Infrastructure Engineering - Research Publications

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    Multi-Criteria Analysis of a Developed Prefabricated Footing System on Reactive Soil Foundation
    Teodosio, B ; Bonacci, F ; Seo, S ; Baduge, KSK ; Mendis, P (MDPI, 2021-11-01)
    The need for advancements in residential construction and the hazard induced by the shrink–swell reactive soil movement prompted the development of the prefabricated footing system of this study, which was assessed and compared to a conventional waffle raft using a multi-criteria analysis. The assessment evaluates the structural performance, cost efficiency, and sustainability using finite element modelling, life cycle cost analysis, and life cycle assessment, respectively. The structural performance of the developed prefabricated system was found to have reduced the deformation and cracking by approximately 40%. However, the cost, GHG emission, and embodied energy were higher in the prefabricated footing system due to the greater required amount of concrete and steel than that of the waffle raft. The cost difference between the two systems can be reduced to as low as 6% when prefabricated systems were installed in a highly reactive sites with large floor areas. The life cycle assessment further observed that the prefabricated footing systems consume up to 21% more energy and up to 18% more GHG emissions. These can significantly be compensated by reusing the developed prefabricated footing system, decreasing the GHG emission and energy consumption by 75–77% and 55–59% with respect to that of the waffle raft.
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    Design of prefabricated footing connection using a coupled hydro-mechanical finite element model
    Teodosio, B ; Baduge, KSK ; Mendis, P (ERNST & SOHN, 2021-11-23)
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    Microstructural Investigation of High-Volume Fly Ash Composites Containing Nano-Calcium Silicate Hydrate Crystals
    Zhou, Z ; Sofi, M ; Sabri, Y ; Liu, J ; Kang, S ; Mendis, P (ASCE-AMER SOC CIVIL ENGINEERS, 2021-12-01)
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    Effect of wind speed and direction on facade fire spread in an isolated rectangular building
    Abu-Zidan, Y ; Rathnayaka, S ; Mendis, P ; Nguyen, K (Elsevier, 2022-05-01)
    This paper investigates the influence of wind speed and direction on external fire spread in an isolated rectangular building using computational fluid dynamics models validated with wind tunnel data and facade fire tests. Two wind speeds (2 m/s, 4 m/s) are considered for each of four wind directions (0°, 45°, 90°, 180°) and compared to a reference case of no wind. Results indicate that facade fire spread is heavily influenced by the near-wall flow fields generated by the building geometry. These flow fields explain counterintuitive findings such as the upstream tilting of flames under the influence of reverse flow near the side walls. The presence of external wind was found to inhibit the initial development of facade fires, but can greatly exacerbate fire spread once the fire has fully developed. The largest fire occurred for the case of no wind (7.5 GJ in 15 min) while the smallest fire occurred for the 4 m/s diagonal wind case (2.2 GJ). An additional case with temporally varying wind conditions demonstrated a 50% increase in fire spread area compared to no wind. The study provides valuable insight into wind and fire interaction in building facades that can help improve fire safety of buildings.
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    Comparative assessment of embodied energy of recycled aggregate concrete
    Wijayasundara, M ; Crawford, RH ; Mendis, P (Elsevier, 2017)
    Concrete waste can be recycled to produce an aggregate product; referred to as recycled concrete aggregate (RCA). While RCA is mainly used as a road base filler material, it has the potential to replace natural coarse aggregate (NA) in structural concrete. In determining the environmental performance of the resultant concrete product from this substitution, referred to as recycled aggregate concrete (RAC) against its counterpart, natural aggregate concrete (NAC), it is important to consider the effects of the entire life cycle including the upstream processes associated with each. This paper evaluates “cradle-to-gate” embodied energy (EE) of RAC received at a construction site, in comparison to NAC, using the input-output-based hybrid approach, using an Australian context. The paper constructs a model to evaluate EE of RAC and analyses the incremental energy of RAC as opposed to NAC, to identify what contribute to the difference out of four primary factors discussed in previous research. It was found that the EE of RAC is marginally different to that of NAC by +2.1 to −1.1%, and the variation was subject to the magnitude and direction of the four factors considered. The mix composition, primarily the binder composition, was found to have the highest contribution to the difference, significantly standing out from the direct energy difference between RCA and NA, difference of sourcing distance between RCA and NA and the difference of direct manufacturing energy between RAC and NAC.
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    Methodology for the integrated assessment on the use of recycled concrete aggregate replacing natural aggregate in structural concrete
    Wijayasundara, M ; Mendis, P ; Crawford, RH (Elsevier, 2017)
    Recycled concrete waste in the form of recycled concrete aggregate (RCA) is presently used mostly as a road base filler in Australia. However, instead of producing natural aggregate (NA) to manufacture natural aggregate concrete (NAC) to use in structural concrete, there is potential to use RCA to manufacture recycled aggregate concrete (RAC). While the material performance of RAC compared to NAC is analysed in the existing literature, it is not evident whether the use of RCA in structural concrete results in financial and environmental benefits. Previous literature analysing these aspects mostly focuses on a single area of investigation. This paper presents an integrated methodology for the assessment of the use of RCA replacing NA in structural concrete, considering technical, financial, environmental and social perspectives. Cost-benefit assessment (CBA) has been used to evaluate the internalised impacts as well as external costs concerning the use of both RAC and NAC. The scope of each discipline-focused assessment is presented demarcating the relevant scope for further study, and the specific tools and methodologies to be adopted are specified. Finally, amalgamating the different discipline-focused assessments, a unique approach for comparing a sustainable, alternative raw material for concrete, is presented in this paper.
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    Integrated assessment of the use of recycled concrete aggregate replacing natural aggregate in structural concrete
    Wijayasundara, M ; Mendis, P ; Crawford, RH (Elsevier, 2018)
    The use of recycled concrete aggregate (RCA) replacing natural aggregate (NA) to produce concrete named as recycled aggregate concrete (RAC) has gained increased importance in the last few decades. Despite many visible advantages associated with the initiative, RAC is not manufactured at commercial scale to replace natural aggregate concrete (NAC) used as structural concrete in Australia presently. To identify whether the production of RAC should be favoured against NAC, an integrated assessment combining multiple criteria is essential as the previous research findings provide mixed outcomes on financial viability, product performance and environmental performance. This paper uses an integrated assessment methodology employing cost-benefit analysis (CBA) which combines the financial, direct and indirect environmental, social outcomes associated with the initiative to evaluate its suitability. By combining several qualitative and quantitative studies published by the author/s, an integral result to compare the use of RCA replacing NA in structural applications is conducted in this study. Net present value (NPV) to society associated with a unit volume of RAC is evaluated as a representative indicator to compare RAC against NAC in this paper. The results state that a unit volume of RAC results in a positive NPV of 4.2–6.0% of the price of NAC for 30% replacement (and 16.3–22.6% for 100%), prior to being used in a building r. Simulation of application of the RAC to two case study buildings indicate that the average price of concrete used in the buildings is decreased by 4.1–6.1%. The results indicate that, if the external benefit associated with the production of RAC is internalised and passed on to the purchaser of the product, production of RAC in structural buildings result in a positive NPV and saving of building material costs to the contractor.
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    Net incremental indirect external benefit of manufacturing recycled aggregate concrete
    Wijayasundara, M ; Mendis, P ; Crawford, RH (Elsevier, 2018-08-01)
    Concrete waste (CW) either reaches landfill with mixed waste or crushed to produce crushed concrete (CC) used as a road-base product in Australia. The coarse portion of CC, referred to as recycled concrete aggregate (RCA) has the potential to be used as an aggregate in structural concrete replacing natural aggregate (NA). The environmental performance of RAC has been studied in comparison to NAC, in terms of direct environmental implications (DEI) concerning the processes in the production chain of these products. However, when replacement at industry level is considered, the implications go beyond the DEI, and affect a series of other products/processes within a system boundary, referred to as indirect environmental implications (IEI). This paper quantifies the key IEI associated with the use of RCA in structural concrete and evaluates the external costs and benefits associated with it using economic evaluation methods. The net benefit associated with the avoidance of landfill of CW, extraction of NA, and transportation of waste and by-products are the major externalities identified and quantified in this paper. Evaluation of these suggest that there is a significant net benefit ranging from 9% to 28% of the price of natural aggregate concrete (NAC) with the production of recycled aggregate concrete (RAC), for RCA replacement rates between 30% and 100%.
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    Designing Post COVID-19 Buildings: Approaches for Achieving Healthy Buildings
    Navaratnam, S ; Nguyen, K ; Selvaranjan, K ; Zhang, G ; Mendis, P ; Aye, L (MDPI AG, 2022-01-12)
    The COVID-19 pandemic forced the accessibility, social gathering, lifestyle, and working environment to be changed to reduce the infection. Coronavirus spreads between people in several different ways. Small liquid particles (aerosols, respiratory droplets) from an infected person are transmitted through air and surfaces that are in contact with humans. Reducing transmission through modified heating, ventilation, and air conditioning (HVAC) systems and building design are potential solutions. A comprehensive review of the engineering control preventive measures to mitigate COVID-19 spread, healthy building design, and material was carried out. The current state-of-the-art engineering control preventive measures presented include ultraviolet germicidal irradiation (UVGI), bipolar ionization, vertical gardening, and indoor plants. They have potential to improve the indoor air quality. In addition, this article presents building design with materials (e.g., copper alloys, anti-microbial paintings) and smart technologies (e.g., automation, voice control, and artificial intelligence-based facial recognition) to mitigate the infections of communicable diseases.