BRIDGE CONCERNS By WILLIAM T. SUNLEY, Engineer of Local Roads and Streets Illinois Department of Transportation Credits to: Richard Mochel, Local Bridge Engineer

All bridges open to public travel must be inspected at least every two years. This is a requirement of the National Bridge Inspection Standards (NBIS). The Federal Highway Administration (FHWA) is charged with the enforcement of the NBIS and is very interested in the states' efforts to assure inspection and maintenance of structures in a serviceable condition.

Illinois has been very active in the effort to make bridges safe. Inventory, inspection, maintenance, repair, rehabilitation and replacement are all words associated with bridges. To get the job done requires active participation of many state and local agency employees. With all the new emphasis on specialized inspections and follow-up, even more time and effort will be needed to get the bridge inspection job done.

The following is a list of the various types of inspections required.

Biennial Inspections — All 17,000 local agency bridges in Illinois must be inspected at least every two years, as required by the National Bridge Inspection Standards (NBIS). Inspections must be performed by qualified inspectors and the results must be reported to the IDOT District office for inclusion in the Illinois Structure Inventory System (ISIS).

Underwater Inspections — This inspection requirement for bridges was emphasized in the latest revision to the NBIS. Details are contained in the Bureau of Local Roads and Streets Circular Letter 89-3, dated January 23, 1989 (Circular letters referenced in this article are policy and procedures letters sent to municipal and county highway agencies as well as consultants). Inspection procedures are provided in Circular Letter 89-41 dated November 30, 1989. Records indicate that about 129 bridges are included in this group. Circular Letter 90-31, dated October 12, 1990 was issued as a reminder that all inspections must be completed and the data entered in the ISIS by January 1, 1991. To date 91 bridges have been completed. Additional effort is needed to attain full compliance.

Fracture Critical Inspections — Revisions to NBIS adopted in 1988 require that all fracture critical members of bridges be inspected at regular intervals. Each affected bridge must be identified and inspected by January 1, 1992. Guidelines and other information regarding this specialized inspection are contained in Circular Letter 90-25, dated August 17. 1990. About 1, 133 structures fit into this category. To date, 20% have been inspected.

Scour Evaluation — FHWA, through a Technical Advisory entitled "Scour at Bridges", requires that all bridges over water be evaluated for scour. This affects 14, 000 existing bridges in Illinois and those being designed. We met with FHWA, county and municipal officials to work out an implementation plan, and Circular Letter 91-3, dated January 25, 1991 was issued to address bridge scour screening, evaluation and design. In response to subsequent local agency concerns, the scour screening guidelines were revised to relax and clarify the requirements of the screening. These revisions were issued by Circular Letter 91-8 on June 7, 1991 which supersedes Circular Letter 91-3. Local agency structures must be screened to determine the potential for scour and this screening must be completed by December 1, 1991.

This office has ongoing programs to train and assist the local agencies in developing qualified bridge inspectors. We offer a two week inspector training class that qualifies individuals with five years experience to be certified bridge inspectors. A courst to train inspectors in fracture critical inspections has been offered four times in Illinois. One day training in bridge inspection and bridge repair is also offered annually to update individuals on the latest methods of inspection and repair.

Bridge concerns are all around us and the 1990s will see more emphasis on this important issue. If you haven't trained employees to be qualified inspectors, sign up for the courses at the first opportunity. If you don't have the staff to do the inspections, expecially the specialized ones, then consider hiring a qualified consultant to perform the work. The Bridge Unit in the Bureau of Local Roads and Streets also offers support in the rating of structures, so call this office if you have bridges that require rating. If you have any questions regarding bridges call Rich Mochel, Local Bridge Engineer at (217) 782-5928 for assistance. •

July 1991 / Illinois Municipal Review / Page 9