Anura Nanayakkara | University of Moratuwa Sri Lanka (original) (raw)
Papers by Anura Nanayakkara
Journal of Structural Fire Engineering
PurposeElevated temperature material properties are essential in predicting structural member'... more PurposeElevated temperature material properties are essential in predicting structural member's behavior in high-temperature exposures such as fire. Even though experimental methodologies are available to determine these properties, advanced equipment with high costs is required to perform those tests. Therefore, performing those experiments frequently is not feasible, and the development of numerical techniques is beneficial. A numerical technique is proposed in this study to determine the temperature-dependent thermal properties of the material using the fire test results based on the Artificial Neural Network (ANN)-based Finite Element (FE) model.Design/methodology/approachAn ANN-based FE model was developed in the Matlab program to determine the elevated temperature thermal diffusivity, thermal conductivity and the product of specific heat and density of a material. The temperature distribution obtained from fire tests is fed to the ANN-based FE model and material properties...
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Frontiers of Structural and Civil Engineering
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Structural Concrete
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Innovative Infrastructure Solutions, 2022
Emerging environmental problems are identified due to the improper sand extraction near the river... more Emerging environmental problems are identified due to the improper sand extraction near the riverbeds for the construction activities. This research was involved with completely replacing river sand by alternatives in masonry works. Manufactured sand and offshore sand were utilized as the substitutions for river sand and incorporated in mortars in the forms of manufactured sand alone and blending of both alternatives. Cement–sand and lime–cement–sand mortars were prepared to fabricate the masonry specimens and brick–mortar joints. The mechanical characteristics of masonry and brick–mortar joints were investigated using the available standards. The compressive and flexural strengths of masonry were greatly improved by the mortars included manufactured sand alone and the blended sand mortars. The diagonal tensile strength of masonry with the alternatives showed conflicting trends. Shear and adhesive strengths of brick–mortar joint were significantly advanced by the alternative mortars. Fine aggregate properties such as angularity, surface roughness and packing density were correlated with the masonry properties and some models were proposed to evaluate the rationale behind these effects.
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Journal of Structural Fire Engineering, 2021
Purpose In this study, the insulation fire ratings of lightweight foamed concrete, autoclaved aer... more Purpose In this study, the insulation fire ratings of lightweight foamed concrete, autoclaved aerated concrete and lightweight aggregate concrete were investigated using finite element modelling. Design/methodology/approach Lightweight aggregate concrete containing various aggregate types, i.e. expanded slag, pumice, expanded clay and expanded shale were studied under standard fire and hydro–carbon fire situations using validated finite element models. Results were used to derive empirical equations for determining the insulation fire ratings of lightweight concrete wall panels. Findings It was observed that autoclaved aerated concrete and foamed lightweight concrete have better insulation fire ratings compared with lightweight aggregate concrete. Depending on the insulation fire rating requirement of 15%–30% of material saving could be achieved when lightweight aggregate concrete wall panels are replaced with the autoclaved aerated or foamed concrete wall panels. Lightweight aggreg...
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2019 Moratuwa Engineering Research Conference (MERCon), 2019
This paper reports the feasibility of using bottom ash which is a waste product of coal-fired pow... more This paper reports the feasibility of using bottom ash which is a waste product of coal-fired power plants, for producing cellular lightweight concrete blocks. Experimental investigation was carried by varying the parameters; bottom ash to cement (BA/C) ratio, water to cement (W/C) ratio, the density of foam concrete mixes and particle size fraction of bottom ash. The method of moisture curing was used to produce bottom ash foam concrete blocks. The performance of the produced bottom ash foam concrete was evaluated by considering compressive strength, drying shrinkage, structure and distribution of pores, wetting expansion and water absorption. It was observed that with the increase of BA/C ratio, the compressive strength of the foam concrete blocks increased and reached the maximum value of 3.1 MPa with 1.2 BA/C ratio, followed a drastic strength reduction. Experimental results also showed very high values for drying shrinkage and water absorption of the foam concrete produced with bottom ash.
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Journal of Structural Fire Engineering, 2022
PurposeLight-Gauge Steel Frame (LSF) structures are popular in building construction due to their... more PurposeLight-Gauge Steel Frame (LSF) structures are popular in building construction due to their lightweight, easy erecting and constructability characteristics. However, due to steel lipped channel sections negative fire performance, cavity insulation materials are utilized in the LSF configuration to enhance its fire performance. The applicability of lightweight concrete filling as cavity insulation in LSF and its effect on the fire performance of LSF are investigated under realistic design fire exposure, and results are compared with standard fire exposure.Design/methodology/approachA Finite Element model (FEM) was developed to simulate the fire performance of Light Gauge Steel Frame (LSF) walls exposed to realistic design fires. The model was developed utilising Abaqus subroutine to incorporate temperature-dependent properties of the material based on the heating and cooling phases of the realistic design fire temperature. The developed model was validated with the available ex...
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2020 Moratuwa Engineering Research Conference (MERCon), 2020
Bottom ash, which is a byproduct of coal fired thermal power plants has given rise to major envir... more Bottom ash, which is a byproduct of coal fired thermal power plants has given rise to major environmental impacts due to its potential hazardous effects. Through this research, attempts were made to use bottom ash as a substitute for river sand in producing foam concrete blocks. This will further contribute to the reduction of excessive river sand mining. In this research main focus was given to develop lightweight concrete blocks incorporating bottom ash and foaming agent. Experimental investigations were carried out by varying bottom ash to cement ratio, water to cement ratio and particle sizes of bottom ash in order to identify the potential of applicability of bottom ash in producing foam concrete blocks. Furthermore, in this study, wet method was used to generate foam by using industrial foam generating machine. By evaluating a range of properties such as compressive strength, drying shrinkage, wetting expansion and water absorption, it was found that the optimum bottom ash to cement ratio for foam concrete is 0.75 which resulted in compressive strength of 3.8 MPa with dry density in the range of 700-850 kgm-3 which satisfies the requirements of lightweight category masonry blocks.
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This paper mainly discusses the deterioration of concrete due to temperature rise in concrete as ... more This paper mainly discusses the deterioration of concrete due to temperature rise in concrete as a result of heat of hydration of cement. When concrete is subjected to high temperature at early age, many physical and chemical changes of the hardened concrete can take place. Recently, severe cracking in some of the pile caps of bridge piers in southern highway project in Sri Lanka was reported. After extensive investigations, it was found that the main cause for cracking in those pile caps was due to an internal chemical reaction known as delayed ettringite formation (DEF). DEF is sometimes referred to as internal sulphate attack which is an internal swelling reaction of the concrete that occurs in the presence of water without any external ingress of sulphate. It is widely accepted that concrete subjected to high temperature at early age and exposed to moisture continuously or intermittently is likely to crack due to DEF. Experimental investigations also revealed that even when the ...
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According to ASTM 403C, initial setting time of concrete is measured based on penetration resista... more According to ASTM 403C, initial setting time of concrete is measured based on penetration resistance of mortar sieved from concrete and it is considered as the time taken to achieve a penetration resistance of 3.5MPa which is an arbitrary value. The main objective of this research is to find a test method to obtain a realistic initial setting time value in order to plan the placing of concrete to prevent formation of cold joints which can affect the performance of the structure. Mechanical properties (tensile strength and shear strength) at a purposely made cold joint was evaluated by testing concrete cubes cast in two layers with different time lags between placing of concrete in the two layers. Point of change of each strength parameter with respect to time lag was identified and corresponding time range was identified as the initial setting time range. Standard penetration resistance test was also carried out and with the use of penetration resistance vs. elapsed time graph, corr...
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European Journal of Environmental and Civil Engineering, 2021
The environment and ecological systems are suspected of serious drawbacks as a result of the over... more The environment and ecological systems are suspected of serious drawbacks as a result of the over-extraction of river sand for construction activities. An attempt was made in this research on completely replacing river sand in lime-cement masonry mortars with blended sands comprised of manufactured sand and offshore sand. The S and N types (as defined in the standards) were selected for producing masonry mortars with different sand contents. For each type, five mortars were prepared to contain river sand alone (reference mortar), manufactured sand alone, and three blended sands (replacing manufactured sand by offshore sand at 25%, 50%, and 75%). Because of the dominant roles of particle angularity, surface roughness, and gradation of the alternatives, the performance of mortars was evaluated and compared based on these sand characteristics. Furthermore, the level of statistical significance of the experiment results was analyzed from a single factor one-way ANOVA test. Outcomes of this research revealed that the blended sands and manufactured sand declined the fresh state performance of mortars than the river sand mortars. However, most of the stiffened and durability properties of alternative mortars were significantly advanced than the reference mortars.
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Construction and Building Materials, 2008
ABSTRACT A figure of 0.075% by weight of sand was arrived at as a safe limit for allowable Cl− io... more ABSTRACT A figure of 0.075% by weight of sand was arrived at as a safe limit for allowable Cl− ion content in offshore sand for OPC based reinforced concrete. A 2 m high sand column was fabricated for checking the effects of natural drainage and simulated rain on the chloride levels in offshore sand, and the action of even 80 mm of rain was found to reduce Cl− contents to below acceptable levels. The accelerated corrosion performance of grade 20 concrete (i.e. the most critical structural grade) with the allowable Cl− content in the sand was satisfactory and similar to a chloride free control mix; on the other hand, a mix with seawater saturated sand (0.3% Cl−) showed clear evidence of high corrosion.
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Buildings
This paper reviews the research advancements and design practices related to the structural web c... more This paper reviews the research advancements and design practices related to the structural web crippling response of lipped Cold-Formed (CF) carbon steel, stainless steel, and aluminium channels with web perforations. The web crippling response differs among each material based on the non-linear stress-strain characteristics and degree of strain hardening. Therefore, the reduction in the web crippling strength of web-perforated CF channel sections made of different materials may not be equivalent. The research activities surrounding the web crippling response of CF channels with and without web openings were reviewed initially. Despite the limited design provisions given in the international specifications for the web crippling design of lipped CF channels with web openings, web crippling studies conducted across the world have developed suitable design equations in the form of reduction factors. Past research studies have substantially captured the web crippling response of carbon...
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Engineering Fracture Mechanics, 2012
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European Journal of Environmental and Civil Engineering, 2021
The environment and ecological systems are suspected of serious drawbacks as a result of the over... more The environment and ecological systems are suspected of serious drawbacks as a result of the over-extraction of river sand for construction activities. An attempt was made in this research on completely replacing river sand in lime-cement masonry mortars with blended sands comprised of manufactured sand and offshore sand. The S and N types (as defined in the standards) were selected for producing masonry mortars with different sand contents. For each type, five mortars were prepared to contain river sand alone (reference mortar), manufactured sand alone, and three blended sands (replacing manufactured sand by offshore sand at 25%, 50%, and 75%). Because of the dominant roles of particle angularity, surface roughness, and gradation of the alternatives, the performance of mortars was evaluated and compared based on these sand characteristics. Furthermore, the level of statistical significance of the experiment results was analyzed from a single factor one-way ANOVA test. Outcomes of t...
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Journal of Structural Fire Engineering
PurposeElevated temperature material properties are essential in predicting structural member'... more PurposeElevated temperature material properties are essential in predicting structural member's behavior in high-temperature exposures such as fire. Even though experimental methodologies are available to determine these properties, advanced equipment with high costs is required to perform those tests. Therefore, performing those experiments frequently is not feasible, and the development of numerical techniques is beneficial. A numerical technique is proposed in this study to determine the temperature-dependent thermal properties of the material using the fire test results based on the Artificial Neural Network (ANN)-based Finite Element (FE) model.Design/methodology/approachAn ANN-based FE model was developed in the Matlab program to determine the elevated temperature thermal diffusivity, thermal conductivity and the product of specific heat and density of a material. The temperature distribution obtained from fire tests is fed to the ANN-based FE model and material properties...
Bookmarks Related papers MentionsView impact
Frontiers of Structural and Civil Engineering
Bookmarks Related papers MentionsView impact
Structural Concrete
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Innovative Infrastructure Solutions, 2022
Emerging environmental problems are identified due to the improper sand extraction near the river... more Emerging environmental problems are identified due to the improper sand extraction near the riverbeds for the construction activities. This research was involved with completely replacing river sand by alternatives in masonry works. Manufactured sand and offshore sand were utilized as the substitutions for river sand and incorporated in mortars in the forms of manufactured sand alone and blending of both alternatives. Cement–sand and lime–cement–sand mortars were prepared to fabricate the masonry specimens and brick–mortar joints. The mechanical characteristics of masonry and brick–mortar joints were investigated using the available standards. The compressive and flexural strengths of masonry were greatly improved by the mortars included manufactured sand alone and the blended sand mortars. The diagonal tensile strength of masonry with the alternatives showed conflicting trends. Shear and adhesive strengths of brick–mortar joint were significantly advanced by the alternative mortars. Fine aggregate properties such as angularity, surface roughness and packing density were correlated with the masonry properties and some models were proposed to evaluate the rationale behind these effects.
Bookmarks Related papers MentionsView impact
Journal of Structural Fire Engineering, 2021
Purpose In this study, the insulation fire ratings of lightweight foamed concrete, autoclaved aer... more Purpose In this study, the insulation fire ratings of lightweight foamed concrete, autoclaved aerated concrete and lightweight aggregate concrete were investigated using finite element modelling. Design/methodology/approach Lightweight aggregate concrete containing various aggregate types, i.e. expanded slag, pumice, expanded clay and expanded shale were studied under standard fire and hydro–carbon fire situations using validated finite element models. Results were used to derive empirical equations for determining the insulation fire ratings of lightweight concrete wall panels. Findings It was observed that autoclaved aerated concrete and foamed lightweight concrete have better insulation fire ratings compared with lightweight aggregate concrete. Depending on the insulation fire rating requirement of 15%–30% of material saving could be achieved when lightweight aggregate concrete wall panels are replaced with the autoclaved aerated or foamed concrete wall panels. Lightweight aggreg...
Bookmarks Related papers MentionsView impact
2019 Moratuwa Engineering Research Conference (MERCon), 2019
This paper reports the feasibility of using bottom ash which is a waste product of coal-fired pow... more This paper reports the feasibility of using bottom ash which is a waste product of coal-fired power plants, for producing cellular lightweight concrete blocks. Experimental investigation was carried by varying the parameters; bottom ash to cement (BA/C) ratio, water to cement (W/C) ratio, the density of foam concrete mixes and particle size fraction of bottom ash. The method of moisture curing was used to produce bottom ash foam concrete blocks. The performance of the produced bottom ash foam concrete was evaluated by considering compressive strength, drying shrinkage, structure and distribution of pores, wetting expansion and water absorption. It was observed that with the increase of BA/C ratio, the compressive strength of the foam concrete blocks increased and reached the maximum value of 3.1 MPa with 1.2 BA/C ratio, followed a drastic strength reduction. Experimental results also showed very high values for drying shrinkage and water absorption of the foam concrete produced with bottom ash.
Bookmarks Related papers MentionsView impact
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Journal of Structural Fire Engineering, 2022
PurposeLight-Gauge Steel Frame (LSF) structures are popular in building construction due to their... more PurposeLight-Gauge Steel Frame (LSF) structures are popular in building construction due to their lightweight, easy erecting and constructability characteristics. However, due to steel lipped channel sections negative fire performance, cavity insulation materials are utilized in the LSF configuration to enhance its fire performance. The applicability of lightweight concrete filling as cavity insulation in LSF and its effect on the fire performance of LSF are investigated under realistic design fire exposure, and results are compared with standard fire exposure.Design/methodology/approachA Finite Element model (FEM) was developed to simulate the fire performance of Light Gauge Steel Frame (LSF) walls exposed to realistic design fires. The model was developed utilising Abaqus subroutine to incorporate temperature-dependent properties of the material based on the heating and cooling phases of the realistic design fire temperature. The developed model was validated with the available ex...
Bookmarks Related papers MentionsView impact
2020 Moratuwa Engineering Research Conference (MERCon), 2020
Bottom ash, which is a byproduct of coal fired thermal power plants has given rise to major envir... more Bottom ash, which is a byproduct of coal fired thermal power plants has given rise to major environmental impacts due to its potential hazardous effects. Through this research, attempts were made to use bottom ash as a substitute for river sand in producing foam concrete blocks. This will further contribute to the reduction of excessive river sand mining. In this research main focus was given to develop lightweight concrete blocks incorporating bottom ash and foaming agent. Experimental investigations were carried out by varying bottom ash to cement ratio, water to cement ratio and particle sizes of bottom ash in order to identify the potential of applicability of bottom ash in producing foam concrete blocks. Furthermore, in this study, wet method was used to generate foam by using industrial foam generating machine. By evaluating a range of properties such as compressive strength, drying shrinkage, wetting expansion and water absorption, it was found that the optimum bottom ash to cement ratio for foam concrete is 0.75 which resulted in compressive strength of 3.8 MPa with dry density in the range of 700-850 kgm-3 which satisfies the requirements of lightweight category masonry blocks.
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This paper mainly discusses the deterioration of concrete due to temperature rise in concrete as ... more This paper mainly discusses the deterioration of concrete due to temperature rise in concrete as a result of heat of hydration of cement. When concrete is subjected to high temperature at early age, many physical and chemical changes of the hardened concrete can take place. Recently, severe cracking in some of the pile caps of bridge piers in southern highway project in Sri Lanka was reported. After extensive investigations, it was found that the main cause for cracking in those pile caps was due to an internal chemical reaction known as delayed ettringite formation (DEF). DEF is sometimes referred to as internal sulphate attack which is an internal swelling reaction of the concrete that occurs in the presence of water without any external ingress of sulphate. It is widely accepted that concrete subjected to high temperature at early age and exposed to moisture continuously or intermittently is likely to crack due to DEF. Experimental investigations also revealed that even when the ...
Bookmarks Related papers MentionsView impact
According to ASTM 403C, initial setting time of concrete is measured based on penetration resista... more According to ASTM 403C, initial setting time of concrete is measured based on penetration resistance of mortar sieved from concrete and it is considered as the time taken to achieve a penetration resistance of 3.5MPa which is an arbitrary value. The main objective of this research is to find a test method to obtain a realistic initial setting time value in order to plan the placing of concrete to prevent formation of cold joints which can affect the performance of the structure. Mechanical properties (tensile strength and shear strength) at a purposely made cold joint was evaluated by testing concrete cubes cast in two layers with different time lags between placing of concrete in the two layers. Point of change of each strength parameter with respect to time lag was identified and corresponding time range was identified as the initial setting time range. Standard penetration resistance test was also carried out and with the use of penetration resistance vs. elapsed time graph, corr...
Bookmarks Related papers MentionsView impact
European Journal of Environmental and Civil Engineering, 2021
The environment and ecological systems are suspected of serious drawbacks as a result of the over... more The environment and ecological systems are suspected of serious drawbacks as a result of the over-extraction of river sand for construction activities. An attempt was made in this research on completely replacing river sand in lime-cement masonry mortars with blended sands comprised of manufactured sand and offshore sand. The S and N types (as defined in the standards) were selected for producing masonry mortars with different sand contents. For each type, five mortars were prepared to contain river sand alone (reference mortar), manufactured sand alone, and three blended sands (replacing manufactured sand by offshore sand at 25%, 50%, and 75%). Because of the dominant roles of particle angularity, surface roughness, and gradation of the alternatives, the performance of mortars was evaluated and compared based on these sand characteristics. Furthermore, the level of statistical significance of the experiment results was analyzed from a single factor one-way ANOVA test. Outcomes of this research revealed that the blended sands and manufactured sand declined the fresh state performance of mortars than the river sand mortars. However, most of the stiffened and durability properties of alternative mortars were significantly advanced than the reference mortars.
Bookmarks Related papers MentionsView impact
Construction and Building Materials, 2008
ABSTRACT A figure of 0.075% by weight of sand was arrived at as a safe limit for allowable Cl− io... more ABSTRACT A figure of 0.075% by weight of sand was arrived at as a safe limit for allowable Cl− ion content in offshore sand for OPC based reinforced concrete. A 2 m high sand column was fabricated for checking the effects of natural drainage and simulated rain on the chloride levels in offshore sand, and the action of even 80 mm of rain was found to reduce Cl− contents to below acceptable levels. The accelerated corrosion performance of grade 20 concrete (i.e. the most critical structural grade) with the allowable Cl− content in the sand was satisfactory and similar to a chloride free control mix; on the other hand, a mix with seawater saturated sand (0.3% Cl−) showed clear evidence of high corrosion.
Bookmarks Related papers MentionsView impact
Buildings
This paper reviews the research advancements and design practices related to the structural web c... more This paper reviews the research advancements and design practices related to the structural web crippling response of lipped Cold-Formed (CF) carbon steel, stainless steel, and aluminium channels with web perforations. The web crippling response differs among each material based on the non-linear stress-strain characteristics and degree of strain hardening. Therefore, the reduction in the web crippling strength of web-perforated CF channel sections made of different materials may not be equivalent. The research activities surrounding the web crippling response of CF channels with and without web openings were reviewed initially. Despite the limited design provisions given in the international specifications for the web crippling design of lipped CF channels with web openings, web crippling studies conducted across the world have developed suitable design equations in the form of reduction factors. Past research studies have substantially captured the web crippling response of carbon...
Bookmarks Related papers MentionsView impact
Engineering Fracture Mechanics, 2012
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European Journal of Environmental and Civil Engineering, 2021
The environment and ecological systems are suspected of serious drawbacks as a result of the over... more The environment and ecological systems are suspected of serious drawbacks as a result of the over-extraction of river sand for construction activities. An attempt was made in this research on completely replacing river sand in lime-cement masonry mortars with blended sands comprised of manufactured sand and offshore sand. The S and N types (as defined in the standards) were selected for producing masonry mortars with different sand contents. For each type, five mortars were prepared to contain river sand alone (reference mortar), manufactured sand alone, and three blended sands (replacing manufactured sand by offshore sand at 25%, 50%, and 75%). Because of the dominant roles of particle angularity, surface roughness, and gradation of the alternatives, the performance of mortars was evaluated and compared based on these sand characteristics. Furthermore, the level of statistical significance of the experiment results was analyzed from a single factor one-way ANOVA test. Outcomes of t...
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