Reactions for the horizontal girders of vertical lift gates do not remain constant due to their fixity with skin plates and vertical stiffeners. After the evaluations of spacing of horizontal girders, based on the formulae given by Nigam [2] and Gupta et al [1], these should be analyzed to account for the effect of fixity to obtain design reactions. The design reaction is the maximum value of reaction obtained after considering the effect of fixity. In the present case a typical example has been considered to address the problem. From practical considerations the top and bottom girders may be made of lighter section and be disregarded in the stress calculation. The second girder coincides with the centre of gravity of the top strip, and the penultimate girder coincides with the centre of gravity of the bottom strip. It is concluded that consideration of the fixity effect is very significant in the computation of design reactions, and cannot be ignored. When a high head vertical lift gate, with skin plate and seals on its upstream, is opened with a small opening, a hydraulic jump forms downstream. This interferes with the bottom horizontal girder and gives excessive uplift at small openings which causes the problem in self closure of the gate. This aspect must be considered when evaluating the design reaction for this girder.
