London Bridge Station - canopies

Entered by MBSI Detailing Ltd

A transformation of London Bridge Station

London Bridge Station, built in the 1830's is one of the world's oldest station. The station is being updated and transformed creating new platforms for more trains, building a new concourse and creating a bigger and better station for passengers. The concourse itself will be bigger than the pitch at Wembley Stadium and as well as providing new retail and station facilities will unify the station for the first time with access to all platforms from one place. By reconfiguring the track there will be nine "through" platforms and six terminating platforms. This model highlights the complexity of the canopies to those platforms.

Design principles of the roofscape

The canopies are designed to provide full platform coverage. Meanwhile, as to give an overall sense of unified roofscape, the canopies gently extend laterally above the platform edge, when above the concourse zone. Therefore the canopies seem to reach for one another from one platform to another.

Natural light into concourse

The canopies gently raise over the station concourse below allowing glazing on both the north and south elevations. However, as to limit direct southern light, the southern apex is kept at a lower height in comparison to the northern apex, controlling both glazing ratios. The north sides of the 'eyebrows' are glazed, to a maximum height of 4.5m above the platform canopy below. This allows north-light to be directed down into the canopy space. The soffit of the canopy will be a metallic, reflective finish. In addition to the indirect light, smaller openings have been introduced on the southern side of the canopy 'eyebrow'. This design allows shafts of direct sunlight into the space below in a managed way.

Louvres

Louvres have been integrated into the design as a visual link between the canopies to create the appearance of a continuous roofscape, in alignment with the planning constraints set by Southwark council. The geometry of the canopies changes as it moves along the platforms due to the larger structural members in the eyebrow area and the increased span.

'Y' Shape column design

The setting out of the columns is designed to standardise elements where possible. The top prefabricated cross beam and the steel arm are intended to be standard components, with the supporting steel column varying in length to suit the change in level of the canopy as it rises across the central area of the platforms, as the taper angle is fixed. It is proposed that electrical, mechanical, drainage and railway system (signaling cables) services routes will be located within the canopy columns and beams. The steel sections have been designed with voids for service routes integrated within. Services will be accessible via a removable cover panel which fits within the flanges of the steel.

Shard interface design

At the end of the terminating platforms the canopies integrate with an existing steel and glass roof, 10 metres above platform level, constructed as part of the Shard development. The canopies sweep up to 6m to meet the Shard canopy. Asymmetric Y shaped columns are used to support the upward sweep of the roof. These columns are founded on concrete foundations, below the concourse finishes, which span onto the arch piers below.

The design of the columns to this area use a similar architectural language to that of the 'Y' shape columns for the rest of the station areas. Rather than being a set of parallel columns, as for the through and terminus platforms, these structural elements have been designed as a single column to reduce the impact on pedestrian flow in the concourse area.

Effective creation of object database

The London Bridge canopies contract consists of a series of plated columns, spine beams & Y arms. These support a shop floor built up cassettes made from varying shaped rafters joined together with cold rolled Z section purlins to form the roof and C section purlins to form the soffit, these together form the roof canopies. One of the challenges we have had to overcome is to take the Architect's roof geometry and describe it as a sequence of cross sections with parametric properties. We then produced routines to calculate the positioning of standard components in a 3D model (purlins, rafters, gutters, etc), effectively creating a database of objects. From this an IFC file is created to import into the Tekla model and then converted to native Tekla objects. When detailing the connections because of the complex shape of the roof each purlin connection to the support rafter is slightly different so a series of standard custom components had to be produced. Due to programme constraints the opportunity for offsite work and modularisation will be maximised. This includes the buildup of cassettes on the shop floor ready to be delivered to site as required.