BRIDGE REPAIR/REHABILITATION FEASIBILITY STUDY

Based on the 1997 load rating analysis, all members of the bridge have capacities in excess of
Operating Level capacities (see Appendix C.) As such, load restrictions and weight posting were
previously waived. Although the bridge does not currently require load restrictions, the load
rating analyses revealed that two elements of the bridge have load carrying capacities less than
the Inventory Level capacities. These elements are the shear capacity of the bascule span timber
stringers and the shear capacity of the Bent 7A timber bent cap that supports the bascule span.
Load capacities less than the Inventory Level capacities indicate that the structural member may
not have adequate capacity to carry current loading indefinitely and that degradation of the
elements under loading is eventually expected. Furthermore, in accordance with FHWA
guidelines, if the existing bridge was to remain and was rehabilitated, a design exception would
need to be granted to allow the members with substandard Inventory Level capacity to remain.
Otherwise the substandard members would need to be strengthened or replaced with stronger
members. According to the 2010 Structures Inspection Field Report, the condition of the bridge
has not changed sufficiently to warrant a new load rating evaluation.
4.1.4 Functional Evaluation and Roadway Safety
The existing bridge contains geometry that
is considered substandard (i.e. the
geometry does not meet current design
standards.) Specifically, the narrow 24’-0”
clear roadway width between curbs for
two travel lanes is considered substandard.
Because of the geometry, the bridge has a
Deck Geometry Rating of 2 (Intolerable
with a High Priority of Replacement) and
as such, the bridge qualifies as
“Functionally Obsolete”. In accordance
with FHWA guidelines, as the bridge is
also currently classified as “Structurally
Deficient” it cannot also be classified as
“Functionally Obsolete”. Bridges that
qualify as both “Structurally Deficient”
and “Functionally Obsolete” are classified
as “Structurally Deficient”. If sufficient
improvements were made to the deficient
structural members without corresponding
improvements to the geometric features,
the existing bridge would then be
classified as “Functionally Obsolete”.
Photo 3 - Approach Sidewalk and Guardrails
The existing bridge does not contain traffic railings that are crash tested in accordance with
NCHRP 350 as required by current design standards. Low-level curbs, such as the existing 1’-1”
high timber curbs, have a history of causing errant vehicles that strike the curb to lose control
and rollover. The traffic railings are required to meet Test Level 2 (TL-2) crash testing criteria
as a minimum, which are appropriate for use on local collector roads, with favorable site
Repair/Rehab. Feasibility Study March 10, 2011
Bridge No. C-07-001 (437) 12 Final Report