Abstract

In this study, a regional convolutional neural network (RCNN)-based deep learning and Hough line transform (HLT) algorithm are applied to monitor corroded and loosened bolts in steel structures. The monitoring goals are to detect rusted bolts distinguished from non-corroded ones and also to estimate bolt-loosening angles of the identified bolts. The following approaches are performed to achieve the goals. Firstly, a RCNN-based autonomous bolt detection scheme is designed to identify corroded and clean bolts in a captured image. Secondly, a HLT-based image processing algorithm is designed to estimate rotational angles (i.e., bolt-loosening) of cropped bolts. Finally, the accuracy of the proposed framework is experimentally evaluated under various capture distances, perspective distortions, and light intensities. The lab-scale monitoring results indicate that the suggested method accurately acquires rusted bolts for images captured under perspective distortion angles less than 15° and light intensities larger than 63 lux.

Highlights

  • Bolts serve to connect structural components and to maintain the load-bearing performance of a steel structure

  • This paper presents a regional convolutional neural network (RCNN)-based deep learning and Hough line transform (HLT) algorithm to autonomously monitor bolt corrosion and loosening in steel structures

  • Lab-scale experiments were performed under three uncertain conditions to evaluate the feasibility of the RCNN-based bolt detector and HLT-based bolt angle estimation

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Summary

Introduction

Bolts serve to connect structural components and to maintain the load-bearing performance of a steel structure. Despite the above research efforts, there exists a need to improve vision-based methods for accurate detection of complex damage types such as corrosion and bolt-loosening in bolted connections. To this end, this paper presents a regional convolutional neural network (RCNN)-based deep learning and Hough line transform (HLT) algorithm to autonomously monitor bolt corrosion and loosening in steel structures. The accuracy of the proposed framework is experimentally evaluated under various capturing distances, perspective distortions, and light intensities

Workflow of Bolt Detection and Bolt Angle Estimation
RCNN-based Classification of Clean and Corroded Bolts
Training of an RCNN-Based Bolt Detector
Image Correction of Perspective Distortion
HLT-Based Bolt-Loosening Estimation
Lab-Scale Experimental Setup
Bolt Identification under Various Perspective Distortions
Bolt Identification under Various Capture Distances
Bolt Identification under Various Light Intensities
Bolt-Loosening Estimation under Various Perspective Distortion
Bolt-Loosening Estimation under Various Image Capture Distances
Bolt-loosening Estimation under Various Light Intensities
Findings
Conclusions

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