Optimal Localization of Smart Aggregate Sensor for Concrete Damage Monitoring in PSC Anchorage Zone

This study investigates the feasibility of smart aggregate (SA) sensors and their optimal locations for impedance-based damage monitoring in prestressed concrete (PSC) anchorage zones. Firstly, numerical stress analyses are performed on the PSC anchorage zone to determine the location of potential damage that is induced by prestressing forces. Secondly, a simplified impedance model is briefly described for the SA sensor in the anchorage. Thirdly, numerical impedance analyses are performed to explore the sensitivities of a few SA sensors in the anchorage zone under the variation of prestressing forces and under the occurrence of artificial damage events. Finally, a real-scale PSC anchorage zone is experimentally examined to evaluate the optimal localization of the SA sensor for concrete damage detection. Impedance responses measured under a series of prestressing forces are statistically quantified to estimate the performance of damage monitoring via the SA sensor in the PSC anchorage.

Ponies, Joints, Complexity and the Method of Indifference

An important discipline in biomedical science is the repair of damaged organs by in vitro cultured differentaited stem cells. This article evaluates an article in this field, entitled "The complexity of joint regeneration", by Diloloksumpan et al. (2021), who described a regeneration experiment of artificial damage of the joint of ponies. The experiment failed an I describe the possible cause of this failure by discussing the design of the experiment in the light of J.S.Mill's Method of Difference, published in 1848. I continue with a discussion of the concept of complexity that was introduced by the authors of the paper, by pointing out that three types of complexity may be distinguished; one of these is complicatedness which characterizes the assumed complexity of the joint experiment. I propose that this complicatedness can be solved by the use of the method of difference.

Damage Detection in Composite Skin Stiffener with Hybrid PZT-FO SHM System

A hybrid piezoelectric (PZT)/fibre optic diagnostic system has been developed for damage detection in built up composite structures. The hybrid system uses PZT transducers to actuate the structure and fibre optic (FO) sensors to capture the propagating wave. The diagnostic system will then have the advantages of both PZT and FO sensors. The applicability of the system is then tested for detecting an artificial damage at a skin/stiffener interface of a thick composite structure. The response of the FO sensors is then compared to PZT sensors and presented.

Dynamic Characteristics of a Wood Frame Structure: (II) the Effect of Artificial Damage

A full-scale, three-storey wood frame structure had been tested in-situ to investigate the changes of dynamic properties due to artificial damage. Beams and braces of the test structure were removed, to simulate damage, and then reassembled, to simulate rehabilitation. Free vibration tests were performed during every stage of the tests. The natural frequencies and damping ratios were obtained using modal parameter identification technique based on the Hilbert-Huang Transform. It is shown that, when the structure is damaged or rehabilitated, the natural frequency changes in accord with the structural stiffness in general while the damping ratio varies irregularly.