Browsing by Author "Lopez-Garcia, Diego"

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    Cyclic behavior and design methodology of exposed base plates with extended anchor bolts
    (2022) Torres-Rodas, Pablo; Medalla, Miguel; Zareian, Farzin; Lopez-Garcia, Diego
    This paper investigates the behavior of a ductile detail of exposed base plates. This detail consists of a base plate anchored to the concrete foundation through bolts extended to a steel chair configuration. The intention is to concentrate plastic strains mainly in the extended region of the anchor bolts, forcing the other connection components to remain elastic. The scientific background of this research consists of a series of sophisticated nonlinear finite element models subjected to a cyclic load protocol in the presence of an axial compressive force. The models were validated against an experimental test reported in the literature. Forces within the connection components, stresses, strain distributions, and deformation modes were examined. A total of sixteen three-dimensional nonlinear models were created using the ABAQUS simulation platform. The models were sepa-rated into two groups: the first consists of models with dimensions similar to the specimens tested in recent experimental programs reported in the past, while the second group simulates connections representative of mid-rise industrial frames. Building on the insights gained from the simulations of the first group, a methodology is proposed to design these column base connections. This suggested methodology is validated with the second group of simulations. Results indicate that the studied configuration detail presents some advantages compared with the traditional detail presented in Design Guide 1. For instance, plastic strains are developed almost exclusively in the anchor rods, and no damage is expected at the remaining components. Another essential characteristic is the exposed stretch length, with which it is possible to achieve a target design rotation without significant strain concentrations in the anchor rods. This characteristic facilitates post-earthquake inspections and repairs, and damage is virtually eliminated in the first story.
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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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    Seismic response of acceleration-sensitive nonstructural components in a Thin Lightly-Reinforced Concrete Wall (TLRCW) mid-rise building
    (2022) Obando, Juan Carlos; Arroyo, Orlando; Lopez-Garcia, Diego; Carrillo, Julian
    Experience in recent earthquakes has shown that Non-Structural Components (NSCs) in multi-story buildings exert a significant influence on economic losses. Different topics about the seismic behavior of NSCs have been investigated; however more research is needed in several areas such as the type of building structural system and the type of seismic hazard. Motivated by this observation, floor accelerations in a novel structural system, namely the Thin and Lightly-Reinforced Concrete Wall (TLRCW) building, are examined in this paper. The TLRCW system comprises thin and slender walls with deficient or nonexistent confinement at the wall edges, and web reinforcements made of welded-wire mesh with limited ductility. In this study, seismic demands on NSCs in a TLRCW building are analytically calculated and compared with current characterizations included in earthquake-resistant building codes and presented in the literature. Comparisons are performed in terms of peak floor accelerations, floor spectra, inelastic displacement ratios, and the still not completely characterized in-elastic absolute acceleration ratios. Influence of elastic and inelastic behavior of NSCs as well as of the structure is also evaluated. Since the TLRCW system is becoming common in some South American countries prone (in part or wholly) to subduction earthquakes, possible influence of the type of seismic hazard (i.e., crustal earthquakes or subduction earthquakes) is accounted for. It was found that, under design-level seismic demands, floor ac-celerations can be very large even though the structure undergoes a significant level of inelastic excursion. It was also found that floor accelerations are, for the most part, reasonably approximated by current characterizations. Finally, the type of seismic hazard has a negligible qualitative influence on floor accelerations (only minor quantitative differences were found).