Browsing by Author "Maureira, Nelson"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Implementation of elastomeric seismic isolation in tall buildings considering axial-lateral coupling in the isolators
    (National Information Centre of Earthquake Engineering, 2017) Maureira, Nelson; Llera Martin, Juan Carlos de la
    Seismic isolation of high-rise buildings presents an opportunity but also a challenge to seismic isolation, a technique mostly used in the past in low and moderate-rise buildings. It turns out that under certain conditions of the structure and input, it is perfectly reasonable to protect tall structures using seismic isolation. The objective of this research is to explore these conditions in simple structural models. A parametric analysis on seismically isolated tall buildings was performed using first a simplified representation of the superstructure as a 3D rigid rectangular prism, geometrically characterized by its height and aspect ratio in plan and height. The elastic properties of the isolation system were lumped at the isolation interface by assuming circular elastomeric devices connected to the nodes of a regular grid at the base. The energy dissipation of the isolation devices was incorporated by assigning a constant damping ratio to the six degrees of freedom of the model. The results of this linear elastic model help identify problems of rocking at the base and tensile loads on the isolators in some cases. The results obtained from the rigid body model for the building were extended to a second parametric model that considers finite stiffness on the superstructure. For the sake of simplicity, 2D non-linear analyses were performed with focus on the isolator tensile loads and the building inter-story drifts. Two building models were considered, a simple frame with three column axes, and a mixed frame with a central wall. The Koh & Kelly non-linear two-spring model was used to characterize the isolators. The results of this analysis show that it is possible to implement seismic isolation in buildings with height-to-base aspect ratio of up to 6:1 without excessive tensile loads on the isolators if theoretical isolation periods go over 6s. Additionally, in these tall and slender buildings, the inter-story displacement reductions decrease with aspect ratio. Also, base shear and floor accelerations are reduced in tall and slender buildings, but the reduction is less significant than the reduction obtained for the relative lateral displacement and drifts.
  • No Thumbnail Available
    Item
    Innovative use of copper mine tailing as an additive in cement mortar
    (2023) Arunachalam, Krishna Prakash; Avudaiappan, Siva; Maureira, Nelson; Garcia Filho, Fabio Da Costa; Monteiro, Sergio Neves; Batista, Isabela Devesa; de Azevedo, Afonso R. G.
    This research assesses the feasibility of recycling copper mine tailings (CMT) by analyzing the durability and mechanical characteristics of cement mortar using these tailings as filler additives. CMT are mineral wastes generated during the process of mining. In this work, specimens of cement mortar were incorporated with up to 30 wt.% of a CMT. Bulk density, dynamic modulus of elasticity, apparent density, ultrasonic pulse velocity, flexural and compressive strengths tests were evaluated. Total amount of voids, sorptivity, water ab-sorption and chemical resistance tests were also obtained to evaluate the mortar durability. When 10 wt.% CMT was incorporated, overall amount of voids in the mortar was reduced by 20% and mechanical performance was improved by 16% after 28 days. The flexural strength of the mortar was also found to increase, with the 20% wt.% CMT mortar incorporation reaching a flexural strength of 5.89 MPa. Thus represents 16% increase compared to the control 0% CMT strength. The results indicated that there was not a perfect correlation be-tween these results and the mechanical strength results for the 15 and 20 wt.% CMT mortars. In addition, the CMT acts as a protective barrier against harmful chemicals. The results of this research indicate that reusing CMT by incorporating into cement mortar is a feasible method for their recycling. Mortar made with as much as 15 wt.% CMT presented the same strength and durability as mortar with traditional sand and cement. (c) 2023 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).