Structural health monitoring (SHM) systems can improve the safety and reliability of structures, reduce maintenance costs, and extend service life. Research on concrete SHMs using piezoelectric-based smart aggregates have reached great achievements. However, the newly developed techniques have not been widely applied in practical engineering, largely due to the wiring problems associated with large-scale structural health monitoring. The cumbersome wiring requires much material and labor work, and more importantly, the associated maintenance work is also very heavy. Targeting a practical large scale concrete crack detection (CCD) application, a smart aggregates-based wireless sensor network system is proposed for the CCD application. The developed CCD system uses Zigbee 802.15.4 protocols, and is able to perform dynamic stress monitoring, structural impact capturing, and internal crack detection. The system has been experimentally validated, and the experimental results demonstrated the effectiveness of the proposed system. This work provides important support for practical CCD applications using wireless smart aggregates.

Structural health monitoring (SHM) can enhance the functionality of structures, improve its safety and reliability, reduce maintenance costs, and increase the service life. A new kind of SHM technology based on piezoelectric ceramic transducers is an effective way to realize the prospective functions. However, many of piezoelectric ceramic SHM systems, which are complicated, weighty, and having much equipment, are mainly used for laboratory researches. In order to meet the needs of engineering applications, a portable piezoelectric concrete SHM system which uses the virtual instrument technology is proposed and produced in this paper. The developed system which is based on piezoelectric transducers can be realized to monitor online vibration accelerations, dynamic stresses, concrete cracks, and so forth. The function of this integrated system has been effectively proved in test and in an engineering application. The experimental and applied results show that the system is reliable, of high degree of automation, and portable. The work provides important technical support for improvement of structure design and monitoring of structural health status.

This paper aims to set up a finite element model using piezoelectric elements to realize pipeline structure damage identification analysis. Ultrasonic guided wave propagation characteristics and damage identification of pipeline structures are analyzed by the ABAQUS software. The pulse-echo method using an L(0, 2) mode impulse guided wave with a central frequency of 70 kHz is applied to evaluate different size circumferential cracks. An experiment was performed for the validation of the numerical analysis results. Both of the results show that the proposed FEM model with piezoelectric elements can efficiently reveal the dynamic behaviors, which can be used in much more precise numerical simulations than the equivalent dynamic displacement loading method.

For tubular structures, ultrasonic guided waves (UGWs) which are closely related to interfacial boundary conditions such as gas, liquid and solid materials, are usually used in damage detection. Due to the different phase materials inside tubes, the interfacial boundary (connection) conditions are variable, which has a great influence on the dispersion-related UGW propagation characteristics. However, most UGW-based damage detection methods only consider the pipeline structures as hollow tubes, ignoring the interfacial boundary condition influences on the UGW propagation. Based on the UGW theory, this paper aims to propose a novel method for describing the UGW propagation characteristics for different interfaces, and lay a foundation for the UGW-based tubular structure damage detection. Based on the Navier’s equation of motion and combined with interfacial boundary conditions and coordinate conditions, the dispersion equations for a hollow steel tube, a tube filled with liquid, and a concrete filled steel tube (CFST) were established, respectively. Under the given conditions of both materials and geometric parameters, the transcendental dispersion equations were established and solved by using a numerical method. The UGW propagation characteristics in different interfaces were classified and discussed, and the dispersion curves of both group and phase velocities are drawn. To validate the efficiency of theoretical and numerical results, three kinds of model tubular structure experiments filled in air (hollow), water and concrete, respectively, were performed based on lead zirconate titanate (PZT) transducer UGWs. The results showed that the UGWs propagation in different interfaces has the dispersion and multi-modes characters, which are not only related to the product of frequency and thickness, but also to the internal dielectric material parameters and interfacial boundary conditions.

Mechanical properties of shape memory alloy (SMA) wires were experimentally researched in this paper, and an energy dissipater made of SMA wire cable was designed and applied in a steel frame structure model by using superelasticity characteristics of SMAs to passively reduce dynamic responses of the steel frame structure under seismic load. For the characteristics of large relative displacements between the stories of the steel frame structure on both diagonal ends and the consideration of initial prestrain effects of the SMA cables, three kinds of the whole control, the part control, and no control of the shaking table tests and numerical simulations were carried, respectively. Through the results of the shaking table test and numerical simulation analysis, the dynamic responses such as the maximum displacement, velocity, and acceleration at the top layer of the steel frame structure applied with SMA cables are significantly decreased compared with the no control case. However, considering the premise of both effectiveness and efficiency, the part control effect is superior to the whole control. In many cases, it can meet the control requirement of reducing the maximum displacement and acceleration, while the superelasticity of SMAs can be sufficiently played, realizing the passive control purposes of the steel frame structure based on the energy dispassion through the application of the SMA cables. The proposed method has broad application prospects in the passive control field of building structures.

A smart aggregate‐based approach is proposed for the concrete compactness detection of concrete filled steel tube (CFST) columns. The piezoceramic‐based smart aggregates (SAs) were embedded in the predetermined locations prior to the casting of concrete columns to establish a wave‐based smart sensing system for the concrete compactness detection purpose. To evaluate the efficiency of the developed approach, six specimens of the CFST columns with the rectangular cross‐section were produced by placing some artificial defects during casting of concrete for simulating various uncompacted voids such as cavities, cracks, and debond. During the test, the time reversal technology was applied to rebuild the received signals and launch the reversed signals again by SAs, to overcome the issue of the lack of the prototype. Based on the proposed nonprototype, two indices of time reversibility (TR) and symmetry (SYM) were applied to relatively evaluate the level of concrete compactness in the range of the two SAs. The experimental results show that the developed method can effectively detect the compactness of concrete in CFST columns.