Discussion - Optimizing Roof Truss Installations with Body-Loaded Photoelastic Models – Neall, G. M., Haycocks, C., Townsend, J. M. and Johnson, L. P. – Technical Papers, MINING ENGINEERING, Vol. 30, No. 6, June 1978, pp. 660-666

The authors are to be complimented on using a novel and potentially helpful technique to analyze the effects of mine roof trusses. However, some criticisms of their application and analysis seem appropriate to further its acceptance. This discussion will deal with the normal structural analysis format covering: 1) material. 2) load, 3) structure, and 4) analysis. It will then briefly review the testing procedures and finally cover miscellaneous items. That the analytical and testing results admittedly disagreed by several orders of magnitude, indicates a need for improved understanding. The introduction of data determined previously was not assisted by references to "Interim" or "Preliminary" reports. This material should have been concisely reformulated for the open discussions that Transactions encourage. In addition, many important simplifying assumptions are tacitly made without recognition, and much less, an attempted justification.