{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,21]],"date-time":"2025-11-21T06:10:48Z","timestamp":1763705448599,"version":"build-2065373602"},"reference-count":42,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2018,4,18]],"date-time":"2018-04-18T00:00:00Z","timestamp":1524009600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The in-situ measurement of thermal stress in beams or continuous welded rails may prevent structural anomalies such as buckling. This study proposed a non-contact monitoring\/inspection approach based on the use of a smartphone and a computer vision algorithm to estimate the vibrating characteristics of beams subjected to thermal stress. It is hypothesized that the vibration of a beam can be captured using a smartphone operating at frame rates higher than conventional 30 Hz, and the first few natural frequencies of the beam can be extracted using a computer vision algorithm. In this study, the first mode of vibration was considered and compared to the information obtained with a conventional accelerometer attached to the two structures investigated, namely a thin beam and a thick beam. The results show excellent agreement between the conventional contact method and the non-contact sensing approach proposed here. In the future, these findings may be used to develop a monitoring\/inspection smartphone application to assess the axial stress of slender structures, to predict the neutral temperature of continuous welded rails, or to prevent thermal buckling.<\/jats:p>","DOI":"10.3390\/s18041250","type":"journal-article","created":{"date-parts":[[2018,4,19]],"date-time":"2018-04-19T10:12:01Z","timestamp":1524132721000},"page":"1250","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Non-Contact Smartphone-Based Monitoring of Thermally Stressed Structures"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5783-479X","authenticated-orcid":false,"given":"Mehmet","family":"Sefa Orak","sequence":"first","affiliation":[{"name":"Laboratory for Nondestructive Evaluation and Structural Health Monitoring Studies, Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA"},{"name":"Department of Civil Engineering, Istanbul Technical University (ITU), Maslak, Istanbul 34469, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8826-661X","authenticated-orcid":false,"given":"Amir","family":"Nasrollahi","sequence":"additional","affiliation":[{"name":"Laboratory for Nondestructive Evaluation and Structural Health Monitoring Studies, Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Turgut","family":"Ozturk","sequence":"additional","affiliation":[{"name":"Department of Civil Engineering, Istanbul Technical University (ITU), Maslak, Istanbul 34469, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"David","family":"Mas","sequence":"additional","affiliation":[{"name":"Institute of Physics Applied to the Sciences and Technologies, University of Alicante, Alicante 03690, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8455-5534","authenticated-orcid":false,"given":"Belen","family":"Ferrer","sequence":"additional","affiliation":[{"name":"Department of Civil Engineering, University of Alicante, Alicante 03690, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Piervincenzo","family":"Rizzo","sequence":"additional","affiliation":[{"name":"Laboratory for Nondestructive Evaluation and Structural Health Monitoring Studies, Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2018,4,18]]},"reference":[{"key":"ref_1","unstructured":"(2018, April 17). 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