This paper presents the results of a study into the use of pattern recognition as a method for detecting damage in structures.Pattern recognition is achieved by the use of artificial neural networks (ANNs); however, these require careful design because the number of hidden layers and the number of neurons in each hidden layer are critical to the ANN's performance.In the current study, a Bayesian model class selection method was employed to select an optimal ANN model class that avoids ad hoc assumptions and subjective decisions in the ANN design.The objective of the research was to provide an extended study of the proposed method using the IASC-ASCE Structural Health Monitoring (SHM) Phase II Simulated Benchmark Structure.Damage-induced modal parameter changes were used as a pattern feature in damage detection.Analysis showed that the proposed method is able to successfully identify damages in a benchmark structure.

Abstract In the design of prestressed concrete fl exural members it is necessary to allow for the longterm effects of creep and shrinkage, particularly in regard to defl ections and prestress loss. ...

In reinforced concrete construction, deflection control is an important performance criterion for its serviceability and sustainability. In this paper, a finite element model dedicated to the calculation of the overall stiffness of reinforced concrete beams is extended in order to take into account steel-concrete interface damage due to excessive live loading resulting from cover-controlled cracking. The effect of cover-controlled cracking is taken into account by implementing a damage variable to reduce the bond at the steel-concrete interface. In addition, a criterion for the initiation of cover-control cracks based on a peak value of the steel stress at the crack location is also defined.

Round timbers are extensively used as utility poles in Australia for electricity distribution and communication. Lack of information on their conditions results in great difficulties on asset management for industries. Despite the development of various non-destructive testing (NDT) techniques for evaluating the condition of piles, few NDTs are reported for applications on timber poles. This paper addresses challenges and issues on development of NDTs for condition assessment and embedded length of timber poles. For this paper, it is mainly focusing on determining the embedded length of the pole considering loss of the sufficient embedment length is a main factor compromising capacity and safety of timber poles. Since it is impractical for generating longitudinal waves by impacting from the top of poles, utilising flexural wave from side impact on poles becomes attractive. However, the flexural wave is known by its highly dispersive nature. In this paper, one dimensional wave theory, guided wave theory and advanced signal processing techniques have been introduced in order to provide a solution for the problem. Two signal processing techniques, namely short kernel method and continuous wavelet transform, have been investigated for processing flexural wave signals to evaluate wave velocity and embedment length of timber poles in service.

The structural responses and vibration properties such as frequencies and mode shapes are directly related to the structural mass and stiffness. Changing structural conditions will affect the structural responses and vibration properties. Structural conditions can thus be identified through measurements of structural vibration. However, certain uncertainties associated with structure models, changing ambient environmental conditions, changing loading conditions, equipment noises and various signal processing techniques used in extracting structural vibration properties, etc. is inevitable. The influences of these uncertainties on structural vibration properties might be more significant than that of the structural damage, therefore, cause false identification or result in the true structural damage not identifiable. This paper studies the applicability and reliability of a few popularly used modal identification methods including time-domain, frequency-domain and time-frequency domain methods for civil structural system identification. The results indicate that on average a 2% to 3% error tends to be yielded by using different signal processing techniques for vibration frequencies identification when the signal is not heavily noise contaminated, which should be taken into account when estimating the damage detection results. The applicability of the time-frequency domain methods to the identification of time-varying system either with sudden change or continuous variance is also discussed.

This paper presents techniques and instrumentation employed in the measurement of dynamic structural properties of tall buildings and structures, long-term monitoring of their responses in strong winds, and vibration mitigation systems installed in actual buildings and structures. The merits and limitations of these techniques are discussed. Natural frequencies of vibration, deflected mode shapes and damping values can be determined reliably through dynamic measurements on actual buildings, and these results provide invaluable validations of numerical modelling techniques and generalised prediction formulae. The improved accuracy of prediction processes, coupled with a better understanding of building performance in strong winds, through long-term building monitoring, can lead to significant cost savings in the wind-resistant design and construction of tall buildings.

The confining effect of infill panels on the hysteresis performance of the external beam-column joints has been studied experimentally. Four hinged joints and two rigid joints have been tested under cyclic loading with the interaction of infill panels on both the sides of the joints. The infill panels have remained subjected to different compression loads applied either at centre or at the end positions of the infill panels. This effect of infill panels has shown an increase with the increase in amount of compression load. The cyclic evaluation of hinged joints with infill panels has been used to determine the shear resistance of infill panels which has not only depended upon the amount but also on the location of compression load. It has been observed that the load-deformation diagrams of rigid beam-column joints with infill panels manifest a significant increase in the capacity of the joint by confining the joint with infill panels. The obtained capacity has almost been the result of the combined effects of two independent systems, ie. bare rigid joint system and compressed infill panel system.

A parametric experimental study has been conducted to investigate the effect of silica fume on the fracture properties of high performance concrete (HPC), with five silica fume contents (1.5%, 3%, 6%, 9% and 12%) used. The results indicate that the addition of silica fume has greatly improved the fracture parameters of HPC, such as fracture toughness, fracture energy, effective crack length, the maximum mid-span deflection, the critical crack opening displacement and the maximum crack opening displacement of concrete. The fracture parameters of HPC containing silica fume are increasing gradually with the increase of silica fume content when the silica fume content increases from 0% to 3%, while, the fracture parameters begin to decrease after the silica fume content increases beyond 3%. However, the values of the fracture parameters of HPC with the silica fume content below 12% are still higher than that of the concrete without silica fume. It seems a small content of silica fume has an advantage of improvement of the fracture properties of HPC, while an overlarge silica fume content may adversely affect the fracture properties of HPC.