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52

www.concrete.org.uk

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concrete

REINFORCEMENT AND ACCESSORIES

responsible for ensuring that the support can

perform.

Telescopic connectors are normally of

specific capacities, with the substantiating

design being provided by the manufacturers.

It is still necessary however to calculate the

load being carried by each connector in order

for correct selection to take place. Usually

the connector supplier will provide this

calculation.

Robustness

If the stair is required to provide a means

of escape, there should be a reasonable

probability that it will retain sufficient

integrity for this purpose if the building

becomes damaged by accidental loads. To

achieve this,UK regulations require that all

precast concrete stair landings are anchored

to the main structure,ie,tied to the stairwell

walls.Historically,methods used were often

quite complex,time consuming,and costly,as

well as relying on many site skills.Some were,

and remain,totally impractical (see Figure

5). In particular, ensuring the correct level of

pull-out bars from the wall into a screed is

difficult to achieve, especially with slipformed

walls. Such connections may be used, but

design responsibility must be spelled out.

With telescopic connectors, recent

developments in design allow robustness to

be achieved without recourse to additional

fixings into the wall. Positioning connectors

on three sides of the landing allow

justification that they provide anchorage in

all three axes, thus satisfying requirements.

Where geometry prevents this, it is possible

to achieve anchorage by using factory-

modified connectors with a factory-modified

recess and a dowelled connection.

Appearance

Where angles are used, they normally are

exposed, or even protrude below the soffit.

This entails making good and fire protection,

thus spoiling the line and the appearance

of the high-quality concrete (see Figure 6).

Again, it should be decided at the outset

whose package this work falls into.With

telescopic connectors, there is nothing on

show on the soffit, so architectural intent is

maintained (see Figure 7).

Hugebenefits

For smaller or low-rise projects, angles

may (if only for planning reasons) be the

easiest solution. For high-rise however, the

overall savings in time and cost from using

telescopic connectors show huge benefits.

It is important however that the use of

such connectors is agreed at the outset so

that all parties can build in their element

of costs and that wall recesses are suitably

incorporated. Large projects in particular can

benefit massively from their use (see Figure

8), where programme gains, on-the-job

practicalities and improved aesthetics will

provide most benefit.

Figure 9: View of a TSS

telescopic insert.

Figure 8: Southbank

Place, currently under

construction, uses

over 2000 telescopic

connectors.

Figure 7: Clean soffit achieved

with telescopic connectors.

With telescopic connectors, recent

developments in design allow robustness to

be achieved without recourse to additional

fixings into the wall.

Figure 6: Making good required

where angles are used.