| 1. |
- Said, Safwat, 1951-, et al.
(författare)
-
Prediction of rutting in asphalt concrete pavements : the PEDRO model
- 2020
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Flexible pavement rutting due to permanent deformation accumulation in asphalt layers is one of the most common modes of road failures. In addition to high maintenance costs, rutting is a major concern for traffic safety, as the rut growth increases the risk for hydroplaning and difficulties in vehicle steering. In this context, accurate methodologies for pavement rutting performance prediction are crucial for decision support in pavement design and rehabilitation. More rational rutting performance models are needed to enable the implementation of new and more sustainable and environmentally friendly asphalt materials as well as to evaluate the impact of high capacity traffic (HCT) vehicle types on bituminous layers.The main goal of this work is to implement and disseminate an asphalt rutting performance prediction tool called PEDRO (PErmanent Deformation of asphalt concrete layers for ROads). It focuses solely on the permanent deformation of asphalt concrete materials in the pavement structure. The PEDRO tool is a viscoelastic model for the calculation of permanent vertical strain under moving wheel loads over a viscoelastic half-space. The analysis is performed for the entire rutting zone and the permanent deformation of each layer or sub-layer, depending on its location in the pavement structure, is then integrated over the whole asphalt concrete depth.
|
|
| 2. |
- Hu, Min, 1979-, et al.
(författare)
-
Assessment of a Three-Dimensional Fiber Orientation Model for Timber
- 2016
-
Ingår i: Wood and Fiber Science. - 0735-6161. ; 48:4, s. 271-290
-
Tidskriftsartikel (refereegranskat)abstract
- Wood is an orthotropic material with very different properties along and across fibers, and every board has its own pattern of knots and fiber deviations. Therefore, detailed knowledge of the three-dimensional (3D) fiber orientation of individual boards would enable more accurate assessment of properties such as stiffness, strength, and shape stability. This paper presents a method for modeling 3D fiber orientation of side boards of Norway spruce. The method is based on dot laser scanning and utilization of the tracheid effect, and it is verified by a comparison between strain fields calculated on the basis of the fiber orientation model and corresponding strains determined using digital image correlation (DIC) technique. By means of the method, it is possible to identify knots and to reproduce the fiber orientation in clear wood in the vicinity of knots. Fiber orientation models of side boards including traversing edge knots were established and integrated in finite element models of boards used for simulation of four-point bending tests. The same boards were also tested in laboratory and displacement fields of the wide faces were recorded at different load levels using DIC technique. Comparisons of strain fields from measurements and simulations showed close agreement, regarding both strain patterns and strain levels. Local strain concentrations caused by very small defects were detected using the models and also found from the laboratory test results. The modeling approach may be used both to achieve improved accuracy of existing machine strength grading methods and, after further development, also for more advanced analysis of eg crack propagation and strength of timber.
|
|
