There are defects in the conventional seismic design for foundations as most jurisdictions in earthquake-prone regions specify fixed-based foundations be built to support structures. Department of Civil and Environmental Engineering professor Lijun Deng says conventional foundations force structures to take on too much responsibility during earthquakes but they can't—sometimes after an event you will see that one storey in a building has collapsed onto another. But if you share the responsibility between the foundation and the structure, the structures will perform much better. Deng’s research goal is to design innovative building foundations that have some ‘rocking’ behaviour which will improve the performance of soil-structure systems in seismic events.
Deng and his research team look at case studies from earthquakes, conduct research and work on building code development. In some earthquakes in Chile and Japan, they have observed a few cases where rocking foundation saved the structures and human lives. The team also conducts small-scale centrifuge tests and the results they have observed show that rocking-foundation bridges perform much better than bridges with conventional foundations. With regard to code development, New Zealand has begun to accept rocking foundations methodology and California might. The latest ASCE-41 (Seismic Rehabilitation of Existing Buildings) guidelines have actually incorporated the rocking foundations—but it is not code.
We want to build structures that will save people’s lives—that is always the goal,” says Deng. “Safety is always the first priority. We don’t want to see a structure collapse. In earthquakes in Chile and New Zealand and Japan you saw a lot of residential buildings that fell over and there were a lot of fatalities. The last major seismic event in Western Canada was off the coast of Washington in the 1700s—it was a magnitude nine, which is comparable to the earthquake in Japan in 2011. There are definitely risks, even in Western Canada.”