: A series of tests has been conducted on twelve, short span, slender plate girders to investigate their ultimate resistance to shear, patch and combined shear and patch loading. Comparison of the experimental ultimate resistance of the test girders to combined shear and patch loading, with experimental results for shear and patch loading applied independently, indicates significant interaction between the two forms of loading. Theoretical predictions of the ultimate resistance of slender plate girders to independently applied shear and patch loading, based on existing theories and formulas, show close correlation with the test data presented herein. However, existing interaction formulas, based on tests on trapezoidal beams and plate girders with corrugated webs, appear either unduely conservative or unsafe. Based on the present test data, an improved interaction formula is proposed.

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