http://nopr.niscair.res.in/handle/123456789/8397 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/8462 Title: Analysis of probabilistic low cycle fatigue design curves at strain cycling <br/> <br/>Authors: Bazaras, Zilvinas <br/> <br/>Abstract: In this investigation, low cycle fatigue tests were carried out and mechanical characteristics of three materials (steel of grades 15X2MFA and 45 and aluminium alloy D16T1), representing all possible variations of cyclic properties (fatigue, quasi-static and intermediate mode of fracture) were determined experimentally. Based on the data obtained, design curves of equal fracture probability for steels 15X2MFA and 45 and aluminium alloy D16T1 at low cycle strain-controlled loading were generated and the design curves were compared with experimental data. Analysis of calculated and experimental low cycle fatigue curves constructed according to the fracture probability parameter, revealed that the use of analytical relationships for lifetime assessment of structures may lead to an error and decreasing safety margin. It is recommended to use experimental 50% fracture probabilistic curves in lifetime assessment of power equipment structures. <br/> <br/>Page(s): 411-418 http://nopr.niscair.res.in/handle/123456789/8461 Title: Effects of high density polyethylene on the permanent deformation of asphalt concrete <br/> <br/>Authors: Hinislioğlu, Sinan; Aras, Hatice Nur; Bayrak, Osman Ünsal <br/> <br/>Abstract: <smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"> This paper reports an investigation about the effect of high density polyethylene (HDPE) in powder form as a bitumen modifier on the permanent deformation of asphalt concrete using Marshall design parameters and creep behaviour. The parameters assessed are the compacted mix density, the percentage of air voids in the mixture, the percentage of void in the mineral aggregate, the percentage of voids filled with bitumen, Marshall stability and flow and also Marshall quotient (MQ), axial strain and stiffness modulus. It is also investigated the effect of HDPE on some physical properties such as penetration, softening point and ductility. Bitumen is mixed with the HDPE at 1-4% by weight of bitumen at 185°C for 60 min. duration using a high shear mixer. Marshall samples prepared with the HDPE modified binder provide the specification limits. The addition of 3% HDPE, results in an increase of 57% in Marshall quotient. In addition, it has been observed that the use of 2% HDPE decreased the permanent strain by 34% and increased the creep stiffness by 52%. The creep recovery values of the asphalt concrete with HDPE after 15 min have been found to be higher than control mixtures. It can be concluded that HDPE modified asphaltic binders provide better resistance against permanent deformation, because of their higher stability and stiffness, relatively lower flow. As a result, HDPE modified asphaltic binders are considered to be very useful in mitigating permanent deformation in hot climate regions. </smarttagtype></smarttagtype> <br/> <br/>Page(s): 456-460 http://nopr.niscair.res.in/handle/123456789/8460 Title: Comparison of three back-propagation training algorithms for two case studies <br/> <br/>Authors: Kişi, Özgür; Uncuoğlu, Erdal <br/> <br/>Abstract: This paper investigates the use of three back-propagation training algorithms, Levenberg-Marquardt, conjugate gradient and resilient back-propagation, for the two case studies, stream-flow forecasting and determination of lateral stress in cohesionless soils. Several neural network (NN) algorithms have been reported in the literature. They include various representations and architectures and therefore are suitable for different applications. In the present study, three NN algorithms are compared according to their convergence velocities in training and performances in testing. Based on the study and test results, although the Levenberg-Marquardt algorithm has been found being faster and having better performance than the other algorithms in training, the resilient back-propagation algorithm has the best accuracy in testing period. <br/> <br/>Page(s): 434-442 http://nopr.niscair.res.in/handle/123456789/8459 Title: Behaviour of the model surface strip footing on reinforced sand <br/> <br/>Authors: Moroglu, Berkan; Uzuner, Bayram Ali; Sadoglu, Erol <br/> <br/>Abstract: A series of tests were carried out with an eccentrically loaded model surface strip footing on un-reinforced and reinforced dense sand to investigate the behaviour of the footing (decrease in ultimate load with increasing eccentricity, failure surfaces and load displacement relations). The experimental set-up used to run the tests consists of tank, model footing, sand and loading mechanism. A single woven geotextile strip sheet was placed horizontally below the footing’s base at a depth half of the footing’s width. The primary failure surfaces occurred at the eccentricity side for this laterally unrestricted footing. The use of this reinforcement increased the ultimate load by about 50% for centrally loaded strip footing in comparison with un-reinforced case and its contribution to ultimate load decreased as eccentricity increased in these conditions. Geotextile not only increased ultimate load, but also increased necessary amount of vertical displacement of footing to reach failure compared with un-reinforced case. The experimental results are in good agreement with Meyerhof’s effective width concept than the customary analysis and the customary analysis is unsafe outside the core. <br/> <br/>Page(s): 419-426