S. Talukdar
Indian Institute of Technology Guwahati
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Featured researches published by S. Talukdar.
Finite Elements in Analysis and Design | 2004
Anjan Dutta; S. Talukdar
Damage identification in civil engineering structures using the dynamic system parameters has become an important area of research. A reliable, time and cost effective method is therefore required to evaluate and localize damage using the changes in dynamic parameters between the intact and damage states. The dynamic parameters must be calculated in as accurate manner as possible. In the present work, eigenvalue analysis is carried out using Lanczos algorithm in an adaptive h-version finite element environment in order to control the discretization error for accurate evaluation of modal parameters. Standard Ahmed Shell elements have been used for the discretization of bridge deck. Changes of natural frequencies between the damaged and intact model have been observed. A better localization of damage could be done by considering curvature of the mode shapes, which shows more sensitivity than the mode shapes themselves. Numerical studies are conducted to demonstrate the necessity of adaptive eigenfrequency analysis by considering simply supported and continuous bridges containing damaged parts at different locations and their usefulness in the application for damage detection in the field.
Journal of Vibration and Acoustics | 2007
M. Karthikeyan; Rajiv Tiwari; S. Talukdar
A model-based algorithm has been developed, in order to locate and quantify the size of a crack, based on free vibration measurements of a cracked beam. Measured natural frequencies (at least two) and corresponding mode shapes of the cracked beam are used in the identification algorithm. The Euler-Bernoulli beam theory is used to model the beam. The crack of the beam is modeled through standard five crack flexibility coefficients, by considering bending effects only. Damping is assumed to be Rayleighs damping. The finite element method is used in the simulation of the cracked beam. The present algorithm is iterative in nature and the iterations are carried out until the estimated and assumed crack depth ratios (as well as its location) become close up to the desired accuracy. The applicability of the algorithm has been tested through numerical examples and is found to be adequate even in the presence of the measurement noise in modes shapes and measurement errors in natural frequencies.
Journal of Vibration and Acoustics | 2008
M. Karthikeyan; Rajiv Tiwari; S. Talukdar
The present work aims at the development of a method for the crack detection, localization and sizing in a beam based on the transverse force and response signals. The Timoshenko beam theory is applied for transverse vibrations of the beam model. The finite element method is used for the cracked beam forced vibration analysis. An open transverse surface crack is considered for the crack model, which contains standard five flexibility coefficients. The effect of the proportionate damping is also included. A harmonic force of known amplitude with sine-sweep frequency is used to dynamically excite the beam, up to few flexible modes, which could be provided with the help of an exciter. In practice, linear degrees of freedom (DOFs) can be measured quite accurately; however, rotational DOFs are difficult to measure accurately. All rotational DOFs, except at crack element, are eliminated by a dynamic condensation scheme; for elimination of rotational DOFs at the crack element, a new condensation scheme is implemented. The algorithm is iterative in nature and starts with a presumption that a crack is present in the beam. For an assumed crack location, flexibility coefficients are estimated with the help of forced responses. The Tikhonov regularization technique is applied in the estimation of bounded crack flexibility coefficients. These crack flexibility coefficients are used to obtain the crack size by minimizing an objective function. With the help of the estimated crack size and measured natural frequency, the crack location is updated. The procedure iterates till the crack size and location get stabilized up to the desired level of accuracy. The algorithm has a potential to detect no crack condition also. The crack flexibility and damping coefficients are estimated as a by-product. Numerical examples, with the simply supported and cantilevered beams, are given to justify the applicability and versatility of the algorithm in practice. With the numerically simulated forced responses, which have the noise contamination and the error in the natural frequency measurements, the estimated crack parameters (i.e., the crack location and size) are in good agreement.
Journal of Astm International | 2008
Aminul Islam Laskar; S. Talukdar
A new concrete rheometer has been presented including its concept, actual design, working principle, calibration, and repeatability. Resistance offered by vertical wall of cylindrical container to concrete has been taken into consideration to represent actual flow condition of concrete during shearing. An expression for total shear stress has been derived whereby shear stress versus torque and overall shear strain rate versus rotational frequency relationships have been established for the given geometry of the rheometer. A magneto-rheological fluid has been tested with the present rheometer and the results have been compared with the test results obtained by HAAKE RS1 rheometer to validate the present analytical approach. Repeatability tests were conducted with different concrete mixes and results were found to be reasonable.
Shock and Vibration | 2007
K. Nallasivam; Anjan Dutta; S. Talukdar
The impact on curved box-girder bridges due to vehicle moving across rough bridge deck have been analyzed using bridge-vehicle coupled dynamics. The bridge deck unevenness has been assumed to be a homogeneous random process in space specified by a PSD function. The analysis incorporates the effect of centrifugal forces due to vehicle moving on curved bridge. The curved box-girder bridge has been numerically modeled using computationally efficient thin-walled box-beam finite elements which take into account the torsional warping, distortion and distortional warping, that are important features of thin-walled box girders. Rigid vehicle with longitudinal and transverse input to the wheels giving rise to heave-pitch-roll degrees of freedom has been considered. The theoretical bridge model used in simulation study has been validated by a free vibration experiment using impact excitation. The impact factors for several response parameters such as bending moment, shear force, torsional moment, torsional bi-moment, distortional moment, distortional bi-moment and vertical deflections have been obtained for various bridge-vehicle parameters. Both constant velocity and forward acceleration of the vehicle have been considered to examine impact factor. The results highlighted that the impact factors of a curved box girder bridge corresponding to torsion, distortion and their corresponding bimoments have been observed to be generally very high, while those of the other responses are also relatively higher than that of corresponding straight box girder bridge.
Finite Elements in Analysis and Design | 2004
Animesh Das; Anjan Dutta; S. Talukdar
The effects of random road surface roughness on the impact effects on cable-stayed bridge due to moving vehicles are investigated. The random road surface roughness is described by a zero-mean stationary Gaussian random process. The bridge is modeled by finite element method as a planar structure. Each moving vehicle is idealized as a single degree-of-freedom lumped mass system, in which a mass is supported by a spring and a dashpot. The impact effects of random road surface roughness on a cable-stayed bridge vary a lot, depending on the location and the structural components. The entire computation has been carried out in an adaptive finite element environment. It has been clearly demonstrated that the dynamic amplification factor, a significant parameter for bridge design can become highly erroneous if the errors due to both space and time discretization are not kept within control.
Journal of Materials in Civil Engineering | 2017
Sulaem Musaddiq Laskar; S. Talukdar
AbstractGeopolymer has earned a significant position in the construction industry. A number of researchers have attempted to use it as a concrete-repairing material. To enrich the literature with r...
Canadian Journal of Civil Engineering | 2009
Aminul Islam Laskar; S. Talukdar
Monitoring of workability is a critical issue since high-performance concrete is susceptible to small changes in mixture proportions that have a direct impact on workability and hardened properties. Test results in fundamental units such as yield stress and plastic viscosity are needed to characterize workability of high-performance concrete. In the present study, rheological properties of concretes with different workability were evaluated with a rheometer fabricated in the laboratory. Yield stress and plastic viscosity measured for various mixes were combined together with shear strain rate to obtain a single parameter, the energy dissipation rate per unit volume, which was used to develop a workability scale.
Vehicle System Dynamics | 2000
D. Yadav; S. Kamle; S. Talukdar
Analysis for response statistics evaluation of a flexible vehicle travelling with variable velocity over nonhomogeneously profiled flexible track is presented with a heave-pitch-roll model. The vehicle body is idealised as a flexible member with variable cross-section, inertia, damping and stiffness distributions. The vehicle may also have variable section slender elastic attachments. Coupled dynamics with rigid body heave-pitch-roll modes and elastic bending-torsion modes of the vehicle body along with coupled bending-torsion modes of the attachments are considered. Equivalent linear suspension system characteristics are employed for developing the analysis. Numerical results are presented for an aircraft with tricycle landing gear arrangements and comparison is made with other models.
Structural Health Monitoring-an International Journal | 2018
Palash Dey; S. Talukdar
This article presents a study for detecting crack parameters (crack location and crack-depth ratio) in horizontally curved thin-walled channel section beams utilizing only dynamic information from a post-damage event based on combined statistical and optimization tools. A combined response surface methodology and genetic algorithm have been utilized in the present research work. Finite element computations based on design of experiment have been used in order to obtain the coefficients of a second-order polynomial model for the response surface function. Genetic algorithm is then used as a searching tool to determine the optimum parameters by minimizing an objective function which is formed as the root mean square of the errors between the computed responses from response surface functions and measured responses. Two cases of different subtended central angles are considered to illustrate the approach. Each case required 18 laboratory experiments to provide measured input to the proposed integrated approach. It was found that large variation can occur in the calculation of natural frequencies of thin-walled beams, when the effect of warping stiffness is neglected in mathematical model. This study reveals that the precision of the localization and quantification of cracks are dependent on subtended angle. The present method has great potential in crack detection as it does not require the response of an uncracked beam as baseline criteria.