Presentation is loading. Please wait.

Presentation is loading. Please wait.

Potential Solutions Goals for Design – What are we concerned about? –Primary Goal: Get the deck on successfully Stability during deck pour Stability during.

Similar presentations


Presentation on theme: "Potential Solutions Goals for Design – What are we concerned about? –Primary Goal: Get the deck on successfully Stability during deck pour Stability during."— Presentation transcript:

1 Potential Solutions Goals for Design – What are we concerned about? –Primary Goal: Get the deck on successfully Stability during deck pour Stability during deck pour Girder plumbness Girder plumbness Deck thickness, cover, smoothness Deck thickness, cover, smoothness –Secondary Goal Design efficiency Design efficiency

2 Potential Solutions- Background: Current Designs

3 Potential Solutions- Background Current Designs On skewed structures, in order to accommodate differential dead load deflections of adjacent stringers that exceed ½ inch at any intermediate crossframe location, the erection bolt holes in the crossframe members should be detailed as slotted holes. Hole dimensions shall be 1/16 wider than the nominal bolt diameter and ¾ longer than the nominal bolt diameter. Holes in the stiffeners shall be 3/16 larger than the diameter of the erection bolts. Final bolting and welding shall not be completed until after the deck concrete has been placed.

4 Potential Solutions- Background: Current Designs

5 Potential Solutions One obvious solution – reduce or eliminate skew Solution 1 – Erect Girders Plumb Solution 1 – Erect Girders Plumb Solution 2 – Erect Girders Out of Plumb (Pre- twist girders) Solution 2 – Erect Girders Out of Plumb (Pre- twist girders) Solution 3 – Stiffen Superstructure Solution 3 – Stiffen Superstructure Solution 4 – Lean-on Bracing Solution 4 – Lean-on Bracing

6 Potential Solutions – Solution 1 Erect Girders Plumb Erect girders plumb Erect girders plumb Install all crossframes (welded) Install all crossframes (welded) Girders rotate out of plumb during deck placement Girders rotate out of plumb during deck placement Girders will be permanently twisted Girders will be permanently twisted Business as Usual Solution

7 Potential Solutions – Solution 1 Erect Girders Plumb Issues How much twist is too much ? How much twist is too much ? –Girders –Bearings –Crossframes

8 Potential Solutions – Solution 2 Erect Girders out of Plumb Erect girders out of plumb (twisted) and girders rotate to plumb during deck placement

9 Potential Solutions – Solution 2 Erect Girders out of Plumb AASHTO/NSBA Guidelines for Constructability

10 AASHTO/NSBA Guidelines for Constructability Method for Erecting Girders Out of Plumb

11 Potential Solutions – Solution 2 Erect Girders out of Plumb Issues –Steel fit-up during erection –Ability of erectors –Where has it been done before ? Is it really feasible? –Steel detailing done correctly ? –Potential finger pointing (detailer, erector, designer, owner)

12 Potential Solutions – Solution 3 Stiffen Superstructure Stiffen superstructure Stiffen superstructure –Add steel Bigger flanges Bigger flanges Deeper webs Deeper webs –Add girder line(s) –Use shored construction Benefit – girder twist reduces with increased girder stiffness Benefit – girder twist reduces with increased girder stiffness

13 Potential Solutions – Solution 3 Stiffen Superstructure Shored Construction Shored Construction Advantage Advantage –Composite for all dead and live loads

14 Potential Solutions – Solution 3 Stiffen Superstructure Disadvantages Disadvantages –Cost of temporary shoring –Need good foundations for shoring –Cant put shoring in traffic –Undesirable to put shoring in waterway –Serious issues with redecking

15 Potential Solutions – Solution 3 Stiffen Superstructure Example 1: Single span, 150 span, 60 deg., 50 ksi Differential Deflection No. of Girders Max. Girder Rotation Total Girder Weight No Restrictions deg. 276 k 1 Max deg. 443 k ½ Max deg. 670 k

16 Potential Solutions – Solution 3 Stiffen Superstructure Example 2: Single span, 166 span, 63 deg. Skew No. of Girders Max. Girder Rotation Total Girder Weight deg. 410 k deg. 750 k

17 Potential Solutions – Solution 4 Lean-on Bracing Lean on Bracing Lean on Bracing What is it ? What is it ?

18 Potential Solutions – Solution 4 Lean-on Bracing

19 Lean-on Cross Frame Bracing for Steel Girders with Skewed Supports

20 Potential Solutions – Solution 4 Lean-on Bracing - Definitions Internal Lean on Bracing (Solution 4I) Internal Lean on Bracing (Solution 4I) External Lean on Bracing (Solution 4E) External Lean on Bracing (Solution 4E)

21 Potential Solutions – Solution 4I Internal Lean-on Bracing X X X X X X A A Section A-A

22 Potential Solutions – Solution 4E External Lean-on Bracing

23 Potential Solutions – Solution 4E External Lean-on Bracing Top & Bottom Angles, Single Bolt at Each End Bolted Crossframe

24 Potential Solutions – Solution 4E External Lean-on Bracing Place Deck – Middle Girders Deflect

25 Potential Solutions – Solution 4E External Lean-on Bracing Install and Weld X-frames Remove Crossframe; Place Deck

26 Potential Solutions – Solution 4E External Lean-on Bracing Install and Weld X-frames

27 Potential Solutions – Solution 4E External Lean-on Bracing Place Closure Pour

28 Miscellaneous Issues Bearings Bearings Deck Joints & End Crossframes Deck Joints & End Crossframes Semi-integral bridges Semi-integral bridges

29 Miscellaneous Issues Bearings Longitudinal slope issues

30 Miscellaneous Issues Bearings Cambered Beam Before Deck Placement

31 Miscellaneous Issues Bearings Beam After Deck Placement

32 Miscellaneous Issues Bearings Before Deck Placement

33 Miscellaneous Issues Bearings After Deck Placement

34 Miscellaneous Issues Bearings

35 Bearing Movement and Restraint Issues

36 Miscellaneous Issues Bearings Longitudinal Displacements Fixed Expansion

37 Miscellaneous Issues Bearings Transverse Displacements

38 Miscellaneous Issues Bearings Lateral restraint issues Fixed Expansion

39 Miscellaneous Issues Bearings Lateral Restraint Semi-integral Retainers

40 Miscellaneous Issues Bearings Lateral Restraint Seismic Pedestals

41 Miscellaneous Issues Bearings - Summary For Skewed / Wide Bridges, May Need to: Design for individual loads Design for individual loads Design for permanent long. & lat. bearing rotations Design for permanent long. & lat. bearing rotations Design for additional longitudinal translation Design for additional longitudinal translation Design for lateral translation Design for lateral translation Prevent or design for lateral restraint forces Prevent or design for lateral restraint forces –Bearing anchors or other restraints –Seismic pedestals –Semi-integral retainers

42 Miscellaneous Issues End Crossframes

43

44

45

46 Miscellaneous Issues Semi-integral Bridges

47

48

49 QUESTIONS ? QUESTIONS ? questions to:


Download ppt "Potential Solutions Goals for Design – What are we concerned about? –Primary Goal: Get the deck on successfully Stability during deck pour Stability during."

Similar presentations


Ads by Google