Bridge collapse is thankfully a very rare occurance, and that’s in no small part due to the rigorous and frequent testing of bridges across the world.
We’ve featured various ways that load cells take the lead in bridge monitoring. However, as Dr. Mehridat Makki Alamdari of the School of Civil and Environmental Engineering, UNSW Sydney points out:
“Around the world we have so many deteriorating bridges which are nearing the end of their service lives, but the various road authorities do not have enough funding to demolish all of these bridges and build them from scratch.”
The University team have a particular interest in bridge safety. Australia has over 53,000 bridges, from the iconic Sydney Harbour Bridge to small bridges on regional roads. Major bridges use a combination of visual inspections, CCTV, load cells and other sensors to constantly monitor movement and structural integrity. These effective but complex systems cost money to install, monitor and repalce on a regular basis.
For small, regional bridges, cash-strapped local authorities may not be able to afford the installation costs of monitoring systems, just at a point where the bridges are experiencing more traffic as they age. As Dr. Makki Alamdari said in an article on the University website:
“Unfortunately, some overloaded trucks make detours over these regional bridges to avoid weighing stations on more direct routes. This can cause significant damage to bridges in rural areas that aren’t built to take these loads.”
Drive my car
The University team have suggested an alternative method. In association with a team from Kyoto University, they created a custom-built vehicle loaded with sensors that can analyse the bridge by simply driving over it.
“The car is equipped with multiple accelerometer and load cells to measure the dynamic response of the vehicle once it is moving over the bridge as well as measuring the interaction force between the vehicle and the bridge. There is also a data-acquisition system on-board to log data in real-time. It can reach a speed of 10 meters per second, but for the best outcomes, tests show the vehicle speed should be kept at around 2 meters per second.”
According to Dr Makki Alamdari,
“The car will move back and forth many times to collect a rich dataset of the bridge. Once data is collected, they will be analysed off-line in the office to see if there are any anomalies compared to the benchmark state.”
This could be a major advance for reviewing and monitoring historic bridges around the world. For example, the oldest bridge in the UK with buildings on it is Lincoln High Bridge, built in 1160 AD .
The oldest surviving bridge is thought to be Tarr Steps in Exmoor National Park, built two thousand years earlier in around 1000BC. According to an answer at Quora:
“It is a “clapper bridge” , which means it is constructed with large unmortared slabs of stone resting on one another. There are 17 spans across 50m and the top slabs weigh 1-2 tons and are about 99cm above normal water level. The largest slab is over 2.4m long and is about 1.5 m wide.”
The oldest bridge is generally held to be the Arkadiko Bridge, also known as Kazarma Bridge, in Greece. It is an arch bridge built by the Mycenaeans between from 1600 – 1100 BC. The Arkadiko Bridge sat on an ancient route between the cities of Tiryns and Epidauros. It is still in use today.
Building bridges with monitoring systems
Over the years we’ve written about load cells for bridge data monitoring, including:
And one that really caught our fancy – bridges made from decommissioned wind turbine blades.
Load cells for new bridges of all sizes
Need to integrate monitoring into a new or existing structure? Contact us to discuss your requirements.