Vertical Vessel Foundation Design Spreadsheet

Octagonal Vertical Vessel Foundations

Vertical vessel foundations are often octagonal in shape as this provides the most cost effective solution to a foundation which can be loaded in any direction. While typical columns are only loaded in two directions, a vertical vessel may have a large wind force component which can act in any direction.

Theoretically a circular foundation would be most appropriate but circular concrete shapes introduce difficulties with construction and reinforcement detailing. The octagonal foundation is a compromise which uses much less concrete than an equivalent square foundation but is much easier to build than a circular foundation.

The CivilWeb Vertical Vessel Foundation Design Spreadsheet can be used to design any octagonal foundation. Octagonal foundations are often used where the foundation can be loaded in any direction. They are also often used for pipelines or other large projects where hundreds or thousands of identical foundations are required. In these cases relatively small savings on concrete for each foundation can add up to produce significant savings when repeated many times.

Octagonal vertical vessel foundations work by spreading the load from the load point over a larger area. This reduces the bearing pressures on the soil low enough so the soil can resist them. The calculation of the bearing pressures beneath an octagonal foundation is more complex than for a typical square foundation. Completing these calculations by hand is a time consuming process. The CivilWeb Vertical Vessel Foundation Design Spreadsheet spreadsheet is able to complete these calculations instantly, allowing the design to check the validity of the design and to optimise the size of the foundation in minutes.

Vertical Vessel Foundation Design Spreadsheet - Inputs

Firstly the designer must input the loading conditions for the octagonal vertical vessel foundation. In most cases these loadings are set by the superstructure design and cannot be altered by the foundation designer. The spreadsheet can be used to model any combination of axial, horizontal and moment forces acting on the foundation. The designer can also include a universally distributed load on the foundation.

Next a trial foundation dimension must be input. This can be taken from experience of similar foundations or simply guessed. A useful dynamic drawing of the octagonal vertical vessel foundation is produced by the spreadsheet so the designer can see exactly what is being analysed.

Next the designer must input the soil properties. The CivilWeb Vertical Vessel Foundation Design Spreadsheet works using a simple maximum allowable bearing capacity for the soil. This is a simplification of soil behavior but in most cases is adequate for simple foundations. The bearing capacity of the soil can be taken from experience for preliminary design but must be verified from site testing before the design is finalised. In long pipelines or similar large projects the bearing capacity of the soil will need to be checked at regular intervals. A simple spreadsheet such as the CivilWeb Soil Bearing Capacity Calculation Suite can be used to finalise the maximum allowable bearing capacity after onsite testing.

In most cases the octagonal vertical vessel foundation will not settle more than 25mm if the maximum allowable bearing capacity of the soil is not exceeded. However in some clay soils consolidation settlement caused by the increase in pore water pressure can continue for many years after the foundation is built. In these cases and where the structure is sensitive to settlement it may be prudent to undertake a separate settlement analysis as well as the bearing capacity analysis. A simple spreadsheet such as the CivilWeb Foundation Settlement Calculator Spreadsheet can be used for this analysis.

After the designer has input the loading, geometrical and soil design parameters, the CivilWeb Vertical Vessel Foundation Design Spreadsheet will complete the analysis of the foundation. The spreadsheet can complete this analysis in accordance with either BS EN 1997 or BS 8004. The spreadsheet will present the results of the analysis to the designer instantly, allowing the design to be tweaked and optimised by the designer. This eliminates the need for time consuming iterative design procedures as a fully optimised design can be completed using the CivilWeb Vertical Vessel Foundation Design Spreadsheet in minutes.

After the designer has finalised the geometrical design, the CivilWeb Vertical Vessel Foundation Design Spreadsheet now completes the calculations required for the reinforcement design. The spreadsheet can complete these calculations in accordance with either BS EN 1992 or BS 8110. The spreadsheet calculates the maximum bending moments and shear forces and uses these to determine the reinforcement required for the foundation. The spreadsheet also includes unique reinforcement suggestion tools which allow the designer to see at a glance exactly which combination of reinforcement and spacing is most appropriate for the foundation.

The CivilWeb Vertical Vessel Foundation Design Spreadsheet then presents the designer with a summary and dynamic drawing of the octagonal vertical vessel foundation design highlighting any areas where the design is not valid.

CivilWeb Vertical Vessel Foundation Design Spreadsheet

The CivilWeb Vertical Vessel Foundation Design Spreadsheet can be used to complete a fully optimised an fully compliant octagonal vertical vessel foundation design in minutes. This will save the designer hours of works on every single foundation design. The spreadsheet also includes unique analysis tools which make the design process even simpler.

The CivilWeb Vertical Vessel Foundation Design Spreadsheet can be purchased here for only £20.