A good initial hypothesis would quickly dismiss inadequate structural engineering design as the cause of the roof collapse.\u00a0 The structure is likely to be simple in the extreme: Structural concrete slabs\u00a0supported by\u00a0regularly spaced columns bearing on concrete footings on good foundation soil.<\/p>\n
If design had been inadequate the mall\u00a0might have collapsed long ago.\u00a0 The “loads” (see below)\u00a0in a simple building are easy for structural engineers to calculate and provide for.<\/p>\n
Professional engineers are not infallible but\u00a0we are governed by professional bodies that do watch us closely.\u00a0\u00a0We carry out\u00a0our designs according to well understood principles and are held to a strict code of ethics.\u00a0 Cost is a factor in design; designs must be economical, but not at the expense of safety.<\/p>\n
It’s sometimes another matter, however, once the construction drawings leave the design office.\u00a0 Design can be all well and good but\u00a0construction inspection is sometimes left\u00a0wanting.<\/p>\n
The pressure on design engineers – not much really, is\u00a0applying fairly simple design principles\u00a0in\u00a0providing for support of\u00a0the structure, for a reasonable fee.\u00a0 The pressure on builders – quite a lot of pressue, actually, is getting the structure\u00a0erected as quickly as possible, for\u00a0the lowest\u00a0price.\u00a0 The pressure on the inspector is ensuring\u00a0the design is implemented properly, sometimes for a reasonable fee and sometimes with\u00a0experienced, full time inspection, but not always.\u00a0 Construction inspection sometimes gets the short\u00a0end of the stick as far\u00a0as being adequately funded and staffed.<\/p>\n
Inadequate\u00a0inspection and\/or faulty construction would be a good second\u00a0hypothesis as the cause of the failure.<\/p>\n
Inadequate maintenance could be\u00a0a third, particularly if coupled with inadequate construction.\u00a0 For example, inadequate drainage of corrosive water and\u00a0exposed, inadequately covered structural steel.<\/p>\n
There are many factors that could bring a building down: Corrosion\u00a0– mentioned above, weather, various aging effects inherent in the choice of materials, original design mistakes – as acknowledged above but unlikely in simple structures,\u00a0abuse, unexpected loads and external forces.<\/p>\n
These items or factors can be divided into two fundamental categories:<\/p>\n
Static loads<\/span> – weight in\u00a0laymen’s terms, are the basic weight of the building itself and its contents.\u00a0 A building has to be strong enough to resist gravity and\u00a0hold itself up.\u00a0 The static loads can be subdivided into two categories:<\/p>\n Dead<\/em> loads are loads that never seem to change in a building such as the weight of the floors, walls and roof.\u00a0 Live<\/em> loads are loads that can sometimes change in a building due to weather, occupancy, or\u00a0building use.\u00a0 For example, the people, furniture and equipment, and possibly vehicles in a parking garage (see below), etc.<\/p>\n Dynamic loads<\/span> are loads on a building that change during a relatively short period of time.\u00a0 They are repeatedly applied and released.\u00a0\u00a0Dynamic loads\u00a0are added to the static loads.\u00a0 Typical dynamic loads include strong and variable winds, machinery that pounds or shakes the floors of a building (vehicles in a parking garage?), and earthquakes.\u00a0 Dynamic loads can sometimes cause contruction materials to fail due to fatique.<\/p>\n Any one or more of several factors could have brought the building in Elliot Lake down.\u00a0 For sure, inadequate design\u00a0of a simple building is a possibility but, based on my experience,\u00a0inadequate construction and maintenace\u00a0are\u00a0more likely causes, and good second hypotheses.<\/p>\n I propose, but who knows\u00a0until a thorough forensic engineering investigation is carried out?<\/p>\n Reference<\/strong><\/p>\n James, Stuart H. and Nordby, Jon J., Editors, Forensic Science; An Introduction to Scientific and Investigative Technicques<\/em>, 2nd ed., Chap. 23, Taylor & Francis 2005<\/p>\n","protected":false},"excerpt":{"rendered":" A good initial hypothesis would quickly dismiss inadequate structural engineering design as the cause of the roof collapse.\u00a0 The structure is likely to be simple in the extreme: Structural concrete slabs\u00a0supported by\u00a0regularly spaced columns bearing on concrete footings on good … Continue reading \n