Technical Data

Aveng 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 Aveng 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

Aveng 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.

Aveng 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.

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
Span
Culvert
Class
Vertical
Proof Load
(kN/m)
Horizontal
Proof Load
(kN/m)
Horizontal Leg
Load Factor
Span > Height
Horizontal Leg
Load Factor
Span = Height
 
450 200 200 x 0.450 30 0.2 0.45

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

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 0.5
1500 100 100 x 1.500 30 0.3 0.6
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

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.

Installation conditions

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

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

Please see images.

Maximum Fill Heights on Culverts

Culvert Size Foundation conditions
Span Height 1 and 2 3 and 4
(mm) (mm) Class Fill (m) Class Fill (m)
600 300 200 S 10.2 200 S 5.6
600 450 11 6
600 600 12 6.4
           
750 300 175 S 8.7 175 S 4.98
750 450 9.2 5.2
750 600 10 5.5
750 750 10.5 5.8
           
900 300 175 S 8.6 175 S 4.8
900 450 9 5.1
900 600 9.5 5.3
900 750 10 5.6
900 950 10.2 5.8
           
1200 300 150 S 7.1 150 S 4.1
1200 450 7.4 4.3
1200 600 7.7 4.4
1200 900 8.2 4.7
1200 1200 8.8 5
           
1500 300 100 S 4.5 100 S 2.9
1500 450 4.7 3
1500 600 4.9 3.1
1500 900 5.3 3.3
1500 1200 5.6 3.5
1500 1500 6 3.7
           
1800 600 75 S 3.3 75 S 2.4
1800 900 3.6 2.5
1800 1200 3.8 2.7
1800 1500 4 2.8
1800 1800 4.3 2.9
           
2100 600 75 S 3.3 75 S 2.4
2100 900 3.5 2.6
2100 1200 3.7 2.7
2100 1500 3.9 2.8
2100 1800 4.1 2.9
2100 2100 4.3 3
           
2400 600 75 S 3.2 75 S 2.4
2400 900 3.4 2.5
2400 1200 3.5 2.1
2400 1500 3.7 2.9
2400 1800 3.8 2.8
2400 2400 4 3
           
3000 600 75 S 3.1 75 S 2.4
3000 900 3.2 2.5
3000 1200 3.3 2.6
3000 1500 3.4 2.7
3000 1800 3.5 2.7
3000 2400 3.7 2.9
3000 3000 3.1 2.7
           
3600 600 75 S 3.1 75 S 2.4
3600 900 3.1 2.5
3600 1200 3.2 2.6
3600 1500 3.3 2.6
3600 1800 3.3 2.7
3600 2400 3.5 2.8
3600 3000 3.5 2.7

For higher fill heights, products can be specially designed.

 

Maximum Fill Heights

Definitions

Yielding foundation conditions occur when the founding material and the fill material are expected to settle at equal rates (compressible material). The loading is calculated in accordance with TMH7 Part 2 clause 2.3.3.2 (2).

Unyielding foundation conditions occur when the founding material is incompressible (soft rock or harder material). The loading is calculated in accordance with TMH7 Part 2 clause 2.3.3.2 (3) and (4).

Trench condition occurs when culverts are laid in a narrow excavation and backfilled to ground level.

Embankment (untrenched) condition occurs when culverts are laid at ground level and backfilled to final formation level.

The combinations of foundation and installation conditions used in TMH7 are defined as:

Condition 1: Culverts in trench on unyielding foundation with no projection

Condition 2: Culverts in an embankment on yielding foundation

Condition 3: Culverts in an embankment on yielding foundation for h>1, 7b

Condition 4: Culverts in an embankment on unyielding foundation for h<1, 7b

Where:

h = fill heights in metres
b = overall trench width or, if in an embankment, overall culvert width, in metres.

 

Assumptions

The following assumptions and clauses of TMH7 Parts 1 and 2 were used to compile the table above:

  • A minimum fill height of 300mm over the culvert units. Where this cannot be achieved, a 100mm reinforced concrete slab must be used
  • Standard traffic loading SNABC
  • Fill material unit weight 20kN/m³
  • Concrete unit weight 24kN/m³
  • Horizontal earth pressure 7,8kN/m² per metre depth
  • Ultimate Limit State Load factors.

Technical Data 

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