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Keywords: flexible pavement, pavement modelling, multi-layer method, finite element method, axi-symmetric model, 3D model.

Summary

As with any engineering structure, to model a flexible pavement for analysis purposes, one has to know the calculation method and the structural model that best represents reality in terms of geometry and loading. However in pavement design, the pavement analysis must be not only sufficiently accurate but also expeditious.

In this paper, different calculation methods, the first one based on the multi-layer method and the second one on the finite element method, and different structural models (axi-symmetric and 3D models) are considered in the calculation of three pavement structures, in order to establish the main differences between calculations. The selected pavement structures are referred to in the Portuguese Pavement Catalogue [1] for the traffic class corresponding to 500-800 heavy vehicles a day and differ with regard to geometry and pavement materials.

In the numerical study, several software programmes such as ALIZE, EVERSTRESS, MICHPAVE and DIANA were used. The first two, are based in the multi-layer theory while MICHPAVE and DIANA, or the finite element method. As far as the structural models, only the DIANA package allows the consideration of 3D models. It must also be condidered that the allowed load configuration for each program is different and those differences may influence the numerical results.

In the paper the actual pavement methodology is considered that is mechanistic-empirical in almost all European countries. This methodology essentially consists of two phases: firstly evaluation of the pavement response (deflections, strains and stresses) due to loads and environment conditions and secondly calculation of the admissible standard axle loads, considering the pavement performance. The performance models are based on damage criteria; in Portugal, these criteria are: fatigue cracking of the bituminous layer and permanent deformation of the subgrade.

The main conclusions study presented in the paper are: (1) the interface condition between pavement layers had influence in the structural behaviour of the pavement; (2) different finite element software programmes with the same structural model (axi-symmetric) provided different results; (3) the software programmes based in the multi-layer theory provided (for the analysed pavements) lower results than those obtained with the finite element calculation; (4) the axi-symmetric model (more conservative) can be still applied for pavement design, as a result of to its simplicity.

References

1: JAE "Manual de Concepção de Pavimentos para a Rede Rodoviária Nacional", Junta Autónoma das Estradas (JAE), Almada. 1995. (in Portuguese)

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 80 PROCEEDINGS OF THE FOURTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: B.H.V. Topping and C.A. Mota Soares Paper 130 The Influence of the Structural Calculation Method and the Model on Pavement Design C. Vale and A. Sousa-Melo Department of Civil Engineering, University of Porto, Portugal doi:10.4203/ccp.80.130 purchase the full-text of this paper Full Bibliographic Reference for this paper C. Vale, A. Sousa-Melo, "The Influence of the Structural Calculation Method and the Model on Pavement Design", in B.H.V. Topping, C.A. Mota Soares, (Editors), "Proceedings of the Fourth International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 130, 2004. doi:10.4203/ccp.80.130 Keywords: flexible pavement, pavement modelling, multi-layer method, finite element method, axi-symmetric model, 3D model. Summary As with any engineering structure, to model a flexible pavement for analysis purposes, one has to know the calculation method and the structural model that best represents reality in terms of geometry and loading. However in pavement design, the pavement analysis must be not only sufficiently accurate but also expeditious. In this paper, different calculation methods, the first one based on the multi-layer method and the second one on the finite element method, and different structural models (axi-symmetric and 3D models) are considered in the calculation of three pavement structures, in order to establish the main differences between calculations. The selected pavement structures are referred to in the Portuguese Pavement Catalogue [1] for the traffic class corresponding to 500-800 heavy vehicles a day and differ with regard to geometry and pavement materials. In the numerical study, several software programmes such as ALIZE, EVERSTRESS, MICHPAVE and DIANA were used. The first two, are based in the multi-layer theory while MICHPAVE and DIANA, or the finite element method. As far as the structural models, only the DIANA package allows the consideration of 3D models. It must also be condidered that the allowed load configuration for each program is different and those differences may influence the numerical results. In the paper the actual pavement methodology is considered that is mechanistic-empirical in almost all European countries. This methodology essentially consists of two phases: firstly evaluation of the pavement response (deflections, strains and stresses) due to loads and environment conditions and secondly calculation of the admissible standard axle loads, considering the pavement performance. The performance models are based on damage criteria; in Portugal, these criteria are: fatigue cracking of the bituminous layer and permanent deformation of the subgrade. The main conclusions study presented in the paper are: (1) the interface condition between pavement layers had influence in the structural behaviour of the pavement; (2) different finite element software programmes with the same structural model (axi-symmetric) provided different results; (3) the software programmes based in the multi-layer theory provided (for the analysed pavements) lower results than those obtained with the finite element calculation; (4) the axi-symmetric model (more conservative) can be still applied for pavement design, as a result of to its simplicity. References 1 JAE "Manual de Concepção de Pavimentos para a Rede Rodoviária Nacional", Junta Autónoma das Estradas (JAE), Almada. 1995. (in Portuguese) purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £95 +P&P)
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