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CEE320 Midterm Exam

CEE320 Midterm Exam. 10 True/false (20% of points) 4 Short answer (20% of points) 3 Calculations (60% of points) Homework In class examples. Course material covered. Introduction Vehicle dynamics (chapter 2) Geometric design (chapter 3)

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CEE320 Midterm Exam

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  1. CEE320 Midterm Exam • 10 True/false (20% of points) • 4 Short answer (20% of points) • 3 Calculations (60% of points) • Homework • In class examples

  2. Course material covered • Introduction • Vehicle dynamics (chapter 2) • Geometric design (chapter 3) • Pavement design (chapter 4 except 4.3, 4.5, including 4th power thumbrule)

  3. Suggestions for Preparation • Review each lecture and identify the main points and formulas. Write these on summary notes. • For each lecture, write an question. Do this in a group, and share questions. • Solve these questions from scratch, do not just review solutions. • Review homework and in class examples. Do the problem yourself. • Make a list of the tables in the text, their title, and the page number. Include a note of what it is used for.

  4. The science of safe and efficient movement of people and goods Transportation Engineering

  5. Road Use Growth From the Bureau of Transportation Statistics, National Transportation Statistics 2003

  6. Sum forces on the vehicle

  7. Aerodynamic Resistance Ra Composed of: • Turbulent air flow around vehicle body (85%) • Friction of air over vehicle body (12%) • Vehicle component resistance, from radiators and air vents (3%) from National Research Council Canada

  8. Power required to overcome Ra • Power • work/time • force*distance/time • Ra*V

  9. Rolling Resistance Rrl Composed primarily of • Resistance from tire deformation (90%) • Tire penetration and surface compression ( 4%) • Tire slippage and air circulation around wheel ( 6%) • Wide range of factors affect total rolling resistance • Simplifying approximation:

  10. Grade Resistance Rg Composed of • Gravitational force acting on the vehicle • The component parallel to the roadway θg For small angles, Rg θg W G=grade, vertical rise per horizontal distance (generally specified as %)

  11. Engine-Generated Tractive Effort

  12. Braking Force • Ratio • Efficiency We develop this to calculate braking distance – necessary for roadway design

  13. Braking Distance • Theoretical • Practical

  14. Stopping Sight Distance (SSD) • Worst-case conditions • Poor driver skills • Low braking efficiency • Wet pavement • Perception-reaction time = 2.5 seconds • Equation

  15. Stationing – Linear Reference System Horizontal Alignment 2+00 0+00 1+00 3+00 Vertical Alignment 100 feet >100 feet

  16. Vertical Curve Fundamentals PVI G1 δ PVC G2 PVT L/2 L=curve length on horizontal x • Choose Either: • G1, G2 in decimal form, L in feet • G1, G2 in percent, L in stations

  17. Relationships

  18. Other Properties • K-Value (defines vertical curvature) • The number of horizontal feet needed for a 1% change in slope • A as a percentage • L in feet

  19. Crest Vertical Curves For S < L For S > L

  20. Sag Vertical Curves Light Beam Distance (S) G1 headlight beam (diverging from LOS by β degrees) G2 PVT PVC h1=H PVI h2=0 L For S < L For S > L

  21. Underpass Sight Distance

  22. Underpass Sight Distance • On sag curves: obstacle obstructs view • Curve must be long enough to provide adequate sight distance (S=SSD) S<L S>L

  23. Horizontal Curve Fundamentals PI T Δ E M L Δ/2 PT PC R R Δ/2 Δ/2

  24. Stopping Sight Distance SSD (not L) Ms Obstruction Rv Δs

  25. Minimum radius that provides for safe vehicle operation Given vehicle speed, coefficient of side friction, gravity, and superelevation Rv because it is to the vehicle’s path (as opposed to edge of roadway) Superelevation

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