Channel beams have been designed with the main purpose of giving large resistance to bending while the torsional strengths are known to be relatively small. In this experiment, a cantilevered channel beam was loaded with a concentrated load at the free end, first through the experimentally determined shear center and then through the centroid of the cross section. For each loading condition, the strains were measured with the aid of SR-4 strain gages placed at intervals along the length of the beam. With the aid of a computer, the strains were converted into longitudinal stresses and these stresses were compared to the theoretically predicted values of longitudinal stresses.
The derivation of the torsional stress equation as shown in the text Advanced Mechanics of Materials by Seely and Smith is briefly compared to the derivation of the torsional stress equation as shown in the text Strength of Materials by Timoshenko. The two derivations are discussed and, even though the derivations are completely different, the values of longitudinal stress obtained by the use of each equation agree very well with each other.
The longitudinal stresses calculated from the experimentally obtained values or strain agree very closely with the theoretically predicted values of longitudinal stress --Abstract, page iii
