Prestressed Concrete Floors

5,0mm wire and 9,3 and 12,5mm strand used.

The wire and strand is pretensioned to 70% of ultimate capacity prior to the 50MPa concrete being cast

Structural Details
Standard depths available: 120mm, 150mm, 170mm, 200mm and 250mm
Standard widths: 1 200mm
Non-standard widths: In 100mm increments
Min. concrete strength at detensioning: 35mPa for 120mm, 150mm, 170mm and 200mm deep slabs, 40mPa for 250mm deep slabs
Min. concrete strength at 28 days: 50mPa
Suggested max. span/depth ratio: L/50
Prestressing wire type: 5mm dia. triple indented low relaxation wire
Prestressing strand type: 9,53mm dia. stabilized strand
12,5mm dia. stabilized strand
Suggested bearings: On brickwork – 100mm
On steel – 75mm
On concrete – 75mm
Fire rating: 1 hour standard. Higher ratings are possible.
SELF WEIGHT AND FINISHES – Weight – Kg/m2
Depth of Slab: 120mm 150mm 170mm 200mm 250mm
Slab only: 222 253 275 306 358
Slab and Joint: 237 270 292 328 383
Slab, Joint & 40mm levelling screed: 337 370 392 428 483
SECTIONAL INFORMATION
Cross section area: 102,365 10e3mm2 Conc. 28 day strength 50N/mm2
Moment of inertia: 154.393 10e6mm4 Conc. strength at transfer 35N/mm2
Section modulus top: 2,549 10e6mm3 Mod. of elasticity of conc. 34kNm/m2
Section modulus bottom: 2,598 10e6mm3 Stressing of strand/wire 70%
Total breadth of webs: 468mm Check: stresses at transfer O.K.
Centroidal axis from bottom: 32,5mm Cover to steel 30,0mm
Core cover 25,0mm
STRUCTURAL INFORMATION Wiring Pattern
Moment & Shear Capacities: B C D E
Service moment: 20,66kNm/m 24,83kNm/m 27,44kNm/m 31.10kNm/m
Ultimate moment: 28,14kNm/m 37,73kNm/m 43,25kNm/m 50.38kNm/m
Ultimate shear resistance: 99,56kN 104,75kN 107,06kN 109.39kN
STANDARD WIRING PATTERNS
B = 12 x 5mm wires C = 9 x 5mm wires + 3 x 9.53mm strand
D = 7 x 5mm wires + 5 x 9.53mm strand E = 4 x 5mm wires + 8 x 9.53mm strand
LOAD CAPACITY TABLE Wiring Pattern / span
Live Load kN/m2 B / Span C / Span D / Span E / Span
0,75 5,5 6,2 6,5 6,8
1,5 5,1 5,7 6,0 6,4
2,5 4,6 5,2 5,5 5,9
4,0 4,1 4,7 4,9 5,2
5,0 3,8 4,4 4,6 4,9
7,5 3,3 3,9 4,1 4,3
10,0 3,0 3,5 3,7 3,9
SECTIONAL INFORMATION
Cross section area: 117.248 10e3mm 2 Conc. 28 day strength 50N/mm2
Moment of inertia: 286.517 10e6mm4 Conc. strength at transfer 35N/mm2
Section modulus top: 3.790 10e6mm3 Mod. of elasticity of conc. 34kNm/m2
Section modulus bottom: 3.851 10e6mm3 Stressing of strand/wire 70%
Total breadth of webs: 468mm Check: stresses at transfer O.K.
Centroidal axis from bottom: 32,5mm Cover to steel 30,0mm
Core cover 25,0mm
STRUCTURAL INFORMATION Wiring Pattern
Moment & Shear Capacities: B C D E F+2
Service moment: 29,94kNm/m 36,03kNm/m 39.83kNm/m 45.15kNm/m 51.51kNm/m
Ultimate moment: 38.50kNm/m 52.60kNm/m 61,64kNm/m 73,53kNm/m 86.03kNm/m
Ultimate shear resistance: 121.83kN 128.35kN 131.28kN 134.27kN 141.47kN
STANDARD WIRING PATTERNS
B = 12 x 5mm wires C = 9 x 5mm wires + 3 x 9.53mm strand
D = 7 x 5mm wires + 5 x 9.53mm strand E = 4 x 5mm wires + 8 x 9.53mm strand
F +2 = 12 x 9.53mm + 2x5mm wire (top)
LOAD CAPACITY TABLE Wiring Pattern / span
Live Load kN/m2 B / Span C / Span D / Span E / Span F+2 Span
0,75 6,2 7,2 7,6 7,8 8,6
1,5 5,7 6,7 7.0 7,5 8.0
2,5 5,2 6.1 6,5 6,9 7.4
4,0 4,7 5,5 5,8 6.2 6,6
5,0 4,4 5,1 5,5 5,8 6.2
7,5 3,8 4,5 4,8 5.2 5,5
10,0 3,5 4,0 4,4 4,7 4,9
SECTIONAL INFORMATION
Cross section area: 126.715 10e3mm2 Conc. 28 day strength 50N/mm2
Moment of inertia: 403.072 10e6mm4 Conc. strength at transfer 35N/mm2
Section modulus top: 4.715 10e6mm3 Mod. of elasticity of conc. 34kNm/m2
Section modulus bottom: 4.770 10e6mm3 Stressing of strand/wire 70%
Total breadth of webs: 468mm Check: stresses at transfer O.K.
Centroidal axis from bottom: 32,5mm Cover to steel 30,0mm
Core cover 25,0mm
STRUCTURAL INFORMATION Wiring Pattern
Moment & Shear Capacities: B C D E F+2
Service moment: 36.40kNm/m 44.06kNm/m 48.68kNm/m 55.16kNm/m 62.91kNm/m
Ultimate moment: 45.53kNm/m 62.35kNm/m 73.27kNm/m 88.72kNm/m 105.60kNm/m
Ultimate shear resistance: 136.4kN 143.34kN 146.73kN 150.21kN 158.407kN
STANDARD WIRING PATTERNS
B = 12 x 5mm wires C = 9 x 5mm wires + 3 x 9.53mm strand
D = 7 x 5mm wires + 5 x 9.53mm strand E = 4 x 5mm wires + 8 x 9.53mm strand
F +2 = 12 x 9.53mm + 2x5mm wire (top)
LOAD CAPACITY TABLE Wiring Pattern / span
Live Load kN/m2 B / Span C / Span D / Span E / Span F+2 Span
0,75 6,7 7,8 8,2 8,7 9,3
1,5 6.1 7,2 7.6 8,1 8,7
2,5 5,6 6.5 7,0 7,5 8,0
4,0 5.0 5,9 6.3 6,8 7,2
5,0 4,7 5,5 6,0 6,4 6,8
7,5 4,2 4,8 5,3 5,6 6,0
10,0 3,7 4,4 4,7 5,1 5,5
SECTIONAL INFORMATION
Cross section area: 141.325 10e3mm2 Conc. 28 day strength 50N/mm2
Moment of inertia: 626.385 10e6mm4 Conc. strength at transfer 35N/mm2
Section modulus top: 6.240 10e6mm3 Mod. of elasticity of conc. 34kNm/m2
Section modulus bottom: 6.287 10e6mm3 Stressing of strand/wire 70%
Total breadth of webs: 468mm Check: stresses at transfer O.K.
Centroidal axis from bottom: 32,5mm Cover to steel 30,0mm
Core cover 25,0mm
STRUCTURAL INFORMATION Wiring Pattern
Moment & Shear Capacities: B C D E F+2
Service moment: 46.48kNm/m 55.79kNm/m 61.61kNm/m 69.76kNm/m 80.64kNm/m
Ultimate moment: 55.47kNm/m 76.98kNm/m 90.73kNm/m 110.80kNm/m 137.75kNm/m
Ultimate shear resistance: 157.61kN 166.63kN 170.77kN 175.07kN 184.22kN
STANDARD WIRING PATTERNS
B = 12 x 5mm wires C = 9 x 5mm wires + 3 x 9.53mm strand
D = 7 x 5mm wires + 5 x 9.53mm strand E = 4 x 5mm wires + 8 x 9.53mm strand
F +2 = 12 x 9.53mm + 2x5mm wire (top)
LOAD CAPACITY TABLE Wiring Pattern / span
Live Load kN/m2 B / Span C / Span D / Span E / Span F+2 Span
0,75 7,2 8,4 9,0 9,6 10,3
1,5 6,6 7,8 8,4 8,9 9,6
2,5 6,1 7,1 7,8 8,3 8,9
4,0 5,5 6,4 7,0 7,5 8,0
5,0 5,1 6,0 6,6 7,1 7,6
7,5 4,5 5,3 5,8 6,3 6,7
10,0 4,1 4,8 5,2 5,7 6,1
SECTIONAL INFORMATION
Cross section area: 165.675 10e3mm2 Conc. 28 day strength 50N/mm2
Moment of inertia: 1143.163 10e6mm4 Conc. strength at transfer 35N/mm2
Section modulus top: 9.137 10e6mm3 Mod. of elasticity of conc. 34kNm/m2
Section modulus bottom: 9.154 10e6mm3 Stressing of strand/wire 70%
Total breadth of webs: 468mm Check: stresses at transfer O.K.
Centroidal axis from bottom: 34,5mm Cover to steel 30,0mm
Core cover 25,0mm
STRUCTURAL INFORMATION Wiring Pattern
Moment & Shear Capacities: C D E G+2 H+2 J+4
Service moment: 77.07 kNm/m 85.03 kNm/m 96.27 kNm/m 118.87 kNm/m 127.18 kNm/m 141.96 kNm/m
Ultimate moment: 101.17 kNm/m 119.86 kNm/m 147.01 kNm/m 205.42 kNm/m 227.22 kNm/m 263.67 kNm/m
Ultimate shear resistance: 204.44 kN 211.64kN 217.16 kN 235.08 kN 238.96 kN 252.03 kN
STANDARD WIRING PATTERNS
C = 9 x 5mm wire + 3 x 9.53mm strand D = 7x 5mm wire + 5 x 9.53mm strand
E = 4 x 5mm wires + 8 x 9.53mm strand G+2 = 10 x 9.53mm strand + 2 x 12mm strand + 2 x 5mm wires (top)
H+2 = 8 x 9.53mm strand + 4 x 12.5mm strand + 2 x 5mm wires (top) J+4 = 4 x 9.53mm strand + 8 x 12.5mm strand + 4 x 5mm wires (top)
LOAD CAPACITY TABLE Wiring Pattern / span
Live Load kN/m2 C / Span D / Span E / Span G+2 / Span H+2 / Span J+2 / Span
0,75 9,2 10,0 10,8 12,0 12,4 13,0
1,5 8,6 9,4 10,1 11,2 11,6 12,2
2,5 7,9 8,6 9,4 10,4 10,8 11,4
4,0 7,2 7,8 8,5 9,5 9,8 10,4
5,0 6,8 7,4 8,1 9,0 9,3 9,8
7,5 6,0 6,5 7,2 8,0 8,3 8,8
10,0 5,5 5,9 6,6 7,3 7,6 8,0

All loose material is to be removed from the tops of the slabs. The slabs should be thoroughly wetted and screed applied immediately. The levelling screed should comprise a 1:4 mix by volume of cement and clean river sand. Water should be added to the mixture to an extent that the mixture is relatively dry but remains easy to float finish. The screed should be laid to an approximate thickness of 40mm. Note that in some areas additional screed may be necessary to level out the camber in the units. After laying the screed it should be steel floated and then wetted for 48 hours to prevent shrinkage cracks.

In certain areas, namely balconies, roofs, walkways, tiled areas, car parks and areas where the screed is to be left unfinished, the screed specifications change slightly. On balconies, roofs, walkways etc., i.e. all areas where Echo Prestress slabs are exposed to the elements – a Ref. 100 mesh* must be placed in the leveling screed to counteract the transverse forces created by large temperature differences.

Where tiles are to be used on the slab, a Ref. 100 mesh* must be placed in the levelling screed as for balconies, roofs and walkways. Expansion joints should be allowed in the tiles every 3 metres and particularly where the section alters shape such as doorways. It is recommended that a flexible tile adhesive be used. TAL (Pty) Ltd. have produced a technical specification for tiling on Echo slabs which is available on request from Echo Prestress.

On car parks a Ref. 193 mesh** must be placed in a structural topping of not less than 50mm thickness to help spread the load from one panel to the next. The screed can be left rough to suit the clients requirements.

In areas with exposed screed a Ref. 100* mesh is required to control shrinkage/drying stresses. These areas would also require adequate movement joints.

Where the screed thickness is 50mm or less the mesh should be laid flat on top of the slab and the screed placed on top. Where the screed depth exceeds 50mm the mesh should be placed 20mm from the top surface of the screed.

Providing the above procedures are followed, the screed will adhere extremely well to the prepared surface of the slab. Experience has shown that it is impossible to remove the leveling screed from the top surface of the slab after a few days.

* A ref. 100 mesh is a 4,0mm wire in a square pattern at 200mm centres.
** A ref. 193 mesh is a 5,6mm wire in a square pattern at 200mm centres.

Specifications for the following are available from Echo prestress on request:

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