|Staging and early contracts.
- Getting work done earlier by starting earlier.
- Early steel contracts.
- Letting bridges on north end of project earlier (if money is available).
- Using steel in cold weather.
- Cold weather epoxy with precast boxes.
- 8 to 9 months to get segments.
- 170,000 to 190,000 ft2 of segmental bridges.
- Possibly change a segmental to steel.
- Need 100,000 ft2 of segmental to be economical - could change one ramp.
- Precast Segmental hasn't been done in MN yet - competition not there yet (more expensive).
- Takes a while to set up for segmental suppliers but goes good when set up.
- Precast piers.
- Ideas to get walls built faster.
- Tiebacks into R/W no good.
- Cast-in place (CIP) footing with precast stem.
- Emulation = CIP design converting to precast.
- Could go up to 30 ft.
- With CIP, footings easy, stems take longer.
- Secant walls (expensive, large quantity).
- Local precasters share responsibility with contractors.
- No room on project for casting yard.
- Set up precasting to be competitive.
- Enough volume on this project to bury cost of forms.
- Aesthetics with precast walls?
- Can precast anything that can be CIP (counterforts included).
- Precast counterfort walls done on 394.
- Give contractors option of CIP or alternate.
- Contractors required to design alternates.
- Alternates = CIP, MSE, MBW, tiebacks, crib.
- Just give the contractor the ground rules for walls then let them finalize design and const. (not sure of what you'll get in end - maybe allow only one type of wall).
- Have contractors submit designs for options before letting.
- Giving options may make for a crunch with design later. At this stage we'd want value engineering option.
- West wall on north segment will be critical - 1 mile on piles.
- With precast panels, could set up to 20 a day.
- Battered forms take extra time.
- Aesthetic of PC walls could be a tough sell (full height vertical joint ~ every 10 ft).
- MSE issues - temp sheeting retaining 8 ft' at abutments - ½ price of CIP - ½ time of CIP.
- How is sheeting pulled at MSE/abutment joint? Use temporary block out from abutment.
- MSE strap length = 0.7H - utility conflicts, settlement issues.
- Running long lengths of sheeting (only 8 ft high)? Good for contractor? Sheeting may not be needed if slopes are shallow enough.
- In Florida MSE walls cost $20/vertical sq ft.
- MSE walls good for different settlements, get costly when forming at top of wall, cast in place or precast option at top of wall.
- Slip form rail on top of MSE wall.
- Drainage considerations in MSE walls should not be a problem.
- Right now one large contract.
- May eliminate some small contractors.
|Small overpass bridges on north end (not on critical path).
- Precast slab structures to speed construction.
- Superstructures only being replaced.
- Stay in place precast deck panels on PCB, not on steel (reflective cracking)?
- MSE wall abutments.
- Pile footing, Spread footing.
- Close rail line for a while - side walls.
- Precast panels - need neoprene pad to set on, then make sure grout gets underneath to provide a solid bearing (solid bearing most important - need gap over beam from edge of neoprene to edge of panel).
- Decking a bridge doesn't take that long if there aren't traffic issues. Time of pulling forms would be saved.
- Monolithic, precast decks prefabricated on beams (German construction).
- Stage the Lyndale Bridge so that it can all be built at once - may not be an issue because there will be a lot of room to work (100 ft) - may be better for traffic if built all at once.
- Segment weight = 55T - 60T, 250T crane to lift.
- Placed by crawler crane.
- 1 to 2 hours to get one segment placed.
- Four segments during 8 hour shift, temporarily constructed - need to post-tension later.Traffic OK with temp PT installed.
- The more segmental bridges, the better for the segmental contractor.
|Bridge type specifics.
- Br 27V73 - make it segmental to match 27V66?
- Need to widen retaining walls.
- Too small to make same size segmental as other five.
- High performance concrete and steel.
- Self-compacting concrete (no vibration needed, give up strength, tougher for field applications).
- Use 12 in CIP, try to get 75T.
- Shallow foundations may not work because of future excavations.
- Sheeting incorporated into foundations to be left in place - tie into footing.
- Slurry trench - more expensive, harder.
- Why design for worst case? H-pile in front of footing, lagging later if excavation needed. Drilled shafts for piers - possibly 1-8-footer for each pier, soil may be better for shafts on east end of commons.
- Works for segmental.
- Need temporary footing of bracket off column for temporary erection.
- Driven piles (18 in).
- Load tests prior to letting.
- Huge point loads in footings (not always economical - tougher design).
- Use heavy wall sections (3/8 in wall on Wakota).
- Drive 12 in heavy wall to more than 96T
- Use prestressed piles with steel prices on the rise.
- Augercast piles - no vibrations, no problem with water table, just very messy when close to water, need computer automated monitoring, increased inspection demands, 100T at 18 in.
- For speed of construction use high capacity piles and pour cap quickly.
- Precast piles may not be ideal for MN with varying depths of soil layers.
- Room for pile load test?
- $60K - $80k for auger pile test.
- Deep soil mixing?
- Micro-piles (5-8 in diameter) $100/lf - too expensive.
- Drilled shafts have been done in MN recently - could be cost effective, some don't like crosshole sonic logging (CSL), $1K to $2K per test, doesn't replace testing.
- Waiting period on fills - no, maybe 72 hours at the most.
- Light weight fill to eliminate settlement periods.
- Construction questions:
- Consider other types of walls.
- Bringing in fill may limit rate of construction - incentives for speed of construction.
- MSE walls are quickest and cheapest.
- R/W not an issue on fill situations, other options considered in cut situations.
- Utilities can't be under MSE straps, transverse crossing wouldn't be an issue.
- Also no trees on top of MSE walls.
- Use soil nailing under frontage road near 46th Street.
- Walls on north end.
- Precast wall types.
- Stability of foundations for future excavations.
- 1 mile of walls on piling - may control rate of work.
- Final Recommendations:
- Contractors would need list of acceptable wall types in proposal.
- WY tee detailed to 30 ft.
- High cost, $80/sq ft (high because of long hauling).
- Glen Canyon.
- Michael Culmo has sketches - will be quicker but not cheaper than CIP.
- Aesthetic considerations.
- MSE = $25/sq ft.
- CIP = $50/sq ft.
- Precast = $50/sq ft.
- Staging is the issue.
- Project must be all DB or none.
- Use at abutments to shorten span lengths.
- Shorten east end span and put another span on the east end?
- Can't lengthen because we'll get into exiting ramp too much.
- Split bridge along gore area, stagger abutment.
- Precast box vs. steel.
- Future painting of steel.
- Fracture critical steel cap.
- PT Concrete cap.
- Redecking segmental is an issue, not an issue with beam bridges.
- Erection not an issue for either.
- Consider weathering steel.
- Need to paint too.
- Removal of precast segments - the whole thing may come down if things go wrong, with beams can better control things.
- Aesthetics issues with mixed superstructure types on flyovers.
- If bridge needs to open in spring 2007, bridge may need to be steel.
- May need early steel contract.
- Steel tub section vs. steel I-section.
- North end of bridge controlled by retaining wall heights (approaching 50 ft).
- Make other flyovers steel if this one needs to be steel.
- Construction questions:
- Use steel for this bridge?
- When does it need to be done? - Stage 0 (says construction staging).
- Can't start till 2007 now, could start a year earlier if steel used.
- Could also benefit by changing location of piers for bridge 27V79 - get farther from travelways (reduce lane closures).
- Bridge open by spring 2007 to save the time.
- Use CIP box superstructure.
- More money than early steel because have to pay for whole bridge.
- Steel box cost 20 percent more than steel I-girders, and more difficult to erect.
- Steel box may end up being economical with less steel because of torsional resistance.
- Approximately two tubs would be required if tubs are to be used.
- With tubs, lose deck inspection access.
- Recommendation: When could seg bridge realistically be opened?
- Cast Jan, Feb., March, April.
- Erect March to June.
- Deck, railing - June, July.
- Open August 1, 2007.
- Steel bridge be opened.
- Piers and abuts July, August, September.
- Questionable to open by fall 2006.
- Let this bridge on its own.
- See bridge type specific notes.
- Widen out to use precast section?
- Would have two small cores and four large cores for casting.
- If made segmental - Stage 1 - four bridges (180 large segments, 91 small segments - could this be done), Stage 2 - two bridges.
- 6-8 months lead time to cast stage one segments, first segment comes off in 6 months.
- Number of different sections (two) is not an economic issue.
- Load restrictions, onsite casting maybe at a location where weight restrictions are an issue.
- Spend first year doing substructures then ready for segments (do-able).
- Geotech questions:
- Shorten bridges by eliminating cross slopes.
- Use MSE walls to do this.
- Drive piles so beams can be set before MSE walls built.
- Use 30 ft approach panels for compaction issues behind MSE walls.
- Spread footings on bridges.
- Self compacting concrete - works best in precasting yards where there is more control.
- Usually lose strength.
- OK for drilled shafts.
- No real advantage for field applications.
- High performance steel - silent in new code.
- High performance concrete.
- High fly ash.
- Silica fume.
- Already used by Mn/DOT.
|RR Bridge (27V74).
- Build bridge off site then haul into place.
- Salvage existing substructures.
- Rigid frame structure.
- Conspan structure.
- See bridge type specific notes.
- Bridge 27V75.
- Needs to be steel only 8 months prior.
- Probably done by fall 2006.
- Box vs. I-girder.
- Done by July/Aug 2007.
- What really is the critical path?
- Retaining Walls.