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.