Impact on Pin-Jointed Trusses: Fid-Bau Portal

Impact on Pin-Jointed Trusses

Boley, Bruno A. / Chao, Chi-Chang

A method is presented for the analysis of pin-jointed trusses subjected to impact. Expressions are derived describing the behavior of the various types of joints which may exist; with the aid of these, a numerical computation procedure is developed. This procedure makes use of “distribution factors,” dependent only on the joint geometry, to describe the relationship between the waves arising in the bars meeting at an unloaded joint. The analogous relationships at a loaded joint are determined with the aid of a finite-differences technique. The method suggested can be used whether impact is caused by a known pressure pulse or by collision with a solid object. The criterion for establishing the time at which impact ends is cited in detail for the latter of these cases. An illustrative example is presented for which stresses, deflections, and reactions are computed. The basic equations governing the behavior of the various joints are derived for three-dimensional trusses as well as plane trusses; the proposed method of analysis is equally applicable to both.