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CE 436/536 – ROADWAY DESIGN February 12, 2008

CE 436/536 – ROADWAY DESIGN February 12, 2008. Review Homework Assignment #3 and #4 Half of the lane width for radius discussion, when to use. Topics to cover this week: Superelevation refresher Cross-sectional geometry Vertical alignments/geometry. HW #3 Solutions.

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CE 436/536 – ROADWAY DESIGN February 12, 2008

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  1. CE 436/536 – ROADWAY DESIGN February 12, 2008 • Review Homework Assignment #3 and #4 • Half of the lane width for radius discussion, when to use. • Topics to cover this week: • Superelevation refresher • Cross-sectional geometry • Vertical alignments/geometry

  2. HW #3 Solutions

  3. Important Equations To Know So Far

  4. Let’s work a few more problems together. Text problem #3.26 Find the length of runoff and runout for a 55 mph design on a two lane roadway with an e of 0.08 ft/ft.

  5. Superelevation – Refresher • How do we select the proper super rate? • What is super runoff? • What is tangent runout? • Where do we place the superelevationtransistion along the horizontal alignment? • Rotation of the roadway about a longitudinal axis

  6. Cross – Sectional Geometry • Cross-sectional geometry is the first thing you determine in the design process. • What is cross-sectional geometry composed of? • Widths of lanes, shoulders, medians, ditches, etc. • Depths of base materials and pavements, etc.

  7. Cross – Sectional Geometry

  8. Cross – Sectional Geometry

  9. Cross – Sectional Geometry

  10. Cross – Sectional Geometry • Nomenclature used in Roadway Cross-sections: • Travel Lane • Traveled Way • Roadway • Paved Shoulder • Gravel Shoulder • Median • Subgrade • Base • Pavement – base course(s) and wearing course • Subgrade Shoulder • Ditch • Foreslope • Backslope • Cut • Fill • Typical Section • Horizontal:Vertical – Slopes • Curb • Gutter

  11. Cross – Sectional Geometry • How do we determine what widths and depths to use? • Widths – from design manuals based on functional classification, speed, local standards. • Depths of material depending on cost, subgrade material, loading, etc. • Let’s look at what AASHTO says about lane and shoulder widths. • Insert scans from AASHTO pages 315-319

  12. Cross – Sectional Geometry

  13. Cross – Sectional Geometry

  14. Cross – Sectional Geometry • Later in the semester we will talk about “Clear Zone” which is the area beyond the traveled way which needs to be considered in roadway design. • There really are not many calculations used to establish a design cross-section, assuming the pavement design is provided by others. Pavement design is almost always provided by a specialist in materials and/or pavements.

  15. Vertical Alignments/Geometry • Text Page 47, Section 3.3, 1st Paragraph • Crest Vertical Curves • Sag Vertical Curves • Equal Tangent Vertical Curves • Nomenclature: G1, G2, PVC, PVI, PVT, L, A

  16. Vertical Alignments/Geometry • The length of a horizontal curve is measured along the curve. • The length of a vertical curve is measured horizontally. • Example: • A 400 foot vertical curve has an entrance grade of +2.0% and an exit grade of -3.0%. The station and elevation of the PVC is 10+00 and 5000 feet, repsectively. What is the station and elevation of the PVI and PVT?

  17. Vertical Alignments/Geometry • Solution • PVI = 10+00 + 2+00 = 12+00 • PVT = 10+00 + 4+00 = 14+00 • PVI elevation = 5000 + 200(.02) = 5004 feet • PVT elevation = 5004 – 200(.03) = 4998 feet

  18. Vertical Alignments/Geometry • Other important vertical curve relationships: • Y, Ym, Yf– what are these why would we use them?

  19. Vertical Alignments/Geometry • Other important vertical curve relationships: • Y, Ym, Yf– what are these why would we use them? Page 53/54 Text. • Using our previous sample problem, let’s calculate all of these values, with “x” at 50 feet from the PVC.

  20. Vertical Alignments/Geometry • Other important vertical curve relationships: • K = L/A (it will turn out this is the most fundamental/useful vertical curve equation we will use) • K = horizontal distance (ft) required to effect a 1% change in the slope of the vertical curve. • The high or low point on the curve can be calculated using K. • Let’s go through Example 3.3, Page 54 in Text.

  21. Homework Assignment #5 February 12, 2008 Homework, due February 19th: PROBLEM #1 Given: A vertical curve crosses a creek perpendicular to the creek centerline. The elevation at the bottom of the creek at roadway centerline is 100.00 feet. The vertical curve characteristics are as follows: G1 = -3.0% G2 = +2.0% PVI station = 400+00 PVI elevation = 98.00 feet A 36” pipe needs to be placed in the creek so the road can cross it. There needs to be 3.0 feet of cover over the top of the pipe, i.e. 3.0 feet between the top of the pipe and the roadway finished grade. Assume the midpoint of the curve is at the creek centerline. Find: Design a vertical curve to accomplish the task by finding: The length of the curve The elevation of the curve finished grade at the midpoint The PVC and PVT elevations and stations K value for the curve Station of the low point of the curve PROBLEM #2 – text problem #3.1 PROBLEM #3 – text problem #3.2

  22. Pop Quiz #1 February 12, 2008 1) Problem 2.29 from text. 2) Problem 3.23 from text. 3) Define “Tangent Runout” and “Super Runoff”

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