PERI devised and supplied an optimised and safe formwork and scaffolding solution for construction of the Foz Tua Dam and the associated pumped-storage power station. The PERI specialists supported the construction firm, Barragem de Foz Tua, ACE, to ensure the build was completed on schedule and with precision, providing an elaborate concept, as well as logistical and technical services. This included continual coordination on site by the PERI Project Manager in addition to the PERI engineers' close collaboration with all project participants.
The dam in northern Portugal will reach a height of 108 m, while the dam crest measures 275 m long. From a formwork perspective, the particular challenge is caused through the complex design of the double curvature reinforced concrete structure with the 5-m-wide dam crest and its integrated overflow mechanism. The hydraulic circuit covers over 700 m along the right-hand bank of the river and includes two independent tunnels, as well as the subterranean power station with two reversible units.
The PERI complete solution – material and support from one source
With a complex project of this size the issue is to coordinate the diverse requirements of the build especially with a tight schedule and high material requirements. In addition to planning the formwork and scaffolding solution for complex geometries and high loads, one of the biggest challenges is strict compliance with the construction phase and cost plan for the gigantic dam project. To support the build PERI also deploys a Project Manager to the construction site, who acts as liaison between the Technical Office and the enormous construction team. While keeping in continual contact, this Project Manager makes sure all processes and works run smoothly in relation to formwork and scaffolding technology – especially for supply logistics as well. Thus, the profitability of the construction site is not only assured by the project-specific optimised equipment, but also by the continual controls and adjustment to material volumes on site. All processes relating to planning, logistics and formwork assembly are scheduled in detail by the PERI Project Manager and coordinated in depth with the actual construction sequence.
This PERI overall solution of planning, material provision and project management removes many interfaces and reduces frictional losses in the construction sequence. The contractor benefits from increased profitability in terms of time and costs.
The PERI formwork and scaffolding solution
PERI's engineers devised a solution of the SCS Climbing System and the VARIO GT 24 Wall Formwork for the double curvature dam. This combination is the ideal solution for the massive dam, as it facilitates both the single-face load transfer and the high finish requirements.
SCS enables single-face concreting by transferring the loads from the fresh concrete pressure without formwork anchors through the bracket into the climbing anchor of the previous concreting step. Thanks to the modular concept with multi-piece brackets, the SCS Climbing System can easily be adapted to the structural geometry. Large climbing units are possible due to the special load capacity of the brackets and high load factor of the anchoring, which ensures rapid progress on site. The working platforms with a useful width of 1.90 m remain horizontal despite an inclined position on the dam, creating extremely secure working conditions for users.
The highly flexible VARIO GT 24 Girder Formwork makes units with the platforms that can be moved by crane. The planned project-specific wall formwork also ensures the best architectural concrete results thanks to the planned arrangement of joints.
PERI also supplied a modified climbing and falsework solution for the highly complex geometry, such as the overflow area of the dam crest. The well-engineered design consists of systems components from the PERI rental park, making it particularly cost-effective: a combination of SB Brace Frames and system components of the VARIOKIT Engineering Construction Kit is used to form large platforms anchored in the hardened dam wall. These serve as an installation area for MULTIPROP Shoring Towers and SLS Heavy-Duty Props, which in turn support the inclined formwork units based on the VARIO GT 24 Girder Formwork.
The tried-and-tested TRIO Panel Formwork is the fast and best solution for the less complex wall structures of the dam, such as in the area of the dam galleries. The universal formwork system is designed for simple shuttering and to reduce shuttering times.
Moreover, the PERI UP Modular Scaffold is being used for diverse falsework and working scaffold tasks and for access solutions. The scaffold system with its metric grid arrangement and a multitude of practical details ensures secure erection and dismantling, as well as high safety during use. PERI UP Stairs with installation heights up to 55 m also ensure fast and secure accessibility to the working areas.
PERI Portugal also devised the right formwork solution for the reinforced concrete pipes of the hydraulic circuit. The two 700-m-long tunnels have varying cross sections from 5.50 m to 7.50 m. A standardised, self-supporting steel frame is being used as the basis for the two formwork carriages. The steel formlining is adapted based on the tunnel cross section. The equipment for manual processes and hydraulic control were planned in accordance with the specific construction site requirements. The steel formwork carriage enables the construction team to achieve the best concrete finish. The extremely robust structure is also very cost-effective thanks to the high number of use cycles.
About the Foz Tua pumped-storage power station
The Foz Tua pumped-storage power station is being built on the River Tua, an important tributary of the Douro. As part of the Portuguese national energy plan and with an investment volume of 370 million euros, the power station is intended to radically increase energy availability in the region. Construction work on the dam began in 2011 and is expected to take five years. Commissioning of the pumped-storage power station is already planned for 2016. The main investor EDP Energias de Portugal developed a detailed concept in collaboration with the experienced project offices COBA, QUADRANTE and architect Souto Moura, to minimise the environmental impact of this significant building project.