Projekt BVFF - publicerade   BVFF nummer:  2015-017 Projekttitel  Mechanistic empirical based pavement design and performance prediction framework – Further development and implementation Projektledare/Kontaktperson  Sigurdur Erlingsson Telefon  013 204123 / 0709 174219 Utförarorganisation  VTI Medutförare  Ph.D. students ??, KTH? Bakgrund  Current pavement design methods and procedures are based on empirical approach based on the AASHO road experiment that was carried out in late 1950´s and early 1960´s. Since then heavy traffic volume has increased substantially. Furthermore was the experiment limited to one type of subgrade in all sections and to a limited number of different base courses and surfacing materials. These limitations along with other factors such as developments in construction techniques, improved materials, different sub-drainage conditions, higher axle loadings and tyre pressures and the long-term effects of climate on pavements and ageing make the empirical design approach obscure and difficult to apply in new situations. They cannot neither predict functional nor structural degradation with time. It is furthers difficult to apply the method for unconventional or novel materials. The current Swedish pavement design method PMS Objekt is partly based on this approach. Mechanistic-based pavement design methods are being developed in different countries in the world. The main objective of these methods is to adequately predict functional and structural conditions of roads over time. These methods differs for different countries but they are all based on application of the principles of engineering mechanics to evaluate the response of pavement structures to traffic loading and thereafter carry out distress prediction (or how performance changes with time). The methods are referred to as M-E methods as they calculate the response of the pavement mechanistically and thereafter relate the response in an empirical way to degradation. The empirical step is further based on field or laboratory experimental results where real behaviour has been simulated (note that it is important that this is done locally). This approach ensure a fundamental understanding of how the pavement structure responds to a certain action or loading conditions and introduces flexibility of dealing with new situations such as new pavement materials and loading situations. At VTI, in the Ph.D. project Funktionell vägdimensionering – Tillståndsutveckling av vägar that finished in 2014 a new M-E procedure was developed. At the moment the procedure exists as a relatively simple computer code, ERAPave Perform that can predict degradation as a function of time. The current version of the code concentrates on simulating rutting development but predicts fatigue cracking as well. Limited calibration has been carried out. Further is the climate model simple and needs improvements. In the projects Klimatets inverkan på vägdimensionering and förstärkningsåtgärder av tjälskadade vägar (two Ph.D. projects) that will finish in the first half of 2015 a new knowledge regarding unbound material and subgrades moisture dependency has been developed. This could be implemented into the ERAPave code. Sammanfattning  Mechanistic-based pavement design methods are being developed in different countries in the world. The main objective of these methods is to adequately predict functional and structural conditions of roads over time. These methods differs for different countries but they are all based on application of the principles of engineering mechanics to evaluate the response of pavement structures to traffic loading and thereafter carry out distress prediction (or how performance changes with time). At VTI a new mechanistic pavement design procedure has been developed. At the moment the procedure is a relatively simple computer code, ERAPave Perform that can predict degradation as a function of time. The current version of the code concentrates on simulating rutting development but predicts fatigue cracking as well. Limited calibration has been carried out. Further is the climate model simple and needs improvements. The objectives of this project is to: a) enhance the ERAPave perform code so it can in a realistic way predict rutting and fatigue cracking as a function of time (this includes i.e. improved user interface, use of local ambient climate conditions, incorporate new temperature and moisture dependent material models); b) introduce new distress modes such as low temperature cracking and roughness (IRI); c) validate and calibrate the code against known performances from HVS test results and full-scale performance tests (the Svappavaara road tests and maybe LTPP sections) and implement into the code. The end results will be a new mechanistic based design method/tool (software) for pavement design and performance predictions for Swedish (Nordic?) conditions. Förväntat resultat  1) Increased knowledge regarding a new framework for mechanistic pavement design and performance prediction. The framework can be used to study consequences for pavement live due to different scenarios such as changes in axle loads, tyre pressures or configurations, climate changes, using local inferior materials etc. 2) A new M-E based design tool (software) for pavement design and performance predictions based on Swedish (Nordic?) calibration and validation. Plan för resultatspridning och implementering  This project is divided into two parts regarding dissemination and implementation: Implementation Part a) and c) (see description below) is to a large extent implementation of a relatively new concept/knowledge into a new computer tool in form of a software for pavement design and performance predictions. Further will the software be documented to assist new user to use the code as a program manual. Further, will the code be described in a scientific publication. Dissemination Part b) consist of a Ph.D. study and includes therefore new research results that will be published in a thesis and in peer review journals. Further will all results from a), b) and c) be disseminated through seminars and workshops like transportforum etc. Tidsramar  The project is defined as a four year project, starting in June 2015 and ending in 2018.