Ag construction companies throughout the Mid-Atlantic are busy repairing and, in too many cases, rebuilding livestock barns and poultry houses after February’s record snows. Here are a few pointers on what to look for from a story we posted on February 12.
Roof truss design is only as good as its weakest element. When snow loads approach design limits, if one gives way without cross-bracing support whole roofs can collapse. Large roof spans are especially vulnerable.
That's why Larry Jones, general manager of Dairy Development International, advises 40-pound per square foot snow load minimums for dairy free stall designs in the Northeast. Roofs built to hold 20 pounds per square foot aren't designed to sustain such loads due to the fatigue factor, adds Larry Jacobson, a University of Minnesota professor and engineer.
"Unfortunately, there are agricultural buildings out there that have not been designed for any particular loading at all," warns Curt Gooch, Cornell Extension dairy specialist. "These building have a much higher probability of failing."
Wood structures will show stress before they fail. Metal structures usually won't. Look for:
• New roof leaks developing
• Bowing of truss bottom chords or web members
• Bowing or cracks in rafters or purlins
• Bowing of headers or columns