scholarly journals An efficient mechanical-probabilistic approach for the collapse modelling of RC structures

2019 ◽  
Vol 12 (2) ◽  
pp. 386-397
Author(s):  
K. O. COELHO ◽  
E. D. LEONEL ◽  
J. FLÓREZ-LÓPEZ
Keyword(s):  
Probabilistic Approach ◽  
Damage Model ◽  
Coupled Model ◽  
Simulation Method ◽  
Computationally Efficient ◽  
Rc Structures ◽  
Realistic Representation ◽  
Probabilistic Context ◽  
Numerical Approaches

Abstract The reinforced concrete (RC) structures are widely utilized around the world. However, the modelling of its complex mechanical behaviour by efficient numerical approaches has been presented marginally in the literature. The efficient approaches enable the accurate and the realistic representation of the mechanical phenomena involved and are computationally efficient for analysing complex structures. In the present study, the improved version of the lumped damage model is coupled to the Monte Carlo simulation method to represent the mechanical-probabilistic behaviour of RC structures. In such model, the concrete cracking and reinforcements’ yield are represented accurately. Moreover, this damage approach enables the accurate modelling of failure scenarios, which are based on the damage variable. Furthermore, this coupled model enables the determination of the collapse modelling accounting for uncertainties, which is the main contribution of the present study. One simple supported RC beam and one 2D RC frame are analysed in the probabilistic context. The accurate results are obtained for the probabilistic collapse path as well as its changes as a function of the loading conditions and material properties uncertainties.

Nonlinear Analysis of RC Structures Using Isotropic Damage Model

2011 ◽  
Vol 21 (5) ◽  
pp. 647-669 ◽  
Author(s):  
Smitha Gopinath ◽  
J. Rajasankar ◽  
N. R. Iyer
Keyword(s):  
Damage Mechanics ◽  
Local Level ◽  
Damage Model ◽  
Coupled Model ◽  
Crack Model ◽  
Element Analysis ◽  
Directional Bias ◽  
Rc Structures ◽  
Isotropic Damage ◽  
As Stress

This article proposes a simple isotropic damage model within damage mechanics framework to represent the behavior of concrete in tension. Macroscopic evolution of tensile crack is considered as damage and is mathematically defined using an exponential function of tensile strain. A damage evolution law is formulated by applying strain equivalence principle to hyperbolic tension-softening curve. Value of damage variable is assumed theoretically to vary between ‘0’ and ‘1’ to denote uncracked and ruptured states, respectively. A smeared rotating crack model is coupled with damage formulation to simulate crack propagation effects in nonlinear finite element analysis of reinforced concrete (RC) structures. Many deficiencies of smeared crack model such as stress locking, mesh-induced directional bias, and instability in response computation for near-ultimate load are overcome using the coupled model. To verify the proposed model, nonlinear static response behavior of a RC beam is computed and compared with experimental and analytical results reported in literature. Effectiveness and applicability of the model to analyze practical structures are proved by analyzing a RC chimney. Nonlinear response of RC chimney is reviewed at global level while damage states of finite elements are studied at local level.

Computationally Efficient and Robust Nonlinear 3D Cyclic Modeling of RC Structures Through a Hybrid Finite Element Model (HYMOD)

2018 ◽  
Vol 16 (01) ◽  
pp. 1850125 ◽  
Author(s):  
George Markou ◽  
Christos Mourlas ◽  
Manolis Papadrakakis
Keyword(s):  
Computational Cost ◽  
Nonlinear Behavior ◽  
Material Model ◽  
Element Model ◽  
Simulation Method ◽  
Full Scale ◽  
Hybrid Modeling ◽  
Computationally Efficient ◽  
Rc Structures ◽  
Rc Frames

A computationally efficient and robust simulation method is presented in this work, for the cyclic modeling of reinforced concrete (RC) structures. The proposed hybrid modeling (HYMOD) approach alleviates numerical limitations regarding the excessive computational cost during the cyclic analysis and provides a tool for the detailed simulation of the 3D cyclic nonlinear behavior of full-scale RC structures. The simplified HYMOD approach is integrated in this work with a computationally efficient cyclic concrete material model so as to investigate its numerical performance under extreme cyclic loading conditions. The proposed approach adopts a hybrid modeling concept that combines hexahedral and beam-column finite elements (FEs), in which the coupling between them is achieved through the implementation of kinematic constraints. A parametric investigation is performed through the use of the Del Toro Rivera frame joint and two RC frames with a shear wall. The proposed modeling method managed to decrease the computational cost in all numerical tests performed in this work, while it induced additional numerical stability during the cyclic analysis, in which the required number of internal iterations per displacement increment was found to be always smaller compared with the unreduced (hexahedral) model. The HYMOD provides for the first time with the required 3D detailed FE solution tools in order to simulate the nonlinear cyclic response of full-scale RC structures without hindering the numerical accuracy of the derived model nor the need of developing computationally expensive models that practically cannot be solved through the use of standard computer systems.

scholarly journals Stiffness Estimation and Equivalence of Boundary Conditions in FEM Models

2021 ◽  
Vol 11 (4) ◽  
pp. 1482
Author(s):  
Róbert Huňady ◽  
Pavol Lengvarský ◽  
Peter Pavelka ◽  
Adam Kaľavský ◽  
Jakub Mlotek
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Boundary Conditions ◽  
Model Updating ◽  
Element Model ◽  
Computational Time ◽  
Stiffness Coefficients ◽  
First Case ◽  
Numerical Approaches

The paper deals with methods of equivalence of boundary conditions in finite element models that are based on finite element model updating technique. The proposed methods are based on the determination of the stiffness parameters in the section plate or region, where the boundary condition or the removed part of the model is replaced by the bushing connector. Two methods for determining its elastic properties are described. In the first case, the stiffness coefficients are determined by a series of static finite element analyses that are used to obtain the response of the removed part to the six basic types of loads. The second method is a combination of experimental and numerical approaches. The natural frequencies obtained by the measurement are used in finite element (FE) optimization, in which the response of the model is tuned by changing the stiffness coefficients of the bushing. Both methods provide a good estimate of the stiffness at the region where the model is replaced by an equivalent boundary condition. This increases the accuracy of the numerical model and also saves computational time and capacity due to element reduction.

Quantification of the Complex Crack Geometry Effect On Fracture Resistance Using Strain Based FE Damage Analysis

2021 ◽  
Author(s):  
Seung-Jae Kim ◽  
Ho-Wan Ryu ◽  
Jin Weon Kim ◽  
Young-Jin Oh ◽  
Yun-Jae Kim
Keyword(s):  
Crack Length ◽  
Surface Crack ◽  
Crack Depth ◽  
Damage Model ◽  
Simulation Method ◽  
Resistance Curve ◽  
Crack Geometry ◽  
Model And Simulation ◽  
Resistance Curves ◽  
Complex Crack

Abstract This paper examines the effect of complex crack geometry on the J-resistance curves obtained by strain-based ductile tearing simulation of complex cracked tension (CC(T)) specimens. The damage model is determined by analyzing the results of a smooth bar tensile test and a C(T) specimen toughness test on an SA508 Gr.1a low-alloy steel at 316 ?. The validity of the damage model and simulation method is checked by comparing the fracture test data for two CC(T) specimen tests. To investigate the effect of the complex crack geometry on the crack growth profiles and J-resistance curves, two geometric parameters (namely, the through-wall crack length and the surface crack depth) are systematically varied. It is found that the J-resistance curves for the CC(T) specimens with various through-wall crack lengths and surface crack depths are consistently lower than the corresponding 1T C(T) J-resistance curves. The effect of the through-wall crack length upon the J-resistance curve is found to be less significant than that of the surface crack depth. Moreover, the J-resistance curve decreases continuously with increasing surface crack depth.

scholarly journals Application of a computationally efficient method to approximate gap model results with a probabilistic approach

2014 ◽  
Vol 7 (1) ◽  
pp. 1535-1600
Author(s):  
M. Scherstjanoi ◽  
J. O. Kaplan ◽  
H. Lischke
Keyword(s):  
Climate Change ◽  
Efficient Method ◽  
Tree Species ◽  
Forest Dynamics ◽  
Probabilistic Approach ◽  
Age Distribution ◽  
Change Scenario ◽  
Model Parameters ◽  
Computationally Efficient ◽  
Tree Species Composition

Abstract. To be able to simulate climate change effects on forest dynamics over the whole of Switzerland, we adapted the second generation DGVM LPJ-GUESS to the Alpine environment. We modified model functions, tuned model parameters, and implemented new tree species to represent the potential natural vegetation of Alpine landscapes. Furthermore, we increased the computational efficiency of the model to enable area-covering simulations in a fine resolution (1 km) sufficient for the complex topography of the Alps, which resulted in more than 32 000 simulation grid cells. To this aim, we applied the recently developed method GAPPARD (Scherstjanoi et al., 2013) to LPJ-GUESS. GAPPARD derives mean output values from a combination of simulation runs without disturbances and a patch age distribution defined by the disturbance frequency. With this computationally efficient method, that increased the model's speed by approximately the factor 8, we were able to faster detect shortcomings of LPJ-GUESS functions and parameters. We used the adapted LPJ-GUESS together with GAPPARD to assess the influence of one climate change scenario on dynamics of tree species composition and biomass throughout the 21st century in Switzerland. To allow for comparison with the original model, we additionally simulated forest dynamics along a north-south-transect through Switzerland. The results from this transect confirmed the high value of the GAPPARD method despite some limitations towards extreme climatic events. It allowed for the first time to obtain area-wide, detailed high resolution LPJ-GUESS simulation results for a large part of the Alpine region.

scholarly journals Multi-city modeling of epidemics using spatial networks: Application to 2019-nCov (COVID-19) coronavirus in India

2020 ◽  
Author(s):  
Bhalchandra S. Pujari ◽  
Snehal Shekatkar
Keyword(s):  
Hybrid Approach ◽  
Coarse Grained ◽  
Spatial Networks ◽  
Computationally Efficient ◽  
Transport Networks ◽  
Epidemiological Modeling ◽  
Fine Grained ◽  
City Modeling ◽  
Coupling Parameters

The ongoing pandemic of 2019-nCov (COVID-19) coronavirus has made reliable epidemiological modeling an urgent necessity. Unfortunately, most of the existing models are either too fine-grained to be efficient or too coarse-grained to be reliable. Here we propose a computationally efficient hybrid approach that uses SIR model for individual cities which are in turn coupled via empirical transportation networks that facilitate migration among them. The treatment presented here differs from existing models in two crucial ways: first, self-consistent determination of coupling parameters so as to maintain the populations of individual cities, and second, the incorporation of distance dependent temporal delays in migration. We apply our model to Indian aviation as well as railway networks taking into account populations of more than 300 cities. Our results project that through the domestic transportation, the significant population is poised to be exposed within 90 days of the onset of epidemic. Thus, serious supervision of domestic transport networks is warranted even after restricting international migration.

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