Nitin Kumar
@ucdavis.edu
Civil and Environmental Engineering
University of California Davis
RESEARCH, TEACHING, or OTHER INTERESTS
Civil and Structural Engineering
Scopus Publications
Scholar Citations
Scholar h-index
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Scopus Publications
P. Vijayalakshmi, Nitin Kumar, and Vivek R. Das
Springer Nature Singapore
M. Manoj, Vivek R. Das, and Nitin Kumar
Springer Nature Singapore
Nitin Kumar, Michele Barbato, Erika L. Rengifo-López, and Fabio Matta
American Society of Civil Engineers (ASCE)
Sujata Subedi, Gabriel A. Arce, Marwa M. Hassan, Michele Barbato, Maria Teresa Gutierrez-Wing, and Nitin Kumar
Springer Science and Business Media LLC
Nitin Kumar, , Michele Barbato, Erika L. Rengifo-López, Fabio Matta, , , and
MIM Research Group
Received 26 Feb 2022 Revised 13 May 2022 Accepted 17 May 2022 Finite element (FE) simplified micro-modeling techniques are commonly used to investigate and predict the mechanical behavior of masonry structures because they provide a good compromise between accuracy and computational cost. These FE techniques generally discretize masonry structural elements into expanded masonry units and zero-thickness interface joints of assumed known locations. These joints correspond to actual masonry joints and to preferential cracking surfaces, which are often placed vertically in the middle of the expanded masonry units to simulate the cracking mechanisms that are typically observed in masonry bricks and blocks. Three different versions of simplified micromodels (SMMs) are widely used in the literature to model the response of masonry walls and assemblies: SMMs with rigid, elastic, and elasto-plastic constitutive models for the expanded masonry units. All SMMs are based on the hypothesis that the masonry inelastic behavior and cracking are concentrated along the pre-defined zero-thickness interface joints. The hypothesis is often satisfied for ordinary masonry, in which masonry units are generally stronger than the masonry joints, i.e., mortar and unit-mortar interface. However, this hypothesis is not always satisfied for historical masonry with units of irregular shapes or for earth block masonry, in which masonry units and masonry joint can have similar mechanical properties. This paper highlights the capabilities and limitations of SMM techniques by comparing the experimentally-measured and numerically-simulated response of ordinary and earth block masonry walls, for which well-documented experimental results are available in the literature. It is found that SMMs can properly reproduce the mechanical behavior of masonry when the masonry units are significantly stronger than the masonry joints; however, SMMs produce poor estimates of the mechanical response when this hypothesis is not satisfied. This finding highlights the need to develop more general FE models to investigate the mechanical behavior of different masonry materials and construction techniques, as well as to identify the parameters controlling the cracking patterns and the conditions under which SMM techniques can be accurately use.
Nitin Kumar and Michele Barbato
Elsevier BV
Nitin Kumar and Michele Barbato
American Society of Civil Engineers (ASCE)
AbstractA new interface element constitutive model is proposed in this study for analyzing masonry using the simplified micromodeling (SMM) approach, in which mortar and two unit–mortar interfaces ...
Nitin Kumar, Michele Barbato, and Robert Holton
American Society of Civil Engineers (ASCE)
Nitin Kumar and Dipti Ranjan Sahoo
Elsevier BV
Nitin Kumar, Harish Lambadi, Manoj Pandey, and Amirtham Rajagopal
Informa UK Limited
Masonry is a heterogeneous anisotropic continuum, made up of the brick and mortar arranged in a periodic manner. Obtaining the effective elastic stiffness of the masonry structures has been a challenging task. In this study, the homogenization theory for periodic media is implemented in a very generic manner to derive the anisotropic global behavior of the masonry, through rigorous application of the homogenization theory in one step and through a full three-dimensional behavior. We have considered the periodic Eshelby self-consistent method and the finite element method. Two representative unit cells that represent the microstructure of the masonry wall exactly are considered for calibration and numerical application of the theory.
Nitin Kumar, Amirtham Rajagopal, and Manoj Pandey
Informa UK Limited
Computational modeling of failure in quasi-brittle materials at various length scales is important. In this work we present a rate independent cohesive zone model for modeling failure in quasi-brittle materials. The proposed model can simulate cracking, slipping, and crushing of planes through a traction-separation law. A single surface hyperbolic failure criterion, which naturally comes as a direct extension of Coulomb friction criterion with cut-off in tension and cap-off in compression, has been developed. A Euler backward integration scheme together with a global-local Newton solver compatible with a substepping strategy has been used in numerical computations. The proposed model is then used for modeling of shear wall panels. The numerical results obtained are validated by comparing them with experimental results available in literatures.
Dipti Ranjan Sahoo and Nitin Kumar
Elsevier BV
P.C. Ashwin Kumar, Dipti Ranjan Sahoo, and Nitin Kumar
Elsevier BV
Nitin Kumar, Rajagopal Amirtham, and Manoj Pandey
Elsevier BV