|Short description of the project
This sport facilities centre belongs to the municipality of Maldonado, Uruguay, in a no freeze, no snow climatic zone. This particular intervention, renovating the swimming pool, including the installation of a membrane roof and a heating system, was a part of a general project, improving and enlarging the existing sports centre.
For the membrane roof for the swimming pool, the following objectives had been determined:
- a special and attractive design to provide a distinctive design quality;
- allowing natural light (at least 7%) to enter, so the indoor area is not darkened;
- protection from wind and rain, so the swimming pool can be used all year long;
- eliminating direct solar radiation, that can disturb ongoing activities;
- and, last but not least, an easy installation.
For these reasons, a pre-stressed PVC polyester membrane has been chosen. Other traditional building systems and materials, such as glass, plastic, metal, and/or concrete, do not meet all these requirements. Some of these construction methods would block all natural light; others would lead to new problems, such as an increase of the interior temperature. More important, most of these materials would not offer the aesthetic and formal opportunities PVC polyester membranes have to offer. PVC polyester, as a translucent membrane material, complies with all the abovementioned objectives.
The membranes are made of threaded polyester PES HT 1100dtex, 5x5 threads per cm (12 threads per inch) with PVC coating, UV protection on the outside, a weight of 800gr/m2 (230oz/sqyd) and a breaking load limit of 30kN/m. (167lbs/inch).
Description of the design
The membrane roof project was, of course, designed to go with the rest of the building.
The eventual roof consists of a double curvature tensioned roof, in PVC polyester fabric. The membrane is stressed by wire ropes, and anchored onto perimetrical A-shaped saddles, made of 4” steel tubes with a base rotation axis. Moveable panels in transparent PVC close the roof structure.
The roof is generated between two cable families, anchored all around on the high and low points of the A-shaped saddles. One family of cables has a positive curvature, the other family a negative curvature, so eventually both cable families together generate a double curvature surface.
Another important aspect to this roof design is the concrete gutter. This gutter does not only collect the rain water, but also works as an anchorage for the structural elements. The loads of these anchor points of the membrane roof onto the building have been considered in the design. Moreover, it houses an air-conditioning injection tube on its inner side, and provides the fixture points for the sliding panels in glass and aluminium, 3m below.
Tensioning the membrane
The tensile system of the membrane is based on the rotational movement of the A-shaped saddles around their base axis, on both sides. This rotation tensions the cables, which in turn tension the membrane.
Construction works started with the concrete gutter.
Then the iron anchorages were placed, with high precision.
At the same time, the pre-assembling of the steel structure, the A-shaped saddles, was done at the factory, as was the preparation of the PVC polyester membrane.
When every thing was ready, the final installation was done in a two days, eventually resulting in an enjoyable space for sports.