Author: C. O'Regan (AECOM)
2 January 2019
First published: 2 January 2019
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C. O'Regan (AECOM)
These panels are quite slender to the point where they usually require additional horizontal support to make them stable. The same can also apply to cavity walls, where both skins are incapable of resisting lateral loads.
The element that provides this support to masonry panels is a vertical prop known as a ‘windpost’. Its principal role is to provide lateral support against destabilising horizontal forces that typically originate from wind pressure – hence, the name.
Windposts are typically steel elements – either open sections, such as channels or angles, or closed sections, such as rolled hollow rectangular sections. This Technical Guidance Note provides guidance on the design and detailing of windposts relating to their incorporation into building structures.
The design of timber posts follows the same principles as the design of vertical structural elements formed from other materials. Extreme fibre stresses or buckling due to applied axial forces are the key components affecting a post’s ability to perform. The major difference is the anisotropic nature of timber, which, for vertical elements, has a significant impact on the assessment of their performance as a structural member.
The design of timber elements in the UK, according to current codes of practice, is based on limit state theory. This Technical Guidance Note adopts this approach to describe the design of timber posts. The note assumes that the reader is familiar with the use of coefficient factors prevalent within BS EN 1995-1-1 (Eurocode 5), as described in Technical Guidance Notes Level 1, No. 18 Design of timber floor joists and Level 2, No. 14 Design of unrestrained timber beams.
Since the invention of medium-storey framed structures in the late 1800s, there has been a need to clad them with a reasonably robust material that acts as an efficient barrier to the external environment. Masonry delivers the performance required of a cladding system on multiple fronts. It has therefore developed from a load-bearing element within structures to become a component of an envelope to larger framed buildings.
This Technical Guidance Note introduces structural engineers to the interfaces between a primary structure that is principally formed from steelwork and a masonry cladding system.
This Technical Guidance Note addresses the design of timber elements that are unrestrained against lateral torsional buckling. It explains how such beams are analysed and designed. The impact of notching the supports of beams is also considered with respect to the shear capacity of the beam.
For clarity and brevity, this note only covers solid and glued laminated (glulam) timber elements; compound and composite beams, such as flitch beams, are not considered. The connections within timber frame assemblies will be addressed in a future note.
Readers should also be aware that this note forms part of a trio of Technical Guidance Notes leading to the design of bespoke timber trusses – assemblies made from unrestrained timber beams and posts. Notes on the design of timber posts and bespoke timber trusses will follow later in the series.