PSI - Issue 11

J.H.A. Rocha et al. / Procedia Structural Integrity 11 (2018) 99–106 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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1. Introduction

At present, there is a search for non-destructive tests that might be applied in the inspection and evaluation of different structures (Runkiewicz 2009), mainly looking for the advantages they present such as the lack of direct contact with the object studied, thus avoiding partial destruction and waste generation. Among many non-destructive tests available in the market, infrared thermography arises for including a basic principle that states every object emits radiation in the infrared band of electromagnetic spectrum, which is related to its temperature. Radiation is captured by a thermographic camera and transformed into electrical signals to be then processed and presented as thermograms or thermal images, where each temperature is represented by a color (Silva 2012). Despite being a consolidated technique in different areas such as medicine, military tactics, mechanics and electricity (Bagavathiappan et al. 2013), its application in civil construction is still under development. There are many investigations in the area such as detection of anomalies in waterproofing (Melrinho et al. 2015), ceramics delamination (Bauer et al. 2016), bridge inspection (Rocha and Póvoas 2017, Rehman et al. 2016) and identification of thermal bridges (Asdrubali et al. 2018), among others (Bagavathiappan et al. 2013). Regarding building activities, pathologies involving moisture are the most common, mainly those from precipitation (Melrinho et al. 2015), and in many cases their detection is complicated because they are invisible at initial stage. In this context, infrared thermography may become an important tool to detect these problems due to its non-destructive and contactless features, as well as fast results obtained, which may be analyzed both in qualitatively or quantitatively manner. In the first case, by visualizing different colors or surface temperature heterogeneity of a subject studied; and in the second case, providing exact values of temperature and its evolution according to heating sources over time. Temperature needs a correct definition of measurement parameters and a more detailed analysis (Oliveira 2013). In addition to mentioned benefits, this technique also has advantages related to disorders that should have minimal impact to users (Barreira and Freitas 2007, Bernardo 2012). However, applying infrared thermography is possible only if there are differences in temperature between an object surface and the environment that might generate thermal gradients (Barreira 2004, Tarpani et al. 2009, Amarante et al. 2016). In recent years, many investigations with infrared thermography were developed to study problems arising from humidity (Barreira et al. 2016, Oliveira 2013). However, there are still some uncertainties regarding test implementation and data analysis. In this sense, this work is also intended to verify applicability of this technique on humidity detection from pluvial precipitation, specifically. 2. Methodology Methodology for this work was carried out through a case study involving a building that showed signs of infiltration and stains caused by rainfall. The building is located on Nossa Senhora da Conceição Street, Aguazinha, Olinda, Pernambuco in Brazil (Fig. 1a). The subject of this study is a wall on the balcony. Its facade is oriented southeast, therefore the period of greatest solar ray incidence is during morning (Fig. 1b).

Fig. 1. Location for (a) study building and (b) subject wall. Source: Google Earth (2017).