Modelling of timber diaphragms

Diaphragms are a critical element in the lateral load path of every structure. Their design should not be overlooked, especially for larger spans and taller buildings. This note provides guidance on the design of timber diaphragms using simple computer modelling, where the diaphragm is analysed as a membrane or shell element with an equivalent shear stiffness. Although it is acknowledged that computer modelling of the whole structure including the diaphragms is not a common approach and certainly not strictly necessary for regular buildings, horizontal and vertical irregularities often require a modal analysis of the whole structure, or the diaphragm may be too complex to be analysed with traditional methods. In addition,
computer modelling allows designers to determine load paths and deformations of the diaphragms, as well as determining the load demand on connections, panels and chords. The approach presented is based on a number of assumptions and simplifications, and although it might not be able to provide the most accurate answer, it allows a designer to assess the behaviour and performance of a diaphragm, and the potential need to refine their analysis if required.

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