International Journal of Mechanical Sciences 41 (1999) 179—208 Experimental quasi-static axial crushing of top-hat and double-hat thin-walled sections M.D. White, N. Jones* Impact Research Centre, Department of Engineering, The University of Liverpool, Liverpool, L69 3GH, U.K. Abstract Quasi-static axial crushing tests have been carried out on thin-walled top-hat and double-hat mild steel spot-welded sections. Several post-test collapse modes were identified for the structures and the associated energy-absorbing characteristics have been examined and compared with previous tests. A new empirical equation is suggested for relating the structural effectiveness to the structural density of top-hat and double-hat sections.  1998 Elsevier Science Ltd. All rights reserved. Keywords: top-hat; double-hat; quasi-static; axial crushing; mild steel Notation A cross-sectional area of structure (2a#2b#4 f )t a width of top-hat or double-hat structure b depth of top-hat or double-hat structure C, D, E, F 500, 333, 250, 166 mm long top-hat specimens, respectively DH double-hat specimen E  energy absorbed during collapse e  crush efficiency f specimen flange size l specimen length P  mean crush load P  maximum crush load t specimen thickness TA tensile test specimen fabricated in the rolling direction of the parent material * Corresponding author. Tel.: 00 44 151 794 4858; fax: 00 44 151 794 4848; e-mail: njones@ mechnet.liv.ac.uk. 0020-7403/99/$ — see front matter  1998 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 0 - 7 4 0 3 ( 9 8 ) 0 0 0 4 7 - 2