Raised collar roof trusses
During the correspondence on this subject, introduced by Mr R. 0. C. Seaman on 18 December last, doubts have been expressed by some of our correspondents (Mr Seaman on 18 December, Owen Hope on 16 April, and Mr D. E. Clark on 18 June) on whether present practice adequately takes into account the effects of spread deflections and resisting forces introduced at the supports of trusses of this type. On 19 February Frank Hall drew attention to the guidance given by the International Truss Plate Association in restricting the recommended horizontal spread deflection of ‘raised tie trusses’ to 12mm, and to a Technical Bulletin of the Association justifying such a limiting deflection as acceptable with respect to its effect on masonry walls. Mr Clark, in his contribution, questioned the basis for this guidance. We now hear from Dr. Luke Whale, of Gang-Nail Systems Ltd. in Aldershot, in which he elaborates on the guidance quoted by Mr Hall:
Having read the latest correspondence on this topic, I must confess to a feeling of great frustration over the nature of the comments made.