Non-linear response of the rockfill in a concrete-faced rockfill dam under seismic excitation

Kartal M.E. | Bayraktar A.

Article | 2015 | Mathematical and Computer Modelling of Dynamical Systems21 ( 1 ) , pp.77 - 101

This study investigates the non-linear response of the rockfill in a concrete-faced rockfill dam under seismic excitation for various concrete slab thicknesses from 30 to 100 cm thick. The effect of the friction in the concrete slab rockfill interface on the non-linear response of the rockfill is also considered in the numerical solutions. The friction contact in the concrete slab joints is provided with contact elements based on the Coulomb’s friction law. The hydrodynamic pressure of the reservoir water is considered by the fluid finite elements based on the Lagrangian approach. Geometrical and material non-linear behaviours of th . . .e dam-foundation-reservoir interaction system are considered together in the finite element analyses. The Drucker–Prager model is used to obtain materially non-linear behaviour of the concrete slab. The multi linear kinematic hardening model is used for rockfill and foundation rock in the material non-linear analyses. Therefore, the uniaxial stress–strain relations of the rockfill and foundation rock are determined from the shear stress–shear strain relations of the gravel and rock, respectively. The principle compressive and tensile stresses of the rockfill are investigated along the horizontal section of the rockfill. According to numerical analyses, the most critical stresses occur in the upstream and downstream faces of the dam for the concrete slab thickness of 30 cm, while the optimum thickness for seismic performance is 58 cm. © 2014, © 2014 Taylor & Francis Daha fazlası Daha az

Area-based quality control of airborne laser scanning 3D models for different land classes using terrestrial laser scanning: sample survey in Houston, USA

Sefercik U.G. | Glennie C. | Singhania A. | Hauser D.

Article | 2015 | International Journal of Remote Sensing36 ( 23 ) , pp.5916 - 5934

Airborne laser scanning (ALS) is a remote-sensing technique that provides scale-accurate 3D models consisting of dense point clouds with x, y planimetric coordinates and altitude z. Using ALS, very high-resolution (VHR) digital surface models (DSMs) have been widely used for commercial and scientific applications since the early 1990s. Although there is widespread usage, there has been little comprehensive investigation of quality control for ALS DSMs in the literature, as most studies have been limited to assessing point-based vertical accuracy. This article is dedicated to investigating the quality of ALS DSMs for different land c . . .lasses using statistical and visual approaches based on absolute and relative vertical accuracy metrics. Rather than a limited number of ground control points (GCP), the model-to-model-based approach is applied and DSMs derived from terrestrial laser scanning (TLS) point clouds that have around 5 mm absolute and 3 mm relative geolocation accuracy were used as the reference data for comparison. The results demonstrate that in open, grass, and building land classes, the ALS DSMs reached both standard deviation (?) and normalized median absolute deviation (NMAD) of 3–5 cm after the elimination of any systematic biases. This result sufficiently satisfies the vertical accuracy requirements for 1/1000-scale topographic maps determined by National Digital Elevation Program (NDEP) specifications. In tall vegetation, a higher number of discrepancies larger than 0.5 m exist, reversing the relation between ? and NMAD. These vegetation errors also do not appear to be normally distributed. As an additional investigation, the performance of ALS DEMs under dense high-vegetation areas was assessed. These under-canopy ALS DEMs, created using only classified ground returns, offer both ? and NMAD of 12–14 cm, a performance level that is difficult to achieve under-canopy using photogrammetric techniques. © 2015 Taylor & Francis Daha fazlası Daha az

Quality function deployment in the speculative house-building market: How to satisfy high-income customers

Ulubeyli S. | Kazaz A. | Soycopur B. | Er B.

Article | 2015 | International Journal of Construction Management15 ( 2 ) , pp.148 - 156

This paper presents a study that reports a detailed process of 'quality function deployment', considering an ultra-luxury villa project. It is based on a questionnaire survey that was applied to 42 residents and seven top managers. The results highlight real expectations of high-income residents. Residents were not satisfied with the 'sauna', 'sports areas', and 'fitness centre' despite the fact that these were among the least important expectations. However, residents were satisfied with the 'security of the complex', 'architectural design', and 'quality of the end-products'. If some expectations (i.e. 'areas for common use', 'play . . .ing areas for children', and 'quality of the end-products') achieve better technical standards in the next projects, demand for luxury residences will likely be improved. Consequently, 25 expectations and corresponding findings constitute a preliminary framework for an expectations agenda for such projects for builders who wish to improve marketing practices. © 2015 Taylor & Francis Daha fazlası Daha az

Difficulties in learning and teaching statistics: teacher views

Koparan T.

Article | 2015 | International Journal of Mathematical Education in Science and Technology46 ( 1 ) , pp.94 - 104

The purpose of this study is to define teacher views about the difficulties in learning and teaching middle school statistics subjects. To serve this aim, a number of interviews were conducted with 10 middle school maths teachers in 2011–2012 school year in the province of Trabzon. Of the qualitative descriptive research methods, the semi-structured interview technique was applied in the research. In accordance with the aim, teacher opinions about the statistics subjects were examined and analysed. Similar responses from the teachers were grouped and evaluated. The teachers stated that it was positive that middle school statistics s . . .ubjects were taught gradually in every grade but some difficulties were experienced in the teaching of this subject. The findings are presented in eight themes which are context, sample, data representation, central tendency and dispersion measure, probability, variance, and other difficulties. © 2014, Taylor & Francis Daha fazlası Daha az

The effect of project-based learning on students’ statistical literacy levels for data representation

Koparan T. | Güven B.

Article | 2015 | International Journal of Mathematical Education in Science and Technology46 ( 5 ) , pp.658 - 686

The point of this study is to define the effect of project-based learning approach on 8th Grade secondary-school students’ statistical literacy levels for data representation. To achieve this goal, a test which consists of 12 open-ended questions in accordance with the views of experts was developed. Seventy 8th grade secondary-school students, 35 in the experimental group and 35 in the control group, took this test twice, one before the application and one after the application. All the raw scores were turned into linear points by using the Winsteps 3.72 modelling program that makes the Rasch analysis and t-tests, and an ANCOVA ana . . .lysis was carried out with the linear points. Depending on the findings, it was concluded that the project-based learning approach increases students’ level of statistical literacy for data representation. Students’ levels of statistical literacy before and after the application were shown through the obtained person-item maps. © 2015 Taylor & Francis Daha fazlası Daha az

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