A Reusable PZT Transducer for Monitoring Initial Hydration and Structural Health of Concrete

During the construction of a concrete structure, strength monitoring is important to ensure the safety of both personnel and the structure. Furthermore, to increase the efficiency of in situ casting or precast of concrete, determining the optimal time of demolding is important for concrete suppliers. Surface bonded lead zirconate titanate (PZT) transducers have been used for damage detection and parameter identification for various engineering structures over the last two decades. In this work, a reusable PZT transducer setup for monitoring initial hydration of concrete and structural health is developed, where a piece of PZT is bonded to an enclosure with two bolts tightened inside the holes drilled in the enclosure. An impedance analyzer is used to acquire the admittance signatures of the PZT. Root mean square deviation (RMSD) is employed to associate the change in concrete strength with changes in the PZT admittance signatures. The results show that the reusable setup is able to effectively monitor the initial hydration of concrete and the structural health. It can also be detached from the concrete for future re-use

Brief Overview of Bioinformatics Activities in Singapore

10.1371/journal.pcbi.1000508PLoS Computational Biology5

Applications of smart materials in health monitoring of civil infrastructures

446 p.The last few decades have witnessed the construction of vast infrastructural facilities in Singapore and other parts of the world. Now, the ageing of these structures is creating maintenance problems and increasingly prompting the development of automated, real-time and online structural health monitoring (SHM) and non-destructive evaluation (NDE) systems, which can provide cost-effective alternative to the traditional visual inspection method. Similar necessity is increasingly felt for civil and military aircraft, spaceships, heavy machinery, trains, and so on, where long endurance combined with intensive usage causes gradual but unnoticed deterioration, often leading to unexpected disasters, such the as the Columbia Shuttle breakdown.RG 8/0

Development of an intelligent CPM scheduling system for building construction management

165 p.Construction scheduling essentially entails the generation of a 'map' of operations of how the project is to be carried out. The construction schedule, or the 'map', consists of a breakdown of the project into a series of activities leading to the completion of the project. These activities are first assigned durations, and then sequenced in a certain logical manner to ensure the successful completion of the project according to plan.RP 4/8

'Hot spot' stresses of K tubular joints subjected to combined loadings

An approach has been proposed to verify, and modify if necessary, the conventional method for determining the peak 'hot spot' stresses of various configurations of tubular joints subjected to combined loadings. A typical K tubular joint, which was subjected to various loading conditions, was employed to illustrate the proposed approach. It is found that the accuracy of the peak 'hot spot' stresses estimated by the conventional method for combined loadings are closely related to the types of loading condition involved. This is due to the possible change in peak stress locations and directions when various basic load types are combined. The peak 'hot spot' stresses of some combined loadings are significantly over estimated by the conventional method and, thus, can be reduced in order to provide accurate data for fatigue analysis. © 1993.link_to_subscribed_fulltex

Effect of varying axial load under fixed boundary condition on admittance signatures of electromechanical impedance technique

In recent years, researchers in the field of structural health monitoring have been rigorously striving to replace the conventional nondestructive evaluation techniques with the smart material–based structural health monitoring techniques. These techniques possess distinct advantages over the conventional techniques, such as capable of providing autonomous, real-time, reliable, and cost-efficient monitoring. For instance, the electromechanical impedance technique employing smart piezo-impedance transducer (lead zirconate titanate) is known for its sensitivity in detecting damage. The admittance signatures of the electromechanical impedance technique for structural health monitoring are susceptible to variation in the static load applied on the host structure, which should not be ignored. This article presents a series of experimental, analytical, and numerical studies conducted to investigate the effect of varying axial load in the presence of fixed boundary condition on the admittance signatures. Theoretically, the extensional vibration is not affected by any static axial load acting in the same direction. However, it is useful in identifying the effect of stiffening caused by the boundary condition upon increase in the axial force, which contributes to the discrepancy between the experiments and the analytical models. This study suggests that the effect of boundary condition is substantial, which should be carefully considered in real-life application of the electromechanical impedance technique for structural health monitoring

Parametric study of welded tubular joints

In this study, experimental and numerical research has been carried out to increase the data on the ultimate strength of welded multiplanar joints and to provide a better basis for the designof multiplanar joints.RGM 11/9