BIM applied to Hammersmith Flyover project. Ramboll
The competition’s panel of industry expert judges selected winners from 40 of the world’s most challenging civil infrastructure projects. Submissions covered a wide range of projects: airports; ports; bridges and tunnels; rail and transit; roads and highways; land, urban and campus; water resources; and utilities.
The judges evaluated entries based on complexity, innovative use of technology, sustainability and the execution of a BIM process to anticipate, assess and act more confidently from project start to finish and continue to add value to operations and maintenance. The winners will be honoured at the upcoming Autodesk University 2015 conference this December in Las Vegas.
Second prize for the Hammersmith Flyover project is shared by Costain, Ramboll Parsons Brinckerhoff Joint Venture for the model-based design applied to post tensioning strengthening and bearing replacement.
The Hammersmith Flyover carries the four-lane A4 arterial road over the Hammersmith gyratory and links the west to central London. Constructed more than 50 years ago, the 622-meter-long pre-cast, post-tensioned bridge, supported by 15 central piers, was in need of significant strengthening and repair.
With little space for the installation of a new post-tensioning system, and the requirement to keep the bridge open to traffic during construction, the design team sought a way to accurately account for the details of the existing structure, and to precisely design a solution. Starting from an initial as-built model created from record drawings, the team explored a number of conceptual post-tensioning options.
While the as-built model and concept designs were being progressed, the team undertook internal and external laser scan surveys. The greater accuracy of both the scan data and subsequent changes to the as built model helped to inform the designed solution and construction tolerance required for the system. The laser scan also allowed the team to identify and model existing elements that were not included on the record drawings giving greater confidence of clash avoidance.
With concept design proven, the team moved to preliminary design where Costain was appointed as Principal Contractor. Continuing to use the 3d model the design was refined to incorporate Costain’s system preferences and construction methodology. During detailed design Costain appointed a specialist post tensioning sub-contractor, Freyssinet, which brought about further design refinement. Opting for external precast and internal in-situ anchors rendered in Ultra High Performance Fibre Reinforced Concrete which were to be bolted together through the existing structure, the purpose of the model changed from developing the design to proving fit of all designed elements.
A highly collaborative cyclic process was established between all stakeholders throughout the project lifecycle, which involved modelling the proposed strengthening anchors and post tensioning cables, checking the design for fit and reporting, discussing and resolving issues, and repeating the process until the design worked.
By continuously checking for interferences throughout the design process, the team was able to address clashes between cable runs and against existing concrete to find a best-fit solution before construction.
Phase 2 strengthening of the Hammersmith Flyover (HFO2), was a phenomenally complex £100m programme including innovative engineering solutions to install a full new prestress without removing the original. With 70,000 users every day on a key strategic route into London, the structure, which had been deteriorating due to significant corrosion, presented many technical, logistical, programme and political challenges.