Journal of Geotechnical and Geoenvironmental Engineering, 2004
The paper describes a new working stress design methodology introduced by the writers for geosynt... more The paper describes a new working stress design methodology introduced by the writers for geosynthetic reinforced soil walls (K-Stiffness Method) that is now extended to steel reinforced soil walls. A large database of full-scale steel reinforced soil walls (a total of 20 fully instrumented wall sections) was used to develop the new design methodology. The effects of global wall stiffness, soil strength, reinforcement layer spacing, and wall height were investigated. Results of simple statistical analyses using the ratio of measured to predicted peak reinforcement loads (i.e., method bias) demonstrate the improved prediction accuracy. The AASHTO Simplified Method results in an average method bias of 1.1 with a coefficient of variation (COV) of 45%, whereas the proposed K-Stiffness Method results in an average bias of 0.95 and a COV of 32%. Soil strength was found to have limited influence on reinforcement loads for steel reinforced soil walls, especially for high shear strength soils, while global wall stiffness and wall height had a major influence on reinforcement loads.
This paper describes a study that compares the results of usability testing of mobile interfaces ... more This paper describes a study that compares the results of usability testing of mobile interfaces based on three different evaluation approaches: (i) using a computer-based mobile phone emulator inside the laboratory (ii) using a mobile phone inside the laboratory (iii) using a mobile phone linked to a wireless camera in the field. The results regarding user performance and usability problem identification showed the existence of more similarities than significant differences between the results of the three evaluation contexts. Moreover, in the simplest evaluation context of the emulator it was possible to identify a large percentage of the overall set of usability problems found.
Journal of Geotechnical and Geoenvironmental Engineering, 2004
The paper describes a new working stress design methodology introduced by the writers for geosynt... more The paper describes a new working stress design methodology introduced by the writers for geosynthetic reinforced soil walls (K-Stiffness Method) that is now extended to steel reinforced soil walls. A large database of full-scale steel reinforced soil walls (a total of 20 fully instrumented wall sections) was used to develop the new design methodology. The effects of global wall stiffness, soil strength, reinforcement layer spacing, and wall height were investigated. Results of simple statistical analyses using the ratio of measured to predicted peak reinforcement loads (i.e., method bias) demonstrate the improved prediction accuracy. The AASHTO Simplified Method results in an average method bias of 1.1 with a coefficient of variation (COV) of 45%, whereas the proposed K-Stiffness Method results in an average bias of 0.95 and a COV of 32%. Soil strength was found to have limited influence on reinforcement loads for steel reinforced soil walls, especially for high shear strength soils, while global wall stiffness and wall height had a major influence on reinforcement loads.
This paper describes a study that compares the results of usability testing of mobile interfaces ... more This paper describes a study that compares the results of usability testing of mobile interfaces based on three different evaluation approaches: (i) using a computer-based mobile phone emulator inside the laboratory (ii) using a mobile phone inside the laboratory (iii) using a mobile phone linked to a wireless camera in the field. The results regarding user performance and usability problem identification showed the existence of more similarities than significant differences between the results of the three evaluation contexts. Moreover, in the simplest evaluation context of the emulator it was possible to identify a large percentage of the overall set of usability problems found.
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Papers by Walter Holtz