Browsing by Author "Almazán, J.L."

Now showing 1 - 6 of 6
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    A simplified approach to assess the technical prefeasibility of multistory wood-frame buildings in high seismic zones
    (2022) Berwart, S.; Estrella, X.; Montaño, J.; Santa-María, H.; Almazán, J.L.; Guindos Bretones, Pablo
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    Cyclic behavior of wood-frame shear walls with vertical load and bending moment for mid-rise timber buildings
    (2021) Orellana, P.; Santa María, H.; Almazán, J.L.; Estrella, X.
    In light wood-frame buildings, the gravitational and lateral force-resisting systems are composed of floor diaphragms and shear walls. During an earthquake, these walls are subjected to the simultaneous action of in-plane vertical force, shear force, and in-plane bending moment. In a mid-rise building, these internal forces can reach large magnitudes, especially on the lower stories, and could have an important influence on the lateral behavior of the walls. The historical use of light wood-frame construction has been in low-rise buildings. Consequently, few investigations have analyzed the effects of high gravitational forces or in-plane bending moment on the lateral behavior of wood shear walls designed for multi-story buildings. This paper presents an investigation of the cyclic lateral behavior of light wood-frame shear walls, designed for mid-rise buildings, subjected to large axial compressive load and in-plane bending moment. Eight wall specimens were experimentally tested with a cyclic lateral displacement protocol, a constant compressive load, and a cyclic in-plane bending moment. The effects of axial compressive load and in-plane bending moment were analyzed. Also, the wall length and the spacing of sheathing nails were varied to study the effects of these variables on the response. A numerical study was performed to show how these effects could influence the response of mid-rise timber buildings. An improvement in the lateral performance of the walls was observed compared to walls tested without compressive force nor bending moment, showing an increase in stiffness, load-carrying capacity, and dissipated energy.
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    Development of an amplified added stiffening and damping system for wood-frame shear walls
    (2020) Montaño, J.; Maury, R.; Almazán, J.L.; Estrella, X.; Guindos Bretones, Pablo
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    Experimental study of the effects of continuous rod hold-down anchorages on the cyclic response of wood frame shear walls
    (2021) Estrella, X.; Malek, S.; Almazán, J.L.; Guindos, P.; Santa María, H.
    When designing mid-rise wood frame buildings in high seismicity areas, overturning moments induce large tensile forces in the anchoring system that cannot be resisted by conventional discrete hold-downs. To address this issue, continuous rod hold-downs are used instead to transfer the generated tensile loads to the foundation. However, investigations on the lateral response of wood frame walls employing this anchorage system are quite limited. This paper presents an experimental-numerical study aimed at providing a better understanding of the response of such walls under lateral loads. Four specimens with different configurations were tested under lateral cyclic load, and their behavior was compared with that of walls with discrete hold-downs. Results showed that employing the continuous rod system increases the wall strength by 35.8%, with the specimens behaving elastically up to drifts of about 0.8%. The walls exhibited a marked stiffness degradation during the tests, keeping a residual value of about 15-20% of the initial stiffness. Further analyses showed that the Special Design Provisions for Wind and Seismic (SDPWS) guidelines underestimate the wall strengths by 39.9% and overestimate the stiffnesses by 37.5%, on average. Finally, a nonlinear model was developed to investigate the specimens of this research in depth, showing a special failure pattern that concentrates the damage in the nails located at the central studs of the wall.
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    Ground motions for FEMA P-695 application in subduction zones
    (2019) Estrella, X.; Guindos Bretones, Pablo; Almazán, J.L.
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    Seismic performance factors for timber buildings with woodframe shear walls
    (2021) Estrella, X.; Guindos, P.; Almazán, J.L.; Malek, S.; Santa María, H.; Montaño, J.; Berwart, S.
    Seismic performance factors are an engineering tool to estimate force and displacement demands on structures designed through linear methods of analysis. In Chile, the NCh433 standard provides the regulations, requirements, and factors for seismic design of several structural typologies and systems. However, when it comes to wood frame structures, previous research has found that the NCh433 provisions are highly restrictive and result in over-conservative designs. Therefore, this paper presents an experimental and numerical investigation aimed at proposing new, less restrictive seismic performance factors for wood frame buildings. Following the FEMA P-695 guidelines and a novel ground motion set for subduction zones, this research embraced: (1) testing of several full-scale specimens, (2) developing of detailed and simplified numerical models, and (3) analyzing the seismic performance of a comprehensive set of structural archetypes. 201 buildings were analyzed and results showed that changing the current NCh433 performance factors from R = 5.5 & Delta(max) = 0.002 to R = 6.5 & Delta(max) = 0.004 decreases the average collapse ratio of wood frame structures by 13.3% but keeps the collapse probability below 20% for all the archetypes under study. Besides, it improves the cost-effectiveness of the buildings and enhances their competitiveness when compared to other materials, since savings of 40.4% in nailing, 15.9% in OSB panels, and 7.3% in timber studs were found for a 5-story building case study. Further analyses showed that the buildings designed with the new factors reached the "enhanced performance objective" as defined by the ASCE 41-17 standard, guaranteeing neglectable structural and non-structural damage under highly recurring seismic events. Finally, dynamic analyses revealed that the minimum base shear requirement Cmin of the NCh433 standard is somewhat restrictive for soil classes A, B, and C, leading to conservative results compared to archetypes where the Cmin requirement did not control the structural design.