SOLUTIONS FOR POST-TENSIONED SLABS - .Alga solutions for post-tensioned slabs ... Centered post-tension: the cables are placed in the mid of the section obtaining a uniformly compression

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  • LGASLAB SOLUTIONS FOR POST-TENSIONED SLABS

    ANTISEISMIC DEVICES | BEARINGS | EXPANSION JOINTS | POST TENSIONING SYSTEMS | STRUCTURAL REPAIR AND MAINTENANCE

  • Re-development of Michelin complex ex-area, Trento - Client: Trento Futura S.c.a.r.l.

    Alga solutions for post-tensioned slabs Technical evolution in the construction of post-tensioned slabs has been successfully developed over the recent years by incorporating post-tensioned tendons increasing design performance of the structures. The use of post-tensioned cables in slabs has many direct and indirect advantages:

    Direct - Increased span relatively with slab loading - Increased loading relatively with slabs span - Reduction of slabs thickness - Reduction of slabs reinforcement - Reduction of slabs deformability

    EXPANSION JOINT

    SAVING AREA

    HEIGHT REDUCTION

    SAVING OF EXCAVATION

    WITHOUT EXPANSION JOINTS 60m 60m TYPICAL STRUCTURE WITH REINFORCEMENT STRUCTURE WITH POST-TENSIONED CABLES

  • Indirect - Reduction /elimination of the expansion joints - Reduction /elimination of concrete cracks due to reactions of tensioning, increasing durability of structures - Reduction of columns number - Reduction of the vertical loads and foundation size - Reduction of the seismic mass - Quick removal of formwork - Increased effectiveness of sealing (cracks restraint) The cables can be used for any type of construction such as small buildings, office facilities having large span slabs, parking areas at malls, even small or large industrial facilities. The post-tensioning system can be adopted to meet the demands of high performance slab design. Two possible solutions can be adopted: bonded strand cables or un-bonded cables (also called sliding cables). 1. The solution of bonded cables provides the placement of cables inside steel corrugated sheaths installed in the slab before casting. After the completion of tensioning process, the sheaths are grouted using cement grout made of cement, water and suitable additive as per approved design mix grout. 2. The solution of un-bonded cables is utilizing greased and polyethylene (PE) coated strands by means of a polyethylene sheath surrounding the strand having thickness of about 1.5 mm. The filling of voids with grease between strand and sheath, ensures an adequate protection against atmospheric conditions. The PE cables are placed directly in the slab before casting. The selection of the type of strand cables (bonded or un-bonded) depends on the demands of the design approach.

    Post-tensioning of slabs: Centered post-tension: the cables are placed in the mid of the section obtaining a uniformly compression. This type of solution is used in order to restrain the effects of concrete shrinkage, the cracks due to thermal variations (i.e. large industrial slabs with under floor heating) or even to reduce the joints of industrial pavements and increase the resistance to bending. Post-tension with elevation geometry profile variations: commonly adopted solution for post-tensioned beams, where the elevation of the cable varies and guarantees a moment of resistance absorbing the effects of bending loads. The dimensioning of post-tensioned slabs may provide different design approach according to customers requirements. One side or both sides tensioning can be utilized. The permanent or accidental loads can be compensated totally or partially only. The solutions are very flexible and can meet any technical requirement. Alga provides post-tension cables for cast-in-situ slabs. The anchorages proposed by Alga ranges from single-strand (monostrand) anchorages to multi-strands anchorages. Alga slab tendons are proposed in both versions with bonded or un-bonded strands. All anchoring systems are tested in accordance with the current and valid norms and approved as per European legislation ETAG013. Algas anchorages are applicable for the use of strands diameter ranging from 0.5 to 0.6S as per below tables.

  • BARESTRAND(BONDED)

    Diameter

    Norm Nominaldiameter

    [mm]

    Nominal Area

    [mm2] fptk

    [N/mm2] fp(1)k

    [N/mm2]

    Weight [kg/m]

    Breaking load [KN]

    T13 EN 10138 12,5 93 1670 1860 0,73 173 T13S EN 10138 12,9 100 1670 1860 0,785 486 T15 EN 10138 15,2 140 1670 1860 1,09 269

    T15S EN 10138 15,7 150 1670 1860 1,172 279 T15C EN 10139 15,2 165 1670 1860 1,29 307

    UNBONDEDSTRANDWITHPEDUCT&GREASE

    Diameter

    Norm Nominal diameter

    [mm]

    Nominal diameter with sheath thickness

    1,5mm

    Nominal- Area [mm2]

    fptk [N/mm2]

    fp(1)k [N/mm2]

    Weight[kg/m]

    Breaking load [KN]

    T13 EN 10138 12,5 16 93 1670 1860 0,83 173 T13S EN 10138 12,9 16,4 100 1670 1860 0,89 486 T15 EN 10138 15,2 18,7 140 1670 1860 1,21 269

    T15S EN 10138 15,7 19,2 150 1670 1860 1,305 279 T15C EN 10139 15,2 18,7 165 1670 1860 1,41 307

    SINGLE-STRAND TENDONS (MONOSTRAND) The single strand tendon (monostrand) consist of a cast-iron element (anchorage) having an internal conical shape for nesting the strand locking wedge and a proper shape to transfer the tension loads into concrete. The anchoring unit is equipped with accessories for the proper connection between sheath and anchorage by ensuring also strands protection.

    Two holes for fixing purposes of casting units to the formwork are foreseen ensuring recess proper casting and allowing tensioning operations. The fixed anchoring is usually achieved by locking the wedge inside the conical shape of casting unit and sealing the strand using a screwed protective cap.

    Single strand fixing detail in formwork Preassembled cables having a fixed head

    Cables prior of casting Single strand cables prior of tensioning

  • g asso

    97

    35,5

    70

    A

    G1

    G2

    B

    G

    SINGLE-STRAND (MONOSTRAND) ANCHORAGE (type 1F13 / 1F15)

    LIVE ANCHORAGE DEAD ANCHORAGE water-tight connection

    filling mortar

    protective cap

    connecting tube coupler

    locking wedge

    spring

    grease 144

    22

    47 64

    cup for recess

    130 STRESSING ANCHORAGE (type F)

    injection tube

    cast-iron unit 50

    70 in aggressive environment

    MULTISTRAND CABLES PREFABRICATED

    WITH FIXED PRE-ASSEMBLED ANCHORAGE Multi-strands cables consist of a cast-iron element (anchorage) having internal conical shapes for nesting the strand locking wedges and a proper shape to transfer the tension loads into concrete. The anchoring unit is equipped with accessories for the proper connection between sheath and anchorage by ensuring also strands protection. Two holes for fixing purposes of casting units to the formwork are foreseen ensuring recess proper casting and allowing tensioning operations. All the anchorages are available in types for use with bonded strands.

    cup for recess

    coupler

    C H

    flat duct

    A 3F

    A 4F

    A 5F

    DIMENSIONS A B

    C

    G

    H G1 X G2

    A 3F 13 85 180

    163

    95

    190 58 X 21

    A 4F 13 85 230

    163

    95

    240 58 X 21

    A 5F 13 85 270

    163

    95

    280 75 X 21

    A 3F 15 85 190

    163

    95

    200 58 X 21

    A 4F 15 90 230

    163

    100

    240 75 X 21

    A 5F 15 95 270

    163

    105

    280 91 X 21

    grease

    AN

    CH

    OR

    AG

    E

  • A

    NC

    HO

    RA

    GE

    DIMENSIONS

    A

    B

    C G H

    A 3F 13

    85

    180

    163 95 190

    A 4F 13

    85

    230

    163 95 240

    A 5F 13

    85

    270

    163 95 280

    A 3F 15

    85

    190

    163 95 200

    A 4F 13

    90

    230

    163 100 240

    A 5F 13

    95

    270

    163 105 280

    L1

    T13:

    150

    / 2

    00 /

    250

    B

    100

    T15:

    225

    / 3

    00 /

    375

    A

    G

    ANCHORAGES FIXED (type NE) ANCHORAGES FIXED (type G)

    injection pipe injection pipe

    strands grip

    connection

    sealant

    flat duct

    bulb

    connection

    sealant

    flat duct

    300 / 300 / 400 W

    950 W

    Steel plate 80 80

    55 55 55 55 55 55 55 55

    260 260

    Values of L1 & W are only for anchorages of 3, 4 & 5 strands respectively

    MULTI-STRAND ANCHORAGES (type F)

    filling mortar

    A 3F

    A 4F

    70 in aggressive environment

    fixing plate