Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

In a multilayer system, as a pavement with layers of different materials, movements between layers are an important source of cracks. When the adhesion between layers is poor, often cracking appear early with increasing deformation at the loads of traffic due to consumption of internal energy of the material, causing problems fatigue cracks from top to bottom (top- down). In this context the study of adherence between different substrates (base concrete and asphalt base), interposing different geosynthetic materials, using as a bonding agent a modified asphalt emulsion, and placing thereon a layer of conventional asphalt CAC D20, acting as reinforcement in rehabilitating deteriorated of pavements was proposed. It is considered as a reference intercoat adhesion without placing any geosynthetic material. To quantify the adhesion it was used strength test cut LCB (Laboratorio de Caminos de Barcelona), and the adhesion test traction implemented in the LEMaC, Highway Research Center of the National Technological University of La Plata is used. The load and deformation at the interfase of materials, were tested and a result it was observed that adhesion is favorably or unfavorably affected, depending on the type of geosynthetic material and the substrate where it is applied.

This paper discusses the relationship between the Costa Rican Seismic Code 2010 (CSCR-10) specifications and the research generated as result of those specifications. The use of timber for construction in Costa Rica has been growing since 2000, including the development of industrialized products such as structural laminated timber (GLULAM) and plywood. Consequently, the CSCR began to work on a chapter for the CSCR-10, in which the specification for structural timber is developed. The objective of this paper is to highlight the impact that the design codes and standard specification have had in the development of applied research in the field of design and construction of timber structures. To establish this relationship, the sections of the CSCR-10 are explained and then, the most relevant investigations are described. Finally, it is concluded that the CSCR has a great impact in the development of research of structural timber in Costa Rica. The previous is reflected on the eight investigations that have been carried out in a period of eight years.

This paper presents the results of an off-line vibration based monitoring of a simply-supported, prestressed concrete box girder bridge. The structure evaluated was the Tenorio River Bridge in National Route 1, Costa Rica, which was built in 2014. The purpose of the study was to register the dynamic response of the bridge under operational conditions and to identify its vibration modes using the covariance driven stochastic subspace identification method (SSI – COV). The ambient vibration test was carried out using a hybrid monitoring system developed by LanammeUCR. Uniaxial accelerometers were used to register the accelerations at 25 different locations on the bridge for approximately 40 minutes. Through the analysis of the data, nine vibration modes were identified in the frequency range of 0 to 25 Hz, including vertical bending modes, torsional modes and one transverse bending mode.

Bridge Weigh-In-Motion (BWIM) has been demonstrated to be reliable for obtaining critical information about the characteristics of trucks that travel over the highways. Continued improvements provides greater opportunity for increased use of BWIM. Traditional BWIM systems based on measuring the bending strain of the bridge have various challenges which has led to a class of BWIM methodologies that employ the use of shear strain in determining the gross vehicle weight (GVW) of crossing trucks. However, the known techniques of these shear-strain BWIM methods assume or measure the shear influence line for the calculation of the GVW. In this paper, an alternative shear-strain based BWIM technique is proposed. The method presented here is independent of the influence line, does not require a measurement of the speed of the truck, and is based on the difference in magnitude observed at the discontinuity of the shear strain record as a truck crosses over the sensor location on the bridge. A series of field tests is presented that demonstrate this shear-strain based BWIM method has error levels consistent with other more complex BWIM methods and as such has great potential to be used for determining the GVWs of trucks that travel on simple or multispan bridges in a consistent and reliable manner.

Asphalt has complex chemical and physical compositions that normally vary with the source of crude oil. Its composition is based on approximately 84% C, 10% H2, 1% O2 and 5% trace elements such as S, Ni, V and Fe. This is the development of a new method to quantify V, Ni, Zn and Fe on asphalt AC-30 by atomic absorption spectroscopy. These metals were detected qualitatively with a higher intensity in an X-ray analysis by fluorescence in an electron scanning microscope. Some metals found in asphalt may have a catalytic effect on the oxidation of asphalt.The research proposes a treatment process of up to 2 g of asphalt, which is based on dilution with mineral spirits in volumetric flasks with the aid of an ultrasonic bath to lighten the dilution. The parameters of optimization of the method are dictated by looking for the adequate instrumental data in the atomic absorption equipment to obtain the highest possible absorbance in the alignment of both the burner and the hollow cathode and deuterium lamps; In addition to the optimization of the flame and the flow of the nebulizer. The calibration curves of each metal were performed with a hydrocarbon-based standard to measure metal concentrations in asphalt in mg / kg with a linear correlation coefficient of at least 0,995. The asphalt recovery study is performed with the addition of a quantity of the metals directly to the asphalt matrix aliquots. The concentrations obtained for Ni were 70, V 330, Zn 24 and for Fe 10 ppm, which presented a relative standard deviation of less than 1%, indicating that measurements of the same sample are accurate and have little dispersion between them. The average recoveries were 99,17% for Ni, 100,30% V, 92,26% Zn and 97,72% Fe. These results indicate that the method is reliable for the quantification of metals by the atomic absorption technique; values greater than 100% are given by readings of absorbances higher than expected or by generation of false positives in the technique. 

The composition of the hot asphalt mixture used for pavements is defined according to a design that try to meet the performance according the project in which it is to be used. Since asphalt is the binding material that provides cohesion and adhesion to the mixture, it is important to be able to quantify if the mixture produced contains the amount of asphalt established in the mix design, for that different tests have been developed to determine the content of asphalt. Although the purpose of the test methods is the same, there are doubts about the accuracy of some of them, and especially about the correlation between test procedures. This study aims to provide real results of an asphalt mix produced in a production plant, which is analyzed using the different methods and equipment to compare them with the production data and thus determine the precision and accuracy of each procedure. The results show that the methods of incineration by resistance furnace, incineration in the infrared furnace and the solvent extraction method using centrifuge do not present significant statistical differences, which is not the case with the solvent extraction method using a reflux system. The latter, despite being the one with the lowest variability, is also the most distant from the design asphalt content. However, the four methods studied are within the tolerance allowed by national regulations with respect to the asphalt content established in the blend design. In addition, as some laboratories use the gasoline extraction method as solvent instead of ACS grade trichlorethylene, the extraction test is performed using both solvents to determine whether the result with the alternative solvent is reliable. The results obtained discard it as solvent, as it does not produce statistically comparable results with the method when using trichlorethylene.

This paper presents a synthesis of the experimental results obtained from testing the evolution of the compressive strength in concrete made with different modified cements at different ages. It includes the characterization of two aggregates of different provenances (river and quarry) and three types of modified cements. The cements tested correspond to MM/C (P-C) -28, MM/C (C-P) -28 and MC/A - AR. The objective of the study was to generate the standard resistance development curves of six concrete mixtures (in percentage terms), using these cements and aggregates. The characterization tests were conducted out following the INTECO and ASTM standards. The curing of concrete specimens took place in a humid chamber at 4 different ages (3, 7, 28 and 56 days). The strength of the concrete was obtained through tests on the Universal Machine, and the results were processed and validated statistically, using the acceptance parameters of the ACI 214-2002 report. From the analysis, it was possible to generate the curves of standard development of resistance for all the cements under study using two provenances of aggregates, including an inferential statistical analysis for the resistance results of the concretes. It was concluded that, by varying the origin of the aggregate for the same cement, the resistance of the concrete is significantly different (on statistical terms), as for the same aggregate when the type of cement is changed.

This paper compares the application of different computational modeling techniques of wall-type buildings; specifically, the following modeling methodologies were studied: Modeling through frame type elements with rectangular cross-section Modeling through frame type elements with irregular cross-section Modeling through shell type elements In order to apply each modeling techniques to different buildings, the structural analysis software called ETABS was used. In which a spectral dynamic analysis of each one of these models was carried out, with which a results matrix was created that allowed comparing and discussing the different global structural responses that can be obtained for the same building when a linear analysis is carried out using different modeling techniques. From this comparison, it is concluded that in general, the models composed of frame type elements with a rectangular cross-section and the models made with area type elements show similar behaviors, so that wall-type buildings of up to 30 levels could be modeled with both methodologies without significant differences in structural responses (periods, seismic forces at the base of the structure and drifts). On the other hand, models made with frame type elements with irregular cross-section presented significant differences for these same responses.

In recent years, different test methods and procedures have been developed to evaluate the rheological properties of asphalt materials, some of which have been incorporated in design methodologies and standards in Mexico. However, the correct determination of mechanical properties of asphalt mix involves complex evaluations and the need for other areas of knowledge as metrology, instrumentation and data processing, combined with a clear understanding of the mechanical behavior of a viscoelastic material. This is the case for the dynamic modulus test, which aims to evaluate the linear viscoelastic properties of the asphalt mixture by determining two mechanical parameters, the dynamic or complex module (|E*|) and the phase angle (δ). The present article illustrates the evaluation of the viscoelastic properties of an asphalt mixture and the analysis of the data obtained in tests. Indicating some of the general errors in the conduction of the test and to justify the test sequence proposed by the IMT regarding the AASHTO T 342 Standard, which does not alter the identification of the linear viscoelastic properties of the asphalt mixture. 

This research paper presents an alternative methodology for the surface evaluation of pavements on urban roads, using georeferenced images obtained by an unmanned aerial vehicle (UAV) that are processed by generating an orthophoto and a high-resolution 3D digital model. The analysis of the generated products allows the total inspection of the pavement in a safe way, identifying the type of deterioration, its severity and its damaged density, as parameters and inputs to use the Pavement Condition Index (PCI) Method. The results obtained in a test track show that the VANT method collects data in a safer way, allows more informative plans with reliable values and avoids accidents of the technical staff in comparison with the traditional method. This research innovates an alternative procedure to evaluate pavements periodically in order to establish strategies for maintenance and rehabilitation of urban roads.