Ephrem Taddesse

• Taddesse, Ephrem; Alamnie, Mequanent Mulugeta & Afeworki, Yonatan Russom (2026). Influence of RAP content on the viscoelastic properties of asphalt mixtures. Transportation Research Procedia. 99, p. 765–773. doi: 10.1016/j.trpro.2026.07.115. Full text in Research Archive Show summary

  This study investigates the influence of Reclaimed Asphalt Pavement (RAP) content on the viscoelastic behavior of asphalt concrete mixtures through dynamic modulus testing and rheological modeling. Asphalt mixtures containing 12.5%, 30%, and 40% RAP were evaluated using both empirical sigmoid master curves and the rheological 2S2P1D model. Results show that increasing RAP content leads to higher dynamic modulus and lower phase angle, indicating stiffer and more elastic behavior due to the aged binder in RAP. Loss modulus analysis revealed reduced energy dissipation in high-RAP mixtures, suggesting decreased stress-relaxation and increased cracking potential. Relaxation modulus curves confirmed that higher RAP mixtures retain stiffness over time, while lower RAP mixtures exhibit greater flexibility. The findings underscore the trade-off between stiffness and flexibility in RAP-modified mixtures

• Alamnie, Mequanent Mulugeta; Taddesse, Ephrem & Hoff, Inge (2023). A study on permanent deformation and fatigue damage interaction in asphalt concrete. Construction and Building Materials. ISSN 0950-0618. 407, p. 1–15. doi: 10.1016/j.conbuildmat.2023.133473. Full text in Research Archive Show summary

  The dominant load-induced damages, permanent deformation (PD) and fatigue cracking (F), are traditionally predicted separately by taking temperature as a variable of departure. This paper presents an experimental study of the two damages and interaction using sequential test procedure (STP) based on ‘sequential damage’. The STP is conducted in PD-F and F-PD sequences on each specimen using a creep-recovery and cyclic fatigue tests. The effect of strain hardening on fatigue cracking is studied in the PD-F sequence, and the impact of fatigue cracking on permanent deformation is explored using the F-PD sequence. First, the shear deformation in tertiary stage of creep recovery is investigated using the dissipated energy ratio criterion and a new fourth creep phase is obtained. Following the PD-F sequence, strain-hardening is found a significant accelerator of fatigue damage rate, particularly on aged and laboratory produced mixes. The fatigue tests without considering the strain-hardening effect underestimate fatigue damage rate. In the F-PD sequence, the effect of pre-existing crack (up to 40% modulus reduction) on permanent deformation is found marginal. The sequential test and damage approach is an effective way to analyze interaction between damage modes and evaluate asphalt mixtures.

• Alamnie, Mequanent Mulugeta; Taddesse, Ephrem & Hoff, Inge (2022). Permanent deformation and fatigue damage interaction in asphalt concrete using energy approach. In Hoff, Inge; Mork, Helge & Saba, Rabbira G. (Ed.), Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields, Volume 3. CRC Press. ISSN 9781003222910. p. 118–127. doi: 10.1201/9781003222910-12. Full text in Research Archive Show summary

  The interaction of fatigue and permanent deformation is very complex phenomenon and little attempt is made on this topic. This paper presents an investigation on the interaction of the two damages using the energy approach. Laboratory tests were conducted for both fatigue and permanent deformation on two different asphalt concrete in a sequential test procedure. A new failure criterion is proposed based on the dissipated energy ratio (DER). The proposed criterion for permanent deformation gives more damage indicator (inflection points) than the conventional flow number/strain rate criterion. The sequential test procedure is also found economical that can be standardized. From the study, strain hardening (pre-deformed) accelerates fatigue cracking susceptible. Similarly, high fatigued samples are more prone to permanent deformation than new samples. The energy approach is convenient for potential coupling of fatigue and permanent deformation interactions.

• Alamnie, Mequanent Mulugeta; Taddesse, Ephrem & Hoff, Inge (2022). Thermo-piezo-rheological characterization of asphalt concrete. Construction and Building Materials. ISSN 0950-0618. 329. doi: 10.1016/j.conbuildmat.2022.127106. Full text in Research Archive Show summary

  The linear viscoelastic (LVE) properties of asphalt concrete is investigated in this paper using a controlled-strain triaxial dynamic modulus test over wide frequency, temperature, and confining pressure ranges. The time–temperature-pressure superposition principle (TTPSP) is applied to validate the thermo-piezo-rheological simplicity of the tested materials using triaxial master curves. The LVE response is found highly stressdependent at intermediate and high temperatures. The Prony series modeling of time-domain properties ascertains that confining pressure strongly correlates with long-term relaxation modulus, the absolute maximum slope of the relaxation modulus, and viscoelastic damage parameter. The stress triaxiality ratio concept is applied, and a new shift model is proposed that takes the triaxiality ratio as an internal state variable in the TTPSP. The model prediction agrees well with the experimental data. Moreover, a relationship between the longterm relaxation modulus and the triaxiality ratio is established. The triaxiality ratio coupled with TTPSP can accurately describe the stress-dependent response of asphalt concrete in the LVE domain.

• Alamnie, Mequanent Mulugeta; Taddesse, Ephrem & Hoff, Inge (2022). Advances in Permanent Deformation Modeling of Asphalt Concrete—A Review. Materials. 15(10). doi: 10.3390/ma15103480. Full text in Research Archive Show summary

  Permanent deformation is one of the dominant asphalt concrete damages. Significant progress has been made to realistically predict the damage. In the last decade, the mechanistic approach has been the focus of research, and the fundamental theories of viscoelasticity, viscoplasticity, continuum mechanics, and micromechanics are applied to develop the material laws (constitutive equations). This paper reviews the advancement of permanent deformation models including analogical, microstructural, and continuum-based methods. Pavement analysis using the nonlinear damage approach (PANDA) is the most comprehensive and theoretically sound approach that is available in the literature. The model coupled different damages and other phenomena (such as cracking, moisture, and phenomena such as healing, aging, etc.). The anisotropic microstructure approach can be incorporated into the PANDA approach for a more realistic prediction. Moreover, the interaction of fatigue and permanent deformation is the gap that is lacking in the literature. The mechanistic approaches have the capacity to couple these damages for unified asphalt concrete damage prediction.

• Alamnie, Mequanent; Taddesse, Ephrem & Hoff, Inge (2021). Viscoelastic characterization and comparison of Norwegian asphalt mixtures using dynamic modulus and IDT tests. In Hoff, Inge; Mork, Helge & Saba, Rabbira G. (Ed.), Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields, Volume 1. Proceedings of the eleventh international conference 8-10 June, Trondheim, Norway. CRC Press. ISSN 9781003222880. p. 118–128. doi: 10.1201/9781003222880-12. Full text in Research Archive Show summary

  This paper presents the comparison of stiffnesses of two types of asphalt concrete mixes (Ab11 and Agb11) fabricated in the laboratory using two commonly used stiffness tests. (1) uniaxial compression dynamic modulus (E*) and (2) Indirect tensile resilient modulus (Mr) tests are conducted at various temperatures, frequencies, and loading times. As expected, both E* and Mr values decrease as temperature increases and frequency decreases. It is observed that the Mr is generally less than the E*. However, this phenomenon is dependent on frequency, temperature, and material type. The viscoelastic property of the two mixes is characterized using the time-temperature superposition principle. Master curves are developed using the mathematical sigmoid and the rheological 2S2P1D models. It has been observed that the rheological model has shown difficulty to converge optimization error to fit Mr master curve while sigmoid function accurately fitted the measured data. Mr is compared with E* both in frequency and time domains using master curves. A closer comparison is observed with the storage modulus((E')and time-domain relaxation modulus E(t) master curves. Considering the inherent time-domain property of Mr, it is recommended to compare with E' or E(t). From the master curves and data analysis and by considering inputs such as energy loss, modular ratio, frequency, temperature, and other volumetric properties, a rigorous Mr vertical shifting function can be developed. Finally, a material database is obtained for Norwegian asphalt mixes.

• Regué, Barrufet Andreu & Taddesse, Ephrem (2020). Condition Assessment of Norwegian Bridge Elements Using Existing Damage Records. Lecture Notes in Mechanical Engineering. ISSN 2195-4356. p. 716–722. doi: 10.1007/978-3-030-48021-9_79. Full text in Research Archive Show summary

  Abstract. The Norwegian Public Roads Administration (NPRA) has recorded bridge element damages in a database for all the bridges it manages since the 1990s. This paper presents a comparison of three methods to establish element condition based on damage records. The methods consist in a non-parametric procedure based on the worst damage registered in the element, linear regression considering also bridge and road characteristics data and classification through an artificial neural network. The methods are assessed using a set of 159 bridges inspected in 2016. The results show that diagnostics of bridge element condition can reach high accuracy by using an artificial neural network classifier and taking into account existing damage records and bridge data.

• Taddesse, Ephrem (2017). Pavement Rutting Prediction Models for the coastal roads of southern Norway. In Loizos, Andreas; Al-Quadi, Imad & Scarpas, Tom (Ed.), Bearing Capacity of Roads, Railways and Airfield. CRC Press. ISSN 9781138295957. p. 1375–1382. doi: 10.1201/9781315100333-197. Full text in Research Archive
• Taddesse, Ephrem & Mork, Helge (2009). Pavement Performance Models For the Ethiopian Pavement Management System. In Birgonul, Talat & Azhar, Salman (Ed.), Proceedings of the Fifth International Conference on Construction in the 21st Century Collaboration and Integration in Engineering, Management and Technology. CITC-V. p. 1266–1274. Full text in Research Archive
• Taddesse, Ephrem & Mork, Helge (2009). Roughness Progression Models by Regression and Artificial Neural Network Techniques. In Tutumluer, Erol & Al-Qadi, Imad L. (Ed.), Bearing Capacity of Roads, Railways and Airfields. CRC Press. ISSN 9780415871990. p. 521–530. Full text in Research Archive

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• Taddesse, Ephrem & Regué, Barrufet Andreu (2018). Condition Assessment of Norwegian Bridge Elements Using Existing Damage Records. Full text in Research Archive
• Taddesse, Ephrem (2017). Dimensjonering av veger i Norge 2017. Full text in Research Archive
• Taddesse, Ephrem (2017). skademekanismer og Tilstandsregistrering – Pavement Performance Criteria. Full text in Research Archive
• Taddesse, Ephrem (2016). Dimensjonering av veger i Norge. Full text in Research Archive
• Taddesse, Ephrem (2016). Pavement Performance Criteria. Full text in Research Archive
• Taddesse, Ephrem (2014). CENG 6307- Advanced Geometric Design of Highways and Airfields. Full text in Research Archive
• Taddesse, Ephrem (2013). Pavement rutting prediction models using artificial neural network technique. Full text in Research Archive
• Taddesse, Ephrem (2013). Intelligent flexible pavement rutting prediction models: the case of Norwegian main road network. Full text in Research Archive
• Taddesse, Ephrem (2011). Tilstandsutviklingmodeller for det norske vegnettet. Full text in Research Archive
• Taddesse, Ephrem (2009). Pavement performance modles for the Ethiopian pavement management system. Full text in Research Archive
• Alamnie, Mequanent Mulugeta; Taddesse, Ephrem & Hoff, Inge (2024). Laboratory-based study of viscoelastic, viscoplastic and fatigue damage of asphalt concrete. Universitetet i Agder. ISSN 9788284271835. Full text in Research Archive Show summary

  Asphalt concrete is one of the most important road building materials worldwide. This material exhibits unique chemical, physical and mechanical properties. The most well-known mechanical properties are the viscoelastic, viscoplastic-viscodamage (deformability), fatigue cracking, and fracture under different environmental and loading scenarios. The investigation of bituminous mixtures focuses on four main properties; stiffness and stiffness change, fatigue and damage law evolution, permanent deformation and accumulation at high temperatures, and cracks and crack propagation at low temperatures. Every mechanistic-empirical (ME) and mechanistic pavement design method attempts to model and simulate these four properties for an accurate performance prediction. The main contributions of this research project are focused on the linear viscoelastic and damage responses of asphalt concrete mixtures. This thesis presents the uniaxial and triaxial viscoelastic responses and the interaction between the permanent deformation and uniaxial cyclic fatigue responses of asphalt concrete mixtures. To achieve these objectives, extensive laboratory investigations were performed using the latest mechanistic asphalt testing equipment. The linear viscoelastic (LVE) properties of asphalt concrete are crucial for mechanistic pavement design. The rutting and fatigue cracking properties of asphalt concrete are directly correlated with the LVE stiffness. In the first phase, the research emphasized the LVE response in both uniaxial and triaxial states, as well as the axial and indirect tensile (IDT) testing modes. Three of the appended papers extensively addressed these properties. The important conclusions from this phase were the triaxiality of the LVE properties at intermediate and high temperatures, and the good correlation of the IDT and axial mode of the stiffness tests at low and intermediate temperatures but not at high temperatures. The second phase of the study was devoted to the damage responses of asphalt concrete. Permanent deformation (viscoplastic-viscodamage) was investigated at high temperatures (both uniaxial and triaxial), and the cyclic fatigue damage was studied at lower temperatures. The results are reported in three appended papers. A thorough investigation of the inherent damage interaction in asphalt concrete has been conducted in this thesis, which has not been done before. Based on the extensive literature review and our observations and experiments, the permanent deformation - fatigue damage interaction sequence dominates the asphalt concrete damage mechanism. This study applied both continuum damage mechanics (CDM) and dissipated energy (DE) approaches to assess the interaction. The existing prediction models have missed the interaction damage mechanism. It is observed that the myth of rutting-fatigue interaction is interrelated. This research confirms that rutting, apart from thermal cracking, is the cause of surface cracking. This observation further confirms the need for a unified damage model for accurate pavement performance prediction.

• Aurstad, J. & Taddesse, Ephrem (2016). Lærebok i vegteknologi. Statens Vegvesen, vegdirektoratet. Full text in Research Archive
• Taddesse, Ephrem (2010). Development of roughness and rutting prediction models using data from road databanks. A comparative study of artificial neural networks and regression techniques. Norwegian University of Science and Technology. ISSN 9788247125083. Full text in Research Archive
• Taddesse, Ephrem (2009). Evaluation of pavement thicknesses using Ground Penetration Radar (GPR). NTNU. Full text in Research Archive
• Taddesse, Ephrem (2007). Comparison of Field Measurements on Low-Volume Roads in Norway. NTNU. Full text in Research Archive
• Taddesse, Ephrem (2007). Comparison of Field Measurements on Low-Volume Roads in Norway. NTNU. Full text in Research Archive

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