When buying steel beams for use in the UK, earthquakes might not seem like a top priority; but figures from the British Geological Survey show there have been 20 earthquakes recorded in the British Isles in the last 50 days alone.
The largest of these measured a magnitude of 3.5 on the Richter scale, and occurred in Oakham, Rutland, on April 18th – one of three in the area, all of which were felt by people who were there at the time.
Even larger earthquakes are not wholly uncommon, such as the magnitude 5.2 quake that hit Market Rasen in Lincolnshire in February 2008.
But what factors affect the performance of steel beams against near-field earthquakes – that is, earthquakes that occur within a few tens of kilometres from the structure?
Research published in the Journal of Constructional Steel Research suggests that flange thickness plays a crucial part in allowing steel beams to withstand the deformation and forces applied to them by a near-field earthquake.
The authors suggest that the forces that occur can be akin to a Newton’s Cradle – the arrangement of five suspended balls in which the force of one end ball falling is transferred directly to the opposite end, sending the fifth ball into the air.
In steel beams, flange thickness and buckling of the flange, along with the yielding ratio, all combine to predict how well the structure will withstand such forces without brittle failures.