Abstract
A diagonal grid configuration is considered consisting of beams arranged in two parallel sets, equally spaced and usually interconnected at 90 degree and placed obliquely (usually at 45 degree with respect to the boundary lines. The diagonal grid has been used by one of the authors in a number of practical applications including steel flat roofs over petrol stations. During a feasibility study for structures of this type several different boundary conditions have been considered during the design and the detailed resulting stresses and deflections compared. The paper contains a comparison of 12 different boundaries of a diagonal grid.