A 640-meter bridge replaces the Vekaransalmi ferry
Graniittirakennus Kallio has won a bidding competition arranged by the Northern Savo ELY Centre to span the Vekaransalmi sound at Sulkava. In less than two years of construction, a 640 meters long box-girder bridge joined by 1,6 kilometres of new roadway will be built to span the watercourse between the bay of Ruokolahti and the Vekaransalmi sound in the county of Sulkava in eastern Finland.
“We will start work during January. During the first year, we will focus on erecting the support structures and assembling the steel beams of the bridge. We have scheduled the casting of the deck slab for April 2019”, says site manager Antti Rämä.
Rämä estimates that one of the biggest technical challenges of the entire project is the drill piling of the foundations for the four intermediate supports. The drill piles are the largest possible: their diameter is 1220 millimetres. There are ten supports in total; the remaining six supports rest on land or rock, and thus require no piling.
The fleet of cranes is also massive. At the site, a heavy crane is needed especially for lifting the steel beams. The longest span of the nine-gap bridge is 120 meters. The dimensions of the steel beams supporting the bridge deck vary according to the load and the span. The flange height of the beam thus varies from 5.2 meters at the highest, to 1.65 meters at the lowest. The steel beams are assembled into prefab elements on a launching bridge and moved to their support bearings by cranes.
“The concrete deck will be cast in-situ as a continuous three-day pour. The deck slab varies in thickness from 23 to 36 centimetres. The traffic loads will be taken by the steel girders. The thickness of the deck is thus quite moderate in relation to the size of the bridge”, Rämä explains.
The ferry will be out of work
The turnkey bridge contract is yet another example of demanding bridge construction lately performed by Graniittirakennus Kallio. Concurrently, the company is operating the Vårdö bridge construction site in Åland.
“We have sufficient resources for our site, which will employ some 50 workers as a maximum, and about 30 as an average”, says Antti Rämä.
Of the total project cost of EUR 18.6 million, the actual bridge works at Sulkava account for almost 90 percent. The remainder is earmarked for a total of 1.9 kms of roadworks, to create the access ramps to the new bridge from both sides of the Vekaransalmi sound.
Until the end of 2019, vehicle traffic on the regional route 438 leading to Ruokolahti between Virmutjoki and Sulkava will still depend on ferry service. The local ferry has served faithfully for over 20 years. Before Sulkava, it was stationed in the Turku archipelago. But a bridge built there some five years ago caused the relatively new ferry to be transferred to Sulkava, as a replacement for the aging former ferry there. Now, once again, a new bridge will put an old ferry out of work.
“The timetable in the project is tight, but fully realistic. We have allowed for postponing assembly work on days when the wind exceeds 10 meters per second (20 knots)”, says Antti Rämä.
Jetro Matilainen, project manager of the client, the Finnish Transport Agency, considers the project important because the bridge represents a significant improvement in traffic flow compared to the current ferry service. Additionally, the operating costs of the ferry will be eliminated upon completion of the bridge. The resulting savings of nearly one million euro per annum will significantly increase the economic viability of the project.
“We received two good bids for the bridge contract. Of these, GRK submitted the best one. In choosing, we paid attention not only to the price, but also to the competence of project management and site personnel, as well as quality management, safety and data modelling”, he says.