 Advances in Technology Innovation , vol. 2, no. 2, 2017, pp. 56 - 60 56 The Research of Infrared Thermal Image Diagnostic Model for Building External Wall Tiles Li-Wei Chiang * , Sy-Jye Guo Department of Civil Engineering, National Taiwan University, Taipei 106, Taiwan, ROC. Received 22 February 2016; received in revised form 29 April 2016; accept ed 04 May 2016 Abstract This study focuses on a deterioration diag- nostic standard and inspection time for e xterna l wall t iles. The study was carried out using a tap tone test, followed by fast Fourier transform and pattern recognition to analyse the tapping results. Based on the test results, the study recommends that for frequencies between 200 and 800 Hz on the spectrogram, it can be deduced that a cavity is present in the tiles. The study was carried out using infrared thermal imag ing record to det e- riorat ion and norma l t ile position. This study observed temperature changes per hour, it is obvious temperature diffe rence with deteriora - tion tiles and norma l tiles between 09: 00-11: 00 (East), 10:00-14:00 (West), 10:00-12:00 (South) and 11:00-13:00 (North), the study was calcu- lated that the average temperature difference of 1.0 degrees. This study suggests that the best e xperimental inspection time is 09: 00-14:00. Exclude the impact of e xte rnal factors, if the temperature d ifference more than 1.0 degrees, it can be deduced that a cavity is present in th e t iles, and this can be used as basis for determining tile deterioration. Keywor ds : external wall tiles, infrared thermal image inspection, tap tone inspec- tion, temperature difference, in- spection period 1. Introduction In Taiwan, there has experienced frequent safety incidents involving the e xternal wa lls of buildings recent years. The most common inci- dents include falling tiles, falling advertising signage and falling e xposed pipelines, all seriously impacting the surrounding environment and public safety. On March 14, 2015, a tile falling inc ident in Taipei City, Taiwan, resulted in a fatality. According to the Taipei City Go v- ernment Statistics, there were 1188 buildings listed for control as important cases with spall- ing wa ll tiles. The govern ment of Kaohsiung City, Taiwan investigated the 6492 apart ment buildings with six or more floors in the city. There we re 859 buildings with t iles spalling. Kaohsiung City government listed 367 buildings as important cases for control. According to research data (Chang, 2008), construction in Taiwan peaked in the years 1981 and 1994. According to this research, Taiwanese buildings e xperience significant deteriorat ion after 30 years. Safety check require ments for Taiwanese buildings should thus peak in 2011 and 2024. Integrating news relating to fatalities in tile-fa lling incidents in Taiwan, this research sees an immed iate need for a co mp lete diagno s- tic mechanism and preventive method for the further occurrences of such public safety inci- dents. To effectively drive external wall replacement safety checks and studies on evaluation systems, the industry requires relevant emp irica l results and evaluation criteria. Th is study aims to e m- ploy data collection and e mp irical research to provide a basis of reference and an evaluation method for use in external wall tile diagnosis. 2. Method 2.1. Tap Tone Method This study used s ounding diagnosis to com- ple ment the visual diagnosis method. The tap tone diagnostic method is the most convenient, economical and wide ly used evaluation method for inspecting surface defects. Tile inspection is norma lly co mbined with other inspection meth- ods (such as the visual inspection method) as a basis for inspection of the condition of wall tile deterioration. * Corresponding aut hor, Email: d9952 1007@ntu.edu.tw Advances in Technology Innovation , vol. 2, no. 2, 2017, pp. 56 - 60 57 Copyright © TAETI The theory behind the tap tone diagnostic method is associated with determinations made through sound frequency. Besides pitch, sound also has intensity and tone. Genera lly speaking, pitch, intensity (loudness) and timbre are the three main ele ments of sound. The pitch of a sound is determined by its frequency of vibra- tion. A higher frequency of vibration indicates a higher pitch, and a lo wer frequency of vibration indicates a lower p itch. The intensity of sound is determined by the vibration magnitude (amp li- tude) of the sound wave. Higher a mp litudes equate to more powerful sound waves, and thus louder sounds. Observing the diffe rent sounds generated from tapping on norma l and dete rio- rated tiles with a tap tone diagnosis stick, this study uses a Fast Fourier Transform to determine a spectrogram. Frequency (Hz, x-coordinate) and amplitude (V, y-coordinate) a re used to form the basis for determin ing the degree of tile deterio- ration. Spectrogra ms fro m the tap tone diagnosis are shown in Fig. 3 and Fig. 4. The spectro- gram's peak and trough for norma l tiles show stable frequency (Fig. 1), while deteriorated tiles show apparent instability (Fig. 2). Fig. 1 Transformed spectrum for a tap tone diagnosis on normal tile Fig. 2 Transformed spectrum for a tap tone diagnosis on deteriorated tiles Fig. 3 Test procedure 2.2. Infrared Thermal Image Method This study uses the infrared therma l imaging to detect building e xternal wall tiles. Infrared therma l imaging method is use natural sunlight, which a llo ws the building wa ll tile te mperature changes . In general, if there is no concrete pos i- tion defect (bulging phenomenon), infrared therma l imaging d isplays a consistent surface color. Since the defective portion and the norma l portion of different therma l conductivity, this study used infrared therma l imaging device to measure ments the temperature diffe rence to determine peeling. Selected object Confirm the external wall tiles surface moist condition Tap Tone diagnosis and consistent strength Tap Tone record results Marking on the external wall, to records the deterioration and normal tiles Adjust the machine parameters - Temperatures Every 30 minutes, record the normal and deterioration position of the Infrared thermal imaging photos FLIR Tools Soft to analysis tile temperature Advances in Technology Innovation , vol. 2, no. 2, 2017, pp. 56 - 60 58 Copyright © TAETI In this study, every 30 minutes to record the e xternal wall t iles temperature of the building, fro m 09:00 to 17:00, then through the analysis of temperature-t ime curve to discuss the best measure ment time. When detecting the position of internal de fects, the temperature deterioration of the position will be higher than other norma l area in the day heating period (08:00-11:00), on the contrary, when the cooling time in the day (16:00-19:00), the degradation position will lower te mperature than the norma l position. And then, this study used tap tone diagnostic method to confirm the deterioration of the range. 3. Results and Discussion 3.1. Tap Tone Diagnosis Results The study carried out tap tone diagnosis on 2 buildings . There are 63 a reas of deterioration out of 126 tap tone diagnostic tests. The study deems the first peak of the spectrogram as noise, the beginning of the second wave as the start point of deteriorat ion sound, and its end point as the end point of the deterioration sound. The spec- trogram is then segmented by lattice points. Further statistical analysis of the 126 deterio- rated areas shows that the average start point of deteriorated tiles is 239Hz, while that for the end point is 761Hz. The deterioration e xtent is in- dicated by the shaded portion. The study suggests that upon tap tone diag- nosis, if the Fast Fourier Transform graph shows a frequency fro m 200 to 800 Hz, it can be spec- ulated that there is a cavity in the tiles. If tap tone diagnosis is required, it is suggested to tap at least 5 spots on the facade to increase overall detection accuracy. The study tentatively rec- ommends that if the tile deterioration ratio e x- ceeds 50%, immediate overall facade renovation of the building should be carried out. If the tile deterioration ratio is less than 50%, then safety measures to prevent surrounding objects from falling should be immediately imposed. This study investigated 2 building cases in the National Taiwan Un iversity. This study used lattice segmentation method for analyzing 126 tiles deterioration image spectrums. It is found that the deterioration of the tiles starts at fre - quency average about 240Hz and ends at about 760Hz. Deterio ration hatched range shown in table 1 and table 2. Table 1 Case A of tap tone diagnosis results Case A Table 2 Case B of tap tone diagnosis results Case B Advances in Technology Innovation , vol. 2, no. 2, 2017, pp. 56 - 60 59 Copyright © TAETI The study conso lid ates resu lts an d rec- ommendations of visual inspection and taps tone diagnosis, and proposes a diagnostic criteria and standard operating procedures for e xternal wa ll tile deterioration diagnosis of Taiwan buildings. 3.2. Infrared Thermal Image Diagnosis Results Fig. 4 Case A external wa ll tiles infra red images (SP1: deterioration, SP2: normal) According to statistics , the study found that the east tiles ma ximu m te mperature is 2.0 de- grees, occurred at 9: 00-10: 00. The west tiles ma ximu m te mperature is 1.3 degrees, occurred at 12: 00-13: 00. The south tiles ma ximu m temperature is 1.3 degrees also, occurs at 11: 00-12: 00. The north tiles ma ximu m te mperature is 1.2 degrees, occurred at 12: 00-13: 00. In this study, the statistics of the external wall te mper- ature, an average temperature d iffe rence of 1 degree results. This study suggests that the threshold can be used as observation Fig. 5 Case A temperature difference of east external wall tiles Fig. 6 Case A te mperature diffe rence of west external wall tiles Fig. 7 Case A temperature diffe rence of south external wall tiles Fig. 8 Case A temperature difference of north external wall tiles This study analyzed the average of daily tem- perature difference, the temperature difference if more than one degree, and in the best time of ob- servation of this study suggests, it can be specu- lated that there is deterioration of tile production. Aggregated data are shown in Table 3. Table 3 The investigation time and threshold of external wall tiles East West Sout h Nort h Maximum t em- perat ure differ- ence 2.0 1.3 1.3 1.2 Average t emper- at ure difference 1 0.9 1.1 0.9 Recommendation inspect ion t ime 09-11 12-14 10-12 11-13 Advances in Technology Innovation , vol. 2, no. 2, 2017, pp. 56 - 60 60 Copyright © TAETI 4. Conclusions Since the construction boom in the 1970s in Taiwan, many build ing e xterna l wa ll have su f- fered natural deterioration, and many inc idents of e xterna l wall tiles falling have occurred, with some even resulting in fatalities. As the nu mber of such cases has increased, a comp lete e xterna l wall tile d iagnostic system is required. This study proposes public safety visual diagnostic models for e xternal wa ll tiles of build ings, in- cluding Tap Tone and Infrared The rma l Image diagnostic concepts, diagnostic method and diagnostic evaluation reference datum. It a lso offers a Infrared Thermal Images method for e xternal wa ll tiles, as we ll as suggesting the adoption of tap tone diagnosis on tiles that p o- tentially have significant impact on public safety. It also verifies the developed evaluation model, and proposes countermeasures and recommenda- tions for deterioration conditions. Based on the test results, the study reco m- mends that for frequencies between 200 and 800 Hz on the spectrogram, it can be deduced that a cavity is present in the tiles, and this can be used as basis for determining tile deterioration. The study was carried out using infrared therma l imaging record to deteriorat ion and norma l t ile position. Th is study observed tem- perature changes per 30 mins, it is obvious temperature d iffe rence with deteriorat ion tiles and norma l tiles between 09: 00 -11: 00 (East), 10:00-14:00 (West), 10:00-12:00 (South) and 11:00-13:00 (North), the study was calculated that the average temperature d ifference of 1.0 degrees. This study suggests that the best ex- perimental inspection time is 09: 00 -14:00. Exclude the impact of e xte rnal factors, if the temperature d ifference more than 1.0 degrees, it can be deduced that a cavity is present in the t iles, and this can be used as basis for determining tile deterioration. Acknowledgement This research was supported by the Ministry of Science and Technology (MOST 103-2221-E -002-171), and Sinotech Foundation for Research and Development of Engineering Sciences and Technologies. References [1] L. W. Chiang, S. J. Guo, C. Y. Chang, and T. P. Lo, “The develop ment of a diagnostic model for the deterioration of exte rnal wa ll tiles of aged buildings in Taiwan,” Journal of Asian Architecture and Bu ild ing Eng i- neering, vol. 15, no.1, pp. 111-118, January 2016. [2] L. W. Chiang, S. J. Guo, and C. Y. Chang, “The model of visual inspection for building external wall deterioration tiles,” Journal of Architecture, vol. 87, pp. 49-66, 2014. (In Chinese) [3] E. D. Km, “Service life prediction for buildings exposed to severe weather,” Journal of Asian Architecture and Building Engineering, vol. 10, no.1, pp. 211-215, 2011. [4] F. Tong, S. K. Tso, and X. M. Xua, “Tile-wall bonding integrity inspection based on time-domain features of impact acoustics,” Journal of Sensors and Actuators A 132, pp. 557-566, 2006. [5] U. Taketo, K. Kato, and S. Hirono, Non-destructive of the concrete structure, Tokyo: Morikita publishing Co., Ltd, 2000.