A masonry design research group at Hamilton, Ontario-based McMaster University’s Department of Civil Engineering is working outside the box with its research into the seismic and blast performance of masonry buildings.
The seismic research is on how “whole buildings” behave during earthquakes.
Traditionally, seismic research has focused on individual components of buildings, explains Wael El-Dakhakhni, the Martini, Mascarin and George chair in masonry design at the civil engineering department.
“We are working to provide designers with urgently needed information on how to more accurately predict the overall building performance during extreme load events.”
Last year, El-Dakhakhni won the prestigious discovery accelerator supplement grant from the Natural Science and Engineering Research Council of Canada (NSERC) for his internationally-recognized research.
The grant covers three years of masonry research by El-Dakhakhni and his team of 20 post-graduate students at the applied dynamics laboratory at McMaster, considered the largest research group studying masonry structures under extreme loading in North America.
“After our extensive studies for the past ten years, there is no lack of information on individual building components such as walls, columns and beams,” he says.
The same can’t be said for how components interact in a building. “Our design approaches will significantly change once we take into account those interactions.”
For their innovative research, El-Dakhakhni’s students use scaled models of multi-storey load-bearing masonry buildings tested on shake tables to simulate different levels of seismic hazards in various Canadian cities.
Some in-situ tests are done as well in which shakers are installed on structures for the researchers to learn more about the natural frequency and other dynamic characteristics of the buildings, he adds.
The buildings tested for seismic are constructed of reinforced concrete block. Tests to understand the blast resistance mechanism, a relatively new but more complex field, are also being conducted.
The objective is to provide practical recommendations for seismic design and construction for the new edition of the National Building Code. “Our aim is,” El-Dakhakhni says, “to develop design equations that will result in more economical and safer masonry construction.”
Countries around the world will be paying close attention to the team’s work.
Since the 2005 National Building Code, there have been significant changes and more stringent requirements in the seismic design provisions in Canada, and the 2015 National Building Code might add even more, says El-Dakhakhni.
In addition, the new Canadian standards for blast-resistant buildings would require various buildings to have different levels of protection against explosions.
It will be a “major challenge” for the masonry and construction industries to meet new design standards.
To date El-Dakhakhni’s research has shown some surprises. For instance, because of its high degree of redundancy, reinforced masonry block construction can offer equal or even better seismic performance than reinforced concrete framed structures for low- and mid-rise buildings, he says.
“There is a misconception that reinforced masonry and reinforced concrete structures do not share the same seismic performance qualities.”
El-Dakhakhni points out that a big plus with masonry block over reinforced concrete construction is the former’s ease of construction.
In buildings where masonry block is used only as a partition wall, he suggests that designers consider using it as a structural element in place of reinforced concrete because it performs well under extreme loading. “It is easy to build and the availability of skilled trades makes it an attractive solution.”
The McMaster team’s research will look at how to design concrete block construction for 15 to 20-storey buildings. To achieve that, resilient masonry walls with ductile characteristics will be required.
El-Dakhakhni says the quality of masonry blocks has increased significantly over the years. The regular quality-control tests conducted at McMaster research for concrete block manufacturers are proof.
“The block producers are using leading-edge technology nowadays. It would be very surprising if we found a block with strength less than 20 MegaPascal. Lots of them are 25-30 MegaPascal, which is similar to concrete.”