Strengthening of an Existing Continuous-Span, Steel-Stringer, Concrete-Deck Bridge, HR-333, 1993

(1993) Strengthening of an Existing Continuous-Span, Steel-Stringer, Concrete-Deck Bridge, HR-333, 1993. Transportation, Department of


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The need to upgrade understrength bridges in the United States has been well documented in the literature. The concept of strengthening steel stringer bridges in Iowa has been developed through several Iowa DOT projects. The objective of the project described in this report was to investigate the use of one such strengthening system on a three-span continuous steel stringer bridge in the field. In addition, a design methodology was developed to assist bridge engineers with designing a strengthening system to obtain the desired stress reductions. The bridge selected for strengthening was in Cerro Gordo County near Mason City, Iowa on County Road B65. The strengthening system was designed to remove overstresses that occurred when the bridge was subjected to Iowa legal loads. A two part strengthening system was used: post-tensioning the positive moment regions of all the stringers and superimposed trusses in the negative moment regions of the two exterior stringers at the two piers. The strengthening system was installed in the summers of 1992 and 1993. In the summer of 1993, the bridge was load tested before and after the strengthening system was activated. The load test results indicate that the strengthening system was effective in reducing the overstress in both the negative and positive regions of the stringers. The design methodology that was developed includes a procedure for determining the magnitude of post-tensioning and truss forces required to strengthen a given bridge. This method utilizes moment and force fractions to determine the distribution of strengthening axial forces and moments throughout the bridge. Finite element analysis and experimental results were used in the formulation and calibration of the methodology. A spreadsheet was developed to facilitate the calculation of these required strengthening forces.

Item Type: Departmental Report
Keywords: Before and after studies, Design methods, Load tests, Posttensioning, Spreadsheets, Steel, Steel bridges, Strength of materials, Strengthening (Maintenance), Stringers, Trusses
Subjects: Transportation
Transportation > Bridges and tunnels
Transportation > Roads and highways
Transportation > Design and Construction
ID Code: 16285
Deposited By: Iowa DOT Library
Deposited On: 11 Mar 2014 11:59
Last Modified: 29 Oct 2014 12:07