Bridge Safety Initiative: Slab Bridge Load Rating using AASHTO Methodology and Finite Element Analysis AASHTO RAC/TRB 2011 Summer Meeting Prepared by Dale Peabody

The Challenge  MaineDOT is responsible for 2,723 bridges and minor spans  271 are in poor condition  226 are structurally deficient  Nine percent of Maine’s bridges are over 81 years old and 37% are over 61 years old.

The Challenge  288 bridges are at risk of closure or weight restrictions in the next decade  Balance public safety and socioeconomic concerns over bridge closure and load restriction decisions  Replacement costs for a single small bridge can exceed $1 million

What We Did  Develop Finite Element Analysis program for concrete slabs - SlabRate  Conduct Finite Element Analysis on bridges with potential load restrictions  20 flat slab bridges evaluated to date  13 with unacceptable load ratings are deemed acceptable w/SlabRate

What We Did  SlabRate’s FE formulation validated using widely accepted commercial FE codes  Further validation to be done with live loading analysis

Benefits  SlabRate – models can be generated and solved in a few minutes  SlabRate – analyzes 1 to 5 span continuous slab bridges, multiple user defined rating vehicles, highly intuitive graphical user-friendly display  Thirteen of 20 bridges analyzed will not require load restrictions, repair or replacement

Benefit/Cost  SlabRate development and analysis of 20 bridges - $200k  Assume just one out of the 13 bridges will not need to be replaced - $1 million B/C = 5 B/C = 5  Assume two bridges avoid replacement B/C = 10 B/C = 10