http://hdl.handle.net/2117/3826 Mon, 20 May 2013 00:02:31 GMT 2013-05-20T00:02:31Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no http://hdl.handle.net/2117/16826 Title: Linear buckling analysis of perforated steel storage rack columns with the Finite Strip Method Authors: Casafont Ribera, Miguel; Pastor Artigues, María Magdalena; Bonada Bo, Jordi; Roure Fernández, Francisco; Peköz, Teoman Abstract: An investigation on the use of the Finite Strip Method (FSM) to calculate elastic buckling loads of perforated cold formed storage rack columns is presented. Nowadays, this calculation can be accurately performed by means of the Finite Element Method (FEM), because the effect of perforations can be explicitly considered in the analysis. However, the FSM is preferred in cold-formed steel design since it is implemented in much convenient and easy to use software. The problem with FSM is that holes cannot be easily modeled. In this paper, the concept of the reduced thickness of the perforated strip is applied to take into account their effect. A formulation is presented for the reduced thickness that has been calibrated with loads obtained in eigen-buckling FEM analyses. Its accuracy has been verified carrying out analyses on real rack columns with different end conditions Wed, 31 Oct 2012 18:35:08 GMT http://hdl.handle.net/2117/16826 2012-10-31T18:35:08Z Casafont Ribera, Miguel; Pastor Artigues, María Magdalena; Bonada Bo, Jordi; Roure Fernández, Francisco; Peköz, Teoman no An investigation on the use of the Finite Strip Method (FSM) to calculate elastic buckling loads of perforated cold formed storage rack columns is presented. Nowadays, this calculation can be accurately performed by means of the Finite Element Method (FEM), because the effect of perforations can be explicitly considered in the analysis. However, the FSM is preferred in cold-formed steel design since it is implemented in much convenient and easy to use software. The problem with FSM is that holes cannot be easily modeled. In this paper, the concept of the reduced thickness of the perforated strip is applied to take into account their effect. A formulation is presented for the reduced thickness that has been calibrated with loads obtained in eigen-buckling FEM analyses. Its accuracy has been verified carrying out analyses on real rack columns with different end conditions http://hdl.handle.net/2117/16636 Title: Residual stresses and initial imperfections in non-linear analysis Authors: Pastor Artigues, María Magdalena; Bonada Bo, Jordi; Roure Fernández, Francisco; Casafont Ribera, Miguel Abstract: When non-linear finite element analysis (FEA) of cold-formed thin-walled steel sections subject to compression is carried out, an initial perturbation must be introduced in the model in order to trigger the failure due to instability. The most usual way is to introduce an equivalent initial imperfection in the model (conventional models) that includes the effects of geometric imperfections and residual stresses due to the roll-forming manufacturing process, possible loading eccentricity, etc. It is thought that results would be more accurate if the actual measured geometric imperfections and the actual residual stresses induced from manufacturing were introduced. This paper presents the determination of residual strains and stresses generated in the cold roll-forming process of a typical rack section (without perforations) from steel sheet, using FE simulation. The obtained residual elastic and plastic strains have then been incorporated in the model, and used as an initial strain state in the non-linear finite element analysis. The results obtained agree well with the experimental results for short and intermediate length columns, where the failure mode is predominately local and distortional. Thu, 04 Oct 2012 10:37:20 GMT http://hdl.handle.net/2117/16636 2012-10-04T10:37:20Z Pastor Artigues, María Magdalena; Bonada Bo, Jordi; Roure Fernández, Francisco; Casafont Ribera, Miguel no When non-linear finite element analysis (FEA) of cold-formed thin-walled steel sections subject to compression is carried out, an initial perturbation must be introduced in the model in order to trigger the failure due to instability. The most usual way is to introduce an equivalent initial imperfection in the model (conventional models) that includes the effects of geometric imperfections and residual stresses due to the roll-forming manufacturing process, possible loading eccentricity, etc. It is thought that results would be more accurate if the actual measured geometric imperfections and the actual residual stresses induced from manufacturing were introduced. This paper presents the determination of residual strains and stresses generated in the cold roll-forming process of a typical rack section (without perforations) from steel sheet, using FE simulation. The obtained residual elastic and plastic strains have then been incorporated in the model, and used as an initial strain state in the non-linear finite element analysis. The results obtained agree well with the experimental results for short and intermediate length columns, where the failure mode is predominately local and distortional. http://hdl.handle.net/2117/15826 Title: An investigation on the design of steel storage rack columns via the direct strength method Authors: Casafont Ribera, Miguel; Pastor Artigues, María Magdalena; Roure Fernández, Francisco; Bonada Bo, Jordi; Peköz, Teoman Abstract: The paper presents an attempt to predict the load carrying capacity of perforated rack columns by means of the Direct Strength Method (DSM). The investigation is focused on two different issues: the prediction of the elastic buckling loads of members with multiple perforations, and the evaluation of the accuracy of the current DSM buckling curves when applied to rack columns. In relation to the first issue, a model for the calculation of the reduced thickness of the perforated strip to be used in finite strip buckling analysis is developed. Regarding the study of the DSM curves, it is demonstrated that they can be used to accurately determine the strength of rack cross-sections whose failure is governed by distortional buckling or global buckling (with no significant participation of local buckling). This is an interesting result because it will allow substituting the distortional buckling tests, that are currently carried out in the process of design of these columns, by a simple and easy to apply calculation procedure. Fri, 11 May 2012 08:36:10 GMT http://hdl.handle.net/2117/15826 2012-05-11T08:36:10Z Casafont Ribera, Miguel; Pastor Artigues, María Magdalena; Roure Fernández, Francisco; Bonada Bo, Jordi; Peköz, Teoman no The paper presents an attempt to predict the load carrying capacity of perforated rack columns by means of the Direct Strength Method (DSM). The investigation is focused on two different issues: the prediction of the elastic buckling loads of members with multiple perforations, and the evaluation of the accuracy of the current DSM buckling curves when applied to rack columns. In relation to the first issue, a model for the calculation of the reduced thickness of the perforated strip to be used in finite strip buckling analysis is developed. Regarding the study of the DSM curves, it is demonstrated that they can be used to accurately determine the strength of rack cross-sections whose failure is governed by distortional buckling or global buckling (with no significant participation of local buckling). This is an interesting result because it will allow substituting the distortional buckling tests, that are currently carried out in the process of design of these columns, by a simple and easy to apply calculation procedure. http://hdl.handle.net/2117/14905 Title: Selection of the initial geometrical imperfection in nonlinear FE analysis of cold-formed steel rack columns Authors: Bonada Bo, Jordi; Casafont Ribera, Miguel; Roure Fernández, Francisco; Pastor Artigues, María Magdalena Abstract: This paper presents three methodologies to predict the load carrying capacity of cold formed steel rack columns via nonlinear finite element analysis (FEA). The column lengths are chosen in the range where the main failure is due to distortional buckling. It is demonstrated that for this range, to derive an accurate prediction of the ultimate load is more complex than for lengths where the main failure is local or global. The nonlinear analysis is carried out introducing an initial geometric imperfection on the upright. The three methodologies presented here allow for different imperfection shapes. The first one uses the critical mode shape (the first buckling mode). The second corresponds to an iterative methodology in which the shape that leads to the lowest ultimate load is used. These two first methodologies use exclusively the finite element method (FEM). The third one combines the finite element analysis with the generalised beam theory (GBT) in order to determine the modal participation of the FEM buckling mode and generate a particular combined geometric imperfection. To validate the predicted loads, the results of the three methodologies are compared with values obtained in experimental tests. Wed, 01 Feb 2012 11:48:21 GMT http://hdl.handle.net/2117/14905 2012-02-01T11:48:21Z Bonada Bo, Jordi; Casafont Ribera, Miguel; Roure Fernández, Francisco; Pastor Artigues, María Magdalena no This paper presents three methodologies to predict the load carrying capacity of cold formed steel rack columns via nonlinear finite element analysis (FEA). The column lengths are chosen in the range where the main failure is due to distortional buckling. It is demonstrated that for this range, to derive an accurate prediction of the ultimate load is more complex than for lengths where the main failure is local or global. The nonlinear analysis is carried out introducing an initial geometric imperfection on the upright. The three methodologies presented here allow for different imperfection shapes. The first one uses the critical mode shape (the first buckling mode). The second corresponds to an iterative methodology in which the shape that leads to the lowest ultimate load is used. These two first methodologies use exclusively the finite element method (FEM). The third one combines the finite element analysis with the generalised beam theory (GBT) in order to determine the modal participation of the FEM buckling mode and generate a particular combined geometric imperfection. To validate the predicted loads, the results of the three methodologies are compared with values obtained in experimental tests. http://hdl.handle.net/2117/12866 Title: Linear Buckling Analysis of Thin-Walled Members Combining the Generalised Beam Theory and the Finite Element Method Authors: Casafont Ribera, Miguel; Marimón Carvajal, Federico; Pastor Artigues, María Magdalena; Ferrer Ballester, Miquel Abstract: A finite element procedure to carry out linear buckling analysis of thin-walled members is developed on the basis of the existing Generalised Beam Theory (GBT) and constrained Finite Strip Method (cFSM). It allows designers to uncouple the buckling modes of a finite element model and, consequently, to calculate pure elastic buckling loads. The procedure can easily be applied to members with general boundary conditions subjected to compression or bending. The results obtained are rather accurate when compared to the values calculated via GBT and cFSM. As a consequence, it is demonstrated that linear buckling analyses can be performed with the Finite Element Method in a similar way as can be done with the existing GBT and cFSM procedures. Tue, 05 Jul 2011 07:12:44 GMT http://hdl.handle.net/2117/12866 2011-07-05T07:12:44Z Casafont Ribera, Miguel; Marimón Carvajal, Federico; Pastor Artigues, María Magdalena; Ferrer Ballester, Miquel no A finite element procedure to carry out linear buckling analysis of thin-walled members is developed on the basis of the existing Generalised Beam Theory (GBT) and constrained Finite Strip Method (cFSM). It allows designers to uncouple the buckling modes of a finite element model and, consequently, to calculate pure elastic buckling loads. The procedure can easily be applied to members with general boundary conditions subjected to compression or bending. The results obtained are rather accurate when compared to the values calculated via GBT and cFSM. As a consequence, it is demonstrated that linear buckling analyses can be performed with the Finite Element Method in a similar way as can be done with the existing GBT and cFSM procedures. http://hdl.handle.net/2117/12650 Title: Perfiles metálicos con secciones abiertas de pared delgada Authors: Roure Fernández, Francisco; Pastor Artigues, María Magdalena; Bonada Bo, Jordi; Casafont Ribera, Miguel; Minguella Canela, Joaquim Wed, 25 May 2011 14:37:27 GMT http://hdl.handle.net/2117/12650 2011-05-25T14:37:27Z Roure Fernández, Francisco; Pastor Artigues, María Magdalena; Bonada Bo, Jordi; Casafont Ribera, Miguel; Minguella Canela, Joaquim no http://hdl.handle.net/2117/12442 Title: An experimental investigation of distortional buckling of steel storage rack columns Authors: Casafont Ribera, Miguel; Pastor Artigues, María Magdalena; Roure Fernández, Francisco; Peköz, Teoman Mon, 02 May 2011 13:10:33 GMT http://hdl.handle.net/2117/12442 2011-05-02T13:10:33Z Casafont Ribera, Miguel; Pastor Artigues, María Magdalena; Roure Fernández, Francisco; Peköz, Teoman no http://hdl.handle.net/2117/12057 Title: L'Evolució dels mètodes de càlcul d'estructures durant el segle XX: dels mètodes gràfics a la irrupció dels computadors Authors: Pons Poblet, Josep Maria; Torres Llinars, Lluís Abstract: The methods of calculation used in engineering, and specifically in structural design, have experienced a great development throughout the 20th century. From the manual methodologies to the present systems, mainly based on computer calculations, they have increased of unimaginable way the calculation capacity, as well as the precision, reliability and speed of calculation. The methods at the beginning of the century, that followed the previous graphical methods, with which they coexisted a long time, gave rise to iterative systems for solving equations. These methodologies evolved with the appearance of first computers, and the increase of the capacity of calculation, memory and speed, lead to an increase of the degree of sophistication and complexity of the used methods. In this article the basic characteristics of the evolution of the methods of analysis of structures and its implications for the professional and educational world are exposed. This evolution is exemplified through three significant methods: the graphical methods, the Cross method and the Finite Element Method Thu, 24 Mar 2011 19:01:27 GMT http://hdl.handle.net/2117/12057 2011-03-24T19:01:27Z Pons Poblet, Josep Maria; Torres Llinars, Lluís no The methods of calculation used in engineering, and specifically in structural design, have experienced a great development throughout the 20th century. From the manual methodologies to the present systems, mainly based on computer calculations, they have increased of unimaginable way the calculation capacity, as well as the precision, reliability and speed of calculation. The methods at the beginning of the century, that followed the previous graphical methods, with which they coexisted a long time, gave rise to iterative systems for solving equations. These methodologies evolved with the appearance of first computers, and the increase of the capacity of calculation, memory and speed, lead to an increase of the degree of sophistication and complexity of the used methods. In this article the basic characteristics of the evolution of the methods of analysis of structures and its implications for the professional and educational world are exposed. This evolution is exemplified through three significant methods: the graphical methods, the Cross method and the Finite Element Method http://hdl.handle.net/2117/9554 Title: Stub column tests for racking design: Experimental testing, FE analysis and EC3 Authors: Roure Fernández, Francisco; Pastor Artigues, María Magdalena; Casafont Ribera, Miguel; Somalo Coarasa, María Rosa Abstract: The LaboratoryofElasticityandStrengthofMaterials,intheSchoolofEngineeringofBarcelona(UPC), has gainedawideexperienceinpallet-racktestinginrecentyears.Wehavegatheredacomprehensive set ofexperimentalresultsfromuprightcross-sectionssubjecttocompression.Twentydifferentpallet- rack steelprofileshavebeentested.Thisinformationisvaluableandallowsustoevaluatedifferent methodsalternativetotestingasadesignoption.Inthispaper,twoalternativemethodsareconsidered: the analytical,byapplyingtheEuropeanStandardEN1993-1-3:2006/AC:2009;atraditionalmethod, which involvestheeffectivewidthdeterminationforeachpartofthesectionsubjecttocompression; and thenumerical,byapplyingfiniteelementanalysis,includingnon-linearmaterialandgeometrical behaviour.Theresultsofbothmethodsarecomparedtotheexperimentalones.Thisresearchreveals that eventhoughtheEuropeanStandardEN15512:2009doesonlyaccepttheexperimentalmethodfor perforatedsections,thesesothertwomethodscangivegoodaccuracy,andbegoodtoolsinthestageof design andoptimization. Thu, 07 Oct 2010 16:59:21 GMT http://hdl.handle.net/2117/9554 2010-10-07T16:59:21Z Roure Fernández, Francisco; Pastor Artigues, María Magdalena; Casafont Ribera, Miguel; Somalo Coarasa, María Rosa no The LaboratoryofElasticityandStrengthofMaterials,intheSchoolofEngineeringofBarcelona(UPC), has gainedawideexperienceinpallet-racktestinginrecentyears.Wehavegatheredacomprehensive set ofexperimentalresultsfromuprightcross-sectionssubjecttocompression.Twentydifferentpallet- rack steelprofileshavebeentested.Thisinformationisvaluableandallowsustoevaluatedifferent methodsalternativetotestingasadesignoption.Inthispaper,twoalternativemethodsareconsidered: the analytical,byapplyingtheEuropeanStandardEN1993-1-3:2006/AC:2009;atraditionalmethod, which involvestheeffectivewidthdeterminationforeachpartofthesectionsubjecttocompression; and thenumerical,byapplyingfiniteelementanalysis,includingnon-linearmaterialandgeometrical behaviour.Theresultsofbothmethodsarecomparedtotheexperimentalones.Thisresearchreveals that eventhoughtheEuropeanStandardEN15512:2009doesonlyaccepttheexperimentalmethodfor perforatedsections,thesesothertwomethodscangivegoodaccuracy,andbegoodtoolsinthestageof design andoptimization. http://hdl.handle.net/2117/8556 Title: Experimental testing of joints for seismic design of lightweight structures: part 2: bolted joints in straps Authors: Casafont Ribera, Miguel; Arnedo Pena, Alfredo; Roure Fernández, Francisco; Rodríguez Ferran, Antonio Abstract: An experimental testing campaign on tensile bolted joints between straps is reported. Two dominant failure modes are identified: (1) tilting, bearing and tearing of the sheets (TS) and (2) tilting, bearing and net-section failure (NSF). The analysis in terms of ductility and strength shows that bolted connections are less adequate than screwed connections (reported in Part 1 of this paper) for the seismic design of X-braced shear walls in lightweight structures. NSF joints are more ductile than TS joints in the sense that they undergo larger displacements before failure. However, if washers are not used, both types of connections fail before energy dissipation through yielding of the diagonal straps can occur. Some design recommendations to improve the seismic performance of bolted joints, including the use of washers, are given. The accuracy of Eurocode 3 formulas to predict the ultimate load is also analyzed. Mon, 02 Aug 2010 12:20:54 GMT http://hdl.handle.net/2117/8556 2010-08-02T12:20:54Z Casafont Ribera, Miguel; Arnedo Pena, Alfredo; Roure Fernández, Francisco; Rodríguez Ferran, Antonio no Bearing, Ductility, Failure modes, Net-section failure, Light gauge steel, Lightweight steel, Seismic design, Joints, Bolts, Experimental research An experimental testing campaign on tensile bolted joints between straps is reported. Two dominant failure modes are identified: (1) tilting, bearing and tearing of the sheets (TS) and (2) tilting, bearing and net-section failure (NSF). The analysis in terms of ductility and strength shows that bolted connections are less adequate than screwed connections (reported in Part 1 of this paper) for the seismic design of X-braced shear walls in lightweight structures. NSF joints are more ductile than TS joints in the sense that they undergo larger displacements before failure. However, if washers are not used, both types of connections fail before energy dissipation through yielding of the diagonal straps can occur. Some design recommendations to improve the seismic performance of bolted joints, including the use of washers, are given. The accuracy of Eurocode 3 formulas to predict the ultimate load is also analyzed. http://hdl.handle.net/2117/8555 Title: Experimental testing of joints for seismic design of lightweight structures: part 1: screwed joints in straps Authors: Casafont Ribera, Miguel; Arnedo Pena, Alfredo; Roure Fernández, Francisco; Rodríguez Ferran, Antonio Abstract: Connections in x-braced shear walls play a crucial role in the seismic performance of lightweight structures: they should be strong enough to allow energy dissipation via plastification of the diagonal straps. An extensive experimental research on tensile screwed joints between straps is reported here. Two dominant failure modes are identified: (1) tilting and net section failure (T+NSF) and (2) tilting, bearing and pull out (T+B+PO). The analysis in terms of strength and ductility shows that T+NSF joints are suitable for seismic design, because the straps yield before the connections fail. T+B+PO joints, on the contrary, are not suited because the connection fails before the straps can yield. The influence of various design parameters (strap thickness, number and diameter of screws, steel grade) in the failure mode is studied, and design criteria to induce a T+NSF response are given. Mon, 02 Aug 2010 12:14:53 GMT http://hdl.handle.net/2117/8555 2010-08-02T12:14:53Z Casafont Ribera, Miguel; Arnedo Pena, Alfredo; Roure Fernández, Francisco; Rodríguez Ferran, Antonio no Failure modes, Net section failure, Bearing, Light gauge steel, Lightweight steel, Seismic design, Joints, Experimental research, Ductility Connections in x-braced shear walls play a crucial role in the seismic performance of lightweight structures: they should be strong enough to allow energy dissipation via plastification of the diagonal straps. An extensive experimental research on tensile screwed joints between straps is reported here. Two dominant failure modes are identified: (1) tilting and net section failure (T+NSF) and (2) tilting, bearing and pull out (T+B+PO). The analysis in terms of strength and ductility shows that T+NSF joints are suitable for seismic design, because the straps yield before the connections fail. T+B+PO joints, on the contrary, are not suited because the connection fails before the straps can yield. The influence of various design parameters (strap thickness, number and diameter of screws, steel grade) in the failure mode is studied, and design criteria to induce a T+NSF response are given. http://hdl.handle.net/2117/8165 Title: Experimental testing of joints for seismic design of lightweight structures. Part 3: gussets, corner joints, x-braced frames Authors: Casafont Ribera, Miguel; Arnedo Pena, Alfredo; Roure Fernández, Francisco; Rodríguez Ferran, Antonio Abstract: An experimental campaign on joints of x-braced frames is presented. Tests are performed on strap-gusset joints and lower and upper corner joints. Many different phenomena and failure modes are observed in these tests. However, it is possible to see that only one failure mode can be accepted if a good seismic performance of the frame needs to be guaranteed: the net-section failure of the diagonal strap after yielding. The results of the tests also allow to establish a set of recommendations for seismic design of joints. The effectiveness of these recommendations is verified by means of two final tests on complete x-braced frames. A full explanation on the behaviour of the joints and frames tested is included, together with a description of the special test set-up developed for the experimental campaign. Tue, 13 Jul 2010 16:51:48 GMT http://hdl.handle.net/2117/8165 2010-07-13T16:51:48Z Casafont Ribera, Miguel; Arnedo Pena, Alfredo; Roure Fernández, Francisco; Rodríguez Ferran, Antonio no An experimental campaign on joints of x-braced frames is presented. Tests are performed on strap-gusset joints and lower and upper corner joints. Many different phenomena and failure modes are observed in these tests. However, it is possible to see that only one failure mode can be accepted if a good seismic performance of the frame needs to be guaranteed: the net-section failure of the diagonal strap after yielding. The results of the tests also allow to establish a set of recommendations for seismic design of joints. The effectiveness of these recommendations is verified by means of two final tests on complete x-braced frames. A full explanation on the behaviour of the joints and frames tested is included, together with a description of the special test set-up developed for the experimental campaign. http://hdl.handle.net/2117/7465 Title: Optimization of cold-formed steel pallet racking cross-sections for flexural-torsional buckling with constraints on the geometry Authors: Pastor Artigues, María Magdalena; Casafont Ribera, Miguel; Chillarón Jordán, Eduardo; Lusa García, Amaia; Roure Fernández, Francisco; Somalo Coarasa, María Rosa Abstract: Starting from a comprehensive set of experimental test results of upright cross-sections in compression, this paper is focussed on how the section can be optimally designed to achieve the highest possible failure load in global buckling. The aim is to optimize a cross-section prototype shape with restrictions on its geometry attending to manufacturing feasibility and assembly constraints. The proposed scheme consists of maximizing the design strength with respect to flexural torsional buckling, according to European Standard prEN 15512:2008 [European Standard prEN 15512:2008. Steel static storage systems - Adjustable pallet racking systems - Principles for structural design] / Fédération Européenne de la Manutention [Fédération Européenne de la Manutention (Section X): The design of static steel pallet racking. FEM 10.2.02; August 2000] design recommendations. This is a bicriteria optimization problem which is solved by formulating a nonlinear mathematical program. Optimization is performed prior to the finite element method (FEM) nonlinear analysis of the solution design. The procedure herein presented has two advantages: on the one hand it considerably reduces the number of nonlinear analyses, and on the other it ensures that the best design is achieved. Tue, 01 Jun 2010 13:05:22 GMT http://hdl.handle.net/2117/7465 2010-06-01T13:05:22Z Pastor Artigues, María Magdalena; Casafont Ribera, Miguel; Chillarón Jordán, Eduardo; Lusa García, Amaia; Roure Fernández, Francisco; Somalo Coarasa, María Rosa no Starting from a comprehensive set of experimental test results of upright cross-sections in compression, this paper is focussed on how the section can be optimally designed to achieve the highest possible failure load in global buckling. The aim is to optimize a cross-section prototype shape with restrictions on its geometry attending to manufacturing feasibility and assembly constraints. The proposed scheme consists of maximizing the design strength with respect to flexural torsional buckling, according to European Standard prEN 15512:2008 [European Standard prEN 15512:2008. Steel static storage systems - Adjustable pallet racking systems - Principles for structural design] / Fédération Européenne de la Manutention [Fédération Européenne de la Manutention (Section X): The design of static steel pallet racking. FEM 10.2.02; August 2000] design recommendations. This is a bicriteria optimization problem which is solved by formulating a nonlinear mathematical program. Optimization is performed prior to the finite element method (FEM) nonlinear analysis of the solution design. The procedure herein presented has two advantages: on the one hand it considerably reduces the number of nonlinear analyses, and on the other it ensures that the best design is achieved.