FEATURES IN THE DESIGN AND CONSTRUCTION OF THE SHELL CENTRE, LONDON.

Abstract

The Paper refers briefly the London County Council's scheme for development of the South Bank area, and describes the main features of the Shell Centre which is divided into an upstream and a downstream section. A feature of the former is a tower block 351 ft high. An account is given of the ground conditions over the site and of considerations concerning the effects of extraordinary high tides. Retaining walls of prestressed concrete were designed to act as simple cantilevers. Prestressing of the walls is described. The basement of the upstream section was constructed over the tunnels of the Bakerloo Railway and its floor level was only about 7 ft above the crown of one tunnel. Special measura and precautions were taken to avoid damage to the tunnels. Calculations were made of the probable heave of the tunnels during basement excavation and careful observations carried out of the actual heave. The distortions of the tunnels were measured. The buildings are extensive, with wide differences in the foundation loading under various sections. Differential settlements had to be considered carefully and measures taken to minimize their effects. The tower block and certain other parts of the upstream section were founded upon cylinders which were generally formed by machine auger. Water was excluded from the basements by the retaining walls which formed a cut-off in the London clay. Reliance was placed upon the watertightness of the concrete in the retaining walls. These were divided into short lengths, with water bars in the joints. The upstream and the downstream sections are connected by a subway under the brick arch of the Waterloo-charing Cross railway viaduct. The construction of this subway immediately adjacetnot shallow viaduct foundations carrying heavy locomotives called for special measures. Cooling water for the air conditioning system of the building is drawn from the River Thames through a tunnel in the London clay. This was driven by hand without a shield. Compressed air was applied to the section of tunnel under the river. The framework of the tower block is steel. Up to second floor level this takes the form of welded rigid frames. Above second floor level lateral strength is provided by moment connexions with high-strength bolts, in combination with bracings incorporated in fixed wall positions. Measures taken by the contractor to achieve a high speed of construction are described briefly.