The investigation of the strength of a rigid-jointed frame is a problem of considerable practical importance. The precise effects of the secondary stresses arising from the rigidity of the joints have in the last half century been the subject of much speculation. But the calculation of these secondary stresses is extremely tedious by any existing method and in consequence they have rarely been ascertained with any degree of accuracy. The first real attack on the problem was made by Manderla in his Munich Polytechnic prize essay–“ The Calculation of Secondary Stresses which Occur in Simple Trusses ”–published in 1880 in Allgenieine Bautzeitung.