{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,24]],"date-time":"2026-01-24T04:19:01Z","timestamp":1769228341661,"version":"3.49.0"},"reference-count":34,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2021,9,16]],"date-time":"2021-09-16T00:00:00Z","timestamp":1631750400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012226","name":"Fundamental Research Funds for the Central Universities","doi-asserted-by":"publisher","award":["2020CDJQY-A067"],"award-info":[{"award-number":["2020CDJQY-A067"]}],"id":[{"id":"10.13039\/501100012226","id-type":"DOI","asserted-by":"publisher"}]},{"name":"National Key Research and Development Project","award":["2019YFD1101005"],"award-info":[{"award-number":["2019YFD1101005"]}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["51608074"],"award-info":[{"award-number":["51608074"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>Many structures in civil engineering are symmetrical. Crack detection is a critical task in the monitoring and inspection of civil engineering structures. This study implements a lightweight neural network based on the YOLOv4 algorithm to detect concrete surface cracks. In the extraction of backbone and the design of neck and head, the symmetry concept is adopted. The model modules are improved to reduce the depth and complexity of the overall network structure. Meanwhile, the separable convolution is used to realize spatial convolution, and the SPP and PANet modules are improved to reduce the model parameters. The convolutional layer and batch normalization layer are merged to improve the model inference speed. In addition, using the focal loss function for reference, the loss function of object detection network is improved to balance the proportion of the cracks and the background samples. To comprehensively evaluate the performance of the improved method, 10,000 images (256 \u00d7 256 pixels in size) of cracks on concrete surfaces are collected to build the database. The improved YOLOv4 model achieves an mAP of 94.09% with 8.04 M and 0.64 GMacs. The results show that the improved model is satisfactory in mAP, and the model size and calculation amount are greatly reduced. This performs better in terms of real-time detection on concrete surface cracks.<\/jats:p>","DOI":"10.3390\/sym13091716","type":"journal-article","created":{"date-parts":[[2021,9,22]],"date-time":"2021-09-22T03:47:35Z","timestamp":1632282455000},"page":"1716","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":29,"title":["A Real-Time Detection Method for Concrete Surface Cracks Based on Improved YOLOv4"],"prefix":"10.3390","volume":"13","author":[{"given":"Gang","family":"Yao","sequence":"first","affiliation":[{"name":"School of Civil Engineering, Chongqing University, Chongqing 400044, China"},{"name":"Key Laboratory of New Technology for Construction of Cities in Mountain Area, Ministry of Education, Chongqing 400044, China"}]},{"given":"Yujia","family":"Sun","sequence":"additional","affiliation":[{"name":"School of Civil Engineering, Chongqing University, Chongqing 400044, China"},{"name":"Key Laboratory of New Technology for Construction of Cities in Mountain Area, Ministry of Education, Chongqing 400044, China"}]},{"given":"Mingpu","family":"Wong","sequence":"additional","affiliation":[{"name":"School of Civil Engineering, Chongqing University, Chongqing 400044, China"},{"name":"Key Laboratory of New Technology for Construction of Cities in Mountain Area, Ministry of Education, Chongqing 400044, China"}]},{"given":"Xiaoning","family":"Lv","sequence":"additional","affiliation":[{"name":"Science & Technology on Integrated Information System Laboratory, Institute of Software Chinese Academy of Sciences, Beijing 100190, China"}]}],"member":"1968","published-online":{"date-parts":[[2021,9,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"9628","DOI":"10.3390\/s111009628","article-title":"Adaptive road crack detection system by pavement classification","volume":"11","author":"Gavilan","year":"2011","journal-title":"Sensors"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1016\/j.conbuildmat.2016.11.032","article-title":"Algorithm for automatic detection and analysis of cracks in timber beams from LiDAR data","volume":"130","author":"Cabaleiro","year":"2017","journal-title":"Constr. 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