Faculty Publications
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Publications by NITK Faculty
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Item Analysis of berthing structures for wave induced forces(2011) Shanthala, B.; Rao, S.; Venkataramana, K.; Narayana, H.Countries surrounded by ocean can easily achieve tremendous progress in trade and industry provided proper planning of ports and harbours is made for transportation of goods and materials through sea transport. Berthing structures are to be designed for different load combinations. The deck of berthing structure is generally supported by vertical piles. Marine and offshore structures are subjected to wave and current forces and the loads acting on the member are cyclic and will induce time varying forces and moments. Due to this nature of wave forces and moments, the stress in the structure material fluctuates with respect to time, leading to progressive growth of cracks and they ultimately lead to fracture. This fatigue changes depends upon the wave action. To reduce wave and berthing forces, it is important to fix the alignment in such a way that incoming forces are minimum. Berthing structures are the facilities constructed in ports for berthing and mooring of vessels, for loading and unloading of cargo and for embarkment and disembarkment of passengers or vehicles. The berthing structures are designed for dead load, live load, berthing force, mooring force, earthquake load and other environmental loading due to winds, waves, currents etc,. In the present study layout of jetty for berthing 5000 DWT ship at NMPT is modeled using the ship dimensions from IS code and analyzed for the available environmental data from NMPT using StruCAD 3D software. The detailed analysis of the berthing structure for the significant wave height of 3.2m is carried out for a full cycle of wave and the Variation of deflection, forces and moments for perpendicular wave directions and different pile diameters is done by Static and Dynamic analysis. Dynamic Amplification Factor is calculated by comparing static and dynamic analysis results. Time history analysis is also done for the wave loading and deflection, forces and moments of the structure is calculated. From the results it is observed that the forces and moments are large as the diameter of pile increases and the deflection is reduced. From the time history analysis it is observed that as the pile diameter increases the maximum deflection occurs at the larger time period. It was found that at time period of 8.611sec peak response occurs. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Flexural fatigue analysis of steel fibre reinforced concrete(2012) Girish, M.G.; Chandrashekar, A.; Ravi Shankar, A.U.This paper presents the experimental investigation carried on Steel Fiber Reinforced Concrete (SFRC) subjected to repeated loading. The SFRC beam specimen of size 500mm × 100mm × 100mm containing mixed steel fibers of size 50mm × 2mm × 0.6mm and 0.5mm?× 30mm in different proportions were tested under two point flexural fatigue load at a frequency of 2Hz at various stress levels. The readings obtained from the flexural fatigue test were used to plot S-N diagram and also to perform statistical analysis using two parameter Weibull distributions. © 2012 CAFET-INNOVA TECHNICAL SOCIETY.Item Fatigue and Engineering Properties of Chemically Stabilized Soil for Pavements(Springer, 2013) Lekha, B.M.; Ravi Shankar, A.U.; Goutham, G.Soil stabilization is a technique to improve the weak soils and making them to meet certain requirements of the specific engineering projects. The type of soils available in Dakshina Kannada region of Karnataka State is laterite and Lithomarge clay. Its Plasticity Index is very high due to the presence of high percentage of silt and clay content. In the present investigation, an attempt is made to study the behaviour of laterite with and without adding chemicals. A chemical named Zycosoil, when added to water and mixed with soil alters its engineering properties that depend upon the type of the soil and dosage of chemical. These chemicals are liquid additives, which act on the soil to reduce the voids between soil particles and minimize adsorbed water in the soil for maximum compaction. In the present study, the effectiveness of Zycosoil in stabilizing the laterite soils of South Canara district is investigated through laboratory experiments. Various geotechnical properties are studied and correlations between different geotechnical properties and improvement in the soil properties with different percentages of chemical additions are derived. The important properties such as index properties, compaction characteristics, unconfined compressive strength parameters, California bearing ratio values and fatigue behaviour were studied. The results obtained indicate that there is an improvement in almost all properties with the addition of Zycosoil. © 2012 Indian Geotechnical Society.Item Evaluation of lateritic soil stabilized with Arecanut coir for low volume pavements(Elsevier Ltd, 2015) Lekha, B.M.; Goutham, G.; Ravi Shankar, A.U.Soil stabilization is a common method used by engineers and designers to enhance the properties of soil with different stabilizers. From ancient times, usage of natural fiber in soil as reinforcement is an effective technology adopted. This paper presents the effect of including randomly spaced Arecanut coir to the soil mix. The engineering properties and bearing capacity of a soil get enhanced by stabilizing it with Arecanut coir and a binding material (cement). The information available on experiments and research on the behavior of soil cement mixtures were collected and a few studies conducted on fiber reinforcement were referred. The current study mainly focuses on the durability test and physical evaluation of soil cement mixtures reinforced with Arecanut coir. Coir content was varied from 0.2% to 1% with an increment of 0.2%. For further improvement, a uniform dosage of 3% cement was added to soil. Laboratory tests including the Unconfined Compressive Strength (UCS), California Bearing Ratio (CBR), durability and fatigue behavior, were conducted as per standards. The test results indicated that the improvement in characteristics of the soil cement coir mixtures were functions of coir dosage, soil type and curing days. Durability test satisfied at 1% Arecanut coir with 3% cement. The stress-strain values were determined and damage analysis was conducted for the higher dosage of Arecanut coir using KENPAVE software. From the results it is observed that, the Arecanut coir reinforced cement soil mix can be used for low volume roads (traffic ?1 million standard axles) and few design cases have been discussed. © 2014 Elsevier Ltd.Item Effect of machine scatter on the rotating bending fatigue life of materials(De Gruyter peter.golla@degruyter.com, 2018) Banavasi Shashidhar, S.M.; Ravishankar, K.S.; Naik, P.S.Rotating bending fatigue test results vary from specimen to specimen even if materials are tested in a standard laboratory set up because rotating bending fatigue life or fatigue strength depends upon various factors due to its dynamic action. One method of testing may be machine scatter (offset and angular misalignment). Angular misalignments are unavoidable in dynamic machines due to continuous operation leading to transverse vibrations in specimens. The magnitude of transverse vibrations was measured manually by dial gauge arrangement. Experiments were carried out until fracture either with smooth running conditions or with the effects of offset and angular misalignment. The enhanced effect of misalignments on fatigue life was done through the histogram normal distribution technique. There was a clear distinction between the appearances of the fracture surfaces between the specimens subjected to smooth running conditions and specimen vibration, which reveals general fatigue fracture phenomena and intergranular fatigue cracks, larger decohesion of graphite nodules and isolated cleavage facets. The manual technique used without any resistance strain gauges, as they were not efficiently sustainable under repetitive loads, helped in understanding the dynamic machine scatter on fatigue life in an economical way where there were lesser concentrations in these areas. © 2018 Walter de Gruyter GmbH, Berlin/Boston 2018.Item Laboratory Evaluation of SMA Mixtures Made with Polymer-Modified Bitumen and Stabilizing Additives(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2019) Shiva Kumar, G.; Ravi Shankar, A.U.; Ravi Teja, B.V.S.Stone matrix asphalt (SMA) is a gap-graded mixture that consists of two parts, a high concentration coarse aggregate skeleton and a high binder content mortar. The coarse aggregate skeleton provides the mixture with stone-on-stone contact, giving it strength, while the high binder content mortar adds durability. The mortar is typically composed of fine aggregate, mineral filler, asphalt binder, and a stabilizing additive. A stabilizing additive such as natural fibers, mineral fibers, or polymers is added to SMA mixtures to prevent draindown. In addition, it has the potential of reinforcing and improving the tensile strength and cohesion of SMA mixtures. In this study, banana fiber (BF) and pelletized fiber (VP) are used as stabilizing additives to prepare SMA mixtures with conventional viscosity-graded (VG) 30 bitumen. Mixtures were prepared with different levels BF and VP content, and another mixture without any stabilizers was also prepared using polymer-modified bitumen (PMB). Superpave mix design, draindown, fatigue, rutting, workability, and moisture-induced damage properties were evaluated. Results indicated that addition of natural and pelletized fiber controls binder draindown and improves resistance to rutting, fatigue, and moisture-induced damage of SMA mixture. Further, polymer-modified SMA mixtures take less energy for densification compared to SMA mixtures with natural and pelletized fiber. Results also showed that even though polymer-modified SMA mixtures performed better, SMA mixtures with pelletized fiber provided comparable results. © 2019 American Society of Civil Engineers.Item Properties of Rejuvenated Reclaimed Asphalt Pavement Mixtures with Waste Glass Powder and Sisal Fibers for Pavements(American Society of Civil Engineers (ASCE), 2025) Marathe, S.; Akarsh, A.P.; Bhat, A.K.By exploring the usage of reclaimed asphalt pavement (RAP) mixtures in pavement construction, this study fills a substantial gap in the literature. The research includes a number of experimental investigations ranging from enhancing binder qualities to efficiently using waste engine oil (WEO) as a rejuvenator, as well as detailed performance evaluations using waste glass in powdered form. RAP materials were meticulously graded to provide stone matrix asphalt compositions. Throughout the study, a reinforcing supplement of 0.30% sisal fiber was utilized. The determination of optimal (fresh) binder content (OBC) of 3.50% and the selection of a lowered OBC of 2.50% with the adding of 20% WEO rejuvenator are among the preliminary key results. The study also effectively modified RAP mixes by including waste glass powder (WGP) as a mineral additive, yielding an optimal dose of 5.0% for a selected RAP mix. Performance testing on the improved RAP mixtures produced remarkable results. The Marshall stability value was increased by 20% with 5.0% WGP content. The Marshall quotient constantly fell between 2 and 5 kN=mm, which is the desired range. Tensile strength ratios often crossed 80%, and the drain-down potential was decreased by the use of WGP drastically. The combination with a 5.0% WGP content excelled the control mixture in rutting and fatigue testing and had a maximum retained Marshall stability of 93.1%. Additionally, pavement design utilizing Indian Roads Congress criteria demonstrated the viability of building pavements for low-volume roads using RAP mixtures in an efficient and sustainable manner. This study highlights the utilization of RAP to achieve sustainability in pavement building, offering a viable approach to bituminous pavement rehabilitation. © 2024 American Society of Civil Engineers.