MacPlaza1 City-CS 960627- 07-01-96 A11~12 I~~
VILBI~ & ASSOCIAT S, NC.
CIVIL. & STRUCTURAL ENGINEERS
GEOMATICS 1 SURVEYORS
June 27, 1996
City of Coppell
P. O. Box 478
Coppell, Texas 75019
~;7 ~ /I ~ ~ ~ ;~ ? 1 .Project: City Garag
~ `7" ~/ VAi Projec No. 4
~"1 Mach: thur lava
VAi Projec No. 4
RE: Request for V ante
Atm.: Ken Griffin
As we discussed, we request a variance on the paving requr ement for the above
referenced projects. Please refer to the letter from Reed Engine ring roup dated June
13, 1996.
Please call if you have any questions
YILBIG ~ASSOCIA , I C.
R
David A: Vilbig, P.E. R.P. S.'
President
c: Robert Hodges - HCB Contractors
~ittacftmeni
c: l mso~ce l wi mvo~d l ci tygarg 1489-31 variance. doc/dc
10] 32 MONROE DRIVE" DALLAS, TEXAS 75229 (214) 352 7333
• FAX (214) 352-0999
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cOTECH^ICAL AND ( G W Q LI PL
VIkONME TAL CONSULTANTS ~
June 13, 1996
Project Igo. 2482
Ms. Heidi Fischer
Vilbig & Associates, Inc.
10132 Monroe Drive
Dallas, Texas 75229
Re: lvlacArthur Plaza
MacArthur Drive
ing,~exas
--~_
Dear Ms. Fischer:
Submitted here are reconuriendations regarding equivalent pavement ectiaat for the
referenced project. Two pavement sections were provided; afive-inc secti n for light-
duty, and asix-inch section for truck tragic. I3oth sections were desi ned fo a non
stabilized subgrade.
A five inch, 3,000 pounds per square inch (psi) concrete pavement o er a no -stabili
subgrade provides an unlimited number of repetitions far car and ligli truck rafl'ic.
Additional analysis of various sections ryas therefore not performed.
The standard pavement in areas subject to truck traffic w,as considere to co sist of 6-
inch thick, 3,000-psi compressive strength concrete over d inches of 1 me-st ilized
subgrade. The analysis has consisted of determining the number ofd ily rep titions of an
equivalent 18-kip axle load and a 20-year design life. The analysis fol awed racedures
from the American Association of State Highway Officials (AASHO) Interi G--ui.de.
Three pavement sections have been analyzed; the referenced "standar " pay ment
consisting of 6 inches of 3,000-psi concrete over a lime stabilized sub rade, inches of
4,000-psi concrete, and 7 inches of 3,000-psi concrete. The latter tw secti ns were
analyzed considering natural or unstabilized subgrade.
The first factor to be derived consists of the rnodul~ts of subgrade rea tibn, ,for both
the natural subgrade and on tap of a six-inch layer of lime stabilized oil. A slue of 100
pounds per cubic inch (pci) is recommended for the natural subgrade Gorr lations
developed by the Federal Aviation Administration .(FAA) for cement stabili ed subgrade
provide an effective k value, considering a 6-inch stabilized subgrade of 210 pci. Two
hundred pci was used for the analysis.
Grntrrbnirrtl Engixrrring
Envirnr:nvrnrlel GeruLdti>tg
I
Conrcrucriar, MnrLwrs6 Trrnn,
242A STUTZ DR. SUITE 400 DALLAS, TX 75235 *EL i214) 350 560U ~ FA;t [214P 350 0019
1.1. _ 7t_~ ~I _._~j-I`1 Y'.: t_L! LI`9~.=1~-..iL r:1(~41~ ~- 4 .._~l_1-i%l Il~_i ---
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`Vilbig & Associates, Inc.
Project. No. 2482
June 13, 196
Pa$e 2
The second factor required to evaluate the sections consists of the
concrete. This value is equal to 0.75 percent of the modulus of ru
between the compressive strength and iVIR indicate that the MR c~
the square root of the compressive strength. This analysis results
425 psi for the 3,000- and 4,600-psi concrete, respectively.
Application of the A.ASHQ nomograph results in the derived equi
below,
Pavement Sec i n
6 °', 3,000 psi concrete
over 6" lime
6'", 4000 psi Concrete
over natural subgrade
7", ;,000 psi concrete
over natural subgrade
As discussed above, the allowable daily traffic is based on a 2
orki stress of the
ire ( }. Correlations
be a proximated as 9 times
a wo king stress o£370 and
g_~p axle loads shown
deign life.
Based on this analysis, b inches of 4,000-psi concrete over a no -lime- abilized subgrade is the.
equivalent of 6 inches of 3,000-psi concrete aver 6 inches of lim -stabi ized subgrade. As an
alternative, 7 inches of 3,000-psi concrete over a non~lime stabi ized s gtade provided
approximately 7S percent greater traffic than the required section.
We trust this inforrlation is sufficient for your use. If any quest~ons
Sincerely,
READ P'.NGINE RING C7RCU//I",1NC. .*~`~ OF ~~~ ~
t: ~ ~
Ronald F. Reed, P.E. ,, po1!AI.D ~; ~~;~~ ...
~„~ ......x.9174 .~
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X10
do not hesitate to call.
copies submitted: (1}