Street Light Foundation Design Spreadsheet

Street Light Foundation Design

The detailed process of street light foundation design is seldom completed in the UK for new street lights. This is due to the fact that standard planting depths, manufacturer's standard details and historical foundation designs are often used to save time. In many cases where standard street lights are to be installed in normal ground conditions these procedures will produce a satisfactory design. However for more complex or unusual applications a fully detailed street light foundation design will produced. The standard designs are also always conservative. Where large lights are planned or where a large number of street lights will use the same design, the conservative approach can become seriously uneconomical. Indeed the CivilWeb Street Light Foundation Design spreadsheet makes completing a full design so simple and quick that a fully detailed foundation design is almost always justified.

Firstly the spreadsheet calculates the wind loading acting on the street light. This is done either using the simplified procedure contained within BS PD 6547 or through a full analysis using BS EN 1991-1-4. The simplified analysis is useful where the site information available to the designer is very limited and for quick feasibility or preliminary designs. The more detailed procedure in BS EN 1991-1-4 provides a much less conservative loading and requires only slightly more detailed site knowledge. Generally it is recommended that a full analysis is undertaken except where the required information cannot be easily acquired.

The spreadsheet takes this wind loading information and uses this to model the forces produced in the street light and foundations. Two foundation types are common, planted columns where the street light column is installed into a hole in the ground and encased in concrete, or concrete pad foundations where the street light column is bolted onto a concrete pad foundation which resists the forces by bearing onto the ground.

Planted columns are very common. There are minimum depth requirements given in HA HD94/17 which are often used as design values. In many cases the minimum depth is not sufficient and the depth and diameter of the planted foundation must be calculated. The CivilWeb Street Light Foundation Design spreadsheet does this by modelling the moment resistance of the ground based on three simple ground types as defined in HA HD94/17. It then returns a graph showing the minimum depth required to resist the moments. This process is very similar to the method used for sign foundations as detailed here.

Concrete pad foundations are sometimes used for larger street lights or where planted foundations would not be suitable. The CivilWeb Street Light Foundation Design spreadsheet calculates the required size and depth of foundation using a detailed design procedure in accordance with BS EN 1990, 1991 and 1997. In some cases this level of detail would be considered excessive, particularly if the calculations are being done by hand. However the spreadsheet makes this process very quick and simple as the inputs required are generally the same for all the design checks. The designer simply inputs the proposed foundation dimensions and the soil shear strength and unit weight and the spreadsheet instantly completes 11 separate design checks and returns graphs showing the dimensions required for the foundation to pass each design check. The spreadsheet also includes a unique feature returning suggested foundations sizes which meet all the requirements. This is done for the chosen foundation depth and for 3 other commonly used depths allowing the designer to quickly ascertain whether a more economical or more suitable design is possible. Again this process is similar to the one used for sign foundations detailed here.

To produce an economical design the designer can simply input a suitable depth which will generally be as deep as is practical for the installation methods anticipated. The spreadsheet will then return a suggested length and width dimensions for a square foundation which will meet all design check criteria in accordance with the Eurocode standards.

The CivilWeb Street Light Foundation Design spreadsheet completes the above detailed design procedure enabling even single street light foundation designs to be fully optimized for an economical design.

Spreadsheet Main Features;

• Simple and Complete Wind Loading Calculations - The spreadsheet can complete  detailed street light wind loading analysis in accordance with BS EN 1991-1-4 and BS EN 40. Alternatively where some design parameters are unknown, the spreadsheet can also estimate wind loadings in accordance with the simplified procedure in BS PD 6547.
• Embedded Street Light Foundation Design - The spreadsheet completes all the required calculations for an embedded street light foundation design in accordance with BS EN 12889-1 and minimum planting depths in accordance with HD94/17.
• Street Light Pad Foundation Design - Alternatively the spreadsheet also completes all the required calculations for a street light pad foundation in accordance with the Eurocode design standards. Unique design features include graphs showing the optimum foundation dimensions for each of 11 design checks and suggested foundation sizes which meet all the criteria. This allows the designer to complete a fully optimised design in seconds without any iterative steps.

Get the full license version now for only £20. This includes;

• CivilWeb Street Light Foundation Design Calculator Spreadsheet with all inputs available. Both detailed and simplified wind loading analysis included.
• Free comprehensive 27 page Ultimate User Guide.  This includes detailed information and typical values for all the required inputs and an explanation of the design standards and principles used in the spreadsheet.

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