Pallet rack structures are usually made up of thin walled cold formed steel sections. The cold ro... more Pallet rack structures are usually made up of thin walled cold formed steel sections. The cold rolling process changes the material properties, increasing the yield strength and tensile strength across the section. According to EN1993-1-3, an equivalent yielding strength is allowed to be considered in design to account for the changes in material properties. It has to be mentioned that this approach does not take into account the residual stresses that arise following the forming process. The current paper presents the experimental evidence of residual stresses as result cold rolling process for two pallet rack upright sections. Based on experimental findings, a series of numerical models were created in order investigate the influence of residual stresses onto the load bearing capacity of pallet rack uprights. The experimental program was developed within the CEMSIG Research Centre (http://cemsig.ct.upt.ro) of " Politehnica " University of Timisoara. The increase of yield strength and tensile strength across the cross-section was also experimentally determined.
An imperfection sensitivity analysis of cold-formed steel members in compression is presented. Th... more An imperfection sensitivity analysis of cold-formed steel members in compression is presented. The analysis is based on Koiter’s approach and Monte Carlo simulation. Mode interaction is correctly accounted and limit load and erosion of critical buckling load evaluated. Thousand of imperfection can be analysed with very low computational cost and an effective statistical evaluation of limit performance can be carried out.
Abstract: The present paper compares overstrength demands on non-dissipative memebers in three se... more Abstract: The present paper compares overstrength demands on non-dissipative memebers in three seismic design codes: P100-1/2006 (RO), EN 1998 (EU) and AISC 341-05 (USA) based on the analysis of a multistory eccentrically braced frame. The structural behavior ...
This paper analyses the interactive buckling behaviour of compression members used for steel pall... more This paper analyses the interactive buckling behaviour of compression members used for steel pallet racks. Recently, the proposed rack members were thoroughly analyzed at CEMSIG Research Centre of “Politehnica” University of Timisoara. Following the guidelines of EN15512, the authors of this study performed experimental and numerical testing on a large number of specimens with lengths carefully chosen in order to capture the lower critical loads related with pure Local, Distortional buckling and also with the interactive Distortional-Global buckling usually met in practice for this type of sections. The aim of the presented paper is to quantify the Local-Distortional-Global (L-D-G) modes participation in the linear buckling shapes, assessing with high precision if the methods used for choosing the members lengths for experimental analyses, are valid. For this reason, an original modal identification method, based on the Generalised Beam Theory (GBT), is applied, providing the pure m...
ABSTRACT Global buckling behaviour, with or without interaction with distortional buckling, of st... more ABSTRACT Global buckling behaviour, with or without interaction with distortional buckling, of storage rack members is evaluated by tests carried out according to EN 15512 (2009) [1] on compression and out-of-plane bending of upright frame modules. Based on test results for both single upright sections and frame modules, completed by numerical simulation, the present paper attempts to demonstrate that the design buckling strength of uprights can be conveniently estimated by single section tests, providing that the length of these members is calibrated for the distortional–global interaction mode.
This paper investigates the behaviour of different types of cold-formed steel members in compress... more This paper investigates the behaviour of different types of cold-formed steel members in compression of built-up back-to-back lipped channel cross-sections. Previous research on specimens in compression, made by Rondal and Niazi (1992, 1993) based on the formulas given by Johnston (1971) for spaced hot-rolled columns in which the battens (e.g. stitches) are attached to the chords by hinged connections, have provided recommendations to calculate the buckling resistance of such cold-formed built-up members; these are the only existing design recommendations for such specimens. Dubina et al. (2002b) reconfirmed, via numerical investigations, the analytical formula proposed by Rondal and Niazzi. In case of members in bending there are no particular design rules excepting the fact the distances between stitches must be appropriately sized in order to comply with built-up section conditions. Three types of back-to-back lipped channel cross-sections will be investigated, e.g. (a) back-to-back cold-formed steel columns connected with bolts; (b) back-to-back cold-formed steel columns connected with bolts and gussets; (c) back-to-back cold-formed steel columns connected with bolts, using stitches.
Present paper presents specific aspects of the design, operation, evaluation and maintenance of h... more Present paper presents specific aspects of the design, operation, evaluation and maintenance of hyperbaric pressure vessels designed to operate with an internal pressure of over 30 bars. Considerations regarding the effects of cuttings for manholes, stress concentration and fatigue assessment, in the design stage, the heat affected zones, residual stress due to welding, alignment and/or planeity of manholes during the construction stage and the evaluation of fatigue induced by cyclic loading and required tests during the operation of such structures are also presented. Moreover, the final part of the paper underlines a series of proposed methods that could be used to better quantify and evaluate the life span of such structures without the need of costly and time consuming in-field tests. In addition, the proposed methods are desired to reduce the number of incursions in the plastic range in high stress concentration areas.
Eurocode specifies that, for plastic hinges in beams it should be verified the full plastic momen... more Eurocode specifies that, for plastic hinges in beams it should be verified the full plastic moment of resistance and rotation capacity are not decreased by compression or shear forces. For current moment resisting frames, low values of shear to shear capacity or axial force to axial capacity were observed in comparison to bending moment ratio. For these cases, the influence of shear and axial force on bending moment and rotation capacity of moment plastic hinges can be ignored. However, there are some cases, when the lateral force-resisting system is composed by close-spaced columns rigidly connected by beams. These beams are long enough to allow for the development of moment plastic hinges at the ends, but they are also sufficiently short to create a significantly shear forces to influence the bending moment and rotation capacity of the beam.
The paper presents a parametric study using an experimentally calibrated numerical model carried out at Department of Steel Structures and Structural Mechanics of Politehnica University Timisoara on the purpose to observe and characterize the plastic mechanism of short steel beams with Reduced
Beam Section (RBS) applied in Moment Resisting Frames. Such a solution was applied to design a multi-story building structure in Bucharest, were the structural designer aimed to get a good
dissipative behaviour under seismic actions in the plastic hinges expected to form in the RBS zones of the short beams of the frames. An experimental confirmation of this solution was asked and validity of plastic hinge model, applied in global analysis, to be checked. In case, an interaction
model between bending moment and shear force had to be calibrated. A synthesis of the main result of this investigation is presented, including main experimental and numerical investigations, and, at the end, a simplified interaction model, compatible with SAP2000 is proposed, enabling for non-linear analysis in practical design.
Pallet rack structures are usually made up of thin walled cold formed steel sections. The cold ro... more Pallet rack structures are usually made up of thin walled cold formed steel sections. The cold rolling process changes the material properties, increasing the yield strength and tensile strength across the section. According to EN1993-1-3, an equivalent yielding strength is allowed to be considered in design to account for the changes in material properties. It has to be mentioned that this approach does not take into account the residual stresses that arise following the forming process. The current paper presents the experimental evidence of residual stresses as result cold rolling process for two pallet rack upright sections. Based on experimental findings, a series of numerical models were created in order investigate the influence of residual stresses onto the load bearing capacity of pallet rack uprights. The experimental program was developed within the CEMSIG Research Centre (http://cemsig.ct.upt.ro) of " Politehnica " University of Timisoara. The increase of yield strength and tensile strength across the cross-section was also experimentally determined.
An imperfection sensitivity analysis of cold-formed steel members in compression is presented. Th... more An imperfection sensitivity analysis of cold-formed steel members in compression is presented. The analysis is based on Koiter’s approach and Monte Carlo simulation. Mode interaction is correctly accounted and limit load and erosion of critical buckling load evaluated. Thousand of imperfection can be analysed with very low computational cost and an effective statistical evaluation of limit performance can be carried out.
Abstract: The present paper compares overstrength demands on non-dissipative memebers in three se... more Abstract: The present paper compares overstrength demands on non-dissipative memebers in three seismic design codes: P100-1/2006 (RO), EN 1998 (EU) and AISC 341-05 (USA) based on the analysis of a multistory eccentrically braced frame. The structural behavior ...
This paper analyses the interactive buckling behaviour of compression members used for steel pall... more This paper analyses the interactive buckling behaviour of compression members used for steel pallet racks. Recently, the proposed rack members were thoroughly analyzed at CEMSIG Research Centre of “Politehnica” University of Timisoara. Following the guidelines of EN15512, the authors of this study performed experimental and numerical testing on a large number of specimens with lengths carefully chosen in order to capture the lower critical loads related with pure Local, Distortional buckling and also with the interactive Distortional-Global buckling usually met in practice for this type of sections. The aim of the presented paper is to quantify the Local-Distortional-Global (L-D-G) modes participation in the linear buckling shapes, assessing with high precision if the methods used for choosing the members lengths for experimental analyses, are valid. For this reason, an original modal identification method, based on the Generalised Beam Theory (GBT), is applied, providing the pure m...
ABSTRACT Global buckling behaviour, with or without interaction with distortional buckling, of st... more ABSTRACT Global buckling behaviour, with or without interaction with distortional buckling, of storage rack members is evaluated by tests carried out according to EN 15512 (2009) [1] on compression and out-of-plane bending of upright frame modules. Based on test results for both single upright sections and frame modules, completed by numerical simulation, the present paper attempts to demonstrate that the design buckling strength of uprights can be conveniently estimated by single section tests, providing that the length of these members is calibrated for the distortional–global interaction mode.
This paper investigates the behaviour of different types of cold-formed steel members in compress... more This paper investigates the behaviour of different types of cold-formed steel members in compression of built-up back-to-back lipped channel cross-sections. Previous research on specimens in compression, made by Rondal and Niazi (1992, 1993) based on the formulas given by Johnston (1971) for spaced hot-rolled columns in which the battens (e.g. stitches) are attached to the chords by hinged connections, have provided recommendations to calculate the buckling resistance of such cold-formed built-up members; these are the only existing design recommendations for such specimens. Dubina et al. (2002b) reconfirmed, via numerical investigations, the analytical formula proposed by Rondal and Niazzi. In case of members in bending there are no particular design rules excepting the fact the distances between stitches must be appropriately sized in order to comply with built-up section conditions. Three types of back-to-back lipped channel cross-sections will be investigated, e.g. (a) back-to-back cold-formed steel columns connected with bolts; (b) back-to-back cold-formed steel columns connected with bolts and gussets; (c) back-to-back cold-formed steel columns connected with bolts, using stitches.
Present paper presents specific aspects of the design, operation, evaluation and maintenance of h... more Present paper presents specific aspects of the design, operation, evaluation and maintenance of hyperbaric pressure vessels designed to operate with an internal pressure of over 30 bars. Considerations regarding the effects of cuttings for manholes, stress concentration and fatigue assessment, in the design stage, the heat affected zones, residual stress due to welding, alignment and/or planeity of manholes during the construction stage and the evaluation of fatigue induced by cyclic loading and required tests during the operation of such structures are also presented. Moreover, the final part of the paper underlines a series of proposed methods that could be used to better quantify and evaluate the life span of such structures without the need of costly and time consuming in-field tests. In addition, the proposed methods are desired to reduce the number of incursions in the plastic range in high stress concentration areas.
Eurocode specifies that, for plastic hinges in beams it should be verified the full plastic momen... more Eurocode specifies that, for plastic hinges in beams it should be verified the full plastic moment of resistance and rotation capacity are not decreased by compression or shear forces. For current moment resisting frames, low values of shear to shear capacity or axial force to axial capacity were observed in comparison to bending moment ratio. For these cases, the influence of shear and axial force on bending moment and rotation capacity of moment plastic hinges can be ignored. However, there are some cases, when the lateral force-resisting system is composed by close-spaced columns rigidly connected by beams. These beams are long enough to allow for the development of moment plastic hinges at the ends, but they are also sufficiently short to create a significantly shear forces to influence the bending moment and rotation capacity of the beam.
The paper presents a parametric study using an experimentally calibrated numerical model carried out at Department of Steel Structures and Structural Mechanics of Politehnica University Timisoara on the purpose to observe and characterize the plastic mechanism of short steel beams with Reduced
Beam Section (RBS) applied in Moment Resisting Frames. Such a solution was applied to design a multi-story building structure in Bucharest, were the structural designer aimed to get a good
dissipative behaviour under seismic actions in the plastic hinges expected to form in the RBS zones of the short beams of the frames. An experimental confirmation of this solution was asked and validity of plastic hinge model, applied in global analysis, to be checked. In case, an interaction
model between bending moment and shear force had to be calibrated. A synthesis of the main result of this investigation is presented, including main experimental and numerical investigations, and, at the end, a simplified interaction model, compatible with SAP2000 is proposed, enabling for non-linear analysis in practical design.
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Papers by Andrei Crisan
lipped channel cross-sections. Previous research on specimens in compression, made by Rondal and Niazi (1992, 1993) based on the
formulas given by Johnston (1971) for spaced hot-rolled columns in which the battens (e.g. stitches) are attached to the chords by hinged connections, have provided recommendations to calculate the buckling resistance of such cold-formed built-up members; these are the only existing design recommendations for such specimens. Dubina et al. (2002b) reconfirmed, via numerical investigations, the analytical formula proposed by Rondal and Niazzi. In case of members in bending there are no particular design rules excepting the fact the distances between stitches must be appropriately sized in order to comply with built-up section conditions. Three types of back-to-back lipped channel cross-sections will be investigated, e.g. (a) back-to-back cold-formed steel columns connected with bolts; (b) back-to-back cold-formed steel columns connected with bolts and gussets; (c) back-to-back cold-formed steel columns connected with bolts, using stitches.
planeity of manholes during the construction stage and the evaluation of fatigue induced by cyclic loading and required tests during the operation of such structures are also presented. Moreover, the final part of the paper underlines a series of proposed methods that
could be used to better quantify and evaluate the life span of such structures without the need of costly and time consuming in-field tests. In addition, the proposed methods are desired to reduce the number of incursions in the plastic range in high stress concentration areas.
The paper presents a parametric study using an experimentally calibrated numerical model carried out at Department of Steel Structures and Structural Mechanics of Politehnica University Timisoara on the purpose to observe and characterize the plastic mechanism of short steel beams with Reduced
Beam Section (RBS) applied in Moment Resisting Frames. Such a solution was applied to design a multi-story building structure in Bucharest, were the structural designer aimed to get a good
dissipative behaviour under seismic actions in the plastic hinges expected to form in the RBS zones of the short beams of the frames. An experimental confirmation of this solution was asked and validity of plastic hinge model, applied in global analysis, to be checked. In case, an interaction
model between bending moment and shear force had to be calibrated. A synthesis of the main result of this investigation is presented, including main experimental and numerical investigations, and, at the end, a simplified interaction model, compatible with SAP2000 is proposed, enabling for non-linear analysis in practical design.
lipped channel cross-sections. Previous research on specimens in compression, made by Rondal and Niazi (1992, 1993) based on the
formulas given by Johnston (1971) for spaced hot-rolled columns in which the battens (e.g. stitches) are attached to the chords by hinged connections, have provided recommendations to calculate the buckling resistance of such cold-formed built-up members; these are the only existing design recommendations for such specimens. Dubina et al. (2002b) reconfirmed, via numerical investigations, the analytical formula proposed by Rondal and Niazzi. In case of members in bending there are no particular design rules excepting the fact the distances between stitches must be appropriately sized in order to comply with built-up section conditions. Three types of back-to-back lipped channel cross-sections will be investigated, e.g. (a) back-to-back cold-formed steel columns connected with bolts; (b) back-to-back cold-formed steel columns connected with bolts and gussets; (c) back-to-back cold-formed steel columns connected with bolts, using stitches.
planeity of manholes during the construction stage and the evaluation of fatigue induced by cyclic loading and required tests during the operation of such structures are also presented. Moreover, the final part of the paper underlines a series of proposed methods that
could be used to better quantify and evaluate the life span of such structures without the need of costly and time consuming in-field tests. In addition, the proposed methods are desired to reduce the number of incursions in the plastic range in high stress concentration areas.
The paper presents a parametric study using an experimentally calibrated numerical model carried out at Department of Steel Structures and Structural Mechanics of Politehnica University Timisoara on the purpose to observe and characterize the plastic mechanism of short steel beams with Reduced
Beam Section (RBS) applied in Moment Resisting Frames. Such a solution was applied to design a multi-story building structure in Bucharest, were the structural designer aimed to get a good
dissipative behaviour under seismic actions in the plastic hinges expected to form in the RBS zones of the short beams of the frames. An experimental confirmation of this solution was asked and validity of plastic hinge model, applied in global analysis, to be checked. In case, an interaction
model between bending moment and shear force had to be calibrated. A synthesis of the main result of this investigation is presented, including main experimental and numerical investigations, and, at the end, a simplified interaction model, compatible with SAP2000 is proposed, enabling for non-linear analysis in practical design.