3 Girders: 84” Hybrids @ 11’-8” Skew = 0° MAH :Spans 117’ , 180’, 262’, 212’, 183’Hybrid A709-50w and HPS-70wWebs 5/8” ThickFlanges from 1-3/8” to 3” thickDeck had multiple transitions on deck.Some bays have top cross frame strutSpans: 5 (963’)Girders: 84” 11’-8”Skew = 0°
4 Frames: Slotted L4”x4”x½” MAH :Spans 117’ , 180’, 262’, 212’, 183’Hybrid A709-50w and HPS-70wWebs 5/8” ThickFlanges from 1-3/8” to 3” thickDeck had multiple transitions on deck.Some bays have top cross frame strutFrames: Slotted L4”x4”x½”3 piece and 4 pieceExpected Deflection during Pour = 10.67”Frame Spacing: 24’
9 Structure was milled ¾” to 1 ¼” MAH :Remedy:Structure was milled ¾” to 1 ¼”Structure was given a 2”-3” microsilica overlayExtra tall overhang brackets were used to dissipate web loading on the adjacent sister structure.Overlay was 2”-3” with a cost 200K
18 FAI :The beam rotation also caused the deck to be thin and the resteel cover to be less than specified.
19 Corrections Performed: FAI :Corrections Performed:Fascia bearings at piers were replaced and beveled shim plates were added to address translational rotation.Loss of cover and deck thickness could have required grinding and overlay.
22 Deck Forming: Hanger Strut Falsework Between the Beams **Between the beams the falsework struts are hung from hangers across the tops of the beam.**The struts do not have to be perpendicular to beams, but they must be consistently spaced**Usually doubled 2x10 lumberFalsework Between the Beams
23 Deck Forming: Edge Forms Soffit Hanger Haunch **Parts of the deck forming seen from the topside.**The soffit is the major decking component which forms the bottom surface of the deck**The haunch forms the depression that embeds the steel beam flange into the deck**Edge forms are are usually steel framed as they often must carry the weight of the deck paving machine.**The hangers seen support the falsework timbers below the soffit.Notice the shear studs that have been welded onto the beam in the background. We will visit more on them later.
24 Stay-in-place forms (SIP): Corrugated, galvanized metalAssume 18 psf for additional concreteSIP forms are often referred to in the field as “pans” or “pan decks”Used for speed, but does not allow inspection of the bottom surface of the deck throughout the life of the deck.18 psf assumes the corrugations are filled with concrete..
25 Stay-in-place forms (SIP): Note orange lines on the skew to help keep the concrete loaded on the deck at the proper skew.Notice galvanized straps across top of beam.
26 Stay-in-place forms (SIP): Clip angleBottom view interior bay
27 Stay-in-place forms (SIP): HaunchStyrofoamStyrofoam has been used to displace the 18 psf of concrete discussed in the previous slide.ODOT has no first hand data on how this practice effects the concrete long term.If the Styrofoam is not adhered properly, it could float up and lay against the reinforcing steel.
29 Traditional formwork and falsework Overhang jacks were bearing approximately 16” above bottom flange. (20%-25% of web depth)
30 Spacing is typically 2’-3’ Typically no haunch No SIP forms Vertical leg length is currently determined by capacity of bracket only.Spacing adjusted to maximize material usage.
31 Standard brackets could not be brought down low due to inspection rail.
32 Overhang brackets can cause localized buckling and rotation of deep girders **Overhang brackets must extend down to a point near the bottom flange. On tall girders, standard overhang brackets only extend partially down the web. When the weight of the concrete pushes down on the overhang bracket it pushes on the web of the girder. If the force is large enough and the web is thin enough localized buckling can occur. Once buckling begins this can cause the beam to rotate. This will affect both structural integrity and rideablility.These localized web deflections can also cause “oil canning” between the cross frames or stiffeners.
33 Std. Max = 50”Deep Max = 70”C-49 is the standard size overhang bracketC-49D is the Deep overhang bracket.
36 Rail Rotating Rollers Augers Vibrating Rollers **The most common bridge paving machines are manufactured by Bidwell and Gomaco**Specification has specific requirements for the bridge paving machine some of which are:**Must have precise control of movement forwards and backwards**Two rotating rollers to smooth and finish the concrete**Leveling augers to get concrete to approximate elevation**Vibrating roller or vibrating pan with a frequency of between 1500 and 5000 impulses per minute**The machine must be able to finish transversely, in both directions, for the full width of the deck between curbs or parapets.**It must run on temporary steel railsRotatingRollersAugersVibratingRollers
37 Bid-Well 3600 Max. Paving Width = 96’ Basic Machine = 5990 lbs. 3600 indicates 36” square trussExtension inserts available in 18 ft. (5.5m), 15 ft. (4.6m),12 ft. (3.7m), 6 ft. (1.8m), 4 ft. (1.22m) and 3 ft. (0.9m) lengthsMax. Paving Width = 96’Basic Machine = 5990 lbs.Additional = 53 lbs. / ft.
38 Bid-Well 3600 Wheel Base = 3’ 8’-7” 3600 indicates 36” square truss Extension inserts available in 18 ft. (5.5m), 15 ft. (4.6m),12 ft. (3.7m), 6 ft. (1.8m), 4 ft. (1.22m) and 3 ft. (0.9m) lengthsWheel Base = 3’
39 Bid-Well 4800 Max. Paving Width = 120’ Basic Machine = 7600 lbs. 4800 indicates 48” square trussExtension inserts available in 18 ft. (5.5m), 15 ft. (4.6m),12 ft. (3.7m), 8 ft. (2.4m), 6 ft. (1.8m), 4 ft. (1.22m), 3 ft. (0.9m) and 2 ft. (.61m) lengthsMax. Paving Width = 120’Basic Machine = 7600 lbs.Additional = 75 lbs. / ft.
40 Bid-Well 4800 Wheel Base = 4’ 11’-7” 4800 indicates 48” square truss Extension inserts available in 18 ft. (5.5m), 15 ft. (4.6m),12 ft. (3.7m), 8 ft. (2.4m), 6 ft. (1.8m), 4 ft. (1.22m), 3 ft. (0.9m) and 2 ft. (.61m) lengths
41 Bid-Well 4800 w/ 66” Deep Truss 4800 indicates 48” square truss “ toDeep Truss Transitions are 15’ long and go from 48” to 66”Deep Truss 66” sections are 90 lbs/ftShould use 80’-90’ of 48” truss maximum.OCA- Office of Construction AdministrationMax. Paving Width = 160’Specialty Item – Do Not Use without Consulting OCA
42 Deck Placement: Contractor Typical Method of Placement This causes large amounts of differential deflection between the girders as they are carrying a different portion of the total girders intended load.
43 Deck Placement: Design Assumes Loading Along the Skew - OR - This keeps the differential deflection between the beams to a minimum.It takes specialized attachments to the bridge paving machine to finish a deck on a skew.
45 Deck Placement Going Forward: Load and finish along skew (±5°) up to 50°.Above 50°, finish at 50° and load at actual skew (±5°), but limit leading edge of concrete to 20’ ahead of bridge paving machine.The skew kit on the Bidwell paving machine goes from 15° to 55° in 5° increments.Mention rollers should be parallel to center line.
46 Calculating Bid-Well Machine Length: SkewWidth+ Extra┴151.04 x w5’-0”201.06 x w5’-6”251.10 x w6’-6”301.15 x w7’-0”351.22 x w8’-0”401.31 x w9’-0”451.41 x w10’-6”501.56 x w11’-6”Skew is finishing skew┴Width is the rail to rail dimension perpendicular to centerline.+Extra is the additional truss necessary to get legs onto rail in skewed position.Machine Length = Width + Extra Length┴
56 Setting Grade:Contractor receives a table of screed elevations at quarter points of each span.Deviations in the camber of the beams is normally corrected by varying the haunch height**Setting the grade for a bridge deck is discussed in the CIM in section 511 on page 604Haunch
57 Theoretical Bottom of Deck Setting Grade:The haunch height is determined by subtracting the elevation of the top of the beams from the theoretical bottom of the deckThe theoretical bottom of the deck is determined by subtracting the thickness of the deck from the given screed rail elevations**Setting the grade for a bridge deck is discussed in the CIM in section 511 on page 604Screed ElevationDeck ThicknessTop of BeamTheoretical Bottom of Deck
58 Setting Grade: Example of a haunch height or “fill” table 966.64 966.48966.32966.16966.00965.89965.73965.57965.41965.25965.22965.07964.93964.75964.580.660.640.67Assuming 9” thick deck:**First calculate the Deck Bottom elevation by subtracting the deck thickness of .75 from the Screed elevation.**For the first column that would be – 0.75 =**Next by taking actual shots on the beams get the elevation at the abutment and all ¼ points along the span and fill them in the row marked “Beam Top”**Now calculate the haunch height by subtracting the Beam Top elevation from the Deck Bottom elevation.**For the first column that would be – = (which is equal to 8”)
59 Setting Grade: Grade must be set by instrument Rails Cups or Saddles Cups and Saddles are threaded and adjustable.Rails are comprised of 2” hollow round or square stock.Cup spacing usually ranges from 2’-4’. Must allow zero deflection due to machine and operator weight.If the spans are short enough Contractor’s will string between quarter points to set rails. For larger spans, the Contractor will calculate intermediate screed elevations and shoot them in and then string between them.RailsCups or Saddles
60 Dry RunCheck deck thickness and concrete cover over reinforcing steel **Make sure bridge paving rails are secure with no deflection**The dry run is where the contractor runs the bridge paving machine through the entire pour sequence to make sure that everything is ready for the actual pour.**NOTE that significant differential camber between the fascia beams and interior beams will cause the steel to appear low during the dry run.Make sure bridge paving machine is functioning properly
61 Dry RunContractor can only make adjustments for deflections due to the finishing machine weight (not the concrete dead load)Contractor assumes deflections due to concrete dead loads have been addressed in the screed elevations provided