SSAB : RRs270 pile size is suitable for replacing RR320 pile size - SSAB

RRs270 pile size made of S550 steel grade offers more lightweight and more sustainable alternative for RR320 pile size. In addition, the mechanical splices of RRs270 fasten the installation and lower the cost for splicing.

Use of S550 steel grade offers several benefits for steel piles. Higher steel grade means naturally higher resistance for pile. With steel piles, the buckling is often considered as phenomenon that lowers the resistance of the pile, but in reality, it usually is valid only with very soft soil conditions. Soil offers lateral support for pile and therefore use of higher steel grade offers more benefits with piles than with columns without such support.

Several benefits with RRs270 pile size

RRs270/10 has several benefits compared to RR320/10 pile size, for example:
- both RRs270/10 and RRs270/12.5 pile sizes can be manufactured as elements with mechanical RR splices and mechanically attached rock shoes
- weights of RRs270 pile sizes are clearly lower than the weights of comparable RR320 pile sizes, due this the handling of piles at site is easier
- smaller diameter and lower weight allow loading of more piles to one truck, this results in reduced emissions in transportation
- CO2 emission of RRs270/10 piles are 16.2 % lower than with RR320/10 and CO2 emission of RRs270/12.5 piles are 16.4 % lower than with RR320/12.5 thanks to reduced amount of steel

Comparison of design resistances

When calculating and comparing the structural buckling resistances and geotechnical resistances of RRs270 and RR320 pile sizes, it can be noticed that despite smaller size RRs270 has similar design resistances. An exception are the softest soils, where the buckling resistance is little lower due to smaller diameter of the pile.
Below are several comparison graphs for design resistances of RRs270 and RR320 pile sizes, when undrained shear strength of soil is considered. The resistance values are calculated with SSAB's RRPileCalc software. Calculations are done according to Eurocode design standards and national design guidelines of Finland, Sweden and Norway.

Comparison of design resistances for RRs270/10 and RR320/10 in Finland.

With undrained shear strength values over 3.8 kPa the buckling doesn't reduce the resistance of RRs270/10 pile size. In those situations, both pile sizes have similar design resistances.

Comparison of design resistances for RRs270/12.5 and RR320/12.5 in Finland.

With undrained shear strength values over 4.7 kPa the buckling doesn't reduce the resistance of RRs270/12.5 pile size. In those situations, both pile sizes have similar design resistances.

Comparison of design resistances for RRs270/10 and RR320 in Boverket projects in Sweden.

With design values of undrained shear strength over 6.6 kPa the buckling doesn't reduce the resistance of RRs270/10 pile size. In those situations, both pile sizes have similar design resistances.

Comparison of design resistances for RRs270/10 and RR320/10 in Trafikverket projects in Sweden.

With design values of undrained shear strength over 11.1 kPa the buckling doesn't reduce the resistance of RRs270/10 pile size. In those situations, both pile sizes have similar design resistances.

Comparison of design resistances for RRs270/12.5 and RR320/12.5 in Boverket projects in Sweden.

With design values of undrained shear strength over 6.2 kPa the buckling doesn't reduce the resistance of RRs270/12.5 pile size. In those situations, both pile sizes have similar design resistances.

Comparison of design resistances for RRs270/12.5 and RR320/12.5 in Trafikverket projects in Sweden.

With design values of undrained shear strength over 8.9 kPa the buckling doesn't reduce the resistance of RRs270/12.5 pile size. In those situations, both pile sizes have similar design resistances.

Comparison of design resistances for RRs270/10 and RR320/10 in Norway.

With undrained shear strength values over 12.7 kPa the buckling doesn't reduce the resistance of RRs270/10 pile size. In those situations, both pile sizes have similar design resistances.

Comparison of design resistances for RRs270/12.5 and RR320/12.5 in Norway.

With undrained shear strength values over 16.3 kPa the buckling doesn't reduce the resistance of RRs270/12.5 pile size. In those situations, both pile sizes have similar design resistances.

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