Dolmen Flyover Interchange Improves Safety and Traffic Flow

DYWIDAG installed post-tensioning for the landmark Dolmen Flyover Bridge, in Emmen, Netherlands, to improve traffic flow and safety. The team navigated significant construction challenges that stemmed from strict regulation around closing roads on the interchange to complete a construction challenge initially deemed “impossible.”


For years, the busy Emmen-West interchange, where Rondweg (N391) and the N34 connect, near Erm, Netherlands had been experiencing traffic and safety hazards caused by vehicles and trucks entering and exiting at the same level. A new flyover needed to be built to improve safety and accessibility. Because of strict rules for opening/closing roads, the bridge would have to be built using building techniques considered nearly impossible. DYWIDAG engineers worked to design a solution, and then supplied and installed the post-tensioning system for the flyover.


  • Design post-tensioning system

  • Supply and install 14 cables, MA 68 19 over 93 meters


The installation was very challenging due to strict requirements around traffic and road closures. Typically, a regular bridge with multiple spans usually starts on one end and is built toward the other side to allow space to place the jacks. In the Dolmen case, the bridge was built in three segments beginning with the end sites (1 and 3), and the middle phase installed last. It was considered impossible due to lack of space to place the middle jack. (See below for details.)

The flyover was built in three segments, with the middle segment poured last. This means that this part needed to be tensioned by pushing the segments one and three against segment two. Ducts and anchors from parts one and three were installed to tension part two.

DYWIDAG engineers worked on this difficult design with contractor Van Spijker to develop a unique solution. A custom three-phase construction design was created, using 14 cable MA 6819 over 93 meters. This had never been done before.

Constructing the Dolmen Flyover in Three Phases:

  • Phase 1: Deck field 1 and 14 ducts installed; strands placed but only 7 ducts were filled and tensioned over the 31m.

  • Phase 2: Deck field 3 and 14 ducts installed; strands placed but only 7 ducts were filled and tensioned over the 31m. The 7 tendons (50% of the final force) were enough to carry the own weight and loads during construction. These tendons are over 62m.

  • Phase 3: Deck field 2 and 14 ducts installed and connected to the empty 7 ducts in fields 1 and 3. Strands were pushed in through fields 1, 2, and connected with couplers to 3. During this last tensioning phase, fields 1 and 3 squeezed with the middle deck, providing necessary tension. At the end of the process, the cables were 93m long with the installation of the couplers.


Provincie Drente