Traditionally, the resilient modulus values obtained from repeated unconfined or triaxial compression tests are used as the elastic modulus of granular layers in structural analysis of flexible pavements. Sometimes the resilient modulus of granular materials are estimated from known California bearing ratios (CBR) or stabilometer resistance (R) values by simple regression equations. On the other hand, it is well known that stress-strain relation for unbound granular materials is nonlinear and the resilient modulus increases with the increase in stress intensity.
There exist several models for stress dependent nonlinear behavior of unbound granular materials. These models are incorporated into elastic layered analysis by applying a method of successive approximations in order to get more realistic pavement responses. Kenlayer is a popular computer program incorporating nonlinear behavior of granular materials in elastic layered system. In this computer program, the resilient modulus of granular materials are varied in vertical direction only, without considering variations in radial direction.
In this study, simplest model namely K-Q model for stress dependency of granular layer is applied in structural analysis of flexible pavements. This model is adopted for use in finite element analysis carried by SAP90 software. Analyses are performed over 24 different three-layered pavement structures by changing asphaltic concrete modulus values, granular base thicknesses, base materials and subgrade modulus values. Critical pavement responses namely tensile strains at the bottom of asphaltic surface layers and compressive strains on top of subgrade are obtained for each pavement by linear layered elastic, nonlinear layered elastic and nonlinear finite element solutions. The pavement lives are calculated by using selected performance equations. The results of layered systems and finite element solutions are compared. It is observed that, results obtained from finite element model and linear elastic solutions differ considerably.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/2/12605320/index.pdf |
| Date | 01 September 2004 |
| Creators | Karagoz, Cem |
| Contributors | Acar, Osman Soner |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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