As for all other building materials, a critical aspect of wood structures is the manner by which members are connected. Wood products are building materials which are easily drilled, chiseled, or otherwise shaped to facilitate the connection of members, and a number of methods and a wide range of products are available for connecting wood.
The installation of metal fasteners is the most common method of connecting wood products and a wide range of hardware is available. These range from the nails and the light connectors used for light framing construction to the bolts, side plates and other hardware used for heavy member connections. Each type of fastener is designed to be used with a particular type of construction. When used appropriately, metal fasteners provide means of connection which are easy to install and which offer trouble free performance.
Nailing for example, which is a basic means of connection with which everyone has some degree of familiarity, is an effective means of connection which, when applied according to specified layouts, results in strong structural systems which perform well under the most adverse loading conditions such as the effects of earthquake.
The performance of metal fastener connections is based upon the fasteners being large enough to carry and transfer loads over a large enough area of the wood so that the wood fibre in contact with the fastener is not deformed.Spacing and load arrangement considerations for metal fasteners are shown in Figure 5.1 below.
Timber joinery is a traditional method of connecting wood members without the use of metal fasteners. Although the use of metal fasteners for connections is almost universal, timber joinery still offers a unique visual appearance exhibiting a high degree of craftmanship.
The cellular structure of wood and modern chemistry combine to produce glue bonds between wood members which are as least as strong as the wood fibre itself. For this reason, adhesives play a crucial role in the manufacture of wood products such as plywood and parallel strand lumber (PSL). They are also used structurally, for example, in improving the performance of floor assemblies.
For many applications, such as nailing for frame wall construction, metal fasteners serve only a structural purpose, and will be hidden from view by interior and exterior finishes. In other cases where wood members serve a structural purpose and are left exposed to add visual interest to a ddesign, as much thought must be given to the appearance of connections as to the selection and finishing of the wood products themselves.
Where metal fasteners are exposed to view, the designer will in some cases will want them to be as inconspicuous as possible. This can be done by selecting fasteners such as split rings and bolts (which are effective means of transferring loads), by reducing the visual impact of hardware such as steel side plates by recessing them into the wood members, or by using painting to reduce prominence. In other cases, it may be desired to highlight the hardware to give a robust appearance to a structure.