### Flexible Pavement Design Life AnalysisA flexible pavement has a structural number of 3.8, the initial Present Serviceability Index (PSI) is 4.7, and the terminal serviceability is 2.5. The soil has a resilient modulus of 13,000 psi. The overall standard deviation is 0.4, and the design reliability is 95%. The pavement is currently designed for 1,800 equivalent 18-kip single-axle loads per day.#### Main Problem:1. What is the pavement’s design life in years?#### Extended Problem:2. If the number of 18-kip single-axle loads were to increase by 50%, by how many years would the pavement’s design life be reduced?The following parameters and their values are given:- **Structural Number (SN):** 3.8- **Initial PSI:** 4.7- **Terminal Serviceability:** 2.5- **Resilient Modulus of Soil (Mr):** 13,000 psi- **Standard Deviation (σ):** 0.4- **Design Reliability (R):** 95%- **Daily Load:** 1,800 equivalent 18-kip single-axle loads### Detailed Explanation#### Calculating Pavement Design LifeThe design life of flexible pavement is determined using standard equations and models that incorporate the above parameters. Typically, the AASHTO (American Association of State Highway and Transportation Officials) Guide for Design predicts service life based on the given inputs.1. **Change in the Number of Loads:** - Current loads/day: 1,800 - Increased loads/day (50% increase): \( 1,800 \times 1.5 = 2,700 \)2. **Impact on Design Life:** - The pavement design life is inversely related to the number of loads it experiences. As the number of loads increases, the expected life span of the pavement generally decreases.#### ConclusionTo solve the above questions, you would use detailed pavement design equations which factor in these variables to predict the design life and the impact of increased loads. Calculations typically use logistic or empirical models and often require computational tools for precise answers.By addressing these factors, one can predict the lifecycle and plan appropriate maintenance or design modifications for extending pavement life, even under intensified load conditions.

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A flexible pavement has a structural number of 3.8, the initial PSI is 4.7 and the terminal serviceability is 2.5. The soil has a resilient modulus of 13,000. The overall standard deviation is 0.4 and the design reliability is 95%. The pavement is currently designed for 1800 equivalent 18-kip single-axle loads per day. What is the pavement's design life in years? If the number of 18-kip single-axle loads were to increase by 50%, by how many years would the pavement's design life be reduced?

A flexible pavement has a structural number of 3.8, the initial PSI is 4.7 and the terminal serviceability is 2.5. The soil has a resilient modulus of 13,000. The overall standard deviation is 0.4 and the design reliability is 95%. The pavement is currently designed for 1800 equivalent 18-kip single-axle loads per day. What is the pavement's design life in years? If the number of 18-kip single-axle loads were to increase by 50%, by how many years would the pavement's design life be reduced?

Structural Analysis

6th Edition

ISBN:9781337630931

Author:KASSIMALI, Aslam.

Publisher:KASSIMALI, Aslam.

Chapter2: Loads On Structures

Section: Chapter Questions

Problem 1P

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### Flexible Pavement Design Life Analysis

A flexible pavement has a structural number of 3.8, the initial Present Serviceability Index (PSI) is 4.7, and the terminal serviceability is 2.5. The soil has a resilient modulus of 13,000 psi. The overall standard deviation is 0.4, and the design reliability is 95%. The pavement is currently designed for 1,800 equivalent 18-kip single-axle loads per day.

#### Main Problem:
1. What is the pavement’s design life in years?

#### Extended Problem:
2. If the number of 18-kip single-axle loads were to increase by 50%, by how many years would the pavement’s design life be reduced?

The following parameters and their values are given:
- **Structural Number (SN):** 3.8
- **Initial PSI:** 4.7
- **Terminal Serviceability:** 2.5
- **Resilient Modulus of Soil (Mr):** 13,000 psi
- **Standard Deviation (σ):** 0.4
- **Design Reliability (R):** 95%
- **Daily Load:** 1,800 equivalent 18-kip single-axle loads

### Detailed Explanation

#### Calculating Pavement Design Life
The design life of flexible pavement is determined using standard equations and models that incorporate the above parameters. Typically, the AASHTO (American Association of State Highway and Transportation Officials) Guide for Design predicts service life based on the given inputs.

1. **Change in the Number of Loads:**
- Current loads/day: 1,800
- Increased loads/day (50% increase): \( 1,800 \times 1.5 = 2,700 \)

2. **Impact on Design Life:**
- The pavement design life is inversely related to the number of loads it experiences. As the number of loads increases, the expected life span of the pavement generally decreases.

#### Conclusion
To solve the above questions, you would use detailed pavement design equations which factor in these variables to predict the design life and the impact of increased loads. Calculations typically use logistic or empirical models and often require computational tools for precise answers.

By addressing these factors, one can predict the lifecycle and plan appropriate maintenance or design modifications for extending pavement life, even under intensified load conditions.

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1. During the AASHO road test, ONLY flexible pavements were constructed and tested.a. Trueb. False2. The AASHO present serviceability rating (PSR) was considered an objective quantity used to establish the performance of highway pavement in terms of applied traffic.a. Trueb. False3. The AASHTO present serviceability index (PSI) correlates the PSR to actual pavement performance in terms of applied traffic, and select distresses.a. Trueb. False4. There is only one AASHTO PSI equation that applies to both flexible and rigid pavements.a. Trueb. False5. The AASHTO PSI scale ranges from:a. 0-5b. 0-10c. 0-100d. None of the above
The data given below pertain to the design of a flexible pavement. Initial trafic = 1213 cvpd Traffic growth rate = 8 percent per annum Design life = 12 years Vehicle damage factor = 2.5 Distribution factor = 1.0 The design traffic in terms of million standard axles (msa) to be catered would be
Overall standard deviation, S, Design serviceability loss, APSI 10 5.0 99.9 0.2 99 1.0 0.4 0.5 0.6 90 0.5 0.1 0.05 1.5 2.0 80 70 2.5 60 3.0 50 9 87 65 4 6.5 5.5 4.5 3.5 2 1 Eхample: 2.5 1.5 W18 = 5 x 106 Design structural number, SN R = 95% S, = 0.35 M = 5000 Ib/in² APSI = 1.9 Solution: SN = 5.0
3- What is meant by JRCP in rigid pavements? Explain its characteristics.
A flexible pavement has the following class of loads during a particular hour of the day, i. 80 buses with 2-axles (each axle load of 40 KN): ii. 160 trucks with 2-axles (front and rear axle loads of 40 kN and 80 kN, respectively) The equivalent standard axle load repetitions for this vehicle combination as per IRC:37-2012 would be A. 320 B. 250 C. 240 D. 180
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