KCI provided bridge and ancillary structure inspection and engineering services for the Maryland Transportation Authority (MDTA) under this $8 Million open-end contract as part of a joint venture. During alternating cycles, KCI performed 46 visual and hands-on bridge inspections, eight underwater inspections, as well as hundreds of sign structure and high mast light inspections, as well as traffic safety feature inspections of seven miles of interstate highway. All structures inspected were part of the I-95/I-395 system within Baltimore City, as well as the Hatem Bridge, which is a major river crossing in northeastern Maryland. This contract included the development of comprehensive bridge condition inspection reports in coordination with numerous engineering firms that performed these services for MDTA on three concurrent inspection/engineering service contracts.
Bridges on I-95 and I-395. Field teams inspected approximately seven miles of elevated highway with 59 mainline, interchange, and ramp structures consisting of multi-span plate girder bridges, rolled steel beam bridges, curved steel box girder bridges, and prestressed concrete box girder bridges over and under I-95 and I-395, several city roads and parking lots, Middle Branch of the Patapsco River, Gwynns Falls, CSX railroad tracks and yards, and private properties. Nearly half of the structures are steel box girders that required confined space entry procedures, and several structures had steel straddle bents, which required close inspection since they were fracture critical and required confined space access to inspect them internally. Access to all structures required a combination of snoopers, man lifts, ladders, and boats.
Thomas J. Hatem Memorial Bridge. KCI’s structural engineers inspected 24 approach spans of the 7,600-linear-foot bridge, which carries US 40 over the Susquehanna River between Harford and Cecil Counties in northeastern Maryland and includes a three-span trussed arch main channel crossing with a suspended deck and floor system in the middle span, supported by vertical members connected to the truss system by conventional riveted gusset connections. Structures were composed of continuous steel Wichert truss-girders supporting a floorbeam and stringer system. The fracture-critical truss-girders and floorbeams received a detailed hands-on inspection, with a focus on fatigue-sensitive details (FSD). Following the condition inspection of the accessible portions of the structure, actionable repair/rehabilitation items were coordinated with the contractor that was on-site.
Gusset Plate Analysis for the Francis Scott Key Bridge. In the aftermath of the collapse of the I-35W highway bridge over the Mississippi River in north Minneapolis, MN, the National Transportation Safety Board (NTSB) and the Federal Highway Administration (FHWA) issued recommendations and guidelines for owners of bridges within the National Bridge Inventory to conduct assessments for the load carrying capacity of gusset plates. KCI analyzed 50 of the 89 typical truss joints for the Francis Scott Key Bridge. The truss portion of the four-lane bridge is a 2,640-foot, three-span continuous truss unit with a 1,200-foot main span and suspended deck. The truss unit contains a total of 352 joints with gusset plates.
Because the FHWA design guidelines were under development with multiple updates throughout the duration of the analysis, structural engineers performed continuous research to ensure the analysis was being conducted based on the latest guidelines. KCI developed project analysis tools to implement an economical and efficient approach to the assessment of the numerous plates and multiple modes of failure in the plates. The gusset plates were evaluated for multiple modes of failure. Field measurements were obtained for a select number of joints to validate shop drawings and as-built plans. The analysis methodology and results was summarized in a comprehensive report that contained the analytical results and a graphical representation of the results, presented as Demand-to-Capacity (D/C) ratios for an easy comparison to the code specified permissible limits.