Experimental Use of High Strength Reinforcing Steel: Fid-Bau Portal

Experimental Use of High Strength Reinforcing Steel

J. G. Newton / L. G. Walker

The design, construction and study of a full scale experimental overpass structure is reported. A-432 reinforcing steel having a minimum yield strength of 60,000 psi was used in the four span (55'-88'-88'-55') continuous haunched concrete girder unit. Ultimate strength theory was used in the design, and stresses were also checked by elastic methods. Electrical strain gages were installed at selected points on the reinforcing steel and deflection gages employing electrical strain gages were mounted on the completed structure. Oscillographic records of strain and deflection were taken for a series of live load tests. A three axle truck was used in the live load tests. Speed and lane position were varied for purposes of studying impact, stress distribution, vibration characteristics and deflection characteristics. Comparisons of observed and calculated stresses and deflections were made. A study of crack width and distribution was made at several times during the test program. Observed crack formation is compared with various crack prediction methods. Time dependant deflections were observed throughout the test period and compared with deflection predictions. The performance of the structure appears to be satisfactory. Crack formation is not considered excessive and observed strains indicate an adequate factor of safety against static failure. (Author)