Browsing by Author "Mahendran, M"

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item: Conference-Full-text
Comparative analysis of vertical metal zonation in Ginigalpelessa and Indikolapelessa serpentinite complex
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Mahendran, M; Maduranga, U.K.D.; Amarasinghe, A.A.Y.D.T.; Abeysinghe, A.M.K.B.; Ratnayake, N.P.; Premasiri, H.M.R.; Dushyantha, N.P.; Batapola, N.M.; Dilshara, R.M.P.; Iresha, H.; Elakneswaran, Y.; Dassanayake, A.; Jayawardena, C.
Serpentinite deposits in Ginigalpelessa and Indikolapelessa Sri Lanka, are known to exhibit a high supergene enrichment of Ni, Cr, and Co in the regolith due to the prolonged weathering of the underlying serpentinite bedrock. However, no detailed studies have been conducted to determine the vertical zonation of these critical metals in these deposits. The vertical metal distribution of a deposit is significant to delineate its vertical metal enrichment patterns and mobilization which may lead to the identification of efficient exploration and extraction methods. Therefore, this study assessed the vertical zonation of Ni, Cr, and Co in both Ginigalpelessa and Indikolapelessa serpentinite deposits. Twenty-four soil (n=12) and weathered rock (n=12) samples from 4 soil horizons (O, A, B, C) in soil profile were collected and analyzed for Ni, Co, Cr, and Cu by ICP-MS. Our findings revealed high metal concentrations in the soil or highly weathered rock samples over the partially weathered rock samples. The Ginigalpelessa deposit demonstrated4 a higher concentration of Ni, Co, Cr, and Cu compared to the Indikolapelessa deposit. It observed that the concentrations of Ni, Co, Cr and Cu in the topsoil were lower compared to deeper horizons (A, B, and C) in some locations. This may have occurred due to the bioavailability of some metals like Ni, which accumulates in the plants and reduce the concentration in the soil. Conversely, the low bioavailability of Cr compared to the other metals have resulted high Cr concentrations in the surface horizon. In addition, previous studies found that Cr is immobile, whereas Ni and Co are scarcely mobile under the moderate acidic conditions in the serpentine soil. During the weathering process, the slightly acidic rainwater leaches these Ni-like metals from the O and A horizons, resulting their enrichment in the B horizon. However, further studies are necessary to identify the suitable leaching or extraction method to recover these metals from serpentine soil. Therefore, this research contributes to a deeper understanding of vertical metal zonation in serpentinite deposits to facilitate more efficient and sustainable exploration of valuable metals like Ni in serpentinite deposits.
item: Thesis-Abstract
Diagnosing productivity proplems and identifying priorities
Mahendran, M; Jayawardane, AKW
This research project was done to diagnose productivity problems and identify priorities: and to determine the type of actions the Practitioners are willing to take to improve productivity. Methodology adopted to achieve the objectives were literature review and structured questionnaire survey. Questionnaire was developed to obtain from contractor and consultant the Company Characteristics. Areas for productivity improvement and the type of actions the organization would be willing to take. Contractors indicate that certain functions including procurement practices. cost control. scheduling and management integration need much improvement. Whereas the consultants indicate that they are concerned about design standards. design practices. drafting and specifications. From the research it was found that funding by the government appears to be necessary to support construction productivity programmes. It is recommended that designers awareness of materials and equipment issues could improve construction productivity. Also it is recommended surveys to be conducted every 3-4 years to observe and identify new trends in the industry and to direct research in the appropriate direction.
item: Conference-Full-text
Fatigue capacity of cold-formed steel roof battens under cyclic wind uplift loads
(2015-12-29) Kathekeyan, M; Mahendran, M; , Steel roofing systems, Thin steel roof battens, Wind action, Pull-through failures, Fatigue, Miner’s rule
Abstract: Steel roofs made of thin cold-formed steel roof claddings and battens are widely used in low-rise residential and industrial buildings all around the world. However, they suffer from premature localised pullthrough failures in the batten to rafter connections during high wind events. A recent study proposed a suitable design equation for the pull-through failures of thin steel roof battens. However, it was limited to static wind uplift loading. In contrast, most cyclone/storm events produce cyclic wind uplift forces on roofs for a significantly long period, thus causing premature fatigue pull-through failures at lower loads. Therefore, a series of constant amplitude cyclic load tests was conducted on small and full scale roof panels made of a commonly used industrial roof batten to develop their S-N curves. A series of multi-level cyclic tests, including the recently introduced low-high-low (LHL) fatigue loading test, was also undertaken to simulate a design cyclone. Using the S-N curves, the static pullthrough design capacity equation was modified to include the effects of fatigue. Applicability of Miner’s rule was evaluated in order to predict the fatigue damage caused by multi-level cyclic tests such as the LHL test, and suitable modifications were made. The combined use of the modified Miner’s law and the S-N curve of roof battens will allow a conservative estimation of the fatigue design capacity of roof battens without conducting the LHL tests simulating a design cyclone. This paper presents the details of this study, and the results.
item: Conference-Abstract
Numerical investigation of split mullions subject to negative wind action
(2019) Sivaprakasam, T; Kesawan, S; Mahendran, M
In modern facade construction, unitized aluminium framed and glazed facades have gained increasing popularity. In these unitized systems, vertical load bearing member is a split mullion (or mullion couple) made of thin-walled male and female mullions of adjacent panels, thus facilitating pre-fabrication and site assembly. The cross-sectional shape of these mullions are complex, and their shear centre generally lies outside the section. During negative wind action (suction), the male and female mullions would rotate to lean on each other at their unrestrained compression flange, by giving lateral supports to each other, due to eccentricity between the load and their shear centre. Conducting full-scale tests to understand such complex behaviour is expensive and time consuming, thus numerical simulations are preferred in such applications. In addition, finite element (FE) models developed in the previous studies were unable to simulate the real behaviour of mullion couples. Therefore, advanced numerical models were developed in order to investigate the structural behaviour and capacity of mullion couples subject to negative wind action. Full and simplified FE models of three different mullion couples, comprising captive and structural glazing mullions, were developed and analysed. In the full model, mullion couple, glass panes and gaskets/silicone sealants were modelled, whereas, only the mullion couple was modelled in the simplified model. In addition, FE analyses were performed on individual mullion sections, and their capacity predictions were compared with the respective mullion couple analysis predictions. The results from FE analyses were then compared with the moment capacities predicted using the current design approach. Based on the comparisons, suitable recommendations are given for the design of mullion couples subject to negative wind action. Overall, this study has improved the knowledge and understanding of the structural behavior and capacity of mullion couples used in facades.