Complex creativity: a new version of structures analysis software has been used for numerous bridges in Finland.

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Use of 3D building information technology can dramatically improve current processes, according to Tekla UK, which has recently released version 14.1 of its Tekla Structures software. The techniques can minimising replication of data input and provide accurate information to help manage projects more effectively, says the company.

Consultant WSP Finland has used Tekla Structures on bridge designs. "Modelling is not 'hype' any more but actually translates into better quality," says WSP Finland's IT development manager Antti Karjalainen. The geometry of a bridge is nearly always more complex than that of other structures, he says, and accurate and efficient 3D modelling is essential.

Tekla says that the move from a 2D format to intelligent 3D models allows the resulting information to be presented and coordinated on drawings and reports by all the project team members. This ensures that information is correctly displayed on all plans, elevations and sectional drawings and model reports, representing the as-built state of the finished bridge.

The recently-released version 14.1 of Tekla Structures builds on previous versions by integrating construction management tools into the system. It includes time as a fourth dimension to track how the project is proceeding. Time-sensitive data can be incorporated into the model to control and update the schedule at various stages and levels of detail throughout construction.

Engineers from WSP Finland have used the 3D modelling capabilities on bridges such the asymmetric cable-stayed Crusell Bridge in Helsinki, Finland, which is currently under construction. Tekla Structures was used to design its steel and concrete parts as well as the supporting walls on the embankment. The bridge has spans of 92m and 51.5m, with a passage for small boats located at the main span. The cable system is an asymmetric harp, where the cable angle of the back span is steeper than the angle of the front cables. The towers of the bridge are inclined 11[degrees]. "The project is challenging, including a cast-in-place concrete deck, but it will pay to model," says Karjalainen.

Another WSP Finland project is the Varikko Depot Bridge in Kajaani, in the north of the country. The existing bridge was demolished before a new reinforced concrete bridge could be put into place. The new bridge has a curved horizontal geometry with a constant cross-section and five spans of between 8.3m and 15.3m. The entire structure was modelled using Tekla Structures, including remaining parts of the existing structure to which the new structure is joined. Laser scanning was used to locate the model in the ground coordinate system and in the correct position in relation to adjoining structures.

According to WSP Finland, modelling the base structures, the ground support and intermediate supports using Tekla's software was much quicker and easier for both the concrete structures themselves and the reinforcement. "During the different phases of construction, the bridge geometry was measured several times, and the results were compared with the Tekla model," says Karjalainen.

"At the same time we used the model to measure the achieved quality in the geometry. We saw that modelling in combination with the latest methods of measuring is a functional and efficient way of working."Madekoski Railway Bridge in Oulu was also designed by WSP Finland and modelled using Tekla Structures. The deck of the 7.2m-wide continuous three-span concrete slab structure was built alongside the railway and then moved into position using hydraulic jacks. It was mounted on steel pipe piles that had already been driven into the ground through the railway embankment. "To ensure successful fitting, we usually compare the as-built dimensions with the accurate Tekla model," explains Karjalainen.

WSP Finland managing director Matti Mannonen sees a clear trend: "There is no doubt that we will move on to using 3D modelling for all bridge design within the next couple of years."

Tekla

www.tekla.com