Property Developers, European Land appointed Mace as main contractor for this £100m project with PJ Carey (Contractors) Limited as concrete frame contractor. This project brought a number of construction challenges; the basement abuts the existing developments of 4 and 5 Merchant Square and one of the towers is being built within only 500mm off the existing 4 Merchant Square. The project is also being built directly over the Bakerloo Underground Line with the south side of the basement only 500mm from the 100 year old Grand Union canal.
The combined floor plan of the towers is 30,000m2 of post tensioned slabs constructed by P J Carey (Contractors) Limited. The lift and stair core in the smaller East tower is being constructed using a Doka’s GCS guided climbing system, along with Doka’s Framax panel formwork lined with Wisaform to form the specified, quality concrete finish. Doka’s GCS is a crane lifted formwork platform, with each 3.08m high construction lifted into the next position by the GCS guide rails and climbing shoes. This climbing system was chosen for the East Core due to its close proximity to the existing building allowing P J Carey(Contractors) Limited to lift a complete individual face of formwork in a single operation, shortening construction cycle times.
The core in the West tower is larger and more complex with an irregular shape and sub cores (cores within the main core). This core is constructed using Doka’s SKE50 hydraulically operated self-climbing formwork system with Framax formwork panels, again lined with Wisaform. Doka’s SKE50 was chosen as it is entirely independent of site cranage, freeing up crane hook time for construction of the East Core and other lifting operations. The planned cycle time for each 3.08m high lift was 5 days, but P J Carey (Contractor) Limited achieved on average 3 days and at best 2 days when sufficient concrete maturity was achieved.
The climbing formwork design for each core needed to consider additional loadings imposed from the use of a spider pump and concrete placing boom, which was to be located on one of the internal working platforms. Additionally, the main external working platform on both cores included Doka’s 2m high trapezoidal protection screen, providing a fully enclosed, safe working platform with protection from inclement weather.
Doka UK supported this project with a comprehensive service package, supplying their formwork, providing design, engineering support, planning of formwork, preassembly of working platforms, rental of equipment, formwork logistics with planned site delivery and an onsite demonstrator in the training and licensing of P J Carey (Contractors) Limited personnel in the safe operations of SKE50 and GCS climbing systems.