Why prestressed concrete?

Prestressed concrete

The technique of prestressing consists of subjecting precast concrete parts to compressive stresses prior to its commissioning. It is achieved through steel cables that are tensioned and anchored to the concrete.

PACADAR, ECOVENTIA´s parent company, acquired in 1944 from its inventor a patent for the use of prestressed. Nowadays, the company is a leader in use of this technique.

The aim in the use of prestressed concrete is to increase the tensile strength of concrete by introducing an internal compressive stress, counteracting in part the tensile stresses caused by these loads on the structural element.

Usually, when applying this technique, high strength concrete and high tensile steels are used, given the magnitude of the stresses induced.

Advantages of prestressed concrete

In general, prestressed concrete has the following merits:

• Since the technique of prestressing eliminates cracking of concrete under all stage of loading, the entire section of the structures takes part in resisting the external load. In contrast to this, in the reinforced concrete, only portion of the concrete above neutral axis is effective.
• Since concrete does not crack, the possibility of steel to rust and concrete to deteriorate is minimized.
• Absence of cracks results in higher capacity of the structure to bear reversal of stresses, impact, vibration and shock.
• The quantity of steel required for prestressing about 1/3 of that required for reinforced concrete, though the steel for the former should have high tensile strength.
• There is a possibility of minimizing the thickness and edges by giving to prestressed concrete structures more lightness and slender than to those of reinforced concrete, and lowering the cost of it.

Features of the concrete tower

Due to all these reasons, the R & D +I department of ECOVENTIA decided to develop its concrete tower based on prestressing. Therefore, ECOVENTIA´s prestressed concrete wind towers have the following characteristics, which make it the best solution on the market in this field, both steel and concrete:

• Due to the mechanical ability of the tower given by the materials it has been made of and its design, ECOVENTIA´s prestressed concrete wind tower can be raised to immeasurable heights concerning other solutions in the market. That means greater energy production.
• Due to its modular design and a revolutionary treatment of the joints between its precast components, the assembly system is very simple, resulting in a substantial shortening of deadlines. In any case, the installation of a wind farm with precast prestressed concrete towers of ECOVENTIA is a critical path.
• The precast concrete tower has a high structural rigidity, high fatigue resistance and high damping. Those parameters has been maximized with our solution to support very high deflection and stresses to which wind towers are exposed.
• Our tower is designed in that way, so as , under any case of load, it had a linear behavior.
• Due to the volatility of steel prices in most markets, with the use of precast concrete tower, ECOVENTIA removes an important factor of economic uncertainty in the project given that the concrete is subjected, to a much lesser extent than steel, to fluctuations in raw material prices.
• The maintenance cost of our concrete towers is very low, in particular because of the prestressed concrete resistance to corrosion, since it does not crack during its lifespan, which precludes moisture entry.
• The frequency response of ECOVENTIA´s prestressed concrete tower can be varied to suit the requirements in each case without being forced to design within established frequency range.
• ECOVENTIA´s prestressed concrete wind towers can achieve a designed lifespan of 100 or more years, and this is just another parameter for the calculation. It makes this option economically attractive, as the ROI can be extended over time.
• The transport of the pieces that make up the tower is studied thoroughly in order to be performed quickly and safely and avoid seeking a special permit which could slow down the process.
• The pre-assembly of the components of the tower runs directly on the site, and final assembly is done in one day with a big tonnage crane that can be utilized to retrofit the nacelle and blades.