Identifying a Warren truss 1

[charliealphabravo]

I am doing a routine inspection of about a dozen identical roofs built in the 40's and 50's. They each have three of these trusses constructed with 3x timbers and shear plates (42' span, 15'oc).

At this point I am just trying to identify the type of truss. Since it has no vertical webs it looks something like a Warren truss with extra diagonals.

Thanks in advance.

 

[charliealphabravo]

I guess it would help if I attached the drawing.

 

[woodman88]

Looking back, it could be based on the 1860's Brown truss see

http://en.wikipedia.org/wiki/Brown_truss

Or the 1830's Town Lattice truss see

http://en.wikipedia.org/wiki/Lattice_truss

In my 1960 Data Book for Civil Engineers it is called a lattice truss. No design information is given.
You would have to run some calculations to determine if the design requires just tension or just compression or both tension and compression for the web design.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[charliealphabravo]

Thanks woodman,
The Brown truss looks right. That would explain the bolt through the web intersections if they were expected to be in compression (based on the wiki).

Also it might resolve another matter that came up. At one location the edge of the shear plate was visible below the top cord where the webs tied in. It occurs at the first panel point from the end. The drawing also shows a small edge distance there but it shouldn't be critical if the web turns out to be in compression.

 

[paddingtongreen]

The diagonals were considered to share the vertical shear in each section. It makes for a little difficulty in that logic when only one chord is loaded.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[hokie66]

I would just analyze it as a Warren truss with the webs doubled.

 

[charliealphabravo]

If anyone is curious this is how the Tension/Compression study is turning out.