Toward effective structural identification of medium-rise building structures

Structural Identification (St-Id) is the process of constructing and calibrating a physics-based model based on the measured static and/or dynamic response of the structure. Over the last two decades, although the St-Id methods have become increasingly popular amongst civil-structural engineering communities, most complete and successful applications are often found with flexible structures such as long-span bridges and towers. Very few comprehensive studies were reported on building structures, especially those with medium-rise characteristics which are often associated with complicated analytical modelling and different degrees of parameter uncertainties. To address this need, this paper presents an in-depth study on St-Id of a benchmark medium-rise building firstly demonstrating the importance of developing appropriate initial analytical models that can be used for the automated model calibration techniques. Then, a novel parametric study based sensitivity analysis approach is introduced to identify tuning parameters as well as their appropriate ranges to maximise the correlation of the calibrated model whilst preserving the physical relevance of the calibrated model. Modal data of the first few modes measured under ambient vibration conditions are used in this study

Damage assessment of concrete gravity dams using vibration characteristics

Vibration-based Structural Health Monitoring (VBSHM) has emerged as a feasible technique in long-term monitoring, structural performance evaluation and damage assessment of civil structures. As an important as-pect of the complete VBSHM system, over the last three decades, many vibration-based damage detection methods have been developed for buildings and bridges. However, the application of these techniques to con-crete gravity (CG) dams has been limited. In the present study, damage indices based on changes in modal flexibility and modal strain energy are suitably enhanced to be applicable for plane-strain structures. They are then used to investigate the feasibility of detecting and locating damage in a finite element CG dam model without noise effects. Results show that the enhanced damage indices can be promising for locating damage in the upstream part of CG dams by using only the first lateral mode of vibration. In addition, it is necessary to monitor both horizontal and vertical mode shape components and use these for structural damage diagnoses in CG dams

Fiber Bragg grating strain modulation based on nonlinear string transverse-force amplifier

2012-2013 > Academic research: refereed > Publication in refereed journalpublished_fina

Enhancing temperature sensitivity using cyclic polybutylene terephthalate- (c-PBT-) coated fiber bragg grating

A polybutylene terephthalate (c-PBT) coating for enhancing the temperature sensitivity of a fiber Bragg grating- (FBG-) based sensor is proposed and demonstrated. The coating is seen to increase the sensitivity of the proposed sensor by a factor of approximately 11 times as compared to a bare FBG, giving a Bragg wavelength shift of 0.11 nm/°C with an operating temperature ranging from 30°C to 87°C. The proposed sensor is also easy to fabricate as compared to other similarly coated FBG sensors, giving it a significant advantage for field applications with the added advantage of being easily reformed to fit various housings, making it highly desirable for multiple real-world applications

Very sensitive fiber Bragg grating accelerometer using transverse forces with an easy over-range protection and low cross axial sensitivity

2013-2014 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Optical fiber Bragg grating-based pressure sensor for soil monitoring applications

An optical-based pressure sensor for a 150 × 150 mm surface was designed and fabricated. The sensor utilizes a fiber Bragg grating (FBG) attached to a 30 × 30 × 30 mm actuator as the pressure sensing mechanism. The middle section of the actuator, which is circular, can bend into an elliptical form and, in the process, pull the FBGP via both ends when force or pressure is applied, thus converting the pressure applied to its surface into a wavelength shift. In laboratory testing, a sensitivity of 0.152 nm∕kPa was obtained. Subsequently, the pressure sensor was tested in the field by burying it 20 cm underground to measure soil pressure, while another FBG was spliced in series to the FBGP to compensate for temperature variations. Testing shows that the proposed design can realize a compact optical-based pressure sensor with enhanced soil monitoring applications such as dynamic soil pressure caused by soil movement

Acoustic keyword spotting in speech with applications to data mining

Keyword Spotting is the task of detecting keywords of interest within continu- ous speech. The applications of this technology range from call centre dialogue systems to covert speech surveillance devices. Keyword spotting is particularly well suited to data mining tasks such as real-time keyword monitoring and unre- stricted vocabulary audio document indexing. However, to date, many keyword spotting approaches have su®ered from poor detection rates, high false alarm rates, or slow execution times, thus reducing their commercial viability. This work investigates the application of keyword spotting to data mining tasks. The thesis makes a number of major contributions to the ¯eld of keyword spotting. The ¯rst major contribution is the development of a novel keyword veri¯cation method named Cohort Word Veri¯cation. This method combines high level lin- guistic information with cohort-based veri¯cation techniques to obtain dramatic improvements in veri¯cation performance, in particular for the problematic short duration target word class. The second major contribution is the development of a novel audio document indexing technique named Dynamic Match Lattice Spotting. This technique aug- ments lattice-based audio indexing principles with dynamic sequence matching techniques to provide robustness to erroneous lattice realisations. The resulting algorithm obtains signi¯cant improvement in detection rate over lattice-based audio document indexing while still maintaining extremely fast search speeds. The third major contribution is the study of multiple veri¯er fusion for the task of keyword veri¯cation. The reported experiments demonstrate that substantial improvements in veri¯cation performance can be obtained through the fusion of multiple keyword veri¯ers. The research focuses on combinations of speech background model based veri¯ers and cohort word veri¯ers. The ¯nal major contribution is a comprehensive study of the e®ects of limited training data for keyword spotting. This study is performed with consideration as to how these e®ects impact the immediate development and deployment of speech technologies for non-English languages

Non-destructive testing of timber bridges

It is recommended that timber bridges are inspected at a minimum of two year intervals to determine and rate the condition of the structure to enable the scheduling of maintenance and determine the effectiveness of past maintenance treatments. During these inspections it is necessary that a visual inspection be undertaken in conjunction with a drilling survey of all major structural elements. Unfortunately current methods of drilling can promote the deterioration of these structural elements and the reserves of timber that are suitable for bridge construction and maintenance are scarce. It is therefore imperative that asset managers consider using alternative methods such as Non-Destructive Evaluation (NDE) during routine inspections. The Resistograph is a quasi non-destructive evaluation tool that was developed for testing the soundness of European softwoods that is now available in Australia. This paper will present the results of testing the resistograph on timber hardwood bridge

An experimental investigation of multisolitons using an erbium doped fiber amplifier and a fiber optic ring resonator

We have successfully generated the mutisoliton pulses using a Gaussian pulse in a fiber optic ring resonator incorporating an erbium-doped fiber (EDF) and a semiconductor optical amplifiers (SOAs). The multisoliton memory time within the system is also measured. Initially, the Gaussian input pulse is pumped and amplified through the EDF and the SOAs, respectively. The suitable experimental values, such as drive current, coupling power, and the fiber ring radius, are arranged to generate the multisoliton pulses. In application, the wider multisoliton band can be generated by adjusting the suitable system parameters. Results obtained have shown that the multisoliton with a free spectrum range and spectrum width of 2.4 and 0.96 nm is achieved. The memory time and the maximum soliton output of 15 min and of 5.94 dBm, respectively, are noted