Tecnura

15-28

Authors: José Miguel Benjumea Royero, Fredy Saúl Sotelo Monroy, Camilo Eduardo Celis Melo, Gustavo Chio Cho

Context: Regarding their design of reinforced concrete structural walls, the Colombian seismic design building code allows the engineer to select one of the three seismic energy dissipation capacity (ordinary, moderate, and special) depending on the seismic hazard of the site. Despite this, it is a common practice to choose the minor requirement for the site because it is thought that selecting a higher requirement will lead to larger structural materials amounts and, therefore, cost increments. Method: In this work, an analytical study was performed in order to determine the effect of the selected energy dissipation capacity on the quantity of materials and ductility displacement capacity of R/C walls. The study was done for a region with low seismic hazard, mainly because this permitted to explore and compare the use of the three seismic energy dissipations capacities. The effect of different parameters such as the wall total height and thickness, the tributary loaded area, and the minimum volumetric steel ratio were studied. Results: The total amount of steel required for the walls with moderate and special energy dissipation capacity corresponds, on average, to 77% and 89%, respectively, of the quantity required for walls with minimum capacity. Conclusions: it is possible to achieve reductions in the total steel required weight when adopting either moderated or special seismic energy dissipation instead of the minimum capacity. Additionally, a significant increment in the seismic ductility displacements capacity of the wall was obtained

43-54

Authors: Alfonso Mariano Ramos-Cañón, Luis Felipe Prada-Sarmiento, Carlos Alberto Vega-Posada

Context: Experimental results show that the stress-strain behavior of granular materials depends upon the scale analysis. However, due to the intrinsic assumptions of the mechanics of a continuum medium, the analysis of finite elements based on the Boltzmann´s continuum does not allow to consider characteristic lengths in its formulation to reflect the scale effect. Method: This work presents a finite element formulation to analyze plane-strain linear problems using the Cosserat continuum. The degrees of freedom of a four-node quadrilateral finite element are presented and the differential operator is derived to obtain the deformation vector, function form, interpolation matrix, stiffness matrix and nodal load vector. Finally, the Cosserat continuum with the aforementioned element is implemented in a finite element software coded by the authors. The software is used to solve a stress-strain problem of a homogeneous layer with a linear elastic behavior. Results: The differences of the stress and shear strain responses between the conventional and the Cosserat continuum along with the moments acting at the Gauss point level are obtained. Conclusions: The derivation and implementation of the Cosserat continuum provides an alternative finite element analysis to the conventional continuum, along with the advantage of introducing a characteristic length in the formulation to account for the scale effects and rotations observed in granular materials.

69-84

Authors: Marieta Peña Abreu, Carlos Rafael Rodríguez Rodríguez, Pedro Yobanis Piñero Pérez

Objective: This paper proposes a method to analyze the technical, commercial and social feasibility of software projects in environments of uncertainty. It allows working with multiple experts and multiple criteria and facilitates decision-making. Method: The proposal contains two phases, first the necessary information is collected and in second place projects are evaluated using 2-tuple linguistic representation model. The experts are selected by analyzing their curricular synthesis. The evaluation criteria are defined using the technique Focus Group and weighted in the interval (0,1) according to their importance. three domains are offered to express the preferences: numeric, interval-valued and linguistic. For aggregation extended arithmetic mean and weighted average extended are used, preventing the loss of information. A 2-tuple (feasibility, precision) is obtained as a result for each project. Results: The evaluation of P1 project was a very high feasibility with -0,33 of precision. The P2 project obtained a high feasibility with 0,38 of precision and P3 project achieved a medium feasibility with -0,21 of precision. Conclusions: This method is favorable for software projects feasibility analysis with presence of multiple experts and criteria, in environments of uncertainty. It tries heterogeneous assessments without loss of information. Their results are consistent and useful for decision makers.

96-105

Authors: Alfonso Alzate Gómez, Duberney Murillo Yarce, Ricardo León Silva Cárdenas

Context: The traditional methodology for the control of harmonics consists in the use of passive filters tuned to the harmonic components to be eliminated. Passive filters require a frequency-demanding design to avoid resonance phenomena with other elements and they not respond to changes in the dynamics of the electric power system. Method: A best-performing solution alternative is parallel power active filters. These filters, unlike passive filters, inject compensation currents into the network and have adaptation to changes in operating conditions. The implementation of an active filter involves hardware development but also software development. Algorithms are required for calculation of compensation currents and dc bus voltage control. Results: In this work a prototype for the harmonic compensation of 5kVA is designed and built in three phase distribution systems of 220V. The hardware fundamental elements are: coupling coil, capacitor, semiconductor devices and controller. The control algorithms that are responsible for the operation of the active filter at each instant of time are PQ theory, Linear Control-PWM and PI Control. Conclusions: The active power filters are a solution to the presence of harmonics in power systems. They compensate the harmonics generated by nonlinear loads and they don‘t have resonance problems and good dynamic response.

119-140

Authors: Jesús Orlando Escalante Torrado, Jhon Jairo Cáceres Jiménez, Hernán Porras Díaz

Context: Nowadays, Unmanned Aerial Vehicles (UAVs) are among the technological tools most researched and applied in areas such as aerial photogrammetry and remote sensing, presenting itself as an important alternative for capturing imagery with high spatial and temporal resolution. However, UAV flight parameters, image and sensor characteristics, result on major challenges for traditional processing for producing mapping products such as digital elevation models and orthomosaics, that is why it is required to identify new processing strategies. Method: In this paper, a review of the main characteristics of UAVs used in aerial photogrammetry is done, along with related processing strategies currently being used in areas such as computer vision and photogrammetry. Results: From this review, it is shown that processing strategies in the area of computer vision are more akin to the information captured with UAV systems for generating digital elevation models and orthomosaics. Conclusions: The technological advances in UAVs systems and advances in strategies for processing large data volumes continue to drive research and application of these systems for the generation of mapping products more accurately in areas such as photogrammetry and computer vision.