Kirkaldy Testing Museum - Tay Bridge Disaster

Tay Bridge Disaster

Kirkaldy famously tested many samples taken from the first Tay railway bridge for the official Inquiry on the Tay Bridge Disaster. He confirmed that the wrought iron tie bars failed at their connections to the cast iron columns of the bridge, when he tested intact tie bars with complete lugs still attached. The attachments were cast iron lugs which fractured at the bolt holes, and numerous fractured lugs were found after the disaster lying on the piers. The critical strengthening elements were much weaker than had been supposed by Thomas Bouch, the engineer of the first bridge. They failed at about 20 tons tensile load rather than the specified 60 tons, and were a prime cause of the collapse of the bridge on 28 December 1879.

Since Kirkaldy tested several samples of each of the lower and upper lugs, he was able to show that they exhibited a range of strengths, the lowest results being caused by defects like blow holes in the cast metal. Thus some of the upper lugs were actually weaker than the strongest lower lugs, an observation confirmed by damage shown on the remains left on the piers after the disaster. He tested the wrought iron tie bars themselves, and they proved tough, as specified, although only slightly stronger than the cast iron lugs to which they were attached. The high girders were also made of wrought iron and had a very high tensile strength. They were found after the accident at the bottom of the Tay estuary and had sustained relatively little damage compared with the cast iron columns which supported them. Some were reused in local houses, and when they were demolished in the 1960s, some were removed to the Royal Museum of Scotland in Edinburgh, where they are on public display.