Tag Archives: Collapse

Root Cause Analysis - Incident Investigation

The Collapse of Agricultural Buildings

By ThinkReliability Staff

Every winter there are pockets of agricultural building collapses in areas that have seen heavy snow and ice accumulation.    The causes for these collapses can be examined in a Cause Map, or visual root cause analysis.  First, we begin by capturing the basic information about the issue.  In this case, there  were three areas that suffered building collapses due to winter weather accumulation.  This included New  York State in 1999,  Wisconsin in 2010, and England in 2010 and 2011.  Important to note is that each of these areas experienced heavy snowfall during the periods of collapse and in each region, agricultural buildings were more likely than other types of buildings to have collapsed.  It is also important to note that in each of these areas, agricultural buildings were not regulated to the same level as other buildings.

To begin our root cause analysis, we begin with the impacts to the goals. The collapse of an agricultural building carries with it the risk of human injury or loss of life, as well as potential loss of livestock.  A building collapse results in property damage as well as time spent on cleanup, repairs, and anything else that needs to be done to get the facility up and running again.

To continue the analysis, we begin with the impacted goals and ask “why” questions.  These impacts to the goals are all related to the collapse of an agricultural building.  The collapse of a building results when the stress (in this case, the structural load) exceeds the strength.  The structural loads in the case of the collapsed buildings generally result from accumulation of ice and snow, which  may be unevenly distributed, increasing local load, due to drifting, and an improperly engineered building.  Agricultural buildings are more likely to collapse due to structural loads because they are exempt from codes in most of the US and unregulated in England.  If engineering is desired, a properly engineered building may be scaled up or altered, resulting in changing loads and strengths, meaning the engineering review may no longer be valid to protect the building.  Although engineering is frequently skipped due to cost measures, experts say that proper engineering can save money by ensuring that supports are put in only where they’re needed (and, of course, reducing the risk of a collapse.)

Generally the collapsed buildings are found to have inadequate bracing, which reduces the strength of the building to the point of collapse.  If the buildings are not properly engineered, bracing may be inadequate for the design of the building.  Another issue  frequently seen is that the trusses are engineered, but are not reviewed with respect to the overall building design, leading to an insufficient analysis that does not take into account all of the factors that impact building loads and strength.

Although states and countries could elect to consider agricultural buildings in their codes, farmers don’t need to wait.  If you are building an agricultural building (or any building that may be exempt from code), ensure it’s adequately structurally engineered.  It may save a life.

To view the Outline and Cause Map, please click “Download PDF” above.  Or read more:

1999 collapses in NY State

2010 collapses in Wisconsin

2010 & 2011 collapses in England

Root Cause Analysis - Incident Investigation

Deadly Stage Collapse at State Fair

By Kim Smiley

On August 13, 2011, a stage at the Indiana State fair collapsed, killing seven and injuring dozens more.  The accident occurred just before 9 pm as a crowd waited to watch the popular country band Sugarland perform.

Why did the stage collapse?  What caused this tragic accident to occur?

This incident can be analyzed by building a Cause Map, an intuitive, visual format for performing a root cause analysis.  The first step when beginning a Cause Map is to determine what goals have been impacted.  In this example, the focus will be on the safety goal since there were fatalities and many injuries.  Once the impact is determined, the Cause Map is built by asking “why” questions to determine what causes contributed to the accident.

In this example, people were killed and injured because they were near the stage and the stage collapsed.  They were near the stage because they were waiting for a concert and the area had not been evacuated.  The area had not been evacuated because the decision to evacuate wasn’t made in time.  The decision didn’t happen in a timely manner because it wasn’t clear who had the authority to make the decision because there was not an adequate emergency plan in place.  The bad weather wasn’t a surprise.  The storm was being monitored and the National Weather Service had issued a warning, but the decision to evacuate wasn’t made until too late to prevent the tragedy.

Recently findings by investigators determined that the stage collapsed because it wasn’t up to code.  The structure was required to be able to withstand winds up to 68 mph, but the stage collapsed at winds below this limit.  Investigators determined that the lateral supports were inadequate and the stage wasn’t strong enough to stand up to the wind.  The stage also wasn’t inspected because it was a temporary structure and they are not required to be inspected.

On Tuesday, (April 17, 2012)  Indiana Governor Daniels reported that he has ordered temporary outdoor structures to be inspected by the Indiana Department of Homeland Security to help prevent a similar accident in the future.

To view a high level Cause Map of this incident, click “Download PDF” above.

Root Cause Analysis - Incident Investigation

Bluff Collapse Releases Coal Ash

By ThinkReliability  Staff

On October 31, 2011, a bluff collapsed at a power plant on the shores of Lake Michigan.  The resulting mudslide took trailers, storage units, at least one truck and an unknown amount of coal ash into the lake, which provides drinking water for more than 40 million people.  Cleanup is ongoing, but the overall impact to the environment has not yet been determined.  Fortunately, no personnel were in the objects that ended up in the lake, so there were no injures.

Although the safety goal was not impacted by this incident, there was the potential for personnel injury.  Additionally, the environmental, customer service, property and labor goals were impacted by the pollution of the lake, loss of property and necessary cleanup.  The causes for these impacts to the goals can be examined in a Cause Map, or visual root cause analysis.

The mudslide which took the objects and coal ash into the lake was caused by insufficient stability of a bluff overlooking the lake.  The bluff’s instability was caused by degraded ground material stability mixed with water and no vegetation.  The vegetation had been removed for construction.  The ground in the area had been filled with coal ash – a practice allowed in previous decades.  Coal ash is less stable than soil, especially when it is exposed to water.  In this case, aerial images suggest that the water seeped into the area from a high water table or from an unlined retention pond used to store storm water.  Although a construction project was ongoing, an environmental impact study – which may have unearthed concerns about the stability of the area – was not considered necessary.

Steps are being taken to clean up the lake to the extent possible.  However, concerns about coal ash in this area and others are prompting a review by Congress to determine how coal ash can be safely dealt with.  Many say this incident suggests that stronger controls are needed.

To view the Outline and Cause Map, please click “Download PDF” above.  Or click here to read more.

Root Cause Analysis - Incident Investigation

Metrodome Collapsed

By Kim Smiley

At about 5 am in the morning on Sunday, December 12, 2010, the roof of the Metrodome collapsed under the weight of snow accumulated during the heaviest snow storm in almost two decades.  According to the National Weather Service, Minneapolis received a whopping 17.1 inches of snow between Friday and Saturday night.

The Metrodome is home to the Minnesota Vikings and its collapse set off a multicity scramble as the NFL worked to reschedule the Monday night game between the Vikings and the Giants that was planned to take place in the Metrodome on December 13.  After considering all the options, the game was moved to Detroit.  (Ironically, this was the first Monday night game played in Detroit in a decade because of the Detroit Lions’ abysmal record.)

Despite some early optimism, the latest update is that repairs will not be completed until March. The damage to the Metrodome moved the last two games of the Vikings’ season and will impact the schedule of about 300 college baseball games along with many other events planned in the venue.  In addition to the massive schedule impact, the cost associated with the repairs will be significant.

Why did this happen?

A Cause Map can be started using the information that is known.  To build a Cause Map, begin with the impacted goals and add Causes by asking why questions.  In this case, the impacted goals considered are the Production-Schedule goal and the Safety goal.  Fortunately, there were no injuries during the collapse, but the impact to this goal is included because of the potential for injuries if the Metrodome collapsed while occupied.  Click on the “Download PDF” button above to see the initial Cause Map built for this example.

The Metrodome design includes an inflatable dome to protect the venue from the harsh Minnesota winters.  The massive amount of snow accumulation on the dome after the severe storm exceeded the capacity of the dome to stay inflated.  The dome is made of two layers of materials (the outside layer is Teflon coated fiberglass and the inner layer is made from a proprietary acoustical fabric) and air is constantly pumped into the space between the layers to keep it inflated.  The massive weight of the snow tore the roof in several places and it collapsed.

The high winds that accompanied the snow fall were also one of the causes contributing to this accident.  When there are heavy snow falls, workers typically climb on the roof of the Metrodome and use steam and high powered hot water hoses to melt snow and limit accumulation.  Workers were unable to access the roof due to safety concerns because of the strong winds.  Additionally, the other measures used to prevent accumulation were inadequate.  These measures include pumping hot air into the dome and heating the stadium to about 80 degrees to help melt snow.

To view a video of the Metrodome collapsing from inside dome click here.