Publication Date: 2022
Journal of Anatomy (14697580)240(2)pp. 305-322
Statistical data pertaining to anatomic variations of the human talus contain valuable information for advances in biological anthropology, diagnosis of the talar pathologies, and designing talar prostheses. A statistical shape model (SSM) can be a powerful data analysis tool for the anatomic variations of the talus. The main concern in constructing an SSM for the talus is establishing the true geometric correspondence between the talar geometries. The true correspondence complies with biological and/or mathematical homologies on the talar surfaces. In this study, we proposed a semi-automatic approach to establish a dense correspondence between talar surfaces discretized by triangular meshes. Through our approach, homologous salient surface features in the form of crest lines were detected on 49 talar surfaces. Then, the point-wise correspondence information of the crest lines was recruited to create posterior Gaussian process morphable models that non-rigidly registered the talar meshes and consequently established inter-mesh dense correspondence. The resultant correspondence perceptually represented the true correspondence as per our visual assessments. Having established the correspondence, we computed the mean shape using full generalized Procrustes analysis and constructed an SSM by means of principal component analysis. Anatomical variations and the mean shape of the talus were predicted by the SSM. As a clinically related application, we considered the mean shape and investigated the feasibility of designing universal talar prostheses. Our results suggest that the mean shape of (the shapes of) tali can be used as a scalable shape template for designing universal talar prostheses. © 2021 Anatomical Society
Publication Date: 2015
Multidiscipline Modeling in Materials and Structures (15736105)11(2)pp. 186-201
Purpose - The interest in the ability to detect damage at the earliest possible stage is pervasive throughout the civil engineering over the last two decades. In general, the experimental techniques for damage detection are expensive and require that the vicinity of the damage is known and readily accessible; therefore several methods intend to detect damage based on numerical model and by means of minimum experimental data about dynamic properties or response of damaged structures. The paper aims to discuss these issues. Design/methodology/approach - In this paper, the damage detection problem is formulated as an optimization problem such as to obtain the minimum difference between the numerical and experimental variables, and then a modified ant colony optimization (ACO) algorithm is proposed for solving this optimization problem. In the proposed algorithm, the structural damage is detected by using dynamically measured flexibility matrix, since the flexibility matrix of the structure can be estimated from only the first few modes. The continuous version of ACO is employed as a probabilistic technique for solving this computational problem. Findings - Compared to classical methods, one of the main strengths of this meta-heuristic method is the generally better robustness in achieving global optimum. The efficiency of the proposed algorithm is illustrated by numerical examples. The proposed method enables the deduction of the extent and location of structural damage, while using short computational time and resulting good accuracy. Originality/value - Finding accurate results by means of minimum experimental data, while using short computational time is the final goal of all researches in the structural damage detection methods. In this paper, it gains by applying flexibility matrix in the definition of objective function, and also via using continuous ant colony algorithm as a powerful meta-heuristic techniques in the constrained nonlinear optimization problem. © Emerald Group Publishing Limited.
Publication Date: 2017
Journal of Power Sources (0378-7753)350pp. 127-139
It is well known that phase separation could severely intensify mechanical degradation and expedite capacity fading in lithium-ion battery electrodes during electrochemical cycling. Experiments have frequently revealed that such degradation effects could be substantially mitigated via reducing the electrode feature size to the nanoscale. The purpose of this work is to present a fracture mechanics study of the phase separating planar electrodes. To this end, a phase field model is utilized to predict how phase separation affects evolution of the solute distribution and stress profile in a planar electrode. Behavior of the preexisting flaws in the electrode in response to the diffusion induced stresses is then examined via computing the time dependent stress intensity factor arising at the tip of flaws during both the insertion and extraction half-cycles. Further, adopting a sharp-interphase approximation of the system, a critical electrode thickness is derived below which the phase separating electrode becomes flaw tolerant. Numerical results of the phase field model are also compared against analytical predictions of the sharp-interphase model. The results are further discussed with reference to the available experiments in the literature. Finally, some of the limitations of the model are cautioned. © 2017 Elsevier B.V.
Publication Date: 2015
Mechanics of Advanced Materials and Structures (15210596)22(8)pp. 655-669
A semi-analytical fully discretized finite strip method is developed to investigate the pre-buckling and local buckling of viscoelastic plates with different boundary conditions subjected to time-dependent loading. The mechanical properties of the material are considered to be linear viscoelastic by expressing the relaxation modulus in terms of Prony series. The fully discretized finite strip equations are developed using a two-point recurrence formulation, which leads to a computationally superior formulation. Time history of maximum deflection of plates with different end conditions is calculated. The effects of thickness, length of plate, and transverse loading on critical buckling load are also studied. Copyright © 2015 Taylor & Francis Group, LLC.
Publication Date: 2020
International Journal of Steel Structures (20936311)20(5)pp. 1465-1481
On the structural analysis, connection effects should be evaluated in terms of rotational stiffness and ultimate strength; this makes it possible to obtain realistic behavior of the structure. In this research, a simple analytical evaluation is carried out to predict the behaviors of the connections as a bi-linear curve. Mechanical properties of the initial and the second parts of this curve are obtained by component-based method and a suggested classification method, respectively. The component-based method represents a joint by using a combination of rigid and flexible components. Each of the components is modeled by means of specific stiffness and strength values and they are assembled together to obtain the initial mechanical properties of the joint. The suggested classification method classifies all the components in a connection into three groups based on comparing the ultimate and the design moment strength of each component with those of the connection. By considering this procedure, a new equation is proposed to determine joint post-limit rotational stiffness. This simple and fast method is applicable to any type of joints regardless of profile type and applied loading. The proposed method is applied to a bolted angle, an end-plate to rectangular hollow section column and two bolted end-plate beam-to-column connections. The results are compared with those obtained from some other analytical, numerical and experimental methods. The outputs confirm that the proposed method is simpler, more accurate and less time consume than the other methods. © 2020, Korean Society of Steel Construction.
Publication Date: 2024
Water Science and Technology (2731223)(7)pp. 1741-1756
Wastewater treatment plants (WWTPs) have positive and negative impacts on the environment. Therefore, life cycle impact assessment (LCIA) can provide a more holistic framework for performance evaluation than the conventional approach. This study added water footprint (WF) to LCIA and defined ϕ index for accounting for the damage ratio of carbon footprint (CF) to WF. The application of these innovations was verified by comparing the performance of 26 WWTPs. These facilities are located in four different climates in Iran, serve between 1,900 and 980,000 people, and have treatment units like activated sludge, aerated lagoon, and stabilization pond. Here, grey water footprint (GWF) calculated the ecological impacts through typical pollutants. Blue water footprint (BWF) included the productive impacts of wastewater reuse, and CF estimated CO2 emissions from WWTPs. Results showed that GWF was the leading factor. ϕ was 4–7.5% and the average WF of WWTPs was 0.6 m3/ca, which reduced 84%, to 0.1 m3/ca, through wastewater reuse. Here, wastewater treatment and reuse in larger WWTPs, particularly with activated sludge had lower cumulative impacts. Since this method takes more items than the conventional approach, it is recommended for integrated evaluation of WWTPs, mainly in areas where the water–energy nexus is a paradigm for sustainable development. © 2024 IWA Publishing. All rights reserved.
Publication Date: 2025
Structures (23520124)81
There are countless valuable historical monuments in Iran, whose restoration and protection are critical. Nevertheless, ignorance of the mechanical behavior of Persian adobes has jeopardized their survival. This research aims to understand the mechanical properties of historical and new Persian adobes through DTS/ITS and modulus of elasticity in tension. To this end, six groups of adobes produced in various time periods were initially collected from historical places in different parts of Iran and adobe production workshops. After preparing specimens from existing adobe materials, several mechanical strength tests, including flexural strength, splitting tensile strength (STS), and DST were conducted according to international standards. The mechanical properties and behavior of the Persian adobes were determined by analyzing the results of the experiments. Load-deflection curves obtained from flexural strength tests and stress–strain curves, stress–strain relations and normalized stress–strain relations obtained from DST test were also presented as another part of the results. Moreover, the relationships between mechanical properties were determined with high accuracy using laboratory data. The results of this research will help engineers and researchers take an effective step toward the international standardization of materials and construction related to adobe and earthen materials through perceiving the mechanical properties and developing knowledge of behavior of Persian adobes. Based on the results, new adobes exhibit higher resistance than their historical counterparts, whose mechanical strengths can be converted to each other with amplification or reduction factors. Therefore, researchers will be able to perform only one type of test to obtain mechanical strengths. Finally, a comparison was drawn between the mechanical properties of Persian adobes and those made in other countries, indicating that adobes around the world possess convergent and similar tensile behaviors. © 2025 Institution of Structural Engineers. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Shojaei a., A.,
Mossaiby, F.,
Zaccariotto, M.,
Galvanetto, U. Publication Date: 2019
Computer Methods in Applied Mechanics and Engineering (00457825)356pp. 629-651
This paper introduces an effective way to equip the standard finite element method (FEM) for the solution of transient scalar wave propagation problems in unbounded domains. Similar to many other methods, we truncate the unbounded domain at an artificial boundary and convert the problem into a bounded one by prescribing appropriate absorbing boundary conditions (ABCs) at the truncating boundary. In the present method, the ABCs are time-dependent, and they are constructed by a simple collocation approach which is local in space and time. Therefore, the method does not make use of any routine schemes such as Fourier and Laplace transform. We shall show that the method is simple, and it can be easily applied to an explicit time domain FEM approach so that the sparsity of the FEM scheme (as well as its efficiency) can be preserved. The proposed method does not require any auxiliary variables as well as any approximating differential operators. This feature roots from the fact that here the ABCs are Dirichlet-type (or first-type) and thus they can be easily imposed to the corresponding boundaries. Therefore, the method shares some similarities with the conventional 1st and 2nd order ABC methods in terms of the simplicity of implementation. The method employs basis functions that exactly satisfy the governing and dispersion wave equations. The basis function can be easily adjusted to act as outgoing waves transmitting energy from the interior domain (near field) towards exterior domain (far field); i.e, they can cope with satisfaction of radiation boundary conditions. Several numerical examples are presented to evaluate the performance and to demonstrate the effectiveness of the approach. We shall show that the present method is capable of yielding results with a proper level of accuracy, similar to that of the perfectly matched layers method (PMLs), and it performs stably even in the case of long-term computations. © 2019 Elsevier B.V.
Publication Date: 2022
Computers and Mathematics with Applications (08981221)124pp. 163-187
Transient nonlinear problems play an important role in many engineering problems. Phase-field equations, including the well-known Allen-Cahn and Cahn-Hilliard equations, fall in this category, and have applications in cutting-edge technologies such as modeling the diffusion of lithium (Li) ions in two-phase electrode particles of Li-ion batteries. In this paper, a local meshless method for solving this category of partial differential equations (PDEs) is proposed. The Newton-Kantorovich scheme is employed to transform the nonlinear PDEs to an iterative series of linear ones which can be solved with the proposed method. The accuracy and performance of the method are examined in various linear and nonlinear problems, such as Laplace equation, three dimensional elasticity as well as some abstract mathematical equations with linear or nonlinear boundary conditions. The main focus of the work is on applying the proposed method in solution of the phase-field equations, including the Allen-Cahn and Cahn-Hilliard equations. In addition to homogeneous Neumann boundary condition which has been widely examined in the literature, we also employ a practical nonlinear, inhomogeneous Neumann boundary condition formulation specialized for modeling the diffusion of lithium ions in electrode particles of Li-ion batteries. The generalized-α method is used for time integration of diffusion-type equations to overcome the intrinsic stiffness of the phase-field equations. It is shown that the method is capable of capturing the main features of the phase-field models i.e. phase separation, coarsening and energy decay in closed systems. © 2022 Elsevier Ltd
Publication Date: 2014
Computational Mechanics (14320924)53(6)pp. 1355-1374
This paper introduces a novel meshless method based on the local use of exponential basis functions (EBFs). The EBFs are found so that they satisfy the governing equations within a series of subdomains. The compatibility between the subdomains is weakly satisfied through the minimization of a suitable norm written for the residuals of the continuity conditions. The residual norm may contain any desirable order of continuity. This allows increasing the continuity of the solution without increasing the type of point-wise variables at each node. The solution procedure begins with the discretization of the solution domain into a set of nodal points and cloud construction on each nodal point. The approximate solution in the local coordinates of each cloud is constructed by a series of EBFs. A set of intermediate points are distributed throughout the domain and its boundary to apply the continuity between the local solutions of the adjacent clouds up to a desired order, and also to impose the boundary conditions. The main nodes may play the role of the intermediate points as well. The validity of the results is shown through some patch tests. Also some numerical examples are solved to illustrate the capabilities of the method. High convergence rate of the numerical results is one of the salient features of the proposed meshless method. © 2014 Springer-Verlag Berlin Heidelberg.
Publication Date: 2019
Journal of the Mechanics and Physics of Solids (00225096)133
Defect formation has been widely observed to occur in phase transforming intercalation materials of critical importance to many technological applications. In this work, relying on energy balance argument, we develop a planar particle model to investigate critical conditions for spontaneous dislocation formation in a single-crystalline phase transforming material. Dislocations self-energy is calculated assuming isotropic elasticity, and the work done by the background stress field during dislocation formation is examined based on bilayer and core-shell models of solute distribution. Considering well-known slip systems in cubic crystals, critical sizes are derived, as a function of transformation strain, below which dislocation formation is predicted to remain energetically suppressed throughout complete phase transformation, resulting in completely coherent phase transformation. Effect of the surface flux on the critical size is also examined using a moving interphase model. Minimum dislocation spacing is derived for an array of dislocations which could spontaneously form at the phase boundary when particle size exceeds the critical size. Numerical estimates of the critical size are presented for several materials systems, and the results are discussed with reference to the available experiments. Results of this work could have potentially important implications in terms of designing phase changing materials resistant against cyclic damage. © 2019
Publication Date: 2023
Journal of the Mechanics and Physics of Solids (00225096)174
Point defect distribution in the vicinity of discontinuities plays important role in the transport properties of nonstoichiometric ionic solids. Here, considering dopants and oxygen vacancies as the major point defects in doped ceria, we develop a Monte Carlo model to examine how the stress field of edge dislocations affect point defect distribution in their surroundings. Point defects are considered to interact with the elastic stress field of dislocations due to their misfit volume, and the electrostatic interaction between the point defects is also taken into account. In contrast with a prevalent theory of chemo-mechanical equilibrium in solid solutions, the model developed here is consistent with classical elasticity in that the point defects do not interact through their self-stress fields. Stress effects both on the defect distribution, and on the electric potential, are examined for a single dislocation as well as a periodic array of like dislocations. In agreement with previous atomistic simulations, the model predicts that electrostatic interactions drive enrichment or depletion of defects of both types on either the compressive or tensile side of edge dislocations depending on the ionic radius of the dopant. The stress field of an array of like dislocations periodic in the direction of the Burgers vector is shown to result in different bulk defect concentrations and bulk electric potentials on the opposite sides of the array, whereas for an array with repeat direction normal to the Burgers vector, defect enrichment and depletion emerge in alternate regions limited to the vicinity of the dislocations. © 2023 Elsevier Ltd
Publication Date: 2023
Agricultural Water Management (18732283)282
Grey water footprint (GWF) is one component of water footprint (WF). It considers multiple pollutants and water quality regulations when determining the amount of freshwater required to assimilate the pollution load discharged by agricultural production into the receiving water body. This indicator is typically estimated for accounting the WF of agricultural productions including paddy rice. This study evaluates the GWF of irrigated paddy rice (IPR) through sampling multiple pollutants in both the inflow and drainage of a pilot area, simultaneously. It aims to find a realistic range for the GWF of IPR and emphasize the impacts of pollutants, regulations (Cmax), and inflow (Qin) variations. For this purpose, an isolated subsurface drained farm in northern Iran was chosen as a pilot area where 32 samples from inflow and outflow were taken during the cultivation period (94 days). Here, the concentrations of electro-conductivity (EC), dissolved oxygen (DO), chemical oxidation demand (COD), nitrate (NO3), total kjeldahl nitrogen (TKN), total phosphorous (TP), total nitrogen (TN), and butachlor herbicide, as well as irrigation and drainage volume were investigated. Cmax was examined through three regulation scenarios: strict (S1), normal (S2), and lenient (S3). In addition, Qin was measured by the methods of water balance and SCD-USDA. Results show that TP was most critical in paddy rice GWF (S1-S2), while DO can be an alternative critical parameter in S3. Based on calculations, GWF was ultimately varied between 1109 and 8079 m3/ton in all scenarios. It incorporated a significant share in WF as its ratio varied between 46% and 86%. Cmax showed relatively higher impacts on GWF comparing with the precise calculation of Qin. Moreover, calculating the net pollution loads of multiple pollutants discharged from paddy field was recommended for higher accuracy. As a result, a range for GWF is introduced instead of an absolute value that can be updated by further case studies. © 2023 The Authors
Publication Date: 2016
Canadian Journal of Civil Engineering (03151468)43(12)pp. 1034-1043
This study presents a methodology that utilizes a new combination of two compressed damage indices as input data of an artificial neural network (ANN) ensemble to detect multi-damages in the braces of cold formed steel shear walls. To identify an efficient input data for ANN, first, three main groups of damage indices are considered: modal parameter-based damage indices; frequency response functions (FRFs)-based damage indices and time series-based damage indices. Furthermore, principal component analysis (PCA) technique is applied to reduce the dimensions of FRFs and time series-based input pattern. By a sensitivity study, two suitable damage indices of PCA-compressed time series data and PCA-compressed FRFs are identified and then combined to produce a new efficient input data for a hierarchy of ANN ensembles. The numerical results show that the ANN ensemble-based damage detection approach with the proposed collection of two damage indices is effective and reliable. © 2016, Canadian Science Publishing. All rights reserved.
Publication Date: 2018
International Journal Of Civil Engineering (17350522)16(6)pp. 671-680
This study introduces a mathematical model to represent the hysteresis behavior of structural systems. Compared with some of the analytical models currently in use, this model (which considers different structural phenomena, including pinching, stiffness degradation, strength deterioration, and sliding) yields more precise responses. This model is based on Mostaghel’s well-known model, although some essential modifications and sliding effects are also considered. The model is developed based on a simple single-degree-of-freedom multi-linear mechanical system and on the development of partial differential equations. The proposed model includes the basic characteristics of the hysteresis cycles that can be easily measured through experimental tests. To demonstrate the degrading phenomena of the hysteresis behavior of the structures, several examples of different actual structural systems are presented, to show that the proposed analytical model can provide realistic descriptions of the structural hysteretic performances. In addition, comparisons between the outputs of this model and some hysteretic curves of other models are presented to show the high capability and accuracy of the proposed model. © 2017, Iran University of Science and Technology.
Publication Date: 2021
Scientia Iranica (23453605)28(1A)pp. 109-123
One of the most prevalent ground motion Intensity Measures (IMs) is the spectral acceleration at the fundamental period of a structure. Previous research has shown that vectorizing scalar IMs leads to a more reliable structural response, particularly in nonlinear regions and near collapse. Furthermore, the nonlinear behavior of ductile structures results in elongation of their "effective period". Therefore, this paper proposes a new approach to selecting ground motion records considering the effect of spectral shape and period elongation. This method contains two disaggregation analyses at the fundamental and elongated periods of the structure. Nonlinear dynamic analysis is conducted on a set of reinforced concrete moment-resisting frames designed based on ACI 318-05 as representatives of modern structures. Results show a considerable decrease in the median collapse prediction, margin against collapse, and dispersion of the structural response. The presented approach can ensure a better prediction of the vulnerability of structures to collapse. © 2021 Sharif University of Technology. All rights reserved.
Publication Date: 2017
Intelligent Buildings International (17566932)9(4)pp. 222-236
In this article, an intelligent method to detect, locate and quantify structural damages is presented via an optimization model. To predict the damage location and severity, the theory of pseudo-residual force vector (RFV) is applied. The proposed method can identify damages based on only a few mode shapes of the structure that can be easily obtained by a dynamic test. The objective function is defined as a minimum difference between the numerical and experimental variables in the RFV and the gravitational search algorithm is employed as a meta-heuristic technique for solving this optimization problem. The efficiency of the proposed method is investigated through the numerical examples with different damage scenarios. In the examples, the experimental data were simulated numerically using a finite element model of the structure and as demonstrated, it is possible to identify the damages with a reasonable level of accuracy while considering noise effects. © 2016 Informa UK Limited, trading as Taylor & Francis Group.
Publication Date: 2025
Stochastic Environmental Research And Risk Assessment (14363259)39(4)pp. 1605-1621
One major characteristic of the Standardized Drought Indices is their dependence on one variable. However, different variables influence drought simultaneously. To address this issue, this study modifies and develops the Surface Water Supply Index (SWSI) to involve multiple aspects of droughts. Data on precipitation, runoff, reservoir volume, and discharge (instead of snow) over 21 years are used to modify the SWSI in Marun, Khuzestan Province, Iran. Standardized Precipitation Index (SPI), Standardized Runoff Index (SRI), Standardized Reservoir Storage Index (SRSI), and Standardized Discharge Index (SDI) are used as standard univariate indices to evaluate a new comprehensive index. The Shannon Entropy (SE) method is utilized innovatively to determine the weights of the comprehensive index, instead of deriving them depending on the weather experts. Additionally, a Modified-Surface Water Supply Index (M-SWSI) is also proposed to align it with the existing standard indices. For comparison, the weights are also calculated using the Proportioning Objective Procedure (POP) method, and presented in the POP-SWSI index. The results indicate that utilizing the SE method to determine weights provides an exceptional perspective on the meteorological and hydrological conditions of the drought-affected upstream region; while determining the weights using the POP method provides an insightful socio-economic and hydrological view on the drought-affected downstream region. In 2017, one of the most severe years, the M-SWSI index detected a drought event one month earlier than the POP-SWSI, with a drought duration value of 6 months close to the duration value of 5 months identified by POP-SWSI. Furthermore, the severity values were similar between the two indices, although the M-SWSI indicated lower drought severity than the univariate indices. Copulas are also employed for drought events analysis and to build the joint distribution function of drought severity (S) and duration (D) for the M-SWSI. Bivariate cumulative probability distribution functions are created and analyzed to determine the periodic “and” and “or” bivariate drought return periods. Additionally, Severity-Duration-Frequency (SDF) curves are established to evaluate the M-SWSI index. The Marun dam has been chosen as a case study to analyze the surface water supply under drought conditions, aiming to develop management policies for downstream decision-making. Consequently, the M-SWSI can be applied to any dam reservoir for similar analyses. This index involves various aspects of drought and can be utilized for reservoir management, assessing risks, and addressing flood and flood risk management challenges. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.
Publication Date: 2017
Desalination and Water Treatment (19443994)60pp. 106-113
For water quality assessment, there are several water quality indices, such as National Sanitation Foundation-Water Quality Index (NSF-WQI). These indices are determined by measuring several parameters in different samplings. Because the value of some of the measured parameters is constant during the different samplings; hence, these parameters can be measured in the earlier samplings and be used in the later one. The identification of these parameters can reduce the time as well as the cost of water quality evaluation. In this study, a new strategy by Taguchi method was used to propose a method (proposed method) to determine the mentioned parameters in a case study of Karaj River, Iran. For demonstrating capability of this strategy, water quality was calculated by standard (NFS-WQI), adjusted, and proposed methods and then the results were compared. Nine measured parameters in standard method were reduced to four by using the proposed method. In contrast to standard and adjusted methods that showed significant differences (p < 0.1), there were no differences between proposed and standard method results. Therefore, the proposed method may be recommended for water quality evaluation with reduction of the cost and the time. © 2017 Desalination Publications. All rights reserved.
Publication Date: 2024
Thin-Walled Structures (02638231)199
Cold-formed steel composite beams are known for their unique advantages, like being lightweight and ease of installation. The use of profiled steel sheeting in cold-formed composite beams reduces construction time and costs by acting as a permanent formwork in the composite beams. The current study presents a 3D finite element model of cold-formed steel composite beam specimens comprising a cold-formed double-lipped channel section, profiled steel sheeting, concrete slab, and bolted shear connector. Employing bolted shear connectors, structural components can be deconstructed and replaced after their service life expires or if they are damaged. The characteristics of the materials obtained from an experimental program were assigned to the finite element model. Geometric characteristics, material nonlinearities, and loading procedures were attentively simulated, and a dynamic explicit procedure was employed for the numerical analyses. A comparison of the results obtained from the finite element models and the available experimental results validated the precision of the models. Then, numerical studies were conducted to investigate the effects of various parameters, including compressive strength of concrete, thickness of concrete slab, height and grade of cold-formed steel section, thickness of profiled steel sheeting, number and diameter of shear connectors, on the behavior of the composite beam. The results showed that the height and grade of the cold-formed steel section and compressive strength and thickness of the concrete slab have a significant effect on increasing the capacity of the composite beam. © 2024 Elsevier Ltd
Khouzani, M.A.,
Zeynalian dastjerdi, M.,
Hashemi esfahanian, M.,
Mostofinejad, D.,
Farahbod, F.,
Shahadifar, M. Publication Date: 2021
Journal of Building Engineering (23527102)44
Several roofing systems have been proposed given their significance in concrete structures, in terms of time and resources. A biaxial voided slab system is introduced to improve the solid slab system's performance by creating voids in the concrete and removing ineffective material. In this study, the bending behavior of voided slabs is investigated numerically. For this purpose, a numerical ABAQUS model is presented and then verified using available experimental results. Then, a parametric study was carried out focusing on the plastic balls and their spacing, steel cages, and the position of plastic balls relative to the slab height. As shown in this paper, the presence of plastic balls improves the flexural capacity, because of steel cages. However, the spacing between plastic balls and their position have not a significant effect on flexural behavior. Finally, the numerical results were compared with the ultimate moment capacities from ACI 318-19, AS 3600-18, EC2 2004, and CSA A23.3-19, and were shown that considering steel cages have better consistencies with numerical results. © 2021 Elsevier Ltd
Publication Date: 2011
Thin-Walled Structures (02638231)49(12)pp. 1517-1525
Non-linear finite element analyses were carried out to evaluate and optimize the seismic characteristics of knee-braced cold formed steel shear walls using software ANSYS. Different structural characteristics including: material nonlinearity, geometric imperfection, residual stresses and perforations are taken into account. The numerical models were verified based on experimental tests. Agreement of the numerical simulations and the test results showed that finite element analysis can be used effectively to predict the ultimate capacity of knee-braced CFS shear panels. A total of 12 models with a various ranges of knee-elements lengths were investigated. Of particular interests were the specimens maximum lateral load capacity and deformation behavior in addition to a rational estimation of the seismic response modification factor. Preliminary conclusions presented in this paper, refer to the optimum seismic characteristics of knee-braced CFS shear walls and the corresponding dimensions and configuration. © 2011 Published by Elsevier Ltd.
Publication Date: 2012
Thin-Walled Structures (02638231)60pp. 229-238
This paper presents a non-linear finite element analyses in order to optimize the seismic characteristics of strap-braced cold formed steel shear walls enhanced with brackets in the four interior corners of the wall. The numerical models presented here are verified based on experimental tests considering different structural characteristics including: material nonlinearity, geometrical imperfection, residual stresses and perforations. A comparison between the numerical simulations and the test results shows a good agreement proves that the finite element analysis can be used effectively to predict the ultimate capacity of strap-braced CFS shear panels. A total of 16 models with different variants of bracket length are investigated. Of particular interests were the specimens' maximum lateral load capacity and deformation behavior in addition to a rational estimation of the seismic response modification factor. Preliminary conclusions presented in this paper, refer to the optimum seismic characteristics of strap-braced CFS shear walls and the corresponding dimensions and configuration. © 2012 Elsevier Ltd.
Publication Date: 2014
Journal of the Mechanics and Physics of Solids (00225096)71(1)pp. 1-14
In this study, we first demonstrate that the J-integral in classical linear elasticity becomes path-dependent when the solid is subjected to combined electrical, chemical and mechanical loadings. We then construct an electro-chemo-mechanical J-integral that is path-independent under such combined multiple driving forces. Further, we show that this electro-chemo-mechanical J-integral represents the rate at which the grand potential releases per unit crack growth. As an example, the path-independent nature of the electro-chemo-mechanical J-integral is demonstrated by solving the problem of a thin elastic film delaminated from a thick elastic substrate. © 2014 Elsevier Ltd.
Publication Date: 2013
Computers and Fluids (00457930)81pp. 134-144
The rise of GPUs in modern high-performance systems increases the interest in porting portion of codes to such hardware. The current paper aims to explore the performance of a portable state-of-the-art FE solver on GPU accelerators. Performance evaluation is done by comparing with an existing highly-optimized OpenMP version of the solver. Code portability is ensured by writing the program using the OpenCL 1.1 specifications, while performance portability is sought through an optimization step performed at the beginning of the calculations to find out the optimal parameter set for the solver. The results show that the new implementation can be several times faster than the OpenMP version. © 2013 Elsevier Ltd.
Publication Date: 2024
Arabian Journal for Science and Engineering (21914281)49(4)pp. 5447-5466
The lack of a code for preparing one-part geopolymer concrete (GPC) is one of the major obstacles to its wide use. This study adopted one of the most common methods for preparing ordinary concrete, the ACI method, taking into account the most important variables affecting this method and then modified it to suit one-part GPC. Three different sizes of aggregates and four water-to-binder ratios (W/B) were used in preparing the concrete mixtures in this study. In addition, three different proportions of sodium metasilicate were used as the activator, which ultimately resulted in a total of 36 mix designs. Specimens were subjected to various tests, including setting time, workability, and compressive strength. In addition, the material's behaviour was studied using X-ray diffraction and scanning electron microscope. The results indicate that the ACI method is generally applicable for designing geopolymer concrete mixtures with minor adjustments. Consequently, the table used for predicting concrete strength based on a specific water/cement ratio has been replaced with relevant figures that depict the relationship between compressive strength and the water-to-binder ratio. In addition, a step-by-step flowchart has been presented that explains how to design one-part geopolymer concrete. Conducted experiments indicated that the properties of geopolymer concrete are greatly affected by the ratio of W/B and the size of aggregate used in preparing the concrete mixture. Furthermore, the quantity of activators has significant effects on concrete's workability and compressive strength. Results of the experiment suggest that one-part GPC can provide greater compressive strength than ordinary concrete. © King Fahd University of Petroleum & Minerals 2023.
