Working capacity

Conversion of disused water tower into offices, Huntingdon, Hertfordshire

The octagonal shape of this water tank structure, constructed in the early part of the last century as a reinforced concrete tank and pump chamber housing, supported by eight reinforced concrete columns is inherently strong. The capacity of the water tank is 576m³ and together with the self-weight of the superstructure equates to approximately 650 tonnes.

The proposed office development consists of a asymmetric steel frame supported by the existing water tank and two additional columns positioned such that the centroid of the new structure in coincidental with the water tank foundations and new column foundations. This ensures the load onto the existing structure remains symmetric, allowing the capacity of the existing foundations to be fully utilised.

The proposed structure consists of two storey Vierendeel steel trusses, between levels four and six radiating for the existing water tank columns, with two principal trusses supported by two new columns. The base of the Vierendeel trusses is designed to coincide with the base of the existing water tank allowing horizontal compression reactions from the cantilever vireendal trusses to be negated using the base of the water tank.

The weight of the proposed structure is considerably less than the weight of the water previously stored, although with the asymmetric plan of the proposed structure a significant proportion of the weight of the proposed structure will be supported by the new columns. Able to support the additional lateral loads from the proposed structure, the existing foundations are not overstressed.

The capacity of the piled foundations for the two new columns are designed to reciprocate the percentage of the capacity of the exiting foundations loads when loaded with the proposed structure, ensuring that both the short and long term settlement of the new and existing foundations will be similar.

The floor and roof of the proposed structure consists of in-situ reinforced concrete on profiled steel decking, bearing onto to composite secondary beams and supported by the primary steel Vierendeel l frames. The structure of level three is similar to flooring above and is supported by composite secondary and primary beams suspended from the Vierendeel trusses at level four with vertical tension columns.

The in-situ concrete flooring will provide lateral stability to the proposed structure at each level.

Service: Architects

Location: Huntingdon, UK

Client: Landro Ltd.

Cost: Undisclosed

Areas: XX m2

Dates: 2005

To Live In   To Learn In   To Work In   To Play In