Tag Archive for axle loads on bridges


This business case story below represents very innovative use of inexpensive smart technology to determine cost effective rail bridge capital budgets. Published case study in ASLRRA’s Tech Tracks –  “Short Line Railroad Saves CAPEX Funds with modern bridge stress and strain monitoring structural technology”

The Indiana Rail Road engaged an engineering consultant to provide a calculated load rating for a 100 year old multi-span bridge located in southwest Indiana. After a thorough visual inspection and a load rating analysis that uses AREMA visual inspection guidelines, the bridge was rated as unsatisfactory for the intended live loads. Report recommended rehabilitation of a number of main steel girders to achieve the required load rating. The consultant also suggested train speeds be reduced from 40 mph to a maximum of 10 mph.

Indiana Rail Road estimated the cost of the rehab to be approximately $2 million dollars. This bridge had been providing its customers with heavy axle freight service (32.5 metric tons per axle) with profitable revenues to the rail company. A critical business issue.

Indiana Rail Road asked for a second due diligence opinion.  Working  with Parsons, LifeSpan from Atlanta installed approximately 12 of its unique sensors on key structural elements. Next, the railroad ran known loads across the bridge to calculate a load rating based on actual structural response instead of just visual inspection. Data was collected on each run and the sensor peak channel manually re-set between runs.


The technology  captures both compression & tensile displacements/strain

Can measure up to 11mm of displacement (up to  95mm with special sensor)

With a resolution of 3 to 4 micron range (average human hair is 80 microns)

Capture crack width/propagation, displacement/strain, out-of-plane bending, deflection

Captures peak strain data without power source


RESULTS showed total stresses where within the allowable limits (AREMA).

The business lesson is that the use of advanced condition sensor technology can make a huge financial difference in a railroad’s capital budget.  In this example, $2 million.

Is your railway using this scientific approach to optimize your engineering budgets yet?

Using modern sensors to measure bridge risks

Using modern sensors to measure bridge risks