Computation Modeling, Materials, and Mechanics

Faculty Member: Dr.  Ioannis Koutromanos

CONCRETE AND MASONRY STRUCTURES – Constitutive models, performance assessment, retrofit techniques

Constitutive modeling of quasibrittle materials.

The behavior of concrete and masonry structures under cyclic loading is complicated, because a number of different mechanisms can affect the structural response. The occurrence of large cracks is common for older concrete and masonry construction, due to the possibility for shear cracking. Additionally, localized mode-I crack opening and shear (mode-II) slip is expected to occur along the masonry mortar bed joints. Numerical simulation is a powerful tool for the performance assessment of such systems, allowing the determination of the response for a variety of structural configurations, material properties and loading scenarios. To this end, constitutive models must be developed to account for the inelastic behavior of quasibrittle materials (materials whose behavior is affected by cracking processes) under multi-axial stress states.

The finite element simulation of strongly localized damage (large strains concentrated over very narrow bands) with continuum elements leads to an overestimation of the strength and ductility. To avoid such overestimations, discrete cohesive crack interface elements must be introduced in a finite element model to obtain the correct deformation patterns and the strength degradation associated with strongly localized damage.

Specific research topics include:

  • Formulation and numerical implementation of constitutive models to describe the stress-strain behavior of materials characterized by cracking processes.
  • Numerical analyses of inhomogeneous quasibrittle materials at the meso- or micro-scale to elucidate the effect of the constituent interaction on the observed macroscopic behavior.
  • Formulation and implementation of discrete crack interface elements to accurately simulate the effect of strongly localized damage.

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Seismic Performance Assessment of Reinforced Concrete and Masonry Buildings Using Computational Models

Reinforced concrete and masonry structures constitute a significant portion of the building inventory in various earthquake-prone areas around the world. The determination of the seismic performance of such systems is of uttermost importance for the hazard assessment of the built environment.

Detailed nonlinear finite element models can capture the cyclic load-displacement response and failure mechanisms of concrete and masonry buildings for any earthquake loading scenario. Finite element modeling can also determine the improvement in performance of older construction due to the application of retrofit techniques.

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Research topics include:

  • Validation of detailed analytical models using the results of experimental tests.
  • Performance assessment for archetype structural configurations, subjected to collections of ground motions scaled to various intensity levels.
  • Investigation of the effect of retrofit techniques on the seismic performance of old construction.

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