Our R&D on confinement and repair of bridge columns with FRP jackets started over 20 years ago. We were the first team of researchers funded by the U.S. National Science Foundation to study repair and retrofit of columns and bridge piers with FRP wraps. Keep in mind that the first generation of FRP jackets we used in the 1990s to wrap those columns was far inferior to the newly-developed PileMedic™ system that we introduced in 2010. The earlier “FRP wraps” were, for example, very narrow and the uniaxial, meaning the fibers could only be positioned in the hoop direction to provide confinement for the column. In contrast, the new PileMedic™ has a biaxial construction so the laminate can not only provide confinement but it can also contribute to the flexural capacity of the column.
Referring to some of the earlier studies we published on tests of circular columns, this improvement is shown when you compare Figs. 9 and 10 with Fig. 8 or when you compare Fig. 12 with Fig. 11. In all cases, the enhancement caused by the confining wraps is substantial.
In another paper on rectangular columns, we studied the effects of keeping the same rectangular shape or enlarging the column cross section into an oval shape (Fig. 5). Another variable was whether the resin in the annual space was placed under gravity alone (passive confinement) or pressurized to place the jacket in tension from the start (active confinement). Fig. 10 is the response of the same column shown in Fig. 9 after it was wrapped. Likewise, Figs. 12 and 13 show the improvements on the behavior of unwrapped column (Fig. 11).
Finally, many of the unwrapped circular and rectangular columns that were damaged at the conclusion of the initial tests, were subsequently repaired by wrapping and re-tested. This portion of the study was aimed at showing the effectiveness of FRP wraps in repairing unretrofitted columns that are damaged in an earthquake. As seen in Figs. 12, 13 and 14 deteriorated columns could also benefit significantly from such repairs with FRP jackets.
Following two decades of R&D and learning from numerous field installations, I have developed a new FRP product (www.PileMedic.com) that offers an amazingly simple yet strong and durable solution for repair of deteriorated piles and columns in buildings, bridges, water and waste-water facilities, industrial plants, underwater piles, etc.
The advantages of this system include:
1) 3-4 times stronger than steel
2) Increase axial capacity beyond original strength of column
3) Protects the column against future corrosion
4) Provides structural confinement
5) Does not corrode
6) No metallic parts
7) Available in carbon or glass
8) One size fits all piles (no delays for customized jackets)
The Missouri DOT was so impressed with our product that a few days after our demonstration they placed an order to repair 48 additional piles with this system. Those 48 columns were completed in November 2010. Not only this was the most economical alternative, it allowed them to do the repairs with no road closure or traffic control and without bringing any heavy equipment to the jobsite (Please click here to read the article).
As you notice from the Miami project listed below, PileMedic™ works equally well for repair of underwater piles. We are currently working with several port authorities to set up underwater pile strengthening demonstrations projects.The table below contains a printed pdf sheet and a short video for each project.
|Description||Flyer in PDF||Short Video|
|Restoration of Structurally Deficient Bridge Piers for Missouri DOT||Flyer||Video|
|Repair of Deteriorated Underwater Piles in Miami, FL||Flyer||Video|
|Repair of Corrosion Damaged Steel Columns for Tucson Electric Power Company||Flyer||Video|
|Tests of Earthquake-Damaged Concrete Bridge Piers by Caltrans and NSF||Flyer||Video|