Faculty Publications
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Item Studies on the influence of infill on dynamic characteristics of reinforced concrete frames(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2011) Chethan, K.; Ramesh Babu, R.; Venkataramana, K.; Sharma, A.The basic investigation under dynamic loads starts with the estimation of the natural frequencies of the structure or system under consideration. This is an important parameter under dynamic analysis. Hence a detailed study has been carried out on the influence of masonry infill (MI) on fundamental natural frequency of RC frames. MI though considered as non-structural element largely affect the strength, stiffness and ductility of the framed structure during the application of lateral forces such as wind and earthquake loads. Experimental and Numerical studies are carried out on RC frames under different configurations of MI in addition to bare frames. The RC frames are designed and detailed as per the relevant Indian standard codes. A simple numerical method has been formulated to obtain the natural frequencies of RC frames with MI using FE analysis. Tri-axial shake table is used for the determination of natural frequencies experimentally. This is a part of the collaborative project between BARC, Mumbai and CPRI, Bangalore focusing on the Response evaluation of RC frames under dynamic loading. This paper consists of numerical formulation, FE analysis, Shake table tests and comparison of results. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Studies on the dynamic characteristics of monolithic RC wall panels(2013) Amitha, S.B.; Chethan, K.; Bhavanishankar, S.; Annapurna, B.P.; Venkataramana, K.; Ramesh Babu, R.Monolithically built RC wall panels permits for the industrialized construction of a group of integrated buildings using mechanized, rationalized and mass-production procedure. This is a unique, fast and economical technique. Most of the national and international codes comprise of a brief design procedure of this type of construction. Lot of research is being carried out worldwide about the effect of dynamic loads on these structures. In this paper, FE analysis is done on a designed typical monolithic RC wall panel structure for all zones as per Indian code and the results are compared with different international codal provisions and the formulae presented by Saheb & Desayi and Doh & Fragomeni. This paper consists of background, design and construction of monolithic RC wall panel, FE analysis and comparison of results. © 2013 CAFET-INNOVA TECHNICAL SOCIETY.Item Performance of berthing structure under static and dynamic loading(CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2014) Yajnheswaran; Rao, S.In berthing structures, lateral forces are caused by impact of berthing ships, pull from mooring ropes and pressure of wind, current, wave and floating ice, seismic force, active earth pressure and differential water pressure, and vertical loads are due to self-weight of the structure and live load. In the analysis considered there is an expansion joint between berthing structure and diaphragm wall. The analysis is carried out using the finite element software PLAXIS 2D with absence of anchor and varying locations of anchor of diaphragm wall. In the case of static loading, the extreme displacement, and bending moment of the diaphragm wall were found to be about 0.07342m,24936.03knm/m respectively in absence of anchor. In the case of seismic loading of the structure, the maximum displacement and bending moment of the diaphragm wall were around0.0749m28263.68knm/m in absence of anchor condition. When anchor is provided the maximum displacement and bending moment were reduced to 0.00642m and 11830knm/m respectively. The variation of bending moment is 13.34% more in dynamic analysis than static analysis. The variation of displacement is 2%more in dynamic analysis than static analysis. © 2014 CAFET-INNOVA TECHNICAL SOCIETY.Item Prediction of modulus at various strain rates from dynamic mechanical analysis data for polymer matrix composites(Elsevier Ltd, 2017) Zeltmann, S.E.; Prakash, K.A.; Doddamani, M.; Gupta, N.Understanding and modeling the behavior of polymers and composites at a wide range of quasi-static and high strain rates is of great interest to applications that are subjected to dynamic loading conditions. The Standard Linear Solid model or Prony series frameworks for modeling of strain rate dependent behavior are limited due to simplicity of the models to accurately represent a viscoelastic material with multiple relaxations. This work is aimed at developing a technique for manipulating the data derived from dynamic mechanical analysis to obtain an accurate estimate of the relaxation modulus of a material over a large range of strain rate. The technique relies on using the time-temperature superposition principle to obtain a frequency-domain master curve, and integral transform of this material response to the time domain using the theory of viscoelasticity. The relaxation function obtained from this technique is validated for two polymer matrix composites by comparing its predictions of the response to uniaxial strain at a prescribed strain rate to measurements taken from a separate set of tension experiments and excellent matching is observed. © 2017 Elsevier LtdItem Aileron endurance test rig design based on high fidelity mathematical modeling(Springer-Verlag Wien michaela.bolli@springer.at, 2017) Prasad, M.; Gangadharan, K.V.This paper presents a model-based approach to design aileron endurance test rig (ETR). ETR is a dynamic load simulator which simulates aerodynamic load on-ground for verifying and validating the design, performance and stability of aileron actuator. Aileron actuator is a servo-controlled linear hydraulic actuator used to control the movement of ailerons in aircraft. Aileron is one of the primary flight control surfaces which controls roll of the aircraft. In ETR, Aileron actuator acts as unit under test (UUT) while a double-acting linear hydraulic actuator produces a dynamic load with the help of high pressure fluid source and electro-hydraulic servo valve (EHSV). The design of the test rig depends on load and velocity requirements which vary widely over the whole flight envelop and depends on deflection of surface, angle of attack, aircraft speed and altitude. One of the critical factor in designing ETR is to accurately model the interaction between the UUT and load system. This paper presents a simple yet powerful approach of free body diagram to account the power flow between the two systems. Model-based approach allowed to simulate the complete test rig behavior identifying the values of the critical parameters prior to building it. A high fidelity, non-linear mathematical model of aileron ETR is developed, simulated and verified. An appropriate load actuator and its electro-hydraulic servo valve are chosen to meet load and velocity requirements. The minimum rig structure stiffness is determined to ensure the stability of the load control system. A velocity feed-forward-based load controller along with proportional-integral control is implemented and tuned to meet the load control performance satisfactorily. Finally, the developed model is validated against the experimental data from actual test rig. © 2017, Deutsches Zentrum für Luft- und Raumfahrt e.V.Item A numerical modelling approach to assess the behaviour of underground cavern subjected to blast loads(China University of Mining and Technology, 2018) Kuili, S.; Sastry, V.R.The paper gives an insight into the behaviour of large underground caverns which are subjected to blast loads. Caverns are generally constructed in hard rock formation which compels us to use blasting methods for the excavation works. Comparative study was done between models with intact rock mass and discontinuities to assess the stability of cavern as a result of blast loads. Numerical modelling was performed with 3 dimensional distinct element code (3DEC) to analyse the performance of cavern walls in terms of displacement and to compute peak particle velocities (PPV) both around the cavern periphery and at surface of models. Results showed that the velocity wave with higher frequency exhibited large displacements around the periphery of cavern. Computation of PPV showed that model with horizontal joint sets showed lower PPV in comparison to model with intact rock mass. PPV values were also analysed on the surface for model consisting vertical joints spaced at 4 m intervals. Comparative study of PPV on surface vertically above the blast location between models with horizontal joints spaced at 4 m and vertical joints at 4 m intervals were conducted. Results depicted higher magnitudes of PPV for model with vertical joints in comparison to model with horizontal joints. © 2018Item Performance of magnetorheological elastomer based torsional vibration isolation system for dynamic loading conditions; ??????????????????????????(Central South University of Technology f-ysxb@mail.csut.edu.cn, 2020) Shenoy, S.K.; Kuchibhatla, S.A.R.; Singh, A.K.; Gangadharan, K.V.Vibration isolation is an effective method to mitigate unwanted disturbances arising from dynamic loading conditions. With smart materials as suitable substitutes, the conventional passive isolators have attained attributes of semi-active as well as the active control system. In the present study, the non-homogenous field-dependent isolation capabilities of the magnetorheological elastomer are explored under torsional vibrations. Torsional natural frequency was measured using the serial arrangement of accelerometers. Novel methods are introduced to evaluate the torsional stiffness variations of the isolator for a semi-definite and a motor-coupled rotor system. For the semi-definite system, the isolation effect was studied using the frequency response functions from the modal analysis. The speed-dependent variations for motor-coupled rotor system were assessed using the shift in frequency amplitudes from torque transducers. Finite element method magnetics was used to study the variations in the non-homogenous magnetic field across the elastomer. The response functions for the semi-definite rotor system reveal a shift in the frequency in the effect of the magnetic field. Speed-dependent variations in the frequency domain indicate an increment of 9% in the resonant frequency of the system. © 2020, Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature.Item Studies on free and forced vibration of functionally graded back plate with brake insulator of a disc brake system(Springer Science and Business Media Deutschland GmbH info@springer-sbm.com, 2020) Patil, R.; Joladarashi, S.; Kadoli, R.The back plate with brake insulator of a disc brake system used in automobile is a sandwich structure. Mitigating brake squeal associated with the operation of the disc brake has been a focus of many automobile researchers. As on today’s practice, steel–acrylic–steel is used for back plate–brake insulator assembly. The present study focuses on proposing Al - Al 2O 3 functionally graded metal ceramic composite material (FGM) for the back plate attached with conventional Steel–Acrylic brake insulator. Accordingly, a comparison study is presented in terms of the free and forced vibration characteristics of different material combinations for back plate–brake insulator sandwich beams such as steel–acrylic–steel, FGM–acrylic–steel, FGM–acrylic–aluminium and steel–acrylic–aluminium. The associated governing equations for sandwich beam which are well established in the literature are presented, and they are solved for simply supported conditions using trigonometric displacement functions. The real and imaginary parts of the various parameters come into the picture because of complex shear modulus of viscoelastic core. The comparison study among the combinations reveals that the natural frequency, loss factor and with regard to dynamic loading the imaginary part of transverse displacement, axial displacement, stress and strain of FGM–acrylic–steel are higher. As a result, FGM–acrylic–steel is suitable combination for back plate and brake insulator assembly which enhances the damping capacity of overall disc brake system and also helps in reducing brake squeal problem associated with operation of disc brake system. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Item Experimentation on dynamic compressive response of bio-inspired helicoidal structured Basalt/Hemp/polyurethane rubber sandwich composites(Elsevier Ltd, 2024) Gowda, D.; Mahesh, V.; Mahesh, V.; Ravishankar, K.S.In this article, to incorporate sustainability, enhance recyclability and achieve a good trade-off between the cost-weight-energy absorption performance, bioinspired helicoidal structured Basalt (B)/Hemp (H)/Polyurethane (PU) rubber hybrid composites are proposed, and their dynamic compressive response is experimentally investigated using a split Hopkinson pressure bar (SHPB) setup. These composites' high strain rate performance subjected to both in-plane and through-plane directions are studied. The strain rates ranging from 4254 to 10,750 s-1 are achieved by varying the striker bar's input pressure. In addition, the performance of the bioinspired helicoidal design is compared against the uniform monolithic and hybridised fibers laminated structures. The experimental results suggest that the dynamic compressive properties of Basalt/Hemp-helicoidal (BH-helicoidal) laminates were on compar with that of B-laminates, achieving an almost 30% weight reduction. The optimised fiber orientation at a helical angle of 120 enhances interlaminar shear strength, mitigating buckling and delamination failures, thereby improving BH-helicoidal laminate's structural integrity and dynamic compressive properties. Further, the through-plane dynamically loaded samples displayed better compressive properties due to increased stiffness than in-plane samples. The PU rubber matrix was thermally softened at higher strain rates, enhancing the flow stress. The strengthening mechanism of the proposed composites was evaluated through Cowper-Symonds, strain rate sensitivity, and thermal activation volume parameter. Macroscopic and microscopic imaging was proposed to understand the damage behaviour of laminates as a function of loading direction. Overall, BH-helicoidal laminate is favoured for ballistic application due to its cost-effectiveness and sustainable design. © 2024 Elsevier LtdItem Static and dynamic performance of single batter piles embedded in slope(Springer, 2024) Kumar, S.; Najar, D.S.; Sarkar, R.; Nainegali, L.The performance of pile foundations embedded in the sloping ground has received the least attention. Further, considering piles with batter angles, the investigation is even more limited. In this study, 3D non-linear finite element analyses were conducted to investigate the lateral load-carrying behaviour of vertical and batter (with angles -5°, +5°, -10° and +10°) pile foundations embedded in slope. Firstly, static analyses were performed, and the behaviour of the batter piles was compared with the vertical piles, considering the piles are embedded in a 30° slope of height 5.0 m with medium-stiff clay. It was observed that the capacity of piles reduces when they are installed on sloping ground. Negative batter piles were found to be more effective than the vertical piles in the slope. Next, the performances of the piles were investigated for dynamic lateral loading. It was inferred that the negative batter piles provide better resistance under lateral loading than the vertical and positive batter piles in sloping ground under dynamic loading as well. © Indian Academy of Sciences 2024.