National Portrait Gallery. Client. Norwest Holst. Consulting Engineer. Ove Arup and Partners.

Project value. £450.000

Royden Engineering counts the National Portrait Gallery as one of its success stories.

The engineering design was driven by the need to achieve the space envisaged by the architect while taking account of the extremely tight constraints imposed by the proximity of the adjacent existing National Portrait Gallery and the National Gallery, both grade 1 listed structure. Due to the sensitivity of movement of the structures there was a need to provide an independent building to take the column loading away from the existing facades. The decision was made by Ove Arup and partners to use a lightweight composite steel structure founded on tripod bored piles.

The distinctive form of the new buildings upper levels was achieved by supporting the majority of the weight of the floors from a storey high truss spanning the length of the structure between two supporting columns. The truss was made up of eight welded sections which were built up in position. An extensive temporary works scheme was developed by Royden Engineering to give stability in the temporary condition before the permanent support members were put in place.

Careful thought had to be given to the construction sequence and close communication was required with Ove Arup and partners to ensure that clear load paths were maintained and movement minimised during the various stages of construction as well as in the final condition to prevent additional loading on the existing foundations.

The finished product was that of an award winning structure that was built on time, within budget and constructed under extremely tight tolerance and spacial constraints.