Papers by Sekhar Chandra Dutta
Advances in Manufacturing Engineering and Materials, 2018
The utilization of smart structure technologies to mitigate the vibrations of structures have bee... more The utilization of smart structure technologies to mitigate the vibrations of structures have been the prime focus of numerous scientists involved in the area of structural vibration control. Smart materials serve multiple purposes like that of sensing, actuation and also exhibit the capability of modifying and adjusting the structural behavior when subjected to sudden external shock like earthquake or blast. Smart materials are basically defined as those materials possessing special features and can be applied in the design of structures to enhance the structural performance. Shape Memory Alloys (SMAs) are the most promising and prominent class of smart materials. When strained beyond 6–8%, SMAs possess the ability to regain its original shape. Reversible phase transformation is responsible for such sort of shape recovery. It can be either stress induced (pseudo-elasticity) or temperature induced (shape memory effect). This paper shows the potential of Nitinol (alloy of Ni and Ti) SMA damper to control structural vibrations when subjected to underground blast through a detailed computational study by considering a two-story steel frame as an example problem. Different bracing configurations of the damper are taken into account. A comparative study showing the effectiveness SMA braced damper over the conventional steel bracing is also carried out.
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Journal of Structural Fire Engineering, 2022
PurposeThe purpose of the paper is to mathematically model and predict the characteristics of the... more PurposeThe purpose of the paper is to mathematically model and predict the characteristics of thermo-mechanically treated (TMT) rebar when subjected to elevated temperatures.Design/methodology/approachData were collected from a few selected studies for developing the constitutive relations. Using the exposed temperature and the duration of heating as independent variables, the empirical relations were developed for determining the changes in mechanical properties of TMT rebars at elevated temperatures.FindingsRecrystallization of TMT rebar crystals took place around 500 °C, which led to a decrease in the dislocation density along with the increase of large-sized grains, resulting in the degradation of strength. Up to a temperature range of 500 °C, the normalized fracture strength was higher, while the normalized fracture strain is not so high. This indicated a failure of brittle nature.Originality/valueThis is an original work done by others as a study to theoretically predict the m...
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Exploring Natural Hazards, 2018
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International Journal of Applied Mechanics and Engineering, 2002
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The Structural Design of Tall and Special Buildings, 2021
Due to architectural and functional considerations, buildings with irregular configurations are f... more Due to architectural and functional considerations, buildings with irregular configurations are frequently constructed with rapid urbanization. During a seismic or blast activity, the performance of a building depends on various factors like adequate lateral strength, stiffness, ductility, regularity, and the extent of simplicity in the configuration. The irregular distributions of the stiffness, mass, and strength in the plan and height of the building create irregularity within the structures. The purpose of this study is to understand the nature of response under seismic ground motion and that obtained from ground vibration generated due to mine blasts if such buildings are situated near mines. This study also emphasizes on identifying the critical location of stress concentration of the structures under both seismic and mine blast‐induced ground motion. Base shear, fundamental natural periods, mode shapes, and member forces for a few buildings with typical irregular configurations and similar buildings with regular counterparts are obtained. Nonlinear dynamic analysis has been carried out on irregular buildings for confirming the trends in behavior observed from linear dynamic analysis. Since the mine blasts take place sequentially, the study also aims to prescribe a suitable delay interval between such series blasts to minimize the vulnerability of vertically irregular seismic structures to the possible extent.
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Current Science, 2020
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Structures, 2020
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Civil Engineering Research Journal, 2018
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June 2019, 2019
Pre-buckling vibration and buckling behaviour of composite skew plates subjected to linearly vary... more Pre-buckling vibration and buckling behaviour of composite skew plates subjected to linearly varying in-plane edge loading with different boundary conditions are studied. The total energy functional of the skew plate mapped from physical domain to computational domain over which a set of orthonormal polynomials satisfying the essential boundary conditions is generated by Gram-Schmidt orthogonalization process. Using Rayleigh-Ritz method in conjunction with Boundary Characteristics Orthonormal Polynomials, the total energy functional is converted into sets of algebraic equations for static stability problems and ordinary differential equation for free vibration problem. Pre-buckling vibration frequencies of the stressed skew plate are obtained by solving associated linear eigen value problem for free vibration and solution of the eigen value problem for static case results critical buckling load. From different parametric study, it is observed that the pre-buckling vibration frequenc...
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Structures, 2021
Abstract RC buildings with infilled masonry are very common in Northeast India and neighbouring c... more Abstract RC buildings with infilled masonry are very common in Northeast India and neighbouring countries like Nepal, along with open ground storey (OGS) buildings and bare framed buildings. In this region, due to the low financial capacity of the owners, most of the private buildings are constructed either with a consultation to local masons without any engineering input or by the engineers, mainly based on the thumb-rules. In such cases, design and construction quality (DCQ) and non-uniform distribution of the infill wall increase the damage level. Herein, an effort has been made to quantify the influence of DCQ, infill wall distribution, and their combined effect on seismic response. The vulnerability of low to mid-rise RC buildings is studied through fragility analysis using a simplistic nonlinear static analysis based method. The fragility curves show that inferior design and construction quality and the absence of masonry infill on the ground floor increases susceptibility to the manifold. However, the vulnerability of these RC buildings, including the ones with an open ground storey, can be decreased through well design and construction practices under controlled supervision. Thus, it may avoid collapse mainly for low seismic hazards that are often striking the Northeastern region of the Indian subcontinent and many other countries relatively more frequently than the very severe event. The overall observations that came out from the study may prove beneficial for selecting the suitable building configuration by design engineers, keeping a balance between safety and economy. The results obtained in the form of various curves and tables may be used for the preliminary design of new buildings and seismic risk assessment of existing buildings of such regions as well as of other areas with similar building typologies. Hence, the study may prove useful not only in the design offices, but the approach outlined in the study may be applied to various regions for vulnerability assessment, using the methodology having a fair compromise between rigour and accuracy. Finally, a large set of results generated following such a process may pave the way for refining design guidelines for performance-based design.
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Journal of Building Engineering, 2020
Abstract The Northeast region of India is considered to be the most seismically active zone in In... more Abstract The Northeast region of India is considered to be the most seismically active zone in India, having witnessed two major earthquakes (Mw > 8) in the past. Recently, the 2017 Ambasa earthquake (with Mw of 5.7) caused significant damage to unreinforced masonry (URM) buildings in Tripura, a Northeast state of India. The typical nature of damage observed in URM buildings during the post-earthquake damage survey highlights poor construction practices that have been used in this region even though the seismic hazard of the Northeast region of India is well established. In this context, the present study is an effort to evaluate through fragility analysis the vulnerability of existing low-rise URM buildings in Agartala, the capital city of Tripura, which in a broader sense represents the buildings of the entire Northeast region of India, through fragility analysis. In this regard, an assessment method based on a nonlinear static approach is used to develop bilinear capacity curve parameters. The capacity curve parameters are then used to estimate fragility functions. Fragility analysis shows that URM buildings would suffer heavy damage even for an earthquake having Peak Ground Acceleration (PGA) of 0.18 g, which is used to design buildings in the Northeast region of India according to the Indian seismic code. Fragility curves developed in this study may prove useful for assessing the seismic risk of the same building typology in other urban areas of Northeast India. In this first attempt, however, the effect of variability from construction quality and modelling uncertainty on the fragility curves is not considered in the limited scope of the present study.
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Structures, 2020
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Structures, seldom designed with adequate safety to blast hazards, are often designed for earthqu... more Structures, seldom designed with adequate safety to blast hazards, are often designed for earthquake. At this backdrop, presented herein is an attempt to achieve safety against explosive hazard through aseismic design methodology. The possibility of blast damage to ‘solitary’ structures appears to be comparable to that due to earthquake beyond a critical standoff distance of explosion. The study develops an equivalency of blast parameters (charge weight, critical stand-off distance) and earthquake characteristics (PGA) along with ductility capacity (represented by R) so as to yield similar damage. For example, beyond a critical stand-off distance of about 25m, structures designed elastically for earthquake with PGA of 0.2g may endure little damage (similar to that at R = 2 during earthquake) due to the explosion of 500 kg charge-weight. This not only helps to ascertain the level of safety of seismically designed buildings under blast, but also to decide the distance of fencing to be...
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Journal of the Institution of Engineers. India. Civil Engineering Division, 2000
Some elevated water tanks have failed due to torsional vibrations during earthquakes in the past.... more Some elevated water tanks have failed due to torsional vibrations during earthquakes in the past. The overall axisymmetric structural geometry and mass distribution of such structures may leave only a small accidental eccentricity between centre of stiffness and centre of mass. Such a small accidental eccentricity is not expected to cause a torisonal failure. This paper studies the possibility of amplified torsional behaviour of elevated water tanks due to such small accidental eccentricity in the elastic range, using two simple idealized systems with two coupled lateral-torsional degrees offreedom. The systems are capable of retaining the characteristic torsional-to-lateral stiffness ratios and torsional-to-lateral strength ratios of reinforced concrete elevated water tanks with two extreme categories of circular frame-type stagings : (a) staging with less number of columns and panels and (b) stagings with large number of columns and panels. A few representative ground motions are ...
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Current Science, 2020
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Structures, 2020
Abstract The paper aims to analyse the effect of confined explosion of high-explosive materials i... more Abstract The paper aims to analyse the effect of confined explosion of high-explosive materials in storage compartment. The present investigation proposes an improved structural configuration of the storage compartments for limiting the damage. An experiment was conducted in which a TNT charge had been detonated at the centre of a full-scale compartment constructed by following the Indian standards and the effect of the same was studied. Numerical simulation of the problems was obtained using a well-established software to supplement the experimental results for further understanding. The pressures developed at various locations (as obtained from Computation) were compared with the experimental data. The study also presents the development and validation of a non-propagating type sandwiched partition wall combinations so that it can reduce the severity of the damage. The effect of alternate materials and geometric changes are also studied through numerical models which increased the confidence in predictions. The study, thus, proposes alternate configurations to limit the damage due to the internal blast. Analytical study based on models calibrated with that of experiments gives reliability in the investigation even for few particular types of configuration of internal walls.
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Lecture Notes in Mechanical Engineering, 2017
Among many of the nonlinear equations presented throughout the decade, Forchheimer equation is th... more Among many of the nonlinear equations presented throughout the decade, Forchheimer equation is the most widely experimented and investigated. In this study, a simple CFD model created using ANSYS Fluent 15.0 has been used in order to predict the flow through a parallel flow permeameter packed with crushed stone of three different sizes. The results obtained were compared with the experimental results obtained from a similar kind of experimental set under similar type of field and media conditions. Furthermore, the statistical validation of the simulation results with the experimentally obtained results suggests that this type of model can be used for analysing the flow though porous media as a substitute of the complex laboratory experiments with a reasonable precision.
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Earthquake Engineering and Engineering Vibration, 2015
Traditionally seismic design of structures supported on piled raft foundation is performed by con... more Traditionally seismic design of structures supported on piled raft foundation is performed by considering fixed base conditions, while the pile head is also considered to be fixed for the design of the pile foundation. Major drawback of this assumption is that it cannot capture soil-foundation-structure interaction due to flexibility of soil or the inertial interaction involving heavy foundation masses. Previous studies on this subject addressed mainly the intricacy in modelling of dynamic soil structure interaction (DSSI) but not the implication of such interaction on the distribution of forces at various elements of the pile foundation and supported structure. A recent numerical study by the authors showed significant change in response at different elements of the piled raft supported structure when DSSI effects are considered. The present study is a limited attempt in this direction, and it examines such observations through shake table tests. The effect of DSSI is examined by comparing dynamic responses from fixed base scaled down model structures and the overall systems. This study indicates the possibility of significant underestimation in design forces for both the column and pile if designed under fixed base assumption. Such underestimation in the design forces may have serious implication in the design of a foundation or structural element.
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Majority of the people living in third world countries cannot afford a healthy, safe and long las... more Majority of the people living in third world countries cannot afford a healthy, safe and long lasting shelter because those built with conventional engineering materials are beyond their reach. They are forced to opt for traditional indigenous structures out of which masonry work is one of the oldest and popular-most. These structures are generally designed considering the vertical load acting on them in the form of dead and live loads, but the effect of lateral thrusts that is produced during earthquakes are normally ignored. In this context, the present paper attempts to develop simple and workable expressions and/or numerical estimation of various design parameters like strength, stiffness and energy dissipation capacity of masonry wall through experimental verification to aid the seismic design methodology for these structures. Experimental results have been collected from well accepted literatures as well as those generated through shake table tests by the authors on unreinforc...
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Papers by Sekhar Chandra Dutta