5Structural Timber Frames

Structural timber frames are a popular choice for relatively low‐rise building of one to two storeys and increasingly popular for mid‐rise buildings (three to five storeys). More recently, structural timber frames have been used for buildings of up to nine and ten storeys high. The advantages of the structural timber frame are the speed of erection of the pre‐cut timber members and ease of fixing. Timber has inherent fire resistance and it is a sustainable material (carbon neutral). Structural timber frames may comprise seasoned timber, such as oak columns and beams, engineered timber components, or a mix of timber and engineered timber.

5.1 Functional requirements

The functional requirements of a structural frame are:

  • Strength and stability
  • Durability and freedom from maintenance
  • Fire safety

Strength and stability

The strength of timber varies with species and is generally greater with dense hardwoods than less dense softwoods. Strength is also affected by defects in timber such as knots, shakes, wane and slope of the grain of the wood. The strength and stability of a structural timber frame depends on the combination of elements, such as columns and beams and the rigidity of the connections. Simple calculations will help to establish the size of columns and beams. Connections tend to follow a tradition of using a combination of nails, screws and bolts. Factory produced assemblies will be joined by mechanical connections.

Stress grading of timber ...

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