RATING THE LIMITING SHIFT OF A STORY AS A CRITERIA FOR A SPECIAL LIMITING STATE

Abstract

The article presents a verification of one of the existing seismic resistance criteria found in domestic and international standards. The study examines the limit value of relative displacement of the first-floor column in a reinforced concrete building under seismic loading using two different material models in a nonlinear dynamic framework. The article introduces a modeling approach that allows for the assessment of the seismic resistance of reinforced concrete buildings and structures in a nonlinear dynamic framework. The objective of the work is to verify the standardized limit drift value for a specific structural scheme when modeling the column with volumetric elements including direct reinforcement.

Two different material models, implemented in the LS-DYNA software, were used in the column modeling. The first material model is the Karagozian & Case (K&C) Concrete model. This material model represents a three-invariant model with multiple strength and yield surfaces. The model's input parameters include various factors, including empirical ones, such as yield strength, ultimate strength, and residual strength, which are key parameters for the damage accumulation function. The second material model is the Continuous Surface Cap Model, represented by a closed surface (a cap model with a continuous yield surface). This model also accounts for damage accumulation and the degradation of stiffness and strength under cyclic loading.

The results include isocontours of the damage accumulation function in concrete, isocontours of strain and stress intensities in concrete and reinforcement at various time steps, as well as graphs of the damage accumulation functions. The findings confirm the accuracy of the numerically determined limit displacement value and identify which material model most precisely represents the failure mechanisms of concrete, thus indicating its suitability for further in-depth research.