The Warsaw Voice » The Polish Science Voice » Monthly - August 29, 2015
Civil engineering
You have to be logged in to use the ReadSpeaker utility and listen to a text. It's free-of-charge. Just log in to the site or register if you are not registered user yet.
Keeping Bridges Safe
Engineers from the southern Polish city of Cracow have developed an innovative system for monitoring the safety of bridges that also collects data on traffic and vehicle loads.

The new system, developed by experts from Cracow-based engineering company NeoStrain, helps plan bridge repairs to make sure they are completed early enough to avoid more costly renovation work later.

The system uses special sensors that keep tabs on the technical condition of bridges, strain and other parameters measuring their safety for users. Special devices are installed to identify vehicle license plates and send data via GPS about drivers damaging roads to inspectors.

The “Hybrid system for monitoring the safety of bridges” project began in 2012 and runs for three years. Its focus is to design, produce and launch advanced measurement systems designed for the continuous monitoring of bridges. The project has been co-financed with zl.2.28 million from the National Center for Research and Development. The money came from the European Regional Development Fund under the European Union’s Innovative Economy Operational Programme 2007-2013. The total cost of the project is zl.7.2 million.

“We started out with random monitoring of bridges in Puławy, Wrocław, Bydgoszcz and Kwidzyn,” says Adam Komosa, the project’s manager. “Our systems monitored the deformations of the bridges and the stresses acting on them. Initially, we did not check the intensity of traffic or how it was influenced by heavy vehicles.”

Although the project operates along commercial lines, its managers are in constant contact with the technical universities in Warsaw, Cracow, Wrocław and Gdańsk as well as independent experts, Komosa says.

A stitch in time

Most bridges in Poland are managed by the General Directorate of National Roads and Motorways. Some are also overseen by city authorities. Institutions managing bridges need information on their condition and on how much longer they will be safe to use. Bridge managers also want to know how to schedule repairs early enough to avoid complex and costly renovation work later.

Most new bridges are absolutely safe to use and there is a large safety margin, Komosa says. Only about 20 percent of a bridge’s capacity is used on an everyday basis; in other words, a bridge can generally withstand loads that are five times the standard level. On the other hand, a bridge may no longer be safe to use if it is 50 or 100 years old. When bridge components need to be renovated or replaced, the question becomes whether it should be done for zl.200,000 in 10 years, or for zl.2 million later, Komosa adds.

The bridge monitoring system devised by the Cracow engineers is based on a set of sensors mounted in various locations. Some measure the stress on the structural supports. Road sensors examine the condition of the road surface. There are also weather sensors.

This “hybrid” monitoring system also weighs vehicles traveling on bridges. Sensors measure how the bridge sags under their weight, how it performs and what kind of impact this can have on the future stability of the structure. It is also possible to determine if vehicles are overloaded. A license plate identification system instantly sends information to road inspectors, which means every overloaded vehicle crossing the bridge is identified immediately. This information is transferred via GPS to the Road Transport Inspectorate, which sends the vehicle for weighing.

“The weighing must be performed on a stationary basis, on a certified pair of scales in a side parking lot,” says Komosa. “Overloaded vehicles damage roads. And a damaged road becomes badly profiled and begins to pose a threat in the event of an accident.”

The weighing system has been installed on several small bridges and is in the final stages of testing. This requires high accuracy, with the margin of error no greater than 8 percent, Komosa says. As the next step, NeoStrain plans to bring its system to larger bridges managed by the General Directorate of National Roads and Motorways and other authorities.
Karolina Olszewska