assignment 1-201720182 - universiti teknologi malaysia · 2018-03-25 · reinforced 3.2 3.8 -4.4...
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Assignment 1-201720182
1. A two lane interstate expressways of jointed reinforce concrete pavement
(JRCP) with average daily traffic (ADT) 40 000 (both ways), is to be design
according to PCA method. The pavement will be built on cement stabilized
subbase with a design life of 20 years. The percentage of trucks was found to
be 13% with yearly rates of 4% in traffic growth. The pavement is to be designed
with tied Portland concrete shoulder. The modulus of subgrade reaction is 80
MPa/m and the concrete modulus of rupture is 4.0 MPa. Use the load frequency
distribution data given in Table 1.1. Check the adequacy of 210 mm concrete
slab thickness and discuss your findings. Please state clearly your assumptions.
Use all the charts and tables given.
(15 marks)
Table 1.1 Load frequency distribution
Single Axles
Axle Load (kN) Axles per 1000 trucks
133 0.58
125 1.35
115 2.77
107 5.92
98 9.83
88 21.67
Tandem Axles
Axle Load (kN) Axles per 1000 trucks
231 1.96
213 3.94
195 11.48
178 34.27
160 81.42
142 85.54
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Table 1.2 Load safety factor
Road classification Load safety factor
Interstate Pavements 1.2
Highways and arterials streets 1.1
Roads , low volume streets 1.0
Figure 1.1 Percentage of trucks in right lane of a multilane divided highway
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Table 1.3 Yearly rates of traffic growth and corresponding projection factors
Yearly rate of traffic
growth %
Projection factor, 20 years Projection factor, 40 years
1 1.1 1.2
1 ½ 1.2 1.3
2 1.2 1.5
2 ½ 1.
3
1.6
3 1.3 1.8
3 ½ 1.4 2.0
4 1.5 2.2
4 ½ 1.6 2.4
5 1.6 2.7
5 ½ 1.7 2.9
6 1.8 3.2
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Table 1.4 Equivalent stress- with concrete shoulder (Single Axle/Tandem Axle)
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Table 1.5 Erosions factors- doweled joints, concrete shoulder ( Single Axle/Tandem
Axle)
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Figure 1.2 Fatigue analysis- allowable load repetitions based on stress ratio factor
(with and without concrete shoulder)
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Figure 1.3 Erosion analysis – allowable load repetitions based on erosion factor
(with concrete shoulder)
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2. A continuous reinforced concrete pavement (CRCP) has been designed with a
trial thickness of 250mm. It was designed with a dowel joints and asphalt
shoulder on top of 100mm unstabilized subbase. Based on PCA method,
percentage of fatigue analysis and erosion analysis was found to be 108% and
95% respectively. Please summarize the output of the design .Suggest what are
the steps that can be done in order to improve the results.
(8 marks)
3. A concrete pavement is designed to last 20 years. During the first year, the
estimated two- way equivalent single –axle applications are 300,000. And the
expected annual growth rate is 4%. The design reliability is 90%, and the overall
standard deviation is 0.4. The loss of serviceability is 1.7.
The pavement is to be laid on a granular subbase material. Using the standard
laboratory tests on 28-day specimens, the average compressive strength is 6000
psi, and the average modulus of rupture for third-point loadings is 550 psi.
The drainage is considered to be poor, and the pavement is expected to be
subjected to moisture levels approaching saturation 20% of the time. The
pavement is to be designed with jointed reinforced concrete with dowels and
untied asphalt shoulders. The effective modulus of subgrade reaction (corrected
for loss of support) k= 180 pci.
` Determine the design thickness by the AASHTO method. Use the tables, charts
and formulas given.
Ec= 57, 000 (f’c)0.5
T= [ (1+r)n – 1 ] × T1
r
T1= traffic volume during the first year
r = rate of growth expressed as a fraction
n= design period (years)
(12 marks)
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Table 3.1 Recommended Load –Transfer Coefficients for Various
Pavement Type and Design Conditions
Shoulder Asphalt Tied PCC
Load trasnfer device Yes No Yes No
Pavemet type
1. Plain and
jointed
reinforced
3.2 3.8-4.4 2.5-3.1 3.6-4.2
2. Continuously
reinforced
concrete
pavement
2.9-3.2 N/A 2.3-2.9 N/A
Table 3.2 Recommended Values of Drainage Coefficient, Cd for
Rigid Pavement Design
Quality of
Drainage
Percent of Time Pavement Structure is
Exposed to Moisture Levels Approaching
Saturation
Less
Than 1%
1-5% 5-25% Greater
25%
Excellent 1.25-1.20 1.20-1.15 1.15-1.10 1.10
Good 1.20-1.15 1.15-1.10 1.10-1.00 1.00
Fair 1.15-1.10 1.10-1.00 1.00-0.90 0.90
Poor 1.10-1.00 1.10-0.90 0.90-0.80 0.80
Very Poor 1.00-0.90 0.90-0.80 0.80-0.70 0.70
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Design chart for rigid pavement based on using mean values for each input variable (segment 1)
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Design chart for rigid pavements based on using mean values for each input variables (segment 2)