(There’s take-away insight in this item for Advocates at the case merit assessment stage, particularly in Appendices 1 and 2. The simple data there plus conferring with a forensic engineer can help you assess the technical merit of a case)
Right away, three engineers had similar thoughts about the cause of the Morandi bridge collapse August 14 in Genoa, Italy : My friend, Paul Gunson, Adelaide, Australia, in an email a few days ago, friend, Reg Crick, Halifax, during a chat, and me. (Ref. 1) Paul drove under the bridge in 2009.
Take your pick of causes from a survey of these people:
If that’s not enough, I’ll tell you a little secret below about how designers tweak - some might skimp-on - the factor of safety. (Actually, it’s good engineering not skimping but you need an informed public to understand that)
(QC as in Quality Control during construction and Water as in Lots of Water)
Paul did some research and found that the Morandi bridge and one other showed serious rusting of the steel reinforcing – too much water and too little maintenance The concrete cover was spalling in some areas and exposing the steel to the weather. There were also reports of concrete that was way below the specified strength – too little QC.
I did quite a lot of quality control of concrete and earthworks in the past and Paul’s findings resonate with me. Quality control and maintenance are not very glamorous and often get the short end of the stick.
In a blog several years ago, I added quality control and maintenance to a list that I saw of the stages in the life cycle of a building or civil engineering work – to increase the total to 11. There’s no questions they are stages where failure can occur. Ignore them at your peril. (Ref. 2)
Almost the first thing Reg said when we chatted about the bridge in Italy, “Get rid of the water!! (Stupid!!)”. Reg didn’t say “Stupid!!” but that was the tone. (Ref. 3) He was referring to proper drainage of the water from the bridge deck that isn’t provided for during bridge design. Drainage design isn’t very glamorous.
Reg noted another mutual friend Bill Waugh, who designed dozens of bridges in Nova Scotia and Jamaica before he passed away, despaired at the inattention to deck drainage during bridge design. Water rusts exposed structural steel.. There’s an element of maintenance in this as well; keeping deck drains – when they are present – clear of debris so the water can drain.
I wondered when I first saw the bridge failure why successive spans of the bridge went down after the first one? Was that continuous span of bridge deck over successive piers designed to such a low factor of safety – in the interest of looking slender and pretty – that a span relied on adjacent spans for some of it’s support? And when one span goes down, like dominoes many go down? But in hindsight I realized that proper design of bridges like this one might in fact rely on adjacent spans, but perhaps too much.
A tweaking engineering design secret: In engineering design the factor of safety is reduced – confidently whittled away – with increasing successful design and construction, and no failures. Until the pendulum swings too far, failure occurs, the pendulum swings back.and the factor of safety is put back up. This really does happen in design. (Ref. 4, pages 100, 101. A very good read)
(The factor of safety is a number got from dividing the weight you want to support safely into the greater weight that will break the thing providing the support – cause it to fail)
If you want to know more about when and where failure occurs and who is responsible – a broader picture - see Appendices 1 and 2 below.
It’ll be a while before we know why the bridge in Italy failed but the smart money is going down on over confidence during design and poor deck drainage and maintenance. And no way can I leave out poor QC during construction. Any takers?
There’s food for thought for Advocates in this item. Buildings, civil engineering works and infrastructure fail in many ways, and some of these are an easy first pick for a forensic engineering expert at the merit assessment stage. And failure doesn’t have to mean total collapse of a building, – or a bridge like in Italy – but simply that it doesn’t work right. The bridge probably didn’t work right for years, like in poor deck drainage.
Poor design, construction and maintenance can also injure people, for example, in slip and fall accidents on floors with low skid resistance.
What’s the take-away for Advocates? You’ve learned that when a failure occurs in the built environment or a person is injured experienced engineers are suspicious of what took place at certain stages in the development of a structure. Our suspicions are backed up by independent and detailed studies by researchers in the U.S. and Europe of 100s of failures.
Taken together – our experience as engineers and these studies – we have a good idea where to look for cause. If you don’t consult an expert at the merit assessment stage you risk technical failure of your case.
- Personal communication, Paul Gunson, Adelaide, Australia, 2018
- Stages in the “life” of a structure helps communication between counsel, insurance claims managers and engineering expert. Posted July 2, 2015 (See update Appendix 1)
- Personal communication, Reg Crick, Halifax 2018
- Petroski, Henry, To Engineer is Human: The Role of Failure in Successive Design, Vintage Books, New York April 1992,
- International engineering magazine publishes information on foundation engineering in eastern Canada – and also information useful to counsel on the causes of failure. Posted January 4, 2013 (See Appendix 2)
(The following was taken from Reference 2 above and updated)
You might be interested in the updated list below of the stages in the “life” of a structure in the built environment. Structures include earthworks and waterworks – a reshaping of the natural environment – as well as buildings and bridges.
I came across the basic list while reading the latest, 2012 edition of Guidelines for Forensic Engineering Practice. I added the stages in italics to those in the Guidelines. The list is a useful breakdown of the aging of a structure.
The Guidelines were published by the American Society of Civil Engineers (ASCE). Civil engineering includes structural engineering and geotechnical engineering.
I see the list providing context and facilitating communication between counsel, insurance claims managers and consultants, and an engineering expert. Failures and personal injury accidents can occur pretty well any time during the life of a structure.
Principles governing communication between counsel and expert have been developed recently by The Ontario Advocates’ Society. (Ref. 2) The following list of stages in the life of a structure will further help counsel and an engineering expert talk to one another when a failure or personal injury accident occurs:
- Quality control (during construction)
ASCE say that, “Failure can be defined as an unacceptable difference between an actual condition or performance and the intended or reasonably anticipated condition or performance.” This can occur during any stage in the life of a structure.
Furthermore, “Failure need not involve a complete or even partial collapse. It may involve a less catastrophic deficiency or performance problem, such as unacceptable deformation, cracking, water- or weather-resistance, or other such phenomena.”
It’s not difficult to imagine that failure can occur at any stage. Nor that personal injury accidents can occur at any stage.
Communication is easier for both counsel and client and counsel and engineering expert if we all have an idea of a structure’s “life” and the stages it goes through as it ages The list above can help us.
(The following was taken from Reference 5 above)
An article entitled “The expert witness and professional ethics” reports on the categorizing and classifying of the causes of structural failure as determined by researchers in the U.S. and Europe. This research reviewed the causes of hundreds of failures. Based on the research the primary causes of failure were categorized as follows:
- Human failure
- Design failure
- Material failure
- Extreme or unforeseen conditions or environments
- Combinations of the above
When professional engineers were at fault (human failure) the causes of failure could be classified as follows:
- 36%…Insufficient knowledge on the part of the engineer
- 16%…Under estimation of influence
- 14%…Ignorance, carelessness, negligence
- 13%…Forgetfulness, error
- 9%…Relying on others without sufficient control
- 7%…Objectively unknown situation
- 1%…Imprecise definition of responsibilities
- 1%…Choice of bad quality
When the percentage distribution of the failures were summarized the research found that almost half were due to errors in the planning and design of a structure and a third occurred during construction:
- 43%…Planning and design
- 16%…Use and maintenance
- 7%…Others and multiple factors
I reviewed research a few years ago that found many, possibly most, foundation failures were due to inadequate geotechnical investigation of the foundation soils.
This type of information based on what appears to be quite exhaustive research is valuable to a forensic engineer in forming an initial hypothesis of failure at the beginning of an investigation.
The information is also valuable to Counsel in assessing whether or not to take a case or gaining an appreciation of where a forensic investigation may be leading based on initial oral reports by the professional engineer investigating the cause of the failure.