Construction of the Wellcome Trust Building presented a real challenge. The site was occupied by a lecture theatre and an oxygen and chemical plant, and surrounded by research and hospital buildings including the cardiac wing of Great Ormond Street Hospital. A high water table, variable ground conditions, demanding sound restrictions and very constricted site access compounded these difficulties. Furthermore, the floor levels of the new building had to match those of the existing Institute of Child Health building. Steel construction would have required suspended ceilings and greater floor depths, making it difficult to match the levels of the old and new floors. Concrete, which could be pumped from the street, was the obvious choice. It also provided passive cooling, more effective damping of structure-borne sound in the auditoriums and allowed the formation of complex shapes on the lower floors.
The upper building has ribbed, exposed in-situ-concrete floors either side of a tapering central spine. The grp mould sizes and setting out co-ordinate with the grid to allow subdivision into cellular offices, zones for perimeter lighting and for the set-back in plan at upper level. The layout provided for all this with just two mould shapes, 3m x 1.5m and 1.5m x 1.5m, used in combination to fit the plan and enliven the ceiling. Central columns have a tear-drop shape and, to keep them as small as possible, perimeter columns were cast using permanent steel tube formers that reduce in size with height.
One of the main elevations to the upper block spans 15m over the auditorium. This incorporates a 0.8m-wide sill-height upstand beam at the lowest level and clear glazing above. Heavily reinforced, the beam was pre-cambered and remained propped until the upper frame was complete. Load cells in the props monitored the increase in load as the frame above was constructed.
The auditorium and lower levels are of more traditional reinforced-concrete construction. The exposed coffered soffit is used again to striking effect in the circulation area. Complex geometry and acoustic isolation requirements led to some unusual details. The isolation joint follows a curved path beside and over the seminar rooms. The design also features transfer beams, one of which balances on a single 750mm -diameter column, double walls and slabs which cantilever over other slabs.
The monopitch roof slab, with its tapering plan and curved end elevation incorporating a fair-faced ring beam/ cornice, was a challenge for the formwork carpenters. To save time, the contractor cast the lower-ground- floor slab and vertical structure up to first-floor level so the construction of the upper block could proceed in parallel with the more complex auditorium floor slab and roof.
OWNER Halliburton Holdings BV
ARCHITECT Blair Associates
CONSULTING ENGINEER AND MAIN CONTRACTOR Brown and Root
PRECAST CLADDING The Marble Mosaic Co
EXPOSED IN-SITU CONCRETE FRAME P C Harrington Contractors
READY-MIXED CONCRETE rmc South Coast
INTERNAL COLUMNS Malling Precast