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Pages 137-154

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From page 137...
... B-1 APPENDIX B DEVELOPMENT OF ALTERNATIVE M-E JPCP CRACKING MODEL TO INCORPORATE SLAB-BASE EFFECTS A PCC/base interface model adapted in this study is the simplified friction model that is based on the following assumptions (Khazanovich and Gotlif 2002)
From page 138...
... B-2 of lean concrete base material, the effective thickness heff of the equivalent slab is 9.22 inches if an unbonded interface is assumed and 11.82 inches if a bonded interface is assumed. Figure B-1.
From page 139...
... B-3 Ξ›βˆ— = Ξ› 𝐸1β„Ž1 + 𝐸2β„Ž2 8 The use of this parameter for friction illustrates the influence that a simplified friction (partial bond) model can have on the analysis of slab-base behavior in rigid pavement systems.
From page 140...
... B-4 ο‚· The coefficient of friction Ξ› is not a material parameter. Furthermore, its value depends on layer thicknesses and material properties.
From page 141...
... B-5 ο‚· TNL is the nonlinear top or bottom surface temperature; and ο‚· TNLο‚±a is the nonlinear surface temperature at characteristic length, a, away from the top or bottom surface of the slab. Thus Table B-1 illustrates the sensitivity of the structure response and damage parameters to the aggregate input parameters in the original JPCP transverse cracking model and in the modified cracking model to be discussed in the sections below.
From page 142...
... B-6 treatment of the use of hourly pavement data to develop monthly linear temperature difference tables. Previously, under the procedure developed in NCHRP 1-37A and adopted for the AASHTO M-E design procedure, the thermal linearization was conducted for bonded and unbonded interfaces for the 12 calendar months in a representative design year (meaning the single year typified any given year in the entire design life)
From page 143...
... B-7 B.3.1. Calculate the Equivalent Slab Thickness Compute equivalent slab thickness using Equation 4.
From page 144...
... B-8 B.3.4. Calculate Effective Temperature Differential The equivalent temperature difference should produce the same effective bending moment as original temperature distribution.
From page 145...
... B-9 B.3.7. Determine effective slab thickness The AASHTO M-E design procedure define the effective slab thickness is a thickness of the slab with the modulus of elasticity and Possion's ratio equal to 4,000,000 psi and 0.15, respectively, resting on the Winkler foundation with the coefficient of subgrade reaction equal to 100 psi/in, and having the same radius of relative stiffness as the equivalent slab.
From page 148...
... B-12 B.3.16. Find bending PCC stresses πœŽπ‘’π‘“π‘“(πœ‰)
From page 149...
... B-13 For bottom-up damage accumulation, an 18-kip single axle load is placed at the mid-slab edge, where it will produce the maximum stress, as shown in Figure B-4 on the left. For top-down damage accumulation, a 12-kip single axle load and a 34-kip tandem axle load with a medium wheel base is placed at the critical loading location, as shown in Figure B-4 on the right.
From page 150...
... B-14 Table B-2. Example of frequency distribution tables providing probability of a given combination of TL and TNL for a given hour of a specific calendar month Table B-3.
From page 151...
... B-15 B.5. Major modifications to the damage calculation in the modified JPCP transverse cracking prediction model This step involves the calculation of accumulated top-down and bottom-up damage in the slab given the structure response (i.e.
From page 152...
... B-16 B.5.1. Energy of elastic deformation strength criteria The following attempts to develop a criteria for fracture initiation in a quasi-brittle material under a non-uniform uniaxial tensile stress field.
From page 153...
... B-17 By equating the expressions for energy in Equations 32 and 34, one obtains an expression for the modulus of rupture, 𝑀𝑅, i.e the value of 𝜎0 at which the beam fails. 𝑀𝑅, also referred to as the flexural strength, is 𝑀𝑅 = 𝑓𝑑 √1 βˆ’ 2 π‘Ž β„Ž + 4 3 ( π‘Ž β„Ž )
From page 154...
... B-18 B.6. Transverse cracking prediction in the modified model (outputs)

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