Project-specific solution for the longest cantilever bridge in Northern Macedonia
4 March 2019
Kičevo‑Podvis Motorway Bridge, Northern Macedonia
Upon completion, a new, almost 65 km long motorway will connect the cities of Kičevo and Ohrid in the south west of the North Macedonian Republic. On the first section between Kičevo and Podvis, it was necessary to build a 381 m long viaduct. For this, PERI engineers developed a project-specific solution on the basis of the VARIOKIT balanced cantilever equipment. As a result, this allowed the construction team to maintain the very tight building schedule – in spite of the challenging terrain.
On the first section through the mountainous region of western Northern Macedonia, the new motorway crosses a total of 14 viaducts. On a length of around 10 km, 4,000,000 m³ of earth had to be excavated with altogether 150,000 t of concrete and 15,000 t of reinforcement subsequently being processed. However, the biggest challenge for this section of the motorway was the viaduct at Kilometre 9. PERI offered the most cost-effective formwork solution for the bridge piers and superstructure.
Cost-effective through maximum flexibility
A total of four VBC Balanced Cantilever Carriages from the VARIOKIT Engineering Construction Kit supported the construction of the radial bridge superstructure with a span of 165 m. With the balanced cantilever method, the superstructure is symmetrically realised on both sides in the form of a balance beam - starting from the rigidly connected pier. With the help of the VBC Balanced Cantilever Carriages, the site team succeeded in constructing the 12.55 m and 11.55 m wide carriageways, which had to be carried out separately, within the tight construction schedule. The height of the superstructure varied between 9.00 m at the pier and up to 4.00 m in the centre of the bridge. The concreting cycles also varied in length from 3.30 m to 5.00 m. In addition to the constantly changing superstructure cross-sections, the PERI solution also took into consideration the constant longitudinal inclination of 2.8 % as well as variable inclinations of 1.5 % to 6.0 %.
Successful implementation in spite of the tight construction schedule
In particular, the hydraulic solutions for adjusting and aligning as well as the independent moving procedure of the formwork carriages shortened the execution times. Due to the high degree of flexibility of the balanced cantilevered carriage, the system could be quickly adapted in order to match the different cross-sections whereby individual offset cycles were accelerated and work processes optimised. As a result, the construction team realised a regular 7-day cycle.
Project-specific system combination and comprehensive PERI service
For constructing the bridge piers, TRIO Panel Formwork and VARIO GT 24 Girder Wall Formwork on horizontally positioned SB Brace Frames were used as well as a combination consisting of the SCS Climbing System and CB 240 Platforms. PERI UP Stair Towers provided access to the various working areas. Furthermore, thanks to the compatibility of VARIOKIT and PERI UP, safe work places and access to all areas were realised on the balanced cantilever equipment. With only a minimum of effort for the construction team, the scaffolding could be coupled with the VARIOKIT standard components using simple connecting means.
The close cooperation between PERI engineers and building contractor, GRANIT, was fundamental for ensuring the success of the project. At an early stage, the solutions were defined in great detail in accordance with project requirements along with training employees of the construction company in using the balanced cantilever method. In addition, PERI supported the logistics operations and delivered the required formwork and scaffolding materials to the jobsite on a just-in-time basis. On the construction site itself, PERI engineers were ready with professional support and advice throughout the project.
VARIOKIT balanced cantilever equipment
The PERI VARIOKIT solution for cantilever construction predominantly consists of rentable system and core components taken from the VARIOKIT Engineering Construction Kit. This allows the simple, rentable equipment adaptation to match different bridge cross-sections. The balanced cantilever equipment transfers the fresh concrete load into the previous bridge section and moves the formwork from section to section. In order to be able to meet the challenges presented by the cross-sectional changes of the hollow box cross-section, a formwork solution consisting of VARIO Girder Wall Formwork is being used.
With the PERI balanced cantilever equipment, segments up to 5.75 m long can be concreted. If this is taken into account during the bridge planning phase, enormous cost and construction time reductions can be realised.
Furthermore, operating the cantilever equipment is extremely practice-oriented. The integrated, centrally-controlled hydraulics facilitate a very easy moving procedure as well as problem-free assembly of the equipment and formwork thus resulting in a significant acceleration of the construction process.
All balanced cantilever equipment modules can be reused in future projects. In addition, almost all components are available in the PERI rental parks. This not only ensures rapid availability of all components but it also increases the cost-effectiveness of the solutions for the construction company.