This paper contains a discussion on the finite element analysis of cracks in welds connecting floorbeam back-up diaphragms and web plates of box tie girders in a tied-arch bridge. Comparisons of the finite element analysis and the field instrumentation results are made at selected locations, and for one typical position of a test truck. Drawing on the conclusions of the finite element analysis, contract plans were developed to retrofit the tie girder. Two previously unconnected edges of the diaphragms were connected to the top and bottom flanges of the tie girder. Also, the floor beam bottom flange was connected directly to the tie girder bottom flange.