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The development of our in-house joist test lab shows our emphasis on quality and our commitment to
improved production practices through research and development projects. We also use the lab for
jobs where destructive testing is required by local code specs. The lab was designed by experts from
our Engineering and Quality control departments. The machine is versatile, testing joists from 10 ft
to 70 ft in length and 14" - 60" in depth. The joists are tested with the bottom chord up as the longer
top chord provides stability. This design eliminates the need for an elaborate frame system to transfer
test loads back to the earth. The machine can push a 5’ deep girder, 70’ long with 6x6x3/4"
chords up to 200% of the design load.
The floor beam is a W36x193 wide flange with shear studs encased in 4’ deep concrete for composite
action, resting on a 6" x 5’ slab for bearing. The result is an infinitely stiff section that allows for
accurate deflection measurements. The machine is powered by a 5 line hydraulic manifold system that allows
us to simulate uniform load while at the same time applying snow drift, roof top unit (RTU) or other loads
for which the test specimen was designed. Each hydraulic cylinder is capable of producing 30,000 pounds of
load. Lateral bracing, which braces the joist while allowing for deflection, is provided by aluminum arms
behind the machine that straddle each chord.
Load data is obtained through the use of load cells that give us instantaneous readings of loads in pounds.
These can be tied to a data acquisition system where load vs. deflection and stress vs.
strain diagrams can be plotted.
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