Dr.-Ing. Ajmal Hasan Monnamitheen Abdul Gafoor
Damage in concrete: Modeling and numerical analysis
A proper understanding of deformation behavior and fracture mechanisms of different ma-
terials that used in the field of civil enginering is very essential to ensure the safety of
structures against complete failure. Concrete is the most commonly used construction ma-
terial among others due to easy applications. Several numerical models from elasto-plastic
models, fracture models, elasticity based damage models to coupled plastic-damage models
have been developed to simulate its deformation behavior. However, the applications of
these models are limited to particular loading conditions. The complex loading conditions
as in case of earthquakes make the damage process even more complicated, if cyclic and
dynamic loadings have not been considered. On the other hand, concrete exhibits dis-
tributed micro-cracking pattern under multi-directional loads. Therefore, the model must
incorporate damage induced anisotropy inherently for a more reliable representation of
damage and to capture the direction of possible damage evolution.
Previous investigations
The previous work focussed on the devlopement of a 3D continuum damage formulation
using a unified equivalent strain that depends on invariants of elastically predicted stresses.
The failure of concrete in tension and compression was characterized by softening behavior
by means of two history deformation variables were introduced to describe the unilateral
behavior (i.e., crack opening and closure) effectively. The implicit-gradient method was
also incorporated for regularizing the boundary value problem. The irreversible permanent
strains were captured by a failure surface A very good agreement by the model was achieved
with experimental results qualitatively and quantitatively. A few applications of the model
were also analyzed to check the ability and effectiveness of the model in predicting fracture
phenomena such as crack initiation and propagation.
Current investigations
Based on the previous numerical investigations, it is found that the assumption of isotropic
damage behavior is not sufficient to model the actual behavior of concrete. Moreover,
the experimental evidences even prove that the material degradation of the concrete also
depends on the direction of applied loading. Therefore, the present work aims at the
development of model incorporating the damage induced anisotropy by introducing multi-
damage loading functions in tension as well as in compression. In order to include the
unilateral (crack opening/closure) behavior of the material, a multiplicative parameter is
defined based on the principal stresses and strains. The ability of the models will be
validated and verified using selected benchmark examples.
Publications within the framework of the RTG/DAAD:
Doctoral thesis:
A.H. Monnamitheen Abdul Gafoor. Modeling and numerical analysis of damage behavior of concrete. PhD thesis, Institut für Statik, TU Braunschweig, 2019 DOI.
Publications in peer-reviewed scientific journals / Book chapter
A. H. Monnamitheen Abdul Gafoor and D. Dinkler. Modeling damage behavior of concrete subjected to cyclic and multiaxial loading conditions. Structural Concrete. 2021;1–15. https://doi.org/10.1002/suco.202100109
A. H. Monnamitheen Abdul Gafoor and D. Dinkler. A discussion on locking and nonlocking gradient-enhancement formulations for concrete behavior, in: SK Saha and M Mukherjee(Eds.), Recent Advances in Computational Mechanics and Simulations, Lecture Notes in Civil Engineering, vol 103, Springer, Singapore, 2021.
A. H. Monnamitheen Abdul Gafoor and D. Dinkler. A Gradient-Damage Model for Cyclic Behavior of Concrete, in: D. Maity, P. G. Siddheshwar, S. Saha (Eds.), Advances in Fluid Mechanics and Solid Mechanics, Lecture Notes in Mechanical Engineering, Springer, Singapore, pp. 309–318, 2020.
A. H. Monnamitheen Abdul Gafoor, D. Dinkler. A macroscopic gradient-enhanced damage model for deformation behavior of concrete under cyclic loadings. Arch Appl Mech 90, 1179–1199, 2020.
Timo Stein, Ajmal Gafoor and Dieter Dinkler. Modeling inelastic-anisotropic damage behavior of concrete considering lateral deformation. Proceedings in Applied Mathematics and Mechanics (PAMM), 20(1), 2020.
A. H. Monnamitheen Abdul Gafoor and D. Dinkler. A model for coupled inelastic deformation and anisotropic damage behaviour of concrete. Proceedings in Applied Mathematics and Mechanics (PAMM), 17(1):241-242, 2017.
A. H. Monnamitheen Abdul Gafoor and D. Dinkler. Influence of deformation history parameters on softening behaviour of concrete. Proceedings in Applied Mathematics and Mechanics (PAMM), 16(1):155-156, 2016.
Conference contribution with publication in conference proceedings:
A. H. Monnamitheen Abdul Gafoor and D. Dinkler. A discussion on locking and nonlocking gradient-enhancement formulations for concrete behavior. Proceedings of 7th International Congress on Computational Mechanics and Simulation (ICCMS 2019), IIT Mandi, India, December, 2019.
A. H. Monnamitheen Abdul Gafoor and D Dinkler. A gradient-damage model for cyclic behavior of concrete. Proceedings of 63rd International Congress of Indian Society of Theoretical and Applied Mechanics (ISTAM), Dayananda Sagar Univeristy, Bangalore, India, Paper ID-159, 2018.
A. H. Monnamitheen Abdul Gafoor, D. Dinkler. A simplified damage model for unilateral behavior of concrete. Conference Proceedings of 7th GACM Colloquium on Computational Mechanics for Young Scientists from Academia and Industry, pages 312 - 315, Stuttgart, 2017.
A. H. Monnamitheen Abdul Gafoor. Isotropic Damage Model Using a New Damage Equivalent Strain. Report of 4th IABSE Young Engineers Colloquium (YEC 2017), pages 38-39, Bochum, 2017.