The nonlinear behavior of single bay, single story frames composed of the castellated beams has been investigated by means of the finite element analyses of detailed models of sample frames under a combination of vertical and horizontal loads. The frames consisted of castellated beams of various lengths (number of castellation). At the same time, two different types of columns have been considered (battened columns as well as the solid web columns) and their lateral deflection behavior have been compared. In addition to the frames consisting of single castellated beams, frames with double castellated beams with the by-pass type of connections have also been studied. Both traditional and strengthened by-pass connections have been discussed. The effects of the initiation and penetration of plasticity, the formation of the vierendeel type of mechanism and the lateral — torsional buckling of the web-post have been investigated, in particular. A comparison of the results obtained from the finite element studies with the previous tests carried out by the first author, indicates close agreement, which demonstrates the effectiveness of the finite element analyses procedures adopted in the estimation of the nonlinear behavior of such frames.
)