The article presents a comparison of results of optimized calculation of a truss beam which was chosen as a combined construction. The results of calculation of a beam are compared using the method based on the properties of spacer systems and the calculation of the construction designed in LIRA software complex. The article is dedicated to verification of adequacy of the results of theoretical calculations of construction optimization. Values of longitudinal forces and bending moments appearing in a truss beam are chosen as convergence criteria. Two variants of construction loading are considered: a truss beam exposed to constant load only and a truss beam exposed to constant and temporary load. In the case under consideration, the minimum value (weight) of construction is an optimality criteria, variable parameters include beam panel length and camber height of a trussing rod. As a result, the construction will be considered optimal, if bearing and maximal (between the pillars) bending moments are equal in it. The result of verification of the obtained data is the value of error.