Researchers show simple construction change can double earthquake resistance

UBC researchers have discovered that by using oversize wooden sheets
in wall construction they can double the ability of many wood-frame
structures to withstand wind and earthquake forces.

“We knew already that North American platform construction is an
efficient method to withstand wind and earthquake forces. The proof
was in Kobe, Japan where buildings with this type of construction
withstood earthquake forces much better than traditional Japanese
post and beam structures,” says Helmut Prion, an assistant professor
with a joint appointment to the Dept. of Civil Engineering and the
Dept. of Wood Science.

The standard method of residential wall construction in North America
involves framing a wall using vertically positioned and evenly spaced
wooden studs, and then nailing sheets of plywood or oriented strand
board (OSB) to the outside of the frame.

Prion and Frank Lam, an assistant professor in the Dept. of Wood
Science, found that by building a wall using standard construction
techniques and a single large sheet of oriented strand board instead
of multiple smaller sheets, they could double the load the wall
can bear.

“What our research has shown is that by just using considerably
larger sheets we can greatly enhance the wall’s ability to withstand
earthquake and wind forces.”

The research team is halfway through a two-year project which has
received support from the Structural Board Association and funding
from the National Research Council’s Industrial Research Assistance
Program (IRAP).

The team hopes to find ways to apply its research findings to the
construction of larger commercial structures, such as warehouses
and retail spaces, which at present usually require the use of large
structural members for strength and support.

The research team tested both standard walls and walls made of
a single sheet using hydraulic jacks to apply a uniformly distributed
vertical load along the top of a fixed wall, while applying pressure
laterally in one direction across the top of the wall, or alternately
pushing and pulling the wall from an upper corner.

“Almost all failures are in the nail connection, with nails breaking
or bending and pulling out, or with the wood around the nail giving
way,” says Prion, adding that while the larger pieces of board have
not been buckling under pressure, alternate framing methods may
have to be considered to avoid stress concentration around windows
and doors.