Civil Engineering Reference
In-Depth Information
Figure 3.26
Bond of bars and plates
3.11.6 Conclusions
Strut-and-tie analogy is more a philosophy than a method of calculation. It gives to
the designer a tool with which he can make sense of complicated actions, and fi nd a
rational organisation of reinforcement.
In complex areas where it may be diffi cult to decide on an arrangement of struts and
ties, it is often a good idea to run a fi nite element analysis fi rst. This will give a picture
of the direction of the compressive and tensile forces, and give clues to the strut-and-
tie pattern. It may also highlight areas where the concrete may be overstressed in
compression, and where strut dimensions need to be increased, perhaps by thickening
the concrete slabs or webs.
Using this analogy requires considerable expertise. The worst possible way of carrying
out the design of a complex structure would be to pass the task to an inexperienced
engineer armed with a fi nite element program. One criterion for deciding whether an
engineer is suffi ciently experienced to tackle a particular diffi cult piece of design is that
he should be capable of drawing up a strut-and-tie analogy for it.
For further information on the design of strut-and-tie analogies, see [9] and [10].
