View of the open-grid shoulders, raised curb, and open grid sidewalk assembly located on both sides of each bridge.
View of the bridge deterioration caused by water and road salt seepage from the open-grid assembly above.
Combined Open-grid Steel Shoulder and Sidewalk Assembly
This unique design feature called for the combined open-grid steel shoulder with a raised curb and an open-grid steel sidewalk assembly. Although common to mid-20th century steel deck bridge design, this open-grid system was in limited use in New Hampshire.
While well intended, the open-grid shoulders and open-grid sidewalks led to a situation of accelerated deterioration which required continuous maintenance.
These open-grid areas on the bridge deck allowed water and road salt to freely enter the support structure causing the accelerated deterioration of the pile caps and piles (i.e., bents).
To view the 1954 design plans for both bridges as well as additional historic information go to the Historic Documentation page of this website by clicking on the link below.