Early Determination of the Presence of Low Strength Concrete in Reinforced Concrete Beam-Column Joints Using Piezoceramic-Based Transducers

Bolted spherical joints are widely used to form space steel structures. The stiffness and load capacity of the structures are affected by the looseness of bolted spherical joint connections in the structures. The looseness of the connections, which can be caused by fabrication error, low modeling accuracy, and “false twist” in the installation process, may negatively impact the load capacity of the structure and even lead to severe accidents. Furthermore, it is difficult to detect bolted spherical joint connection looseness from the outside since the bolts connect spheres with rods together from the inside. Active sensing methods are proposed in this paper to monitor the tightness status of the bolted spherical connection using piezoceramic transducers. A triangle-on-triangle offset grid composed of bolted spherical joints and steel tube bars was fabricated as the specimen and was used to validate the active sensing methods. Lead Zirconate Titanate (PZT) patches were used as sensors and actuators to monitor the bolted spherical joint tightness status. One PZT patch mounted on the central bolted sphere at the upper chord was used as an actuator to generate a stress wave. Another PZT patch mounted on the bar was used as a sensor to detect the propagated waves through the bolted spherical connection. The looseness of the connection can impact the energy of the stress wave propagated through the connection. The wavelet packet analysis and time reversal (TR) method were used to quantify the energy of the transmitted signal between the PZT patches by which the tightness status of the connection can be detected. In order to verify the effectiveness, repeatability, and consistency of the proposed methods, the experiments were repeated six times in different bolted spherical connection positions. The experimental results showed that the wavelet packet analysis and TR method are effective in detecting the tightness status of the connections. The proposed active monitoring method using PZT transducers can monitor the tightness levels of bolted spherical joint connections efficiently and shows its potential to guarantee the safety of space steel structures in construction and service.

Section: Introductionmentioning

confidence: 99%

Health Monitoring of Bolted Spherical Joint Connection Based on Active Sensing Technique Using Piezoceramic Transducers

Wang

et al. 2018

“…The principle of this approach is to measure the propagating wave property changes due to the structural damage by using a pair of PZT transducers or a deployed sensor network. An increasing amount of research on structural health monitoring using the active sensing approach has been conducted and reported, including crack and corrosion detection of a metal pipeline system [ 47 , 48 ], monitoring of bolt and rock bolt looseness [ 49 , 50 , 51 , 52 ], damage identification in space structures [ 53 ], crack and leakage detection of concrete structures [ 54 , 55 ], bond slip detection of composite concrete structures [ 56 , 57 , 58 , 59 ], early-age cement hydration monitoring [ 60 , 61 , 62 ], nondestructive concrete strength evaluation [ 63 ], and disbond detection in adhesively bonded structures [ 64 , 65 ]. Moreover, Park et al [ 66 ] proposed a self-powered flexible piezoelectric pulse sensor based on a PZT thin film for a real-time health care monitoring system.…”

Section: Introductionmentioning

confidence: 99%

A Feasibility Study on Timber Damage Detection Using Piezoceramic-Transducer-Enabled Active Sensing

Zhang

Huang

Zheng

2018

In recent years, piezoelectric-based transducers and technologies have made significant progress towards structural health monitoring and damage evaluation for various metal and concrete structures. Timber is still commonly used as a construction material in practical engineering; however, there is a lack of research on the health monitoring of timber-based structures using piezoelectric-based transducers and methods. This paper conducts a feasibility study on timber damage detection using surface-mounted piezoelectric patches, which enable the stress-wave-based active sensing approach. Typical damage modes in timber frame structures, such as surface cracks and holes, were investigated in this study. In the active sensing approach, one piezoceramic transducer is used as an actuator to generate stress waves, which propagate along the surface of the timber structure, and other piezoceramic transducers function as sensors to detect the propagating stress waves. Defects, such as a crack or a hole, induce additional attenuation to the propagating stress wave. Based on this attenuation, the proposed method can detect the defects using the wavelet-packet-based damage index, demonstrating its implementation potential for real-time timber damage detection.

“…The field of ultrasonic guided waves has created much interest in the past decades. The number of publications, research works, activities, and actual applications has increased significantly [ 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. The propagation characteristics of the guided waves are often closely related to the structure, the defect type, and the mechanical properties of the material [ 5 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

Development of a Novel Guided Wave Generation System Using a Giant Magnetostrictive Actuator for Nondestructive Evaluation

Luo

Wang

et al. 2018

Self Cite

As a common approach to nondestructive testing and evaluation, guided wave-based methods have attracted much attention because of their wide detection range and high detection efficiency. It is highly desirable to develop a portable guided wave testing system with high actuating energy and variable frequency. In this paper, a novel giant magnetostrictive actuator with high actuation power is designed and implemented, based on the giant magnetostrictive (GMS) effect. The novel GMS actuator design involves a conical energy-focusing head that can focus the amplified mechanical energy generated by the GMS actuator. This design enables the generation of stress waves with high energy, and the focusing of the generated stress waves on the test object. The guided wave generation system enables two kinds of output modes: the coded pulse signal and the sweep signal. The functionality and the advantages of the developed system are validated through laboratory testing in the quality assessment of rock bolt-reinforced structures. In addition, the developed GMS actuator and the supporting system are successfully implemented and applied in field tests. The device can also be used in other nondestructive testing and evaluation applications that require high-power stress wave generation.