Petteri Kokkonen, B. Hemming, E. Mikkola, Linus Teir, Ville Lämsä, J. Junttila
In this paper, robustness optimization of a fatigue-critical welded structure with measured misalignments and a generic robust design procedure are presented. The motivation for considering uncertainties, robustness and multi-criteria decision making in engineering design comes from the increasing sustainability requirements. Lightweight design of vehicles can reduce CO2 emissions and increase energy and material efficiency, but often the fatigue of welds limits the weight reduction. The manufacturing quality affects the fatigue strength of welds, and by quantifying the manufacturing quality and using robust design methodology the increasing sustainability requirements can be met, while also considering the technical and economical constraints. The surrogate model representing the relationship between the actual, measured geometry and the fatigue life can be used as the digital twin during operation.
{"title":"Robust lightweight design and digital twins considering manufacturing quality variation and sustainability requirements","authors":"Petteri Kokkonen, B. Hemming, E. Mikkola, Linus Teir, Ville Lämsä, J. Junttila","doi":"10.23998/rm.120693","DOIUrl":"https://doi.org/10.23998/rm.120693","url":null,"abstract":"In this paper, robustness optimization of a fatigue-critical welded structure with measured misalignments and a generic robust design procedure are presented. The motivation for considering uncertainties, robustness and multi-criteria decision making in engineering design comes from the increasing sustainability requirements. Lightweight design of vehicles can reduce CO2 emissions and increase energy and material efficiency, but often the fatigue of welds limits the weight reduction. The manufacturing quality affects the fatigue strength of welds, and by quantifying the manufacturing quality and using robust design methodology the increasing sustainability requirements can be met, while also considering the technical and economical constraints. The surrogate model representing the relationship between the actual, measured geometry and the fatigue life can be used as the digital twin during operation.","PeriodicalId":52331,"journal":{"name":"Rakenteiden Mekaniikka","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43045495","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}
Typical concrete is a mixture of Portland cement, water, and aggregates. While aggregates have a substantial effect on the concrete strength and fracture behavior, the focus of the present study is on the hardened cement paste which can be further divided into the unreacted core, inner and outer products. In high strength concrete, water-to-cement ratio is low, and thus the distance between cement particles is small. Also, the amount of unreacted (high strength) core is higher, and the porosity is low. When water-to-cement ratio is higher, both the distance between cement particles and the porosity due to capillary pores increases. In the present study, we develop a numerical model based on the embedded discontinuity finite elements to predict the effect of the water-to-cement ratio on the compressive fracture behavior of concrete. Representative 2D plane strain simulations demonstrate that the present method captures the major features of concrete fracture and, particularly, qualitatively predicts the known effects of the water-to-cement ratio on concrete compressive strength.
{"title":"Modelling the effect of concrete cement composition on its strength and failure behavior","authors":"T. Saksala, K. Kolari, R. Kouhia","doi":"10.23998/rm.120704","DOIUrl":"https://doi.org/10.23998/rm.120704","url":null,"abstract":"Typical concrete is a mixture of Portland cement, water, and aggregates. While aggregates have a substantial effect on the concrete strength and fracture behavior, the focus of the present study is on the hardened cement paste which can be further divided into the unreacted core, inner and outer products. In high strength concrete, water-to-cement ratio is low, and thus the distance between cement particles is small. Also, the amount of unreacted (high strength) core is higher, and the porosity is low. When water-to-cement ratio is higher, both the distance between cement particles and the porosity due to capillary pores increases. In the present study, we develop a numerical model based on the embedded discontinuity finite elements to predict the effect of the water-to-cement ratio on the compressive fracture behavior of concrete. Representative 2D plane strain simulations demonstrate that the present method captures the major features of concrete fracture and, particularly, qualitatively predicts the known effects of the water-to-cement ratio on concrete compressive strength.","PeriodicalId":52331,"journal":{"name":"Rakenteiden Mekaniikka","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44191159","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}
Lightweight structures, especially trusses, have attracted a tremendous attention due to their extensive applications in the construction of infrastructures. Optimizing the shape and cross-sectional topology of truss members is essential since the truss systems are widely used in engineering routines. These systems form the framework of structures like bridges, steel halls for industry and trade, and towers. For the scope of this research, genetic algorithms were used for weight optimization of truss structures. This paper aims to optimize truss structures for finding optimal cross-sectional area. To optimize the cross-sectional area, all members were selected as design variables, with the structure’s weight being the objective function. The restrictions related to the change of the location of the nodes and the tension in the members were the looked-upon problems, the permissible values of which were determined under the circumstances of the problem. In addition, the resulting optimized model which masses for sizing, shape, and topology or their combinations, were compared.
{"title":"Weight optimization of truss structures by using genetic algorithms","authors":"Azad Javanmiri, J. Mäkinen","doi":"10.23998/rm.111471","DOIUrl":"https://doi.org/10.23998/rm.111471","url":null,"abstract":"Lightweight structures, especially trusses, have attracted a tremendous attention due to their extensive applications in the construction of infrastructures. Optimizing the shape and cross-sectional topology of truss members is essential since the truss systems are widely used in engineering routines. These systems form the framework of structures like bridges, steel halls for industry and trade, and towers. For the scope of this research, genetic algorithms were used for weight optimization of truss structures. This paper aims to optimize truss structures for finding optimal cross-sectional area. To optimize the cross-sectional area, all members were selected as design variables, with the structure’s weight being the objective function. The restrictions related to the change of the location of the nodes and the tension in the members were the looked-upon problems, the permissible values of which were determined under the circumstances of the problem. In addition, the resulting optimized model which masses for sizing, shape, and topology or their combinations, were compared.","PeriodicalId":52331,"journal":{"name":"Rakenteiden Mekaniikka","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47113380","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}
Artikkelin aiheena on painovoimaisen ilmanvaihdon soveltaminen hormi-tyyppisiin aukkoihin käyttäen hyväksi mekaanisen energian taseen periaatetta. Kanavisto-virtauksen käsitteen häviökerroin yhteys painovoimaisen ilmanvaihdon käsitteeseen purkautumiskerroin tulee esille. Kontrollitilavuustarkastelut ovat tärkeässä asemassa. Kaksi yksinkertaista esimerkkitapausta esitetään. Artikkeli on aiheeltaan opetuksellinen.
{"title":"Purkautumiskerroin ja häviökerroin","authors":"E-M. Salonen, Rauno Holopainen","doi":"10.23998/rm.107658","DOIUrl":"https://doi.org/10.23998/rm.107658","url":null,"abstract":"Artikkelin aiheena on painovoimaisen ilmanvaihdon soveltaminen hormi-tyyppisiin aukkoihin käyttäen hyväksi mekaanisen energian taseen periaatetta. Kanavisto-virtauksen käsitteen häviökerroin yhteys painovoimaisen ilmanvaihdon käsitteeseen purkautumiskerroin tulee esille. Kontrollitilavuustarkastelut ovat tärkeässä asemassa. Kaksi yksinkertaista esimerkkitapausta esitetään. Artikkeli on aiheeltaan opetuksellinen.","PeriodicalId":52331,"journal":{"name":"Rakenteiden Mekaniikka","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47374230","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}
{"title":"Technical note: Open-source finite element software – from the early to the present","authors":"J. Niiranen","doi":"10.23998/rm.113300","DOIUrl":"https://doi.org/10.23998/rm.113300","url":null,"abstract":"","PeriodicalId":52331,"journal":{"name":"Rakenteiden Mekaniikka","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41607057","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}
The classical elastic theory of layered beams is used for the analysis of cross laminated timber (CLT) beams. A brief introduction of the theory is given and followed by examples. The theory of layered beams offers a widely studied, well established method for the analysis the CLT beams including displacements and stresses of each layer of the beam. It is shown that the theoretical basis of the widely used Shear Analogy is the same as the theoretical basis of the theory of layered beams. The results are compared to test results and to results of the finite element calculations. It is seen that the deflections and strains are in 10 % fractals in mean in the considered cases. The theory of layered beams seems to be suitable method in the analysis of the CLT beams at the elastic phase.
{"title":"CLT beam analysis using classical elastic theory of layered beams","authors":"M. Heinisuo, S. Pajunen","doi":"10.23998/rm.107868","DOIUrl":"https://doi.org/10.23998/rm.107868","url":null,"abstract":"The classical elastic theory of layered beams is used for the analysis of cross laminated timber (CLT) beams. A brief introduction of the theory is given and followed by examples. The theory of layered beams offers a widely studied, well established method for the analysis the CLT beams including displacements and stresses of each layer of the beam. It is shown that the theoretical basis of the widely used Shear Analogy is the same as the theoretical basis of the theory of layered beams. The results are compared to test results and to results of the finite element calculations. It is seen that the deflections and strains are in 10 % fractals in mean in the considered cases. The theory of layered beams seems to be suitable method in the analysis of the CLT beams at the elastic phase.","PeriodicalId":52331,"journal":{"name":"Rakenteiden Mekaniikka","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44578944","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}
Painovoimaisen ilmanvaihdon käsitettä purkautumiskerroin selostetaan erityisesti kontrollitilavuustarkastelujen avulla mekaanisen energian taseen periaatetta soveltamalla. Yksinkertainen esimerkkitapaus esitetään. Alan terminologiaa kommentoidaan. Artikkeli on aiheeltaan opetuksellinen.
{"title":"Purkautumiskerroin","authors":"E-M. Salonen, Rauno Holopainen","doi":"10.23998/rm.107342","DOIUrl":"https://doi.org/10.23998/rm.107342","url":null,"abstract":"Painovoimaisen ilmanvaihdon käsitettä purkautumiskerroin selostetaan erityisesti kontrollitilavuustarkastelujen avulla mekaanisen energian taseen periaatetta soveltamalla. Yksinkertainen esimerkkitapaus esitetään. Alan terminologiaa kommentoidaan. Artikkeli on aiheeltaan opetuksellinen.","PeriodicalId":52331,"journal":{"name":"Rakenteiden Mekaniikka","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43033948","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}
The mechanical effects of a parabolic tendon can be modeled replacing the tendon by external loads applied to the concrete. The intensity of these loads depends on the prestressing force P and curvature of the tendons. These two factors are also interrelated because the losses of prestress vary with the curvature. The structural analysis can be simplified by approximating that the line load against the tendon, able to maintain the initial parabolic form of the tendon and called equivalent load, is constant, perpendicular to the centroidal axis of the beam and equal to P/R where R is the radius of curvature of the parabola at its vertex. This approximation is one of the key issues in the textbooks but normally not properly justified. In this paper, the mathematical background for the approximation is formulated. Some typical tendon layouts are analyzed to evaluate the approximation error. The error proved to be insignificant for simple beams. For cantilever and continuous beams more accurate methods in the final design are recommended.
{"title":"Parabolic tendons in prestressed concrete - how accurate are equivalent loads?","authors":"M. Pajari","doi":"10.23998/rm.100697","DOIUrl":"https://doi.org/10.23998/rm.100697","url":null,"abstract":"The mechanical effects of a parabolic tendon can be modeled replacing the tendon by external loads applied to the concrete. The intensity of these loads depends on the prestressing force P and curvature of the tendons. These two factors are also interrelated because the losses of prestress vary with the curvature. The structural analysis can be simplified by approximating that the line load against the tendon, able to maintain the initial parabolic form of the tendon and called equivalent load, is constant, perpendicular to the centroidal axis of the beam and equal to P/R where R is the radius of curvature of the parabola at its vertex. This approximation is one of the key issues in the textbooks but normally not properly justified. In this paper, the mathematical background for the approximation is formulated. Some typical tendon layouts are analyzed to evaluate the approximation error. The error proved to be insignificant for simple beams. For cantilever and continuous beams more accurate methods in the final design are recommended.","PeriodicalId":52331,"journal":{"name":"Rakenteiden Mekaniikka","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44162542","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}
An analytic method is presented for the analysis of flexural restraint of members by sandwich panels. Using the method, which is based on the solutions of the fourth order differential equations, the restraint effect of sandwich panels can be approximated in practical cases. The reliability of the method is shown based on tests and finite element analyses. New results are shown using the analytic method for buckling cases and for P-δ analysis in the elastic range. The exact finite element method (FEM) formulation is given for more complicated cases.
{"title":"Buckling analysis of members restrained by sandwich panels","authors":"M. Heinisuo","doi":"10.23998/RM.91027","DOIUrl":"https://doi.org/10.23998/RM.91027","url":null,"abstract":"An analytic method is presented for the analysis of flexural restraint of members by sandwich panels. Using the method, which is based on the solutions of the fourth order differential equations, the restraint effect of sandwich panels can be approximated in practical cases. The reliability of the method is shown based on tests and finite element analyses. New results are shown using the analytic method for buckling cases and for P-δ analysis in the elastic range. The exact finite element method (FEM) formulation is given for more complicated cases.","PeriodicalId":52331,"journal":{"name":"Rakenteiden Mekaniikka","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48740574","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}
Artikkelissa esitetään menetelmät väsymisdatan ja yksikkökuormien yhdistämisestä ja sen käytöstä avoimen lähdekoodin FEM-ohjelmistojen yhteydessä väsymisvaurion selvittämiseksi. Kirjallisuudesta löytyvän esimerkin ja ohjelmalla lasketut tulokset olivat lähellä toisiaan. Avoimen lähdekoodin tarjoamat ratkaisut ovat siis varteenotettavia moniaksiaalisen väsymisen analysoinnissa.
{"title":"Avoimen lähdekoodin hyödyntäminen väsymisanalyysissä","authors":"Ilkka Valkonen","doi":"10.23998/RM.103377","DOIUrl":"https://doi.org/10.23998/RM.103377","url":null,"abstract":"Artikkelissa esitetään menetelmät väsymisdatan ja yksikkökuormien yhdistämisestä ja sen käytöstä avoimen lähdekoodin FEM-ohjelmistojen yhteydessä väsymisvaurion selvittämiseksi. Kirjallisuudesta löytyvän esimerkin ja ohjelmalla lasketut tulokset olivat lähellä toisiaan. Avoimen lähdekoodin tarjoamat ratkaisut ovat siis varteenotettavia moniaksiaalisen väsymisen analysoinnissa.","PeriodicalId":52331,"journal":{"name":"Rakenteiden Mekaniikka","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41546736","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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