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Computers and Concrete
  Volume 34, Number 3, September 2024 , pages 307-328
DOI: https://doi.org/10.12989/cac.2024.34.3.307
 


Unified modelling approach with concrete damage plasticity model for reliable numerical simulation: A study on thick flat plates under eccentric loads
Mohamed H. El-Naqeeb and Reza Hassanli

 
Abstract
    The concrete damage plasticity (CDP) model is widely used to simulate concrete behaviour using either implicit or explicit analysis methods. To effectively execute the models and resolve convergence issues in implicit analysis, activating the viscosity parameter of this material model is a common practice. Despite the frequent application of implicit analysis to analyse concrete structures with the CDP model, the viscosity parameter significantly varies among available models and lacks consistency. The adjustment of the viscosity parameter at the element/structural level disregards its indirect impact on the material. Therefore, the accuracy of the numerical model is confined to the validated range and might not hold true for other values, often explored in parametric studies subsequent to validations. To address these challenges and develop a unified numerical model for varied conditions, a quasi-static analysis using the explicit solver was conducted in this study. Fifteen thick flat plates tested under load control with different geometries and different eccentric loads were considered to verify the accuracy of the model. The study first investigated various concrete material behaviours under compression and tension as well as the concrete tensile strength to identify the most reliable models from previous methodologies. The study compared the results using both implicit and explicit analysis. It was found that, in implicit analysis, the viscosity parameter should be as low as 0.0001 to avoid affecting material properties. However, at the structural level, the optimum value may need adjustment between 0.00001 to 0.0001 with changing geometries and loading type. This observation raises concerns about further parametric study if the specific value of the viscosity parameter is used. Additionally, activating the viscosity parameter in load control simulations confirmed its inability to capture the peak load. Conversely, the unified explicit model accurately simulated the behaviour of the test specimens under varying geometries, load eccentricities, and column sizes. This study recommends restricting implicit solutions to the viscosity values proposed in this research. Alternatively, for highly nonlinear problems under load control simulation, explicit analysis stands as an effective approach, ensuring unified parameters across a wide range of applications without convergence problems.
 
Key Words
    CDP model; eccentric loads; explicit analysis; numerical modelling; punching shear; thick slabs; viscosity parameter
 
Address
Mohamed H. El-Naqeeb: 1) Badr University in Cairo, School of Engineering and Technology, Cairo 11829, Egypt, 2) University of South Australia, UniSA STEM, Mawson Lakes, SA 5095, Australia
Reza Hassanli: University of South Australia, UniSA STEM, Mawson Lakes, SA 5095, Australia
 

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