Author: The Institution of Structural Engineers
31 August 2012
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The Institution of Structural Engineers
Moment distribution is a method by which statically indeterminate structures are analysed elastically. It’s based on the relative stiffness of elements that make up a structure and shifts bending moments from one section of the structure to another until they become balanced. Once this balance has been achieved, the forces and bending moments within the structure are modelled.
(This article was updated in October 2016 to reflect errata issued since its original publication.)
When analysing structures it is important to adopt a methodical approach wherever possible. By breaking down the structure into manageable portions, the complexity of the analysis is reduced and thus becomes easier to control and review. By adopting such an approach, a seemingly insurmountable task becomes a much more approachable one. This Technical Guidance Note is a good practice guide for analysing and designing structures. It explains how structures are given form, modelled, analysed and designed. Mention is made of the need to rationalise the analysis process, but not at the expense of an economic design.
Once the concept and scheme for a structure has been settled upon, the initial sizing of the elements that it is made up of commences. This Technical Guidance Note provides a set of hints as to how to initially size elements, prior to carrying out the detailed design. This process allows the engineer to gain an appreciation of the form of the structure and the changes that may be required if element sizes prove to be too onerous following this size estimation process. Access more Technical Guidance Notes through our series homepage .
This Technical Guidance Note focuses on the visualisation of structures. It is essential for structural engineers to be able to express their ideas clearly through their designs. Visualising structures in the appropriate way enhances the design process - not least because drawing the complex elements of a structure while carrying out calculations, can help to identify possible construction issues/problems at an earlier stage than may otherwise be possible. This guide explains two techniques that are commonly used to draw in three dimensions and thus aid the structural engineer in visualising the structures they design.All of the guides in this series have an icon based navigation system, designed to aid the reader.