Introduction

Columns can be formed using single sawn members or glued laminated sections or may be built up to form profiles that are structurally more efficient for the type of loading to be supported and/or are required to fit particular situations. The EC5 [1] design requirements for single member columns are discussed in Chapters 5 and 6 for solid and glued laminated sections respectively and the procedures used for built-up columns are addressed in this chapter.

Built-up columns are columns composed of two or more timber or wood product sections connected by adhesives or by mechanical fasteners (e.g. nails, screws, dowels, punched metal plates, etc.), enabling the combined section to function as a composite element. Such columns can provide higher strength than the sum of the strength of the sections acting alone. When adhesives are used, there will be no slip at the joints and the built-up column will be assumed to behave as a fully composite section however, with mechanical fasteners there will be some joint slip resulting in a reduction in the load-carrying capacity. Built-up columns can be constructed in a great variety of cross-sections, examples of which are shown in Figures 8.1 and 8.2, and are formed to meet special needs, to provide larger cross-sections than are ordinarily available, or purely for architectural applications.

The design procedure for built-up columns is given in Annex C of EC5 and the application of the design rules to composite sections as well as to spaced and lattice type columns are addressed in this chapter. The procedure covers built-up columns formed by gluing or by mechanical fixings.

The general information in 4.3 is relevant to the content of this chapter.

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