Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct Analysis of the long and short-term effects of temperature and humidity on the structural properties of adobe buildings using continuous monitoring Giacomo Zonno a , Rafael Aguilar a, ⁎ , Rubén Boroschek b , Paulo B. Lourenço c a Pontificia Universidad Católica del Perú – PUCP, Department of Engineering, Av. Universitaria 1801, San Miguel, Lima 32, Peru b University of Chile, Department of Civil Engineering, Av. Blanco Encalada 2002, Santiago, Región Metropolitana, Chile c University of Minho, ISISE, Department of Civil Engineering, Campus de Azurém, 4800 - 058 Guimarães, Portugal ARTICLE INFO Keywords: Ambient vibration monitoring Environmental monitoring Adobe buildings Historical churches Structural and environmental correlations ABSTRACT The analysis of the evolution of modal properties and its relationship with changes in environmental properties (i.e. ambient temperature and relative humidity) is of high importance since their effects along time can mask the influence of structural damage. While structural monitoring studies to assess the relationship between modal parameters and environmental conditions are abundantly available for modern materials constructions (i.e. concrete or steel), very few studies are reported for adobe buildings. The present paper focuses on the study of the short and long-term structural behavior of existing adobe buildings through the long-term monitoring of ambient vibration and environmental conditions. With this purpose, the paper describes in detail the case study of the San Pedro Apostol Church of Andahuaylillas located in Cusco, inside the Andean region of Peru, a 16th- century church considered as a masterpiece of South American baroque architecture. The paper starts with a historical, architectural, and structural description of the case study. Then, it describes the implementation of a long-term monitoring system of ambient vibration and environmental variables, as well as the results of almost one year of continuous monitoring process. Finally, the obtained results of natural frequencies are correlated with ambient parameters, demonstrating different timescale influences in the modal properties due to daily and seasonal variations of the environmental conditions. 1. Introduction Conservation and promotion of the architectural heritage and ar- chaeological sites is a crucial issue to preserve the intellectual richness and cultural diversity of a modern society. This task is complex due to the high vulnerability of the culture heritage buildings affected by aging of the materials, lack of maintenance, inappropriate use, and effects of natural risks (i.e. environmental conditions, seismic hazard, etc.). In particular, earthen historical constructions have a higher vul- nerability due to the addition of issues in the material itself such as its low tensile strength and brittle behavior [1]. Earthen constructions have a significant presence in different regions of Latin America and, in particular in Peru, where most of the national historical monuments are made of adobe [2]. Remarkable examples of these Peruvian earthen monuments include the magnificent structures of Caral (2000 BCE), the complexes of “Huaca del Sol” and “Huaca de la Luna” (100–800 CE), the pre-Columbian city of Chan-Chan (850–1476 CE), among others [3]. Nowadays, these invaluable constructions are exposed to an un- acceptable high risk that endangers their conservation over time due to the high seismic hazard of the Latin American region. A better under- standing of the structural behavior of these buildings is a crucial step to prevent social, cultural, and economic losses [4]. Vibration-based Structural Health Monitoring (vSHM) is being in- creasingly used for the structural evaluation of historical buildings, such as bell towers [5–9], and stone masonry churches [10–13], be- cause it allows to collect automatic real-time data which provide in- sights regarding structural vulnerability [14], strengthening needs [15] or the occurrence of damage [16]. The most common developed pro- cedures to obtain automatic and accurate estimations of the modal parameters from dynamic data are based on Data-driven or Covariance- driven Stochastic Subspace Identification methods (SSI-Data o SSI-Cov) [17,18], because these methods are able to identify closely spaced modes [19]. Unfortunately, the real-time damage detection through structural monitoring of existing buildings is a challenging task because environmental changes can provoke variations in the boundary condi- tions [20,21], in the system stiffness [22], and in other structural parameters, complicating the accurate identification of structural anomalies [23–26]. Extensive research has been conducted to https://doi.org/10.1016/j.engstruct.2019.109299 Received 5 December 2018; Received in revised form 17 April 2019; Accepted 11 June 2019 ⁎ Corresponding author. E-mail address: raguilar@pucp.pe (R. Aguilar). Engineering Structures 196 (2019) 109299 0141-0296/ © 2019 Elsevier Ltd. 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