So first of all, tell us about your job – what does it involve?

I design new structures and investigate/repair existing structures ranging from bridges to buildings and towers. I’ve worked on various road and footbridges and, more recently, I’ve designed some large seawater tanks made from fibre-reinforced composites (for a research university) and performed seismic earthquake design for a buried building. Whatever the project, I am in contact with plenty of other people interested in the work including the client, the architect and various contractors. The biggest reward is, after putting in a lot of work and thinking about a range of issues, seeing something I’ve sketched actually built.

From an engineering point of view, what was special about the Iron Bridge for its time? What did it do that hadn’t been done before?

Built in 1777 to 1779, the Iron Bridge was the world’s first cast-iron bridge. At the time, it showed how this new cast-iron material could be produced economically and reliably and assembled into a lightweight structure.

The overall arch form of the bridge and the method of jointing were not new. In fact, the connections were made in a similar way to timber connections (after all, if you’re using a new material for the first time you don’t want to take too many bold steps). The key was that it showed others the strength and possibilities of cast-iron.

What’s the legacy of the Iron Bridge in your field now?

Today, in the structural engineering industry, the Iron Bridge is seen as heralding the start of improved and efficient construction. Although many subsequent bridges “beat” Iron Bridge with longer spans and less material (steel was developed, which is stronger and less brittle than cast-iron), it was the method of construction for which the Iron Bridge is remembered. It changed the thinking about structural design and construction from natural materials (such as stone and timber) site-assembled outdoors in dangerous conditions, to one involving standardised industrial components that could be fabricated and pre-assembled in a factory-like process off-site, thus greatly increasing quality, increasing safety and reducing construction time.

The Iron Bridge is a symbol of the beginning of a more engineered world, where design and calculation replaced trial-and-error, and when (noticing how this metal structure contrasts with its natural surroundings) a new aesthetic of economy and technology was born.