Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct Development and experimental behavior of HDR seismic isolators for low- rise residential buildings Ingrid E. Madera Sierra a,b, ⁎ , Daniele Losanno c , Salvatore Strano c , Johannio Marulanda b , Peter Thomson b a Departamento de Ingeniería Civil e Industrial, Pontificia Universidad Javeriana Cali, Calle 18 #118-250, Santiago de Cali, Colombia b Escuela de Ingeniería Civil y Geomática, Universidad del Valle, Calle 13 #100-00, Santiago de Cali, Colombia c Department of Structures for Engineering and Architecture, University of Naples, Federico II, 21 via Claudio, Naples, Italy ARTICLE INFO Keywords: Seismic isolation High damping rubber Fiber reinforced isolators Shear tests ABSTRACT Base isolation systems reduce the action of earthquakes on buildings by disconnecting the structure from the ground through different devices, being the steel reinforced isolators (SREIs) the most common used. However, due to the high initial costs of SREIs, this technique is mainly implemented in special projects and is rarely used for residential buildings in developing countries with high seismic risk. This paper presented a thorough in- vestigation on novel and unbounded rubber isolators which, based on the satisfactory behavior shown during experimental tests, could be a viable alternative to conventional isolators to be mainly implemented in Colombia for the low-rise residential buildings. Rubber and reinforcement materials employed in the manufacturing of the isolator prototypes were obtained locally to minimize the cost of the new devices. Different isolator config- urations, including steel versus nylon/carbon fiber reinforcement (FREI) and bolted versus unbounded con- nections, were investigated to provide technological competitiveness. In the first phase, a high damping rubber was developed and characterized. In the second phase, prototypes of isolators designed for a real building were built and tested using combined compression and shear test. The results highlight an interesting comparison between vertical and horizontal properties of classical SREIs and unbolted FREIs, both satisfying required design values. Specifically, experimental results show that the behavior of the FREIs, in the horizontal direction, is similar to the SREIs, whereas the damping ratio is higher. Satisfactory results were also obtained with nylon reinforcement. Regarding the connection, the unbonded prototypes showed a better behavior respect to classical SREI, achieving higher deformations without failing. Therefore, this type of unbounded FREIs could represent a very promising option with higher potential to be implemented as a low-cost seismic isolation system in re- sidential low-rise buildings of developing countries. 1. Introduction Base isolation is a technique through which the structure is un- coupled from the ground by installing flexible bearings at the founda- tion's level. This reduces the potentially damaging motion that earth- quakes transmit to the structure and decreases the economic and human life losses after the event [1]. The isolation system has been widely implemented in developed countries with more than 12,000 projects [2], and its effectivity has been proved during different seismic events worldwide [3,4]. An important number of developing countries are considered as high seismic activity regions, with the most devas- tating earthquake records in the last decades; however, the isolation system is rarely implemented in their infrastructure. Colombia is a distinct example of this, with seismic events like Tumaco (December 1979, magnitude 7.5), Popayán (march 1983, magnitude 5.5) and Ar- menia (January 1992, magnitude 6.6) earthquakes, which caused more than 2500 human losses, 6000 wounded, 43,000 houses damaged and 50,000 destroyed, in total. However, until 2016, only three buildings were isolated for a special use (education and health). In Colombia, the limited implementation is related to two main aspects. First, the most common type of isolation device is the steel- reinforced multilayer elastomeric isolator (SREI) [5], which is generally large, heavy and expensive due to the highly labor-intensive manu- facturing process [6]. Second, the absence of manufacturing companies in Colombia requires the devices be imported which considerably in- creases the final cost of the isolator. For these reasons, their application https://doi.org/10.1016/j.engstruct.2019.01.037 Received 8 July 2017; Received in revised form 18 September 2018; Accepted 8 January 2019 ⁎ Corresponding author at: Departamento de Ingeniería Civil e Industrial, Pontificia Universidad Javeriana Cali, Calle 18 #118-250, Santiago de Cali, Colombia. E-mail address: ingridm@javerianacali.edu.co (I.E. Madera Sierra). Engineering Structures 183 (2019) 894–906 0141-0296/ © 2019 Elsevier Ltd. All rights reserved. T