Analytical approximation of the primary resonance response of a periodically excited piecewise nonlinear-linear oscillator J. C. Ji and Colin H. Hansen Department of Mechanical Engineering The University of Adelaide SA 5005, Australia Email: jcji@mecheng.adelaide.edu.au (JC Ji) chansen@mecheng.adelaide.edu.au (CH Hansen) Ph. +61 8 8303 6941 (JC) +61 8 8303 5698 (CH) Fax. +61 8 8303 4367 The short running headline: piecewise nonlinear-linear oscillator. The total number of pages: 30 pages The total number of figures: 5 figures.