The Place, is the latest commercial project of developer Sellar’s London Bridge Quarter scheme.
It sits in the shadow of its bigger sibling The Shard, but resolving the complex challenges in creating this building has yielded an extraordinary project, quite worthy of sharing the same space as its lauded neighbour. A JCT Major Project Construction Contract underpinned the solution.Several pioneering techniques were adopted by the project team in building The Shard. On The Place, with the same team, including contractor Mace and architect Renzo Piano, a complex series of issues would mean that their previous experience would be invaluable in this project.
The key issue for The Place has been space. A building fulfilling the requirements of principally corporate occupiers requires floorplates of around 20-30,000ft2. The first barrier to this is that the foundations are surrounded on all sides by London Underground infrastructure. On the South-East side, Jubilee line tunnels and a platform access escalator; the North and North-East includes the London Bridge Underground station and a Northern line escalator; and to the South and West of the site are contained the underground ventilation shafts.
To overcome the problem, a cantilevered structural design was created over the foundations which enabled the footprint to occupy 55% more space than previously available. For this to even be possible however, meant constructing the foundations within the 3m exclusion zone stipulated by London Underground. The system had to be designed in such a way that allowed existing transport activity to continue uninterrupted and avoid any movement of London Underground assets. A complex 3D analysis was carried out to measure potential movement and convince London Underground that works were safe to be carried out within the exclusion zone.
Complicating matters further was the discovery of Roman artefacts in the foundations. This posed a potentially significant risk to the project timeline, as an archaeology team now had to be put in place to carefully extract the artefacts. A result of this was the decision to reduce the depth of the foundations by one level, which was achieved by careful redesign of the location of the plant rooms.
Fortunately many of the building techniques pioneered by the project team on The Shard were brought across and employed on The Place to ensure it met its project deadlines. This included the top-down construction method, which enabled works above ground to progress whilst the foundations were being excavated. In addition, the twin cores were also jump-started, so the core could be built above ground before the core walls were cast underground. Plunge columns were used to support the core, enabling the basement to be excavated and the core walls to be built around them.
For The Shard, core work was stopped on the 21st floor due to the pressure on the plunge cores, but for The Place, which is 14-storeys, this process could be carried throughout to completion. This meant that archaeology,demolition, piling and core work took place simultaneously during phases of the project.
Another key issue was one of strength. With the floorplates occupying a larger area above the foundations, the support of the cantilevered design had to be constructed in a particular way to ensure the structural stability of the building. A corbel system was put in place, where raking columns are tied back to the cores to provide a supportive triangular structure. Further pressure was on the team to deliver as the structure below the raking columns is supported by them, and as the structure cantilevers over the nearby bus station, temporary works had to be located there and completed before the Olympics.
An unusual element of The Place is its asymmetry, due to the cores being under unequal load. This resulted in the building being pulled over to the East. In addition to reinforcement of the cores and thicker walls, the cores have also been built with a pre-set lean to the West. The design developed so that the cores will be pulled into a vertical position once the movement is complete.
A major aspect of completing the project in this way resulted from the use of BIM. BIM was used during several different stages of the project to provide solutions. Initially, it was used in the modelling phase to convince London Underground of the safety of building within the 3m exclusion zone, as areas of movement could be tested and risks could be analysed and assessed. BIM was also used in the design of the structure to account for the asymmetrical loads and their subsequent movement once complete.
A technique known as non-linear analysis (pioneered following the World Trade Centre attack in 2001 to measure the collapse of buildings) was employed, as it allows designers and engineers to design more resilient buildings and complex structures like The Place.
BIM was also used to solve unseen problems that occurred during the project. For instance, in the redesign of the foundations as a result of the archaeological discovery, the model was able to show how the plant rooms could be relocated, so the depth could be reduced by one level. With the discovery of a forgotten entrance to the old City and South London underground line in the way of the secant wall, BIM enabled a redesign to quickly re-route the course of the wall. Overall, the use of BIM has been a benefit to the efficiency of design and delivery, resulting in a reduction of 10% in building costs.
The Shard and The Place represent two aspects of JCT from a contractual view. On The Shard, stability, a recognised form, and well-established contract terms, along with flexibility over design and construction were required which was met by the Standard Building Contract. The complexity of The Place however has warranted a different approach and the use of the JCT Major Project contract has enabled even greater flexibility around design and problem solving and construction. It also more readily accounts for the expertise of the project team. Ultimately this has led to further innovation, some imaginative ways of solving problems, savings on building costs and an increase in overall efficiency.