Correspondence on A Simplified Method for Evaluating the Natural Frequencies and Corresponding Modal

This paper deals with the various factors that affect the racking resistance of timber framed panels. The principal factors are the sheathing materials, the extent of vertical loading, the length of the panel, openings, holding down and the nail spacing. Other factors are generally of lesser importance. Test results relating to these factors are analysed, and a relationship is derived for each factor. The effects of outer claddings and inner linihgs are discussed very briefly. A simple design method for calculating the allowable racking resistance of panel assemblies is suggested. R.A. Robertson and D.R. Griffiths

This month's letters discuss foundations in shrinkable ground and highlight a survey on structural optimisation in practice.

Shalini Jagnarine-Azan describes how the impact of a heating planet is already being felt by islands in the Caribbean, and discusses the challenges of trying to build back more resiliently following a disaster.