Tri-Camera High-Speed Videogrammetry for Three-Dimensional Measurement of Laminated Rubber Bearings Based on the Large-Scale Shaking Table

Xiaohua Tong,Xianglei Liu,Yanmin Jin,Shijie Liu,Peng Chen,Baofeng Huang,Kuifeng Luan,Wensheng Lu

doi:10.3390/rs10121902

Abstract

Laminated rubber bearings are widely used for the mitigation of seismic damage of large-scale structures and equipment. However, owing to the flexibility in horizontal direction, the traditional contacted transducer is difficult to acquire the displacement data accurately in the three directions, respectively. In this paper, three-dimensional displacement measurement of laminated rubber bearing based on the large-scale shaking table is achieved by the use of a tri-camera high-speed videogrammetric system consisting of three complementary-metal-oxide-semiconductor (CMOS) cameras, one synchronous controller, and one pair of 1000 watt light sources, which are used to simultaneously acquire the tri-camera image sequences of laminated rubber bearing at a speed of 300 frames per second (fps). Firstly, this paper proposes a fast image block technique for detecting and tracking targets in tri-camera image sequences by integration of techniques morphological edge detection, attribute based ellipse extraction and least-squares-based fitting adjustment. Secondly, this paper presents an integrated bundle adjustment approach, which brings continuous tracking points into one collinearity condition equation, to reconstruct the three dimensional coordinates of continuous tracking points, for the purpose of improving the accuracy of three-dimensional coordinates of tracking points based on tri-camera image sequences. At last, an empirical experiment was conducted to measure the three-dimensional displacement of laminated rubber bearings on the shaking table by the use of the proposed method. The experimental results showed that the proposed method could obtain three-dimensional displacement of laminated rubber bearings with an accuracy of more than 0.5 mm.

Highlights

Aiming to effective reduce the seismic response of the structures/equipment, rubber bearing and friction-based bearing are two important isolation bearings with application to seismic isolation of the structures/equipment [1,2]
Laminated rubber bearings are constructed from alternating layers of rubber vulcanized to reinforce steel shims, they can be treated as periodic structures, which can provide later flexibility when the isolator is subject to horizontal loads, of which seismic performance can directly affect the stability of structures/equipment [1,4]
Before laminated rubber bearings are used in practical applications, their seismic performance needs to be verified based on the shaking table, which is a specific device for shaking structural models or building components with a simulated seismic wave [5,6]

Summary

Introduction

Aiming to effective reduce the seismic response of the structures/equipment, rubber bearing and friction-based bearing are two important isolation bearings with application to seismic isolation of the structures/equipment [1,2]. The objective of detecting and tracking targets is to determine the positions of targets in tri-camera image sequences aiming at understanding the motion mechanism of the shaking table structure. This paper proposes to build a tri-camera high-speed videogrammetric system to make three-dimensional reconstruction of the continuous tracking points accurately, which is not widely used in the field of civil engineering.

Experimental Site and Structure Model

Approaches

Experimental Results and Discussions

Results of Detecting and Tracking the Ellipical Targets

Result of Accuracy Assessment of the Tri-Camera Videogrammetry