MAP 1053/MKAQ 1053 1

FINAL EXAMINATION

SEMESTER I, SESSION 2014/2015

COURSE CODE : MAP 1053/MKAQ 1053

COURSE : PAVEMENT DESIGN AND CONSTRUCTION

PROGRAMME : MAP/MKAQ

DURATION : 2 HOURS 30 MINUTES

DATE : DISEMBER 2014

INSTRUCTION TO CANDIDATES:

1. ANSWERS ALL QUESTIONS

2. NO REFERENCE IS ALLOWED

3. USE SEPARATE ANSWER BOOK FOR PART A AND PART B.

ENCLOSE TABLE 1.7 WITH ANSWER BOOK PART A

WARNING!

Students caught copying/cheating during the examination will be liable for

disciplinary actions and the faculty may recommend the student to be expelled from

the study.

This examination question consists of (13) printed pages only.

MAP 1053/MKAQ 1053 2

PART A:

Q1. (a) 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. As an engineer, please summarize the

output of the design and suggest what are the steps or methods that can be

done in order to improve the results.

(8 marks)

(b) A continues reinforced concrete pavement using gravel as coarse

aggregate is subjected to 107 ESAL. This CRCP is a dual lane with a

width of 12 ft per lane. Indirect tensile strength of the concrete at 28 days

(ft) was found to be 650 psi. Design temperature drop (DTD) for the

concrete pavement is expecting to be 55˚F and wheel load tensile stress is

200 psi. With a 10 inches thickness of concrete slab, determine the

longitudinal numbers of No 6 bars per lane required.

Design tie bars along the longitudinal joints as well. Use billet steel with

intermediate grade as tie bars. Use the tables and formulas given. Please

state clearly your own assumption.

(17 marks)

(25 marks)

αs = 5 x 106 /˚ F

Nmin = 0.01273 Pmin WsD/ Ф2

Nmax = 0.01273 Pmin WsD/ Ф2

As= (γchLfa)/(fs)

As= area of steel required per unit width

fs= allowable stress

γc = unit weight of concrete (0.0868 pci)

h= thickness of the slab (in)

L= distance from longitudinal joint to free edge

where no tie bars exist (in)

fa= average of coefficient of friction

MAP 1053/MKAQ 1053 3

t= ½ ( fsd/ μ)

t= length of tie bar

fs= allowable stress

d= diameter of tie bar

μ= allowable bond stress (350 psi for deformed

bars)

Table 1.1 Approximate Relationship Between Shrinkage and Indirect Tensile

Strength of PCC

Indirect tensile strength (psi) Shrinkage (in./in.)

300 or less 0.0008

400 0.0006

500 0.00045

600 0.0003

700 or greater 0.0002

Table 1.2 Recommended Value of the Thermal Coefficient of PCC as a

Function of Aggregate types

Type of course aggregate Concrete thermal coefficient (10-6/˚F)

Quartz 6.6

Sandstone 6.5

Gravel 6.0

Granite 5.3

Basalt 4.8

Limestone 3.8

MAP 1053/MKAQ 1053 4

Table 1.3 Allowable Steel Working Stress

Indierct tensile strength of concrete at

28 days (psi)

Reinforcing bar size

No. 4 No.5 No.6

300 or less 65000 57000 54000

400 67000 60000 55000

500 67000 61000 56000

600 67000 63000 58000

700 67000 65000 59000

800 or greater 67000 67000 60000

Table 1.4 Recommended friction factors

Types of Material Beneath Slab Friction factor (f)

Surface treatment 2.2

Lime stabilization 1.8

Asphalt stabilization 1.8

Cement stabilization 1.8

River gravel 1.5

Crushed stone 1.5

Sandstone 1.2

Natural subgrade 0.9

Table 1.5 Yield strength and allowable stress for steel

Type and grade of steel Yield strength

(psi)

Allowable stress (psi)

Billet steel, intermediate grade 40 000 27 000

Rail steel or hard grade of billet

steel

50 000 33 000

Rail steel, special grade 60 000 40 000

Billet steel, 60 000 psi

miminum yield

60 000 40 000

Cold drawn wire (smooth) 65 000 43 000

Cold drawn wire (deformed) 70 000 46 000

MAP 1053/MKAQ 1053 5

Table 1.6 Weights and dimensions of standard reinforcing bars

MAP 1053/MKAQ 1053 6

DESIGN INPUTS

Input Variable Value Input variable Value

Reinforcing

Bar/Wire Diameter

Ф (inches)

Thermal

Coefficient Ratio

αs/αc (in./in.)

Concrete Shrinkage

, Z (in./in.)

Design

Temperature Drop

DTD (˚F)

Concrete Tensile

Strength, ft (psi)

Wheel Load Stress

σw (psi)

DESIGN CRITERIA AND REQUIRED STEEL PERCENTAGE

Crack Spacing,

x (feet)

Allowable

rack Width ,

CWmax

(inches)

Allowable

Steel Stress,

(σs) max (ksi)

Design steel

range

Value of

Limiting

Criteria

Minimum

Required Steel

Percentage

Maximum

Allowable Steel

Percentage

Table 1.7 for Q1b

Worksheet for Longitudinal Reinformecement Design

Note: Please return this figure along with your answer book

MAP 1053/MKAQ 1053 7

Figure 1.1 for Q1b: Percent steel to satisfy crack spacing criterion

MAP 1053/MKAQ 1053 8

:

Figure 1.2 for Q1b: Percent steel to satisfy crack width criterion

MAP 1053/MKAQ 1053 9

Figure 1.3 for Q1b: Percent steel to satisfy steel stress criterion

MAP 1053/MKAQ 1053 10

Q2. (a) AASHTO 1993 Design Guide used an empirical design approach in

designing the thickness of structural layer. Recent development, ATJ 5/85

(2013 revision) method was developed based on mechanistic-empirical

design approach. By using this two types of design method (AASHTO

1993 and ATJ 5/85 (2013)) as an example, explain in details the

difference between empirical and mechanistic-empirical approach.

(5 marks)

(b) Determine the required structural thickness for a dual carriageway Rural

Arterial using AASHTO 1993 Design Guide. The following data were

given.

Analysis period of 20 years

ESAL for the first = 2 million

Traffic growth rate of 4% per annum

Directional spilt 60/40

Lane distribution factor of 80%

Standard deviation of 0.45

Initial serviceability of 4.5

Terminal serviceability of 2.5

Soil will be exposed to six months of dry and 6 months of wet season.

Both base and subbase materials are of good drainage quality and percent

of pavement structure exposed to moisture levels approaching saturation

is 10%.

(20 marks)

(25 marks)

Growth factor= (1+r)n-1

r

∆PSI= po - pt

w18 = DD x DL x ŵ18

SN=a1D1 + a2D2m2 + a3D3m3

D1* ≥ SN1/a1

SN1* = a1D1 * ≥ SN1

D2*≥ (SN2 – SN1*)/(a2m2)

SN1* + SN2 * ≥ SN2

D3*≥ (SN3 – (SN1* + SN2* ))/ (a3m3)

μf = 1.18 x 108 x MR-2.32

MAP 1053/MKAQ 1053 11

Table 2.1 Suggested Levels of Reliability for Various

Functional Classifications

Functional Classification Recommended Level of

Reliability

Urban Rural

Interstate and other Freeways 85-99.9 80-99.9

Principle Arterials 80-99 75-95

Collectors 80-95 75-95

Local 50-80 50-80

Layers Moduli:

Asphalt Concrete : EAC= 400,000 psi

Granular Base: EBS= 28,000 psi

Granular Subbase: ESB= 13,000 psi

a1 = 0.41

a2 = 0.294(log10 EBS) – 0.977

a3 = 0.227 (log10ESB) – 0.839

Table 2.2 Recommended mi values for untreated Base and Subbase

Percent of Time Pavement Structure is Exposed to Moisture Levels

Approaching Saturation

Quality of

Drainage

< 1% 1-5% 5-25% >25%

Excellent 1.40-1.35 1.35-1.30 1.30-1.20 1.20

Good 1.35-1.25 1.25-1.15 1.15-.100 1.00

Fair 1.25-1.15 1.15-1.05 1.05-0.80 0.80

Poor 1.15-1.05 1.05-0.80 0.80-0.60 0.60

Very Poor 1.05-0.95 0.95-0.75 0.75-0.40 0.40

Table 2.3 Effective Roadbed Soil Resilient Modulus

Roadbed Moisture Condition Roadbed Soil Resilient Modulus

(psi)

Wet 5000

Dry 6500

Spring- Thaw 4000

Frozen 20000

MAP 1053/MKAQ 1053 12

Figure 2.1 for Q2b

MAP 1053/MKAQ 1053 13

PART B

Q3. A new big township is under construction and a monthly news bulletin is

distributed monthly to everyone involved in the management and the

construction of the township. An article on a certain construction aspect is

highlighted every month. The article to be included in the next month’s

bulletin is on road construction. The pavement for the roads in the town

are of two types; asphalt pavement and concrete block pavement.

Write a draft for the article to explain the various layers and components

of the pavements. Good construction practices and various innovations

should also be included to provide for an interesting and purposeful

reading.

(25 marks)

Q4. (a) A full cut section of a road has failed during a raining season. The cut

slopes which consist of simply constructed long and steep slopes without

proper drainages and without proper erosion control have collapsed. The

pavement has also failed because of water infiltration into the subgrade.

Suggest how a reconstruction of this failed section should be done to

provide for a permanent solution. The reconstruction should consist of the

required drainages; both surface and subsurface and erosion control

measures.

(16 marks)

(b) The use of rocks and large stones is a common feature in road

construction. Differentiate between a rip rap, a stone mattress and a

gabion in terms of their features and contributions.

(9 marks)

(25 marks)