Evaluation of Prestressed Concrete I-Girder Bridge Design Software with NCHRP Process 12-50

Abstract

NCHRP Process 12-50 was used to evaluate and verify prestressed concrete bridge design software commonly used in Indiana. A test bed of 40 bridge structures was developed with input from practicing engineers and Indiana Department of Transportation (INDOT) specialists. The test bed included 20 simple-span and 20 multispan bridges. The primary parameters were bridge span, girder spacing, section type, strand pattern (straight or draped), and concrete strength. The remaining parameters were held constant with practical or consensus values provided by engineers or the INDOT bridge design manual. The section types included were AASHTO Types II, III, and IV and Indiana modified Bulb-Tee beams (54–78 in. deep). An indigenous computer program, PURDUE PSBD, was developed to implement the bridge design calculations specified in the AASHTO LRFD Bridge Design Specifications, which are currently endorsed by the INDOT bridge design manual. Both CONSPAN (the most common bridge design software in Indiana) and PURDUE PSBD generated calculation results for the complete test bed of bridges. The output from both computer programs was compared to identify assumptions and discrepancies from the AASHTO LRFD specifications. These comparisons indicated excellent agreement between the results from both programs for ( a) concrete stresses and deflections at service-level loads, ( b) nominal flexural strength, ( c) nominal shear strength, and ( d) initial camber and deflections. The test bed of bridge structures and the PURDUE PSBD program developed in this research are recommended for evaluating and verifying other bridge design software.