Chenab Bridge soars through construction process thanks to BrIM

Steel bridge 320 metres above surface of river and insert showing the corresponding 3D model with point clouds

Chenab Bridge, located in northern India, is being constructed as part of the new Baramulla – Srinagar – Udhamptur railway and is one of the highest (by deck height) and longest-spanning railway bridges of its type in the world. Due to the enormous scale and complexity of this project, Bridge Information Modelling (BrIM) was a prerequisite from the client and consequently, Trimble’s Tekla Structures software has been used from the beginning.

By incorporating Tekla software, it has enabled efficient collaboration between all parties, as well as allowing the steel structures to be modelled accurately and drawings to be easily printed directly from the model for the fabrication team.

Constructed 320 metres above the surface of the river Chenab and stretching 1,315 metres long, work on the new steel archway bridge began in 2004 with completion expected in 2019. The main arch of the Chenab Bridge spans an impressive 467 metres, making it one of the longest arches in the world, and has a 13.5 metres wide deck, which has been designed for two rail tracks.

Steel arch of bridge modelled on point cloud bedrock

Erected on Himalayan bedrock with foundations approximately 40 metres high and 50 metres wide, the arch and piers of the bridge are masses of steel trusses, while the foundations and the approach viaduct piers are made of concrete. The arch is erected with a cableway crane, after which the deck is then launched into placed and joints assembled with a total of 600,000 bolts.

To improve the structure’s horizontal stability, the two outer arch elements taper from 10.5 metre in distance of axes at the arch crown to about 30 metres at the base. All piers are tapered accordingly to the inclination of the column legs. This enables a balanced combination of lateral stiffness and flexibility, both requirements of railway and seismic needs.

3D model of bridge on either side of canyon with gap in middle

As the new railway bridge is being built under extremely demanding conditions and will continue to face an array of challenges, at the beginning of project the client, Konkan Railways Corporation, stated that BrIM was to be used to create an innovative design and ensure effective co-operation between all parties involved. As such, WSP Finland, the designing consultant on the project, chose to use Tekla Structures software, as it contains precise, reliable and accurate information needed for successful BrIM and construction execution; it also creates more accurate ways of working and streamlines collaboration between all parties.

In fact, on this project, using Tekla Structures allowed WSP Finland to organise the plate material for better logistics in the difficult terrain; it made it easier to receive the approval from local authorities too, thanks to the visualised 3D models, which were more practical to present in meetings than 2D drawings. 3D visualisation is a comprehensive tool required for bridge design, as it facilities the processes and makes them more successful. The designers can use the 3D models, which include all of the data that is relevant to the project, in all phases, from conceptual design to the preparation of final workshop drawings.

Although, being able to see the project in 3D is often the first benefit for contractors and clients, it is not the most important factor when undertaking a BrIM project, the data is. With Tekla Structures, users can create a constructible, parametric model, which means each and every object holds its own data. This constructible data can then be used for fabrication, erection, construction on-site and asset management during the maintenance of the bridge.

Matti-Esko Jarvenpaa, Development Manager Bridges & Structures from WSP Finland, said: We use Tekla Structures because it is a parametric modelling tool and the model includes all of the data that is relevant to the project, from conceptual design to detailing and fabrication. The accurate data can be used in construction on-site, and even for asset management later in the maintenance phase.

Full Tekla model spanning point cloud canyon

Indeed, a BrIM can be used by various project participants, from contractors to subcontractors, to enter and output measurements and dimensions. In the case of the Chenab Bridge, the Tekla Structures model has produced tens of thousands of drawings, with members of the various parties using it daily to run files for production, management and flame cutting. The contractor on the project, Chenab Bridge Project Undertaking (CBPU) has many BrIM users working on the project, and the site management uses Tekla BIMsight for reviewing the model on site.

Tekla BIMsight is a professional tool for construction project collaboration. The entire construction workflow can combine their models, check for conflicts and share information using the same easy to use BrIM environment. It also enables project participants to identify and solve issues already in the design phase before construction.

Underside of bridge model showing maintenance walkway

At the earlier stages of the project, subcontractor Leonhardt, Andra and Partner, as well as third-party inspector Flint & Neil, also used the model; with Flint & Neil using it to partially conduct the inspections.

By using Tekla Structures, WSP Finland also increased efficiency and optimisation, utilising its extensive range of connections and automated clash checking, which exposes conflicts at an early stage. The designing consultant could also execute reinforced concrete, braces, elements and block constructions, and due to its dimensional accuracy and steady coordinates, the end result was reliable and as expected. The 3D model also generated reports for material quantity take-off, assembly dimensions and centre of gravity for lifting and transportation.

Concrete bridge piers under construction

Unsurprisingly, the design practices in bridge projects have gradually moved towards model-based design, as visualising information makes it easy for all parties to understand the process, and in the planning period the components can be associated with scheduling information. Taking this approach on the Chenab Bridge project has certainly proved that BrIM can make a large-scale project seem less complex to design, plan and construct as one may think.

In fact, using BrIM and Tekla Structures software on the Chenab Bridge has made assessing information at every stage of the design project possible, while improving efficiency and productivity, and minimising the need for rework.

Side profile of Chenab Bridge upon completion, bridge towers across huge canyon