The effects of physical and chemical weathering processes in completely decomposed granitic rocks strongly condition the shear strength parameters commonly used in soil mechanics, where soils have high variability. The technological progress and the joint use of deterministic and probabilistic methods allow for the incorporation of soil variability within the calculations. This paper presents a probabilistic slope stability analysis using a model of random variables to characterize the shear strength parameters. The Monte Carlo simulation is used for generating the values of the random variables, which also allows for the simultaneous evaluation of slope stability in terms of the factor of safety, probability of failure and reliability index. The results of this methodology tend to be more conservative, considering the risk of using average safety factors to evaluate stability when considering the variability of soil properties.
The main aim of this paper is to demonstrate the benefits that building using natural elements can provide to indoor environments when temperatures are lower. For this purpose, an experimental procedure was used to allow a comparison of the thermal behaviour of four systems: a prototype called Control (no vegetation) and three different combinations of vegetation (roofs and facades) installed in a region of tropical climate. They recorded simultaneously internal surface temperatures, internal air temperature and the external environmental conditions. The results show that the use of plant systems in buildings establishes a passive technique effective in reducing energy consumption, because of its insulation property and it maintains more pleasant thermal internal conditions than internal ones.
In the rural areas of Mexico and Latin America, prevails the people of low income, living in unsafe and unhealthy, precarious housing that anchored to its inhabitants in the cycle of poverty. The academic team, with the purpose of contributing to the solution to the problem of rural housing, developed prototypes of low-cost housing were built by families living in conditions of high marginalization in the town of Ocuilapa Juárez, Chiapas. The construction used materials in the place; the foundation stone, sand with high clay content (22%) in the preparation of hollow concrete block and wood in the roof structure. This article presents the results of measurements made with accelerometers in two homes, to determine the level of vulnerability to seismic scenarios. The fundamental period of vibration obtained are from 0.08 to 0.12 seconds; range of values recommended by (Hernández et al.,1979), for structurally sound homes. Also, the analyses carried out prove that dwellings are in "low vulnerability" in the presence of some earthquakes.
This paper explores the sustainable factors, which are taken into consideration by engineers during the holistic process of building Projects Life Cycle (LC) in the Gaza Strip. A total of 53 sustainable factors (economic, social, and environmental)) were identified from extensive literature review and were modified according to the pilot study.
These factors are classified into 5 project LC phases: inception phase, design phase, construction phase, operation phase, and demolition phase. A questionnaire survey is adapted in this study. A total of 119 questionnaires were distributed randomly to engineers working in construction projects in the Gaza Strip to solicit their opinions regarding taking sustainability concepts into consideration. The results revealed 10 most important sustainable factors that were taken into consideration by engineers in the LC phases of the construction projects in Gaza Strip, which are classified as follows: 4 factors are classified under the inception phase, 3 factors under the design phase, 2 factors under the construction phase, and 1 factor under operation phase. The most common factors that are taken in consideration are: provision of services, standardization, community amenities, materials choice, and site security.
This investigation seeks to determine the relationship between working capital as a financial measure and the efficiency level of construction companies. The study sample is intentional, with 58 participating companies, from which the financial information was obtained in a time horizon of four years (2011-2014). In the first stage efficiency was assessed using Data Envelopment Analysis (DEA), and in the second stage Tobit regression model was applied in order to identify the relationship between the variables. Efficiency levels evaluated show a reduction in the average efficiency in the construction sector for the years 2012 and 2013, and the regression results do highlight a positive link between efficiency and working capital for all years, which indicates that a common financial strategy based on reducing working capital does not lead to an increase in the efficiency level of construction firms. This research can benefit not only Ecuadorian construction companies, but others who wish to improve their competitive advantage based on their financial information.
The present study evaluated the potential use of Blast Furnace Slag (BFS) as forming material of untreated granular layers in pavement (e.g. base, subbase and subgrade), and as stone aggregate in the manufacture of asphalt mixtures. For that purpose, tests of characterization, X-ray diffractometry (XRD), X-ray fluorescence (XRF) and imaging in a scanning electron microscope (SEM) were executed on the BFS. As a general conclusion is reported that the BFS can be used in the formation of unbound granular layers of subbase. As granular base material, its use would be recommended on roads with low traffic volumes or with thick asphalt layers and as a selected material, in tertiary roads that support light traffic. In the case of HMA is not recommended to use the coarse fraction of the BFS as a stone aggregate. However, the obtained results indicate that the fine fraction shows good characteristics to be used in the production of the mastic of such mixtures.
Continuum Damage Mechanics describes the progressive degradation of the material properties based on a phenomenological model. This work presents the formulation, implementation and validation of a scalar damage model applied to three-dimensional solid elements. It is a highly versatile model defined from a fault surface and a scalar damage variable. Isotropic elastic materials with softening behavior and a single threshold surface can be simulated by this model. Four parameters are necessary to define the model and they derive from the classical stress-strain test. The model is implemented through a user-defined UMAT subroutine in software ABAQUS. The non-linear equilibrium equations are solved by an implicit algorithm based on the Backward Euler Method. The tensile stress validation shows an adequate correlation between the numerical and experimental results, with a 6% dispersion of dissipated energy. Finally, an illustrative example is presented. The results show that it is a simple but powerful tool for the numerical analysis of brittle materials.
This paper shows the importance of performing an asynchronous dynamic analysis for some bridge types. First, the existence and damage caused by the asynchronous seismic excitation are explored. Then, the general mathematic expression that describes the movement of structures under non-uniform seismic excitation in its supports and the asynchronous patterns that characterize the asynchronous phenomenon (wave passage, loss of correlation, and local site effect) are introduced. In a general approach, the analysis methods that have been implemented and the design codes that emphasize the importance of asynchronous analysis on bridges are also presented. Finally, the results obtained by some authors interested in bridges subjected to asynchronous seismic excitation for several structural types are discussed.
The present work describes different stages that the Urban Development Institute (IDU) has addressed to achieve the adequate and correct application of crumb rubber modified (CRM) asphalt mixtures. The first research stage in the laboratory included an exhaustive analysis of the mechanical properties of the mixtures, according to asphalt mixture typologies used in Colombia. In addition to a brief application on a fatigue carousel to evaluate the deterioration of this type of mixtures under accelerated loading. The second stage deals with the performance analysis and comparison with other types of asphalt mixtures modified with polymers available in the Colombian market. This stage involved the construction of one full-scale pavement test lane with different sections considering asphalt modified with polymers (SBS, SBR), and two sections with rubber asphalt, one through dry process and the other through wet process. As a result of these stages, a technical specification was developed to serve as guidelines for the production and analysis of mixtures added with crumb rubber. Likewise, the environmental advantages of applying this technology in the Colombian context are described.
PDF
(688KB)
PDF
(705KB)
