Tag Archives: non-engineered buildings

A Problem Good Structural Engineering Could Solve Part III

Part III, the conclusion by Dr. David Bohnhoff, Phd., P.E., Professor Emeritus at the University of Wisconsin-Madison.

Perhaps only people that engineer buildings understand and appreciate the true dangers and hence insanity of erecting (and then occupying) a structure of absolutely unknown strength.  To structural engineers involved in agricultural building design, NOT following the structural requirements of the governing commercial building code is crazy given the fact that the code sets MINIMUM criteria.  If you aren’t going to engineer a building in accordance with loads considered the MINIMUM for your project, then pray tell, what loads are you going to use????

The IBC, which was adopted (with modification) as the commercial building code in Wisconsin, is a code that is as applicable to agricultural buildings as it is to other commercial buildings.  The WI administration code exemption that allows for the construction of non-structurally engineered farm buildings is outdated.  In many cases, code exemptions for farm buildings are as old as the code themselves.  The first building codes were largely fire codes (much like today’s codes) that were put in place to protect loss of life and property from large conflagrations (e.g. fires that consumed entire villages in some cases).  Since farm buildings were small and located in rural areas where they were isolated from other buildings, there was little concern regarding loss of life and adjacent property when they did burn (which they often did) and hence they were exempted from building codes.  As codes have changed so have farm building exemptions.  While farm buildings are still largely exempt from fire, ventilation and energy codes, they seldom are exempt from electrical and plumbing codes, and some jurisdictions no longer exempt them from structural codes.  The latter recognizes that large farm buildings need to be structurally engineered.  In some jurisdictions (e.g. Arkansas) farm buildings must be designed and constructed in accordance with the governing commercial code, but there is no enforcement (i.e., there is no required plan submittal and no required on-site inspection).

The confusion surrounding the structural design of farm buildings has made it virtually impossible for insurance companies to offer better rates for buildings that are structurally engineered in accordance with a specific code, then for ones that have not been structurally engineered.  To this end, farmers that purchase properly engineered buildings are not getting the break due them, in fact, the more large, non-engineered buildings erected, the higher their rates become.

Builders who sell and erect non-engineered buildings (typically at the expense of reputable companies) have no incentive to change their practice.  Given that insurance companies continue to insure the buildings they erect, why change?  As soon as one of their buildings fails, he/they are right back in the farmer’s yard telling the farmer not to worry as they will take care of him/her like they always have.  They blame the failure on a rare heavy snowfall (or on the truss manufacturer or some other supplier), and then they put up the exact same non-engineered building.  It’s a double win for these builders (two buildings and two pay days).  So why should they change their practice?  Your answer may be “so they don’t get sued”.  To this I ask, when was the last time a hard-working, independent dairy farmer (not a horse farmer) sued a hard-working local builder?  Given that they could go to the same church, have friends in common, or even be related, you can pretty much guess the answer.

Make absolutely no mistake about it, the rash of agricultural building failures is virtually entirely due to the construction of buildings that are not structurally engineered by builders who in many cases could care less.  They are not among the farmers, the reputable builders, the component supplies (who often get blamed for the failures), or the insurance companies who would all benefit by requiring large farm buildings to be structurally engineered.

David R Bohnhoff, Ph.D., P.E.

Emeritus Professor

Biological Systems Engineering Department

460 Henry Mall, Madison WI 53706″

Thank you, Dr. Bohnhoff!

Non-Engineered Metal Brackets

Save Me Jesus….

I’ve been reading (and commenting) in an online thread of a blog on another website, where someone is trying to decide how to construct a new pole barn. This morning, the following post was made:

“What I had done was to dig the hole like you were going to set the post (below the frost line). I had a local welder make metal brackets with rebar welded to the flat end. Form up a square to match the size of the post, pour concrete, then insert the bracket. The posts sets in the bracket and is attached using two bolts. Building inspector didn’t have any issues with it.”

My response was:

I will truly do my best to be kind, and not go off on a total rant.

The most important point I am going to make is this – just because a Building Official doesn’t have an issue with something, does not make it either Code Conforming, or structurally sound. If I was in Code Enforcement, I would have demanded you provide calculations sealed by a registered professional engineer to confirm the adequacy of this design.

In My Humble Opinion, what you have is nothing short of terrifying. In the event of the threat of a strong wind, I would encourage you to remove any possessions you value from your building, as well as anything of value which is downwind from the building. Also, make sure you have the building well insured.

Non Engineered Post BracketThere are numerous commercially available post base metal brackets available. Very few of them are rated to be able to withstand moment (bending) forces. There is a very good possibility you could have purchased adequate and tested metal brackets, for less than what it cost to have the local welder fabricate these up for you.

From the photo, it appears the diameter of the holes is fairly small. If the columns are very close together, or the building has a very small span, they may be adequate to support the building from settling, as well as other issues.

Buildings of all sorts fail, but very few which have a RDP (Registered Design Professional) involved will ever fail, and those which do are almost universally due to loads being placed upon the building in excess of the design parameters, materials of lesser quality have been substituted, or plans were not followed. Armchair engineering is rarely a good choice. My best recommendation to you would be to hire a registered professional engineer to do a site evaluation of your building.  He/she can determine if what is in place is adequate.  If not, the RDP can design repairs to bring the building up to standards which will withstand the climactic loads which will be placed upon it. Best of Luck…and let me know how it turns out!

Engineered Buildings Part I

Some or all of a building collapses in a wind or snow storm. Upon examination, it is determined the building had several major weaknesses due to lacking engineering. The building owner is frustrated and angry as he truly believed he had purchased a properly engineered building.

A properly engineered building, in the average client’s mind, is what I refer to as a fully engineered building. A fully engineered building is developed by following three structural design steps:

  1. Calculate all loads and load combinations to which the building will be subjected.
  2. Determine how loads are distributed to building elements (this step is known as structural analysis).
  3. Then select components and connections capable of handling forces to which they will be subjected. In practice, selected components and connections will directly influence structural analysis.

A fully engineered building is one in which all structural component interactions are properly accounted for during structural analyses, and forces resulting from these analyses are used to size all components. Non-engineered building design processes do not account for component loads or actual component strengths. In the middle lies a partially engineered building.

In snow country, many collapsed building failures are triggered by unbalanced snow loads (drift or sliding snow loads) which structures should easily withstand. Upon forensic failure review, it becomes obvious these buildings were not fully engineered.

This engineering lack can be attributed to many companies involved in low or moderate risk building construction does not employ engineers.  Nor do they hire an engineer to perform structural engineering calculations for buildings they construct. Each year this lack of responsible building designing results in numerous buildings constructed which contain multiple components and/or connections not sized to handle loads the building is expected to experience.

Companies which erect or provide non-engineered buildings generally try to copy designs they have seen elsewhere. This causes a myriad of problems.

Simply copying, altering and/or scaling up an existing design completely ignores the fact loads like wind and snow are highly dependent on size, shape, orientation and building location. Also local topography characteristics and size, shape and orientation of attached and surrounding structures influence design. Additionally, snow, wind and other structural loads act in a variety of combinations and a building must be designed to handle all load combinations to which it could be subjected. Total ignorance of applicable loads and load combinations is a non-engineered building design hallmark and explains why so many buildings are damaged by wind and unbalanced snow loads which would not damage a fully engineered building.

Extremely weak connections between components are prevalent in non-engineered structures. Stresses which surround bolts, screws and nails are complex and control fastener size, spacing and placement relative to component ends and edges they connect. These conditions are seldom realized by builders attempting to mimic other building designs. Improperly assembled connections trigger and/or contribute to many building failures.

Some building companies are established by individuals who begin erecting buildings for companies which employ engineers and sell fully engineered packages. While I applaud anyone’s entrepreneurialism in starting their own business, it is indeed scary when some of these individuals start erecting or providing non-engineered buildings. Participating in engineered building erection does not make one an expert in building design, no more than designing a building makes one an expert in safe and efficient building construction.

Very few builders, architects, code officials and non-structural engineers understand the true complexity of a fully engineered pole building system. Several building elements perform multiple functions not apparent or understood by those not actively engaged in post-frame building engineering. In addition to having no idea of  loads to which a component is subjected, builders are not familiar with all methods available to resist applied loads and do not have the expertise needed to determine proper size, support system and connection designs for a building component.

One of my pet peeves is builders who call me and argue with me over “how you should design your buildings” based on the 5 or 6 pole buildings they’ve put up over the past 10 years.  Just because they didn’t fall down (yet), is their claim to be the expert!  Sadly, clients too often are duped by these guys because: 1. “This is just the way we DO buildings here” and 2. “Joe has been building around here for 30 years so he must know”.  Again, just because “Joe’s” buildings haven’t yet fallen down (and maybe never will) does not guarantee longevity and more importantly not calculated safety factors.

When I owned Apex Roof Truss, we sold a set of 60′ trusses to a builder for a building up north. Only after the building collapsed due to a record snowfall, did we get to see photos of it prior to collapse. At the time, there were several feet of snow on the roof, and the purlins between the trusses were sagging a good three inches between the trusses. Now the builder (who had written us a bum check for the trusses and his contractor registration had expired) built the building “the way he always did”. Two problems.  One, he used 2×6 purlins on edge, where the truss spacing and snow load would have taken 2×8 to carry the load (hence the hug sag) and two, he left out most of the required truss bracing.

When the purlins started breaking, everything else started sucking in behind them.

Come back tomorrow for Part 2 of 3 in my rant on under designed buildings – meaning NON –engineered pole buildings.