The Piilolanniemi bridge has been completed and inaugurated

The Piilolanniemi bridge at Metsä Group’s bioproduct mill has been completed well ahead of schedule and has already been opened to construction site traffic. During the construction phase of the bioproduct mill, the bridge will serve as the access point for heavy deliveries: building materials, prefabricated elements, equipment and special deliveries.

The final inspection of the bridge was carried out in cooperation with the Äänekoski building supervision authorities on Monday 14 March 2016. The bridge was built by Kreate Oy and designed by Sito Oy.

“This challenging bridge project was implemented over a short period of time and offered something new for all parties,” says Tommi Rissanen, Area Supervisor.

The bridge was built over the lower reaches of Äänejärvi, which runs into Lake Kuhnamo. It is a prestressed concrete continuous beam bridge with a total span of 80 metres. The bridge is accessed from Tehtaankatu on the side of the Piilolanniemi peninsula.

The Piilolanniemi Bridge is the newest addition to the network of bridges in Äänekoski. It was opened for heavy deliveries to the construction site immediately after its final inspection. Image: Metsä Group

Construction began in August 2015

The scaffolding for the bridge was built on a temporary bridge. Its deck was cast just before Christmas, and the bridge was prestressed at the beginning of 2016. Embedded heating pipes and a weather protection structure around the bridge ensured that the deck dried sufficiently rapidly at sub-zero temperatures.

In addition to the heating pipes, the special features of the Piilolanniemi Bridge include the fact that its deck structure has no crossbeams. This structure made it much easier to build the cable trays and the catwalk between the main beams, as well as the widest mass expansion joint in Finland, to facilitate the maintenance and cleaning of the bridge. Paving in February at the northern latitude of Äänekoski was no ordinary paving experience...

The bridge has a horizontal clearance of ten metres.

A low railing was installed on the downstream side of the bridge to accommodate abnormal loads. It will be replaced with a high railing after all of the abnormal loads for the construction site have been delivered.

During the construction phase, passenger traffic will run on the upstream side of the bridge, as this side already has a high railing. The concrete platforms under the railing posts will be cast after the low railing on the downstream side has been replaced with a high railing.

“The access and transportation needs during the construction and operation phases, as well as future care and maintenance needs, were taken into account as extensively as possible in the design and construction of the bridge,” says Rissanen.

A weather protection structure, as well as heating pipes embedded in the deck of the bridge, enabled work to be carried out at indoor temperatures even in January when the outdoor temperatures were far below zero. Image: Metsä Group

The longest and thickest piles of the construction site

The most demanding challenge emerged during the early stages of the project: the pile driving did not go according to plan due to a lack of space and because the bedrock was located deeper than expected. Using abutments, the reinforced concrete piles were replaced with steel ones, and the longest and thickest piles of the construction site were drilled using middle supports. Each of these 800-millimetre bored piles is nearly 35 metres long.

The effects of the construction of the bridge on natural waterways and landscapes were taken into account during the environmental impact assessment (EIA) phase. The logistical solutions for the bridge were designed in cooperation with the City of Äänekoski and the local Centre for Economic Development, Transport and the Environment (ELY Centre). A permit was obtained for the bridge construction project in accordance with the Water Act.

The bioproduct mill will be inaugurated during the third quarter of 2017. After that, the bridge will serve as the main access point for timber deliveries. Around 240 lorries per day will arrive over the bridge throughout the year.

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