Engineering and Construction

Individual members may be combined in a variety of ways to produce a more efficient compound section. Figure 15.15 illustrates the most common arrangements. In each case the concept is one of providing a compound member whose overall slenderness will be such that its load-carrying capacity will significantly exceed the sum of the axial resistances of the component members, i.e. for the case of Fig. 15.15(b) the laced strut will be stronger than the four corner angles treated separately.

The detailed rules contained in these clauses are essentially of two types:

(1) Covering construction details such as the arrangements for interconnection in a general ‘good practice’ manner
(2) Quantitative rules for the determination of the overall slenderness, limits necessary for component slenderness, forces for which the interconnections should be designed, etc.

BS 5400: Part 3 also contains specific rules for the design of:

(1) Batten struts
(2) Laced struts
(3) Struts connected by perforated cover plates
(4) Struts consisting of back-to-back components.

These are somewhat more detailed than those of BS 5950: Part 1, particularly in the matter of determining suitable design forces for the interconnections, i.e. battens, lacings, etc.

Fig. 15.15 Typical arrangements for compound struts: (a) closely spaced, (b) laced or battened