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Direct-reading design charts are presented for 75S-T aluminum-alloy flat compression panels having longitudinal straight-web Y-section stiffeners. These charts make possible the direct determination of the stress and all the panel proportions required to carry a given intensity of loading with a given skin thickness and effective length of panel.

Results are present for part of a test program on 24S-T aluminum-alloy flat compression panels with hat-section stiffeners. The results show the effect of the relative dimensions of a panel on the buckling stress and average stress at maximum load. Comparative envelope curves are presented to provide some indication of the relative structural efficiencies of hat- and Z-stiffened panels having a ratio of stiffener thicknews to skin thickness of one.

Summary: An experimental investigation is being conducted to determine the effect of varying the rivet diameter and pitch on the compressive strength of 24S-T aluminum-alloy panels with longitudinal Z-section stiffeners. The panels were selected on the basis of available design charts, and the panel proportions were limited to the region of these charts in which the panels have the closest stiffener spacings and the smallest values of width-to-thickness ratio for the webs of the stiffeners and have such length that failure is by local buckling. The results showed that for these panels the compressive strengths increased appreciably with either an increase in the diameter of the rivets or a decrease in the pitch of the rivets. Data are also presented from which the rivet diameter and pitch required to develop a given stress in the panels may be determined.