The State DOT is about to begin the reconstruction of SR535. Because it runs through Mythaca County, our staff wants to make sure that the pavement design is adequate for the traffic that is expected to use SR535 during the next 20 years.

Note: As in previous HWs, you may submit this HW as a member of a group formed by the mutual consent of no more than four CE361 students. If this HW is submitted by a group, the top sheet of the material submitted must bear the signature of each group member. Each member of a group that submits HW7 in this way will receive the same grade.

1. Review of Course Notes Chapter 8 (Highway Pavement Design).
• (2 points) Is the general level of the presentation in Chapter 8 too simple, too difficult, or about right for you?
• (3 points) Which sections were the most helpful in understanding the material? Which sections were confusing or otherwise inadequate? Which concepts need to be presented better? Specific comments, please.


2. (15 points) ESAL Calculations. Axle frequency data for a "typical week" in the design lane of SR535 are contained in Table 1. The expected annual growth rate for 2K and 6K axles is 2.2 percent. For the heavier axles in Table 1, the growth rate is 2.9 percent. Complete the entries in Table 1 and compute the 20-year Total Design Life ESALs for the design lane on SR535. Use the fourth-power Equations 8.1 and 8.2 to calculate the individual axle ESALs that are called Load Equivalency Factors (LEF) in Table 1. Note: Regardless of the value you compute in this problem, use Total Design Life ESALs = 31,300,000 in the problems below.
   
   
3. (20 points) Rigid Pavement Design. Determine the slab thickness for the design lane on SR535 using the data listed in Table 2 below and the AASHTO rigid pavement design method described in CNotes Section 8.15. Use a copy of "Materials" and "Highway" portions of the rigid pavement design chart in CNotes Figures 8.22 and 8.23 to do your design. Submit these copies with your assignment.
   
   

   Table 2. Data for Rigid Pavement Design

   C(d) = 1.0	k = 97 pci	R = 95%
   E(c) = 5.7 x 10**6	p(i) or PSI(o) = 4.2	S'(c) = 682 psi
   J = 3.2	p(t) or PSI(t) = 2.5	S(o) = 0.35

   
   
4. (20 points) Flexible Pavement Design. Determine the Design Structural Numbers SN(3), SN(2), and SN(1) for the design lane of SR535. Use the data listed in Tables 3 and 4, and the AASHTO flexible pavement design method described in CNotes Section 8.10. Use an enlarged copy of the design chart in CNotes Figure 8.17 and submit it with your assignment. Do not carry out the layer design (CNotes Section 7.10) until the next problem.
   
   

   Table 3. Data for Flexible Pavement Design

   MR = 5500 for subgrade	p(i) = 4.2	p(t) = 2.5
   R = 90%	S(0) = 0.30

   
   
5. Layer Design and Cost Analysis. Determine the least cost flexible pavement design per lane mile in the design lane on SR535. The lane is 12 feet wide. The subgrade soil extends ten feet below the surface, so that drainage is not a factor in the design, i.e., m(i) = 1.0. Table 4 below indicates the materials that you must use. This problem is best done by setting up a spreadsheet and determining the costs per lane mile for various layer designs. Such a spreadsheet can be seen here. Your design alternatives (and their associated costs) should include ...
   • A. (10 points) A full-depth Hot Mix Asphalt Concrete pavement that uses a Design Structural Number of 5.9, regardless of your answer to Problem 3 above. Use the spreadsheet cited above to calculate the cost of this design.
   • B. (10 points) A layer design that follows the steps in CNotes Section 8.10, as demonstrated in class Wed. 31 October 2001. Regardless of your answer to Problem 3 above, use SN(1) = 2.6, SN(2) = 3.8, and SN(3) = 5.9 as your Design Structural Numbers. What is the cost of this design?
   • C. (15 points) An easy-to-follow search for the values of D*(1), D*(2), and D*(3) that are consistent with the weighted SN equation (CNotes Equation 8.5), obey the layer thickness restrictions in CNotes Table 8.8, and produce the minimum cost flexible pavement layer design. Use the spreadsheet cited above to calculate the cost of this design.
   • D. (5 points) Which of your layer designs is the most economical? Show your analyses and state your conclusions clearly.
   
   

   Table 4. Data for Layer Design and Cost Analysis

   Material	Layer	a(i)	M(R)	Specific Gravity	Unit Cost (delivered)
   Hot Asphaltic Concrete	Top/Wearing	0.30	---	2.56	$67.11/Ton
   Emulsion/aggregate-bituminous	Base	0.13	28,000	2.70	$15.79/Ton
   Coarse Aggregate	Subbase	0.11	16,000	2.68	$9.11/Ton

   
   Note 4a: The subgrade soil has MR = 5500 ksi.
   Note 4b: Excavation costs are $6.48 per cubic yard of soil displaced.
   
   
6. A problem on Pavement Management Systems will not be added.