In some cases the corrosion is similar to an extensive pitting. While there may not be a major concentrated loss of cross section in these H piles, the steel H piles have lost significant axial and bending strength and must be repaired and strengthened to restore the original strength of the steel H pile. However, such restoration to original capacity is not an easy task.
One approach to repair and strengthen steel H piles is by welding additional steel plates or shapes such as C Channels or steel angles to the deteriorated pile. Such repairs have their own problems. First, welding of new steel sections under water is a difficult and expensive task. Secondly, the difference in metals between the original steel H pile, the new steel sections and the weld material can lead to galvanic corrosion. Such repairs are not a permanent fix.
In August 2011, Texas DOT initiated a research study (Project:0-6731- Repair Systems for Deteriorated Bridge Piles) to evaluate some of the techniques for strengthening of corroded steel H piles. The 3-year study consisted of two parts. Structural performance of the jackets for both reduced- and full-scale piles was given to the University of Houston. Texas Tech University was given the task of evaluating the durability of the system. The small-scale tests of H piles were conducted first. To simulate corrosion, different percentage of cross sections from the webs and flanges of these seven H piles were removed. The researchers wanted to perform the repairs in conditions closely resembling field conditions. The steel H-piles were placed inside a large steel tank that was filled with water. The damaged portion of the H-piles were wrapped in PileMedic® carbon laminates to create a solid seamless shell. Next, the portion of the H pile that was wrapped was filled with PileMedic® underwater grout. The pile was allowed to remain in that position while the grout cured.
Testing of the large-scale H piles consisted of placing the specimens inside a test frame. Concentric axial load was applied to the repaired piles. In a sample specimen, 40% of the web area and 20% of the flange area were removed to simulate corrosion damage on the steel H pile. The test had to stop after the jack applied a load of 658,400 pounds (2,930 kN) because the jack had reached its limit and could not provide any additional load! Nevertheless, the research team leader, Prof. Dawood, concluded that "at a minimum, the PileMedic® system restored the capacity f the deteriorated pile to its initial undamaged capacity". The final report on this study is available in pdf format here.
Using a combination of unidirectional and/or biaxial fabrics, PileMedic® laminates provide strength in both longitudinal and transverse directions.
PileMedic® is very thin; with a thickness as small as 0.01 inch, it is flexible enough to be wrapped around corners of square columns
PileMedic® laminates are manufactured in plants under high quality control standards; this improves the quality of the finished construction.
The repairs can be completed much faster in the field.
The strength of the laminates can be tested prior to installation.
The number and pattern of the layers of fabrics in PileMedic® laminates can be changed to produce an endless array of customized products providing different strength values along the height of the pile or in the hoop direction.
Additional coatings to the surface of the laminate can be added for abrasion and UV protection.
"Piles are now being repaired in an hour compared to a day." — Navy Commander
"In a business where compliments are few and far between, I would like to assign credit to a few good men. I would like to thank your exemplary employees, as they championed this project from start to finish with enthusiasm unknown to most construction work.” -Inspector, Salt Lake City Department of Public Utilities