Sanaul Huq Chowdhury

A study of the effects of pavement ageing on binder deterioration

This paper discusses the ageing of asphalt binder of long-term pavement performance (LTPP) sites in Southeast Queensland. The effects of pavement age on binder deterioration were examined by performing ‘Shell’ sliding plate micro-viscometer laboratory tests in accordance with Australian and New Zealand Standard AS/NZS 2341.5: 1997. The tests were carried out on bituminous core samples obtained from the LTPP sites to determine the apparent viscosity of the asphalt binder. A binder deterioration model (BDM) was developed by establishing a relationship between the apparent viscosities of the binder with pavement age. The apparent viscosity data generated using the BDM were compared with that computed using the bitumen hardening model developed by Oliver (2003). The two models show a consistent trend in the binder deterioration, and the results were analysed statistically using regression analysis, Root Mean Square Error and t-test methods. The t-test shows that the data generated by the BDM have no significant deviation from the prediction by Olivers model.

A review of performance based maintenance of road infrastructure by contracting

Purpose - Many road authorities considered contracting out road maintenance to the private sector based on performance measures as an alternative and better solution than traditional methods of contracting. It highlights issues of interest to road authorities in the context of saving maintenance costs and managing contracting times effectively. This method is named as performance based maintenance by contracting (PBMC) and has substantial success records in minimizing infrastructure maintenance costs in many developed and developing countries over the last two decades. It has received the attention of researchers and practitioners. However, the literature on PBMC is reasonably high although the concept of PBMC is relatively new. The purpose of this paper is to carry out a comprehensive state of the art review of the literature that has been conducted in the recent years. Design/methodology/approach - A total of 62 published report and journal articles related to performance based maintenance by contracting for road network system has been analysed and reviewed in this paper. Findings - This paper analyses the literature on PBMC and presents examples of developed and developing countries that have been successfully maintaining their road network systems using PBMC as their preferred method of contracting. Practical implications - The potential of reducing maintenance costs, increasing the quality of works and reducing the chance of corruption in the long run in developing countries are the challenging issues for PBMC, which needs more attention. This paper can be used as a base or platform for future research in the area of PBMC such as developing optimal policies and cost models. Originality/value - This paper would be useful for the research on PBMC. It would be beneficial for the engineers or professionals in improving the performance of road maintenance and management.

Damping Formulae for Reinforced and Partially Prestressed Concrete Beams

A full-size test program was carried out on 26 simply-supported and continuous reinforced and partially prestressed concrete beams to study the cracking behaviour and damping characteristics of concrete beams. The beams were subjected to free vibration tests and logarithmic decrement values corresponding to each load level were measured. Separate regression analyses on the reinforced and the partially prestressed beams were undertaken. These analyses resulted in two separate empirical formulae for predicting the logarithmic decrement of damping in reinforced and in partially prestressed beams. Comparison with test results from all 26 beams indicates that the predictions are accurate. It is also found that the damping formula for reinforced beams is applicable to both single and continuous spans. The proposed damping formulae predict damping from the residual crack widths of the beams. As such, formulae developed for predicting residual crack widths from given variables defining the beams and their deflection-span ratios are also reported.

Modeling the Postflood Short-Term Behavior of Flexible Pavements

The January 2011 flood in Queensland caused severe damage to road infrastructures, which presented new challenges for the efficient management of the roads. To date, no deterioration model can accurately predict the impact of floods on pavements. To understand the impact of the January 2011 flood on the structural performance of flood-affected pavements, falling weight deflectometer (FWD) deflection data on flood-affected roads managed by the Brisbane City Council (BCC) and Roads and Maritime Services, New South Wales (RMS, NSW), Australia, were collected and examined. This paper proposes a deterministic model that expresses structural strength of pavements as a function of time. The model predicts the short-term behavior of a flexible pavement immediately after flooding. A comparison of before- and after-flood data, and flooded and nonflooded sections of the same road, indicates a consistent trend of decrease in strength due to its sustained submergence under flood water. The literature review indicates that structural strength deterioration was also observed for the pavements in New Orleans and Louisiana following Hurricanes Katrina and Rita in 2005. However, a trend of strength gain and even, in some cases, strength loss was also observed in the BCC data, which were collected 2 and 4 years postflood. The flood-affected pavements lost their structural strength faster than the predicted deterioration rate for which the road was designed. Importantly, the proposed model would facilitate the pavement engineers to quantify the postflood rapid deterioration of the structural strength. The model is sufficiently robust and can be adapted to other regions by calibrating for the local condition.

Challenges for achieving sustainable flood risk management

This paper presents the challenges for effectiveness and sustainability of flood risk management strategies and technologies by critically reviewing flood management practices. The study reveals that reliable flood prediction is limited by the characterisation of floods that have multiple causes and hydrological uncertainties due to variability in climate and river morphology. Moreover, changing land use in floodplains and the potential of creating new risks limit the risk assessment and evaluation process of flood control projects. Hence, sustainability analysis mechanisms, including ‘dynamic sustainability’ concepts, should be adopted in the flood management planning process. Investigations into the proportional contribution of structural and non-structural measures to reduce total flood risk could assist in better decision making. Gaining improved understandings of the perception on flood risk and safety, and risk communication methods, for present and future stakeholders is crucial. Extensive research on the above challenges would reveal pathways for developing sustainable flood risk management strategies.

New approaches for modelling subgrade nonlinearity in thin surfaced flexible pavements

Abstract The primary objective of this paper is to present new methods in characterising flexible pavements that possess nonlinear subgrade behavior using deflection data from falling weight deflectometer (FWD). The two techniques to be introduced are Simplified Deflection Modeling and Deflection Ratio (DefR) approach. FWD deflection data can be modelled accurately using an exponential curve in a mathematical form of Y = K1 exp (−r/K2). K1 is equal to deflection at D0 in micron and K2 is the structural parameter at the respective sensor location. K2 parameter is found to have a direct relationship with the material constant, value of the subgrade and it is taken as a measurement of the nonlinearity of the pavement layer. As K2 increases and approaches 500, the pavement structure is observed to possess linear elastic behaviour. In the second method, the DefR is defined as the ratio of the FWD deflection of a sensor divided by the deflection of the preceding sensor. For pavements that exhibit nonlinear subgrade behavior, the DefR shows an increasing trend for FWD sensors located at 300mm and beyond. The two techniques have provided alternative approaches for modelling subgrade nonlinearity.

Establishment of calibration factors for pavement roughness deterioration model in southeast Queensland

Abstract This paper presents the outcomes of the research in establishing the calibration factors for pavement roughness deterioration model for six local council regions in southeast Queensland (SEQ). To achieve the objective, a large number of long-term pavement performance (LTPP) test sites were set up throughout the six SEQ regions. The methodology for the selection of the SEQ-LTPP test sites and the rationale behind the design of the LTPP site selection matrix are discussed. Pavement condition data were collected from the LTPP test sites over a period of five years. Modelling of the pavement deterioration at the test sites were carried out using the SMEC pavement management system (SMEC PMS) with HDM-III deterioration models. The aim was to determine the most appropriate HDM-III roughness deterioration factors for the six regions covered in the study. Three statistical techniques, namely, linear rate of roughness deterioration, regression analysis and statistical t test approach, were used in analysing the roughness data obtained from the LTPP sites and the predicted roughness data generated by the SMEC PMS. The statistical analysis established the accuracy of the prediction generated by a pavement deterioration dataset and confirmed whether the prediction yields significant or no significant deviation from the observed roughness data. Consequently, a set of pavement deterioration factors has been recommended for use in the SMEC PMS for SEQ regions.

Concept Paper: Developing Pavement Structural Deterioration Curves

An SN (structural number) can be calculated for a road pavement from the properties and thicknesses of the surface,basecourse, sub-base and subgrade. Historically, the cost of collecting structural data has been very high. Data were initially collectedusing Benkelman Beams and now by FWD (falling weight deflectometer). The structural strength of pavements weakens over timedue to environmental and traffic loading factors but due to a lack of data, no structural deterioration curve for pavements has beenimplemented in a PMS (pavement management system). IRI (international roughness index) is a measure of the road longitudinalprofile and has been used as a proxy for a pavement’s structural integrity. This paper offers two conceptual methods to developPSDC (pavement structural deterioration curves). Firstly, structural data are grouped in sets by design ESA (equivalent standardaxles). An ISN (“initial” SN), SNI (intermediate SN) and a TSN (terminal SN), are used to develop the curves. Using FWD data, theISN is the SN after the pavement is rehabilitated (Financial Accounting “Modern Equivalent”). Intermediate SNIs, are SNs other thanthe ISN and TSN. The TSN was defined as the SN of the pavement when it was approved for pavement rehabilitation. The secondmethod is to use TSD (traffic speed deflectometer) data. The road network already divided into road blocks, is grouped by trafficloading. For each traffic loading group, road blocks that have had a recent pavement rehabilitation, are used to calculate the ISN andthose planned for pavement rehabilitation to calculate the TSN. The remaining SNs are used to complete the age-based or if available,historical traffic loading-based SNIs.

Lecture capture use in engineering education: Influence of students' social and behavioral factors and teachers' perceptions

This paper discusses the influence of students’ social and behavioral features on lecture capture use in the learning of engineering courses, as well as teachers’ perceptions of pedagogical changes and students’ performance. Results show that the students’ perceptions about lecture capture are highly positive in terms of improving learning and academic performance. With respect to behavioral factors like attention deficit, the study suggests that a significant number of students having difficulties in maintaining attention during lectures and rely on lecture capture for further understanding. With respect to social factors, variation in the use of lecture capture has also been observed between native and non‐native English speaking students, and in students with different levels of past experience in using lecture capture. Lecturers of these engineering courses have expressed optimism about using lecture capture, and have raised concerns about restrictive teaching styles, and the requirement for technological improvements and adequate training.

APPLICATION OF A SUSTAINABILITY ASSESSMENT FRAMEWORK FOR FLOOD MITIGATION PROJECTS: A CASE STUDY ON A FLOOD LEVEE PROJECT IN AUSTRALIA

Sustainable development of floodplains is closely linked to the sustainable flood mitigation measures. Various sustainability assessment (SA) methods to evaluate the influence of policies, plans or projects towards sustainable development have been emerging in recent years; however, most of them are national or regional policies and programs. Very few research studies have been carried out for sustainability assessment of flood mitigation projects. This paper presents the concept of a proposed sustainability assessment framework for flood mitigation projects and its application to a recently implemented flood levee project in Australia. This research has employed a review of the life cycle of flood mitigation projects, sustainability assessment (SA) methodologies, consultations with experts, and a case study of flood mitigation projects. In line with the project life cycle, the proposed sustainability assessment framework is developed incorporating five stages: a) contextualizing the project, b) SA during planning and implementation, c) SA during flood event, d) SA at periodic intervals, and e) SA at modification phase or changing to a new project. The application of the SA framework to the first two stages of a flood levee project demonstrates how the best suitable alternative levee option can be chosen in the planning stage by determining a sustainability index (SI) of the possible alternatives using a set of sustainability indicators. The study also shows achievement towards sustainability of the finally implemented project can be compared with the originally planned project using the SA framework. The application of the SA framework suggests the potential for better decision making for individual flood mitigation projects, taking into account the sustainable outcome of the project as well as linking this to regional sustainable development