Infrastructure Engineering - Research Publications
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ItemNo Preview AvailableInfluences of variability and uncertainty in vertical and horizontal surface roughness on articular cartilage lubrication(PERGAMON-ELSEVIER SCIENCE LTD, 2022-09)BACKGROUND AND OBJECTIVES: Cartilage surface roughness has significant implications on joint lubrication. However, the effects of the variability in surface roughness in different directions (especially in horizontal direction) in mixed-mode lubrication have not been fully investigated and relevant research work in this field is limited. This study presents a probabilistic numerical approach to investigate the influence of variability and uncertainty of Root-Mean-Square (RMS) roughness heights (vertical roughness) and roughness correlation lengths (horizontal roughness) on cartilage lubrication. METHODS: The synthetic surface topographies with typical ranges of vertical and horizontal roughness characteristics were firstly input to a coupled cartilage contact model. A response surface was then constructed using the input roughness parameters and the output coefficient of friction (CoF). Finally, a large number of independent or correlated roughness samples were generated for computing the probability of mixed-mode lubrication failure (PoF), which was defined as CoF > 0.27 (corresponding to a 90% loss of fluid support in the contact interface). RESULTS: Both independent RMS roughness heights and correlation lengths are correlated positively with CoF. This indicates that the increase of the vertical surface roughness could exacerbate cartilage wear, whereas increasing surface roughness in horizontal direction (i.e., reducing correlation lengths) could retain gap fluid that aids mixed-mode lubrication. Importantly, it shows that CoF is dominant by RMS roughness height. The uncertainty in the independent correlation lengths may lead to the underestimation of PoF. By simulating osteoarthritic surface roughness with a strong correlation between RMS roughness heights and correlation lengths, the value of PoF could reach 70-99%. CONCLUSION: This study highlights the significance of incorporating the mutual relations between the surface roughness in vertical and horizontal directions into research, and the findings could potentially contribute to the design of biomimetic cartilage surfaces for the treatment of osteoarthritis.
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ItemStructural Health Monitoring of Bridges Using Advanced Non-destructive Testing Technique(Springer, Singapore, 2020-01-01)This paper presents an integrated framework for structural health monitoring of bridges by using advanced non-destructive testing (NDT) technique in conjunction with computational modelling. First, the structural characteristics of the Eltham Trestle Bridge under train loading were monitored using the combination of the 3D optical measurement system and IBIS-S. The results demonstrate that, in conjunction with computational modelling, the NDT can capture the structural health conditions of the bridge by analysing the natural frequencies and deformation profiles of the critical members of the bridges. Then, the developed framework also takes into account the impact of extreme events (e.g. truck impacts and earthquakes) by using a reliability-based model. Finally, using the Montague Street Bridge as a case study, it shows that proposed framework has the capability of predicting the residual life of a bridge subject to both progressive deterioration and extreme events throughout its service life.
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ItemAutomation in structural health monitoring of transport infrastructure(Springer Singapore, 2021-01-01)Roads are among the most important assets in the world. Road structure improvements make a crucial contribution to economic development and growth and bring important social benefits. Automation in structural health monitoring allow the accurate prediction of ongoing damage caused by long-term traffic loading. This permits optimal road structure management and ensures the longevity and safety of road structures. This chapter discusses a variety of advanced automation techniques in structural health monitoring of road structures, such as data acquisition, data processing, and life-cycle assessment. It demonstrates that the implementation of automation in road asset management can increase the productivity and extend the service life of road structures, and enhance the durability of crucial road structures and increase transport infrastructure sustainability.
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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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ItemInfrared Thermography for Detecting Subsurface Defects of Concrete Structures(Springer Singapore, 2020-12-23)Delamination is one of the serious types of deterioration in reinforced concrete structures. It could cause concrete spalling, exposed steel bars, and ultimately affects the structural integrity of concrete structures. Infrared thermography (IRT) is a non-destructive technique which could potentially detect the delamination by capturing thermal contrast (∆T) on concrete surface caused by the heat flow disruption within the concrete due to subsurface anomalies. However, the optimum time and environmental conditions for IRT data collection are still unclear. In this study, an experimentally validated numerical model was developed to investigate the effect of a range of environmental conditions and defect characteristics on the IRT inspection outcomes. The results show that, under direct solar irradiation, the total heat flux input plays an important role in the development of thermal contrast ∆T instead of flux rate. Furthermore, delamination depth and size are two critical parameters that affect IRT results.
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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 investigation of bone fracture healing under intramembranous and endochondral ossification(ELSEVIER, 2021-06)After trauma, fractured bone starts healing directly through bone union or indirectly through callus formation process. Intramembranous and endochondral ossification are two commonly known mechanisms of indirect healing. The present study investigated the bone fracture healing under intramembranous and endochondral ossification by developing theoretical models in conjunction with performing a series of animal experiments. Using experimentally determined mean bone densities in sheep tibia stabilized by the Locking Compression Plate (LCP) fixation system, the research outcomes showed that intramembranous and endochondral ossification can be described by Hill Function with two unique sets of function parameters in mechanical stimuli mediated fracture healing. Two different thresholds exist within the range of mechanical simulation index which could trigger significant intramembranous and endochondral ossification, with a relatively higher bone formation rate of endochondral ossification than that of intramembranous ossification. Furthermore, the increase of flexibility of the LCP system and the use of titanium LCP could potentially promote uniform bone formation across the fracture gap, ultimately better healing outcomes.
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ItemInvestigation of role of cartilage surface polymer brush border in lubrication of biological joints(Springer Science and Business Media LLC, 2021)Although experimental evidence has suggested that the polymer brush border (PBB) on the cartilage surface is important in regulating fluid permeability in the contact gap, the current theoretical understanding of joint lubrication is still limited. To address this research gap, a multiscale cartilage contact model that includes PBB, in particular its effect on the fluid permeability of the contact gap, is developed in this study. Microscale modeling is employed to estimate the permeability of the contact gap. This permeability is classified into two categories: For a gap size > 1 µm, the flow resistance is assumed to be dominated by the cartilage roughness; for gap size < 1 µm, flow resistance is assumed to be dominated by the surface polymers extending beyond the collagen network of the articular cartilage. For gap sizes of less than 1 µm, the gap permeability decreases exponentially with increasing aggrecan concentration, whereas the aggrecan concentration varies inversely with the gap size. Subsequently, the gap permeability is employed in a macroscale cartilage contact model, in which both the contact gap space and articular cartilage are modeled as two interacting poroelastic systems. The fluid exchange between these two media is achieved by imposing pressure and normal flux continuity boundary conditions. The model results suggest that PBB can substantially enhance cartilage lubrication by increasing the gap fluid load support (e.g., by 26 times after a 20-min indentation compared with the test model without a PBB). Additionally, the fluid flow resistance of PBB sustains the cartilage interstitial fluid pressure for a relatively long period, and hence reduces the vertical deformation of the tissue. Furthermore, it can be inferred that a reduction in the PBB thickness impairs cartilage lubrication ability.
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ItemComputational study on synovial fluid flow behaviour in cartilage contact gap under osteoarthritic condition(Elsevier, 2020-08-01)This study numerically investigates the pathological changes of fluid flow in cartilage contact gap due to the changes in cartilage surface roughness and synovial fluid characteristics in osteoarthritic (OA) condition. First, cartilage surface topographies in both healthy and OA conditions are constructed using a numerical approach with consideration of both vertical and horizontal roughness. Then, constitutive equations for synovial fluid viscosity are obtained through calibration against previous experimental data. Finally, the roughness and synovial fluid information are input into the gap flow model to predict the gap permeability. The results show that the rougher surface of OA cartilage tends to decrease gap permeability by around 30%–60%. More importantly, with the reduction in gap size, the decrease in gap permeability becomes more significant, which could result in an early fluid ultrafiltration into the tissue. Moreover, it is demonstrated that the pathological synovial fluid has more deleterious effects on the gap permeability than the OA cartilage surface, as it could potentially increase the gap permeability by a few hundred times for pressure gradients less than 106 Pa/m, which could inhibit the fluid ultrafiltration into the tissue. The outcomes from this research indicate that the change in fluid flow behaviour in contact gap in OA condition could significantly affect the function of articular joints.