Demolition science

A recent plan to demolish an 81-year-old structure in Turkey went terribly wrong. Thanks to a video posted online, hundreds of thousands of viewers have watched the building roll on its side and land on its roof, instead of demolishing into itself in a pile of rubble. Mehrdad Sasani, associate professor of civil engineering at Northeastern and expert on how buildings respond to manmade or natural disasters, discusses what might have happened and what can be learned from the event.

It’s probably safe to assume that the way this building toppled over was not intentional. Based on the video, without knowing much more, what do you think happened?
You are right: it must not have been intentional! The main idea in demolishing structures is to impose damage to the structure’s load-bearing components, such as columns and walls. The weight of the structure then does the rest of the job, bringing it down. In this case, however, instead of the structure’s weight crushing the structural elements at the back and coming straight down, it rotated around the insufficiently weakened elements and turned over.

How common is it for a building being demolished to behave differently from the plan?
I do not have any detailed statistics, but I have seen many cases like this in the last several years. Obviously, the more experienced a demolition company is, the less likely things are to go so wrong.

What determines whether a building needs to be demolished?
The main reasons for demolishing a building are the age of the building and a change in how it is used. In the latter case, buildings are often demolished when the cost of bringing them up to code and making them functional for a new use is prohibitive.

What goes into the planning process for the safest, most efficient demolition?
Demolition methods are determined by cost, the length of time it takes to destroy the building and the target’s proximity to other buildings. In general, buildings taller than about 10 stories are demolished by implosion. For shorter structures, mechanical equipment, such as a wrecking ball or heavy machinery, is used.

What can engineers learn from seeing demolitions go awry, and how does your research lead to safer structures?
When a building does not collapse following an implosion or damage that was initially imposed, it may become significantly deformed. We can study these large deformations and determine why the demolition went wrong. We apply that knowledge to a properly modeled structural collapse and, in turn, develop new and effective methods both to improve the collapse-resistance of existing structures and to design new buildings that better resist manmade and natural disasters that can lead to collapse.