Collins performed bridge load ratings on MassDOT and municipally owned structures to determine their safe load-carrying capacity. Since 2012, Collins has analyzed and load rated over 70 bridges and culverts in the Commonwealth.
The general scope of work consisted of determining the maximum live load capacity each bridge structure can safely support for defined rating vehicles. All work was completed in accordance with Chapter 7 of the MassDOT LRFD Bridge Manual to comply with the National Bridge Inspection Standards (NBIS), 23 CFR Part 650 Subpart C, Section 650.303. The bridges consisted of several types and materials in the simple and continuous-span superstructure configuration and with non-composite, composite, or jack-arch type deck configurations. Some common types include steel stringer/girder, concrete slab, concrete T-beam, prestressed concrete box beams and I-beams, arch (concrete and masonry), concrete box culvert, and pipe culvert (steel and HDPE).
The ratings used the allowable stress rating (ASR), load factor rating (LFR), and load and resistance factor rating (LRFR) analysis methods, as applicable based on the method used to design each bridge. Following the rating analysis, the results were organized into a comprehensive load rating report. Recommendations were made for any corrective actions required to improve the safety or live load-carrying capacity of the bridge and were supported by calculations to show the improvement in the live load rating such repairs or modifications would make.
All load rating work was completed in accordance with the latest version of AASHTO, The Manual for Bridge Evaluation (MBE), and MassDOT’s LRFD Bridge Manual – Part I, (Chapter 7) (currently the January 2020 Revision). Rating and analysis software used include AASHTOWareBrR, CSiBridge, STAAD Pro, SAP2000, and Excel and MathCAD rating templates were developed.