October 29, 2007

Restoration

Sensors in Parliament Hill’s Peace Tower track structural strength

Renovation 10 years ago gave golden opportunity to monitor changes

KORKY KOROLUK

CORRESPONDENT

OTTAWA

Not much happens inside Parliament Hill’s Peace Tower that scientists don’t know about.

Their knowledge isn’t about the people in the structure and what they’re doing, but the very walls of the tower and what’s happening inside them.

When the masonry exterior of the tower was renovated a decade ago, officials at Public Works and Government Services Canada asked the Institute for Research in Construction if its scientists could install a monitoring system to keep track of such things as temperature and relative humidity, moisture penetration and movement air pressure differentials — anything that could affect the durability of walls.

"It's easier to install sensors if the walls are being opened for restoration work."

Nady Saïd

Institute for Research in Construction

To Nady Saïd, it was a golden opportunity.

The tower is a complex structure, he said, with several different types of stone used, some of it backed by concrete, but not near the top.

All this meant, he said, that “the exterior walls are very interesting — to us anyway — because of the chance to study the behaviour of such composite wall structures.”

Saïd’s team installed about 190 sensors of various types “to measure all kinds of parameters,” he said. The focus was on the exterior masonry walls “so we measure temperature, moisture, pressure differential, vibration of the tower, and at the back, where there had been some cracks repaired, we installed displacement sensors that measure the movement.”

The objective, he said, is that if the cracking recurs “we’ll be able to tell them the cause of the movement, because if you know the cause then you can come up with effective repairs.”

Saïd is an expert in monitoring for the IRC, which is one of the institutes that make up the National Research Council of Canada. He said he sees monitoring as a maintenance tool because when the data collected shows that something untoward is happening you can give the building owner an early warning.

Saïd said monitoring equipment was also installed during some work on the East Block of Parliament Hill some years ago, but the work on the building was stopped.

Then, he said, Public Works wondered whether the monitoring should be reinstated. As a result, the sensors have been reactivated to check moisture conditions inside the wall.

He said he would like to see sensor systems installed in all the walls as restoration work within the Parliamentary Precinct is ramped up again.

“I always recommend it,” he said. “It’s easier to install sensors if the walls are being opened for restoration work, and I think (Public Works) is open to that.”

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