ENHANCEMENT OF FATIGUE LIFE FOR PAVEMENT STRUCTURE

number: 
3356
English
department: 
Degree: 
Imprint: 
Engineering
Author: 
Methal Qudori Ali
Supervisor: 
Dr. Alaa Hussein Abed
Dr. Nabil Mohammed Ali Hussein
year: 
2014

The rehabilitation of an existing cracked pavement made of asphalt can be simply done by the installation of new asphalt layers. Due to external forces from traffic and natural temperature variations, existing cracks or joints rapidly propagate out of the old pavement into the new asphalt overlay. The application of an asphalt reinforcement has showed excellent results in delaying the development of reflective cracks.The main objective of this study is to present a model suitable for analyzing pavement structure strengthened with different types and locations of reinforcement for enhancement of fatigue life using nonlinear three-dimensional finite element method. To meet objective of this study, ANSYS (Release-11) was used. Local pavement section was analyzed, using different types and depths of the reinforcemen Under static load of two types of reinforcement were used in the pavement, steel wire and geosynthetics grids (geogrids). The analysis has determined that the best results are obtained when the reinforcement is located at the bottom of the subbase layer.It was concluded that the deflection at the bottom of asphalt layer decreases by 13.8% when the pavement is reinforced by steel wire mesh, while the deflection decrease by 1.8% and 7.9% when reinforced with geogrid type (I) and type(II) respectivel It was found that the vertical normal stress and horizontal strain decrease by 19.8%, 19.32%  respectively when steel wire is used at the bottom of the subbase layer, while they decreases by  3%, 2.17% when the subbase  is reinforced by geogrid type (I) and 13.3%,17% geogrid type (II). Also the analysis of the results shows that the number of the load repetition increase by 1.5, 0.1, 1.3 times before fatigue cracking when steel wire mesh, geogrid type (I) and geogrid type (II) are respectively included at the bottom of the subbase layer.The theoretical dynamic response of the asphalt concrete pavement was investigated under dynamic loads with harmonic variation, using a finite element model and elastoplastic behavior. According to dynamic analysis using 21Hz frequency, it was found that vertical deflection, normal stress and lateral strain decrease by 28.8%, 45.3% and 42.2% respectively when steel wire mesh is used at the bottom of the subbase layer, while they are decrease by 14.8% , 25.5% , 20%  for geogrid type (I) and 17.2% , 37% and 32.3%  for geogrid type (II).Finally the dynamic analysis of the results shows that the number of the load repetitions increase by 9.6, 1.6, 4.4 times before fatigue cracking when steel wire mesh, geogrid type (I) and geogrid type (II) are respectively included at the bottom of the subbase layer. The results obtained are effected by load frequencies and damping values of the bituminous material