Advanced Structural
Designs ACN 097 789 87
92 Vasey Cres CAMPBELL ACT 2612 Telephone
61612171
Facsimile 61612170 Email mal@structuraldesigns.com.au
What are
the pros and cons of stressing an in-situ concrete slab?
The main
advantages of prestressing are
Less overall building weight resulting in reduced material cost and
footing size.
Shallower beam sizes can lead to reduced floor to floor
heights and reduction in façade costs
Greater spans are possible, allowing greater fit out flexibility.
Tighter and more reliable deflection control is both possible and
economical.
The relatively waterproof nature of prestressed concrete provides a
superior barrier against water penetration over basement car parks and beneath
exposed slab edges.
The relatively
crack free nature of a prestressed structure provides increased protection to
the reinforcement and superior durability performance.
Stripping times are generally less, enabling economies in the use of
formwork.
Large unplanned penetrations can sometimes be accommodated in between
the stressing tendons without the need for trimming beams.
The strands are generally simple to locate prior to coring.
The deck prior to concreting is relatively uncluttered and safe to work
on.
The main
disadvantages are
The recess for the stressing live end at the ends of slabs and beams
needs to be carefully patched, generally in a two stage procedure if they are
to be texture painted.
When an off form edge finish is required or the structure edge is not
accessible pans are placed in the slabs which also require patching.
Unauthorised coring of the slab can seriously weaken the structure when
tendons are hit.
Overall building horizontal shortening is increased. If this shortening
is not planned for, it can lead to increased bending in columns and stress on
façade elements.
For very small projects (say less than 350m^2) stressing may be more
expensive.
For very short runs of cable (say less than 7m) stressing becomes
inefficient due to draw-in losses.
In the last
5 years in
If you have
a particular project in mind in Canberra ACT and need a structural engineer’s
opinion on the most economical framing option, call Mal Wilson from Advanced
Structural Designs (02) 61612171.