Design Considerations

Axially loaded members have to satisfy the relevant design rules and requirements of EC5 [1], and the limit states associated with the main design effects for members loaded in this manner are given in Table 5.1. The equilibrium states and strength conditions relate to failure situations and are therefore ultimate limit states. The displacement condition relates to normal usage situations, however no guidance is given in EC5 regarding limiting criteria for this state. Where lateral instability of a member can occur, a limitation is set for the maximum deviation from straightness allowed and this is given in Section 10, EC5.

For strength-related conditions, the design stress is calculated and compared with the design strength modified where appropriate by strength factors and, to meet the code reliability requirements, when using the partial factor method the design stress must not exceed the design strength.

When members or structures are subjected to combined stresses, e.g. due to the combined effects of axial and bending actions, additional design effects will arise and the design requirements for such conditions are also covered in this chapter.

(a) Simple post

(b) Eccentrically loaded column

(a) Simple post

(c) Truss system

(b) Eccentrically loaded column

(c) Truss system

(d) Beam and post construction

(d) Beam and post construction

(f) Tree truss column

Fig. 5.1. Examples of columns, posts and a stud wall.

(e) Stud wall - multiple studs to carry higher applied loads

(f) Tree truss column

Fig. 5.1. Examples of columns, posts and a stud wall.

Table 5.1 Main design requirements for axially loaded members and the associated EC5 limit states

Design or displacement effect

EC5 limit states

Retention of static equilibrium (sliding, overturning, uplift)

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