Stavros Niarchos Foundation Cultural Center – Opera Building – Canopy Deformation Monitoring Using Surveying Techniques

The ferrocement canopy of the Opera Building is made out of two 100m x 100m ferrocement skins: the superior one (top skin) and the inferior one (bottom skin); they are connected together by Ferrocement diaphragms and steel diagonal circular hollow tube sections. The Canopy Roof is supported by 30 columns through bolted connections to the column bases embedded in the concrete. Since depropping was not executed by removing the props (the number of props does not allow a controlled procedure) and took place by uplifting the canopy from the column heads, it has been required for an Automated Monitoring System (AMS) to be installed in order to calculate the deformations on canopy’s surface as a result to the uplift sequence.

For the needs of the canopy deformation monitoring, a surveying monitoring system has been developed consisting of the following parts:

• 68 Monitoring prisms installed on the canopy’s upper skin surface
• An Industrial Robotic total station
• A Control box
• An SQL data base.

In addition to the above, for the needs of the application a high accuracy network has been created into adjacent building, next to the projects boundaries and out of the zone of influence for reference measurements collection and station primary set up. The network has been established with the use of high accuracy monitoring prisms and it has been incorporated to the projects horizontal and elevation network.

In order to calculate the primary networks reference values, 3 days measurements were performed, 4 times per day. The temperature and the pressure were applied as ppm corrections, and finally the closure error that determines the network accuracy has been calculated on an average value of 0.9 mm ± 0.4 mm per benchmark.

The standard deviation error of the methodology is less than 2 mm.