One of the most economic and versatile forms of agricultural building construction is the Postframe utility building, or what is commonly called the “pole barn”. These are buildings that are widely used on farms and ranches for housing livestock, machinery, maintenance shops, or for storing feed and grain crops. Other uses include a variety of commercial buildings, lumber sheds, warehouses, airplane hangers as well as limited residential use. Many of these buildings have a free span wood truss roof structure of 80’ - 100’ or more and are vulnerable to collapse during construction if they are not properly handled and braced.
I have worked many assignments involving the collapse of metal plate connected wood roof trusses on a post-frame building that occurred during the truss erection process and prior to the completion of the roof structure. Owners and/or builders hope to collect on their builders risk coverage claiming that the truss collapse occurred when “there was a sudden gust of wind” or “when an unexpected wind storm came up overnight”. A check of available climatological data will often reveal that wind pressure could not have been enough to cause collapse if the trusses had been properly braced.
Most modern-day post frame buildings are fabricated by building manufacturers and sold as a pre-engineered unit through local dealers. Postframe buildings erected on farms, ranches or on other rural properties are usually constructed where there are no building permit requirements, and consequently there is no code compliance inspection.
Typically, generic building drawings are prepared by the building manufacturer and it is the responsibility of the owner or builder to adapt the structure to the site. Seldom is a design professional involved in the design and construction of a post-frame building once drawings leave the building manufacturer’s facility. Truss drawings prepared by the truss fabricator disclaim responsibility for designating temporary construction bracing requirements. Some truss fabricators deliver a safety packet with the trusses and the packet will include diagrams or sketches of recommended temporary construction bracing.
Otherwise post-frame buildings on farms, ranches and rural building sites are erected with no temporary bracing instructions from the truss fabricator or a design professional. The building owner then must rely on the builder’s knowledge of bracing standards to assure that there is adequate bracing of the structure during construction. Unfortunately, when a builder is selected on price (low bid) and all required bracing is not clearly shown on the drawings, temporary construction bracing materials are ignored and the building suddenly becomes vulnerable to collapse under less than extraordinary circumstances.
The Structural Building Components Association (SBCA) and the Truss Plate Institute (TPI) have jointly published a document titled “Guide To Good Practice For Handling, Installing and Bracing of Metal Plate Connected Wood Trusses”. This document, published initially in 2006, was last updated in 2011. This document is regarded as the most complete guide to recommended temporary construction bracing that there is in the post frame building industry. Prior to 2006, a similar document known as the Building Component Safety Information (BCSI) standard was published jointly by the Wood Truss Council of America and the Truss Plate Institute. In the early 1990’s the Truss Plate Institute published a 30” x 40” standard drawing known as the HIB-91 Summary Sheet which provided details of bracing standards for wood trusses on post frame buildings. It is apparent the Truss Plate Institute has been directly involved in publishing standards for temporary bracing of wood trusses for over 20 years.
In 1976, the Northeast Regional Agricultural Engineering Service (NRAES) Cooperative Extension first published a Post-Frame Building Handbook that included standards for temporary construction bracing as well as permanent bracing. This handbook was updated periodically over the next 20+ years. These documents provide proof that there have been consistent industry standards for temporary and permanent bracing of Post-frame buildings for over 35 years and there is no legitimate excuse for the failure of a builder to implement temporary and permanent bracing standards to assure safe construction of post-frame buildings with wood trusses.
It is my experience that post-frame buildings that fail during construction are likely victims of inadequate temporary construction bracing. If a builder is lucky, and succeeds in erecting wood trusses and the rest of the roof structure of a post-frame building without experiencing failure due to inadequate construction bracing, it seems logical that the builder may have also failed to provide adequate permanent bracing since the truss fabricator does not specify all permanent bracing required for proper roof strength and stability. I have seen many post frame buildings where it is claimed that structural damage or displacement of framing components is the result of a single high wind event, and after inspection, it is apparent that the damage to the structure has been progressive over the life of the building due to inadequate bracing of the walls and roof trusses.
For those called to investigate damage to post frame buildings, it is important that a copy of the most recent SBCA and TPI guidelines for handling, installing and bracing metal plate connected wood trusses be obtained. When visiting the site with the SBCA and TPI guidelines in your possession, it may be the first time those guidelines have “graced” that post-frame building site with their presence.
The current SBCA/TPI guidelines can be viewed and obtained at the SBCA website at sbcindustry.com.
Without biomechanics the injury potential of those involved in an accident can not be determined. A typical accident investigation/ reconstruction can determine the relationship between certain elements within the accident environment and the people involved. It can not determine the injuries that may result from these relationships. Only by constructing validated biomechanical models can the forces resulting from the accident be measured and the potential for various injuries be determined.
Biomechanics is an applied science encompassing the disciplines of both biology and mechanics. It specifically utilizes the laws of physics and concepts relevant to both engineering and medicine to describe human motion and those forces acting upon limbs, joints and vital organs. The science historically has provided valuable applications in cardiovascular and respiratory medicine, orthopedic, industrial and rehabilitative medicine, automotive medicine, sports medicine, cellular mechanics, injury mechanisms related to human acceleration and/or impact trauma, and sports protective equipment.
The range of biomechanical services which relate to injury mechanisms is wide and includes medical file review and analysis, physical injury analysis and causation, three-dimensional modeling and simulation, as well as providing concise verbal and written reports.
The construction of validated biomechanical models provides valuable expertise within the areas of injury biomechanics. Injury dynamics and the role of various types of equipment and environmental designs can be effectively modeled and tested using mathematical simulations specifically targeted to the subjects’ kinematics/kinetics to confirm injury causation. With a rich selection of validated dummy models, dynamic simulations can be performed giving injury profiles and accelerations at every time instant of an accident pulse. With the proper scaling techniques, any size and shape of subject can be modeled. Typical accidents involving vehicles, pedestrians, workplace, trip/fall, watercraft, trains, buses, and amusement rides can all be modeled. There is almost no situation that cannot be modeled to assess the subjects’ kinematics and injury profiles.
Validated biomechanical models are extremely valuable in understanding pathological joint motion and/or joint forces as a result of trauma and are capable of assessing the level of injury severity sustained by humans. A review of all diagnostics and a complete review of the medical records provide the necessary materials in completing a biomechanical investigation. Typical areas of biomechanical analysis include: spinal injury, concussion, bone fracture, solid and hollow organ trauma, carpal tunnel syndrome, rotator cuff tear, hip, knee and shoulder injury, cumulative trauma disorder, seat belt and airbag induced injury, temporomandibular joint (TMJ) disorder and knee meniscus and ligamentous injury.
In civil cases typical areas of biomechanical analysis include:
Validated biomechanical models have effectively been utilized to support testimony in criminal cases for both the prosecution and defense in the following areas: