ST0301-CS040617 (2)
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CPL03243 Bethel Road Bridge, City of Coppell
Alternative one: close the street; redirect traffic; remove existing bridge and reconstruct
the bridge
. It may take a minimum of 6 months to remove and reconstruct the bridge so
rerouting the traffic will also need at least the same amount of time.
Alternative two: provide a temporary bridge; remove existing bridge and reconstruct the
bridge
. Construction cost and design effort for temporary plus permanent bridges will be
greater.
. Need more ROW for temporary bridge? May not be feasible to obtain additional
ROW.
. Additional design effort can be minimized, if contractor is responsible for the
design and construction of the temporary bridge is specified in the specification.
Additional design effort is still needed to provide the specification and the
associated work.
Alternative three: maintain one lane open during construction by removing existing
bridge and constructing new bridge at two stages
. Alternative 3a: remove existing bridge and construct new bridge at two stages
o Traffic on one-lane bridge needs to be managed. Management of traffic ---
may not be feasible.
o Existing bents (supported by two columns) cannot be removed until the
first half of new bridge built and open in operation.
o Vertical clearances (between top existing bents and bottom proposed
roadway) are not adequate for new I-beams; proposed roadway would
need to be raised
o Additional investigations/survey will be required upfront to obtain
sufficient data to allow demolition and reconstruction of existing
abutments.
o To maintain a viable roadway width and allow for traffic barriers, only a
small portion of existing deck can be removed so new deck has to be much
wider to accommodate future one lane of traffic
o Shallow depth of beams will extend length of bridge and increase cost
o Temporary shoring will be required to retain existing embankment after
existing abutments are demolished
o Shallow beams are not any cheaper since they are not used very often
o Construction cost and design effort will be greater. It may take an
additional 50% of design/drafting effort.
. Alternative 3b: retain and reuse existing bents and abutments, add additional
short piece of new bent and abutment at each side of each existing bent and
abutment
o Traffic on one-lane bridge needs to be managed. Management of traffic
may not be feasible.
o This approach can be accomplished by using same pan joists as existing
for new beams (same depth and spacing) so that no changes are made in
loading pattern (still uniform load). Add additional reinforced concrete on
top of the existing bents and abutments to improve existing members'
strength capacity.
o Considerable saving on construction cost due to no demolition on bents
and abutments; only new extension needed for the bents and abutments.
o To maintain a viable roadway width and allow for traffic barriers, only a
small portion of existing deck can be removed so new deck has to be much
wider to accommodate future one lane of traffic
o Further investigation is needed to ensure this approach is feasible to
construct.
o Current TxDOT standard drawings for pan joists and slab may not fit the
existing bents and abutments. Special design and drafting for pan joists,
bents and abutments may be needed
o It is risky without knowing the strength capacities of the existing members
(drawings for existing bridge are not available). Additional funds will be
required for non-destructive testing to determine existing reinforcing in
the existing members.
o Additional investigations/survey will be required up front to obtain
sufficient data to design the bridge.
o May need to redo the design using other approach, if investigations find
out that the existing members cannot support the proposed bridge loads.
o Construction cost and time may be greater due to more complex
construction approach is involved. Design/drafting effort will be greater. It
may take additional 50% of design/drafting effort.