How engineers test a bridge before it opens

A new bridge is designed with calculations, but engineers still check how the real structure behaves before traffic arrives.

Load testing

Loaded trucks are parked or driven across in planned positions to put a known weight on the bridge.

Measuring the bend

Sensors record how far the deck bends and whether it springs back. The results are compared with the design.

Inspections

Welds, bolts, bearings and joints are checked for defects before and after the test.

Monitoring for years

Many modern bridges keep sensors in place so engineers can spot changes long after opening.