Issue 51

K. Li et alii, Frattura ed Integrità Strutturale, 51 (2020) 386-397; DOI: 10.3221/IGF-ESIS.51.28 387 between the structure and the resistance is analyzed. It is used to promote the comprehensive judgment and evaluation of the safety and reliability of the structure. [2]. However, the detection process is limited by the complex constraints of the engineering site. The traditional structure detection technology cannot fully meet the requirements of modern building structure detection in terms of measuring dimensions, range and frequency [3]. For example, the Progressive Collapse study, which has received extensive attention from the international civil engineering community. The dynamic response of the structure is triggered by the initial initialization of the test component's own components, resulting in high frequency vibration and large deformation. The dynamic strain and the displacement are required to be measured, which exceed the application range of traditional measurement technology [4]. Therefore, it is very necessary to develop precision detection devices and related measurement technologies in combination with various emerging fields. Thereby, the non-destructive detection and reliability identification of modern building structures can be realized efficiently [5]. As one of the latest advances in the field of structural measurement, non-contact measurement technology has the advantages of undamaged, accuracy and objectivity [6]. Among them, Digital Image Correlation (DIC) has been widely used in structural detection experiments [7]. However, DIC technology requires higher illumination conditions for the detection environment. It generally requires multiple devices to work together to obtain spatial deformation information [8]. And the 3D laser scanning measuring device has the following advantages: 1) non-destructive: getting rid of installing the sensor on the object to be detected; 2) strong environmental adaptability: the laser itself can be used as a light source to resist interference; 3) efficient detection: can achieve 3D information acquisition of a single device [9-12]. Therefore, the 3D laser scanning technology have lately received great attention in the field of building structure inspection [13, 14]. Park [15] applied 3D laser scanning technology to structural health monitoring, and verified the effectiveness of the method based on the static loading test of simply supported steel beams. Olsen [16] used 3D laser scanning technology to quantitatively describe the structural damage based on the reinforced concrete frame joint test. Dai [17] obtained the 3D laser scanning data of the steel beam structure and extracted the deformation field information of the structure. The widespread application of commercial, integrated 3D laser scanners to structural testing are facing numerous challenges: 1) Scanners are usually expensive, bulky, and complex; 2) The detection environment is limited, and it is difficult for the inspectors to operate flexibly; 3 ） Usually, the scanner scans large structures, and it is difficult to accurately construct a three-dimensional model of the structural test object. Therefore, it is worthwhile devoting much effort to develop a 3D laser scanning device that is miniaturized, lightweight, high precision and low-cost, thereby achieving accurate modeling of modern structural tests [18]. The laser ranging sensor is characterized by accuracy and efficiency. Therefore, it plays an important role in measurement, navigation and security [19]. Among them, the 2D laser ranging sensor can form a single complete scanning plane by single line scanning. We can independently design a 3D scanning device that drives the 2D laser sensor to move up and down according to the needs of the detection object and the environment.20]. The designed scanning device is more adaptable and flexible, can accurately construct a 3D model based on lower cost. The 3D scanning device integrated by 2D laser sensor has been widely used in environmental modeling, mechanical automation and other fields. For example, the Fraunhofer Institute for Autonomous Intelligent Systems in Germany developed an autonomous mobile robot with a 2D laser range finder and successfully applied it to 3D exploration and digital simulation for indoor environments [21]. Chou [22], etc., installed a 2D laser sensor on a rotating four-bar linkage to create an indoor 3D mapping automatic scanning robot. Cai Jun [23] developed a 3D laser scanning system consisting of a high-precision rotating head and a small 2D laser ranging sensor to achieve high-precision automation environment modeling. The detection technology of 3D laser scanning by adding 2D laser sensor to the 1D transmission actuator has achieved good research results [24-25]. However, despite these considerable advantages, this technology has not been widely promoted in structural testing studies. In summary, it is essential to independently develop a 3D laser scanning system for modern structural inspection. The stepper motor drives the fine movement of the sliding group to realize the lifting and scanning of the two-dimensional laser ranging sensor. This system is portable, more accurate, more adaptable and less costly. It realizes non-destructive, efficient and accurate detection of structural damage 3D information. Based on the RPC bending fatigue test, the reliability of the 3D modeling and structural damage information measurement data of the device was verified. 3D LASER SCANNING SYSTEM DESIGN Principles of System Design he 3D laser scanning system designed in this paper is mainly composed of a 2D laser ranging sensor, a sliding mold combination, a bracket, a control box and a computer, as shown in Figure 1. The scanning system is divided into four parts: a transmission actuator, a transmission control device, a laser ranging sensor, and a sensor control T