Engineering students from the University of Minho in Portugal are currently researching the structural behaviour of the unique wrought iron frame that holds the stained glass in the South Oculus window in Canterbury Cathedral. The framework, which dates to the late 12th century, is a one-of-a-kind medieval engineering solution to the problem of spanning a 4.5 meter opening in the building. The construction of two interlinked iron frames, one to hold the stained glass panels, and one to provide lateral stability, resembles a modern ‘space frame’, which to date had been thought to be a 20th century invention.
This fact that the Canterbury builders got there nearly 800 years earlier has created interest internationally. In the week before Easter, Prof. Paulo Lourenço, one of his PhD students and one of his MSc students visited the Cathedral to undertake tests on the metalwork of the window.
By attaching vibration sensors / accelerometers (very similar to seismometers) and measuring slight vibrations in the metal framework they will be able to create a virtual model of the structure from the actual on site measurements. This will then help them to understand the behaviour of the window when wind forces act upon it, and to assess its structural strength. These sensors are also used to monitor the behaviour of buildings during earthquakes.
Although we will have to wait until later this year for the study to be finished, early indications are that the metalwork in the South Oculus seems surprisingly stiff and immensely strong – not bad for 800 year old iron!
For more information about the Advanced Masters in Structural Analysis of Monuments and Historical Constructions, go to http://www.msc-sahc.org/