2018 LOUISIANA TRANSPORTATION CONFERENCE. Mohsen Shahawy, PHD, PE

Transcription

1 2018 LOUISIANA TRANSPORTATION CONFERENCE Sunday, February 25 - Wednesday, February 28, 2018 DEVELOPMENT OF U-BEAM PRESTRESSED CONCRETE DESIGN STANDARDS Mohsen Shahawy, PHD, PE SDR Engineering Consultants, Inc. SDREngineering.com Engineering Consultants, Inc.

2 LOUISIANA U-GIRDER DEVELOPMENT PHASE I: Task 1: General: Design, Detailing LU Girders Task 2: Distribution Factors for LU Girders Larger than 65 in. PHASE II: Task 3: Design Aids LU Girders Task 4: Design Aids Bearing Task 5: Development Of Lu Girder Standards And Special Details

3 PHASE I: OBJECTIVE Evaluation of the current practice in other states to determine the most appropriate shape for the LU-girders. Development of Live Load Distribution Factors for LU-girders with depths exceeding 65 in.

4 WORK PLAN PROPOSED LU-GIRDER SECTIONS LU-72 LU-78

5 WORK PLAN PROPOSED LU-GIRDER SECTIONS LU-84

6 WORK PLAN FRAMING PLANS Bridge consists of three (3) LU-girders Three girder sections LU-72, LU-78 and LU-84

7 SENSITIVITY STUDY MODELING TECHNIQUES 1- Grillage Model (Transverse element for deck) 2- Planar Model (Plate element for deck)

8 SENSITIVITY STUDY MODELING TECHNIQUES 3- Shell Model (Plate element for deck and girders)

9 SENSITIVITY STUDY Comparison of Modeling Techniques Girder Feature Grillage Planar Shell Exterior Moment (kip ft.) Interior Moment (kip ft.)

10 SENSITIVITY STUDY Findings Grillage models yields results as accurate as the sophisticated 3-D shell model. Planar models yields results as accurate as the sophisticated 3-D shell model. Conclusion Planar models with ~2.5 ft. longitudinal elements will be used in the parametric study.

11 WORK PLAN PARAMETERS Span Length (4 Variations) 100 ft., 110 ft., 120 ft. and 130 ft. for LU-72 girder 105 ft., 115 ft., 125 ft. and 135 ft. for LU-78 girder 110 ft., 120 ft., 130 ft. and 140 ft. for LU-84 girder Girder Spacing (4 Variations) 12 ft., 14 ft., 16 ft. and 18 ft. Overhang Width (2 Variations) 5 ft. and 7 ft. Girder Stiffness (3 Variations) LU-72 LU-78 LU-84 Total No. of FE Models = 4 x 4 x 2 x3 = 96

12 WORK PLAN CASES OF LOADING FOR EXTERIOR GIRDER Case 1: One (1) Design Lane Loaded Multi-Lane Presence Factor included Ext. Girder

13 WORK PLAN CASES OF LOADING FOR EXTERIOR GIRDER Case 2: Two (2) Design Lanes Loaded Multi-Lane Presence Factor included Ext. Girder

14 WORK PLAN CASES OF LOADING FOR INTERIOR GIRDER Case 1: One (1) Design Lane Loaded Multi-Lane Presence Factor included Int. Girder

15 WORK PLAN CASES OF LOADING FOR INTERIOR GIRDER Case 2: Three (3) Design Lanes Loaded Multi-Lane Presence Factor included Int. Girder

16 WORK PLAN MOMENT DISTRIBUTION FACTORS Service Live Load Moment from FE (M FE ) LANES 1+2 Exterior Girder LANES 1+2+3

17 WORK PLAN MOMENT DISTRIBUTION FACTORS W lane = 0.64 kip/ft 32 k 32 k 8 k Impact factor included Magnification factor for LADV11 included Lane Moment for LADV11 using Influence Line (M LANE )

18 WORK PLAN MOMENT DISTRIBUTION FACTORS Moment Distribution Factors were determined as follows: DF (one lane loaded) = M FE (1 lane) M LANE DF (two or more lanes loaded) = M FE (2 or 3 lanes) M LANE

19 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS EFFECT OF SPAN LENGTH LU-72 Bridges FT 120 FT 110 FT 100 FT FT 120 FT 110 FT 100 FT Exterior Girder

20 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS EFFECT OF SPAN LENGTH LU-78 Bridges FT 125 FT 115 FT 105 FT FT 125 FT 115 FT 105 FT Exterior Girder

21 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS EFFECT OF SPAN LENGTH LU-84 Bridges FT 130 FT 120 FT 110 FT FT 130 FT 120 FT 110 FT Exterior Girder

22 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS EFFECT OF GIRDER SPACING LU-72 Bridges Span (ft.) S 18 FT. S 16 FT. S 14 FT. S 12 FT SAME BEHAVIOR OBSERVED FOR LU-78 AND LU-84 BRIDGES Span (ft.) Exterior Girder S 18 FT. S 16 FT. S 14 FT. S 12 FT.

23 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS EFFECT OF GIRDER STIFFNESS 1.30 Girder spacing = 18 ft. 72 IN. DEPTH 78 IN. DEPTH 84 IN. DEPTH IN. DEPTH 78 IN. DEPTH 84 IN. DEPTH SAME BEHAVIOR OBSERVED FOR GIRDER SPACINGS 12, 14 AND 16 FT Span (ft.) Span (ft.) Exterior Girder

24 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS EFFECT OF OVERHANG WIDTH LU-72 Bridges ft. Span OV 5 FT OV 6 FT OV 7 FT. OV 8 FT. OV 9 FT ft. Span OV 5 FT OV 6 FT OV 7 FT. OV 8 FT. OV 9 FT Exterior Girder

25 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE LU-72 Bridges ONE LANE LOADED 130 ft. Span AASHTO ft. ft. Span AASHTO 1 LANE LOADED LANE LOADED Exterior Girder

26 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE LU-78 Bridges ONE LANE LOADED 135 ft. Span 1 LANE LOADED AASHTO ft. Span 1 LANE LOADED AASHTO Exterior Girder

27 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE LU-84 Bridges ONE LANE LOADED 140 ft. Span 1 LANE LOADED AASHTO ft. Span 1 LANE LOADED 140 ft. Span AASHTO Exterior Girder

28 MOMENT DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE Observations For one design loaded lane, AASHTO formulas are unconservative in their prediction for the moment distribution factors for interior LU-girders with depths higher than 65 in. For one design loaded lane, the lever rule provide overly conservative prediction for the moment distribution factor for the exterior LU-girders with depths higher than 65 in. New formulas are proposed to determine the moment distribution factors for interior and exterior LU-girders

29 MOMENT DISTRIBUTION FACTORS PROPOSED FORMULAS (One Loaded Lane) AASHTO FORMULA PROPOSED FORMULA S 0.35 Sd 0.25 S 0.30 Sd L L 2 Exterior Girder (One Loaded Lane) AASHTO FORMULA PROPOSED FORMULA Lever Rule ( d e /16.0) S Sd 8.3 L S Girder spacing L Span length d e : Distance from the centerline of the exterior web of exterior beam at the deck level to the interior edge of the barrier d Girder depth

30 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS PROPOSED FORMULAS Proposed Formula / FE Results (One Loaded Lane) ft. Span 72 in. Depth PROPOSED ft. Span 72 in. Depth PROPOSED LANE LOADED LANE LOADED Exterior Girder

31 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE LU-72 Bridges TWO OR MORE LOADED LANES ft. Span 130 ft. Span AASHTO AASHTO 2 OR MORE LANES LOADED 2 LANES LOADED Exterior Girder

32 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE LU-78 Bridges TWO OR MORE LOADED LANES ft. Span AASHTO ft. Span AASHTO 2 OR MORE LANES LOADED 2 LANES LOADED Exterior Girder

33 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE LU-84 Bridges TWO OR MORE LOADED LANES ft. Span AASHTO ft. Span 140 ft. Span AASHTO 2 OR MORE LANES LOADED 2 LANES LOADED Exterior Girder

34 MOMENT DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE Observations For the case of two or more loaded lanes, AASHTO formulas are unconservative in their prediction for the moment distribution factors for interior and exterior LU-girders with depths higher than 65 in. New formulas are proposed to determine the moment distribution factors for interior and exterior LU-girders with depths higher than 65 in.

35 MOMENT DISTRIBUTION FACTORS PROPOSED FORMULAS (Two or More Loaded Lanes) AASHTO FORMULA PROPOSED FORMULA S 6.3 Sd 12L S Sd 12 L Exterior Girder (Two or More Loaded Lanes) AASHTO FORMULA PROPOSED FORMULA ( d e /28.5) S 6.3 Sd 12L ( d e /16.0) S Sd 12 L S Girder spacing L Span length d e : Distance from the centerline of the exterior web of exterior beam at the deck level to the interior edge of the barrier d Girder depth

36 Distribution Factor Distribution Factor MOMENT DISTRIBUTION FACTORS PROPOSED FORMULAS Proposed Formula / FE Results (Two or More Loaded Lanes) ft. Span 72 in. Depth PROPOSED ft. Span 72 in. Depth PROPOSED OR MORE LANES LOADED OR MORE LANES LOADED Exterior Girder

37 SHEAR DISTRIBUTION FACTORS Service Live Load Shear was determined from FE (V FE ) Lane Moment for LADV11 determined using Influence Line (V LANE ) DF (one lane loaded) = V FE (1 loaded lane) M LANE DF (two or more lanes loaded) = V FE (2 or more lanes) M LANE

38 Distribution Factor Distribution Factor SHEAR DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE LU-72 Bridges ONE LANE LOADED ft. Span ft. ft. Span AASHTO 0.40 AASHTO LANE LOADED LANE LEVER RULE Exterior Girder

39 SHEAR DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE Observations For one loaded lane, AASHTO formulas are very conservative in their prediction for the shear distribution factors for interior and exterior LU-girders with depths higher than 65 in. New formulas are proposed to accurately predict the shear distribution factors for U-girders.

40 SHEAR DISTRIBUTION FACTORS PROPOSED FORMULAS (One Loaded Lane) AASHTO FORMULA S d 12 L 0.1 PROPOSED FORMULA No Change Exterior Girder (One Loaded Lane) AASHTO FORMULA Lever Rule ( d e /16) PROPOSED FORMULA S d 12 L 0.1 S Girder spacing L Span length d Girder depth d e : Distance from the centerline of the exterior web of exterior beam at the deck level to the interior edge of the barrier

41 Distribution Factor Distribution Factor SHEAR DISTRIBUTION FACTORS PROPOSED FORMULAS Proposed Formula / FE Results (One Lane Loaded) ft. span 72 in. depth Interior girder RPOPOSED ft. span 72 in. depth Exterior girder PROPOSED LANE LOADED LANE LOADED Exterior Girder

42 Distribution Factor Distribution Factor SHEAR DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE LU-72 Bridges TWO OR MORE LOADED LANES ft. Span AASHTO ft. Span ft. Span AASHTO 2 OR MORE LANES LOADED 2 LANES LOADED Exterior Girder

43 Distribution Factor Distribution Factor SHEAR DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE LU-78 Bridges TWO OR MORE LOADED LANES ft. Span 135 ft. Span AASHTO AASHTO 2 OR MORE LANES LOADED 2 LANES LOADED Exterior Girder

44 Distribution Factor Distribution Factor SHEAR DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE LU-84 Bridges TWO OR MORE LOADED LANES ft. Span 140 ft. Span AASHTO 140 ft. Span AASHTO 2 OR MORE LANES LOADED 2 LANES LOADED Exterior Girder

45 SHEAR DISTRIBUTION FACTORS COMPARISON WITH AASHTO LRFD CURRENT PRACTICE Observations For two or more loaded lanes, AASHTO formulas are very conservative in their prediction for the shear distribution factors for interior and exterior LU-girders with depths higher than 65 in. New formulas are proposed to accurately predict the shear distribution factors for U-girders.

46 SHEAR DISTRIBUTION FACTORS PROPOSED FORMULAS (Two or More Loaded Lanes) AASHTO FORMULA S d 12 L 0.10 PROPOSED FORMULA S d 12 L Exterior Girder (Two or More Loaded Lanes) AASHTO FORMULA ( + d e /10) S d 12 L 0.10 ( d e /14) PROPOSED FORMULA S d 12 L S Girder spacing L Span length d Girder depth d e : Distance from the centerline of the exterior web of exterior beam at the deck level to the interior edge of the barrier

47 Distribution Factor Distribution Factor SHEAR DISTRIBUTION FACTORS PROPOSED FORMULAS Proposed Formula / FE Results (Two or More Lanes Loaded) ft. span 72 in. depth Interior girder PROPOSED ft. span 72 in. depth Exterior girder PROPOSED OR MORE LANES LOADED OR MORE LANES LOADED Exterior Girder

48 CONCLUSIONS SUMMARY OF OBSERVATIONS AASHTO formulas were found to be unconservative or very conservative in their prediction for the moment and shear distribution factors for interior and exterior LU-girders with depths higher than 65 in. New formulas are proposed to accurately predict the moment and shear distribution factors for interior and exterior LUgirders.

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