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PRECAST CONCRETE CULVERTS – TECHNICAL DATA (PDF)

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					     PRECAST CONCRETE CULVERTS – TECHNICAL DATA

     Introduction
     Infraset design and manufacture high quality, high performance factory engineered precast concrete culverts for use in a wide range of
     modern construction and civil engineering projects.

     The company expertise combined with modern manufacturing facilities and years of experience enables Infraset to offer an extensive
     range of standard culverts as well as the manufacturing of non standard, project specific culverts.

     In addition to their exceptional load bearing capabilities and structural stability, precast concrete culverts require very little or no
     maintenance at all to exceed the useful life.


     CLASSIFICATION OF CULVERTS
     Types of culverts
     Infraset offers the full range of S-Class rectangular portal culverts readily available in lengths of 1.2m. Culverts ranging in size from
     450mm x 450mm up to 3600mm x 3000mm with Butt-joints are manufactured to the relevant S-Class strength requirements. All
     S-Class portal culverts bear the SANS mark and are designed, manufactured and tested in accordance with SANS 986:2006: Precast
     reinforced concrete culverts. Reinforced concrete bases are available for all S-Class culverts and are easily installed on site to complete
     a structurally stable engineered unit.

     SAR rectangular portal culverts manufactured to Spoornet loading, NR 1983, have thicker deck and leg sections to accommodate
     larger fill heights and imposed loads. Culverts ranging in sizes from 900mm x 450mm up to 3000mm x 3000mm are manufactured
     and unit lengths ranging from 1.2m up to 1.5m as stated in the product tables. SAR culverts are available in 2 strength classes, 0-5m
     fill and 5-10m fill. Reinforced concrete bases are available for SAR culverts being placed where the fill height does not exceed a
     maximum of 5m.

     Ribbed skew haunch culverts are designed and manufactured to withstand C-Class loading conditions, consisting of a vertical proof load
     of 150kN/m and a horizontal proof load of 30kN/m. Ribbed culverts range in size from 600mm x 450mm up to 3000mm x 3000mm
     and vary in unit length as shown in the product tables.

     Infraset also manufacture jacking box culverts in various sizes and in standard lengths of 1.190m which are manufactured with bolt
     holes for longitudinal ties.


     Strength of culverts
     Precast portal culverts are classified in terms of their crushing strength when subjected to a combination of loading cases involving vertical
     and horizontal knife edge tests conducted under factory conditions. The proof load test can be defined as a line load that a culvert must
     resist without the development of crack widths exceeding 0.25mm over a length of 300mm or over two adjacent ribs in ribbed 16
     culverts. When required, ultimate load test are also carried out to a magnitude of 25% greater than the applicable proof loads.

     There are three different loading configurations that are applied to precast portal culverts to simulate the installed conditions, namely
     the deck bending moment, deck shear and the inner leg bending moment. The inner leg bending moment is only taken into consideration for
     the S-Class portal culverts.




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PRECAST CONCRETE CULVERTS – TECHNICAL DATA

Loads on culverts
S-Class portal culverts are tested to a vertical proof load which is a function of the strength class multiplied by the span of the culvert,
a horizontal proof load of 30kN/m applied to the top of the leg and a horizontal leg load applied at a height 0.2 times the height
of the leg measured from the bottom of the leg for culverts with a height to span ration of more that 0.5. The horizontal leg load is
determined by the vertical load multiplied by the relevant factor.


Load classifications
     Culvert          Culvert           Vertical         Horizontal      Horizontal Leg    Horizontal Leg
      Span             Class           Proof Load        Proof Load       Load Factor       Load Factor
                                         (kN/m)            (kN/m)        Span > Height     Span = Height
      450               200           200 x 0.450           30                0.2              0.45
      600               200           200 x 0.600           30                0.2              0.45
      750               175           175 x 0.750           30                0.2              0.4
      900               175           175 x 0.900           30                0.2              0.4
      1200              150           150 x 1.200           30                0.2              0.4
      1500              100           100 x 1.500           30                0.3              0.5
      1800              75            75 x 1.800            30                0.4              0.6
      2100              75            75 x 2.100            30                0.4              0.6
      2400              75            75 x 2.400            30                0.4              0.6
      3000              75            75 x 3.000            30                0.4              0.6
      3600              75            75 x 3.600            30                0.4              0.6



Example: A 1200 x 1200 150S Culvert must resist

Vertical
    Proof load = 150x1.200 =180 kN/m
    Ultimate load = 180 x 1.25 = 225 kN/m
Horizontal
    Proof load = 30 kN/m
    Ultimate load = 30 x 1.25 = 38 kN/m
Leg load (Span = Height)
    Proof load = 180 x 0.4 = 72 kN/m
    Ultimate load = 72 x 1.25 = 90 kN/m

SAR portal culverts are manufactured for installations under railway track and designed to take account of train track, ballast
and backfill load combinations as stated in the Spoornet Loading code of practice: NR 1983.

The fill height above the culvert, determines the strength class of the culverts. All SAR culverts are available in two strength
classes to suit either 0-5m or 5-10m fill height conditions.




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     PRECAST CONCRETE CULVERTS – TECHNICAL DATA


     Installation conditions
     The trench condition occurs when the culvert is placed into a trench cut into natural ground and then backfilled with suitable
     material.




                                                    Trenched installation


     In the embankment condition the culvert is installed at ground level and is backfilled with suitable material.




                                                 Embankment installation




                                                                       Temporary prop arrangement
                                                                       Note: For H>1.5m, provide horizontal props
                                                                       at 40% height above base during backfilling
                                                                       and compaction. One prop per precast
                                                                       concrete unit.
                      Culvert in precast base configuration




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