Copyright 2015 American Institute of Steel Construction. All rights reserved.

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1 Notice: Copyright 2015 American Institute of Steel Construction. All rights reserved. This presentation is provided solely for informational purposes and does not constitute conveyance of any intellectual property rights. This presentation may not be reproduced or redistributed, in whole or in part, without the prior consent of the American Institute of Construction or the National Steel Bridge Alliance. Steel Bridge Design and Fabrication Material and Constructability Consideration Christopher Garrell, PE, LEED AP NSBA - Southeast Regional Director garrell@steelbridges.org 2 Steel: The Bridge Material of Choice A division of the American Institute of Steel Construction 1

2 Material Availability and Guidelines Structural Shapes and Plate 3 Structural Shape Availability Steel Dynamics Butler Nucor-Yamato Steel Blytheville Gerdau Ameristeel Petersburg Gerdau Ameristeel Beaumont 4 2

3 Structural Shape Availability ASTM A992; ASTM A709, Grade 50S Minimum Yield = 50 ksi. No HPS Maximums Producer ** Nucor-Yamato Steel Gerdau Ameristeel Maximum Depth (in) Steel Dynamics 36 * Maximum length for some beam sizes may be shorter. Length (ft) 120 * ** These mills account for over 90% of all wide flange shapes produced in the United States. 5 Structural Shape Availability Rolled beam generally more economical. Except with hard curve or camber. Availability dependent on rolling schedules. Allow plate girder alternate (show on bid documents)

4 Mill Plate Availability 7 Mill Plate Availability Grade 50 Plate Availability Maximums Producer Maximum Thickness (in) Maximum Width (in) Arcelor-Mittal Nucor Steel SSAB * Approximately 700,000 tons of plate used annually for construction projects in the United States

5 Mill Plate Availability Rationalize all mill plate tables Arcelor- Mittal Availability Intersection Nucor SSAB 9 Mill Plate Availability Grade 50 Composite Mill Plate Tables * A and A709-50W (Non-FC) Availability only. ** Refer to September 2011 issue of Modern Steel Construction Magazine

6 Mill Plate Availability Grade 50 Thickness Increments 1/8 for plate up to 2½ thick. 1/4 for plate over 2½ thick. Cost increases with thickness. Width Preferences Fabricators prefer 72 and 96 widths. Cost increases with width Material Availability and Guidelines High Performance Steel (HPS)

7 Mill Plate Availability HPS70W Plate Availability Maximums Producer Arcelor-Mittal (Q&T) Arcelor-Mittal (TMCP) Nucor Steel (TMCP) Maximum Thickness (in) Maximum Width (in) Maximum Length (in) / SSAB (TMCP) * Q&T: Quench and Tempered. ** TMCP: Thermomechanical Controlled Process Hybrid and Mixed Design Mixed Design: Homogeneous material grades within each field piece, but may vary the material strength between field pieces. Hybrid Designs: Mix steel grades within design sections

8 Hybrid and Mixed Design Research has shown that hybrid girder designs allowed economical incorporation of HPS 70W. Optimum hybrid section used HPS 70W material in all the bottom flanges and in the top flanges of negative moment regions. All girder webs and positive moment region top flange plates will use Grade 50 steel. May not be cost effective if bottom flange plate in positive moment regions is governed by fatigue in lieu of strength. Generally, hybrid design can be optimized at a shallower depth than can Grade 50 girders. Source: Steel Bridge Design Handbook Bridges: Making the Right Choices Material Availability and Guidelines Usable Plate Area

9 Raw Material and Layout 17 Edge and Weld Preparation

10 Usable Mill Plate Area Flange Plate Web Plate (Haunched) 19 Usable Mill Plate Area Web Plate Width: 1 4 Length: 1 6 Material loss will increase if web is haunched or cambered. Flange Plate Width: 1 4 total plus an additional 1/4" per burn. Length: 1-6 A fabricator may choose to increase flange widths specified by the Engineer from 1/4" - 3/8". Can vary between fabricators

11 Usable Mill Plate Area Horizontally Curved Girders Heat Curving Cut Curving Heat Curving (Allowed) Flange thickness less than 3 in. Flange widths less than 30 in. Radius of curvature greater than 150ft. Additional evaluation of equations in LRFD Construction Specification (new 7 th Edition Specification) More Information Plate Availability for Highway Bridges September 2011 Modern Steel Construction Magazine. Modern Steel Construction Magazine

12 A Starting Point Plate Girder Design Best Practices 23 Design References

13 Span Layout Traditionally, single multi-span unit preferred over many simple spans or several continuousspan units Eliminating end spans and associated joints provides savings in Bearings Cross-frames Expansion devices 25 Span Layout Simple Span Construction with Link Slabs May not need bolted field splices. Uses less additional deck reinforcement. May be less expensive to erect. Valuable tool for accelerated bridge construction projects

14 Span Layout Optimal Span Length = ft. Estimated Cost ($/ft) Total Cost Curve Span Length (ft) Span Layout Layout spans so that maximum positive moments are nearly equal in each span. End spans ideally 75% - 82% of center span. 0.75L To 0.82L L 0.75L To 0.82L Balanced Span Arrangement

15 Girder Spacing & Deck Overhangs Goal economical cross-section Balance spacing & overhang so that interior/exterior girders are nearly the same size. O S(typ) Wider girder spacing - Use 10 to 11 with spans less than 140. Use 11 to 14 with spans greater than 140. Consider clearance issues, staged re-decking and phased construction considerations & deck costs Girder Spacing Benefit of Wide Girder Spacing - Reduced number of girders to detail, fabricate, paint, transport, erect, inspect and maintain. - Fewer diaphragms, crossframes and bearings. - MAYBE more pounds, but FEWER dollars

16 Girder Spacing & Deck Overhangs Total factored moment tends to be larger in exterior girders (also subject to overhang loads). Limit size of deck overhangs accordingly S To 0.35S S(typ) Girder Proportioning Web 1/2 minimum thickness preferred by fabricators. Flange b f 12 and t f ¾ preferred by fabricators. Stiffener and Connection 7/16 minimum, 1/2 preferred by fabricators. b f t w t f D

17 Flange Proportioning Flange transitions welded shop splices): Limit number of different plate thicknesses used for a given project. Avoid changing flange width at a welded shop splice. Reduce flange thickness by no more than one-half the thickness of the thicker plate at shop splices. Allow fabricators to eliminate splices within a shipping piece by carrying thicker material through to next designed splice location Cross-Frame Spacing Trade Offs Closer spacing Lower cross-frame forces. Lower lateral flange moments. Higher compression-flange capacity. vs. Higher cross-frame cost. Larger spacing Lower cross-frame cost. vs. Larger cross-frame forces. Larger lateral flange moments. Lower compression-flange capacity

18 Field-Section Lengths Field sections - Girder sections fabricated and shipped to the bridge site. Shipping and handling concerns are important. Affect field section lengths selected in design. Curved members can require additional field splices to reduce size of shipping piece Field-Section Lengths Shipment by truck is the most common means 175 ft. Length Possible, 80 ft. Comfortable. 100 Tons Maximum, 40 Tons No Permit. 16 ft. Width Maximum. 10 ft. Height

19 Corrosion Protection Uncoated Weathering Steel 37 Uncoated Weathering Steel - Benefits Lower Fab Cost Shorter Fab Time No Field Painting Natural Appearance Minimal Maintenance Lower Life Cycle Cost

20 Uncoated Weathering Steel - Use What other states are doing? Blast facia girders. Detailed to eliminate staining. No painting of girder ends. Mandating its use on all projects Uncoated Weathering Steel - Research Ongoing research at University of Delaware. In use for nearly 50 years in United States. Design and maintenance practices may be more influential to UWS performance than climate. UWS bridges generally perform well in relation to non-uws bridges. Source: National Review on Use and Performance of Uncoated Weathering Steel Highway Bridges, McConnell et al.,

21 Steel I-Girder Bridge Behavior Effect of Skewed Supports 41 Skew Effects Skewed supports are frequently required to span highways and streams not perpendicular to the bridge alignment. Elimination of skews may reduce cost by reducing the length of piers and abutments, but usually increases the span. The significance of skew increases with increasing skew and bridge width

22 Skew Effects 43 Skew Effects

23 Skew Effects 45 Skew Effects

24 Dead Load Camber Article AASHTO Article Fit Decision For straight skewed I-girder bridges and horizontally curved I-girder bridges with or without skewed supports, the contract documents should clearly state an intended erected position of the girders and the condition under which that position is to be theoretically achieved Dead Load Camber Article The Fit Decision Allows Fabricator/Detailer complete shop drawings and successfully fabricate the bridge components. Allows Erector/Contractor assemble the steel and achieve the desired geometry in the field. Affects design decisions regarding rotation demands on the bearings. Affects internal force effects for which the cross-frames and girders must be designed

25 Skewed and Curved I-Girder Fit Guide What is Fit? Common Fit Conditions Customary Practice Recommended Fit Conditions Special Considerations Design and Analysis Conclusion Common Fit Conditions Loading Condition Fit No-Load Fit (NLF) Steel Dead Load Fit (SDLF) Total Dead Load Fit (TDLF) Construction Stage Fit Fully- Cambered Fit Erected Fit Final Fit Description The cross-frames are detailed to fit to the girders in their fabricated, plumb, fully-cambered position under zero load. The cross-frames are detailed to fit to the girders in their ideally plumb as-deflected positions under the self-weight of the steel at the completion of the erection. The cross-frames are detailed to fit to the girders in their ideally plumb as-deflected positions under the total dead load

26 Lack-of-Fit - SDLF or TDLF Cross-frames are detailed to connect to an ideal plumb deflected position of the girders Cross-frame do not fit with the girders in the initial fullycambered No Load geometry. Displacement incompatibility between a girder and a cross-frame under No-Load (NL) due to TDLF detailing Plumb fully-cambered No-Load (NL) girder geometry The displacement compatibility on the right-hand side of the cross-frame is referred to as a lack-of-fit Lack-of-Fit - SDLF or TDLF Some force must be induced in the structure to resolve the displacement incompatibility. When the girders and cross-frames are forced to fit together by the Erector, the initial lack-of-fit results in twisting of the girders. The twisting is generally in the opposite direction from which the girders want to twist under the targeted dead load

27 Lack-of-Fit - SDLF or TDLF Once these twist rotations are combined with the twist rotations caused by the targeted dead load, the girders deflect into an approximately plumb position under the targeted dead load condition. Internal forces associated with the resolution of the lackof-fit are referred to as locked-in forces Straight Skewed I-Girder Bridges When cross-frames are connected, the girders deflect After to Connecting the Girders Skew Angle = 60 vertically and Uniform simultaneously Scaling twist under the dead loads. If detailed for SDLF, cross-frame connections to the girders can be completed with little forcing. If detailed for TDLF, Erector may need to apply greater force to complete the connections

28 Straight Skewed I-Girder Bridges Once installed, cross-frames typically hold the girders in their intended plumb position under the targeted dead load. Locked-in forces due to the lack-of-fit detailed between the cross-frames and girders are approximately canceled (offset) by the dead load effects. Locked-in forces tend to be largely opposite in sign (direction) to the internal dead load forces & stresses Recommended Fit Conditions Straight Skewed I-Girder Bridges Square Bridges and Skewed Bridges up to 20 degree +/- Skew Recommended Acceptable Avoid Any span length Any None 20 +/- Any Span

29 Recommended Fit Conditions Straight Skewed I-Girder Bridges Skewed Bridges with Skew > 20 degrees +/- and I s /- Recommended Acceptable Avoid Any span length TDLF or SDLF NLF >20 +/- Any Span 57 I w tan g S /- Ls AASHTO LRFD Eq Recommended Fit Conditions Straight Skewed I-Girder Bridges Skewed Bridges with Skew > 20 degrees +/- and I s > /- Recommended Acceptable Avoid Span lengths up to 200 feet +/- SDLF TDLF NLF Span lengths greater than 200 feet +/- SDLF TDLF & NLF >20 +/ I w tan See Table Above g S > /- Ls AASHTO LRFD Eq

30 Resources and Support Online and Download 59 Steel Bridge Design Resources LRFD Simon. AASHTO 5 th Edition Specification Steel Plate and Tub girder analysis and design. New 7 th Edition Specification Available early NSBA Bolted Splice. AASHTO 5 th Edition Specification Bolted Splice analysis and design

31 Steel Bridge Design Resources espan140 Web based design solution. Economically competitive. Expedite and Economize the Design Process. Simple Repetitive Details and Member Sizes. Bridge Parameters Span Lengths: 40 ft to 140 ft (in 5 increments). Girder Spacing: 6 ft, 7.5 ft, 9 ft and 10.5 ft. Homogeneous and hybrid plate girders with limited plate sizes. Limited depth and lightest weight rolled sections. Selective Cross-Frame Placement & Design Steel Bridge Design References Steel Bridge Design Handbook. AASHTO/NSBA Collaboration Standards. Skewed and Curved Steel I-Girder Bridge Fit. Modern Steel Construction

32 Steel Bridge Design References NCHRP Report 725: Guidelines for Analysis Methods & Construction Engineering of Curved & Skewed Steel Girder Bridges. NHI Course : Analysis & Design of Skewed & Curved Steel Bridges with LRFD More Information American Institute of Steel Construction Steel Bridge Suite espan140 Modern Steel Construction Magazine

33 THANK YOU Christopher Garrell, PE, LEED AP NSBA - Southeast Regional Director garrell@steelbridges.org