Browsing by Author "Navaratnam, S"

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item: Article-Full-text
Analyses of structural robustness of prefabricated modular buildings: A case study on mid-rise building configurationm
(MDPI, 2022) Munmulla, T; Navaratnam, S; Thamboo, J; Ponnampalam, T; Damruwan, H-GH; Tsavdaridis, KD; Zhang, G
The limited knowledge of the behaviour of modular buildings subjected to different loading scenarios and thereby lack of design guidelines hinder the growth of modular construction practices despite its widespread benefits. In order to understand the robustness of modular building systems, a case study was carried out using the numerical analysis method to evaluate the robustness of ten-storey braced frame modular buildings with different modular systems. Two types of modules with different span lengths were used in the assessments. Then, three different column removal scenarios involving (1) removal of a corner column, (2) an edge column, and (3) an interior column were employed to assess the robustness of modular building cases considered. The forces generated in the elements in close proximity to the removed column were verified to assess the robustness of each building case analysed. The results showed that the change in damping ratio from 1% to 5% has no significant influence on the robustness of the modular building cases considered, where the zero-damping leads to collapse. Corner column removal has not considerably affected the robustness of the braced modular building cases studied. The axial capacity ratio of columns is 0.8 in dynamic column removal in the building subjected to corner column removal, while in interior column removal capacity ratio reached up to 1.2, making it the most vulnerable failure scenario. Doubling the span of the modules (from 2.5 m to 5 m) has influenced the robustness of the buildings by increasing the axial forces of columns up to 30% in the interior column removal scenario. Thus, this study highlights that proper guidelines should be made available to assess the robustness of modular building systems to effectively design against progressive collapse.
item: Article-Full-text
Development of sustainable mortar using waste rice husk ash from rice mill plant: Physical and thermal properties
(Elsevier, 2021) Selvaranjan, Kajanan; Gamage, JCPH; De Silva, GIP; Navaratnam, S
The rice processing industry generates a significant amount of rice husk ash (RHA) waste, which is considered as cost-efficient and environmentally friendly pozzolanic material. This study used RHA as a replacement for filler material/fine aggregate in the mortar. The mechanical, thermal, and environmental performance of mortar comprising RHA waste as a replacement of river sand in different contents (0, 10, 20, 30 and 50% by weight of river sand) were investigated through experimental tests and environmental impact assessment. The RHAs were obtained from both controlled burnt (CBRHA) and opened burnt (OBRHA) processes and used to produce the mortar mixtures. Results show that OBRHA can be used as a partial replacement for river sand for up to 30% of weight to improve the thermal performance by reducing thermal conductivity up to 62% while keeping the adequate compressive strength. Further, the replacement of 30% weight of sand with OBRHA in conventional mortar production significantly reduces greenhouse gas emissions (i.e. 13% reduction per kg) and cost (4% reduction per kg).
item: Article-Full-text
Suitability of modular technology for house construction in sri lanka
(MDPI, 2023) Munmulla, T; Gamage, HDH; Navaratnam, S; Ponnampalam, T; Zhang, G; Jayasinghe, T
Prefabricated volumetric modular building construction is an emerging technology in many countries used to develop the construction industry through its value-added benefits. The adoption of these novel technologies in the Sri Lankan construction industry has been relatively slow compared with other developing countries, delaying the development of the construction industry and the attainment of the added benefits of these technologies. Therefore, this study aims to identify the suitability of modular construction for the Sri Lankan construction industry via a survey and case study. A questionnaire survey was developed and distributed to assess and identify the benefits of implementing the concepts and constraints in Sri Lanka. Then, the construction cost of a proposed single-story house delivered through conventional and modular practices was compared. The survey results showed that introducing a modular concept to the industry is suitable and would benefit the Sri Lankan construction industry. Further, survey participants believed that the economic benefits brought in by modular construction are significantly more important than environmental and social benefits when selecting modular construction. The case study on a single-story affordable modular house showed a 32% reduction in total construction costs and a 36% reduction in labour costs compared to conventional house construction. Further, costs for total modular construction and labour were 32% and 36% less than those of conventional construction costs and labour costs. Moreover, a 16% reduction in embodied energy was observed when compared with conventional construction. Therefore, the modular concept could be used to construct affordable houses and will be cost-effective with the correct choice of material.
item: Article-Full-text
Sustainable approaches to improve the resilience of modular buildings under wind loads
(Elsevier, 2023) Munmulla, T; Navaratnam, S; Gamage, H; Tushar, Q; Ponnampalam, T; Zhang, G; Jayasinghe, MTR
Prefabricated volumetric modular building (PVMB) technology is an emerging technology that can make the construction industry walk towards sustainability by reducing the emission of pollutants leading to various environmental impacts. However, the knowledge of the lateral behaviour of PVMBs is limited. This could lead to significant building failure in future, as the climate continues to change, it is expected that building performance will be affected. Thus, this research aims to study the resilience of PVMBs under changing wind loads and identify the most sustainable approach to improve resilience. A 25-storey case-study building was analysed with modifications added to increase its lateral stiffness. Three methods of increasing the resilience were used: (1) increasing the size of structural elements; (2) increasing the inter-component connection stiffness; and (3) introducing discrete diaphragms. The results showed that using chevron bracings of the same section size as Xbracings can maintain the same resilience against the wind while decreasing total bracing steel volume by 32%. Among the analysis cases, structures with concrete cores (CC) have the highest stiffness to withstand the increased wind loads. The building with CC at the centre can withstand a 100% higher serviceability wind speed (i.e. 74 ms􀀀 1) than building without modifications (i.e. 37 ms􀀀 1). At the same time, the building with CC on either side can withstand a 45% higher wind speed than building without modifications. Further considering the sustainability aspects, the environmental effects of global warming can be reduced by about 160% when fully modular buildings are constructed with recycled steel.
item: Article-Full-text
Thermal and environmental impact analysis of rice husk ash-based mortar as insulating wall plaster
(Elsevier, 2021) Selvaranjan, K; Navaratnam, S; Gamage, DCPH; Thamboo, J; Siddique, R; Zhang, J; Zhang, G
The energy used to maintain the thermal comfort of buildings significantly contributes to the GHG emissions and global warming. In this study, a sustainable and cost-effective rice husk ash (RHA)-based mortar for wall plastering has been developed to provide better thermal insulation, reduce the operational energy and enhance the thermal comfort. Consequently, RHA was partially replaced with the sand in the conventional mortar to produce the RHA-based plaster. Initially, compressive strengths and thermal conductivities of the selected mortar mixes were assessed. The results highlight that the RHA can be replaced up to 30% instead of sand in mortar to produce the thermally enhanced wall plaster. Further, two identical prototype model houses were constructed with RHA-based (i.e. 30% of RHA) and conventional plasters to evaluate their heat transfer, heat flux, and the characteristics of internal and external wall surface temperatures in open weather conditions. It was noted that the average peak heat flux reduction formed by the RHA-based plaster was 10%. The average daily heat transfer reduction across the wall with RHA-based plaster was about 26%. Results also show that RHA-based plaster can reduce the energy that required to maintain thermal comfort by about 9% than the conventional plaster. Moreover, the environmental impact analysis was also conducted to assess the sustainability performance of RHA-based mortars. The environmental impact assessment revealed that the RHA-based plaster has less environmental impact than the conventional mortar. Furthermore, the CO2 emission generated by the production of RHA-based mortar is about 14% less than the conventional plaster.