In this paper, pitched beams which can increase economical efficiency used in ship and land-based structures are introduced. Their behavior under both point load and distributed load is examined by the direct stiffness method in this study. The configuration of pitched beam is considered to be symmetric with two cases of boundary conditions, "pinned" and 'fixed', at ends. Also, the optimal pitch angle of a pitched beam is studied for each case.
In the optimization of structural design, one of the most important matters is to increase the economical efficiency. In the case of a flat beam, lateral load is resisted by the bending and shearing actions. Certainly axial stress is not generated in this situation. Also, shearing action is often neglected because of its magnitude is very slight as compared with the bending action. In the case of a pitched beam, as the pitch angle increases the axial stress is increased, while bending stress is decreased. Therefore a combination of these kinds of stresses contributes to reduce the total stress as occurred in the fiat beam. Thus the stresses and weight of pitched beams with different pitch angles under a point load and diNfibuted load can be investigated and optimized re~ectively. In addition, comparison of the stresses, weight and efficiency with a fiat beam is made. In the study, the direct stiflhess method is used as an analysis tool. A single point load is applied vertically on the apex and uniformly distributed load is applied along the span of the pitched beams. Boundary conditions at both ends are considered either "pinned" or • fixed'.
Beam Properties Consider a pitched beam has I-section which is symmetric as shown in Fig. 1.
