Browsing by Author "Calderón Díaz, Sebastián Andrés"

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    A detailed experimental mechanical characterization of multi-perforated clay brick masonry
    (2023) Calderón Díaz, Sebastián Andrés; Sandoval Mandujano, Cristián; Araya Letelier, Gerardo Andrés; Aguilar, Víctor
    Multi-Perforated Clay Bricks (MPCLBs) are widely used in the construction of modern masonry structures worldwide, including earthquake-prone areas. However, few experimental studies have been carried out aimed at performing a detailed mechanical characterization of their behavior under different loading conditions. In the present paper, tests on masonry constituent materials and assemblages (triplets, rectangular prisms, and panels) made of MPCLBs are carried out, and some relationships between masonry properties useful for design purposes or numerical simulations are derived, including compression strength, Young's modulus, shear strength, and shear modulus. From the results, it is observed that decreasing mortar compressive strength and increasing joints' height are detrimental to masonry properties. Furthermore, a masonry compressive strength equation is fitted to the test results representative of Chilean masonry construction, which significantly overperforms the current Chilean standard formula. Also, digital image correlation is used to confirm the effect of mortar entering bricks' perforations on the shear response of the mortar-brick interface.
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    Detailed micro-modeling of partially grouted reinforced masonry shear walls: extended validation and parametric study
    (2021) Calderón Díaz, Sebastián Andrés; Sandoval Mandujano, Cristián; Milani, Gabriele; Arnau, Oriol
    Partially grouted reinforced masonry (PG-RM) shear walls have been widely used as structural elements in low- and medium-rise earthquake-resistant buildings. Nonetheless, assessing its shear strength represents a complex task mainly because the partial grouting provides a non-constant cross section, which results in heterogeneous stress–strain patterns. Consequently, refined modeling techniques are needed to reproduce local failure mechanisms taking place in these walls, which significantly influence the global response. In response to this issue, a detailed micro-modeling approach based on the finite element method was proposed in previous studies by the authors. Although the numerical strategy provided accurate results, further validation is required. Therefore, in this study, the experimental results of seven PG-RM shear walls of multi-perforated clay bricks with bed-joint reinforcement are employed as validation cases. These seven walls presented variations in five design parameters. The validated numerical model was then employed to perform a parametric study to assess the influence of the wall aspect ratio, axial pre-compression stress, and horizontal reinforcement ratio on the in-plane lateral behavior of PG-RM shear walls. The obtained results show that the three studied design parameters modified the crack patterns of the walls. Besides, increasing the axial pre-compression stress or reducing the aspect ratio resulted in higher walls’ shear strength. Additionally, decreasing the horizontal reinforcement ratio or increasing the aspect ratio generated a higher story-drift ratio at maximum lateral force. Finally, it was corroborated that the positive effect of the axial pre-compression stress on the walls’ shear strength decreases inversely proportional to the aspect ratio.
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    Influence of different design parameters on the seismic performance of partially grouted masonry shear walls
    (2021) Calderón Díaz, Sebastián Andrés; Sandoval Mandujano, Cristián; Araya Letelier, Gerardo Andrés; Inzunza, Ernesto; Arnau, Oriol
    In recent earthquakes in Chile (e.g., Maule’s 2010 earthquake), buildings built with bed-joint partially grouted reinforced masonry (BJ-PG-RM) shear walls made of multi-perforated clay bricks (MPCB) have not collapsed, although significant damages have been reported. Additionally, experimental data on the influence of the different design parameters that control its seismic behavior is scarce, and the available expressions for estimating their lateral resistance are inaccurate. To address these issues, nine full-scale BJ-PG-RM walls made of MPCB were tested under axial pre-compression and cyclic lateral loads. The study addressed the influence of the aspect (height-to-length) ratio, axial pre-compression, mortar compressive strength, mortar joints’ thickness, bricks’ height, and horizontal and vertical reinforcement ratio. The results were analyzed in terms of hysteretic response, damage evolution, seismic performance parameters (shear strength, equivalent viscous damping ratio, ductility, and lateral stiffness degradation). All designed walls failed in a diagonal tension failure mode. Besides, all studied variables influenced the stresses and crack patterns. Also, the shear strength increases when: (i) lower aspect ratio or joint thickness are used; and (ii) higher axial load ratio, horizontal reinforcement ratio, vertical reinforcement ratio, or mortar compressive strength are used. Moreover, when damage progresses, the lateral secant stiffness decays faster as a result of: (i) larger joint thickness or vertical reinforcement ratio; (ii) lower mortar compressive strength. Most walls exhibited an equivalent viscous damping ratio between 5% and 10% for an intermediate state of damage. However, the evaluated design parameters did not considerably affect the development of the viscous damping ratio as a function of the drift ratio. The displacement ductility of the walls ranged from 1.5 to 2.5, where the height of bricks and the vertical reinforcement ratio had positive effects, and the joint thickness, the mortar compressive strength, and the horizontal reinforcement ratio a negative effect. The lateral resistance of tested walls was also estimated with six expressions, but none of them provided accurate results.
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    Quasi-static testing of concrete masonry shear walls with different horizontal reinforcement schemes
    (2021) Calderón Díaz, Sebastián Andrés; Sandoval Mandujano, Cristián; Araya Letelier, Gerardo Andrés; Inzunza, Ernesto; Milani, Gabriele
    Constructions built with partially grouted reinforced masonry (PG-RM) shear walls are common in several countries, and consequently, different construction solutions can be expected. In this context, one of the main differences detected is the type of horizontal steel reinforcement used. The most traditional options consist of bed-joint reinforcement and bond-beam reinforcement. Despite the advances in this research area, there is little experimental evidence to determine which of these horizontal reinforcement schemes exhibits a superior performance under seismic loads. Thus, the research described in this paper focused on assessing and comparing the seismic performance of PG-RM shear walls with different horizontal reinforcement options. For this purpose, four concrete masonry walls with an aspect ratio of 0.86 were tested undergoing constant axial pre-compression and quasi-static cyclic incremental lateral displacements. The tested walls had the same horizontal reinforcement ratio but different layouts (only bed joint reinforcement, only bond beam reinforcement, and a combination of them). The other design characteristics remained constant. The obtained results were analyzed in terms of the force-displacement curves and seismic performance parameters such as the maximum resistance, stiffness decay, energy dissipation, and equivalent viscous damping ratio. In addition, a comparative analysis of damage progression of the tested walls was carried out using the digital image correlation (DIC) technique. The tested walls experienced progressive deterioration of the lateral stiffness in proportion to drift increments regardless of the reinforcement scheme. Once achieved the lateral resistance, the degradation of the behavior accelerated, turning into a rather unpredictable response. Employing different horizontal reinforcement layout showed no influence on the lateral capacity of the walls when the same horizontal reinforcement ratio and material qualities are used. It was also observed that the distributed bed-joint reinforcement was better than the bond-beam reinforcement layout in controlling crack widths. Additionally, a combination of bond-beams and bed-joint reinforcement seems to be the most suitable reinforcement strategy based on hysteretic behavior, energy dissipation capacity, and ductility. The presented experimental evidence is promising, although further studies are required in order to promote its use in design codes and construction projects.
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    Seismic behavior of partially grouted masonry shear walls containing openings: Experimental testing
    (2023) Vargas Carvajal, Laura Andrea; Sandoval Mandujano, Cristián; Bertolesi, Elisa; Calderón Díaz, Sebastián Andrés
    This article presents an experimental study aimed at understanding the effect of openings on the seismic response of partially grouted reinforced masonry (PG-RM) walls. For this purpose, four full-scale PG-RM walls with different opening sizes were built and tested under the combined action of constant axial compression and cyclic lateral loading. All the specimens had the same external dimensions. The effect of openings was assessed in terms of wall hysteresis and force–displacement curves and the quantification of different seismic parameters such as shear capacity, degradation of lateral stiffness, energy dissipated, equivalent viscous damping ratio, and displacement ductility. A 2D Digital Image Correlation (DIC) system was implemented to monitor principal strain fields and cracking patterns during the tests. The paper also includes the assessment of the shear capacity of the tested walls according to three existent approaches developed for in-plane shear panels, which rely on the definition of an effective height of piers. The results indicate that the shear capacity of the walls decreased when the aspect ratio of the piers increased. From DIC analysis results, it was observed that damage extended beyond piers also covering spandrels and that directionality of shear loads played a fundamental role in the damage development. Therefore, the identification of the pier’s effective height and direction of seismic loads should be incorporated into the estimation of the shear capacity. Finally, the performance of the selected shear expressions and different approaches to estimate the effective height of the piers was evaluated. It was concluded that the most accurate approach was to define an effective piers height according to Augenti (2006)’s proposal using the Calderón et al. (2022) shear expression to assess piers’ lateral resistance.
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    Seismic strengthening of partially grouted masonry walls with openings: Evaluation of ferrocement and BTRM solutions
    (2024) Pérez Pinedo, Luis Elías; Sandoval Mandujano, Cristián; Alvarado Funes, Rolando José; Vargas Carvajal, Laura Andrea; Calderón Díaz, Sebastián Andrés; Bernat, Ernest
    This paper presents an experimental study on the seismic performance of partially grouted reinforced masonry (PG-RM) walls strengthened with two solutions: Ferrocement coating (welded wire steel mesh embedded in cementitious mortar, WWM) and Basalt Textile Reinforced Mortar (BTRM) layer. For this purpose, two full-scale walls were built with hollow concrete units, with identical geometry and construction details of a previously reported tested wall, which acts as the control specimen (unstrengthened case) in this study. The walls, with a window-type opening and another door-type opening, were strengthened on one of their sides and tested under the combined action of constant axial compression and cyclic lateral loading up to failure. The experimental results show that both strengthening solutions increased the investigated walls' initial stiffness and lateral capacity. The increase in lateral capacity of both solutions was similar, about 37%. The 2D-DIC analysis implemented during the tests was instrumental in highlighting the areas on the strengthened walls where high strains were developed. The damage registered on the BTRM layer was more consistent with what was observed on the surface of the unstrengthened wall. Meanwhile, the damage reported on the wall strengthened with WWM did not exhibit apparent damage at higher drift levels due to the detachment between the ferrocement coating and the masonry substrate. Finally, the performance of some procedures to compute the contribution of the studied strengthening solutions was also assessed.
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    Shear design equation and updated fragility functions for partially grouted reinforced masonry shear walls
    (2022) Calderón Díaz, Sebastián Andrés; Vargas Carvajal, Laura Andrea; Sandoval Mandujano, Cristián; Araya Letelier, Gerardo Andrés; Milani, Gabriele
    This paper proposes specific ultimate shear strength expressions for partially-grouted reinforced masonry (PG-RM) shear walls that are bed-joint reinforced (BJR) and made with either multi-perforated clay bricks (MPCLBs) or hollow concrete blocks (HCBs). For each unit type, a set of constant coefficients of an arbitrary mathematical expression is optimized to minimize the error against experimental databases of walls made with the same unit types. Additionally, the assembled databases are employed to calculate lognormal empirical fragility functions, following performance-based earthquake engineering (PBEE) methodologies. For this, two different engineering demand parameters (EDPs) (story drift ratio, SDR, and normalized diagonal shear demand, NDSD) are proposed, and two damage states (DS) (named DS4 for moderate damage and DS5 for severe damage) are investigated. The proposed shear formulae are used in the normalization of calculated NDSD values. Moreover, databases are sorted by a selected design parameter (aspect ratio) to calculate design parameter-sensitive fragility functions. Overall, the results indicate that the proposed expressions are more accurate than the corresponding expressions proposed by the American and Canadian codes when assessing BJR-PG-RM shear walls in terms of the average error and dispersion of relative prediction error. All the fragility curves adjusted to the whole database pass the Lilliefors goodness of fit test (). Comparing SDR-based curves of walls of a different unit type, DS4 curves present a smaller difference in the median value () than DS5 curves. Additionally, the variations in the of NDSD-based curves of walls of different units are smaller than those observed in SDR-based fragility functions, indicating that NDSD represents a less variant EDP to describe the probability of shear damage at DS5 when a proper expression is employed for the normalization. Regarding design parameter-sensitive fragility functions, sorting databases reduces the number of data points used to calculate the functions, which produced two SDR-based and one NDSD-based function to fail the Lilliefors test (). In general, the value of SDR-based curves increases in proportion to the aspect ratio. Additionally, classifying the databases by a design parameter (aspect ratio) corroborated that the proposed expression has acceptable accuracy based on the adjusted NDSD-based DS5 fragility functions. It is highlighted that calculating design parameter-sensitive functions might increase the accuracy of PBEE assessments (e.g., loss estimations) when an EDP insensitive to design parameters normalization (e.g., SDR) is employed.
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    Simplified micro-modeling of partially-grouted reinforced masonry shear walls with bed-joint reinforcement: Implementation and validation
    (2021) Calderón Díaz, Sebastián Andrés; Milani, Gabriele; Sandoval Mandujano, Cristián
    Partially grouted reinforced masonry (PG-RM) shear walls of hollow concrete blocks (HCB) have been an object of study during the last years. The non-constant cross-section of this type of structural element and the presence of reinforcement set a challenging scenario when assessing their lateral resistance. This scenario makes simple approaches (e.g., design expressions) lacking accuracy. Besides, the most accurate existent analysis methodologies rely on user-defined sub-routines that are not available for commercial use. Therefore, proper analysis methodologies are still a need. In this regard, this research aims at reproducing the behavior of PG-RM shear walls with bed-joint reinforcement with a simple but also accurate approach. In this line, the in-plane behavior of PG-RM shear walls was reproduced by implementing 2D micro-models in a multi-purpose commercial FE code without requiring excessive work, advanced programming skills, and unaffordable hardware. The model approach was validated by reproducing two identical full-scale PG-RM shear walls. Although the model was not able to reproduce cyclic loading as in the tests, the model captured the experimental failure mode and lateral resistance with an acceptable degree of accuracy. Moreover, the distribution of cracks and deformations in horizontal reinforcement elements were appropriately reproduced at the lateral resistance, indicating the most demanded reinforcement portions. Additionally, the proposed modeling approach was compared with two alternative approaches: a 2D model that reproduced tensile failure employing interfaces and a smeared crack model and a 3D model that reproduced tensile failure utilizing a smeared crack model. The benchmark results pointed out the advantages of the reference model over the alternative modeling approaches. The first alternative model reproduced an excessive displacement capacity, and the second alternative model simulated an inaccurate crack pattern and was associated with a heavy computational burden.
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    Structural feasibility of timber-structured vertical expansions for social housing buildings in Chile
    (World Conference on Timber Engineering (WCTE), 2018) Schmitt Rivera, Cristián; Calderón Díaz, Sebastián Andrés; Cárcamo Chávez, Sebastián; Sandoval Mandujano, Cristián; Chateau Gannon, Francisco; Martínez Torres, María Paula
    In this paper, the structural feasibility of expanding existing social housing buildings structured in reinforced concrete (RC) using timber structures is investigated. For this purpose, a 4-story housing block massively built throughout Chile - known as CORVI 1010 housing block-is selected as a case study. The proposal considers a 2-story platform frame expansion. The results show that timber-structured expansions have low impact on existing buildings, minimal increase on design stress and that strengthening of the original structure is not required.