Revista Ingeniería de Construcción

Incidence of cumulative degree-days on asphalt mixture aging in regions of Ecuador

Rolando Vila Romaní — 2024-04-05

The aging of asphalt mixes affects the durability of the pavement. The characteristics of the mixture interact in a complex way with the temperature and service time on site, so the use of the cumulated degree-days (CDD) criterion is possible. The work’s objective is to analyze the aging of the mixtures in the Coastal and Andean regions, through the application of the CDD related to the stiffness modulus at 20 °C in the NAT equipment, obtained from cores sampling in roads built in different years and to make observations regarding existing damages associated with durability. Seven sections were selected from similar mixtures placed between 0 and 14 years ago, made with crushed alluvial materials and AC-20 asphalt from the Esmeraldas refinery. The results show that the aging evaluated through the stiffness modulus presented a greater impact in the Coastal region than in the Andean region due to its higher temperatures, allowing the use of the CDD to unify the behaviors in the two regions into a single relationship. Observations show that the probable range of the progressive evolution of damages, from its beginning to its critical phase, is from 45.000 to 80.000 °C-days.

Fatigue vulnerability assessment of a steel arch bridge using the probabilistic weibull model and considering its remaining service life under localized corrosion effects

Federico A Nuñez-Moreno — 2024-04-05

This study attempts to obtain the approximate fatigue vulnerability of a steel arch bridge from the Colombian national road network. It establishes the interaction between the demand and the available capacity through the Weibull probability equation, and an AASHTO remaining-time equation indicated in (FHWA, 2015). However, the available capacity in terms of the S-N curve obtained from available international references was modified to account for the effects of corrosion present in elements and/or joints in the bridge. The load demand was modeled as the controlled action of the fatigue truck reported in AASHTO, which was systematically located on a structural model represented by Shell and Frame type finite elements, which represented the information available in drawings (in the current Colombian bridge management system), and the one obtained from structural survey activities. The structural model was further calibrated by a parametric study on the modulus of elasticity of steel, which included the minimization of the error difference in the vertical deflections of a bridge load test, keeping the magnitude within the expected ranges established in a protocol. Such reports of actual deflections were achieved using distance meters at important points of the bridge. This model allowed for estimating the magnitude of stresses in the structural elements of the bridge, especially in an area of interest for the study where chemical and physical elements of structural deficiency were determined. The results show an inverse relationship between the probability of failure and remaining service life. The effect of corrosion on the remaining capacity and the probability of failure of the structural elements is clear.

Ecuadorian asphalt aging in laboratory and field.

Rolando Vila Romaní — 2024-04-05

The aging of asphalt binders has a great impact on the behavior of pavement. The specifications for performance grade include tests on short-term (RTFOT) and long-term (PAV) aged residues. However, aging is greater at the top of wearing course than deeper zones, long-term tests do not correlate accurately with field aging and in the latter, the incidence of local temperature is not considered accurately. The objective is to relate the aging of Ecuadorian asphalt at the laboratory level, applying different conditioning times in the PAV, with the field aging from asphalts recovered from the top of pavements surface in selected roads of the Andean and Coastal regions, with different construction times and cumulated degree-days (CDD), using certain rheological parameters. As a result, in the Ecuadorian asphalt, the RTFOT residue is equivalent to field aging of 1.1 years in the Coastal region and 1.7 years in the Andean region. On the other hand, the usual PAV of 20 hours corresponds to field aging of 5.8 years for the Coastal region and 9.3 years for the Andean region. The progressive evolution of damage to our roads, without considering traffic, corresponds to conditioning times in the PAV between 13.0 and 26.6 hours.

Implementation of a smeared crack model in the finite element method and its application to two-dimensional nonlinear analysis of concrete beams

Juan Carlos Tamásco Sandoval — 2024-04-05

This paper describes the implementation of a two-dimensional rotating smeared crack model within the framework of a nonlinear finite element analysis code, and its application to the mechanical behavior of the plain concrete. In this work, the formulation of three concrete softening law subjected to fracture Mode-I is adapted, considering infinitesimal strains, static loads and two-dimensional conditions. The rotating smeared crack model and the three softening laws are all implemented in Fortran language, into the open source software for nonlinear finite element analysis HYPLAS. The pre- and post-process for a graphical representation of the mesh and the results are done with GMSH or GiD. Finally, three experimental tests of concrete beams of other authors are simulated. The concentration of the displacement contour lines obtained in the simulation represents the crack patterns in the solid. The relationship between the applied load and the representative displacement in each analysis step describes the mechanical response of the beam. Other computed parameters were the crack opening and the principal stresses in the solid. The numerical results were satisfactory in comparison with the experimental tests.

Impact of change orders on construction material waste in residential buildings projects

Ibrahim Mahamid — 2024-04-05

The current study attempts to address the relationship between material waste and change orders in residential building projects implemented in the West Bank in Palestine. The main objectives include: (1) identify the main factors affecting change orders in residential projects, (2) identify the main factors affecting martial waste eon construction sites, (3) address the relationship between change orders and construction material waste, (4) develop prediction model that shows the impact of change orders on material waste. To achieve this, two methods are used: (1) questionnaire survey is conducted to identify the main factors affecting change orders and the major factors of material waste on construction sites. Fourteen (14) factors believed to affect change orders and 15 factors that might affect material waste are investigated in this study. (2) Case study is conducted to address the impact of change orders on material waste. Data collected from 40 residential building projects implemented in the West Bank in Palestine. Regression analysis is used to establish the predictive model that relates the change orders and material waste. Results indicate that the top five factors affecting change orders include: change of project scope by owner, shortage in equipment and materials, change in materials, design mistakes, and change of plans by owner. It also shows that the top five factors affecting material waste are: rework, lack of labors skills, design errors, purchasing materials not complying with specifications, and frequent design changes. The results revealed a strong relationship between number of change orders and construction material waste on site.

Physical and mechanical characterization of cement-stabilized compressed earth bricks

Sócrates Pedro Muñoz Pérez — 2024-04-08

Soil is the basic material for the manufacture of compressed earth bricks, working the soil without any type of stabilization the physical and mechanical properties are minimal. This research aims to evaluate the physical and mechanical characteristics of compressed earth bricks stabilized with different dosages 5, 8, 12, 12, 15 and 18 % of cement, the tests that were performed were: absorption, compressive strength and flexural strength per unit of masonry, compressive strength of piles, diagonal compressive strength of walls and the X-ray diffraction test of the bricks; the results obtained from the different tests determine that with 18% cement the optimum strengths are obtained, the samples subjected to the absorption test have a 12. 63%, as for their compressive strength increased by 53. 95%, flexural strength in 43%, resistance to compression of piles in 36.6%, diagonal compression strength of walls in 41.24%, taking as a reference base the standard sample of 0% cement, in the X-ray diffraction test of the compressed brick stabilized with 18% cement where predominates the 32. 4% of calcium silicate, 23.8% of aluminum silicate, 17.4 % of hydrated calcium, 14.2 % of illite, 6.86 % of calcium oxide, 3.34 % of quartz, 1.2 % of kaolinite and goethite 0.8 % ; it is concluded that the bricks of compressed earth stabilized with cement (BCESC) is a sustainable construction alternative that improves the mechanical properties of the soil

Inflation in Real Estate Development:

Francisco Vergara-Perucich — 2024-04-05

One of the expected consequences of the post-pandemic era has been the global inflationary process with multiscalar characteristics, where construction prices in Chile have experienced unpredictable fluctuations, severely affecting various types of projects, both public and private, from large companies to small public initiatives. On the other hand, the growing demand for housing in the midst of the housing crisis in Chile has been hindered by the increase in material prices. In this scenario, it is relevant to generate an ecosystem of predictive models for construction costs that take into account the external factors that influence construction costs and, therefore, the price of new homes and public infrastructure. This study contributes to the development of this ecosystem by using a vector autoregressive (VAR) model to identify the predictive factors that influence construction costs in Chile, particularly exploring the influence of macroeconomic variables on construction costs by considering a set of incidental variables that are not always considered in this type of analysis and that involve fundamentals from sectors other than construction. The methodological results allow for the testing of predictive models with a good level of statistical significance, as well as clearly identifying those external factors that impact construction material prices.

Investigating the Causes of Variation Orders in Egypt

Wahbi Albasyouni — 2024-04-05

Introduction: Variation order became one of the major issues that is presented in construction projects. The nature of work in the construction industry is complex and difficult. Thus, variation order is expected to occur in every project due to its nature. The purpose of the study was to investigate the causes of variation order in construction projects in Egypt according to the perspective of professional parties working for medium and small sized construction companies. The main method used for data collection was a questionnaire survey with experts working in the Egyptian construction industry. 62 participants from 18 construction companies were invited to take part of the study, 51 of them accepted the invitation. The findings showed the top ranked causes of variation order according to small and medium sized construction companies were poor communication, omissions in the design, financial limitations of the owner, additional work requested by the client, and contractor’s desire to gain more profits. Thus, the proper understanding of the causes of the problem can be helpful towards establishing a suitable criterion for reducing variation orders in construction projects in Egypt. The contribution of this study lies in the fact that only a very limited number of research explored the perspective of medium and small sized construction companies in Egypt. The study can be useful for other countries with similar working conditions and still suffering from the adverse impact of variation order.

Development of a multicriteria matrix for decision making in the management of flexible pavements in an urban road network.

DARWIN ROSERO VEGA — 2024-04-05

Decision-making for interventions in urban road networks is often carried out reactively, addressing roads in the worst condition first, which reduces the length of intervention in the entire urban road network under an assigned budget. The objective of this work was to establish a methodology to prioritize the intervention of asphalt pavements on urban roads through a multi-criteria matrix that allows optimizing the management of pavements in the network. The criteria were previously adjusted and validated by road infrastructure experts using the Likert scale. Subsequently a large group of experts completed the multi-criteria matrix to qualify and weigh each of the criteria and intervention alternatives considered to address each of the established problems; the goal is to preserve the urban road network in good condition. With the support of Geographic Information Systems (GIS) tools, each criterion was represented by a vector shapefile format, each of them was transformed into raster format and reclassified to assign a specific score. The attributes of the raster format used information from the road network of the city of Itagüí (Colombia). The final result was the weighted overlay of maps that allowed establishing the prioritization of the roads to intervene according to the score obtained in each road segment, which allows the administrator to make efficient decisions in an urban network.