General remarks

‘Strut-and-tie modelling’ is described in Section 7 of AS 3600-2009 (the Standard). Since the original issue of AS 3600 (1988), the current Standard is the first update in which a separate section is devoted to this type of modelling. This appendix serves to complement Section 7 of the Standard.

Figure D.1(1) shows some typical reinforced and prestressed concrete structures and elements. In terms of stress-distribution characteristics in response to external loads, each structure or element can be divided into the so-called ‘B’ and ‘D’ regions (Schlaich, Schafer & Jennewein 1987). In general, B regions are dominated by bending and D regions (the ‘distributed’ or discontinuous regions) are dominated by nonflexural stresses.

The analysis and design of various B regions have been extensively explored in most chapters of this book. That the strength behaviour of B (bending) regions can be accurately determined or designed for, using explicit formulas or well-prescribed analytical procedures, is beyond doubt. However, the same cannot be said of the behaviour of the D regions. For these, the analysis or design in general requires rather crude empirical formulas or, alternatively, the aid of sophisticated computer-based numerical procedures, such as the finite element method. The strut-and-tie modelling technique, on the other hand, can provide a direct design process for many types of D region.