Summer Research Project Tests Load-Bearing Capacities for Timber-Framing Construction
Giustino Iuliano ’16 may be new to civil engineering, but he hasn’t
wasted any time getting hands-on experience in his major field.
summer, he’s working alongside Col. Grigg Mullen’76, professor of civil
engineering, to test the load-bearing capacity of floor joists used in
traditional timber framing construction.
The project is part of a
larger effort by Mullen, a timber framing expert, to contribute to the
knowledge base of that ancient art so information about the load-bearing
capability of beams can be included in modern building codes.
precedent works, but modern building code folks want proof,” said
Mullen, who’s been involved with timber framing for over 15 years. “As
an engineer, we need something to hang our hats on instead of, ‘Well,
it’s always been OK.’”
To help expand the knowledge base for
types of wood commonly found in Virginia, Iuliano is testing 12-foot
timbers cut from four tree species: white pine, white oak, red oak, and
poplar. For each type of wood, Iuliano is testing joists cut at three
depths: two inches, three inches, and four inches.
Moisture is a
critical component in determining the strength of wood, so Iuliano
measures the moisture content of each timber by weighing a sample,
drying it in an oven and weighing it again afterward.
“Historically timber frames are built with green wood, so the frame is weakest when it’s first assembled,” said Mullen.
to dry on their own, added Mullen, heavy timbers such as those Iuliano
are testing could take up to a decade to dry completely. The oven simply
speeds the process, he explained, so moisture content can be part of
So far, Iuliano has found that the wood is losing a quarter or more of its weight in the oven.
the small pieces of wood are drying, Iuliano tests the timbers
themselves. Using a jack similar to one used to lift an automobile,
Iuliano applies pressure to each piece of wood for 20 minutes to measure
how much stress the wood can take before cracking.
pressure as a wind load,” Iuliano explained. A load cell attached to the
jack records the amount of pressure applied in each test.
far, Iuliano has found that the strongest of the massive timbers – a
piece of white oak with a four-inch joist cut – withstood 28,000 pounds
of pressure. By contrast, a piece of white pine with a two-inch cut
failed at only 6,000 pounds.
A typical residence, said Mullen, is
usually designed to take about 2,000 pounds of pressure. “That’s when
you’re having a frat party and everybody’s dancing,” he added.
and Iuliano plan to present the results of their work at a meeting of
the Timber Framers Engineering Council, to be held Aug. 7 in Burlington,
Vt. “The goal [of that organization] is to get timber framing covered
in the design codes,” said Mullen.
He continued, “The standard 2 x
4 construction stuff is well covered by the codes. It’s the green heavy
timber that drives the building code folks nuts.”
of timber frame buildings is not in question. On a trip to England,
Mullen once visited inside a timber frame church built in A.D. 600 “If
you keep a roof on it, it’ll stand forever,” he said.