The answer, usually: exceptional circumstances. In modern times and in developed countries, where buildings and other structures are well designed and a lot of checks are undertaken during the design and construction stages, the cause of failure can often be complex and multifaceted. It bears repeating that we won’t know the reason behind this particular building’s collapse, but, speaking generally, a single reason for structural failure is uncommon.
It is also worth recognizing that advances in technologies — structural theories and calculations — have extended our knowledge of architecture and engineering and reduced the failures. These advancements have allowed us to make exceptionally strong materials and develop a capacity to understand their limitations, a vast improvement on empirical building methods of ancient times.
When buildings do collapse, however, it is sometimes due to unusual external forces — such as wind, earthquakes, gas explosions, fires, hurricanes, unpredictable snow and ice accumulation or impact that exceed the assumed loads which the structure was designed for. In these circumstance it’s not hard to understand why a building might fall.
Poor workmanship and badly constructed buildings, or the use of deleterious materials that do not comply with what was specified in the design, can also be a cause of failure. This can arise from undeliberate incompetence, but in rare cases can be considered criminal negligence.
So, with the possibility of unforeseen events, or structural issues that are invisible to the untrained eye, how can we be sure our buildings are safe?
Though building codes have evolved to better guard against collapse, when structural failures are first noticed, its paramount that test are undertaken, and proper remote and timely monitoring actions are put in place to check for such things as crack propagations. It’s also good practice to undertake non-destructive surveys, chemical tests and sometimes even small destructive tests to establish the nature and scale of the problem. Such actions require expertise, but tenants must bring issues to the attention of authorities and owners when they see warning signs; such as large cracks in the structure, fragmenting of material, vibration of floors and walls, or excessive changes in shape of the structure.
It is not uncommon to undertake surveys when property is purchased, but it’s less common to survey a property that has been in the same possession for a long time.
With the economic costs of new technologies such as drones, which can examine the elements of a building that were once inaccessible, structures that are showing distress or are above a certain age should be examined as a matter of course to prevent as best as we can more failure and tragic loss of life.
So, while we can’t yet ascribe a cause to the tragedy in Miami, we can learn a lesson in building safety. Designers, builders, owners and tenants must all be vigilant and investigate the root cause of structural issues when they arise and more readily survey their properties to ensure that buildings that were once safe, remain safe.