You could be excused for thinking that everything is falling down

We recently learned about the potential for failures and accidents in the built environment.  There are 1,000s of different ways these can happen based on the great number of structures that are out there – at least 124. (Ref. 1)  But where are the failures?  Where’s the evidence this might be happening?

It would seem to be all around you as you drive and walk in your neighbourhood, your community, your town and your city.  And you can’t escape the evidence by taking a break in the country.  It’s there too.

By way of bringing you up to speed, I describe a few failures and accidents below, in some cases with a typical cause noted.  I’ve classified them according to whether they were:

  • Small
  • Medium
  • Large and Catastrophic
  • Personal or,
  • Stupid
  • The Reality

A. Small Failures

1. Manholes and catch basins in the street are sometimes higher or lower than the road surface by a few inches.  They are design or construction failures.

Car drivers in trying to avoid the bump sometimes have accidents.

2. A narrow depression a few inches deep across a road – sort of like a hollow, upside down speed bump – is a failure.  You know them from the bump-bump as you drive across.  They are located above trenches where storm and sanitary sewers and water pipes have been installed.

The depressions result from poor compaction of the soil placed in the trench to fill it after the sewers and water pipes are installed – a construction failure.

They can also cause motor vehicle accidents.

3. Pot holes in roads are a design or construction failure.

They’re due to a weak pavement and subgrade or a poorly drained subgrade.

It’s interesting, pot holes can “grow” larger after water collects in them.  The water helps soil stick to the wheel of a vehicle as it drives in and out of the pot hole.

4. Broken pavement in public parking lots and private driveways are failures.

In the case of parking lots, the failure is due either to inadequate design or construction.  In the case of driveways, it’s due to inadequate construction.

Like pot holes, the pavement and subgrade are weak or the subgrade is poorly drained or both.

5. Sloping floors in houses or apartments are failures.

They’re due to inadequate construction – an 11″ slope from one end to the other in one house that I examined.  The mistake was found in time but not corrected.

6. Wet basements and leaking roofs are failures, of course.

B. Medium Failures

1. The floors of a multistory building, a high-rise, slope and sag at least an estimated 2 and 3 inches – a failure.

I know how high-rises are constructed, and in this case I also learned about the tight schedule the contractor was under to get it up.  This was probably a construction failure that unfolded as the floors went up.

There’s an increased risk of slip and fall accidents on sloping floors, particularly if they’re wet.

2. The concrete block and brick walls of buildings sometimes crack – a failure in some cases

The large size and configuration of some cracks point to inadequate design or construction.  Tiny cracks are usually normal.

3. The foundations of all manner of structures sometimes fail.  The failures are marked by excessive foundation settlement or total, catastrophic collapse.

A little settlement is normal.  Excessive settlement damages the structure above.  Collapse destroys the structure.

These types of failures are often due to inadequate geo-investigation of the foundation soils but sometimes due to inadequate foundation design or construction.

4. Uneven sidewalks are due to inadequate design or construction of the subgrade support or to poor drainage.

The unevenness is quite noticeable when the sidewalk is constructed of concrete slabs and one slab is a little higher or lower than the next at a joint – and easy to trip over.

I’ve classified these as medium failures because of the increased risk of trip and fall accidents.

5. The three Edmonton bridge girders that bent sideways during construction on March 15, 2015 was a failure.  No one was injured because the construction workers went home due to a wind storm.  A crane was left standing with it’s cable and strap connected to the outside girder of the three.

Although I was not involved in the investigation of this failure, I did study photographs on line and in newspapers and conferred with structural engineers and bridge designers.  I also examined the bridge from a security fence while visiting my daughter in Edmonton.

I concluded – an initial hypothesis – the wind caused the crane’s boom to vibrate and the strap to repeatedly tug on the girder and in time bend it sideways.  The outer girder was connected to the other girders causing them to bend too.  This was a construction failure.

6. The St. John river in New Brunswick sometimes floods in the spring and causes damage downstream.  Some people wondered during the flood of 2019 if it could be due to operation of the Mactaquac dam and reservoir upstream of Fredericton.

The dam was constructed to generate electricity when water pressure on the dam’s turbines cause them to turn.  The greater the pressure the faster they turn the more electricity generated.  The greater the depth of water in the reservoir behind the dam the greater the water pressure.

There would be interest in the operation of the dam in maintaining as great a depth of water as possible.  But, too great a depth would threaten over-topping of the dam and collapse – a failure.  Not good.

Water is released from the reservoir to prevent this.  But some years melting snow and rain in the watershed would cause the depth of water in the reservoir to rise more quickly.  The need to release water would get quite pressing.  The reluctance to do this would still be there because water depth/pressure is hydro power.

I can’t help but think these conflicting interests would have something to do with flooding of the St. John river.

7. Rain water flooded the electrical service rooms of a medical practice.  My investigation included uncovering the PVC pipe carrying the power lines into the rooms.  This revealed water seeping in around the outside of the pipe where it passed through the exterior wall.  Further investigation found evidence of rain water inside the pipe.

Water wasn’t supposed to be there because the top of the pipe on the outside wall where the power lines entered from the street was covered by a canopy.  Falling rain was shed by the canopy.

This was fine except a driving rain storm out of the southeast has rain soaked up-gusts.  These gusts of wind carry water up under the canopy and into the top of the PVC pipe and down the pipe and into the electrical rooms – a canopy design failure.

It’s interesting that the inadequate design was recognized during construction.  Steps were taken to accommodate the defect and it was a good solution.  Except, another problem developed involving the electric lines that breached the good solution after it was implemented.

At the end of the day, definitely a canopy design failure aided and abetted by construction failure of what seemed like a good idea.  Explaining all these issues would make your eyes glaze over so I’ll stop here.

8. The slump of soil on a cut slope along a highwaya mini landslide – is a design failure.

You sometimes see these along our highways.  They are often due to excavating the slope too steeply for the natural angle of repose of the soil, or poor drainage of the slope.  These types of failures can be up there with a catastrophic failure.

C. Large and Catastrophic Failures

1. The debris flood that happened in British Columbia early Saturday morning July 4th was a failure.  A waist high mix of mud, gravel and cobbles slid off the mountain and covered a residential property.  Another slide also occurred in the area.  The Ministry of Transport reported the likelihood of additional slides.

The slide could be attributed to poor planning years ago in allowing houses to be built in a slide-prone area in the first place or poor maintenance in not monitoring conditions like rainfall that precipitate landslides.

2. The bridge linking Canso to Durell’s Island in Nova Scotia that collapsed Tuesday July 7th was a failure.  The bridge fell down as a truck drove over it hauling a flatbed trailer loaded with a crane.

The failure was likely due to either the live load of the truck, flatbed and crane exceeding the design live load of the bridge or maintenance of the bridge or a combination.

(A live load is the weight to which a structure is subjected periodically in addition to its own dead load/weight which is always there)

3. I investigated the cause of a bridge collapse in a residential area.  A woman was injured when she drove onto the bridge debris in the stream below.

The failure was due to corrosion of the steel in the bridge that was missed during inspection and maintenance.

4. The crane that collapsed onto a multistory building in Halifax in 2019 was a failure.  It came to rest draped over the front of the building, over the top and down the other side.  The crane broke/bent at several locations along it’s length during the failure.

I am not involved in the investigation of this failure but from a distance outside the security fence it was easy to imagine – an initial hypothesis – that the wind that night, a live load, was too great for the crane.  It looked like an older crane and steel corrosion might be suspect too.

5. High retaining walls that collapse and fall down are usually design failures.  The base of one that collapsed on the coast of Nova Scotia a few years ago was too narrow.

Low retaining walls typical of residential landscaping that lean too much are construction failures and often due to inadequate drainage.

6. A man climbed a step ladder to do some work above a hung ceiling in a building.  He fell, hit his head on the concrete floor and died instantly.  One of the ladder’s legs was bent.

I was retained to investigate the cause of the accident.  There were no witnesses to report on whether or not the workman leaned one way or the other while on the ladder nor how far he had climbed up the ladder.

The bent leg and a leaning workman near the top of the ladder were of course initially suspect.  I planned a re-enactment of the accident with a professional stuntman however my client resolved a dispute arising from the accident in another way.

7. Ice falling off a roof and hitting and severely injuring a person is a maintenance failure.

8. A landslide that takes a house down with it is a catastrophic failure.

I investigated the cause of one like this on the coast of New Brunswick.  It was due to erosion of the toe of the natural slope by the Bay of Fundy.

The landslide was not an act of God because it could have been foreseen and prevented, or avoided by building elsewhere.

D. Personal Accidents

1. I was cleaning snow off the back of my neighbour’s car in his sloping driveway two winters ago.  He gets up a bit late.  I was out doing some shoveling so I thought I might as well.

I started to slide sideways down the slope towards the street.  As it turns out on some black ice.  I did good until I got to the windrow of snow left by the snow plow, fetched up and fell hard.

I like to think to this day that if I had been on skis I would not have fallen considering that East Coast ski hills have some icy runs.

My accident alerted me to the accidents waiting to happen on sloping, paved driveways – surfaces, in general, used by people –  due to black ice, due to questionable design and construction.

I see in recent years steel plates with roughed surfaces being installed on sloping sidewalks at intersections.  Smart.

E. Stupid Accidents

1. Three months after investigating the step ladder fatality I was up a step ladder putting the finishing touches on construction of a storage shed on my property.  I was nailing the fascia board in place and leaned sideways on the ladder to drive that last nail at the end when down I went.

I was lucky and didn’t hit any of the cobbles exposed at the ground surface but I did hit the ground hard and lay there for a while.  My ladder was not defective – no component failure, no bent legs – just my use of the ladder.

***

The Reality

There’s a lot of things broken and not working as they should.  It’s important to know this and that it’s all around us, even out in the country.  Also, that it’s our fault, we designers, builders and operators.  But know too, that the very great bulk of the built environment works just fine, thank you very much, and that’s due to us too, we folk who live in the built environment.  There is the potential for 1,000s of failures but they don’t happen because we get it right almost all the time.

References

  1. What’s in “…the built environment” and how many ways can it fail?  Posted July 8, 2020

 

 

 

 

 

 

What’s in “…the built environment” and how many ways can it fail?

On occasion, when blogging about the nature and methods of forensic investigation, I’ve wondered, just how many different structures are there in the built environment?  And are some more difficult to design and build than others?  If so, are some more prone to accidents and failures than others?

I have answers of sorts in the following.  But, like me, you are unlikely to believe anything more than an estimate even if I were to try that.

***

A structure is something (such as a building) that is built by people. It’s also a place where accidents and failures can happen.

Tunnels, bridges, canals, retaining walls and towers are all structures.  Also cars, trucks, helicopters and trains.  And patios, decks and raised flower beds.

It might also be something in the natural environment that is used by people.  Like the foundation soils supporting a building or a tower.  Also the slopes off to the left or right along our highways.

It’s usually a cut slope if it rises from the highway – the natural soil has been cut into or excavated to form the slope.  It’s a fill slope if it drops away from the highway – excavated soil has been dumped there and forms a slope.  These slopes assume the angle of repose of the soil, which varies for different soils.

All this excavating and dumping to construct a highway – another structure – so it can get to where it’s going.

***

One source listed 124 different engineering projects and classified these according to their complexity from Least Complex (#1) to Most Complex (#4). (Ref. 1) The classification took into account the number of parts or stages making up a project, their interrelationship, and the effort involved in analysing, designing and constructing the project.  Generally, the more parts, the more complex.

Examples of Level #1 are simple commercial buildings and storm and sanitary sewers, and of Level #3, ferry terminals, grain silos and small dams.

Almost all engineering projects involve a structure as distinct from a system or process, like a computer network.

Some of the interrelated parts of a bridge include the foundations soils, the foundations, the abutments, the piers and the bridge deck.

If it’s a suspension bridge like across Halifax Harbour there are also the main cables, the towers above the piers supporting the main cables, the anchors on the bank or shore at the ends of the cables and the vertical, suspender cables that tie the bridge deck to the main cables. (Ref. 2)

***

The next time I was driving after drafting the above I noted still more structures not included in the count of 124.  Albeit smaller ones like traffic lights at an intersection, gates at railway crossings, tall propane storage tanks at service stations and armored stone on an eroding shore line.  But still structures that can fail in some way or result in an accident.

And failures or accidents can happen at any of the 10 stages in the life of a structure, not just during the construction stage or service stage. (Ref. 3)

***

If a building, a single structure, can fail in 209 ways, excluding what happens in the basement (Ref. 4, 5), how many ways can each of the 124 different structures in the built environment fail, during each of the 10 stages in the life of each structure?  What would the total look like?

Just think of those 124 structures each with several interrelated parts and each part with several components.  A component that doesn’t work properly or breaks completely is a failure.

The stairs in a building are a component of the building structure.  The chute at the bottom of a grain silo is a component of the silo.  The railing along the edge of a bridge deck that prevents you driving or falling into the river or harbour is a component of the bridge structure.

The National Research Council of Canada found in a study that the lowly, humble basement of a building can fail in hundreds of ways. (Ref. 6)  What does that tell you about the number of ways failure can happen in the built environment?

(It occurred to me on reading this 185 page report that the study procedures and processes are a guide for analysing the cause of failures and accidents in structures, in general, other than just basements)

***

I was tempted but refrained from trying to multiply some of these numbers together to get an estimate of the likely 1,000s of ways failure can occur in the built environment.  It boggles the mind.

Thank heaven we also have good engineering in the built environment and most of the 124+ structures and the many ways each can fail – at least 209 for a building – get through the 10 stages of their life without failure or accident.  We don’t want failures but they do occur and engineers learn from them.

References

  1. Guideline For Engagement of Consulting Engineering Services, CENS, Consulting Engineers of Nova Scotia, Halifax, NS
  2. Personal communication, Jamie Yates, Yates Consulting Engineering, Fall River, Nova Scotia, June, 2020
  3. Stages in the “life” of a structure helps communication between counsel, insurance claims manager and an engineering expert. Posted July 2, 2015
  4. How many ways can a building fail, and possibly result in civil litigation or an insurance claim? Posted July 10, 2014
  5. Nicastro, David H., ed., Failure Mechanisms in Building Construction, ASCE Press, American Society of Civil Engineers, Reston, Virginia 1997 (Readily available by interlibrary loan from Memorial University, Newfoundland)  (Note: This study did not include failure at the foundation or basement level)
  6. Swinton, Michael C., NRC-IRC and Kesik, Dr. Ted, University of Toronto,    Performance Guidelines for Basement Envelope Systems and Materials, 185 pg, Research Report 199, National Research Council, Canada October 2005

 

Conferring on video with apps like Zoom: Another forensic tool

Video conferencing with apps like Zoom makes it even easier to push back against COVID-19 and do the right thing at the start of a forensic investigation.  That is, get on site quick-smart after a failure or accident and do a visual assessment.

An app like Zoom comes into the picture when the forensic expert is briefed on the incident during a video conference.  And what a marvelous way to get briefed – sitting in a bright and colourful virtual meeting room.

Microsoft Teams (‘Teams’) and Go To Meeting are two other video tools making life easier and cost effective.

***

I knew about Zoom but only just.  I learned more last Wednesday evening (June 3) when I took part in a virtual meeting with members of CATAIR, the Canadian Association of Technical Accident Investigators and Reconstructionists.  Of course it was like sitting and meeting in the same room as many of you know.

CATAIR provides accident investigators a professional and affordable way to meet and share experiences and ideas.  The association consists of serving and former police officers as well as professional engineers and others with a technical background.

The purpose of the meeting on Wednesday was to discuss organizing regular meetings of the Atlantic chapter of CATAIR as video conferences.  Also supplemental “get togethers” to discuss reconstruction topics and, generally, to stay in touch.  In the past we met in person in Amherst, Nova Scotia and Moncton, New Brunswick.

My interest in Zoom was tweaked.  A little more checking and I concluded video is going to play a big part in forensic engineering investigation in the future – starting with the initial briefing.

***

It’s big in the corporate world now.  More than half the Fortune 500 companies confer on Zoom video regularly.  Almost all the top 200 US universities do.  And that was the case before COVID-19 shut everything down.  After the lock-down is lifted many will still be working from home and conferring on video.

One of my three daughters oversees computer support for a testing laboratory with five divisions at a large hospital in Toronto.  She virtually meets with staff on video throughout the day using Zoom.  Another daughter in Edmonton works from home for a university and often relies on Zoom to connect.  My third daughter practices vet medicine in North Berwick, Maine.  Hopefully she relies on video conferencing – anything to stay clear of the COVID-19 epic centre in New York, in a sense, just down the road from her.

***

Connecting on video is enhancing our lives socially as well.  My neighbour connects with his two daughters out west weekly courtesy of the Zoom app.  One of the chaps who took part in Wednesday’s virtual meeting and his partner catch up with their family on video as well.  Guess who is going to be “meeting” with his daughters when he gets up to speed with Zoom?

***

There’s no question conferring on video using apps like Zoom is going to impact forensic engineering investigation.  For sure during COVID-19 but afterwards as well.

Forensic experts can be briefed on video now about a failure or accident so they can get on site before the dust settles and do a visual assessment.  The tools are there to be used.

This type of simple, cost effective assessment is sometimes all that is necessary.  If more forensic work is necessary, meeting during a video conference to report progress is certain to ensure continued savings.

 

 

 

 

 

COVID-19 and an initial forensic task a.k.a a visual site assessment, sans social distancing

Like mine, your work has possibly slowed a little because of COVID-19.  For that matter, I’m sure most practices and vocations.

However, we can and should follow through on one forensic task: An initial visual assessment of a failure or accident site, as soon as possible after an incident.  It’s just as important during COVID-19 days and just as easy.

This is also a forensic task that quite often is all that is necessary in determining probable cause, and quite often, cost effective in the extreme.

It’s also important to be seen to have done this by the parties to a dispute or claim.  It’s easier to explain doing too much than too little.  COVID-19 would not cut it as an excuse for not getting on site as soon as possible.

COVID-19 is not a good reason because an initial visual site assessment is carried out by the forensic expert alone. Social distancing is not a problem when you’re walking around a site by yourself doing things like the following:

  1. Noting the features in the terrain, in general, or on the site, in particular, relevant to the accident or failure,
  2. Examining the exposed surfaces of the failed structure and how it was initially constructed and it’s condition now,
  3. Measuring the parts of the structure or component that failed,
  4. Examining the surface where the victim slipped and fell,
  5. Taking terrestrial and aerial photographs and video, and, generally,
  6. Getting calibrated to the site.

Neither is social distancing a problem when taking a briefing by phone, e-mail or Zoom.  Nor reviewing documents sent by courier.

***

I recently looked at e-mailed photographs of the scene of a slip and fall.  The probable cause was known but not who was responsible.  I was able to identify from the photographs the three investigative tasks needed for determining responsibility.  One task was getting some accurate measurements on site – rough ones were possible from the photographs – plus getting that calibrating visit under my belt.

But, as I type this, it occurs to me that one of the other three tasks could be carried out in a very preliminary way and indicate probable responsibility.

***

However, we do need to get on site quickly after an incident because physical and environmental conditions change and important data can be lost.  This is the case whether it’s a breaking-news, catastrophic failure or a tiny component failure, a terrible accident or a seemingly “simple” slip and fall.  Examples of important data include:

  1. The volume of oil in the ground and the ground water after a fuel oil spill; (the change in volume depends on subsoil conditions and the topography)
  2. The location of the plume of contamination on the water table – think, a pool of oil in the shape of a feather with the big end downstream; (the location changes, sometimes very quickly, and this is important data)
  3. The condition of the floor surface at the location of a slip and fall accident; (this can change quickly)
  4. The height of flood water; (changes very quickly)
  5. Weather conditions after a crane collapses or a bridge fails; (this changes quickly but micro weather records sometimes exist)
  6. The size and configuration of cracks in a wall; (these features of a crack can change fairly quickly and often get worse)
  7. Tidal conditions at the location of a seaside structural failure; (changes cyclically)
  8. Sagging floors in a building; (are they sagging more?)
  9. Foundation conditions causing a building to vibrate; (these conditions change seasonally when they’re causing a problem)

Often, as indicated above, an initial visual assessment can point confidently at the probable cause of a failure or accident.  For example:

  1. I knew why a gabion wall failed on the coast as soon as I saw it, and it wasn’t coastal erosion (a gabion is a wire basket filled with rock)
  2. I also knew why a building vibrated in the winter as soon as I saw the sloping site and how the foundations were constructed
  3. The cause of a slip and fall accident on a wet floor in a dry sauna came to me on the drive back to my office – and where the water came from – after visually examining the site
  4. I knew why a furnace oil tank collapsed into a trench spilling oil everywhere based on a virtual visual site assessment – a study of site plans and photographs taken by others (I wasn’t permitted to go on site nor even drive the road nearby)

And if a more detailed and intrusive investigation is needed – none was in the bulleted examples above except skid-resistance testing on the slippery sauna floor – then the visual site assessment ensures more investigation is well planned.

For sure, COVID-19 might delay additional investigation till the lock-down was lifted –  but it can’t delay a visual site assessment by a lonely forensic engineering expert.  

How I got good forensic video in the spring, and you can too

I’m learning all the time – see below – about new methods of forensic investigation.  Also, hopefully, for my readers, increased understanding of the nature of expert work.  For example, aerial video from a drone has been a real eye-opener for me and some of my clients in recent years.

It struck me recently while walking my dogs in a forest that spring is a good time for taking aerial video during a forensic investigation.  For sure, fall as well.  You see through the leafless trees to a forest floor brightly lit by spring sunshine.  I can see my dogs off at a distance in the leafless forest why not the forest floor from above?

Even as I draft this blog I’m learning.  It occurs to me that a cloudy day would be even better – no shadows to confuse what you’re seeing on the ground.  A hardwood forest is best, of course, after the leaves have fallen.

For example: I flew over a leafless forest last spring during a site assessment case and got excellent aerial video.  You could clearly see a piece of gravel the size of a golf ball from 100 to 200 feet up.  The video was a dispute-resolution maker.

To be upfront with you though, it was seeing my dogs running in the forest that made me realize why I got good video last spring.

Another example: I had another case, a fuel oil contaminated site, that was in a dense hardwood forest that was a prime candidate for this type of aerial video.  It didn’t come to pass – the case went off on another tack – but I was ready to capture good video through a leafless forest.

Aerial video of fuel oil contaminated sites has been a game-changer for me in treeless terrain so why not in leafless terrain?

Why am I telling you this?  Because, if you’re processing a dispute or claim that involves an accident or failure in the built environment now is the time to get aerial video of the site.  If there are leafless trees on or near the site, go aloft now.  COVID-19 is no problem because it’s easy to keep your distance outdoors.

Chicken soup for the soul of a forensic expert

Some forensic investigations end suddenly and unexpectedly, reveal the simple cause of the problem and leave the expert feeling soooo good.  Others age us with their head-scratching complexity.

I thought this – and to tell you about it – on reading some stories in one of the chicken-soup-for-the-soul books, The Magic of Moms.  They are warm, feel-good stories that end nicely just like some forensic investigations.  They’re also well written, reason enough to read and learn from them for writing expert reports.

Some examples of chicken-soup-for-the soul forensic investigations

Example #1 One of my investigations involved re-enacting a fatal motor vehicle accident.  The accident happened when the car struck an obstacle in the road at a speed of 50 mph.  I decided to re-enact striking a similar obstacle but initially at a lower speed.

I had safety procedures in place but the car behaved so erratically at 20 mph that I knew I needed even more safety procedures.  Like a rescue crew that could get me out of an overturned car.

Then the penny dropped and I realized that if the obstacle could potentially cause an accident at 20 mph what was likely to happen at 50 mph?  I stopped the investigation with a clear understanding about the cause of the accident, and a good feeling too.

Example #2 I was retained to investigate the stability of a steep slope in an established residential area.  Was it unstable and if so why?

Slope stability analysis can be expensive and time consuming.  Lots of data collection, mathematics and number crunching.  Engineers like this sort of thing but first, boots on the ground and a quick, inexpensive visual examination.

I saw that a retaining wall had been constructed at the toe of the slope.  This would involve excavating the soil at the toe of the slope and possibly undermining it.  But did it?

I saw cracks in the ground in back of the top of the slope – a telltale sign – so it did slide down, at least in the past.  But, was it still sliding?

Examination of trees on the slope particularly saplings found that the trunks were curved, concave up-slope.  The trees kept reaching for the sky like they do as they grow, while the ground beneath their roots kept sliding down-slope.  No number crunching needed here; the slope was moving as I walked across it.  I felt good seeing this, and also glad to get off the slope.

Conclusion: The slope was unstable and this was due to construction of the retaining wall.

Example #3 I saw the same curved saplings on another slope stability problem indicating the slope was still sliding.  Not catastrophic fast sliding – not breaking-news fast – but sliding and unacceptable.

Example #4 Pie-shaped ground beneath a commercial building gave me that good soup feeling too.

I was retained to determine the cause of the foundation failure of a building.  The foundations were still subsiding years after construction causing cracks in the concrete building.  Precise surveys found 0.4 inches per year 10 years after construction.  Not a lot but too much for a concrete building.

A geotechnical investigation of the building site found that it was underlain by a pie-shaped soil and rock fill.  A few inches deep at one end of the building, 25 feet deep at the other end.  The  surface of a fill where foundations are placed subsides according to fill thickness.  More where it’s deep and less where it’s shallow.  And if it’s still settling after 10 years it means poor compaction during fill construction as well.

Strengthening the fill with cement grout fixed the problem.  None of this was inexpensive, but the forensic investigation was simple, determination of cause certain, the fix successful and the feeling good.

Example #5 I was retained to investigate the condition of a nail gun involved in a bloody accident.  Simple examination of the gun found no worn parts.  I was about to retain experts from away in the design and manufacture of nail guns when I decided to have the injured worker re-enact the accident.  He did this and I got video from three different angles with a simple iPhone and texted it to my client.  We talked about how the accident might have happened based on the re-enactment and that was enough.  It was a simple forensic investigation that ended quickly and it felt good.

I can cite other examples but that’s enough.

***

My frugal Mom would be proud of me hearing the penny drop, recognizing that the forensic investigation had determined cause sooner than expected, and saving money.

 

 

 

 

COVID-19 and forensic engineering investigation

It struck me one morning while walking my dogs that forensic engineering investigation is not constrained by COVID-19.  Experts often work alone as principal investigators conferring with other specialists as needed.  Many of the most experienced experts are sole practitioners like others in the professions.  We already “work from home” in a sense and have for years.

Expert sole practitioner “working from home”, alone

We take briefings “from home”, get documents by courier and study, visually inspect a site and “kick the tires”, research the literature, photograph and video a failure or accident site from a drone, measure the site, etc. (Ref. 1)  All done by the expert, alone.

This amount of forensic investigation is often enough for an expert to determine cause – not always, but often.  Even to go through several iterations of cause (hypothesis modification in the scientific method) like I did recently for a mini-flood. (Ref. 2)  An expert does go on site at the first opportunity though.  It’s a no no, not to.

Expert sole practitioner “working on site”, with other specialists

For sure, if it’s a catastrophic failure or accident when other specialists must be called in then a forensic investigation might need to wait – at least to finalize after the expert’s initial tasks noted above are done.  Possibly a wait of only a few short months, however, in light of the opening-up-lock-down talk of late.

Examples

As regards waiting, I’m thinking about the staging of a motor vehicle accident in a road safety assessment case I did recently.  Too many people involved to finalize that in a hurry if it had occurred during COVID-19.

Also the John Morris Rankin accident re-enactment I did a few years ago.  Also the nail-gun accident re-enactment I did not long ago.  And a bridge collapse the cause of which hung on a topographic survey of the site and the height of the flood waters at the time of the collapse.  And a building foundation failure and remediation.

There were just too many people involved up close and personal during forensic investigations like these.

Back to expert sole practitioner “working from home”, alone

But the cause of large cracks in the exterior wall of a recently constructed multi-story building?  This could be stated with great certainty by an expert based on a telephone briefing on wall construction and crack size and configuration.  COVID-19 be damned; the expert would work from home and determine cause.  I did not get retained on this one because of a hiccup in the process but it would have been a motherhood type of assessment from my “work from home” office.

References

  1. A Bundle of Blogs: Aerial video of insurance and forensic sites taken with cameras mounted on drones.  Posted October 31, 2019
  2. The scientific method in action determining the cause of a mini-flood.  Posted April 30, 2020

 

The scientific method in action determining the cause of a mini-flood

I don’t think many of us would associate the scientific method with a leak in a basement.  In this case, however, a big leak, a mini-flood, in the electrical and modem rooms of a commercial building – not the place you want rogue water.

In chasing down the cause – three possible causes ended up on the table at different times, with the third still there – it struck me I was following the scientific method without thinking.  Nice that it came naturally – it should after a few years investigating failures.

This is how I used the scientific method in this case:

  1. I thought – hypothesized – about the cause of the leak based on the evidence I initially had (see below),
  2. fixed that cause, so I thought,
  3. checked if the rooms were still leaking – a test of a hypothesis in the scientific method -,
  4. saw that they were
  5. so, modified my thoughts on cause – modified the initial hypothesis like in the scientific method,
  6. fixed the modified cause,
  7. checked if …,
  8. etc. etc…

It’s not unlike differential diagnosis in medicine. (Ref. 1) Time consuming and expensive at times but thorough and reliable – the way it must be in engineering investigation and medicine.

***

I was retained by the owners of a medium sized three story, commercial building to determine the cause of a leak in the electrical and modem rooms.  The rooms served several businesses in the building.  The rooms were separated by a partition and located on the right side of the finished basement next to the concrete walls.

I started my engineering investigation doing standard tasks.

Staff briefed me on the leak problem.  They told me that water appeared on the floor of the rooms during heavy rain and strong winds from the front, right corner of the building, the southeast.  The water flowed across the floor until the storm blew through and the rain stopped.  The source of the water behind the finished walls could not be seen.

The leaking had been going on for several years since building renovations that included electrical services.

I examined the interior layout of the building and also measured the location where the rain water first appeared on the floor.  I referenced the measurements to the rear and right, exterior walls.

I then examined the exterior layout of the building and measured the location of all features on the roof, and also on the right, brick-clad wall where the water was appearing in the two rooms.  The features on the roof and side included roof drains, exhaust pipes from wash rooms, air conditioning units on the roof and an electrical service mast on the right wall.  All places where rain water might get in.

I compared the interior and exterior measurements.  This revealed that the service mast was in the same location on the outside of the building as the mini-flood on the inside.  Good evidence

Electrical service mast construction

The service mast was a 4″ diameter PVC pipe that extended from the roof down to near the bottom of the brick wall and the top of the concrete basement wall.  The service mast carries electric wires/cables from the street to the building.  The mast/pipe was vertical to the bottom of the brick wall then horizontal through a 90 degree elbow into the wall.  The joint between the service mast and the brick wall was caulked.  Fairly standard construction.

The electrical cables from the street entered the service mast at the top through three 1.5″ x 2.5″ holes at the underside of a canopy.  The cables have what is called a “drip” loop so rain water on the cables can drip off before they go into the holes.

I hired a carpenter to take down part of the finished interior wall in the electrical room.  This revealed that the horizontal electrical service mast entered the rooms through a circular hole cut in the top of the concrete basement wall.  The mast then continued along the top of the partition between the electrical and modem rooms.

The hole in the concrete wall appeared to have been drilled several inches too low in 2004.  A plug of concrete was placed between the underside of the mast and the bottom of the misplaced hole to fill the gap.

Rogue water in the wrong place

Water stains on the bottom of the plug of concrete and down the concrete wall indicated the water on the floor was getting into the rooms at the joint/contact between the plug of new concrete and the old basement wall concrete.

Droplets of water and running water were seen at and below the plug of concrete during future rain and wind storms out of the southeast.  Very good evidence.

Based on the evidence I had at this point, January 22, 2020, I thought – my initial Hypothesis #1 – that the leak and the mini-flood was caused by rain water running down the outside of the service mast and into the electrical and modem rooms through inadequate caulking.

I hired the carpenter to apply additional caulking on top of the old and this was done.

Heavy rain and strong winds on February 27 and the floor mini-flooded again.  More evidence – the water is getting in somewhere else; the exterior caulking was not inadequate.

A suspicious gap and “drip” loopless cables

I noticed during the wind and rain storm in February that there was a gap along the steel heading to a window next to the electrical mast and that the steel was rusted.  Could rain soaked up-gusts of wind get into the window gap and mini-flood the floor?  Hypothesis #2.

But before testing Hypothesis #2 by caulking the gap along the window heading I decided to take the back off the elbow in the PVC electrical mast.  This was where the mast changed from a vertical mast to a horizontal mast and on into the electrical room.

I saw that the bottom of the interior of the mast was water stained and covered with dark, damp dust to an estimated 3/4″ up the circular interior of the mast.  The electrical cables were there with caulking everywhere around the cables filling the space between the cables and the inside of the horizontal mast.

Except for an estimated 1/2″ gap or hole at the top of one of the cables between it and the caulking.

The cables did not have a rain water “drip” loop like at the top of the service mast before going into the horizontal section of the mast.

The purpose of the caulking filling the interior of the mast around the cables was to intercept and shed any rain water that might get into the vertical mast and flow down the cables to the caulking.  The water would then flow across the caulking and onto the bottom of the service mast elbow to drain through small holes drilled there for the purpose.

However, this would not happen completely because of the 1/2″ gap at the top of one of the “drip” loopless cables – there’s no caulking at the gap/hole to intercept rain water.

The culprit? Rain soaked up-gusts of wind and “drip” loopless cables?

Some rain water was getting into the holes in the canopy at the top of the service mast.  This was evident by the water stained bottom and damp dust at the bottom of the mast elbow.  I can easily imagine rain soaked up-gusts of wind getting into the canopy holes.

Could enough water get in and some flow down the “drip” loopless cable and through the 1/2″ gap in the caulking at the top of the cable?  Then through tiny holes that might exist in the elbow at the bottom of the mast above the concrete basement wall?  From there into and through the plug of concrete and down the wall to mini-flood the floor below?  I thought so.  Hypothesis #3.

I plan to caulk the 1/2″ gap above the cable when the weather warms up.  The Duct Seal caulking used for this work is firm at room temperatures of 20 to 25 degrees, and difficult to work.  It must be easy to work to ensure adequate caulking of the gap in the tight 4″ diameter space inside the elbow at the bottom of the electrical service mast.

I’ll then wait for the next heavy rain and wind storm – hopefully soon; sorry – to test my third hypothesis.  I’ll let you know the results in an update of this blog.

Reference

  1. Blog on Differential diagnosis in medicine and forensic investigation, and soft, initial thoughts on cause.  Posted December 20, 2019

 

 

Experts: The only objective party in the judicial process

Judges, unlike forensic experts, are too intuitive in their decision making and too little, deliberative and objective.

The facts, evidence and case law are considered in a dispute but then intuition kicks in – sometimes before the facts – and sneaky bias always lurks in the shadows.

To be fair, judges are human and often dealing with a full docket and a lot of issues.  They’ve got to work fast.  They perhaps can’t be expected to be completely objective like experts who investigate and opine on one issue – for example, the cause of a failure or accident in the built environment.

Advocates for the parties involved in a dispute are partial to their client’s interests, but that’s their job.

Considering the vested interests of the parties in a dispute, an expert must be objective and impartial.  If for no other reason but to serve as a touchstone for the judge when he or she drifts too far from deductive reasoning.

***

I concluded the above based on Ref. 1 and reading the legal references and studies in the Bibliography at least once, one paper twice and another three times.  How judges judge was the topic studied and reported on in this material.  However, I can imagine the findings apply a little to other arbitrators – human nature being what it is – like juries, the Arbitrators in ADR (alternate dispute resolution) and insurance claims managers and consultants.

***

I learned of this situation – too subjective, intuitive, biased judging – when I thought to include judging in an update of a recent blog on the similarities in engineering and medicine. (Ref. 2) I was prompted to do this on reading the judgement in a case for which I provided expert services.

I know now that I can’t do that.  There are few similarities between how judges judge and engineers engineer.

I got in touch with my client in the case (Ref. 3) and another in Toronto and asked for reference material on how judges judge.  I got the material in the Bibliography which is very good.

I read the material and was shocked to learn the extent to which intuition, bias, hunches, culture, etc. figure in a judge’s decision-making, in addition to objective deliberation.  Sometimes intuition figures almost exclusively.

It’s serious enough that people in law and related fields who study this situation must develop models and theories to try and understand and explain what goes on.  They’ve got to resort to the scientific method to get a handle on how judges judge.

Anything reflecting the scientific method, that is key to the expert’s work, was almost nowhere to be found in the decision-making. Too often the decision is intuited then evidence and case law sought to support it.

The cost of the judicial process seems to be part of the problem.  The dockets are often full and a decision takes time and costs money regardless of whether it’s intuitive, deductive or a mix.

However, regardless the cause, there does appear to be a real need for more deliberate decisions by judges if what I read is any indication.  Increased accuracy of decisions in dispute resolution – therefore justice and the fair settlement of claims – may be worth the cost of reform.  Justice depends on deliberation not intuition. 

In the meantime, experts must stay the course and be objective and impartial as expected of us by the judicial process – and show the way forward for judges, and for arbitrators, in general.

References

  1. Corbin, Ruth M., Chair, Corbin Partners, Inc. Toronto, Personal communication, March 30 and April 10, 2020
  2. Differential diagnosis in medicine and forensic investigation, and soft, initial thoughts on cause.  Posted December 20, 2019
  3. Christofi, Andrew, NDD Law, Halifax, Personal communication, April 1, 2020

Bibliography

  1. Capurso, Timonthy J. (1998) “How Judges Judge: Theories on Judicial Decision Making,” University of Baltimore Law Forum: Vol. 29: No. 1, Article 2.
  2. How Judges Make Decisions, Canadian Superior Courts Association, Ottawa, Ontario 2018
  3. Read, Lucy, Arbitral Decision-making: Art, Science or Sport?  The Kaplan Lecture 2012
  4. Guthrie, Chris, Rachlinski, Jeffrey J. and Wistrich, Andrew J. Blinking on the Bench: How Judges Decide Cases. Heinonline 2007/2008
  5. Rachinski, Jeffrey, Guthrie and Wistrih, Andrew.  Inside the Bankruptcy Judges Mind. Boston University Law Review, Vol. 86:1227 2006
  6. Corbin, Ruth M., Several examples of reasons for decision illustrating assessment of evidence 2020
  7. Carlson, Nancy, Judgement and Decision Making. Presented to Ruth M. Corbin, May 2, 2017. Judges Should Not be in the Business of Defying Expectations

 

 

Can a tiny bit of evidence help a forensic expert set the record straight on the cause of the Edmonton bridge failure?

For example, evidence like knowing a steel girder stands upright on blocks on the girder-factory floor or outside before it goes to the bridge construction site.  Not braced sideways, not even a little. (Ref. 1)  Nor pulled sideways at the factory by a sling and cable connected to a crane oscillating in wind so strong workers left the site for safety reasons.

***

The bridge on 102 road over Groat Road, Edmonton failed during construction when girders buckled early on the morning of March 15, 2015. (Ref. 2, also Sources below)

The bridge consists of seven, 40-tonne girders.  Each girder consists of two 7.5 metre long end sections and a 43 metre long middle section.  The end sections are 4.5 metres deep arching up to 3.0 metres at the middle section.  The sizes are approximate.

Six of the seven girders were in place at the time of the failure.  Three of the six girders failed when the 43 metre long middle sections buckled sideways.

The girders are lifted into place by a crane with a cable and a sling attached to the top (flange) of the girder.  The sling was still attached to the outside girder, the last one placed that day, when the workers went home.

I analysed the reason the girders buckled to demonstrate how experts form and modify hypotheses on cause during a forensic engineering investigation. (Ref. 3)

News reports state that the preliminary cause of failure was inadequate cross-bracing.  I don’t agree.  As well, some time ago, I concluded after my second modified hypothesis that the failure was due to a construction crane tugging on the top of the outside girder together with inadequate cross-bracing. (Ref. 3)  I no longer agree with that combo conclusion either.

A third modified hypothesis is needed.

The tiny bit of evidence for this? If steel girders can rest on the ground in the girder-factory yard with no cross-bracing, and not bend sideways in the middle or topple over, why not overnight on the bridge?

Do you want more evidence? The ends of the middle girders that buckled were also bolted to the braced end girders.  This added to their inherent stability that kept them upright on the girder-factory floor or on the ground outside.

So what happened in Edmonton in March, 2015?

There may have been contractual requirements to put cross-bracing in place but the lack of adequate bracing was not the cause of the girders buckling.  The girders buckled because the crane boom oscillated in the wind overnight causing the crane cable and sling to tug on the top of the outside girder until it bent sideways.  There was no other reason. The two inner girders bent because they were attached to the outer girder by a bit of cross-bracing.

***

Like I said, the wind was so strong that night that the construction site was shut down for safety reasons.  Crane operators lower their crane booms in strong winds. (Ref. Sources)  Why wasn’t the boom lowered that night?

The 1.0 metre buckle sideways was well in excess of the 0.3 metre buckle that would occur under service or construction loads. (Ref. Sources) The magnitude of the buckling indicated that the force from the crane tugging on the top of the girder was greater than the construction load, perhaps much greater.  Why wasn’t this tugging load included in the construction load by the bridge designer?

***

If all bracing was in place I would still put money on all the girders bending at least a little, say, a few millimetres to centimetres, as the crane tugged on the top of the girder.  Some pictures may show that the adequately braced end girders where they were connected to the middle girders bent sideways a little too.

***

Life was good for the quite stable, free-standing girders at the girder-factory.  Then they were taken to the bridge construction site and hooked up to the oscillating crane boom and tugged sideways.  They didn’t stand a chance after that.  The Edmonton bridge was destined to fail for that reason alone – a failure waiting to happen.

References

  1. Jamie Yates, P.Eng., Civil Engineer, J. B. Yates Engineering Ltd, Fall River, Nova Scotia, Canada. Personal communication, March 9, 2020
  2. Google: Edmonton bridge failure, Groat Road, Buckling, etc. to see photographs of the buckled girders.
  3. Bridge failure in litigation due to inadequate bracing – City of Edmonton.  But, inadequate for what?  Posted March 15, 2016

Sources

I studied various photographs on-line including construction photographs taken at the time of the failure.

I spoke with Barry Bellcourt, the Road Design and Construction Manager for the City of Edmonton in 2015, also Bryon Nicholson, Manager of Special Projects. Barry mentioned the litigation and the city’s position.

I also learned from him that the bridge consists of seven, 40-tonne girders.  Each girder consists of two 7.5 metre long end sections and a 43 metre middle section.  The end sections are 4.5 metres deep arching up to 3.0 metres at the middle section.  The sizes are approximate.

I saw and photographed the underside of the repaired bridge girders from Groat Road in early August, 2015 when I was in Edmonton.

I understand it was windy the night the girders buckled and that was the reason workers were not on the job.

I spoke with four companies in Nova Scotia that operate cranes.  I learned that crawler crane booms move in the wind; flex and sway.  There is greater movement sideways because there is less strength that way.  Telescopic booms move more than lattice booms because of the greater surface area.  Booms are lowered to the ground in strong winds.  One company doesn’t operate its cranes in winds of 50 km/hr or more.

I also talked with Amjad Memon, P.Eng. a structural engineer with the Nova Scotia Department of Transportation, about the Canadian Highway Bridge Design Code.