De sign of Pavement Structures
<br /> a
<br /> Once a design structural number is se!ccted,it is up to High 7W.0W to 1.000,000
<br /> the user to identify an appropriate combination of Medium 400,000 to (A0,0M
<br /> flexible pavement laver thicknesses which will provide Low 50.000 to 300,000
<br /> the eesircd load-carrvirg capacity. T111s may be ac-
<br /> cc npk:shed using the entera for laver coefficients(a,- (9) The levels of roadbed soil quality and eor-
<br /> vR;ues) presented in Section 2.3.5 and the general responding ranges of effective modulus of
<br /> equation for structural number, subgrade reaction (k-value) are:
<br /> SN =aI Dl +::D2+a3D3 Very Good greater than 550 pci
<br /> Good 400 to 550 pci
<br /> at, a-,a, = layer ciefficient for surface, base, Fair 250 to 350 pci
<br /> and subbase course materials,respec- Poor 150 to 250 pei
<br /> tively, and Very Poor less than 150 pci
<br /> Dt, D:, D3 thickness(in inches)of surface, base, It should bz noted that althou;h the minimum slab
<br /> ar_d subbase course, respective'.y' thickness shown is 5 inches,the user should consider
<br /> the use of a thicker slab since an overloaded truck may,
<br /> in some cases, severely damage thin slab paverientL
<br /> 4.:2 Rigid Pavement Design Catalog ;
<br /> Tames a.3 and '.9 prnment the cataiog of nc:Land 4.2.3 g e ate- n.*farr Road DeSip r'222101
<br /> comer.aaveY.•-... �:i.icz:.rsses t. :�t�v*e u:e�:,r
<br /> :Wore
<br /> Tahl:4_iUpzea Isarara ogoiag_r..2z1eb=1acrr
<br /> appzoat:h it n_^t goss:i ;.T ale 4_8 : *=cinesses that =y be u-,,csa:sr the d=iga.,of low-
<br /> �asea a a 50:==T rZZILI diry Ie'rei...:A 1 ab3*z 4.9 i-; valuI e;czd:3 whrn I.". moredf.aiizddesig,,,m':.p-roach
<br /> bast on_l 15 _--ri.:: I le mL The a-wuzipuoAs tnae cn:
<br /> is not possible_ Tnz t,hialmensses shown are based on
<br /> W these c=s:^ cam ;gs are as follows spc�:ic.at des of 38-kip E 7A applications 8Z traffic
<br /> (1) Jc.niec. ;- -iforr_d or ur-cin:ore;�d)concrete l vels: _ --
<br /> pavemcat (- =3—^). High 601X-00 to 100,00-0
<br /> (2) Slab thicknc_s design recommendations Medium 30,000 60,000
<br /> 1
<br /> apply to all su. U.S. climatic matic regions. _ 10,000 30,000
<br /> (_) Subbase is 6 inches of high quality granular One other assumption inherent in these base thick-
<br /> subbase (For •-ery good subgrade and low ness recommendations is that the effective resilient
<br /> traf:ic, this layer may be )mmittcd). modulus of the aggregate base material is 30,000 psi,
<br /> regardless of the quality of the roadbed soil-This w.lue
<br /> (4) Mean PCC modulus of rupture (Sc) is 600 should be used as input to the nomograph in Figure 4.5
<br /> to convert a portion of the aggregate base thickness to
<br /> Fsi' an equivalent thickness of subbase material with an
<br /> (5) 'glean PCC elastic modulus(E_)is 5,C00,000 intermediate modulus value between the base and
<br /> psi
<br /> roadbed soil.
<br /> .
<br /> (6) T:Icre are no tied concrete shoulders (or
<br /> curbs) required.
<br /> I D-ra,nagc(moisture)con,,' are fair(C,
<br /> = lC .
<br /> �! IS-: in ESAL ,raf,;,:
<br />
|