Browsing by Author "Gamage, JCPH"

Now showing 1 - 20 of 77

item: Conference-Full-text
ACI guidelines to assess the performance of CFRP-strengthened concrete beams with transverse end U wraps
(2016-01-06) Ariyachandra, MREF; Gamage, JCPH
In this comprehensive study, firstly, the theoretical model described in ACI 440 committee report to calculate the area of transverse U wraps provided for anchored CFRP-strengthened concrete beams was examined. Then, an experimental study was carried out with a total of 10 small-scale test specimens and test parameters were set to inspect the validity of the limitations given in the above theoretical model. Theoretical calculations were performed in accordance with ACI guidelines for the above test specimens as well as for the previous research studies. Finally, the constraints of applicability of the theoretical model given in ACI 440 committee report was discussed presenting new recommendations for different scenarios.
item: Conference-Abstract
Alternative bonding techniques to delay end debonding of CFRP strengthened reinforced concrete beams
Premarathne, HRD; Gamage, JCPH
The use of Carbon Fibre Reinforced Polymer (CFRP) as external reinforcement for concrete structures is growing rapidly. This is due to many advantages offered by these materials compared to conventional steel reinforcements such as high strength to weight ratio, good fatigue properties, noncorroding characteristics, high degree of chemical inertness, controllable thermal expansion, damping characteristics and simplicity of application. Rehabilitation and strengthening of existing concrete structures can be done up to a significant level with correctly applied CFRP sheets. However CFRP strengthening systems subject to end de-bonding failure before reaching its full capacity. This study was focused on investigation of alternative bonding techniques to enhance strength gain by delaying premature failure of composite laminate. A total of six specimens were tested to determine the flexural capacity using three point bending test. The specimens were prepared with three different CFRP sheet arrangements. This paper presents the test program, results and conclusions.
item: Conference-Full-text
Alternatives to delay premature failure of CFRP strengthened reinforced concrete members
(2013-11-12) Srisangeerthanan, S; Prashanth, M; Amaradasa, PNS; Gamage, JCPH
This Study was focused on identifying and proposing alternatives such that premature debonding failure of CFRP strengthened reinforced concrete members in flexure is delayed. Two of our proposed alternatives were investigated in relation to three control beams of two standard configurations. A unidirectional CFRP fabric was applied onto the concrete surface using two part epoxy resin as a binder inclusive of an inexpensive polymer mesh of polyester in specific arrangements. Three point bending tests were conducted. This study shows that the polymer mesh of polyester laid in the bond line has effectively delayed premature failure of composites. A range of 60% to 80% strength gains with respect to control beams was noted. Failure was observed with the formation of a mid-span flexure crack causing mid span debonding and subsequently debonding at the ends.
item: Article-Full-text
An analytical approach to predict cohesion and interfacial failures of CFRP/steel composites under prolonged exposure to aqueous solutions
(Elsevier, 2022) Perera, UND; Arachchi, KADYT. K; Gamage, JCPH
The long-term performance of Carbon Fibre Reinforced Polymer (CFRP) strengthened steel joint under prolonged exposure to moisture conditions is imperative in the applications of structures exposed to groundwater or seawater. Analytical models to determine the bond characteristics of CFRP/steel composites subjected to prolonged exposure in aqueous solutions are yet to be explored. This paper explores the cohesive and interfacial failure parameters of such CFRP/Steel composites theoretically. Thirty double-strap joints and twenty adhesive coupons were tested to determine the residual strength after exposure to seawater and distilled water for 6 and 12 months. An analytical model was developed to determine the degradation of adhesive material, bond and the interfaces of composite exposed to seawater and distilled water. The developed model is in good agreement with test results and capable of predicting initial bond degradation rate and stabilized degradation under-considered exposure conditions. Furthermore, the model could predict the contribution from the interfaces, bond line, and adhesive component on the degradation of composite in service.
item: Conference-Abstract
Behaviour of CFRP strengthened concrete slab at elevated temperature
(2016-05-11) Ranasinghe, RATM; Jinadasa, DVLR; Srilal, HPS; Gamage, JCPH
The use of Carbon Fiber Reinforced Polymers (CFRP) for concrete structures is becoming worldwide trend as an alternative to the use of conventional materials. Although there is an enormous structural potential to use the CFRP strengthened concrete in high rise building projects and industrial structures, majority of applications are limited only in bridges. The main reason is due to the lack of information related with the fire resistance of strengthened members. However, it is the prime importance to establish the adequacy of fire endurance and the structural integrity of the members prior to further implementing CFRP composite materials in buildings. Studies are carried out regarding the behavior of insulated and non-insulated CFRP/concrete members exposed to high temperature. Finite element analysis was used for the heat transfer analysis and simulations are done with the aid of commercially available software (ANSYS). This paper presents the thermal behavior of CFRP/concrete subjected to the transient heat condition and analysis on the bond performance under standard fire condition.
item: Conference-Full-text
Behaviour of Concrete Produced with Cement and Rice Husk Ash
(2016-05-04) Abdullah, MAA; Gamage, JCPH
Disposal of rice husk and its ash has been identified as a major problem in areas where rice production is abundance. Cement is an expensive material which plays a major role in the construction industry. This study shows the utilization of Rice Husk Ash (RHA) in concrete by conducting the laboratory experiments. Replacement of cement with RHA enhances both compressive and tensile properties of concrete. For this study, RHA was obtained from Bio-Energy power plant located in Ampara, Sri Lanka. As received RHA was sieved in order to prepare two types of samples with different particle sizes. Enhanced performances of Ordinary Portland Cement (OPC) can be achieved with 10% replacement of OPC by RHA regardless of particle sizes. Moreover, the adverse environmental impacts associated with RHA can also be reduced by utilizing the RHA in cementitious systems.
item: Conference-Full-text
Behaviour of Concrete Produced with Cement and Rice Husk Ash
(2016-01-05) Abdullah, MA; Gamage, JCPH
Disposal of rice husk and its ash has been identified as a major problem in areas where rice production is abundance. Cement is an expensive material which plays a major role in the construction industry. This study shows the utilization of Rice Husk Ash (RHA) in concrete by conducting the laboratory experiments. Replacement of cement with RHA enhances both compressive and tensile properties of concrete. For this study, RHA was obtained from Bio-Energy power plant located in Ampara, Sri Lanka. As received RHA was sieved in order to prepare two types of samples with different particle sizes. Enhanced performances of Ordinary Portland Cement (OPC) can be achieved with 10% replacement of OPC by RHA regardless of particle sizes. Moreover, the adverse environmental impacts associated with RHA can also be reduced by utilizing the RHA in cementitious systems
item: Article-Full-text
Bond characteristics of CFRP strengthened concrete members bonded using Modified Engineered Cementitious Composite
(Elsevier, 2021) Widanage, C; Gamage, JCPH; De Silva, GIP
This study focuses on the development of an insulating cementitious adhesive for bonding Carbon Fibre Reinforced Polymer (CFRP) fabrics to a concrete surface. The epoxy adhesive which is the generally used adhesive for CFRP shows a low thermal performance. As a potential solution, Engineered Cementitious Composite (ECC) mortar was modified as a cementitious adhesive with improved thermal insulation. The ECC adhesive was developed using locally available class F fly ash, silica sand and Polyethylene terephthalate (PET) fibres other than the generally used cement and water (PET-ECC). The selected mix proportion for PET-ECC achieved a low thermal conductivity of 0.145–0.180 W/mK which limited the heat transfer through the adhesive layer. The effective bond length of the developed PET-ECC adhesive was 125 mm and the corresponding bond strength was 224.9 MPa. The respective bond strength was further enhanced up to 570.28 MPa by sticking river sand on top of CFRP fabric using epoxy adhesive before bonding it to the concrete surface using the PET-ECC adhesive. The use of PET-ECC as the bonding agent to strengthen compression members with CFRP confinement yielded an average strength enhancement of 34%.
item: Article-Full-text
Bond characteristics of CFRP-strengthened concrete members subjected to cyclic temperature and mechanical stress at low humidity
(Elsevier, 2017) Gamage, JCPH; Al-Mahaidi, R; Wong, B; Ariyachandra, MREF
A total of fifty two CFRP strengthened concrete specimens were tested. In preliminary investigation, ten specimens were tested at ambient conditions with varying bond length. This indicated the effective bond length is in the range between 100 mm and 150 mm. The bond length of 150 mm was considered and fourty two specimens were prepared for detailed investigation. Thirty of them were conditioned under a range (0% - 50%) of sustained loading. All specimens were subjected to the temperature cycles of 20oC–50oC and constant relative humidity (30%) during conditioning. These specimens were tested using the singlelap shear test method at ambient conditions after 1800 hrs and 2250 hrs exposure for accelerated aging. The conditioned specimens showed the maximum strength reduction of 24%. The test results indicate that the concrete/epoxy interface as the weakest part of the composite in service life. Reduction in peak bond stress was noted from conditioned specimens with exposed level of sustained loading.
item: Conference-Full-text
Bond performance of CFRP strengthened concrete subjected to fire
(2011-12) Ranasinghe, RATM; Jinadasa, DVLR; Srilal, HPS; Gamage, JCPH; Ratnayake, N
CFRP (Carbon Fibre Reinforce Polymer) strengthening system has recently emerged as a practical alternative for the flexural strengthening of reinforced concrete structures because of its efficiency in terms of structural performances, costs, labour and time savings. While CFRP is widely used in bridge construction, it can also be taken advantage of for strengthening concrete members such as beams, columns and slabs. Even though structural engineers are interested in using CFRP for the strengthening work of concrete members in buildings, always hesitation occurs due to lack of knowledge of its fire performance. Therefore it is essential to assess and develop the needed information on fire resistance of CFRP strengthened concrete structural members. The epoxy adhesive used to create the bond is known to be very sensitive totemperature and its mechanical properties deteriorate rapidly with exposure toelevated temperature. The CFRP sheet or plate itself cannot provide sufficient insulation to the composite system. Therefore, application of a suitable insulation onto the CFRP sheet is important, especially in the application to buildings.In this study the behaviour of insulated CFRP/concrete members subjected to standard fire condition is explored. A finite element model, developed by using commercially available software ANSYS was used to simulate the thermal behaviour of the insulated composite structure.
item: Conference-Abstract
Bond performance of CFRP strengthened concrete subjected to fire
(2016-05-11) Rariasinghe, RATM; Jinadasa, DVLR; Srilal, HPS; Gamage, JCPH
CFRP (Carbon Fiber Reinforce Polymer) strengthening system has recently emerged us a practical alternative for the flexural strengthening of reinforced concrete structures because of its efficiency in terms of structural performances, costs, labor and time savings. While CFRP is widely used in bridge construction, it can also be taken advantage of for strengthening concrete members such as beams, columns and slabs. Even though structural engineers are interested in using CFRP for the strengthening work of concrete members in buildings, always hesitation occurs due to lack of knowledge of its fire performance. Therefore it is essential to assess and develop the needed information on fire resistance of CFRP strengthened concrete structural members. The epoxy adhesive used to create the bond is known to be very sensitive to temperature and its mechanical properties deteriorate rapidly with exposure to elevated temperature. The CFRP sheet or plate itself cannot provide sufficient insulation to the composite system. Therefore, application of a suitable insulationonto the CFRP sheet is important, especially in the application to buildings.ln this study the behaviour of insulated CFRP/concrete members subjected to standard fire condition is explored. A finite element model, developed by using commercially available software ANSYS was used to simulate the thermal behaviour of the insulated composite structure.
item: Conference-Abstract
Bond performance of CFRP strengthened steel members subjected to axial compression
Abeygunasekera, S; Gamage, JCPH; Fawzia, S
This paper focuses on the use of externally bonded Carbon Fiber Reinforced Polymer (CFRP) materials to strengthen steel plates subjected to compression. A fully slender steel section was selected in this test programme. CFRP strengthened steel plates and non strengthened plates were tested to fail under compressive load. The middle part of the strut was strengthened using CFRP sheet. The length of the strengthened zone was varied. Eight specimens were tested in this test programme. The test results showed a significant strength gain of 47% and delaying of lateral torsional buckling failure mode of strengthened members. This study confirms that there is great potential to increase the short term performance of CFRP strengthened steel structure under axial compression.
item: Conference-Abstract
Bond performance of CFRP/steel composites: state of the art review
Perera, UND; Gamage, JCPH
Over the past decade, CFRP (Carbon Fibre Reinforced Polymer) has been established as an excellent strengthening material to use in the metallic structures. Performance of CFRP strengthened steel members is directly dependent on the quality and the integrity of the adhesive bond. However, the insufficient knowledge on the bond behaviour of the CFRP/steel bonded joints is the major drawback in the lacking of real world applications of this system. Bonding procedure, including the surface preparation, different loading conditions and environmental conditions experienced can critically affect the bond behaviour and its performance. Studies have shown that dynamic loadings (fatigue/impact) can contribute to the strength and stiffness reduction of the bond while aggravating the results in severe exposed conditions. Also, these structures are frequently exposed to environmental conditions such as temperature variations, humidity conditions, UV radiation and marine environment. The consequence is severe when these exposure conditions are combined. This paper presents a state of the art review on bond performance of CFRP strengthened steel members for different load effects.
item: Conference-Full-text
Bond-slip models of cfrp/steel double strap joints subjected to long term exposure of moisture and elevated temperature
(IEEE, 2020-07) Perera, UND; Chandrathilake, ERK; Gamage, JCPH; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
Strengthening of deteriorated steel elements using Carbon Fiber Reinforced Polymer (CFRP) materials is widely gaining appeal. Since the majority of applications can be seen in outdoor structures, the evaluation of long-term behaviour under various environmental conditions is an important aspect. In the present study, the bond performance of CFRP strengthened steel double strap joints immersed in distilled water at ambient (28 oC) and elevated (40 oC) temperatures for six months was examined. A total of twelve specimens were tested including four control specimens and eight number of conditioned specimens. A numerical model was also developed. The model results are in good agreement with experimental results. The bond shear stress – local slip curves were then developed for each environmental condition using model predicted strain readings. The bond-slip models showed a bond shear strength degradation of about 24 % at 28 oC and 30 % at 40 oC within the exposure duration of six months.
item: Article-Full-text
Combined effects of Carbon Fiber Reinforced Polymer flexural reinforcements and post installed shear dowels on the performance of flat slabs
(Elsevier, 2020) Silva, MAL; Gamage, JCPH
The sudden punching shear failure of flat slabs is a critical issue. The combined effects of externally strengthened Carbon Fiber Reinforced Polymer (CFRP) flexural reinforcements and post-installed CFRP shear reinforcements which explain the real behavior in the strengthening phase of a shear deficient slab, on the punching shear performance are not fully explained. In this study, the flat slab panels of 1200 mm × 1200 mm × 100 mm were retrofitted with seven alternative bonding arrangements of CFRP to investigate the combined effects of shear dowels and flexural reinforcements. A transient load was applied using a stub column, size 100 mm × 100 mm located at the center of the slab. The non-strengthened specimens failed in punching shear. The strengthened specimens showed a maximum punching shear capacity enhancement of 120%. A numerical model was also developed to identify the load transfer behavior of post-installed CFRP shear dowels. Further, the effects from the end anchorage of external CFRP and the refilling material at drilled locations to install CFRP shear strengthening scheme were also determined.
item: Article-Full-text
Comparative durability study of CFRP strengthened tubular steel members under cold weather
(Springer Science+Business Media, 2016) Kabir, MH; Fawzia, S; Chan, THT; Gamage, JCPH
In strengthening systems, the carbon fibre reinforced polymer (CFRP) materials typically have excellent resistance against environmental conditions; however, the performance of adhesives between CFRP and steel is generally affected by various environmental conditions such as marine environment, cold and hot weather. This paper presents the comparative durability study of CFRP strengthened tubular steel structures by using two different adhesives such as MBrace saturant and Araldite K630 under four-point bending. The program consisted of testing twelve CFRP strengthened specimens having treated with epoxy based adhesion promoter, untreated surface and one unstrengthened specimen and conditioned under cold weather for 3 and 6 months to determine the environmental durability. The beams were then loaded to failure in quasi-static manner under four-point bending. The structural responses of CFRP strengthened tubular steel beams were compared in terms of failure load, stiffness and modes of failure. The research findings show that the cold weather immersion had adversely affected the durability of CFRP strengthened steel members. Design factor is also proposed to address the short-terms durability performance under cold weather.
item: Conference-Abstract
Composite effects of pozzolans in producing high strength recycled aggregate concrete
(Department of Civil Engineering, University of Moratuwa, 2021-11) Fernando, AM; Gamage, JCPH; Hettiarachchi, P
Over the years, the unceasing growth and development in the construction industry has resulted in both positives and negatives. The extensive use and disposal of many of the materials used in construction have resulted in the depletion of natural resources, together with piling up of large amounts of construction and demolition waste in landfills, causing adverse effects on the environment, the economy as well as society. The most extensively consumed material in the construction industry can be identified as concrete. Procurement and transportation of raw materials for cement and aggregates which are the two major constituents used in concrete production add significant disturbances to the ecological system. Thousands of research studies have shown the feasibility of using recycled aggregates to produce both normal and high strength concrete with comparable properties to conventional concrete. However, it requires a more allinclusive approach in producing an environmentally friendly solution. This paper discusses the procedure followed in producing cost effective and economical high strength concrete through the composite use of pozzolans namely fly ash, silica fume and rice husk ash (RHA), in both stages of aggregate treatment and concrete production. Results from aggregate testing showed a 26%and 59% reduction in aggregate water absorption and porosity, respectively. Further, enhancements in terms of aggregate specific gravity and crushing value were obtained. Concrete which contained RHA in both stages, attained a compressive strength of 55.4 MPa, which was even higher than the control mix containing natural aggregates. The same mix of concrete showed a 12% increase in its surface resistivity. This indicates the possibility of achieving high strengths, even with the use of RA derived from parent concretes of lower grades, and not many studies have focussed on this aspect of high strength recycled aggregate concrete production (HS-RAC).
item: Article-Abstract
Design of fibre reinforced polymer (FRP) strengthened beam for flexure
(2016-05-11) Gamage, JCPH
Nowadays, upgrading civil engineering structures is a very important issue, particularly for concrete bridges and buildings. For concrete bridges, increase in traffic load and deterioration caused by environmental factors are the two main reasons for a decrease in safety. FRP strengthening technique is widely gaining appeal in civil engineering infrastructures due to its superior properties and ease of construction and strengthening. However, the application of this technique is very limited in Sri Lanka. This is mainly due to lack of knowledge about FRP applications, selection of materials and also design procedures. The paper presents the background and detailed design procedures for FRP strengthened beam subjected to flexure.
item: Conference-Abstract
Development of a novel waste based insulated plaster with water proofing ability for roof slabs
(Department of Civil Engineering, 2023-09-27) Weerakkody, DD; Gamage, JCPH; Chandrathilaka, ERK; Selvaranjan, K; Mallikarachchi, C; Hettiarachchi, P; Herath, S; Fernando, L
The cement industry, notorious for its significant contribution to global greenhouse gas emissions, has drawn increasing attention in recent years due to its environmental impact. As we strive to combat climate change, one crucial area of focus is improving the thermal performance of buildings, which not only reduces energy consumption but also enhances thermal comfort for occupants. Among the various components of a building's thermal envelope, roof slabs stand out as key contributors to heat transfer, accounting for a substantial 50-60% of overall heat exchange. Addressing this thermal challenge necessitates innovative solutions, and one such solution that has gained attention is the use of Rice Husk Ash (RHA) as a sustainable material to augment thermal insulation in roof slabs. This approach aligns with the broader goal of sustainable construction practices and the reduction of greenhouse gas emissions by employing controlled waste disposal techniques that transform waste materials into timely-needed sustainable building materials. The core concept behind this novel approach involves the manipulation of the material's microstructure. To achieve low thermal conductivity, the RHA is employed to induce a pore structure within the material. This pore structure acts as a barrier to heat transfer, significantly enhancing the insulation properties of the roof slabs. Simultaneously, the gaps and voids within the microstructure of the material are filled with non-conductive Waste Brick Powder (WBP). This dual-purpose protection not only improves the thermal performance of the roof but also contributes to enhanced waterproofing abilities. The benefits of this innovative product are impressive, particularly when compared to existing alternatives available in the market. In a comparative analysis, this new material demonstrated a remarkable 69.5% reduction in thermal conductivity, making it an effective solution for minimising heat transfer through roof slabs. Moreover, it exhibited an outstanding 89% improvement in its waterproofing abilities, which is crucial for maintaining the structural integrity of buildings and ensuring the comfort of occupants. This groundbreaking development represents a significant stride towards sustainable construction practices. By harnessing waste materials like RHA and WBP, we not only reduce the environmental footprint of construction but also produce materials that enhance energy efficiency and comfort within buildings. As we continue to address the pressing challenges of climate change, solutions like these offer a glimmer of hope for a more sustainable and environmentally friendly future in the construction industry. In conclusion, the integration of Rice Husk Ash and Waste Brick Powder in roof slab construction is a pioneering approach that holds great promise for reducing greenhouse gas emissions, improving thermal comfort, and advancing sustainable construction practices. This innovation not only contributes to energy-efficient building design but also underscores the importance of repurposing waste materials to create valuable and environmentally responsible building materials.
item: Article-Full-text
Development of a plastering mortar using waste bagasse and rice husk ashes with sound mechanical and thermal properties
(Elsevier, 2022) Srikanth, G; Fernando, A; Selvaranjan, K; Gamage, JCPH; Ekanayake, L
The concept of using cleaner production technologies has become prominent in the present context for achieving sustainability in construction. Incorporating agricultural waste as cement replacements has shown enhanced mechanical and durability properties of the resulting mortar. A comparative study on the mechanical, thermal and environmental performance of a newly developed lightweight mortar containing agro-wastes namely Bagasse Ash (BA) and Rice Husk Ash (RHA) were investigated. Ordinary Portland Cement was partially replaced by BA at dosages of 0%, 5%, 15%, 20%, and 30% and RHA at dosages of 0%, 5%, and 15% by weight. A detailed investigation was carried out to determine the optimum material mix design which achieved good material properties. Results indicated that the addition of 30% BA as a partial replacement for cement improved the thermal performance by causing a 33% decrease in the thermal conductivity. Additions up to 30% of BA or 15% each from RHA and BA can be used to obtain mortar with compressive strengths complying with the standard values. At the same time, the combination of BA and RHA (15% each) decreased the thermal conductivity up to 31% compared to the conventional mortar. Further, the environmental assessment indicated that incorporation of BA and RHA in mortar can significantly reduce greenhouse gas emissions (i.e., 28% reduction per kg of BA).