Why buildings fail

Mohammed Azad Hossain

Analysis shows that building components tend to fail at different rates depending on the materials, designs, method of construction, environmental conditions and the use to which the building is put. Substandard materials and design errors are identified as major causes of component failure.

The causes of building collapse can be classified under general headings to facilitate analysis. These headings are:

• Bad Design
• Faulty Construction
• Foundation Failure
• Extraordinary Loads
• Unexpected Failure Modes
• Combination of Causes

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However, buildings or any structural may collapse due to natural disaster and calamitous conditions such as major earthquakes, floods, hurricanes, tornadoes, fire, terrorist acts.

What are the most common causes of building collapse in terms of design?
Buildings, like all structures, are designed to support certain loads without deforming excessively. The loads are the weights of people and objects, the weight of rain and the pressure of wind--called live loads--and the dead load of the building itself.

The following factors may be visualised for the common causes of bad design as well as design failure:

Internal factors/Human Errors
The internal factors for bad design does not mean only errors of computation, but a failure to take into account the loads the structure will be called upon to carry, erroneous theories, reliance on inaccurate data, ignorance of the effects of repeated or impulsive stresses, and improper choice of materials or misunderstanding of their properties. The structural engineer is responsible for these failures, which are created at the drawing board. Sometimes the failure occurred due to obvious negligence, a gross human error.

The External Factors
These are often natural, such as extraordinary loads, heavy rains, or the shaking of an earthquake, or the winds of a hurricane and a defective site with very unusual ground conditions like sinking holes, swampy land etc. A building that is intended to stand for some years should be able to meet all those challenges and required to be incorporated in the building design. Identification of the characteristics of particular site conditions by the engineers/consultants, through suitable geo-technical studies, can guide decisions about site selection and site progress that reduce the risk of failure.

Inadequate Awareness
Many structural failures have been the consequence of poor technical research and knowledge. As technical awareness gets better, errors are becoming by far the major cause of known structural collapses, mainly in technologically advanced countries. An error in this situation is a gross error or mistake, not a negligible computation error or construction divergence.