Pub Date : 2019-10-01DOI: 10.2495/cmem-v7-n4-376-384
A. Nawaz, A. S. Arora, C. Yun, Hwanchul Cho, Moonyong Lee
The anammox process, used to remove nitrogen from wastewaters is conside red a promising approach due to its advantages over traditional processes. The current study emphasizes on the cost effective nitrogen removal from the sidestream effl uent of anaerobic digester with partial nitration (PN) and anaerobic ammonium oxidation (anammox) process for the municipal wastewater treatment plant. The main objective of this study was to model a cost effective strategy for setting up a lab-scale sequencing batch reactor (SBR) by using activated sludge model (ASM) process equations with applying novel control strategies (NCS) for improving nitrogen-removal effi ciency (NRE). An average rate of removal 80% was obtained during the period of its operation. NCS (intermittent aeration, alteration in the cycle length, etc) were introduced to optimize the operating cost. The overall system contributes to lowering in the greenhouse gas emissions by minimizing the use of energy (60–65%) and hence supporting the WHO mission of achieving sustainable development goals. Results further indicate the future possibility of escalating the lab-scale to full-scale applications.
{"title":"Cost effective nitrogen removal – Novel control strategies","authors":"A. Nawaz, A. S. Arora, C. Yun, Hwanchul Cho, Moonyong Lee","doi":"10.2495/cmem-v7-n4-376-384","DOIUrl":"https://doi.org/10.2495/cmem-v7-n4-376-384","url":null,"abstract":"The anammox process, used to remove nitrogen from wastewaters is conside red a promising approach due to its advantages over traditional processes. The current study emphasizes on the cost effective nitrogen removal from the sidestream effl uent of anaerobic digester with partial nitration (PN) and anaerobic ammonium oxidation (anammox) process for the municipal wastewater treatment plant. The main objective of this study was to model a cost effective strategy for setting up a lab-scale sequencing batch reactor (SBR) by using activated sludge model (ASM) process equations with applying novel control strategies (NCS) for improving nitrogen-removal effi ciency (NRE). An average rate of removal 80% was obtained during the period of its operation. NCS (intermittent aeration, alteration in the cycle length, etc) were introduced to optimize the operating cost. The overall system contributes to lowering in the greenhouse gas emissions by minimizing the use of energy (60–65%) and hence supporting the WHO mission of achieving sustainable development goals. Results further indicate the future possibility of escalating the lab-scale to full-scale applications.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"431 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79582045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-01DOI: 10.2495/cmem-v7-n4-201-211
G. Nasif, R. Balachandar, R. Barron
a numerical investigation is carried out to evaluate the influence of the gap between the bluff body and the bed on the wake characteristics generated in shallow flows. a sharp-edge bluff body with a fixed gap from the bed is employed in the study, and the results are compared with the no gap case. a sharp-edged bluff body was chosen to minimize the effect of reynolds number and ensure fixed flow separation points. The transient three-dimensional Navier–Stokes equations are numerically solved using a finite volume approach with the detached eddy simulation turbulence model. The flow field in this study involves two different fluids, i.e. water and the air above it. The volume of fluid method is used for tracking the free surface separating the water and air. The fluid structures that are generated in the wake are identified using the λ2-criterion. The results reveal that the gap flow will develop a new structure near the bed, which enhances the upwash flow immediately after the submerged jet is about to turn upwards due to the weak hydraulic jump. This structure plays an important role in recovering the free surface to its original shape at a shorter downstream distance from the bluff body than when there is no gap.
{"title":"Effect of gap on the flow characteristics in the wake of a bluff body near a wall","authors":"G. Nasif, R. Balachandar, R. Barron","doi":"10.2495/cmem-v7-n4-201-211","DOIUrl":"https://doi.org/10.2495/cmem-v7-n4-201-211","url":null,"abstract":"a numerical investigation is carried out to evaluate the influence of the gap between the bluff body and the bed on the wake characteristics generated in shallow flows. a sharp-edge bluff body with a fixed gap from the bed is employed in the study, and the results are compared with the no gap case. a sharp-edged bluff body was chosen to minimize the effect of reynolds number and ensure fixed flow separation points. The transient three-dimensional Navier–Stokes equations are numerically solved using a finite volume approach with the detached eddy simulation turbulence model. The flow field in this study involves two different fluids, i.e. water and the air above it. The volume of fluid method is used for tracking the free surface separating the water and air. The fluid structures that are generated in the wake are identified using the λ2-criterion. The results reveal that the gap flow will develop a new structure near the bed, which enhances the upwash flow immediately after the submerged jet is about to turn upwards due to the weak hydraulic jump. This structure plays an important role in recovering the free surface to its original shape at a shorter downstream distance from the bluff body than when there is no gap.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"65 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90882502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-01DOI: 10.2495/cmem-v7-n4-363-375
R. Vodička, K. Krajníková
A computational model for analysis of rate-dependent interface damage which leads to interface crack initiation and propagation in multi-domain structures exposed to shear type cyclic loading is presented. Modelling of interface damage, accounting generally for various stress vs. separation relations of common cohesive zone models in this type of models, is restricted here to one with an exponential relation. The model also includes viscosity and internal parameters for the interface damage to observe a fatiguelike behaviour where a crack appears for smaller magnitudes of periodical loadings in comparison to pure uploading. The computational approach, physically based on evolution of stored and dissipated energies, behind the model results in a kind of variational formulation. Moreover, solving the problem for variables characterising the elastic state of the structure, the multi-domain symmetric Galerkin boundary element method is advantageously used. Finally, the variational character of the solution requires implementation of (sequential-) quadratic programing solvers into the computer code which is fully implemented in MATLAB. The presented numerical results for a rather academic structure demonstrate the properties of the described model and enable to extend its applicability to more general problems of engineering practice.
{"title":"A boundary element approach for an interface visco-damage model exposed to cyclic shear load","authors":"R. Vodička, K. Krajníková","doi":"10.2495/cmem-v7-n4-363-375","DOIUrl":"https://doi.org/10.2495/cmem-v7-n4-363-375","url":null,"abstract":"A computational model for analysis of rate-dependent interface damage which leads to interface crack initiation and propagation in multi-domain structures exposed to shear type cyclic loading is presented. Modelling of interface damage, accounting generally for various stress vs. separation relations of common cohesive zone models in this type of models, is restricted here to one with an exponential relation. The model also includes viscosity and internal parameters for the interface damage to observe a fatiguelike behaviour where a crack appears for smaller magnitudes of periodical loadings in comparison to pure uploading. The computational approach, physically based on evolution of stored and dissipated energies, behind the model results in a kind of variational formulation. Moreover, solving the problem for variables characterising the elastic state of the structure, the multi-domain symmetric Galerkin boundary element method is advantageously used. Finally, the variational character of the solution requires implementation of (sequential-) quadratic programing solvers into the computer code which is fully implemented in MATLAB. The presented numerical results for a rather academic structure demonstrate the properties of the described model and enable to extend its applicability to more general problems of engineering practice.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"169 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77822321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-01DOI: 10.2495/CMEM-V7-N4-327-339
D. Montalvão, Attila Blaskovics, P. Costa, L. Reis, M. Freitas
With the development of new materials, it is now known that there is no such thing as a fatigue endurance limit, i.e., materials do not have infinite life when the stress level is such that there is no fracture up to 10 million (1E7) cycles. The problem of testing materials above this number of cycles is that most testing equipment operates well below 150 Hz, making testing up to 1 billion (1E9) cycles or above an impracticality. The recent developments of ultrasonic testing machines where frequencies can go as high as 20 kHz or above enabled tests to be extended to these ranges in just a few days. This is now known as Very High Cycle Fatigue (VHCF). On the other hand, critical components used in Engineering applications are usually subjected to multi-axial loads, as is the case of the fuselage and wings of aircrafts which are subjected to biaxial states of stress. In this paper, VHCF cruciform test specimens purposely designed to develop orthogonal biaxial stresses with different biaxiality ratios will be analysed. The specimens are composed from Aluminium 6082-T651, a medium strength alloy used in many highly stressed engineering applications, including trusses, cranes, bridges and transportation. The specimens work as tuning forks with determined mode shapes at 20±0.5 kHz, where maximum principal stresses are developed at the centre of the specimen. Finite Element Analysis (FEA) is used to assess the dynamic behaviour of the specimens. The framework on how to design and manufacture cruciform specimens with different biaxiality ratios will be explained in a clear way so it can be used by other engineers in the field.
{"title":"Numerical analysis of vhcf cruciform test specimens with non-unitary biaxiality ratios","authors":"D. Montalvão, Attila Blaskovics, P. Costa, L. Reis, M. Freitas","doi":"10.2495/CMEM-V7-N4-327-339","DOIUrl":"https://doi.org/10.2495/CMEM-V7-N4-327-339","url":null,"abstract":"With the development of new materials, it is now known that there is no such thing as a fatigue endurance limit, i.e., materials do not have infinite life when the stress level is such that there is no fracture up to 10 million (1E7) cycles. The problem of testing materials above this number of cycles is that most testing equipment operates well below 150 Hz, making testing up to 1 billion (1E9) cycles or above an impracticality. The recent developments of ultrasonic testing machines where frequencies can go as high as 20 kHz or above enabled tests to be extended to these ranges in just a few days. This is now known as Very High Cycle Fatigue (VHCF). On the other hand, critical components used in Engineering applications are usually subjected to multi-axial loads, as is the case of the fuselage and wings of aircrafts which are subjected to biaxial states of stress. In this paper, VHCF cruciform test specimens purposely designed to develop orthogonal biaxial stresses with different biaxiality ratios will be analysed. The specimens are composed from Aluminium 6082-T651, a medium strength alloy used in many highly stressed engineering applications, including trusses, cranes, bridges and transportation. The specimens work as tuning forks with determined mode shapes at 20±0.5 kHz, where maximum principal stresses are developed at the centre of the specimen. Finite Element Analysis (FEA) is used to assess the dynamic behaviour of the specimens. The framework on how to design and manufacture cruciform specimens with different biaxiality ratios will be explained in a clear way so it can be used by other engineers in the field.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74905766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-01DOI: 10.2495/cmem-v7-n4-340-349
F. Pape, M. Petzold, G. Poll
To reduce wear in tribosystems, the formation of a protective tribofi lm is benefi cial. by applying additives to the lubricating oil or grease, an anti-wear boundary layer can be achieved. For simulating the induced stresses on the bearings surface, the formed tribofi lm should be regarded. In this study, cylindrical roller thrust bearings were investigated regarding a tribofi lm formed by oil containing zinc dialkyldithiophosphate (ZDDP) additives. Due to the test conditions, a smooth fi lm with low roughness forms on the surface. The fi lm consists of glassy Fe/Zn polyphosphates with a height of up to 150 nm and a width of approximately 1 μm. based on the roughness, the surface was modelled with regularly distributed dimples to be used for a fi nite element model for the contact between a roller and a bearing washer regarding contact stress and tangential forces due to slip. The dimples in the contact between roller and washer lead to an inhomogeneous pressure distribution near the surface. During the contact, the surface pads of the roller partly slide over the surface pads of the washer in dependence of the contact position. of particular interest is the deformation in running direction. If the asperities of the roller press against th e washers asperities, a signifi cant deformation at the dimples and in the volume underneath occurs. As expected, the strains occur in the regions with high deformation gradients. During rolling, the deformations lead to areas that are stretched and compressed. The maximum strains are located between the dimples and shift in rolling direction from pad to pad. It has to be assumed, that the formation of cracks starts between the dimples at the surface and develop along the stretched areas whereas the cracking in the compressed areas is suppressed or at least impeded. The simulative results were compared to literature proving that the values determined by simulation are in well agreement.
{"title":"Computational investigation of crack inducing forces on bearing surfaces regarding the tribofilm structure","authors":"F. Pape, M. Petzold, G. Poll","doi":"10.2495/cmem-v7-n4-340-349","DOIUrl":"https://doi.org/10.2495/cmem-v7-n4-340-349","url":null,"abstract":"To reduce wear in tribosystems, the formation of a protective tribofi lm is benefi cial. by applying additives to the lubricating oil or grease, an anti-wear boundary layer can be achieved. For simulating the induced stresses on the bearings surface, the formed tribofi lm should be regarded. In this study, cylindrical roller thrust bearings were investigated regarding a tribofi lm formed by oil containing zinc dialkyldithiophosphate (ZDDP) additives. Due to the test conditions, a smooth fi lm with low roughness forms on the surface. The fi lm consists of glassy Fe/Zn polyphosphates with a height of up to 150 nm and a width of approximately 1 μm. based on the roughness, the surface was modelled with regularly distributed dimples to be used for a fi nite element model for the contact between a roller and a bearing washer regarding contact stress and tangential forces due to slip. The dimples in the contact between roller and washer lead to an inhomogeneous pressure distribution near the surface. During the contact, the surface pads of the roller partly slide over the surface pads of the washer in dependence of the contact position. of particular interest is the deformation in running direction. If the asperities of the roller press against th e washers asperities, a signifi cant deformation at the dimples and in the volume underneath occurs. As expected, the strains occur in the regions with high deformation gradients. During rolling, the deformations lead to areas that are stretched and compressed. The maximum strains are located between the dimples and shift in rolling direction from pad to pad. It has to be assumed, that the formation of cracks starts between the dimples at the surface and develop along the stretched areas whereas the cracking in the compressed areas is suppressed or at least impeded. The simulative results were compared to literature proving that the values determined by simulation are in well agreement.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84015894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-01DOI: 10.2495/cmem-v7-n4-316-326
Nicolò Beccati, C. Ferrari, M. Parma, Massimo Semprini
Dredge pumps are a complex engineering topic in comparison to water pumps. Mixtures of seawater with several types of soils do not behave as a homogenous fluid, and numerical simulations of these machines can be very challenging. Typical numerical approaches to simulations of dredge pumps are single-phase equivalent slurry and multi-phase liquid–solid, where the specification of the particle flow field can be Eulerian or lagrangian. The single-phase slurry approach is not sufficient to describe the effects of particle size and concentration of the solid phase on pump performance; for this reason, this paper examines a multi-phase CFD model applied to a dredge pump. The solid phase is modelled with an Eulerian approach, in order to reduce the computational effort required by a lagrangian method, mainly used for low solid-phase concentrations. The primary purpose of the presented model, developed using commercial software aNSYS CFX, is to predict head losses in a dredge pump working with several particle sizes, from 0.1 to 5 mm, and different volume concentrations of the solid phase, from 20% to 30%. For numerical solid-phase calibration, the effect of the particle size on pump performance is associated with non-Newtonian rheology of the simulated Eulerian phase. The numerical model is validated via experimental tests on the dredge pump using seawater. The calibration of the particle size effect is obtained from scientific literature data about dredge pump losses in different conditions. The model presented could be a useful tool for the analysis of existing dredge pumps or for the design of new machines.
{"title":"Eulerian multi-phase CFD model for predicting the performance of a centrifugal dredge pump","authors":"Nicolò Beccati, C. Ferrari, M. Parma, Massimo Semprini","doi":"10.2495/cmem-v7-n4-316-326","DOIUrl":"https://doi.org/10.2495/cmem-v7-n4-316-326","url":null,"abstract":"Dredge pumps are a complex engineering topic in comparison to water pumps. Mixtures of seawater with several types of soils do not behave as a homogenous fluid, and numerical simulations of these machines can be very challenging. Typical numerical approaches to simulations of dredge pumps are single-phase equivalent slurry and multi-phase liquid–solid, where the specification of the particle flow field can be Eulerian or lagrangian. The single-phase slurry approach is not sufficient to describe the effects of particle size and concentration of the solid phase on pump performance; for this reason, this paper examines a multi-phase CFD model applied to a dredge pump. The solid phase is modelled with an Eulerian approach, in order to reduce the computational effort required by a lagrangian method, mainly used for low solid-phase concentrations. The primary purpose of the presented model, developed using commercial software aNSYS CFX, is to predict head losses in a dredge pump working with several particle sizes, from 0.1 to 5 mm, and different volume concentrations of the solid phase, from 20% to 30%. For numerical solid-phase calibration, the effect of the particle size on pump performance is associated with non-Newtonian rheology of the simulated Eulerian phase. The numerical model is validated via experimental tests on the dredge pump using seawater. The calibration of the particle size effect is obtained from scientific literature data about dredge pump losses in different conditions. The model presented could be a useful tool for the analysis of existing dredge pumps or for the design of new machines.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75356238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-02DOI: 10.2495/cmem-v7-n3-260-274
A. Galybin
This article presents the general approach to incorrectly posed boundary value problems of the plane theory of elasticity with the boundary conditions formulated through the directions of displacement vectors and principal directions of the stress tensor. The approach is aimed at studying the solvability of problems of this type and allows one to determine the maximum number of arbitrary parameters on which the solution of the problem depends. We report analytical solutions for three particular formulations for the case of elastic half-plane and propose a numerical approach for solving the problems of this type for arbitrary contours.
{"title":"Incorrectly posed BVPs for elastic halfplane in TERMS of stress and displacement orientations","authors":"A. Galybin","doi":"10.2495/cmem-v7-n3-260-274","DOIUrl":"https://doi.org/10.2495/cmem-v7-n3-260-274","url":null,"abstract":"This article presents the general approach to incorrectly posed boundary value problems of the plane theory of elasticity with the boundary conditions formulated through the directions of displacement vectors and principal directions of the stress tensor. The approach is aimed at studying the solvability of problems of this type and allows one to determine the maximum number of arbitrary parameters on which the solution of the problem depends. We report analytical solutions for three particular formulations for the case of elastic half-plane and propose a numerical approach for solving the problems of this type for arbitrary contours.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74168334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-02DOI: 10.2495/cmem-v7-n3-212-225
B. Mncwango, D. Allopi
The construction of expanded polystyrene (EPS) dome houses requires intricate moulding equipment. A further obstacle in the accessibility of EPS dome houses is the minimum order placed by suppliers. Japan Dome House Company supplies dome houses at a minimum order of three-hundred units. This publication analyses how a miniature EPS dome house model created using a hot-wire system matches the claimed performance features of a factory-manufactured EPS Dome house. The purpose of this research is to investigate whether EPS dome houses can be created on an individual basis through a change in the construction method in order to increase product accessibility. All EPS dome pieces were carved over a period of 5 days. EPS pieces were assembled and left exposed to the elements since the main method of analysis of the live model was through exposure; particularly against rain and wind experienced within the jurisdiction of Pietermaritzburg, South Africa. Analysis of the live model was studied in conjunction with the compression, flexural and thermal qualities of EPS under laboratory conditions. With wind speeds of 39 km/h and a rainfall intensity of 28 mm, the model was still found to be in its original state of composure after three months even without having been permanently anchored to the ground. Observation of the model revealed that it is possible to successfully re-create an EPS dome house without complex moulding equipment. However, a compressive strength test on EPS revealed that the compressive qualities of EPS are significantly lower than that of conventional materials such as clay bricks. Contrary to what may be believed, a thermo-gravimetric analysis of three different densities (15, 20 and 30 kg/m 3 ) of EPS revealed that as the density of EPS increases, the maximum degradation value decreases. Dome houses are pre-fabricated and therefore have a reduced impact on the environment.
{"title":"A laboratory investigation and an appraisal of the viability of expanded polystyrene dwellings","authors":"B. Mncwango, D. Allopi","doi":"10.2495/cmem-v7-n3-212-225","DOIUrl":"https://doi.org/10.2495/cmem-v7-n3-212-225","url":null,"abstract":"The construction of expanded polystyrene (EPS) dome houses requires intricate moulding equipment. A further obstacle in the accessibility of EPS dome houses is the minimum order placed by suppliers. Japan Dome House Company supplies dome houses at a minimum order of three-hundred units. This publication analyses how a miniature EPS dome house model created using a hot-wire system matches the claimed performance features of a factory-manufactured EPS Dome house. The purpose of this research is to investigate whether EPS dome houses can be created on an individual basis through a change in the construction method in order to increase product accessibility. All EPS dome pieces were carved over a period of 5 days. EPS pieces were assembled and left exposed to the elements since the main method of analysis of the live model was through exposure; particularly against rain and wind experienced within the jurisdiction of Pietermaritzburg, South Africa. Analysis of the live model was studied in conjunction with the compression, flexural and thermal qualities of EPS under laboratory conditions. With wind speeds of 39 km/h and a rainfall intensity of 28 mm, the model was still found to be in its original state of composure after three months even without having been permanently anchored to the ground. Observation of the model revealed that it is possible to successfully re-create an EPS dome house without complex moulding equipment. However, a compressive strength test on EPS revealed that the compressive qualities of EPS are significantly lower than that of conventional materials such as clay bricks. Contrary to what may be believed, a thermo-gravimetric analysis of three different densities (15, 20 and 30 kg/m 3 ) of EPS revealed that as the density of EPS increases, the maximum degradation value decreases. Dome houses are pre-fabricated and therefore have a reduced impact on the environment.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83193052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-02DOI: 10.2495/cmem-v7-n3-236-245
T. Zula, S. Kravanja
This paper presents the simultaneous cost, standard sizes and rounded dimension optimization of a cantilever roof structure. Since the standard and rounded dimensions are proposed to be handled explic- itly in the discrete type of the optimization, the mixed-integer non-linear programming (MINlP) is applied. The structure is built from the standard hot rolled steel I sections for columns, beams and struts, and from the reinforced concrete bases. The MINlP optimization model of the cantilever roof structure is developed. The model comprises the objective function of the structure’s self-manufacturing costs and the design, resistance and dimensioning (in)equality constraints. The latter are defined in accordance with the Eurocode 2, 3 and 7 specifications. The modified outer-approximation/equality- relaxation (OA/ER) algorithm is used. The MINlP optimization of a cantilever roof structure for a small football stadium near the city of Maribor in Slovenia is presented at the end of the paper. The obtained optimal result includes the minimal production costs of the structure, the optimal standard sections of steel elements and the optimal rounded dimensions of the concrete bases.
{"title":"Minlp optimization of a cantilever roof structure","authors":"T. Zula, S. Kravanja","doi":"10.2495/cmem-v7-n3-236-245","DOIUrl":"https://doi.org/10.2495/cmem-v7-n3-236-245","url":null,"abstract":"This paper presents the simultaneous cost, standard sizes and rounded dimension optimization of a cantilever roof structure. Since the standard and rounded dimensions are proposed to be handled explic- itly in the discrete type of the optimization, the mixed-integer non-linear programming (MINlP) is applied. The structure is built from the standard hot rolled steel I sections for columns, beams and struts, and from the reinforced concrete bases. The MINlP optimization model of the cantilever roof structure is developed. The model comprises the objective function of the structure’s self-manufacturing costs and the design, resistance and dimensioning (in)equality constraints. The latter are defined in accordance with the Eurocode 2, 3 and 7 specifications. The modified outer-approximation/equality- relaxation (OA/ER) algorithm is used. The MINlP optimization of a cantilever roof structure for a small football stadium near the city of Maribor in Slovenia is presented at the end of the paper. The obtained optimal result includes the minimal production costs of the structure, the optimal standard sections of steel elements and the optimal rounded dimensions of the concrete bases.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77876696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-02DOI: 10.2495/cmem-v7-n3-246-259
A. Karageorghis, P. Tryfonos
The radial basis function (RBF) collocation method is applied for the approximation of functions in two variables. When the RBFs employed include a shape parameter, the determination of an appropriate value for it is a major issue. In this work, this is addressed by including the value of the shape parameter in the unknowns along with the coefficients of the RBFs in the approximation. The variable shape parameter case when a different shape parameter is associated with each RBF in the approximation is also considered. Both approaches yield nonlinear systems of equations, which are solved by a standard non-linear solver. The results of several numerical experiments are presented.
{"title":"Shape parameter estimation in RBF function approximation","authors":"A. Karageorghis, P. Tryfonos","doi":"10.2495/cmem-v7-n3-246-259","DOIUrl":"https://doi.org/10.2495/cmem-v7-n3-246-259","url":null,"abstract":"The radial basis function (RBF) collocation method is applied for the approximation of functions in two variables. When the RBFs employed include a shape parameter, the determination of an appropriate value for it is a major issue. In this work, this is addressed by including the value of the shape parameter in the unknowns along with the coefficients of the RBFs in the approximation. The variable shape parameter case when a different shape parameter is associated with each RBF in the approximation is also considered. Both approaches yield nonlinear systems of equations, which are solved by a standard non-linear solver. The results of several numerical experiments are presented.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"6 10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87238756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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