Numerical analysis of RC plane structures: a concentrated nonlinear effect approach (original) (raw)
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2015
This work aims to develop and identify a new model for reinforced concrete joint element subject to cyclic loadings. Based on experiments and 3D numerical modeling, a simplified model of RC beam-column joint is introduced (within the framework of macro-element). In a first experimental study, this joint will be tested under reverse cyclic loading applied at the beam tip to identify its behavior under this kind of loading in terms of strength, stiffness and ductility. In parallel of experiments, a finite elements model of the joint based on 3D finite elements is presented to highlight and define the nonlinear mechanisms involved in the ruin of the assembly. This step will confirm the experimentally observed phenomena: damage, friction, plasticity. Secondly, a simplified macro-element model for beam-column joint, associated to a nonlinear behavior, is introduced to reflect the response of the joint under cyclic loading loads. Model parameters will be identified from experimental resul...
Calibration of the Length of the Plastic Hinge for Numerical Models of Reinforced Concrete Members
Buildings
A proper and computationally efficient numerical modeling of the nonlinear cyclic flexural behavior of reinforced concrete members is crucial for the assessment of the seismic response of RC framed structures. To mitigate the problem of damage localization and improve the stability of the numerical model, force beam column elements with fiber cross-section and finite length hinges located at the ends of the member are often used. In this case, the accuracy in the prediction of the cyclic response is strictly dependent on the length assigned to the plastic hinge. In the past, several authors have proposed formulations to evaluate this crucial parameter based on observations and data from laboratory tests. Nevertheless, the values given by these expressions can differ significantly from each other. In this paper, the optimal value for the length of the plastic hinge is calibrated by comparison between laboratory and numerical test results. Laboratory tests are selected to identify mem...
A Simple Hinge Model for Displacement-based Nonlinear Analysis of Reinforced Concrete Columns
Philippine Engineering Journal, 2018
During strong earthquakes, reinforced concrete (RC) structures experience cyclic lateral loads that result to degradation in load-carrying capacity, and failure of columns in shear and/or flexure. This study presents a simple hysteretic hinge model that may be used in displacement-based analysis of RC columns, classified as flexure critical, shear critical, and shear-flexure critical, subjected to cyclic loads. The proposed hinge model made up of zero-length nonlinear springs can simulate the hysteretic behavior of reinforced concrete material in axial, shear, and flexure. The nonlinear parameters of the springs were derived from geometric and material properties of the column and estimated using Response-2000 software. Pushover analysis and response to cyclic loading were performed using the Open System for Earthquake Engineering Simulation (OpenSees) program and validated by comparing the force-displacement response of select forty-three RC columns available in the PEER Structural Performance Database. Results show that for the six rectangular columns, the numerical experiments using the proposed hinge model and the actual force-displacement curves gave R-squared values greater than 0.80 signifying good agreement of results. Therefore, it was concluded that the model can reasonably replicate nonlinear behavior of shear-, shear-flexure, and flexure-critical columns subjected to cyclic loading and, therefore, may be used to assess performance of actual RC columns.
Nonlinear analysis of reinforced concrete slabs through the finite element method
One of the significant difficulties in representing the behavior of reinforced concrete structures in mathematical models is the postcracking non-linearity. And so, reinforced concrete slabs are no exception to the rule. Still, the usual analysis models for this structural element are verified in the elastic regime when the concrete tensile strength is considered. This model is acceptable for the service limit states but not the ultimate limit state. These aspects associated with the great difference in the behavior of concrete when subjected to tension or compression make it necessary to study a nonlinear mathematical model that can represent a reinforced concrete slab subjected to bending, from the beginning of loading until its failure, as accurately as possible. With this, the ANSYS software, from its version 18, made available in its library the Drucker-Prager-Rankine model arranged with two distinct rupture surfaces. A Drucker-Prager criterion for the concrete subjected to compression and a Rankine criterion for concrete in tension. In addition, the software is based on the finite element method, giving the possibility of precise and nonlinear analysis through load and deformation increments, taking into account both elastic and plastic deformations after concrete cracking. Thus, this work aims to present the modeling of reinforced concrete slabs through the Drucker-Prager-Rankine surface, validating the model by comparing it with several experimental tests. The model results were coherent and acceptable, presenting a good approximation of the results of the tests.