INTL - EN • 01|21 • 4th edition
HOW TO COBIAX
Contact: Heinze Cobiax International GmbH Eupener Straße 35 32051 Herford Germany international@cobiax.com
HOW TO COBIAX The Quick Guide to Cobiax SL and Cobiax EL
Global Contact: info@cobiax.com
cobiax.com
Introduction This Quick Guide is designed to give you a short introduction to the Cobiax technology. Additional information is available upon request or as a download from cobiax.com.
Cross section view
h d,min ≤ h d ≤ h d,max
Method 1 In-situ casting
h u ≤ h d - (c nom,o + h bew,o + c i,o + c nom,u + h bew,u + c i,u ) e = Center distance of void formers
Cobiax SL hd
hu 1 st Layer
We strongly recommend the use of our free Cobiax software tool Quick & Light. Our sales personnel will also be happy to answer
Solid zone
your questions.
Zone with void formers e = Center distance of void formers
Cobiax EL
Method 2 Semi-prefabricated elements
Technology and products
Zone with void formers
e = Center distance of void formers
c nom,o h bew,o c i,o
Cobiax SL
hu h k OR h ks c i,u h bew,u h ft
S-Hooks
The resulting savings of up to 35% in concrete and weight has a positive effect on the construction of the slab itself (e.g. less deflection, larger
Solid zone
spans or thinner slab thickness) and hence on the whole building
Cobiax void former modules, which are internationally patented,
c i,u h bew,u c nom,u
Für (h bew,u + c i,u ) ≥ c ft,min h u ≤ h d - (c nom,o + h bew,o + c i,o + h ft + h bew,u + c i,u ) UND h k ≤ h d - (c nom,o + h bew,o + c i,o + h ft ) Für (h bew,u + c i,u ) < c ft,min WITH SPECIAL FIXING ELEMENT h ks ≤ h d - (c nom,o + h bew,o + c i,o + h ft )
hd
structure.
c nom,o h bew,o c i,o
hu 1 st Layer
Solid zone
replace the heavy concrete inside a slab where it is not required.
c i,u h bew,u c nom,u
hd
Cobiax SL (Slimline): for slab thicknesses from 22 up to 50 cm Cobiax EL (Ecoline): for slab thicknesses from 40 up to 70 cm
Cobiax technology uses recycled lightweight plastic void formers to
c nom,o h bew,o c i,o
Zone with void formers e = Center distance of void formers
Cobiax EL hd
c nom,o h bew,o c i,o hk hu
S-Hooks
consist linear fixing elements (FE) made from steel reinforcement
c i,u h bew,u h ft
fitted with void formers made of 100% recycled postconsumer plastic. Solid zone
Zone with void formers
Design and detailing
of punching shear it is necessary to check whether the solid zone extends beyond
A Cobiax voided slab can be designed and planned by any
the critical circular cross section or the last row of shear links by at least the
structural engineer in compliance with the local building
dimension 2d . Otherwise the solid zone must be enlarged accordingly. Additionally,
code and standards. Cobiax has achieved the General
a solid zone must be provided along linear supports with a width equal to at least
German Technical Approval according to Euro Code 2:
the centre distance e of the void formers. At the free edge of a slab a solid zone with the width of h d has to be provided.
1. Slab cross-section and design parameters After estimating the slab thickness h d , a suitable Cobiax void former module (support height h u respectively total height of fixing element h k or h ks ) is selected, taking into account concrete cover c nom , the rebar layers h bew and any interme-
3. Second run of structural calculation The dead load and if necessary, the bending stiffness are adjusted (back to full dead load and stiffness) in the solid zones without void formers and a second, final run of structural calculation has to be done.
diate layers c i (e.g. for additional spacers or concrete core thermal activation) and if necessary, the thickness of the semi-prefabricated element h ft . Additional require-
min e
ments for the fire resistance have to be taken into account if necessary.
min h d
Support
The load reduction of void formers, the associated stiffness factor for the bending stiffness f EI and the shear resistance factor f V (or the reduced shear resistance
V Rd,c,cobiax = f V · V Rd,c ) can be found in the table on the next page.
Free edge of slab
V Rd,c,cobiax
Alternatively the free software tool Quick & Light can be used for quick preliminary
u + 2d
calculation.
2. First run of structural calculation The calculation of a Cobiax voided slab is to be done in similar manner as that of a conventional concrete slab, taking into account these 3 input parameters. With the first run of the structural calculation the load reduction and the reduced stiffness is applied for the whole slab.
Approx. 50% to 80% of the slab area is fitted with void formers (according to the different structural configuration)
4. Detailed design check Casting the concrete in two layers (to prevent uplift of the void formers) or the use of semi prefabricated elements requires a design detail check for the transfer of
A consideration of the shear forces leads to the determination of the required solid
horizontal shear forces in the joint between both concrete layers considering the
zones. Areas with V Ed > V Rd,c,cobiax must remain without void formers. In areas
reduced bonding area due to the void formers (see software tool Quick & Light).
Execution on site
done within a few hours, depending on the temperature, weather conditions and concrete properties. With the semi prefabricated solution with Cobiax modules
The contractor installs the Cobiax void former modules according to the Cobiax
installed on site (Method 2) uplift is prevented by tying the upper reinforcement to
layout drawing between the top and bottom reinforcement layers using a fixed
the lattice girders of the semi-prefabricated elements.
distance device (to ensure required minimum spacing). In-situ solution as well as semi prefabricated or prefabricated solutions are possible.
Cobiax can be combined for example with post tensioning or concrete core activation.
With the in-situ solution (Method 1) the void formers are usually secured against uplift by casting the concrete in two separate layers. After the first concrete layer (approx. 8 cm to 12 cm thick only in the area of the void formers) has hardened, the void formers are finally fixed and ready for the second layer of concrete. This can be
Cobiax SL Application data
Cobiax EL only available in Germany or on request