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Sat 5 Sep 2009 04:00 AM

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Building failure — Part 1

Mohammed Azad Hossain identifies the most common reasons for building failure and how to avoid a collapse.

Building failure — Part 1

Building components tend to fail depending on materials, designs, method of construction, environmental conditions and the use to which the building is put. Substandard materials and design errors are major causes of component failure.

Some of the main causes for building collapses are bad design, faulty construction, foundation failure, extraordinary loads, unexpected failure modes or a combination of causes. But collapses also occur due to natural disasters such as earthquakes, floods, hurricanes, cyclones and fires.

Common design faults

All structures are designed to support loads without deforming excessively. These loads include live load, which is the weight of people and objects, rain and wind, and the dead load of the building itself. Internal factors/human errors

The internal factors for bad design don’t only mean errors of computation, but a failure to account for loads the structure will be expected 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 failures occur due to obvious negligence or gross human error.

The external factorsThese are often natural, such as extraordinary loads, heavy rain, earthquakes, hurricanes and a defective site, with very unusual ground conditions, like sinking holes or swampy land. A building that is intended to stand for some years should be able to meet all these challenges. This is incorporated into the design. Identification of the characteristics of particular site conditions by the engineers/consultants, through suitable geo technical studies, can help with 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. Common construction faults

Inappropriate construction

The contractor’s failure to build in accordance with drawings and specifications can also add to failure of structures. Use of inferior or sub-standard building materials is another reason buildings fail. Overloading during the life span of a building can critically weaken the structural reliability of it. Extra loads due to unauthorised change of use or additions and alterations to the structure can intensify an under-designed building and can contribute to its eventual failure.

Performance failures

Performance failure can be described as an intolerable difference between anticipated and existing design and construction. The engineer’s design interpretation must be put aside at the construction stage for the structure to be effectively constructed.

Failure may occur due to consultants’ and contractors’ inadequate supervision and control of site operations and quality control. Such errors ultimately lead to a situation, which may involve such failures, which are related to excavation and equipment, inappropriate sequencing, not enough temporary support; unnecessary structure weight; untimely taking away of shoring or formwork; and non conformance to design objectives.

Mohammed Azad Hossain is the head of the contracts department for Gulf Consult, Kuwait. His background includes 30 years of experience in all types of contractual, constructional and financial aspects and procedures of projects in the GCC. Hossain is a professionally qualified chartered quantity surveyor and is a fellow of the Institute of engineers.

The opinions expressed in this column are of the author and not of the publisher.

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