Diseño de puentes

LRFD Design Example
for

December 2003 FHWA NHI-04-042

Steel Girder Superstructure Bridge

Prepared for

FHWA / National Highway Institute Washington, DC

SI Units

Prepared by

Michael Baker Jr Inc Moon Township, Pennsylvania

Detailed Outline

Design Example for a Two-Span Bridge

Development of a Comprehensive Design Example for a Steel Girder Bridge with CommentaryDetailed Outline of Steel Girder Design Example
1. 1.1 General Obtain design criteria 1.1.1 Governing specifications, codes, and standards 1.1.2 Design methodology 1.1.3 Live load requirements 1.1.4 Bridge width requirement 1.1.4.1 Number of design lanes (in each direction) 1.1.4.2 Shoulder, sidewalk, and parapet requirements 1.1.4.3 Bridge width 1.1.5 Clearance requirements 1.1.5.1 Horizontalclearance 1.1.5.2 Vertical clearance 1.1.6 Bridge length requirements 1.1.7 Material properties 1.1.7.1 Deck concrete 1.1.7.2 Deck reinforcing steel 1.1.7.3 Structural steel 1.1.7.4 Fasteners 1.1.7.5 Substructure concrete 1.1.7.6 Substructure reinforcing steel 1.1.8 Future wearing surface requirements 1.1.9 Load modifiers 1.1.9.1 Ductility 1.1.9.2 Redundancy 1.1.9.3 Operational importance Obtaingeometry requirements 1.2.1 Horizontal geometry 1.2.1.1 Horizontal curve data 1.2.1.2 Horizontal alignment 1.2.2 Vertical geometry 1.2.2.1 Vertical curve data 1.2.2.2 Vertical grades Span arrangement study 1.3.1 Select bridge type 1.3.2 Determine span arrangement 1.3.3 Determine substructure locations 1.3.3.1 Abutments 1.3.3.2 Piers

1.2

1.3

FHWA LRFD Steel Design Example

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DetailedOutline

Design Example for a Two-Span Bridge

1.4

1.5

1.6

1.3.4 Compute span lengths 1.3.5 Check horizontal clearance requirements Obtain geotechnical recommendations 1.4.1 Develop proposed boring plan 1.4.2 Obtain boring logs 1.4.3 Obtain foundation type recommendations for all substructures 1.4.3.1 Abutments 1.4.3.2 Piers 1.4.4 Obtain foundation design parameters 1.4.4.1 Allowablebearing pressure 1.4.4.2 Allowable settlement 1.4.4.3 Allowable stability safety factors • Overturning • Sliding 1.4.4.4 Allowable pile resistance • Axial • Lateral Type, Size and Location (TS&L) study 1.5.1 Select steel girder types 1.5.1.1 Composite or noncomposite superstructure 1.5.1.2 Plate girder or roll section 1.5.1.3 Homogeneous or hybrid 1.5.2 Determine girder spacing 1.5.3 Determineapproximate girder depth 1.5.4 Check vertical clearance requirements Plan for bridge aesthetics 1.6.1 Function 1.6.2 Proportion 1.6.3 Harmony 1.6.4 Order and rhythm 1.6.5 Contrast and texture 1.6.6 Light and shadow Concrete Deck Design Obtain design criteria 2.1.1 Girder spacing 2.1.2 Number of girders 2.1.3 Reinforcing steel cover 2.1.3.1 Top 2.1.3.2 Bottom 2.1.4 Concrete strength 2.1.5 Reinforcing steelstrength 2.1.6 Concrete density 2.1.7 Future wearing surface 2.1.8 Concrete parapet properties

2. 2.1

FHWA LRFD Steel Design Example

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Detailed Outline

Design Example for a Two-Span Bridge

2.2 2.3 2.4 2.5 2.6 2.7

2.8 2.9 2.10 2.11 2.12

2.13 2.14 2.15 2.16 2.17 2.18 2.19 3.

2.1.8.1 Weight per unit length 2.1.8.2 Width 2.1.8.3 Center of gravity 2.1.9 Design method (assumeStrip Method) 2.1.10 Applicable load combinations 2.1.11 Resistance factors Determine minimum slab thickness 2.2.1 Assume top flange width 2.2.2 Compute effective span length Determine minimum overhang thickness Select thicknesses 2.4.1 Slab 2.4.2 Overhang Compute dead load effects 2.5.1 Component dead load, DC 2.5.2 Wearing surface dead load, DW Compute live load effects 2.6.1 Dynamic loadallowance 2.6.2 Multiple presence factor Compute factored positive and negative design moments for each limit state 2.7.1 Service limit states (stress, deformation, and cracking) 2.7.2 Fatigue and fracture limit states (limit cracking) 2.7.3 Strength limit states (strength and stability) 2.7.4 Extreme event limit states (e.g., earthquake, vehicular or vessel collision) Design for positive flexure in...