Bracing for non-domestic timber trussed rafter roofs

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Timber trussed rafters are light-weight structural components which are widely used as an economical means of roof framing.

This guidance document provides information for use by designers to justify the extension and possible modification of extrapolations from the guidance provided in BS 5268-3 for bracing of domestic scale trussed rafter roofs, although the information also has a bearing on meeting wind bracing and robustness requirements.

An overview of alternative design methods for non-domestic roof bracing is also provided with illustrative design examples. Practicability issues and resolution of conflicting codified recommendations concerning fixing of bracing are also addressed.

Contents:

  • Introduction
  • The relative stiffening effect of progressive degrees of bracing
  • Contribution of roof covering materials
  • Ceiling level stiffness
  • Behaviour of roof with respect to number of trusses
  • Roof behaviour beyond serviceability levels
  • General comments on roof behaviour
  • Roof construction quality
  • Bracing connections
  • Summary of bracing design methods
  • Other aspects of roof construction in relation to effective bracing
  • Design examples
  • Example 1: Bracing design formulae for trussed rafter roofs
  • Example 2: Ceiling plane bracing design for a roof with no ceiling boards

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