Completed Projects
Numerically integrated MVCCI technique for fracture analysis of plates and stiffened panels
Objective
To develop methodologies for fracture analysis of plates and stiffened panels by using a numerically integrated MVCCI technique
Challenges
- Evaluation of constants used in the polynomial to represent displacement and stress variation
- Independent of type of finite element
Methodology
- Numerically integrated MVCCI technique
- Gauss integration technique with different integration rules
Achievements
- An efficient and novel NI-MVCCI technique demonstrated for 4-noded bilinear, 8-noded (regular & quarter-point), 9-noded Lagrangian and 12-noded cubic isoparametric family of finite elements
- Generalized expressions for evaluation of geometric factors of stiffened panel for various position and size of stiffeners and crack lengths
XFEM methodologies for crack growth analysis and remaining life prediction of metallic structural components
XFEM methodologies for crack growth analysis and remaining life prediction of metallic structural components
Challenges
- Modelling of moving discontinuities (crack) in finite element frame work
- Singularity modelling at the crack tip
- XFEM formulations for stiffened panels
Methodology
- Enrichment of standard displacement based approximation with additional functions
- stiffness matrix formulations of fully enriched element with heaviside enrichment and crack tip enrichment
- Level set representation of crack
- Stress intensity factor evaluation using domain form of interaction integral
- Crack growth study and remaining life prediction
Achievements
- An integrated XFEM formulations for crack growth analysis and remaining life prediction of stiffened and unstiffened panels
- Damage tolerant curves for unstiffened and stiffened panels
Evaluation of loss of prestress of a novel externally prestressed concrete end block by finite element analysis
Evaluation of loss of prestress of a novel externally prestressed concrete end block by finite element analysis
Objective
To evaluate loss of prestress of a novel externally prestressed concrete end block
Challenges
- Integrated modelling of steel bolts, prestressing force, reaction force, connections, concrete and reinforcement
Methodology
- Coupled finite element model by employing contact, gap, solid and link elements for effective load transfer
- Transfer of prestress in shear mode
- Prestress loss represented as slope and slip of the steel bracket
Advanced fracture mechanics based analysis of strutural components
Objective
- To develop advanced methodologies for fracture analysis of concrete and metallic structural components
Challenges
- Accounting for cohesive stresses and size effect that contribute significantly to fracture behaviour depending on material characteristics
- Size independent specific fracture energy for normal strength concrete (NSC), high strength concrete (HSC) and ultra high strength concrete (UHSC)
- An unique tensile stress vs crack width relation for various concretes corresponding to their fracture energy
Methodology
- Modified the plastic zone size to account for underload
- Crack configuration modelled through shape factors
- Applied linear superposition principle to evaluate stress intensity factor
- Load – deflection tail correction and boundary effect method employed to determine size independent specific fracture energy
- Crack hinge concept and inverse analysis applied to deduce tensile stress vs crack width relation
Achievements
- Generalized residual stress model for crack growth analysis and remaining life prediction of structural components
- Fracture mechanics based model for concrete components by accounting for cohesive stress and size effect
- Size independent specific fracture energy and corresponding constitutive relationship for fracture mechanics based design of concrete structural components
Methodologies for advanced finite element analysis and crack width prediction in RC structures / components
Methodologies for advanced finite element analysis and crack width prediction in RC structures / components
Objective
- Development of a strain based constitutive model for nonlinear finite element analysis of RC flexural members with the capability to predict crack width
Methodology
- A new two-phase constitutive model for concrete under tension defined by a bilinear softening law
- The model integrated with layered geometry definition of the structure to accommodate continuously changing crack direction while progressing through thickness
- Bond-slip behaviour defined by modelling the shear transfer between reinforcing bar and concrete after cracking
- Crack width expression as function of concrete strain and fracture energy by applying energy equivalence principle
Finite element mesh of beam considering half-symmetry
Crack width prediction in RC structures/components
Computational modelling of RC structures using damage mechanics approach
Challenges
- Damage quantification in a structure at local and global levels
- Development of mesh-invariant model to predict cracking location in a RC structure
Methodology
- Damage mechanics based tension-softening model incorporating a scalar damage variable
- Effect of crack propagation reproduced by coupling the tension-softening model with a smeared rotating crack model
- Damage evolution law according to strain equivalence principle
Achievements
- Critical modelling issues such as stress locking, mesh-induced directional bias, and instability in response computation at near-ultimate load successfully addressed by a coupled model
- Quantification of damage at local and global levels in a structure
- Demonstration on large size RC chimney
- Serves as a prediction tool to decide on maintenance and retrofitting of the structure
Drift Vs Damage Variable