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Questions and Answers
Dynamic pavement response is easier to analyze than static response.
Dynamic pavement response is easier to analyze than static response.
False
Passenger cars typically have dual wheels on their axles.
Passenger cars typically have dual wheels on their axles.
False
Doubling the load magnitude will always double the rate of pavement deterioration.
Doubling the load magnitude will always double the rate of pavement deterioration.
False
Higher tyre pressures in trucks lead to faster deterioration of the pavement surface.
Higher tyre pressures in trucks lead to faster deterioration of the pavement surface.
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Predicting future traffic growth is always accurate, ensuring precise pavement design.
Predicting future traffic growth is always accurate, ensuring precise pavement design.
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Environmental conditions have no effect on the properties of pavement materials.
Environmental conditions have no effect on the properties of pavement materials.
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Trucks typically have tyre pressures between 100 - 115 psi.
Trucks typically have tyre pressures between 100 - 115 psi.
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Different axle configurations do not influence pavement performance.
Different axle configurations do not influence pavement performance.
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Slab thicknesses for PCC highway pavements typically range from 8 to 12 feet.
Slab thicknesses for PCC highway pavements typically range from 8 to 12 feet.
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A flexible pavement reduces stresses by transmitting traffic loads directly to the subgrade.
A flexible pavement reduces stresses by transmitting traffic loads directly to the subgrade.
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The material for the base course in a flexible pavement is typically stabilized aggregates.
The material for the base course in a flexible pavement is typically stabilized aggregates.
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The average lifespan of a flexible pavement is estimated to be between 10 to 15 years.
The average lifespan of a flexible pavement is estimated to be between 10 to 15 years.
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Subbase layers are always used in the construction of flexible pavements.
Subbase layers are always used in the construction of flexible pavements.
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Rutting and fatigue cracking are examples of distresses that can accumulate over the lifespan of flexible pavements.
Rutting and fatigue cracking are examples of distresses that can accumulate over the lifespan of flexible pavements.
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A cone of distributed loads helps to concentrate stresses at the subgrade level.
A cone of distributed loads helps to concentrate stresses at the subgrade level.
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Hot-mix asphalt is also known as asphalt concrete in flexible pavement design.
Hot-mix asphalt is also known as asphalt concrete in flexible pavement design.
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An 18-kip single-axle load is equivalent to 18,000 pounds.
An 18-kip single-axle load is equivalent to 18,000 pounds.
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A 44-kip tandem-axle load has a W18 value of 1.44.
A 44-kip tandem-axle load has a W18 value of 1.44.
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ZR represents the probability that serviceability will be maintained from a user’s perspective.
ZR represents the probability that serviceability will be maintained from a user’s perspective.
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The z-statistic is derived from a uniform distribution.
The z-statistic is derived from a uniform distribution.
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Reliability values for local roads can be as high as 90%.
Reliability values for local roads can be as high as 90%.
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Transverse cracks are important for evaluating the distress of flexible pavements.
Transverse cracks are important for evaluating the distress of flexible pavements.
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Highways such as interstates require a low reliability level due to the high cost of reconstruction.
Highways such as interstates require a low reliability level due to the high cost of reconstruction.
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Tables 4.1, 4.2, and 4.3 present axle-load equivalency factors for flexible pavement design.
Tables 4.1, 4.2, and 4.3 present axle-load equivalency factors for flexible pavement design.
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Joint faulting in rigid pavements is an indicator of erosion or fatigue beneath the slab.
Joint faulting in rigid pavements is an indicator of erosion or fatigue beneath the slab.
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The impact of an axle load on pavement is measured only in terms of weight.
The impact of an axle load on pavement is measured only in terms of weight.
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Punchouts occur in Continuously Reinforced Concrete Pavements due to widely spaced transverse cracks.
Punchouts occur in Continuously Reinforced Concrete Pavements due to widely spaced transverse cracks.
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The International Roughness Index is used to measure the impact of faulting on pavement smoothness.
The International Roughness Index is used to measure the impact of faulting on pavement smoothness.
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Rigid pavements are built with expansion and contraction joints to allow for thermal movement.
Rigid pavements are built with expansion and contraction joints to allow for thermal movement.
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Fatigue damage in rigid pavements is assessed through the measurement of transverse cracks only.
Fatigue damage in rigid pavements is assessed through the measurement of transverse cracks only.
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The overall standard deviation, So, only accounts for the statistical error in the equations used in pavement design.
The overall standard deviation, So, only accounts for the statistical error in the equations used in pavement design.
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The terminal serviceability index, TSI, indicates the maximum performance level of the pavement.
The terminal serviceability index, TSI, indicates the maximum performance level of the pavement.
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Increased roughness from punchouts can affect the overall performance of the pavement.
Increased roughness from punchouts can affect the overall performance of the pavement.
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The spacing of transverse cracks is not relevant to the structural integrity of the pavement.
The spacing of transverse cracks is not relevant to the structural integrity of the pavement.
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The amount of serviceability loss, ∆PSI, is calculated as the difference between the initial PSI and the TSI.
The amount of serviceability loss, ∆PSI, is calculated as the difference between the initial PSI and the TSI.
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The average 28-day strength of concrete is typically measured in units of psi rather than lb/in2.
The average 28-day strength of concrete is typically measured in units of psi rather than lb/in2.
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A drainage coefficient, Cd, value of 1.0 indicates poor drainage characteristics of a material.
A drainage coefficient, Cd, value of 1.0 indicates poor drainage characteristics of a material.
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Most highway agencies perform detailed tests to measure the modulus of subgrade reaction, k.
Most highway agencies perform detailed tests to measure the modulus of subgrade reaction, k.
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Typical values for the concrete modulus of elasticity, Ec, range between 3 and 7 million lb/in2.
Typical values for the concrete modulus of elasticity, Ec, range between 3 and 7 million lb/in2.
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The load transfer coefficient, J, is used to account for the load transfer capability of pavement across slab joints.
The load transfer coefficient, J, is used to account for the load transfer capability of pavement across slab joints.
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Rain and freeze-thaw cycles weaken the HMA materials and reduce the load carrying capacity of the subgrade.
Rain and freeze-thaw cycles weaken the HMA materials and reduce the load carrying capacity of the subgrade.
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The same road can be built over different subgrade materials without affecting pavement thickness requirements.
The same road can be built over different subgrade materials without affecting pavement thickness requirements.
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Channelized traffic load results in uniform deterioration across the pavement surface.
Channelized traffic load results in uniform deterioration across the pavement surface.
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The distribution of stresses and strains in a multi-layer pavement system is independent of the material properties of the layers.
The distribution of stresses and strains in a multi-layer pavement system is independent of the material properties of the layers.
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Pavement failure occurs when the applied stresses exceed the strength of the material.
Pavement failure occurs when the applied stresses exceed the strength of the material.
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The AASHTO Guide for Design of Pavement Structures is a key resource for flexible-pavement design procedures.
The AASHTO Guide for Design of Pavement Structures is a key resource for flexible-pavement design procedures.
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Pavement structure typically consists of a single layer built directly on the subgrade.
Pavement structure typically consists of a single layer built directly on the subgrade.
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HMA ages over time, leading to increased flexibility and decreased susceptibility to cracking.
HMA ages over time, leading to increased flexibility and decreased susceptibility to cracking.
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Study Notes
Course Information
- Course title: Highway and Railroad Engineering
- Course code: HRE 313
- Edition: First, 2021
- Institution: President Ramon Magsaysay State University
Module Overview
- Module introduces highway and railroad engineering
- Covers topics in structural design of pavements
- Includes discussion of flexible and rigid pavements
- Sample: Typical flexible pavement consists of surface, base course, and subbase over compacted subgrade
- Common distresses of pavements include fatigue cracking, rutting, roughness, and thermal cracking
- Rigid pavements are commonly found in major highways and airports
Pavement Types
- Two main types: flexible and rigid
- Flexible pavements are built with layers of asphaltic cement and aggregates
- Subgrade, subbase, base, and wearing surface are common layers in flexible pavements
- Rigid pavements are constructed using portland cement concrete (PCC) and aggregates
- Base layer is optional, depending on subgrade soil
- Transverse contraction joints are built into the pavement to control cracking
Flexible Pavement Design
- Pavement system design is aimed at reducing and distributing surface stresses to acceptable levels at subgrade
- Stresses are transmitted through aggregate-to-aggregate particle contact
- Confining pressures in subbase and base layers increase bearing strength
- Cone of distributed loads reduces and distributes stresses to subgrade
Unique Properties of Flexible Pavements
- Deterioration over time: Each load application contributes to distresses like rutting, fatigue cracking, disintegration, roughness, and bleeding
- Repeated loads: Dynamic pavement response from traffic loads
- Variable load configuration: Axles can be single, tandem, or multiple, while wheels can be single or dual.
- Variable load magnitude: Increasing load significantly increases the rate of deterioration
- Variable tyre pressure: Higher pressures result in increased contact pressure and faster deterioration of the surface layer
- Traffic growth: Future traffic growth affects the accuracy of predictions of pavement performance and designed life
Rigid Pavement
- Rigid pavements use portland cement concrete (PCC)
- Drainage characteristics of subgrade are important, with drainage coefficients considered in design
- Base layer is optional, depending on subgrade characteristics
- Transverse contraction joints are built into the pavement to control shrinkage cracking
- Load transfer devices like dowel bars help minimize deflection and stresses near edges of slabs
Pavement System Design
- Traditional AASHTO flexible pavement design in the AASHTO guide
- The amount of serviceability loss (APSI) over pavement life
- The overall standard deviation (So) from variability in materials and construction practices
- Structural number (SN) represents the overall structural requirement
Pavement Quality and Performance
- International Roughness Index (IRI) measures surface roughness, important for safety
- Pavement friction measurements are conducted, particularly under wet conditions, to estimate the friction number
Pavement Distress
- Rut depth: Surface deformation in wheel paths affecting vehicle safety due to hydroplaning
- Cracking: Material fatigue can lead to faulting, transverse cracking, alligator cracking, and others
- Faulting: Different slab elevations in JPCP, an indicator of fatigue in layers or transfer ability
- Punchouts: Fatigue damage in CRCP slabs
References
- Includes materials from several texts, including "Principles of Highway Engineering & Traffic Analysis" and the "Handbook of Highway Engineering"
Assignment
- Task: Explain the difference between flexible and rigid pavements
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Description
This quiz covers the fundamental concepts of highway and railroad engineering focusing on the structural design of pavements. It includes discussions on flexible and rigid pavements, their components, and common distresses. Test your knowledge on pavement types and their characteristics.
