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Physical-mathematical model for determination of variation of internal forces in the simplified analysis of a beam

Márquez Peñaranda, J F | 2021-08-26

. Springs are often taught in subjects of physics such as statics and solid mechanics belonging to civil engineering programs and mechanical engineering. This knowledge can be applied successfully in the modeling of structures and the consequent development of structural analysis. This paper presents the results of an investigation on physic-mathematical models which uses springs to replace complex connective conditions attempting to simplify the structural analysis process. The work focuses on the analysis of beams supported upon masonry walls, applying variations to the span lengths, sections and loads on them and considering realistic variations of the stiffness conditions required in the supports to meet the demands that these variations impose. For this, continuous beams with two spans with three types of section that are supported by walls that support different levels of restriction from different heights of the building of which they are part are modeled. It is concluded that there is an important influence of the slenderness of the beams and the degree of confinement of the supports upon the precision of the simplified model.

Relevance of the use of measurement units and orders of magnitude in the training of civil engineers

Márquez Peñaranda, J F | 2021-05-22

Worldwide, a typical civil engineering program focuses in formal, natural, and applied sciences within an environment of ethical and social responsibility. Mathematics and computer sciences are the main formal sciences. The most widely used natural sciences are physics, earth science, and chemistry. On the other hand, a student who begins the professional cycle of the program must develop skills in applied science to solve practical problems. Complex processes and concepts requiring skills related to mathematics and physics must be developed. Such processes and concepts demand an impeccable handling of operations which involve diverse precision degrees, measurement units and a high variety of basic and derived quantities. This work describes the identification and classification of the main errors made by students when solving written exams applied in a natural environment of structural design courses. Data were collected during four years at a university in Colombia. Report of errors was grouped into five categories named modelling, quantities, regulation, signs, and others. Collected errors were evaluated qualitatively and quantitatively. In addition, each error was assigned to a risk level (high, intermediate, low) according to its potentiality to generate catastrophic errors in professional practice. The quality and number of observed errors seem to be correlated with the time of year in which they occur. On the other hand, the high-risk errors resulted to outweigh the two lower risk levels. This finding is worrying and serves as the basis for making an urgent call to review the way of teaching and its relationship with practical results. In synthesis, this study presents a novel manner to study the formation errors in engineering civil programs. In the near future, it is expected to use the results of this research to propose a procedure for the design and feedback of teaching strategies consistent with the evaluation objectives of each course.

Determination of the expansion capacity by calcination of the clays from San José de Cúcuta, Colombia

Márquez, J F | 2021-06-04

Viscoplasticity and pyroplasticity of clays are important characteristics to control in production processes of lightweight concrete aggregates. When clay is calcined under temperatures above 1,000 ℃, its volume increases. For this reason, it is important to investigate how much volume can gain a given clay before using it in production of lightweight aggregates. This research work has evaluated the expansive capacity of some Colombian clays, applying to them static heat treatment in furnaces at temperatures above 1,000℃. The theoretical background of this work is based on the state of the art of production processes of lightweight clay-based aggregates, which were used to determine if the available clay is a precursor of lightweight aggregate. Also, chemical characteristics were determined using X-ray fluorescence tests. Raw material was chosen from several clays existing in San José de Cúcuta, Colombia. The clays were processed until particles’ diameters resulted smaller than 75 µm. Using these particles, pellets with diameter varying from 10 mm to 15 mm were formed. To determine the expansion capacity and the reduction of volumetric density, volume and weight of pellets were measured before and after applying the heat treatments. When the clay presented a low expansion capacity, technological nutrients were added to the mixtures attempting to maximize the expansion capacity of the pellets. A swelling of up to 3.24 times the initial size of pellets was observed. technological nutrients based on organic matter were chosen and applied in a proportion of 1: 4, i.e., one gram of technological nutrients was added to 4 g of clay. The density of manufactured aggregates resulted to be between 0.50 g cm! ⁄ and 1.93 g cm! ⁄ . Clay mixtures added with technological nutrient showed density lower than 1 gram per cubic centimeter, this means that they could float on water

Physical-mathematical model to determine the structural efficiency of sections shaped as ellipses and parallelograms when used in reinforced concrete columns

MARQUEZ-PEÑARANDA, JORGE FERNANDO | 2021-06-09

Current practice of structural design of reinforced concrete columns uses mainly rectangular and circular sections. Among other reasons, this preference is linked to its ease of construction and spatial efficiency, and the historical inertia of civil works processes. Nowadays, modern design and construction techniques make possible to study the structural beahviour of sections distinctively shaped. If typical sections are extended from circular to elliptical and from rectangular to parallelogram shaped, it is possible to compute mathematical and physical parameters needed for the structural analysis. This work presents a physical–mathematical model to determine the structural efficiency in terms of relative strength and stiffness of sections shaped as ellipses and parallelograms when used in reinforced concrete columns. To solve the model, a Matlab® code for drawing the column interaction diagram of each studied section was written. Each diagram describes, in terms of mechanical physics, the relation between the uniaxial bending and the compression load that defines safety conditions as a mathematical limiting curve. The governing equation has the form P(m,g)=f(M(m,g) in which P describes the axial load strength function, M the bending moment strength function, m the material properties, and g the geometrical characteristics function. Structural efficiency has been expressed as the relative behaviour of each section with respect to comparable rectangular sections. To obtain the results of the model, a Matlab® code was written.

Formation of critical thinking related to the energetic efficiency of applied physics processes of civil engineering works

| 2021-06-11

Current problems associated to contamination and climate change claim for urgent solutions to make real a sustainable development of modern societies. To answer that call, the efficiency of applied physics processes must be continuously evaluated. Particularly, engineering programs are called to strengthen the training offer related to basic and applied physics sciences considering energetic transformation and transferring processes. In the civil engineering field, design, construction, functioning, and final disposition of buildings can be understood as applied physics processes. This work proposes an approach for defining and studying possible variables related to energetic processes and their mutual relationship. Such variables must be able to describe the processes of energetic changes which can occur during construction of civil works. To do so, qualitative analysis of mathematic expressions is done to promote the formation of abstract mental connections made of sensitivity and logical thinking. The methodology is based on four moments: (a) students´ brainstorming related to a particular issue, (b) identification of main topics related to energy transformation, (c) variable operationalization, (d) proposal of mathematical expressions. This proposal is expected to facilitate the construction of concepts related to sustainable development and help students to trust themselves when taking well thought out risks.

Determination of the structural efficiency of quadric and cylindrical surfaces when used as reinforced concrete roof structures

Palacios Pabón, José Daniel | 2020-12-05

Modern architecture of civil engineering structures made of reinforced concrete is demanding solutions to problems related to design and construction of roofs shaped as creative forms which require an adequate combination of arts and physical-mathematical models. In that sense, the quadric and cylindrical surfaces offer an attractive based on their volumetric expression, historicity, and mathematical feasibility. In this work, seven cylindrical and quadric surfaces named elliptic cylinder, parabolic cylinder, elliptic cone, elliptic paraboloid, hyperbolic paraboloid, ellipsoid and hyperboloid of two sheets have been analysed to find out which of them show to be more efficient when used as reinforced concrete roof structures. To do so, the configuration of each structure hase been adjusted in terms of similar stiffness, strength parameters and enclosed volume. The structural efficiency was computed using the results of weight/load ratio, available strength, material consumption and relative stiffness. The solution of the model has been achieved using a combination of exact solutions and numerical methods. To compute the model results a Matlab® code was written and validated using the structural software SAP2000®. The best structural efficiency in terms of stiffness, strength, and materials consumption was obtained for roofs configurated using surfaces built from parabolas, i.e., elliptic paraboloid, hyperbolic paraboloid, and parabolic cylinder. The results of this work can be used in future studies and applications related to arhitectural comfort, structural behaviour and material consumption in construction of roofs.

Escala para valororar el estrés en estudiantes de cursos de física en tiempos de covid-19

Vergel Ortega, Mawency | 2021-01-01

El aprendizaje de la física supone arduos esfuerzos cuyos resultados con frecuencia se muestran en paradójica desproporción lo cual conlleva a generar estrategia para valorar el nivel de estrés entre los estudiantes puesto que esto a su vez, permite establecer acciones pedagógicas y didácticas para la enseñanza de la física y para potenciar el pensamiento físico Objetivo: establecer la validez y fiabilidad de una escala para evaluar el estrés en estudiantes de cursos de física de instituciones educativas de educación superior del municipio de Cúcuta en tiempos de covid-19. Materiales y Métodos: Estudio descriptivo de corte transversal, diseño instrumental; evidencia de validez de constructo se evaluó a través de análisis factorial confirmatorio, correlación y comparación; la consistencia interna se estimó mediante el coeficiente alfa de Cronbach. La muestra estuvo constituida por 1200 participantes seleccionados de la población de estudiantes de instituciones educativas públicas y privadas del municipio de Cúcuta, Colombia, de diferentes programas académicos que tienen matriculado cursos de física. Resultados: se conforma una escala con 20 ítems y 3 factores: ansiedad, presión institucional, afrontamiento y se evalúa su fiabilidad y validez para el diagnóstico de estrés en estudiantes de cursos de física. Conclusión: la escala para evaluar el estrés en estudiantes es válida y fiable.

Comparative study of costs for reinforced concrete portico buildings designed with different degrees of seismic performance

Rojas Suárez, Jhan Piero | 2019-06-27

The Colombian regulation of earthquake resistant construction NSR-10 establishes that the seismic-resistant capacity of a building must be classified according to three degrees of energy dissipation: Special energy dissipation, moderate energy dissipation and minimum energy dissipation. The dimensioning and detailing requirements for structural elements that are demanded according to each grade depend on the need to withstand earthquakes in the inelastic range according to the seismic hazard zone in which the structure is located. This work presents an analysis of the incidence of the requirements of each degree of energy dissipation on the costs of multi-storey building structures. For this, the structural analysis and design of four building configurations (2, 3, 4 and 5 floors) for each minimum energy dissipation, moderate energy dissipation, and special energy dissipation grade has been carried out and the quantities of work with their respective total cost have been determined. As a general conclusion, it can be stated that the cost of building a structure that has special energy dissipation capacity for a given building can be twice that of a structure that has minimum energy dissipation capacity for the same building. On the other hand, it was observed that in order to guarantee a rigidity comparable to that of the other models analyzed, the system of reinforced concrete portal resistant to moments for DES level requires large column dimensions in the case of buildings of four or more floors, which suggests that other types of more efficient elements should be used in the vertical seismic resistance system.

Evaluation and analysis of structures with porch system in lightweight concrete by thermally expanded clay from San José de Cúcuta metropolitan area, Colombia

Caceres Rubio, Jose Rafael | 2019-11-29

The increase in the world population has caused cities to grow vertically, increasing the amount of high-rise buildings, which is why there is a need to develop building materials with greater efficiency, that is, resistant and with less density to the conventional. The objective is to analyze the mechanical behavior of buildings with portico system when being designed with lightweight concrete mixtures made with thermally expanded clay from materials in the San José de Cúcuta metropolitan area, Colombia. Eight structural models were made using the finite element method with the Etabs® software, varying the building height and the concrete type that was used, in order to compare the properties and lightweight concrete characteristics contrasted with the conventional concrete. The modeled buildings were located on land with a capacity of 200 KPa and residential use. The San José de Cúcuta city is located on an area of high seismic threat according to the Colombian construction of resistant earthquake. It was determined that lightweight concrete manufactured with materials from the San José de Cúcuta metropolitan area, Colombia, is structural since it has a compressive strength at 28 days of 26 MPa on average and equilibrium density of 1646.16 Kg/m3 complying with the requirements minimums required by the Colombian regulation of resistant earthquake construction for a concrete to be considered light and structural. It was found that when using lightweight structural concrete in the design of joists and slabs, there is a 10% decrease in dead loads that reach the foundations of the structure, which implies a reduction in the dimensions of the foundations.

An approach to the didactics of physics for structural engineering from an artistic perspective

GALLARDO PÉREZ, HENRY DE JESÚS | 2020-12-16

The use of physics in structural engineering requires the combination of its logical strength with social sensitivity. Logical strength is provided by mathematics and physics with practical solutions and new thinking relationships. Social sensitivity is achieved by inserting this "hard" knowledge into the solution of community problems. It is desirable that the teaching of physics and its applications prioritize holistic knowledge over mechanicity and that this process be similar to the one followed by the artist when he conceives his work: he dreams it, tries it, feels it, and adjusts and delivers it after having understood it with his whole being. In terms of curriculum, it is advisable to rethink the contents, encourage the use of majeutics, reduce standardization, personalize evaluation, and abolish the belief that there can be useless knowledge.

Variability of live loads computed from the analysis of internal forces produced during service life of dwellings

GALLARDO PÉREZ, HENRY DE JESÚS | 2020-12-05

In the field of civil engineering, live loads are related to the use of the floors of buildings and dwellings. Live loads are produced by weight of people and furniture. Such loads generate internal physical effects such bending moments, shear forces or axial forces on structural elements that can show high uncertainty in magnitude and position. This work proposes the application of a physical-mathematical model which considers such uncertainty when forecasting maximum probable live loads to be used in structural analysis and design of elements. To do so, field data of live loads acting on different floors of 20 dwellings built in San Jose de Cucuta, Colombia, were collected and used to verify the model validity. As a result, it was observed a small difference in forecasted live loads with respect to the live loads prescribed by the national and international structural design standards. Live loads forecasted using the model describe modern trends of use of floors and can be used as safe values for designing structural elements. Physical quantities related to bending moment effects resulted to influence importantly the obtained maximum loads values.

Percepción en la planificación de cursos de física: relaciones en entornos sincrónicos

MARQUEZ-PEÑARANDA, JORGE FERNANDO | 2020-12-11

La investigación se realizó con estudiantes de física I y II de universidades del Departamento Norte de Santander-Colombia. Su objetivo fue establecer la relación entre la planificación de las clases de los profesores y las percepciones de los estudiantes en entornos sincrónicos. Cuatro instrumentos midieron la percepción de los estudiantes respecto a la práctica pedagógica de los profesores de física. La investigación siguió un enfoque cuantitativo correlacional. Resultados de la investigación muestran que la percepción de los estudiantes sobre la planeación de clase no guarda una asociación estrecha respecto a la consideración que tienen los profesores, encuentros vía streaming muestra asociación a percepción de enfoque, y resultados de aprendizaje. Se establece correlación alta entre la implementación de consideraciones contempladas en el enfoque dialógico-crítico y por competencias, por parte de un alto porcentaje de profesores. La contribución de las acciones realizadas por los docentes para potenciar el desarrollo del pensamiento variacional de los estudiantes a través del quehacer académico y pedagógico, tiene una relación alta entre lo que el profesor realiza y resultados de aprendizaje obtenidos por los estudiantes.

Determination of expandability clay from San José de Cúcuta metropolitan area, by adding different percentages of sewage sludge

caceres rubio, jose rafael | 2019-11-19

This article shows the research carried out on clay from the San José de Cúcuta metropolitan area, Colombia, to which was added several percentages of a wastewater sludge, which is called as a technological nutrient. The objective of the study is to find out with what percentage of technological nutrient the capacity of expansion of the granules is maximized. The methodology that was followed consists of four phases; preparation of raw materials; pelletizing of raw materials in granules of 5 to 10 millimeters; application of heat treatment in a rotary kiln at the pilot plant level; and application of descriptive statistics for analysis of results. It was determined that the mixture with a 20% of technological nutrient, produces the highest volumetric expansion ratio, with 1.56 times its initial size, while, when adding 30% of the nutrient the same expansion occurs when adding an 10% nutrient, which is 1.07 times the initial size of the particle.

Determination of expandability clay from San José de Cucuta metropolitan area, by varying calcination temperature and time

Sanchez Molina, Jorge | 2019-11-19

In this article, the volumetric change of the clay granules and sewage sludge (technological nutrient), San José de Cúcuta metropolitan area raw materials, when calcined at different temperatures and different burning times is shown. The main objective is to evaluate out the work right conditions (temperature and time), for the production of light aggregates from expanded clay. The methodology that was followed consists of three phases: preparation and pelletization of clay mixtures and technological nutrient; application of heat treatment in a set of muffle furnaces; and application of statistical treatment with the help of Software R. One of the most important results is that the expansion of the clay is indifferent to the time it takes to cook the pellets, and that this property depends solely on the temperature of burning. The temperature that generates the greatest expansion is 1,200 Celsius degrees, using a set of muffle furnaces.

A review about the use of industrial by-products in the lightweight aggregates production of expanded clay

caceres rubio, jose rafael | 2019-11-19

The fabrication lightweight aggregates in recent years has included the addition of industrial by-products in the expanded clay manufacture as modifier agents of the expansion capacity, and also as a destination for the disposal of waste and residues in countries where lightweight concrete is used for the construction of high-rise structures. This article provides a review of the use of by-products as additives in the production of lightweight aggregates from expanded clay available in the literature. As a methodology, the bibliographic search was used through the consultation of specialized databases such as Sciencedirect and other documentary sources of open access scientific journals in several countries. The selection criteria for documents were specified according to the frequency the by-product use. 58 references on investigations by-products addition to the lightweight aggregates production were revised. In conclusion, the study of the use of Colombian byproducts as additives in the expanded clay aggregates production is suggested as a research subject due to the absence of articles related to this topic.