05 asphalt institute

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Asphalt Institute Flexible Pavement Structural Design: 

Asphalt Institute Flexible Pavement Structural Design

Outline: 

Outline Origins Overview Example Problem

Origins: 

Origins Asphalt Institute Manual Series 1 (MS-1) From the Chevron N-layer method Published in 1981 Procedure Uses graphs in MS-1 Uses a PC-based program

Overview: 

Overview Mechanistic-empirical design Limit tensile strain on bottom of HMA layer Limit vertical strain on top of subgrade

Subgrade: 

Subgrade Uses Resilient modulus (MR) Procedure to select design MR

Estimating ESALs: 

Estimating ESALs Uses “Truck Factors” Average ESALs for a given truck type

Truck Distribution - Rural: 

Truck Distribution - Rural From MS-1, Table IV-1

Truck Distribution – Urban: 

Truck Distribution – Urban From MS-1, Table IV-1

Truck Factors – Rural: 

Truck Factors – Rural From MS-1, Table IV-5

Truck Factors – Urban: 

Truck Factors – Urban From MS-1, Table IV-5

Limitations: 

Limitations Most data over 20 years old Does not consider top down cracking Core from Makakilo Dr.

Asphalt Institute Method: 

Asphalt Institute Method Example

Step 1: Traffic Calculation: 

Step 1: Traffic Calculation Total ESALs Buses + Trucks 2.13 million + 1.33 million = 3.46 million

Step 2: Get MR Value: 

Step 2: Get MR Value CBR tests along Kailua Road show: CBR ≈ 8 MR conversion AASHTO Conversion NCHRP 1-37A Conversion This is different from your notes, but consistent with the other examples.

Step 3: Select Climate: 

Step 3: Select Climate Determines HMA & subgrade properties Can select mean annual air temperature (MAAT): 45°F (frost effects) 60°F (possible frost effects) 75°F (no frost effects) Software allows more selections

Step 4: Calculate Design: 

Step 4: Calculate Design Decide on basic structure HMA Aggregate base (6 or 12 inches) Software allows for more choices Can also choose Full-depth asphalt HMA over emulsified asphalt base

Step 4: Calculate Design: 

Step 4: Calculate Design Use graph Source: Asphalt Institute, MS-1, 1981

Step 4: Calculate Design: 

Step 4: Calculate Design Final Design 9.5 inches HMA 2.5 inches Mix IV (½ inch Superpave) 7 inches ACB (¾ inch Superpave) 12 inches aggregate base 6 inches UTB 6 inches aggregate subbase

Comparison: 

Comparison

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