment factors, deflection requirements, and load combinations that affect the design of sawn lumber wood framed stud walls. The article briefly covers computer solutions and why they may not be appropriate for stud design.

It has been estimated that each year 2.5 million decks are constructed or rebuilt. Statistically, deck collapses are responsible for more people being killed or seriously injured each year than any other part of a house. The two most common points of failure for decks are ledger-to-band joist connections and guard rails. While the International Residential Code (IRC) has provided design requirements for decks and guard rails in the past, only recently have they begun to include prescriptive… Show more

It has been estimated that each year 2.5 million decks are constructed or rebuilt. Statistically, deck collapses are responsible for more people being killed or seriously injured each year than any other part of a house. The two most common points of failure for decks are ledger-to-band joist connections and guard rails. While the International Residential Code (IRC) has provided design requirements for decks and guard rails in the past, only recently have they begun to include prescriptive details to meet those requirements. The American Wood Council (AWC) has published a series of design guides for code acceptance covering topics such as fire resistance and post-frame buildings. The latest publication in the series is Design for Code Acceptance 6: Prescriptive Residential Wood Deck Construction Guide (DCA-6) (AWC 2010). Although much of the guide uses general engineering to provide designs, ledger-to-band joist connections and guard rail post attachments have been tested to determine the design requirements relevant to residential decks. This article will provide a brief overview of DCA-6, will cover the tested topics that can benefit engineers and will provide an overview of material selection for decks. Show less

Improperly constructed gable end walls are a known weakness in residential structures in hurricane prone regions. With many of today’s architectural designs using increased wall heights and roof slopes, gable end walls can even be a concern in buildings with wood roof framing systems in areas of low wind design speeds or seismic activity. There are several references available for prescriptive design of these structural components for residential structures. Although these references are… Show more

Improperly constructed gable end walls are a known weakness in residential structures in hurricane prone regions. With many of today’s architectural designs using increased wall heights and roof slopes, gable end walls can even be a concern in buildings with wood roof framing systems in areas of low wind design speeds or seismic activity. There are several references available for prescriptive design of these structural components for residential structures. Although these references are subject to limitations, they provide a basis of design that can be used for any structure. This article will discuss general design considerations, two basic methods for bracing gable end walls, prescriptive design methods available and their limitations, and provide recommended details for complete bracing of a gable end wall. Balloon framing of gable end walls is outside the scope of this article. Show less

This study considered the effect of the variability of lumber strength and stiffness on the structural performance of wood trusses. Four truss types and two species of lumber were considered. Multiple trusses in a sheathed roof system were not modeled in this study. Trusses were assumed to be loaded independently and not connected to adjacent components. Each truss was simulated 1000 times, using randomly generated lumber properties. Each simulation produced a load ratio for that truss. In… Show more

This study considered the effect of the variability of lumber strength and stiffness on the structural performance of wood trusses. Four truss types and two species of lumber were considered. Multiple trusses in a sheathed roof system were not modeled in this study. Trusses were assumed to be loaded independently and not connected to adjacent components. Each truss was simulated 1000 times, using randomly generated lumber properties. Each simulation produced a load ratio for that truss. In the simulations the failing member was not always the same, and in some cases members that were under stressed in the original design failed during a given simulation. Under this condition the truss generally could carry 3 to 4 times more load than the design load. To account for this situation and to determine the benefit gained by a low stressed member failing, the load ratios were scaled. By this method the 5% exclusion level of truss strength could be determined and the benefit of having under stressed members in the original design could be quantified. These analyses indicated that the predicted truss strength based on the 5 percent exclusion level of the truss strength distribution was between 1.05 and 1.40 times the truss strength if all members of the truss were loaded to full capacity in the original design. The increase in independently loaded trusses was due to some of the members not being loaded to their full capacity. The average increase was 17 percent.
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