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.
Span > Height
Span = Height
|450||200||200 x 0.450||30||0.2||0.45||
Leg load (Span = Height)
|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.
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|
|750||300||175 S||8.7||175 S||4.98|
|900||300||175 S||8.6||175 S||4.8|
|1200||300||150 S||7.1||150 S||4.1|
|1500||300||100 S||4.5||100 S||2.9|
|1800||600||75 S||3.3||75 S||2.4|
|2100||600||75 S||3.3||75 S||2.4|
|2400||600||75 S||3.2||75 S||2.4|
|3000||600||75 S||3.1||75 S||2.4|
|3600||600||75 S||3.1||75 S||2.4|
For higher fill heights, products can be specially designed.
Maximum Fill Heights
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 22.214.171.124 (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 126.96.36.199 (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
h = fill heights in metres
b = overall trench width or, if in an embankment, overall culvert width, in metres.
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.