Hughes Brothers has conducted over 100 full scale structure tests since our inception in 1921. Structures ranging from H-frames, single steel arm and davit arrangements have been tested until destruction to verify designs. Hughes Brothers has also done testing on aging or in-situ structures to verify their strength, possibly saving utilities millions of dollars by confirming the ability of their existing power lines to be used for a longer time-frame than expected.
Structures were initially designed using the methods outlined in the back of the Hughes Brothers catalog (see www.hughesbros.com). This method used linear analysis with some basic structural assumptions, and has worked well over the years. Thousands of mile of transmission lines have been designed using this method. These transmission lines are performing well and as expected. More recently, computer programs are the preferred method, for a more detailed analysis of each component of a structure. Each design is compared with the final result of a test to confirm the method and assumptions used to arrive at a structure’s predicted strength.
The failure modes of the structures are, at times predictable, and at other times, unexpected. Components ranging from shield wire supports to x-braces have failed. When the failure mode is a pole, the results are often spectacular and unpredictable. Destructive testing has shown that poles and wood members are performing well beyond their expected service life.
Visit our website at www.hughesbros.com to access a detailed report of tests on aging wood pole H-frame structures, as well as our latest test, which incorporates views never seen before from high-resolution cameras mounted on drones flying over the structure during testing.