Browsing by Author "Gallegos, Marco"

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    Comparative seismic collapse assessment of Chilean code-conforming RC dual wall-frame buildings
    (Earthquake Engineering Research Institute, 2022) Gallegos, Marco; Araya Letelier, Gerardo Andres; López-García González, Diego; Parra Torres, Pablo Fernando
    Although the satisfactory performance of Chilean buildings in terms of collapse prevention is widely recognized, there is a need to quantify the actual collapse probability and level of protection provided by current seismic codes. In this study, the collapse potential of code-conforming reinforced concrete dual wall-frame buildings subjected to subduction earthquakes was assessed. A suite of four 16-story archetypes, located at two different seismic zones and on two different soil types, was evaluated considering the latest developments in performance-based earthquake engineering through incremental dynamic analyses of 3D nonlinear models. It was found that the probability of collapse in 50 years is in all cases less than the 1% ASCE 7 target probability, which is consistent with the adequate collapse performance of reinforced concrete buildings that has been observed in recent strong earthquakes (Mw ≥ 8.0) in Chile. It was also observed, however, that the collapse probability is not uniform but strongly influenced by the soil type. This observation suggests that the design response spectra indicated by the Chilean seismic design code for buildings might not correctly account for the influence of the soil type.
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    Influence of statistical approaches on structural collapse potential assessment
    (Earthquake Engineering Research Institute, 2022) Gallegos, Marco; Araya Letelier, Gerardo Andrés; Lopéz-García González, Diego
    Structural collapse estimations could be influenced by alternative statistical methodologies that can be chosen throughout the seismic risk assessment of buildings, specifically in the generation of collapse fragility functions. This research evaluates the impact of selecting different statistical methods on the collapse potential metrics of a reinforced concrete dual wall-frame building as a case study. The explored methods are related to the identification and replacement of unusual observations in the simulated collapse data, and the selection of different probability functions (PFs) to characterize the collapse fragility. According to the results, this mid-rise building showed an acceptable Life Safety risk in accordance with ASCE 7 targets, regardless of the PF. However, the probability of collapse in 50 years obtained using the Weibull PF could be 2.6 times the value obtained using the lognormal PF. This observation is due to the larger probability of collapse values exhibited by the Weibull PF at small-to-medium Sa(T1) intensities that are associated to higher mean annual frequency of exceedance. In addition, it was also found that excluding extreme collapse values reduced the dispersion in the fragilities and it had a non-negligible impact on the collapse probabilities for this case study building.
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    Numerical Study on Cyclic Response of End-Plate Biaxial Moment Connection in Box Columns
    (2020) Gallegos, Marco; Nunez, Eduardo; Herrera, Ricardo
    The 2008 Wenchuan-China earthquake showed the importance of considering the bidirectional seismic action as a cause of failure in column hinge mechanisms. Subsequently, the large 2011 Tohoku-Japan earthquake revealed that Special Moment Frames buildings, made of tubular columns (Hollow Structural Section or Built-up Box Section) and rigid connections with I-beams, did not suffer serious damage. However, only the ConXtech((R)) ConXL (TM) moment connection has been prequalified according to the (American Institute of Construction) AISC Seismic Provisions for use with tubular columns and the rest of connections do not consider biaxial resistance. The research reported herein investigated the cyclic response of box-columns joints, connected to I beams using the four-bolt extended endplate connection, subjected to bidirectional bending and axial load on the column. To conduct the study, complex nonlinear finite element models (FEMs) of several I beam to box column joint configurations were constructed and analyzed under cyclic loading using the ANSYS software. The results reveal that the failure is concentrated in the beams of all joint configurations except for the columns with axial load equal to 75% of the column capacity, where a combined failure mechanism is achieved. The energy dissipation capacity of joints with a greater number of beams is lower than joints with fewer beams. The bidirectional effect of the seismic action and the level of axial load must be considered to avoid the formation of a column-hinge fragile failure mechanism also the behavior exhibited by 3D joints is more realistic than 2D joints according to real structures.