Post Tension Cable Locating in Concrete Beams
in Orlando, Florida

GPRS was contacted by a large steel company located in Orlando, FL to mobilize to a project near the Orlando International Airport. The steel company had an interesting project. Currently there is a 30’x30’ opening in between two floors at an office tower near the Orlando Airport. The opening was originally used as a staircase between two floors. The new tenant of the space was only going to utilize one floor and wanted to have the floor filled. The steel company planned to mount steel bracing to 4 cast-in-place concrete beams found on each side of the floor opening. The steel bracing would then be used to hold metal pan decking for a new concrete pour which would fill in the 30’x30’ opening. 

The project seemed simple enough however the steel company knew that each of the beams contained post tension cables. Their anchor system for the steel beams would require them to drill about 6” into the concrete beam thus risking them drilling directly into a post tension cable in the beam. In order to locate the post tension cables in the concrete beam the steel company contacted Ground Penetrating Radar Systems, LLC. based in Orlando, FL. GPRS mobilized to the site and set about performing the ground penetrating radar survey.

Ground penetrating radar is a versatile technology. In contrast with X-Ray GPR only needs access to one site of the surface being scanned. Also, because of the small size of the specific antenna by GPRS the radar can be rolled over ceilings, and vertical surfaces such as the sides of beams.  Additionally, ground penetrating radar offers pin point accuracy (+/- ¼” to the center of the object being located as well as 10% margin of error when determining the depth). Considering these factors ground penetrating radar was the perfect technology for the steel company’s project.

Once on site GPRS was able to mark the beams and definitively locate the placement of the post tension cables. The cables were marked on the sides of the beams and depth indications were provided. After the layout was complete the steel company was able to plot the location of their anchor points and ensure that they will not drill into any of the cables in the beams. You can see pictures of the post tension markings below.

All in all the steel company was pleased with the results of the survey. For the last 10 years Ground Penetrating Radar Systems has specialized in locating post tension cables (as well as other types of reinforcing steel) in concrete prior to core drilling and saw cutting. If you would like more information or to request a quote, please contact your local rep.