CEE320 Midterm Exam

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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
• 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)
• Pavement design (chapter 4 except 4.3, 4.5, including 4th power thumbrule)
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.

From the Bureau of Transportation Statistics, National Transportation Statistics 2003

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%)

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

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 %)

Braking Force
• Ratio
• Efficiency

We develop this to calculate braking distance – necessary for roadway design

Braking Distance
• Theoretical
• Practical
Stopping Sight Distance (SSD)
• Worst-case conditions
• Poor driver skills
• Low braking efficiency
• Wet pavement
• Perception-reaction time = 2.5 seconds
• Equation
Stationing – Linear Reference System

Horizontal Alignment

2+00

0+00

1+00

3+00

Vertical Alignment

100 feet

>100 feet

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
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
Crest Vertical Curves

For S < L

For S > L

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

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

Horizontal Curve Fundamentals

PI

T

Δ

E

M

L

Δ/2

PT

PC

R

R

Δ/2

Δ/2

Stopping Sight Distance

SSD (not L)

Ms

Obstruction

Rv

Δs

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