Infrastructure Engineering - Research Publications
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ItemInfrared thermography detection of delamination in bottom of concrete bridge decks(JOHN WILEY & SONS LTD, 2022-03)Infrared thermography (IRT) has been widely used in detecting the subsurface delamination of bridge deck. However, IRT inspection on delamination zones of the bridge deck which have limited exposure to direct solar radiation (e.g., the bottom surface of the bridge deck) is rather challenging due to the relatively low thermal contrast (∆T) development in these zones. Therefore, the purpose of this study is to conduct a series of experimental studies in conjunction with numerical modeling for investigating the effectiveness of IRT in delamination detection of bridge deck components which are normally not exposed to direct solar radiation. Specially, the effects of different environmental conditions, thickness of bridge deck, and defect characteristics on the absolute thermal contrast (∆T) development were systematically investigated. The results show that IRT can effectively detect the subsurface delamination of concrete bridge deck located in regions that are not exposed to the direct solar radiation. In addition, the development of detectable thermal contrast (>0.5°C) is much dependent on the rate of change in ambient temperature with a suitable detection period between 8 am and 4 pm. Furthermore, it shows that the value of ∆T increases with the increase of bridge deck thickness and delamination size.
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ItemA Simplified Methodology for Condition Assessment of Bridge Bearings Using Vibration Based Structural Health Monitoring Techniques(WORLD SCIENTIFIC PUBL CO PTE LTD, 2021-09-01)The mechanical properties of bridge bearings gradually deteriorate over time resulting from daily traffic loading and harsh environmental conditions. However, structural health monitoring of in-service bridge bearings is rather challenging. This study presents a bridge bearing condition assessment framework which integrates the vibration data from a non-contact interferometric radar (i.e. IBIS-S) and a simplified analytical model. Using two existing concrete bridges in Australia as a case study, it demonstrates that the developed framework has the capability of detecting the structural condition of the bridge bearings in real-time. In addition, the results from a series of parametric studies show that the effectiveness of the developed framework is largely determined by the stiffness ratio between bridge bearing and girder ([Formula: see text], i.e. the structural condition of the bearings can only be effectively captured when the value of [Formula: see text] ranges from 1/100 and 100.
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ItemLife-cycle modelling of concrete cracking and reinforcement corrosion in concrete bridges: A case study(Elsevier BV, 2021-06-15)The development of effective life cycle management strategies for transport infrastructure assets is of importance for meeting the defined public policies and levels of service. In the last decades, much progress has been made in assessing the life-cycle performance of bridges using reliability-based approaches. However, the goal of developing a comprehensive life-cycle performance assessment framework for bridges has not been fully achieved. This is due to the uncertainties surrounding model parameters as well as the correlation between these parameters (e.g. the complex correlation between the reinforcement corrosion and the concrete cracking). It becomes more challenging due to the limited access to bridge inspection data by bridge research communities resulting from confidentiality issues. Using a typical highway concrete bridge as a case study, the present study systematically investigated the impact of concrete crack induced reinforcement corrosion on the serviceability of concrete bridges by developing an engineering reliability-based approach involving an auto-regressive crack propagation model and a steel corrosion prediction model. The model parameters were calibrated using the eight-year inspection data of an operating bridge. The influence of different external environments in the reinforcement corrosion, ultimately the residual life of the bridges, was also investigated through conducting a series of parametric studies. Based on the collected bridge inspection data, the model results predict that, although the surface crack of a RC bridge is repairable through periodic maintenance, the corrosion of the steel bars in the bridge still continues over time with a corrosion rate which depends on different maintenance intervention cycle periods (Tcycle). For example, reducing Tcycle from 12 years to 4 years could potentially prolong the service life of the bridge by around 15 years. The developed model could assist bridge managers to estimate the optimal Tcycle to prolong the service life of bridges.
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ItemThe influence of ambient environmental conditions in detecting bridge concrete deck delamination using infrared thermography (IRT)(Wiley, 2020-04-01)Delamination is a serious form of deterioration in concrete bridge decks. Infrared thermography (IRT) is an advance non‐destructive testing method for concrete bridge deck delamination detection by capturing the absolute thermal contrast (ΔT) on the concrete surface caused by the disruption in heat flow due to subsurface defects. However, as the ambient environmental conditions (e.g. wind velocity and solar radiation) of a bridge could significantly affect the measurement outcomes of IRT, the optimal times for infrared data collection are still unclear. In this paper, a series of experimental and numerical studies were carried out to investigate the effects of the rate of heat flux and wind velocity on ΔT on the surface of bridge decks with the aim of identifying the optimal inspection times for different geometry characteristics of delamination (i.e. size and depth). The developed model is firstly validated by the experimental data and then a series of parametric studies were carried out. The result shows that the heat flux rate plays an important role in the development of ΔT on concrete surface, especially for a relatively shallow and small size delamination. However, the influence of heat flux rate gradually diminishes with the increase in size and depth of delamination. In addition, it demonstrates that there is a positive linear correlation between the total heat energy (external irradiation) and square of the delamination depth. The current research represents an important step towards the development of an effective and efficient way for defect detection using IRT.