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F-1 Appendix F. Sensitivity Analysis of Modulus of Subgrade Reaction Model Sensitivity analysis was performed on the Artificial Neuron Network (ANN) model for modulus of subgrade reaction (modified k-value) to evaluate the effect of various input variables on the relationship between slab-base degree of bonding and modified k-value. The input variables include the thickness of slab and base course, modulus of slab, base course, and subgrade. Table F.1 lists the change of various input values for sensitivity analysis. Figure F.1 presents the effect of various input variables on the relationship between degree of bonding and modified k-value. Generally, the modified k-value increases with the greater the degree of bonding. The thicker PCC slab or base course can help improve the value of modulus of subgrade reaction. Likewise, the larger modulus of base layer or subgrade is the higher modified k-value is. Additionally, the higher modulus of PCC slab enhances the modified k-value but after a threshold, the modified k-value reverses the order. Table F.1. Change of Various Input Values for Sensitivity Analysis. Input Variable Change of Input Values Slab thickness, in 4, 8, 12 Base thickness, in 2, 6, 10 Slab modulus, psi 1450380, 2900760, 5801520, 8702280 Base modulus, psi 4351, 23206, 46412, 62366, 92824 Subgrade modulus, psi 5076, 20305, 40610 Degree of bonding 0, 0.3, 0.6, 1 (a) Effect of slab thickness
F-2 (b) Effect of base thickness (c) Effect of slab modulus
F-3 (d) Effect of base modulus (e) Effect of subgrade modulus Figure F.1. Effect of Various Input Variables on Relationship between Degree of Bonding and Modified k-value.