"RILCO" laminated wood arch (bowstring) roof framing

[Jc67roch]

Does anyone have knowledge or experience with RILCO laminated wood arch roofs from the early 1960s? This structure is a highway garage with 62 foot span. The roof is RILCO (stamped on wood) laminated wood arches that are 1 3/4" by 6 3/4" with a top height of 8'6". There is a bottom tension tie of 1 5/8 x 3 3/4" laminated wood. Both the arch and the bottom tension tie have metal splice plates at mid span. There are 5/8"x3 5/8" vertical "hangers" at roughly 7'6" on center between the top arch and the bottom tension tie. Note this arrangement does not appear to be a bowstring truss due to the lack of diagonals and insignificant size of the verticals. It seems to be more of an arch. These "arches" are spaced at 2 feet on center. I am trying to check the capacity of this type of structure - it seems very flimsy, and we are concerned about large deflections at mid span. Can anyone lend knowledge or experience with this type of construction - is it a known problem? Have there been failures? I am presuming I should analysis as a tied arch, but does anyone have other thoughts or suggestions? A photo is attached.

 

[msquared48]

There does seem to be some information on the net on this.

For example:

http://books.google.com/books/about/RILCO_Glued_Laminated_Wood_Arches_Beams.html?id=XdIwtwAACAAJ

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Jc67roch]

It appears this book shows up on a Google search, but is not available for download or purchase anywhere. Just seems to have existed at one time.

 

[ThePioneer]

It is a very typical "tied arch" framing. Rilco Laminated Products, Inc. was a subsidiary of Rock Island Lumber Company, a Weyerhaeuser family endeavor. In 1960 Rilco was purchased outright by Weyerhaeuser and became the Rilco Engineered Wood Products Division of Weyerhaeuser Company. They had laminating plants at Albert Lea, MN and Cottage Grove, OR.

You are correct, it is not a bowstring truss.

I have a file of old Rilco literature on their tied arch systems. There are span tables etc... in the literature. No detailed engineering data however.

Andreas