Canary Wharf Buildings

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Overview

Location: Canary Wharf, London

Client: Canary Wharf Contractors Ltd / P C Harrington Group

Scope: Design & Install Post-Tensioning

The columns in DS3's basement substructure are typically on a 9 by 10.5m grid and the standard 300mm thick RC flat slab can cope. However, in one area, the grid becomes irregular creating spans of 13.5 and 18m. To get the shallowest structural depth, Post-Tensioned beams have been introduced to cross these large spans.

A 3000 by 900mm deep beam is needed for the 18m span, with 3250 by 650mm deep beams being sufficient elsewhere. The design has to accommodate 1500mm square by 200mm deep recesses in the top of the beams for the baseplates of the superstructure stanchions. This prevents all the tendons from reaching the profile high point, leading to a design that is less efficient than usual. Never-the-less the post-tensioned solution solves the headroom problem in the basement. Live load is 5.0 kN/m2 and additional dead load is 4.8 kN/m2 . The bonded slab post tensioning system has been selected as this uses the hand-held monostrand jack, thus avoiding the need for craneage.