The main methods for assessing pavement condition do not consider the factors involved in pavement deterioration. Thus, the objective of this research was to develop a current pavement condition index that took into account the factors that lead to deterioration. The index included an assessment of riding comfort, existing distresses, longitudinal slope, drainage aspects and bus traffic volume. The criteria and performance levels were weighed by means of a method known as Measuring Attractiveness by a Categorical Based Evaluation Technique. To be tested and validated, the index developed was applied to 13 Sample Units, and a correlation analysis based on the Fixed-Value Matrix method was performed. In said analysis, a correlation of 0.12 was obtained when all units were considered, and 0.48 when the units with high traffic volume were removed. It was concluded that the proposed method presents a more rigorous assessment of pavement condition, mainly when it comes to distresses and bus traffic.
In the current study, the finite element method using the ABAQUS program is employed to investigate the shear behavior of reinforced concrete (RC) beams strengthened by carbon fiber reinforced polymer CFRP. Load-deflection curves, modes of failure and the pattern of the cracks are studied. Also, the influence of compression strength of concrete, the configuration of CFRP (U shape and 2 side bond shape) and shear span to depth ratio (a/h ratio). The results show that the shear capacity of RC beams strengthened by CFRP increased by a maximum percentage of up to 111.7% compared to the unstrengthened beam. Also, it is found that by increasing the compressive strength of concrete from 40 MPa to 65 MPa the load-carrying capacity increases by 28% and the stiffness also increased, while the decrease of shear span to depth ratio from 1.66 to 2.33 leads to increasing the shear capacity by 23%. The maximum load of beam strengthened with U shape increased by up to11.5% when compared with the same beam strengthened with two side bond shapes of CFRP. However, the gain in the strength was reached to 22.7% for beams strengthened with CFRP laminate compare to unstrengthened beams. The strengthening of RC beams by CFRP laminates using the near surface mounted (NSM) technique is more efficient than the externally bonded reinforcement (EBR) technique for all beams in the shear behavior. The finite element models provide a good level of accuracy compared to experimental results and ACI-440.
The main purpose of fiber reinforcement in concrete is to increase the post-cracking resistance of the composite, which reflects on toughness gain, being steel fibers traditionally used for this purpose. In recent years, an alternative to the steel fibers has emerged in the market for concrete reinforcement: the macro-polymeric fiber. However, there is few research on its performance as a reinforcement element in concrete, particularly when it is a high strength concrete. Given this, the behavior of high strength concrete, without fiber and with macro-polymeric fiber, both in fresh and hardened state, is analyzed in this paper. The workability was evaluated by the slump test and the mechanical properties were evaluated by the tests of compressive strength, Barcelona, flexure of prisms and punching of plates. It was found that, depending on the property to be analyzed, the increase of the macro-polymeric fiber content may be unfeasible. In the flexural test in prisms, for example, most parameters evaluated showed no significant changes when increasing the fiber content. In addition, it was observed that the same concrete mixture may present different behavior depending on the test performed.
In recent years, ideas such as green roofs gained importance as an alternative for environmental adaptation of society to new ambient conditions. In Bogotá city, the roofs at popular neighborhood represent a potential area for their implementation. This present research discusses how the weight of a green roof impacts a self-construction dwelling unit from a structural capacity demand point of view. Green roof weight is a random variable whose normality was investigated through the Shapiro-Wilk goodness of fit. The magnification factors for this dead-like load come from the Nowak-Collins method using the confidence intervals on the mean weight value. The ATC-40 pushover methodology helped in finding the non-linear behavior of a controlled but similar structure as those found in the popular neighborhoods of Bogotá city. According to this methodology, damage caused on these structures due to seismic demand increases by the green roof incorporation. However, damage increase is a function of local soil conditions.
Non-linear dynamic analyses methods generally provide a more adjusted modeling of the structural response for strong seismic events. Such a dynamic seismic non-linear evaluation took place for six buildings: two 5 story-height, two 12 story-height and two 20 story-high and with a regular configuration. The structural systems of the buildings complied to the NSR-10 (Colombian earthquake resistant standard) and with the seismic microzoning of Bogotá.
The analysis done to the previous structures used non-linear methodologies along with two time- histories corresponding to two well recorded earthquakes: Quetame earthquake circa 2008 and the Mesa de los Santos earthquake circa 2015. Said events characterized by records at Bogotá D.C. by the RAB (network of accelerometers of Bogotá). A structural evaluation using the nonlinear approach of a finite element software and following the FEMA 356 guidelines, the structural response to 81 seismic signals from the Mesa de los Santos earthquake and 78 from the Quetame earthquake helped in understanding the simulated behavior. Said signals included three perpendicular ground movements corresponding to the north-south, east-west and vertical directions. With the results of the non-linear dynamic analysis, plastic hinges helped in understanding the nonlinear structural response when the earthquakes hit separately. Based on the results, sway maps showing the results in the Y and X directions, clustered the most affected areas of the city. At the same time, a thorough analysis of moment connections at the first floor, at an intermediate floor and at the last floor of the buildings showed the capacity of the original design.
The results suggest that steel buildings have a better structural performance when compared with reinforced concrete buildings that were also analyzed (nonlinear analysis) with real earthquake (in soft soils) in previous investigations.
City dwellers in South America suffer thermal discomfort inside the buildings because of climate change, a situation that directly affects their health. Resilient design addresses this issue as a response thereto. The objective of the article is to evaluate resilient design characteristics responding to the need for thermal comfort in social housing with regard to the effect of climate change. This was carried out through a theoretical and an empirical stage in two South American cities with opposite characteristics: Passo Fundo in Brazil and Tunja in Colombia. As a result, it was found that CEB is a viable option only in climates with specific conditions given its thermal and environmental properties, according to direct heat gain strategies that tend to be resilient and fit a bioclimatic urban design better. Considering the above, it was concluded that the envelope plays a key role in resilient design in terms of thermal comfort.
In the Aran Valley there is a group of Romanesque churches built between the 11th and 13th centuries characterised by their large deformations, in some cases exceeding 7% of their original condition. The research shows the results of the geometric study carried out with a Terrestrial Laser Scanner (TLS), revealing geometric differences with regard to the traditional definition of barrel vault. The deformations of the initially anti-funicular vaults are sometimes transformed into convex funicular shapes, where the final spatial volume is smaller than the initial one, despite the fact that the linear length of the curve and surface of the vault is greater than that of their original condition.
Ecuadorian asphalt has the particularity of being prone to premature aging; therefore, the asphalt pavements have insufficient durability. The objective of this experimental work is to assess the effect that a modification with the rejuvenating agent Sylvaroad RP-1000 produces on the properties of AC 20 asphalt from the Esmeraldas Refinery, as well as evaluating its impact on the quality of a typical asphalt mix, without reclaimed asphalt pavement, prepared with modified and unmodified asphalt. The asphalt used is also classified as PG 64-22 and when mixed with 2.5% by weight of the rejuvenator, the grade changed to PG 58-28. Additional studies were carried out using the ΔTc, Glover-Rowe parameters and the corresponding transition temperatures, showing improvements in the results. At that point, a dense mix with 5.5% asphalt was designed. Stiffness modulus, cyclic compression and fatigue modulus tests were applied with the NAT equipment to the specimens. When using modified asphalt, the fatigue behavior improved remarkably. Additionally, an aging process in oven at 85 ° C was applied to both mixtures, measuring the stiffness modulus and fatigue at 8 days, which demonstrated an adequate behavior only in the mixture made with rejuvenator.
A Structures Assessment Methodology is presented, complementary to the Visual Inspection, which allows, through on-site non-destructive testing (NDT), to deliver as a result a comprehensive quantitative evaluation of the "Structural Health" of the different elements. This allows essential information to adjust maintenance cycles or make timely based decisions in critical situations, in order to guarantee future performance. The proposed methodology considers the execution of NDT to determine the state of the reinforcement, the characteristics of the concrete cover, and the presence of cracks. By means of the extraction of cores of smaller size (1”) the ingress of carbonation or chlorides is determined. The results measured on-site are weighted to determine a Deterioration Index DI. The aggressiveness of the environment is included through an Environmental Exposure Index EEI. The incorporation of the results to the CTK-ConDiag Model allows the combination of both indices, obtaining a Structure Global Deterioration Level SGDL, which measures the degree of damage determined at 6 levels. The proposed methodology is presented with the results of the study carried out on two specific bridges in Chile under different climatic conditions.
Due to its fast and economical execution, the geotechnical solution known as soil nailing walls is widely used for the stabilization of slopes and ground excavations. At the design stage, verification of the external stability of the soil nailing wall is one of the most important acceptability criteria. The main objective of this work is to evaluate the external stability of soil nailing walls, considering the variability influence of their height and the geomechanical parameters of the soil in-situ. The probabilistic 2k factorial design methodology has been applied to generate 32 experiments. A vertical soil nailing wall, with variable height, under pseudo-static load conditions, and executed in residual soil from granitic rock has been used as a prototype model. Based on the analysis of the observations of the 32 experiments, three regression models have been developed, which can be used to predict the value of the factors of safety with arbitrary realizations. Furthermore, the observations show that the factors that most influence the external stability of soil nailing walls are the height of the wall, the cohesion and the friction angle of the soil in-situ.
PDF
(1MB)
PDF
(14MB)
