Presents a computational algorithm for the numerical integration of triaxial concrete plasticity formulations. The specific material formulation at hand is the so‐called extended…
Abstract
Presents a computational algorithm for the numerical integration of triaxial concrete plasticity formulations. The specific material formulation at hand is the so‐called extended leon model for concrete. It is based on the flow theory of plasticity which entails isotropic hardening as well as fracture energy‐based softening in addition to non‐associated plastic flow. The numerical algorithm resorts to implicit integration according to the backward Euler strategy that enforces plastic consistency according to the closes‐point‐projection method (generalized radial‐return strategy). Numerical simulations illustrate the overall performance of the proposed algorithm and the significant increase of the convergence rate when the algorithmic tangent is used in place of the continuum operator.
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Peter Pivonka and Kaspar Willam
In this paper, we examine the influence of the third invariant in computational plasticity. For this purpose we consider the extended Leon model, an elasto‐plastic model for…
Abstract
In this paper, we examine the influence of the third invariant in computational plasticity. For this purpose we consider the extended Leon model, an elasto‐plastic model for concrete materials which accounts for the difference of shear strength in triaxial compression and triaxial extension. Consequently, the deviatoric trace of the loading surface is no longer circular like in von Mises and Drucker‐Prager plasticity. In the limit it approaches the triangular shape of the Rankine condition of maximum direct stress. Thereby, elliptic functions describe the out‐of‐roundness of the circular trace in terms of C1‐continuous functions of the Lode angle. The algorithmic aspects of the third invariant considerably complicate the computational implementation since the radial return method of J2‐plasticity does no longer maintain normality leading to loss of deviatoric associativity. The paper will focus on the computational issues near the three regions with high curvature at the compressive meridians with special attention on the lack of convergence of the plastic return algorithm and its slow rate of convergence in these regions. The algorithmic discussion at the constitutive level will be augmented by the axial plane‐strain compression test in order to illustrate the effect of the third invariant at the structural level of finite element analysis.
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Rabah Hammoud, Rachid Boukhili and Ammar Yahia
A numerical model to simulate the impact of high temperature on the behavior of conventional concrete under chemoplastic framework is developed and validated. The model is based…
Abstract
A numerical model to simulate the impact of high temperature on the behavior of conventional concrete under chemoplastic framework is developed and validated. The model is based on new formulation of a constitutive law with new chemoplastic potential. By overlaying the chemoplastic potential on the modified Etse and Willam yielding surface, both defined on the Haigh-Westergaard coordinates, it was found that the two curves do not undergo similar stress state at the same strength parameter. For an adequate evaluation of normal vectors, each surface is forced to pass through the current stress state. Keeping the loading surface unchanged, the calculation of the plastic potential need to be modified. The proposed constitutive model is validated by comparing predicted and experimental data. The model is shown to be accurate to predict different stress states of concrete under different temperature levels.
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Ana Clara Berndt, Giancarlo Gomes, Felipe Mendes Borini and Roberto Carlos Bernardes
This study aims to analyze the organizational learning capability relationship with operational performance and frugal innovation across Brazilian companies.
Abstract
Purpose
This study aims to analyze the organizational learning capability relationship with operational performance and frugal innovation across Brazilian companies.
Design/methodology/approach
Quantitative research was performed using collected data from 154 firms, which were analyzed using structural equation modeling.
Findings
The results showed that organizational learning capability is an antecedent of frugal innovation. The results also predict a better operational performance for companies that actively innovate cost-effectively. Another result was the positive relationship between the organizational learning capability and the operational performance. The authors found that the indirect and positive relationship between organizational learning capability, frugal innovation and operational performance was confirmed, reinforcing the literature.
Research limitations/implications
A theoretical implication of this study can be seen in the establishment of the relationship between organizational learning capability, frugal innovation and operational performance since no studies linking these variables together were found. Therefore, the organizational learning capability and the frugal innovation can be considered facilitators of the operational performance.
Practical implications
Managers should consider organizational learning and frugal innovation when thinking about firms’ operational performance. In this way, to facilitate and achieve higher performance, it was found that organizational learning capability and frugal innovation have a great deal of impact on operational performance.
Social implications
At frugal innovation, the needs of citizens are prioritized. It is a great instrument to face crises since it consists of developing simpler and cheaper products and services quickly, making them accessible to a larger group of consumers.
Originality/value
This study seeks to understand whether Brazilian companies are moving toward a more frugal innovation strategy. The study opens the possibility of showing whether the organizational learning capability has also impacted this change.
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Divyanshu Kumar Lal and Arghya Das
Semi-implicit type cutting plane method (CPM) and fully implicit type closest point projection method (CPPM) are the two most widely used frameworks for numerical stress…
Abstract
Purpose
Semi-implicit type cutting plane method (CPM) and fully implicit type closest point projection method (CPPM) are the two most widely used frameworks for numerical stress integration. CPM is simple, easy to implement and accurate up to first order. CPPM is unconditionally stable and accurate up to second order though the formulation is complex. Therefore, this study aims to develop a less complex and accurate stress integration method for complex constitutive models.
Design/methodology/approach
Two integration techniques are formulated using the midpoint and Romberg method by modifying CPM. The algorithms are implemented for three different classes of soil constitutive model. The efficiency of the algorithms is judged via stress point analysis and solving a boundary value problem.
Findings
Stress point analysis indicates that the proposed algorithms are stable even with a large step size. In addition, numerical analysis for solving boundary value problem demonstrates a significant reduction in central processing unit (CPU) time with the use of the semi-implicit-type midpoint algorithm.
Originality/value
Traditionally, midpoint and Romberg algorithms are formulated from explicit integration techniques, whereas the present study uses a semi-implicit approach to enhance stability. In addition, the proposed stress integration algorithms provide an efficient means to solve boundary value problems pertaining to geotechnical engineering.
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Angel Rawat, Raghu Piska, A. Rajagopal and Mokarram Hossain
This paper aims to present a nonlocal gradient plasticity damage model to demonstrate the crack pattern of a body, in an elastic and plastic state, in terms of damage law. The…
Abstract
Purpose
This paper aims to present a nonlocal gradient plasticity damage model to demonstrate the crack pattern of a body, in an elastic and plastic state, in terms of damage law. The main objective of this paper is to reconsider the nonlocal theory by including the material in-homogeneity caused by damage and plasticity. The nonlocal nature of the strain field provides a regularization to overcome the analytical and computational problems induced by softening constitutive laws. Such an approach requires C1 continuous approximation. This is achieved by using an isogeometric approximation (IGA). Numerical examples in one and two dimensions are presented.
Design/methodology/approach
In this work, the authors propose a nonlocal elastic plastic damage model. The nonlocal nature of the strain field provides a regularization to overcome the analytical and computational problems induced by softening constitutive laws. An additive decomposition of strains in to elastic and inelastic or plastic part is considered. To obtain stable damage, a higher gradient order is considered for an integral equation, which is obtained by the Taylor series expansion of the local inelastic strain around the point under consideration. The higher-order continuity of nonuniform rational B-splines (NURBS) functions used in isogeometric analysis are adopted here to implement in a numerical scheme. To demonstrate the validity of the proposed model, numerical examples in one and two dimensions are presented.
Findings
The proposed nonlocal elastic plastic damage model is able to predict the damage in an accurate manner. The numerical results are mesh independent. The nonlocal terms add a regularization to the model especially for strain softening type of materials. The consideration of nonlocality in inelastic strains is more meaningful to the physics of damage. The use of IGA framework and NURBS basis functions add to the nonlocal nature in approximations of the field variables.
Research limitations/implications
The method can be extended to 3D. The model does not consider the effect of temperature and the dissipation of energy due to temperature. The method needs to be implemented for more real practical problems and compare with experimental work. This is an ongoing work.
Practical implications
The nonlocal models are suitable for predicting damage in quasi brittle materials. The use of elastic plastic theories allows to capture the inelastic deformations more accurately.
Social implications
The nonlocal models are suitable for predicting damage in quasi brittle materials. The use of elastic plastic theories allows to capture the inelastic deformations more accurately.
Originality/value
The present work includes the formulation and implementation of a nonlocal damage plasticity model using an isogeometric discretization, which is the novel contribution of this paper. An implicit gradient enhancement is considered to the inelastic strain. During inelastic deformations, the proposed strain tensor partitioning allows the use of a distinct potential surface and distinct failure criterion for both damage and plasticity models. The use of NURBS basis functions adds to more nonlocality in the approximation.
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Mirela Galic, Pavao Marovic and Zeljana Nikolic
The main aim of this paper is to present a three‐dimensional numerical material model for concrete which combines plasticity with a classical orthotropic smeared crack…
Abstract
Purpose
The main aim of this paper is to present a three‐dimensional numerical material model for concrete which combines plasticity with a classical orthotropic smeared crack formulation. A further aim is to raise a discussion leading to the creation of a comprehensive computer programme for the analyses of reinforced and prestressed concrete structures.
Design/methodology/approach
A new numerical material model for concrete is developed and main theoretical explanations are given to aid in understanding the algorithm. The model is based on Mohr‐Coulomb criterion for dominant compression and Rankine criterion for dominant tension influences. A multi‐surface presentation of the model is implemented which permits the rapid convergence of the mathematical procedure. The model includes associated and non‐associated flow rules, strain hardening and softening where the development of the plastic strain was described by the function of cohesion.
Findings
Provides information about developing a new numerical material model for concrete.
Practical implications
The model is implemented into the computer programme PRECON3D for the three‐dimensional nonlinear analysis of the reinforced and prestressed concrete structures.
Originality/value
In this model, the very complex behaviour of concrete is defined by elementary material parameters which can be obtained by a standard uniaxial test. The presented model enables a very detailed and precise analysis of reinforced and prestressed concrete structures until crushing with a high accuracy, so that the expensive experimental tests can be reduced. The paper could be very valuable to researchers in this field as a benchmark for their analyses.
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Javier Luis Mroginski, Pablo Alejandro Beneyto, Guillermo J Gutierrez and Ariel Di Rado
There are many problems in civil or mechanical engineering related to structural design. In such a case, the solution techniques which lead to deterministic results are no longer…
Abstract
Purpose
There are many problems in civil or mechanical engineering related to structural design. In such a case, the solution techniques which lead to deterministic results are no longer valid due to the heuristic nature of design problems. The purpose of this paper is to propose a computational tool based on genetic algorithms, applied to the optimal design of cross-sections (solid tubes) of 3D truss structures.
Design/methodology/approach
The main feature of this genetic algorithm approach is the introduction of a selective-smart method developed in order to improve the convergence rate of large optimization problems. This selective genetic algorithm is based on a preliminary sensitivity analysis performed over each variable, in order to reduce the search space of the evolutionary process. In order to account for the optimization of the total weight, the displacement (of a specific section) and the internal stresses distribution of the structure a multiobjective optimization function was proposed.
Findings
The numerical results presented in this paper show a significant improvement in the convergence rate as well as an important reduction in the relative error, compared to the exact solution.
Originality/value
The variables sensitivity analysis put forward in this approach introduces a significant improvement in the convergence rate of the genetic algorithm proposed in this paper.
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Marzlin Marzuki, Nava Subramaniam, Barry J. Cooper and Steven Dellaportas
The purpose of this paper is to examine the extent to which ethics education is incorporated in the curriculum by accounting academics (EXTENT) and its relationship with the…
Abstract
Purpose
The purpose of this paper is to examine the extent to which ethics education is incorporated in the curriculum by accounting academics (EXTENT) and its relationship with the following four factors: accounting academics’ attitudes towards ethics education (ATTDE); head of department support (HODS); peer support (PEERS); and accounting academics’ ethics teaching self-efficacy (ETSE).
Design/methodology/approach
The study utilises data from a questionnaire survey of 117 accounting academics in Malaysia and engages path analysis to test various hypothesised relationships.
Findings
The results indicate that ATTDE, HODS and PEERS have a significant and positive impact on accounting academics’ ETSE. The findings also suggest that ETSE and PEERS have a direct and positive impact on EXTENT. Overall, ETSE is found to be a significant mediating variable in the relationship between ATTDE, HODS, PEERS and EXTENT.
Research limitations/implications
The relatively small sample of 117 Malaysian accounting academics and the limited number of factors studied as drivers of ETSE, which limits generalisability of the results.
Practical implications
This paper is particularly useful for informing heads of departments and the regulatory and professional bodies of resourcing and fostering a work environment that supports peer support and interactions as well as knowledge resources that facilitate individual accounting academics’ to integrate ethics content in their courses or units.
Originality/value
The study is guided by Bandura’s (1977, 1997) self-efficacy theory and adapts Tschannen-Moran and Hoy’s (2001) teacher efficacy construct in understanding how accounting academic’s belief in one’s ability to complete tasks and achieve goals affects the level of integration of ethics in their courses.
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A lot of triaxial compressive models for different concrete types and different concrete strength classes were proposed to be used in structural analyses. The existence of so many…
Abstract
Purpose
A lot of triaxial compressive models for different concrete types and different concrete strength classes were proposed to be used in structural analyses. The existence of so many models creates conflicts and confusions during the selection of the models. In this study, reliability analyses were carried out to prevent such conflicts and confusions and to determine the most reliable model for normal- and high-strength concrete (NSC and HSC) under combined triaxial compressions. The paper aims to discuss these issues.
Design/methodology/approach
An analytical model was proposed to estimate the strength of NSC and HSC under different triaxial loadings. After verifying the validity of the model by making comparisons with the models in the literature, reliabilities of all models were investigated. The Monte Carlo simulation method was used in the reliability studies. Artificial experimental data required for the Monte Carlo simulation method were generated by using artificial neural networks.
Findings
The validity of the proposed model was verified. Reliability indexes of triaxial compressive models were obtained for the limit states, different concrete strengths and different lateral compressions. Finally, the reliability indexes were tabulated to be able to choose the best model for NSC and HSC under different triaxial compressions.
Research limitations/implications
Concrete compressive strength and lateral compression were taken as variables in the model.
Practical implications
The reliability indexes were tabulated to be able to choose the best model for NSC and HSC under different triaxial compressions.
Originality/value
A new analytical model was proposed to estimate the strength of NSC and HSC under different triaxial loadings. Reliability indexes of triaxial compressive models were obtained for the limit states, different concrete strengths and different lateral compressions. Artificial experimental data were obtained by using artificial neural networks. Four different artificial neural networks were developed to generate artificial experimental data. They can also be used in the estimations of the strength of NSC and HSC under different triaxial loadings.