Timber Abutment Piling and Back Wall Rehabilitation and Repair Timber Abutment Piling and Back Wall Rehabilitation and Repair

Research Project


Timber Abutment Piling and Back Wall Rehabilitation and Repair

Timber abutment piling on a low volume road bridge in Black Hawk County, IA


Principal investigators: Brent Phares, 515-294-5879, bphares@iastate.edu (project list), Iowa State University

Co-principal investigators:

Project status


Start date: 03/01/10
End date: 09/30/12


Report: November 2012, Timber Abutment Piling and Back Wall Rehabilitation and Repair 7.72 mb (*pdf)

Related publications: Timber Abutment Piling and Back Wall Rehabilitation and Repair 1.51 mb *pdf November 2012

*To read pdf files, you may need to download the free Adobe Acrobat Reader.


Sponsor(s): Iowa Department of Transportation
Iowa Highway Research Board

About the research


Based on previous National Bridge Inventory data, the state of Iowa has nearly 20,000 bridges on low-volume roads (LVRs). Thus, these bridges are the responsibility of the county engineers. Of the bridges on the county roads, 24 percent are structurally deficient and 5 percent are functionally obsolete. A large number of the older bridges on the LVRs are built on timber piling with timber back walls. In many cases, as timber abutments and piers age, the piling and back wall planks deteriorate at a rate faster than the bridge superstructure. As a result, a large percentage of the structurally deficient bridges on LVRs are classified as such because of the condition of the timber substructure elements.

As funds for replacing bridges decline and construction costs increase, effective rehabilitation and strengthening techniques for extending the life of the timber substructures in bridges with structurally sound superstructures has become even more important. Several counties have implemented various techniques to strengthen/repair damaged piling, however, there is minimal data documenting the effectiveness of these techniques. There are numerous instances where cracked and failed pilings have been repaired. However, there are no experimental data on the effectiveness of the repairs or on the percentage of load transferred from the superstructure to the sound pile below.

To address the research needs, a review and evaluation of current maintenance and rehabilitation methods was completed. Additionally, a nationwide survey was conducted to learn the methods used beyond Iowa. Field investigation and live-load testing of bridges with certain Iowa methods was completed. Lastly, laboratory testing of new strengthening and rehabilitation methods was performed.

2711 S. Loop Drive, Suite 4700, Ames, Iowa 50010-8664
Phone: 515-294-9501 ~ Fax: 515-294-0467
The Bridge Engineering Center is administered by Iowa State University's Institute for Transportation.

Bridge Engineering Center logo

Timber Bridge Program Structural Health Monitoring Current Projects Completed Projects About BEC Staff Students Related Links

Iowa State University logo and link