CONCRETE SPLICED GIRDERS IN TEXAS Nicholas Nemec, P.E. TxDOT-BRG October 15, 2014
What is a Concrete Spliced Girder? 2
What is a Concrete Spliced Girder? What it is NOT : Continuous For Live Load 3
What is a Concrete Spliced Girder? Hybrid of 2 existing structure types Prestressed Beam Span Lengths 50 to 150 Segmental Span Lengths > 300 4
Similarities to Prestressed Beam Precast Sections Prestressed (strands or tendons) Similar shapes Similar deck construction (PCP and CIP top) 5
Differences to Prestressed Beam Post Tensioning Tendons in the web Continuous over multiple spans Both flanges (top and bottom) experience tension and compression 6
Similarities to Segmental Precast Sections Continuity Tendons Continuous over multiple spans 7
Differences to Segmental Longer Precast Sections Fewer Precast Sections Includes multiple girder lines (structural redundancy) Replaceable deck 8
What is a Concrete Spliced Girder? 2 or more precast concrete beam sections Cast in place splices Post tensioned with full length continuity tendons Final Condition Fully Continuous Concrete Girder 9
What is a Concrete Spliced Girder? 10
What is a Concrete Spliced Girder? Precast Sections 11
What is a Concrete Spliced Girder? Precast Sections Cast in Place Splices 12
What is a Concrete Spliced Girder? Precast Sections Cast in Place Splices Continuity Tendons 13
APPLICABILITY AND ADVANTAGES: Provide an option for spans in the 150 to 300 range Provide an alternative to steel Straight or horizontally curved alignments Fast Uses (combines) current construction techniques 14
TYPICAL SECTIONS: 15
TYPICAL SECTIONS: I-Section U-Section 16
I-SECTION: Uses Max Span (Main Span) Length 300 to 325 (Haunched) 300 to 325 17
I-SECTION: Uses Max Span (Main Span) Length 300 to 325 (Haunched) 300 to 325 Max Span(Main Span) Length 225 to 275 (Constant Depth) 225 to 275 18
I-SECTION: Uses Horizontally Straight Alignments 19
I-SECTION: Uses Horizontally Straight Alignments Skewed or Normal Bents Limit skew angle if possible. Same issues with skew as with any other superstructure type 20
I-SECTION: Uses Horizontally Straight Alignments Skewed or Normal Bents Limit skew angle if possible. Same issues with skew as with any other superstructure type Phased Construction 21
I-SECTION: Uses Horizontally Straight Alignments Skewed or Normal Bents Limit skew angle if possible. Same issues with skew as with any other superstructure type Phased Construction Useful on projects that do not allow for shore towers in the main span 22
I-SECTION: Construction Process Step 1: Set Back Span Sections 23
I-SECTION: Construction Process Step 1: Set Back Span Sections Step 2: Set Pier Sections 24
I-SECTION: Construction Process Step 1: Set Back Span Sections Step 2: Set Pier Sections Step 3: Cast Anchorage Blocks, Splices, and Diaphragms. 25
I-SECTION: Construction Process Step 1: Set Back Span Sections Step 2: Set Pier Sections Step 3: Cast Anchorage Blocks, Splices, and Diaphragms. Step 4: Set Drop In Span Section 26
I-SECTION: Drop In Span Section 27
I-SECTION: Drop In Span Section Strong Back Advantage: Simple Disadvantage: Additional Weight fhwa.gov 28
I-SECTION: Drop In Span Section Hanger System Advantage: No Additional Weight Disadvantage: Complicates Details, Larger Moment Arm fhwa.gov 29
I-SECTION: Drop In Span Section From a DESIGN STANDPOINT Preference is to specify a Strong Back fhwa.gov 30
I-SECTION: Drop In Span Section From a DESIGN STANDPOINT Preference is to specify a Strong Back Allow contractor to develop details to incorporate a hanger system if he/she chooses. fhwa.gov 31
I-SECTION: Construction Process Step 1: Set Back Span Sections Step 2: Set Pier Sections Step 3: Cast Anchorage Blocks, Splices, and Diaphragms. Step 4: Set Drop In Span Section 32
I-SECTION: Construction Process Step 1: Set Back Span Sections Step 2: Set Pier Sections Step 3: Cast Anchorage Blocks, Splices, and Diaphragms. Step 4: Set Drop In Span Section Step 5: Cast 2 nd Splices and Stress Continuity Tendons 33
I-SECTION: Construction Process Step 1: Set Back Span Sections Step 2: Set Pier Sections Step 3: Cast Anchorage Blocks, Splices, and Diaphragms. Step 4: Set Drop In Span Section Step 5: Cast 2 nd Splices and Stress Continuity Tendons Step 6: Place Precast Concrete Panels (PCP) and Cast Deck 34
Place PCP s across entire I-SECTION: Construction Process unit prior to casting deck. Step 1: Set Back Span Sections Helps to reduce deck stresses due to staged Step 2: Set Pier Sections pouring. Step 3: Cast Anchorage Blocks, Splices, and Diaphragms. Step 4: Set Drop In Span Section Step 5: Cast 2 nd Splices and Stress Continuity Tendons Step 6: Place Precast Concrete Panels (PCP) and Cast Deck 35
I-SECTION (Constant Depth) 36
10 Web I-SECTION (Constant Depth) 37
10 Web I-SECTION (Constant Depth) 4 Top Flange (Depth) 38
I-SECTION (Constant Depth) 10 Web 4 Top Flange (Depth) 60 Top Flange (Width) 39
I-SECTION (Constant Depth) 10 Web 4 Top Flange (Depth) 60 Top Flange (Width) 40 Bottom Flange (Width) 40
I-SECTION (Constant Depth) 10 Web 4 Top Flange (Depth) 60 Top Flange (Width) 40 Bottom Flange (Width) 80 Pretensioning Strands Available Debond as needed 41
I-SECTION (Constant Depth) 10 Web 4 Top Flange (Depth) 60 Top Flange (Width) 40 Bottom Flange (Width) 80 Pretensioning Strands Available Debond as needed 4 Continuity Ducts 19 ~ 0.6 Strand Tendons 42
I-SECTION (Constant Depth) 10 Web 4 Top Flange (Depth) 60 Top Flange (Width) 40 Bottom Flange (Width) 80 Pretensioning Strands Available Debond as needed 4 Continuity Ducts 19 ~ 0.6 Strand Tendons Depth Varies 7 Ft, 8 Ft, 9 Ft 43
I-SECTION (Constant Depth) Section weight between 1,500 lbs/ft 1,850 lbs/ft Segment Length = 140 Segment weight 105 Tons - 130 Tons 44
I-SECTION (Constant Depth) Section weight between 1,500 lbs/ft 1,850 lbs/ft Segment Length = 140 Segment weight 105 Tons - 130 Tons Max Span Length is the result of the shipping, lifting, shore tower availability, site conditions. 45
I-SECTION (Haunched) Dimensions are same as Constant Depth 46
I-SECTION (Haunched) Dimensions are same as Constant Depth Overall Height varies linearly Max height is 16 47
I-SECTION (Haunched) Dimensions are same as Constant Depth Overall Height varies linearly Max height is 16 Bottom Flange Thickness varies 48
I-SECTION (Haunched) Dimensions are same as Constant Depth Overall Height varies linearly Max height is 16 Bottom Flange Thickness varies Max Segment Length is 90 to 120 (weight governs) 49
I-SECTION (Splice) 50
I-SECTION (Splice) Uniform Cross Section fhwa.gov 51
I-SECTION (Splice) Uniform Cross Section Disadvantages: More detailed form work fhwa.gov 52
I-SECTION (Splice) Uniform Cross Section Disadvantages: More detailed form work Small tolerance for duct misalignment fhwa.gov 53
I-SECTION (Splice) Uniform Cross Section Disadvantages: More detailed form work Small tolerance for duct misalignment Less clearance for plastic duct couplers fhwa.gov 54
I-SECTION (Splice) Uniform Cross Section Disadvantages: More detailed form work Small tolerance for duct misalignment Less clearance for plastic duct couplers Potential for poor consolidation in bottom flange fhwa.gov 55
I-SECTION (Splice) Uniform Cross Section Disadvantages: More detailed form work Small tolerance for duct misalignment Less clearance for plastic duct couplers Potential for poor consolidation in bottom flange Using a stinger is difficult, could easily damage ducts fhwa.gov 56
I-SECTION (Splice) Uniform Cross Section Advantages : fhwa.gov 57
I-SECTION (Splice) Uniform Cross Section Advantages : Smooth appearance fhwa.gov 58
I-SECTION (Splice) Tapered Web Width PLAN ELEVATION 59
I-SECTION (Splice) Tapered Web Width Advantages: Simple form work More room for alignment errors Stinger can be used (with care) More room for plastic couplers PLAN ELEVATION 60
I-SECTION (Splice) Tapered Web Width Advantages: Simple form work More room for alignment errors Stinger can be used (with care) More room for plastic couplers Higher probability of a quality splice PLAN ELEVATION 61
I-SECTION (Splice) Tapered Web Width Disadvantages: Increased lifting weight on precast section More detailed forming in the precast yard PLAN ELEVATION 62
I-SECTION (Splice) Tapered Web Width Disadvantages: Increased lifting weight on precast section More detailed forming in the precast yard Produces a visible knuckle 63
U-SECTION: Uses Max Span (Main Span) Length 265 to 280 265 to 280 64
U-SECTION: Uses Max Span (Main Span) Length 265 to 280 265 to 280 Can be used on Horizontally Curved Alignments 65
U-SECTION: Uses Max Span (Main Span) Length 265 to 280 265 to 280 Can be used on Horizontally Curved Alignments Larger girder spacing (>20 ) resulting in fewer girder lines 66
U-SECTION: Uses Max Span (Main Span) Length 265 to 280 265 to 280 Can be used on Horizontally Curved Alignments Larger girder spacing (>20 ) resulting in fewer girder lines Require (typically) shore towers in the main span 67
U-SECTION: Uses Max Span (Main Span) Length 265 to 280 265 to 280 Can be used on Horizontally Curved Alignments Larger girder spacing (>20 ) resulting in fewer girder lines Require (typically) shore towers in the main span May require additional construction steps, compared to I-Section 68
U-SECTION: Construction Process Potential Additional Steps 69
U-SECTION: Construction Process Potential Additional Steps Additional Post Tensioning Stages Splices located away from inflection points (due to shorter precast lengths) Additional Bottom Tendons Constant section depth, requires post tensioning above piers Additional Top Tendons 70
U-SECTION: Construction Process Potential Additional Steps Cast a Lid Slab prior to stressing Continuity Tendons Required when used on horizontal alignment Creates a closed box, which can handle the torsion induced by the curvature 71
U-SECTION: Construction Process Potential Additional Steps Requires an Internal Diaphragm Diaphragm is constructed with an access hole for future (potentially) internal inspections 72
U-SECTION (Typical) 73
10 Web U-SECTION (Typical) 74
10 Web U-SECTION (Typical) 8 Continuity Tendons 75
U-SECTION (Typical) 10 Web 8 Continuity Tendons Bottom Tendons (could be pretension strands) 76
U-SECTION (Typical) 10 Web 8 Continuity Tendons Bottom Tendons (could be pretension strands) 6, 7 and 8 depths 77
U-SECTION (Typical) Section weight between 2,100 lbs/ft 2,800 lbs/ft Segment Length = 90 Segment weight 95 Tons - 130 Tons 78
U-SECTION (Splice) 79
U-SECTION (Splice) Increased Web Width 80
U-SECTION (Splice) Increased Web Width Increased Bottom Flange Thickness 81
U-SECTION (Splice) Increased Web Width Increased Bottom Flange Thickness Continuous Top Flange 82
U-SECTION (Splice) Increased Web Width Increased Bottom Flange Thickness Continuous Top Flange Shear Keys in Webs 83
RESEARCH 0-6651, Continuous Prestressed Concrete Girder Bridges, TTI 0-6652, Spliced Texas Girder Bridges, CTR 84
RESEARCH 0-6651, Continuous Prestressed Concrete Girder Bridges, TTI Synthesis study of industry practice, casting, transportation and construction Analysis of the modified Tx70 and U54 girders for a range of main span lengths Practical limits for the girders Failure mechanisms for splices at various moment/shear combinations 85
RESEARCH 0-6652, Spliced Texas Girder Bridges, CTR Comparison of steel vs plastic duct on shear capacity Shear capacity of the cast in place splice with the presence of the plastic couplers 86
ENGINEERING SOFTWARE Stage construction, removal/addition of supports, composite properties, pretensioning/post tensioning modeling, time dependent effects (ADAPT, RMBRIDGE, MIDAS, etc) 87
Nicholas Nemec, P.E. TxDOT--Bridge Division Nicholas.Nemec@txdot.gov 512-416-2280 Copyright 2014 Texas Department of Transportation All Rights Reserved Entities or individuals that copy and present state agency information must identify the source of the content, including the date the content was copied. Entities or individuals that copy and present state agency information on their websites must accompany that information with a statement that neither the entity or individual nor the information, as it is presented on its website, is endorsed by the State of Texas or any state agency. To protect the intellectual property of state agencies, copied information must reflect the copyright, trademark, service mark, or other intellectual property rights of the state agency whose protected information is being used by the entity or individual. Entities or individuals may not copy, reproduce, distribute, publish, or transmit, in any way this content for commercial purposes. This presentation is distributed without profit and is being made available solely for educational purposes. The use of any copyrighted material included in this presentation is intended to be a fair use of such material as provided for in Title 17 U.S.C. Section 107 of the US Copyright Law. 88