I’ve blogged in the past about the importance of measuring in forensic engineering investigation.  About getting on site and getting your hands dirty and mud on your boots. This is particularly true when an engineering failure or a personal injury accident involves the natural environment or the foundations, soils and water beneath the site – wet, messy, untidy places.

Everyone should do this – experts, civil litigation lawyers and claims consultants alike.  Go and see and measure things.

I was reminded of this on Monday when I attended a workshop on Advanced Collision Reconstruction in Moncton – read on, your eyes won’t glaze over at what I tell you, and you may gain some insight into what’s important to experts.

The workshop was organized by the Canadian Association of Technical Accident Investigators and Reconstructionists (CATAIR) and presented by Advantage Forensics Inc, Toronto.  The course instructor was Jason Young, B.E.Sc., M.A.Sc., P.Eng., a senior collision reconstructionist with Advantage.  There was some emphasis in the course on simple measurement with tapes and rulers.  Also considerable emphasis on the analytical technique used by Jason.

Police officers – present and former, professional engineers and others attended the workshop, people who reconstruct accidents.  There’s a lot of very impressive expertise in this field in Atlantic Canada.  We do have a lot of car accidents in the area.  Also people like me attended who practice forensic engineering investigation.  I have a good interest in the techniques used in fields of investigation related to my own.

The session topics were:

1. Crush Energy Analysis
2. Introduction to Collision Biomechanics
3. Rollover Investigations

The topics might look heavy to non-technical people but they rely on simple measurements – first and foremost – and an analytical procedure and software.

We’ve all seen those pictures of horrible car crashes.  Cars and trucks so mangled in some that you are hard pressed to see a vehicle in the mass of metal.  In illustrating his lectures, Jason showed us a lot of pictures like this, also video of simulated field trials and tests.  Head-on crashes, T-Bones, rear end crashes, roll-overs, and pole and tree impacts.

The speed of the cars and trucks in an accident is key information in learning why and how the accident happened – reconstructing it.  No surprise there.  Speed is obtained from analytical procedures – Jason briefed us on one he uses, and software that are fed a lot of simple measurements.  But important measurements because garbage in garbage out.

Two basic measurements are a site survey – like in land surveying of old, and the crush depth.

The crush depth is a simple measure of the length and depth of the hole in the front, side or rear of a vehicle hit by another during an accident.  These measurements give the “damage profile” in accident reconstruction.  It’s not much different than measuring the length and depth of a trench excavated in your garden by a backhoe or yourself.   

The site survey is just that – measuring and describing the location and height of the features that characterize the surface of the site.  These would be the natural features in the terrain, the layout of the road, the position of the vehicles, the location of poles or trees that were hit, and the location of marks left on the ground by the crashing vehicles.  We do this simple kind of survey of a house lot before we build on it.

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Two measurements – crush depth and site survey, that quantify the mess of a car or truck accident.  There’s more involved, of course – analytical procedures and software, also knowledgeable reconstructionists, but nothing happens until the measurements are taken.

I was delighted recently when I saw the text Performance Guidelines for Basements while looking for another book in my library.  The guidelines are lengthy and comprehensive like many for the built environment – 185 large-format pages.  To some, that would be a lot of guideline for what would seem to be a lowly part of a structure.

• Performance guidelines for basements by the National Research Council (NRC)

This type of easily read guideline is important to non-technical people concerned about failures and accidents in the built environment.

The guidelines were prepared for all parties involved in the planning, design, construction and maintenance of basements.  Pretty well everybody from the pick and shovel guy to the cost control people.  NRC – and similar organizations in the U.S., publish a lot of material on buildings.

Basements – and the foundations down there, are not a glamourous part of a structure.  Except, they just happen to be the sole support of the building above – the most frequently erected structure in the world.  And the basement is often the most complicated to design and construct – if you’re going to get it right.

Other Guidelines

I have other guidelines on different aspects of the built environment.  For example,

• Moisture in Atlantic Housing by the Canada Mortgage and Housing Corporation (CMHC)
• National Building Code of Canada (NBC); a set of guidelines on minimum standards
• Slip, Trip and Fall Prevention, a Practical Handbook by Steven di Pilla.  This text is good on performance guidelines for floors and stairs

I also have guidelines on investigating engineering failures and accidents when good design and construction practices are not followed.  For example:

• Guidelines for Failure Investigation by the American Society of Civil Engineers (ASCE)
• Guide to the Investigation of Structural Failures by ASCE

There are guidelines of sorts in the published surveys of how structures fail.  Knowing how things break, fall down or don’t work properly is a first step to ensuring your structure performs properly.  For example,

• Failure Mechanisms in Building Construction by David Nicastroon.  This text  catalogues and categorizes 209 different ways a building can fail.  It’s very good and readily available.  (Just think, the building you’re in now can fail in these many different ways)
• Also, the ASCE guidelines above contain lengthy sections on some of the primary modes of geotechnical, foundation and structural failure

Errors and Omissions in Guidelines

You might wonder, why bother with a forensic engineer when there are such comprehensive guidelines on getting the built environment right?  A fair question if you didn’t know that the guidelines sometimes contain errors and omissions.

For example, the NRC guidelines mentioned above illustrate an error on page 30 in construction of the footing drainage system.  There’s also an omission in these guidelines – an explanation of the need for a drainage system beneath a basement floor.

I’ve seen errors and omissions in CMHC guidelines.

There’s an omission in the NBC – as I suspect there are in some similar Codes in North America, in the vague guidance on the skid resistance of floors.  (This was the case prior to 2015)  Building inspectors make a call now on this problem but this is not good enough.  I had to get guidance from the English translation of comprehensive German research on a slip and fall case a while ago.  I did this to corroborate information I was getting from literature in the U.S. on practice in some areas there, but not in all areas and not codified.

(The NBC code is periodically updated as it was recently in 2015.  This updating is the case for many performance guidelines)

Also referenced above, the published survey of the 209 ways a building can fail is extremely good but it’s completely silent on foundation and basement failure.  And there are many ways a basement can fail as evident in the 185 pages of the NRC publication.  Quite an omission in the text on buildings.

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Performance guidelines are good – no one would do a forensic investigation without considering the guidelines pertinent to the failed structure or component.  But not good enough to omit consultation with a forensic engineer at some point during an investigation.  They are a guide only to what must be done and achieved – and some guidelines do contain errors and omissions.