Browsing by Author "Inzunza, Ernesto"

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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.