The photoelastic technique was employed to investigate the normal stress variation in elastic pinned-end portal rigid frames with deep members. Length to depth ratios were varied for both beams and columns.. Plastic models were loaded symmetrically by two equal concentrated loadm,. Photographs of stress pattern in the frame were used to evaluate the stresses. Also an analytical solution was obtained by using virtual work with the distance between center lines as the effective spalu EXperimental results and the results of the analytical solutions were compared and it was concluded that commonly used design methods are valid if the span-to-depth ratio is not smaller than 4 (center line span) or 3 (clear span). If the span-to-depth ratio is smaller than the above values, either experimental results or the ablutions based on elastic theory should be adopted as abatis for design.