Ira. J. Impact Enang Vol. 13, No. 2, pp. 203-214, 1993 0734-743X/93 $6.00 + 0.00 Printed in Great Britain © 1993 Pergamon Press Ltd MAXIMUM STRENGTH OF SQUARE THIN-WALLED SECTIONS SUBJECTED TO COMBINED LOADING OF TORSION AND BENDING G. J. WHITE, R. H. GRZEB1ETA and N. W. MURRAY Department of Civil Engineering, Monash University, Melbourne, Victoria 3168, Australia (Received 3 September 1992; and in revised form 25 November 1992) Summary--A closed-hat section, thin-walled steel cantilever beam was subjected to (quasi-static) combined torsional and bending loads. Test procedures and results are described in the paper. Experimental results for two series of beams with different material thicknesses were used to derive interaction equations which predict the peak load capacity of the section for any combination of bending and torsional load. Such equations may prove to be a useful design tool for automotive designers when assessing the crashworthiness of roof pillars for rollover accidents. A Al A2 A~ b b~ C E f h /ha k L I M Mo Moc Mow P t tf T T~r~ T~a To Ye .Pp Yl Y2 v W u Ui % .o" k o'er O'y T T O "~jk NOTATION area of section area of section above neutral plane area of section below neutral plane enclosed area (b 2) width of hat section (excluding flanges) effective flange width cantilever length Young's modulus width of flange extension height of web of section second moment of area about the neutral axis buckling coefficient torsion arm length length of portion of section bending moment maximum bending moment in pure bending critical bending moment for buckling of compressive flange critical bending moment for buckling of web load applied to end of cantilever structure thickness of section thickness of flange extension torsional moment critical torsional moment for buckling of hollow square section critical torsional moment for buckling of flange extensions maximum torsional moment in pure torsion distance to elastic neutral axis from bottom flange distance to plastic neutral axis from bottom flange distance from neutt:al axis to centroid of area A I distance from neutral axis to centroid of area A 2 ratio of flange width to section width (f/b) Poisson's ratio ratio of stresses in upper and lower flanges elastic normal stress normal stress component in "x" direction normal stress component in "y" direction normal stress component in "z" direction critical buckling normal stress yield (normal) stress elastic shear stress shear stress in "xy" plane shear stress in "yz" plane 203