minn i35 replacement stepbystep
TRANSCRIPT
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7/21/2019 Minn i35 Replacement StepByStep
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Abutment 1
Pier 2Main Span
11 25
Pier 3
Superstructure
Pier 4 Abutmen
Mississippi River504 242 147330
90 4
11
SafetyShouldersSafety
Shoulders12 12 12 12 12
I-35W St. Anthony Falls Bridge
Constructing the 504 main span over theMississippi River The new bridge consists oftwo adjacent structures; one will carry northboundtraffic and the other southbound traffic. Eachstructure has two box girders, thus there are four504' spans being built concurrently. Prefabricatedconcrete sections, called segments, were cast inthe shape of the box girder.
The main span over the river is being built usingcantilever construction. This construction method
means that the segments are placed in sequencestarting at the main piers until the sides meet inthe middle.
The segments are held together with over athousand miles of high strength steelpost-tensioning strands to provide multiple levelsof redundancy. The steel strands are encased ingrout, pipes and concrete for multiple layers ofprotection.
The main spansegments rangefrom 11' - 25'tall and weighfrom 150 - 200tons each.
Keys (circled inred) cast intoeach segmentare used toalign segmentson the bridge sothey fit togetherproperly.
The segments are picked up with a segment hauler
and loaded onto trailers, which take them to the areanext to the river on the south side.
FIGGProject Hotline612/236-6901 Websitewww.mndot.gov Email Updates [email protected]
9 Key Steps of Mainspan Construction
Step 1 Prefabricate The Concrete Segments.
Step 2 Transport The Segments.
The segments arelifted by BohemianBlue, the largeblue crane, andplaced on bargeswhich then meet upwith Big Ben, thelarge ringer crane.
Step 3 LoadSegments ForConstruction of
The Main Span.
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7/21/2019 Minn i35 Replacement StepByStep
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I-35W St. Anthony Falls Bridge
Big Ben then lifts thesegment into position
in the cantilever.
FIGGProject Hotline612/236-6901 Websitewww.mndot.gov Email [email protected]
Step 4 Liftingthe Segment High strength steel post-
tensioning bars are used toinitially tie the segment to the
previously installed segment.
Step 5
Post-tensioning
bars are installed.
Post-tensioning tendons that areanchored in the completed parts of thebridge are threaded through the newsegment. Each tendon consists of 19high strength steel strands, which inturn consists of seven steel ropes.Multiple tendons create many levels ofredundancy.
Step 6 Post-tensioning Tendons
Segments will be set
on both sides of the
river sequentially, in
all four box girders.
Step 8 Repeatentire process.
After the tendons are threaded throughthe segment, an anchor is positionedon the tendons, then a jack (silver piecof equipment) is used to pull thestrands in each tendon toapproximately a million pounds offorce. Once the proper stress isattained, the wedges in the anchorprevent the strand from losing tension.The jack is removed and an anchorcap is put in its place.
Step 7 Stressing
the tendons.
Main span erection operations will
continue until the box girders
approach each other and meet in
the middle of the span. The final
concrete in the center of the spans
will be cast-in-place, completing
the bridge.
Step 9 Closure joint.
BoxGirder
Segments are squeezed together and locked into place
High StrengthSteel Ropes
Group of strandsform a Tendon
Anchor