Design Parameters o National Highway Route o 2500 vehicles per day (23% Trucks) o Major truck route between Great Falls and Billings o US Air Force Missile Route o Grain Elevator in Moccasin o BNSF Railroad Crossing o Accident cluster at bridge
New Bridge Requirements o New width = 40 feet o Increased railroad lateral clearance o Increased railroad vertical clearance o Avoid existing foundations (timber piles) o Minimize grade raise to catch slopes on existing approaches – avoid sliver fills and new R\W o Minimize traffic disruptions
What are our options? o New Bridge on Offset Alignment o New Bridge on same alignment using On-site Detour o New Bridge on same alignment using Phase Construction o New Bridge on same alignment using Off-site detour and ABC
Could Accelerated Construction work here?? o How long can we shut down bridge site? o How quickly can we build a new bridge? o How much building can be completed before with existing bridge in place? o Is there a reasonable detour route?
Possible detour route o Secondary Highways – wide shoulders / flat slopes o Similar detour length for thru-traffic o Detour through town of Hobson – school crossing o At-grade RR crossing in Hobson o Many local detours possible (County Roads)
o Contacts with o Town of Hobson - Mayor o Hobson School o County Commissioners o Trucking Industry – grain elevator o Air Force Base o BNSF Railroad o Road User Cost Calculations o Preliminary ABC Ideas o Contract Time Estimates o Local Events ABC Planning Efforts
What can we accelerate? What portion of construction takes the most time? o Foundation construction – 4 days/shaft or 4 piles/day o Drilled Shaft testing – 14 days before testing / longer if problems are encountered o Forming bent caps – 3 days each o Curing bent caps – 15 days per project o Deck forming – 20 days up to 300 feet o Deck curing and sealing – 28 days Allowing for some overlap……80 days for major items
Potential Solutions o Foundations o What can we do while traffic is on existing bridge? o What foundation types will work? o Forming and curing bent caps o What cast-in-place can be done while traffic is on existing bridge? o Precast end and intermediate caps? o Deck forming and curing o Full-depth precast deck panels o Partial-depth o Stay-in-place Forms
o What could be completed before detouring traffic o What would be accelerated while traffic is on detour route o What work could be done after traffic is moved back on new bridge Divided Work Into Stages
Work Prior to Detouring Traffic Drilled 4 shafts outside the bridge limits and behind the existing intermediate bents.
Cast struts/crash wall on top of and between shafts
Day 7 o Sunday – no work Day 8 o Span 2 – Set girders and deck panels
Day 9 o Span 1 – Set girders and half the deck panels Day 10 o Span 1 – Set remaining deck panels o Began forming closure pours
Day 11 o Bents 1 & 4 – Formed and placed backwalls o Formed deck panel closure pours Day 12 o Continued forming deck panel closure pours Day 13 and 14 o Saturday and Sunday – No work Day 15 o Adjusted deck grades o Prepare for deck closure pours
Day 18 and 19 o Removing form work and grinding joints o Fill low spots
Day 20 and 21 o Weekend no bridge work – building approach fills Day 22 o More grinding and approach fills Day 23 o Tying barrier steel o Test run with slip form Day 24 o Approach work Day 25 o Slip formed barriers o Final grading along RR tracks
Day 26 and 27 o More grading work o Approach rails Day 28 o Finished approach rails Day 29 o Opened to Traffic One day ahead of schedule (incentive/disincentive deadline)
Lessons Learned o Project scheduling was intensive o Design details are critical – things need to fit o Allow adequate tolerance on precast elements o UHPC is difficult to grind – reduce exposed area to minimize grinding o Have an Engineer on site during construction of critical elements – be prepared to make decisions
Questions?? Project Contact: Jeff Olsen email@example.com 406-444-7610
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