Weather causes forensic engineering problems – and also helps solve them

Weather is an element, a factor, or a cause of some failures or accidents in Eastern Canada.  We get a lot of weather down here so it’s not surprising.

It’s almost always one of several elements in the problems even if it’s quickly dismissed as not relevant.  It’s sometimes a factor in the mechanism leading to a failure.  And it’s occasionally the cause of a failure.

Some examples will raise your awareness

Wind a factor in bridge failure

I thought to raise your awareness of this after suggesting that wind was a factor in the failure of a bridge in Edmonton in March.  Crane cables repeatedly tugged at the top of one of the bridge girders to which they were attached.  The beam eventually failed by buckling sideways.  The cables hung from crane booms exposed to the wind. (Ref. 1)

Weather increases house maintenance

Those of you living in houses that are a few years old have probably noticed the need to paint the south side of timber clad homes more often and to re-point brick clad homes.  I know I have to do that with my home.  That’s failure – increased maintenance, due to weather.  Some of the problem is due to the heat of the sun; some is due to freeze/thaw cycles.  Weather is the cause.

Rain triggers landslide..!!

I investigated the cause of a landslide that destroyed a home in Redhead on the Bay of Fundy, New Brunswick several years ago.  Rain triggered the landslide by increasing the water pressure in the soil that then slid down.  The land was on the verge of sliding, rain was the trigger.  This “trigger mechanism” is well known in civil and geotechnical engineering.  Weather was a factor.

Snow causes roof collapse

I drove past a house this morning with a roof that had collapsed under the weight of snow that accumulated this past winter.  Weather was the cause.

Weather did not cause bridge collapse

I investigated the cause of a soil-steel bridge failure – a very large culvert, a few years ago.  People thought initially that torrential rain – four inches in a few hours, caused a flood that washed the bridge out.  However, photographs taken of the failure and a topographic survey showed that the flood was only half the capacity of the bridge culvert.  Weather was not the cause, nor a factor, only an element.  (Steel corrosion was the cause)

Dirty weather a factor in traffic accidents

Dirty weather is often a factor in traffic accidents.  Sometimes it’s a cause.

Checking rainfall

I check rainfall as a matter of course when investigating drainage and flooding problems. Sometimes it figures in the problem, sometimes not.

I like heavy rain – Sorry.  It helps solve problems

I like heavy rain when investigating some problems – Sorry.  For some problems, it quickly and reliably defines runoff patterns much better than expensive, detailed topographic surveys.  For other problems, it enables me to correlate a rough measure of discharge on a property with reported rainfall in an area. (Ref. 2)

References

  1. Bridge beams that fail are sometimes like balloons http://www.ericjorden.com/blog/2015/05/20/bridge-beams-that-fail-are-sometimes-like-balloons-filled-with-water-squeeze-them-and-they-pop-out-somewhere-else/
  2. Why forensic engineers like heavy rain http://www.ericjorden.com/blog/2014/04/09/image-credits-and-why-forensic-engineers-like-wet-weather-the-heavier-the-rain-the-better/

 

Bridge beams that fail are sometimes like balloons filled with water – squeeze them and they pop out somewhere else

My explanation for the failure of the bridge beams in Edmonton is supported by “new” information. (Ref. 1)

I said in late March that the beams buckled sideways because the cables from the booms of the construction cranes – moving a little in the wind, tugged on the top of the beam pulling it sideways.  The bracing was inadequate and could not resist this tugging. (Refs 2 and 3)

(A wind and gust forecast for the site would be useful data.  A site specific forecast meteorologist could give this)

My reasoning was based on what I saw in pictures on the Internet of the bridge failure.  It was an example of how an idea can be given for the cause of something based on limited information.  How a hypothesis – an explanation, for an engineering failure can be based on limited data, a picture in this case, and revised or supported with new data.

This is the process followed in forensic engineering investigation: Hypothesize, investigate, revise.  Hypothesize, investigate, revise.  Etc.  This process was reflected in remarks by another engineer, Yasser Korany, P.Eng., Ontario during a CBC interview.  (Ref. 4)

My “new’ data is the manner in which a steel bridge beam supports itself initially and the bridge deck later.  The data is not really “new” because bridge beams have always supported themselves in this way.  The significance of this dawned on me when I discussed the bridge failure again with a structural engineer in Halifax.

In supporting itself, the steel beam compresses at the top a tiny bit – squeezes together, and pulls apart at the bottom.  In the process, the steel beam gets a tiny bit shorter at the top and a tiny bit longer at the bottom.

The shortened beam tries to spring back to its original length - that’s what steel beams do.  It tries to do this the easy way by moving sideways.

If something is also tugging the top of the beam sideways, for example, the cable from the boom of a construction crane, then the beam just might do that – move sideways and buckle.  The beam trying to spring back to its original length and the crane cable tugging on the beam aid and abet one another in causing the beam to do this.

The buckled beams in the pictures on the Internet do look a little like the curved sections of a water-filled balloon that has been squeezed.

References

  1. http://news.nationalpost.com/news/canada/traffic-headache-major-edmonton-arterial-road-closed-indefinitely-after-girder-collapse-during-bridge-expansion
  2. http://www.ericjorden.com/blog/2015/03/27/wind-construction-crane-and-inadequate-cross-bracing-caused-edmonton-bridge-failure-an-initial-hypothesis/
  3. http://www.ericjorden.com/blog/2015/04/03/why-in-a-recent-blog-didnt-i-seem-to-consider-foundation-failure-as-a-possible-cause-of-the-edmonton-bridge-failure/
  4. http://www.cbc.ca/1.2999331

Forensic engineering practice in Eastern Canada

Abstract

Forensic engineering as routinely practiced in Eastern Canada is different from what you might imagine.  Not big, catastrophic failures and tragic accidents as reported in the press.  Rather, often enough, quite small problems unworthy of notice to the public at large.  Nor forensic engineering as ideally described in text books.  Rather, a little different and with some warts and shortcomings.

In the following, I describe what I have experienced over the years as a professional engineer specialising in civil engineering and geotechnical engineering.

Things break and fall down and people have accidents.  Civil litigation sometimes results.  Professional engineers are retained to find out why the thing broke or the accident happened and explain in written reports to the justice system – as such, assuming the role of a forensic engineer.

Lawyers retain us – those of us with certain key attributes, on behalf of the plaintiff or defendant.  Occasionally this is done when the merits of the case are being assessed but too often months or years later.

I explain how civil engineers can personally investigate many of the problems that develop in Eastern Canada.  They also sometimes function as lead investigators – `generalist“ engineers, and retain other specialists when they are not qualified for the problem.  There are few experts in Eastern Canada who investigate the same type of problem day in and day out.

(There’s a bulleted Summary at the end of this item, in addition to the abstract)

Our built environment doesn’t always work as it should – things break and fall down.  People sometimes get hurt in this environment too  

Everything in our built environment is expected to be safe and to operate as designed.

But when things do not function properly, such as:

  • a poorly maintained structure,
  • foundation settlement of a swimming pool or building,
  • a bridge failure,
  • earthworks and landslides,
  • a flood,
  • vibrating buildings,
  • traffic and slip and fall accidents,
  • a truck fuel oil spill,
  • a leaking roof, or
  • a wet basement

we are reminded that things do not operate continually or forever.  And that things are sometimes not designed and constructed properly nor are they completely safe. (Refs 1, 2 and 3)

Civil litigation sometimes results when this happens.

Engineers explain to the justice system why things break and fall down

Professional engineers are often retained by counsel for the plaintiff or defendant to investigate the cause of problems like these.  Also to identify and explain the associated technical issues to plaintiffs, defendants, counsel, judges, and juries.  These parties are being asked more and more to believe and rely upon the opinions of experts.  As such, professional engineers practise as forensic engineers either as consulting experts or testifying experts. (Refs 1 and 4)

We explain in well written reports, seldom in court

Today, after we complete our forensic investigation, we increasingly present our findings and opinions in a report according to civil procedure rules like Rule 55 in Nova Scotia.  Professional engineers seldom go to court today since the advent of rules like this. (Ref. 4)  Nevertheless, we still do our work in the event this will be necessary.

How we are retained, including the warts of the process

We are most often retained when a lawyer calls asking to describe a problem, doing this, and then responding to our questions about the failure or accident in our need to assess if we are qualified.  Counsel would most likely have learned of us by word of mouth or as a result of having some profile in the area.

Too often we are retained months or years after an action has been started rather than at the time the merits and investigative costs of a case are being evaluated.  But this is changing as lawyers learn of the benefits of retaining an expert early – serious cost benefits and better service to the justice system and the injured party. (Refs 5 and 6)

Key attributes of a qualified forensic engineer

We would most likely be qualified as an engineer to investigate the failure or accident if we had the following key attributes: (Ref. 1)

  • Suitable education
  • Training
  • Experience
  • Skill, and,
  • Knowledge

And performed our work,

  • Accurately
  • Objectively, and,
  • In a professional manner

Another key attribute: Excellent report writing skills

It’s also absolutely essential today in Eastern Canada, in light of new civil procedure rules, that an engineer have excellent report writing skills – and actually bulletproofs his report. (Ref. 7)  Where excellent testifying skills were a key requirement in the past, it’s report writing skills today.

Fees for forensic engineering services

We charge for our services according to a published schedule of fees on our website.  Contractors in Eastern Canada who are retained by a forensic engineer to do certain specialized testing and construction work are charged at cost.

Failures and accidents are small to medium sized and diverse in nature, and experts are not always available in the area

In general, problems in the built environment in Eastern Canada are diverse in nature with many and varied technical issues – seemingly no two are exactly alike. (Ref. 8) They are also small to medium sized – seldom collapses, fortunately, and certainly not newsworthy.  Experts in the specific problem are not always available in this area.

For example, a lawyer in the U.S. enquired about finding an expert on string.  He was advised that perhaps there may not be a “string expert” at large, and that perhaps a specialist trained in microscopy and hemp manufacturing technology may be of assistance. (Ref. 1)

Closer to home, there are probably no “step ladder with bent leg“ experts in Eastern Canada either, nor slip and fall experts where the victim was walking backwards, experts in the bio-degradation of old oil spills by natural attenuation, or experts in vibrating buildings.

There are experts in Eastern Canada – civil engineers who know more than the lay public about how to investigate why something broke and fell down or an accident happened - but not necessarily experts who investigate the same kind of problem day in and day out.

One engineer per problem

In Eastern Canada, one professional engineer usually works on all aspects of the forensic investigation either because of some specialized knowledge, or because he is able to figure out the problem by applying the scientific method and following established protocols. (Ref. 9)

The “generalist” engineer

Some cases, because of the nature of the problem, involve the services of a “generalist” engineer or lead investigator rather than a “specialist” engineer.  The engineer advises the lawyer on the types of specialists needed for the team, selects them, and coordinates their activities. (Ref. 1)

A professional engineer functioning as a lead investigator must have sufficient technical knowledge of the problem to recognize his technical shortcomings and retain qualified assistance when the failure or accident investigation requires expertise he doesn’t have. (Ref. 1)

For example, I investigated the cause of a soil-steel bridge failure on one occasion that permanently disabled a car driver.  At different times during my investigation I retained the services of a land surveyor, a hydrologist, two engineers experienced with corrugated steel structures – one in Ontario, the other in the U.S., and a metal detectorist.  These specialists took part in the investigation in addition to my own specialties in civil engineering and geotechnical engineering.

Summary

That’s the nature of forensic engineering practice as I have experienced it in Eastern Canada:

  • We investigate and explain why the built environment sometimes breaks and falls down, and why people sometimes have accidents
  • We explain why the thing broke, and the relevant technical issues, in a written report to the justice system, hence the label “forensic engineering”
  • Lawyers retain us to do this, those of us with certain key attributes
  • Most of the problems we investigate are small to medium sized, not catastrophic and newsworthy
  • The cause of most problems can be figured out by an experienced civil engineer
  • Sometimes he must wear his “generalist” engineering hat - lead investigator hat, and retain one or more specialists to investigate issues he’s not qualified to do

References

  1. Lewis, Gary L. ed., Guidelines for Forensic Engineering Practice, 2003, American Society of Civil Engineers (ASCE)
  2. Greenspan, Howard F., et al, Guidelines for Failure Investigation, 1989, American Society of Civil Engineers (ASCE)
  3. Janney, Jack R., Guide to Investigation of Structural Failures, 1979, 1986, American Society of Civil Engineers (ASCE)
  4. How experts are retained in civil litigation is changing and the changes are good for counsel and the justice system Posted May 1, 2014   http://www.ericjorden.com/blog/2014/05/01/how-experts-are-retained-in-civil-litigation-is-changing-and-the-changes-are-good-for-counsel-and-the-justice-system/
  5. Stockwood, Q.C., David, Civil Litigation, 2nd ed. 2004 Thompson Carswell, Toronto
  6. Please, Counsel, retain an expert “early in the life of the case” Posted March 27, 2014 http://www.ericjorden.com/blog/2014/03/27/please-counsel-retain-an-expert-early-in-the-life-of-the-case/
  7. Mangraviti, Jr., Esq., James, J., et al, How to Write an Expert Witness Report, 2014, SEAK
  8. What do forensic engineers investigate in Atlantic Canada? Posted October 9, 2014 http://www.ericjorden.com/blog/2014/10/09/what-do-forensic-engineers-investigate-in-atlantic-canada/
  9. Steps in the forensic engineering investigative process with an Appendix on cost, Posted July 15, 2013 http://www.ericjorden.com/blog/2013/07/15/steps-in-the-forensic-engineering-investigative-process-with-an-appendix-on-costs/