Browsing by Author "Araya-Letelier, Gerardo "

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    Bayesian parameter and joint probability distribution estimation for a hysteretic constitutive model of reinforcing steel
    (2021) Birrell, Matias; Astroza, Rodrigo; Carreno, Rodrigo; Restrepo, Jose, I; Araya-Letelier, Gerardo
    With the structural design paradigm shift since the early 2000's from the traditional approach to performance based design (PBD), there has been a growing need for reliable nonlinear finite element (FE) models that can accurately predict the response of structures when subjected to extreme loads, such as earthquakes. In the case of reinforced concrete (RC) structures, a proper representation of the hysteretic nonlinear behavior of reinforcing steel becomes crucial in order to carry out nonlinear time history analyses. The Giuffre-Menegotto-Pinto (GMP) uniaxial steel constitutive law has been widely used by researchers and practitioners to model reinforcing steel bars. Despite the widespread in its implementation, a limited number of studies have proposed well-calibrated parameter values for this model. In addition, low identifiability of its governing parameters and the high cost of generating reliable experimental data have prevented a thorough probabilistic characterization of the GMP model parameters. Usually, only default parameter values from the early development of the model tend to be used. This paper uses experimental data from cyclic tests conducted on 36 reinforcing steel coupons manufactured in accordance to ASTM A615 and A706 Grade 60 reinforcing steel and proposes a joint probability density function (PDF) for the most influential parameters of the GMP material model. First, a local sensitivity analysis (LSA) is conducted to provide insight into the influence of each parameter in the model response. Also, global sensitivity analysis (GSA) is used to have a deep understanding of the composition of the variability in the model response due to parameter uncertainty and the level of interactions among parameters. The Bayesian approach is combined with the information obtained from GSA and LSA as input, to estimate model parameters and quantify the estimation uncertainties and propagate them to the material stress response. Uncertainty in model predictions obtained with the proposed PDF is assessed, and the impact of considering parameter correlations on the material response is investigated.
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    Carbonation and chloride penetration performance of self-compacting concrete with masonry and concrete wastes
    (2024) Silva, Yimmy Fernando; Izquierdo, Silvia; Delvasto, Silvio; Araya-Letelier, Gerardo
    In this research, masonry and concrete construction and demolition wastes (CDWs) were used as supplementary cementitious material (25% vol. residue of masonry, RM) and recycled coarse aggregate (RCA) in increasing levels (0%, 50% and 100% vol. residue of concrete), respectively, in the development of self-compacting concrete (SCC). The performance of SCC mixtures was evaluated in terms of fresh properties, compressive strength, resistance to both accelerated (1% CO2, 65% R.H. and 23 degrees C temperature) and natural carbonation as well as chloride penetration. Experimental results showed a monotonic workability reduction associated to the incorporation of increasing levels of RCA. In compressive strength, the SCC with RCA showed the greatest increase in this mechanical property after 28 days of accelerated exposure in the carbonation chamber, when compared to its water-cured counterpart. Yet, at 360 days of accelerated carbonation exposure, all SCCs showed compressive strength reductions compared to their water-cured counterparts. On the other hand, the chloride permeability resistance of the SCCs was low and very low at the ages evaluated. Thus, the findings of this study indicate that the use of CDW can generate SCCs with adequate fresh properties, compressive strength and carbonation and chloride penetration performance, which offers benefits for the environment.
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    Collapse Assessment of Mid-Rise RC Dual Wall-Frame Buildings Subjected to Subduction Earthquakes
    (2023) Gallegos, Marco F.; Araya-Letelier, Gerardo; López García, Diego; Parra, Pablo F.
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    Effect of mix dosage on rubberized concrete mechanical performance: a multivariable prediction model towards design provisions
    (2024) Guíñez, Felipe; Santa María, Hernán; Araya-Letelier, Gerardo; Lincoleo, Jocelyn; Palominos, Fabrizio
    The accumulation of end-of-life tires generates significant environmental/economic/social problems worldwide; however, these tires can potentially be used in engineering applications when recycled as crumb rubber (CR). One possibility is to use CR as a replacement for river sand in concrete to reduce the disposal of CR and the use of sand as well as to improve some of concrete’s properties, such as thermal performance and carbon footprint at the expense of some compressive strength reduction. In this study, a novel and simple multivariable model was developed to predict the compressive strength reduction of rubberized concrete (RC) based on a dataset of 287 concrete mixtures from 38 different studies. The approach used in this study quantified the significance of the impact of 10 mix design variables on the evaluation of compressive strength reduction. The final model proposed in this paper considers six explanatory variables (i.e., volume replacement of sand by CR, CR quantity, fine aggregate quantity, coarse aggregate quantity, cement quantity, and water quantity) to predict the compressive strength reduction in which a logarithmic transformation was implemented to achieve a more precise model. The proposed model reached a coefficient of determination of 0.89, significantly better than other existing models with which the proposed model was compared, resulting in a highly accurate and yet easy-to-implement model. Finally, practical design considerations were provided to be used in concrete mix design or the design of minor structural elements.
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    Flexural performance assessment of the effect of the splice length of the Jupiter ray type made of radiata pine using computer-aided design and computer-assisted manufacturing
    (2024) Veliz-Fadic, Felipe Ignacio; Rodriguez-Grau, Gonzalo; Marin-Uribe, Carlos Rodolfo; Garcia-Giraldo, John Mario; Gonzalez-Palacio, Liliana; Araya-Letelier, Gerardo
    The length of timber beams of restricted commercial lengths can be increased by carpenter splices, which requires a thorough characterization of the flexural performance of these beams. An experimental study was carried out addressing timber beams joined with Jupiter ray splices to identify the influence of height-to-length (h:l) ratios of the splices on the mechanical performance in terms of deflection and flexural capacity. Jupiter ray splices with height-to-length (h:l) ratios of 1:2, 1:3, 1:4, and 1:5 were manufactured using computer-aided design (CAD) and computer-assisted manufacturing (CAM). The flexural performance of the tested beams was characterized in terms of modulus of rupture (MOR), modulus of elasticity (MOE), inelastic stiffness (K-inelastic), mid-span deflection (delta), and shear modulus values, measured using a four-point bending test setup under pure bending. Results indicate that implementing these joints reduces the flexural performance compared to equivalent solid timber beams without carpenter splices. The ratio concerning solid beams varies in ranges of 12-24 %, 26-43 %, 57-71 %, and 21-35 % of the corresponding solid beams average MOR, MOE, delta, and K-inelastic values, respectively. Moreover, a high linear correlation was observed between the average values obtained at the bending tests with h:l ratios in this study. Finally, the predominant failure patterns are described, identifying the critical points of stress concentration.
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    Image-Based Automated Width Measurement of Surface Cracking
    (2021) Carrasco, Miguel ; Araya-Letelier, Gerardo ; Velázquez, Ramiro ; Visconti, Paolo
    The detection of cracks is an important monitoring task in civil engineering infrastructure devoted to ensuring durability, structural safety, and integrity. It has been traditionally performed by visual inspection, and the measurement of crack width has been manually obtained with a crack-width comparator gauge (CWCG). Unfortunately, this technique is time-consuming, suffers from subjective judgement, and is error-prone due to the difficulty of ensuring a correct spatial measurement as the CWCG may not be correctly positioned in accordance with the crack orientation. Although algorithms for automatic crack detection have been developed, most of them have specifically focused on solving the segmentation problem through Deep Learning techniques failing to address the underlying problem: crack width evaluation, which is critical for the assessment of civil structures. This paper proposes a novel automated method for surface cracking width measurement based on digital image processing techniques. Our proposal consists of three stages: anisotropic smoothing, segmentation, and stabilized central points by k-means adjustment and allows the characterization of both crack width and curvature-related orientation. The method is validated by assessing the surface cracking of fiber-reinforced earthen construction materials. The preliminary results show that the proposal is robust, efficient, and highly accurate at estimating crack width in digital images. The method effectively discards false cracks and detects real ones as small as 0.15 mm width regardless of the lighting conditions.
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    Seismic collapse performance of high-rise RC dual system buildings in subduction zones
    (2023) Gallegos, Marco F.; Araya-Letelier, Gerardo; Lopez-Garcia, Diego; Parra, Pablo F.
    The satisfactory 'collapse prevention' performance level of reinforced concrete (RC) buildings has been widely recognized during recent earthquakes in Chile. However, there is limited research on the actual level of seismic collapse protection. In this study, the seismic collapse behavior of high-rise RC dual wall-frame buildings representative of the Chilean inventory is quantitatively eval-uated. A suite of four 16-story structural archetypes was carefully selected and code-based designed assuming two different locations (i.e., high and moderate seismicity zones) and two different soil types (i.e., very stiff and moderately stiff soils). The archetypes were analyzed considering the latest developments in performance-based earthquake engineering implementing incremental dynamic analyses for 3D nonlinear models with sets of Chilean subduction ground motions. Results, expressed in terms of the probability of collapse conditioned on the Maximum Considered Earthquake (MCE) hazard level (<10%) and the collapse probability in 50 years (<1%), showed that all archetypes fully met the targets specified by ASCE 7 for an acceptable 'life safety' risk level. These results indeed explain why a very small number of RC building collapses was observed in the recent megathrust earthquakes (Mw>8.0) in Chile. Nevertheless, it was also found that the seismic collapse performance is not uniform, due mainly to the soil type. This observation suggests that the design spectra indicated by the Chilean seismic design code for buildings might need to be revised.
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    Shear behavior of single- and triple-thickness masonry panels strengthened by bed-joint structural repointing
    (2021) Sandoval, Cristián ; Serpell, Ricardo; Araya-Letelier, Gerardo ; Calderón, Sebastián
    Bed-joint structural repointing is a widely used strengthening technique in historic masonry constructions, particularly in applications where the material appearance needs to be preserved. Despite its wide use, limited research is available on the effectiveness of this technique in masonry elements of greater thickness subjected to in-plane shear loading. In the reported study, the shear behavior of single-and triple-thickness masonry panels strengthened with Near Surface Mounted (NSM) steel bars was investigated. Masonry panels were built following the material characteristics and bonding types of a reference case and tested in diagonal compression. Two lime-based mortar mixes with different compressive strength were employed to assess the effect of existing mortar quality on the strengthening technique performance. The investigated parameters were the number of courses with reinforcement in single-thickness panels, and the depth of the reinforcement and number of the faces reinforced in those of triple-thickness. The technique proved effective in improving the shear deformation capacity regardless of specimen thickness and, in panels of triple-thickness, both the eccentricity (result of reinforcing one or two faces) and depth of reinforcement were observed to significantly affect shear behavior. CO 2021 Elsevier Ltd. All rights reserved.
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    Short- and long-term experimental performance of concrete with copper slag: Mechanical and physical properties assessment
    (2024) Silva, Yimmy Fernando; Burbano-Garcia, Claudia; Araya-Letelier, Gerardo; Gonzalez, Marcelo
    Industrial waste management has increased in recent years and, at the same time, the production of more sustainable and high-performance concrete has become one of the most important challenges related to the built environment. To contribute to face the previously mentioned challenges, this paper presents an experimental study on the influence of copper slag (CS) as a supplementary cementitious material (SCM) on the physical and mechanical concrete performance at both short- and long -terms. The CS was incorporated to concrete using five increasing levels (0 %, 10 %, 20 %, 30 % and 50 % vol.) as SCM and both fresh state (slump) and hardened state (compressive strength, indirect tensile strength, flexural strength, porosity and capillary suction) properties of concretes were evaluated. The results showed that the highest slump was achieved by the concrete mixture with 50 % CS, reaching a 27 % increment compared to the reference concrete (0 % CS). In the hardened state, both average compressive and splitting tensile strength values monotonically decreased with increasing CS content at short ages (28 days). However, at 360 days, the 10 % SC concrete mixture presented average compressive and splitting tensile strengths of 57 MPa and 4.9 MPa, respectively, reaching and exceeding the corresponding strength values of the reference concrete, respectively. In addition, the mixture with 10 % CS obtained the highest average flexural strength, reaching a 3.2 % and 3.5 % increment compared to the reference mixture at 28 and 360 days, respectively, which might be attributed to the more angular shape of the CS particles compared to the cement particles. In terms of physical properties, voids and absorption values increased as the CS content increased, yet at 360 days of curing, the only concrete that presented higher values than the reference concrete was the mixture with 50 % CS (increments of 5.6 % and 5.4 % for voids and absorption, respectively). In conclusion, this study showed the advantageous potential use of CS as SCM at low percentages (between 10 % and 20 %), especially in long term performance of concrete mixtures.
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    The Future of Wood Construction: Opportunities and Barriers Based on Surveys in Europe and Chile
    (2022) Leszczyszyn, Ewa; Herajarvi, Henrik; Verkasalo, Erkki; Garcia-Jaca, Javier; Araya-Letelier, Gerardo; Lanvin, Jean-Denis; Bidzinska, Gabriela; Augustyniak-Wysocka, Dobrochna; Kies, Uwe; Calvillo, Alex; Wahlstromh, Margareta; Kouyoumji, Jean-Luc
    The demand for wood has increased in recent years due to new technical possibilities and environmental concerns. This paper provides an analysis of the factors that affect the use of wood in the construction sector, and an assessment of their importance in individual countries and for groups of stakeholders. The study covers the technical, societal, political, economic, and gender aspects of wood construction, with the aim of increasing global understanding regarding national differences, the current situation, and the potential for further development. The subject was investigated using a survey, and the most important opportunities for and barriers to growth in the use of wood in the construction sector were selected, following a statistical analysis. The results indicate strong regional and cultural differences regarding the acceptance of some of the opportunities and barriers related to the development of wood construction. The findings indicate that there is a need to promote wood construction based on its technical and economic benefits rather than its societal ones. On the other hand, the current societal barriers should be addressed as a priority, together with the establishment of common and harmonized policies. The results of this study, therefore, will contribute to the generation of regional-sensitive information that can be useful for policymakers when updating the building codes in their individual countries.