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Adequate mechanical properties make stainless steel an excellent construction material for structures. The current stainless steel European structural code EN1993-1-4 (2015) is largely based on provisions given for carbon steel EN1993-1-1 (2005) and does not establish specific design rules for the global analysis of stainless steel structures. Thus, the same classification criterion applies in both codes for sway and non-sway structures, as well as providing the same predicting expressions for the amplification of bending moments in basic structures, despite the considerable differences between the mechanical behaviour of these two materials. However, recent numerical research on stainless steel frames with H cross-sections by Walport et al. (2019) showed that the degradation of stiffness due to material nonlinearities considerably affects the response of stainless steel frames, causing greater deformations and increasing second order effects. In order to contribute to the optimal design of stainless steel structures, this paper investigates the influence of the nonlinear material response of stainless steel alloys on frame-type structures with Rectangular Hollow Sections based on the experimental results conducted by Arrayago et al. (2019), and the interaction of material and geometric nonlinearities., The authors acknowledge the funding from MINECO (Spain) under Project BIA2016-75678-R, AEI/FEDER, UE “Comportamiento estructural de pórticos de acero inoxidable. Seguridad frente a ac-ciones accidentales de sismo y fuego”. The first author would also like to acknowledge the financial support provided by FPI-MINECO PhD fellowship Ref. BES-2017-082958. The second author would like to acknowledge the financial support received funding from the European Union’s Horizon 2020 research and innovation pro-gramme under the Marie Sklodowska-Curie grant agreement No. 842395.

Current design standards for stainless steel such as ASCE 8-02 and EN 1993-1-4 prescribe provisions for the design of cross-sections and members that account for material nonlinearities and strain hardening, although these features are not considered in the global design of structures. Recent studies have highlighted the need of accounting for material nonlinearities in order to design efficient and safe stainless steel structures, and it is expected that the forthcoming versions of the standards will incorporate updated rules for the global design of these structures. To contribute to this field, this paper presents a Stiffness Reduction Method (SRM) for the in-plane design of stainless steel members and frames with stocky sections based on the prescriptions given in the next version of EN 1993-1-4. The proposed approach predicts the ultimate capacity and internal forces in stainless steel structures by performing a second-order elastic analysis in which the stiffnesses of the members are reduced by a set of factors defined in this paper to account for the effect of the spread of plasticity, residual stresses and member imperfections. The accuracy of the presented method is assessed for individual stainless steel structural members (columns, beams, and beam-columns) with different cross-sections and material properties, and for austenitic stainless steel portal frames, against numerical results obtained from nonlinear analyses conducted on finite element models. A comparison between the proposed approach and the Direct Analysis Method prescribed in the upcoming AISC 370 Specification is also provided, showing that the results are comparable in the two approaches., The research presented in this paper was developed in the frame of the Project BIA2016-75678-R, AEI/FEDER, UE “Comportamiento estructural de pórticos de acero inoxidable. Seguridad frente a acciones accidentales de sismo y fuego”, funded from the MINECO (Spain). The financial support received from the Spanish Ministry for Science, Innovation and Universities through the FPI-MINECO PhD fellowship Ref. BES-2017-082958 (I. González-de-León) and from the European Commission through the Marie Sklodowska-Curie grant agreement No. 842395 (I. Arrayago) is also gratefully acknowledged., Peer Reviewed

This material may be downloaded for personal use only. Any other use requires prior permission of the American Society of Civil Engineers. This material may be found at https://ascelibrary.org/doi/10.1061/%28ASCE%29ST.1943-541X.0003084., This paper summarises the background information and methodology used to derive a set of buckling curves proposed for cold-formed stainless steel columns and beams, incorporated in the recently revised SEI/ASCE 8-21 Specification. The study is based on experimental and numerical data collected from the literature on cold-formed stainless steel columns and beams featuring ASTM grades 304, 2101, 430, 404 and 443. Since most of the investigated specimens exhibited slender cross-sections, both the Effective Width Method (EWM) and the Direct Strength Method (DSM) are considered to account for the effect of interaction between global and local buckling on member strength. Buckling curves for flexural buckling and lateral-torsional buckling codified in current international standards are assessed based on the SEI/ASCE 8 reliability requirements, and new curves are derived accordingly. The proposed new buckling curves include expressions to account for the post-yielding capacity of stainless steel columns and the inelastic buckling resistance of cold-formed stainless steel beams. In addition, a new local buckling strength curve for members in flexure is proposed in the format of the DSM and shown to provide equivalent design resistances to the EWM., Funding for this investigation was received from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement No. 842395 (Project NewGeneSS)., Peer Reviewed

Steel structures can be consistently and efficiently designed using system-based design-by-analysis approaches such as the Direct Design Method. However, since direct design approaches lead to potentially lighter structural configurations, they can also result in larger deformations under service loads. Thus, greater attention may be required to serviceability limit states in structures designed using design-by-analysis approaches than for structures designed elastically at their ultimate limit state following current two-stage approaches, especially for materials showing highly nonlinear stress vs strain responses such as stainless steel alloys. With the aim of investigating the influence of allowing larger deformations in the ultimate limit state design of stainless steel structures, this paper presents an explicit analysis framework for assessing serviceability reliability at system level. Using this framework, the paper investigates the serviceability reliability of cold-formed stainless steel portal frames designed using the Direct Design Method for different load cases, including the gravity load and the combined gravity plus wind load combinations. The study considers six baseline frames covering the most common stainless steel families and international design frameworks (i.e., Eurocode, US and Australian frameworks), for which the reliability of vertical deflection and lateral drift serviceability limit states is investigated using advanced numerical simulations and First-Order Reliability Methods. From the comparison of the calculated average annual reliability indices and the relevant target reliabilities for the different design frameworks, it was found that the reliability of stainless steel frames appears to be adequate for the serviceability limit states investigated for the Eurocode, US and Australian frameworks., Peer Reviewed

Current structural codes for steel and stainless steel structures such as AISC 360-16, AISC 370-21, AS/NZS 4100 and Eurocode 3 are based on the traditional two-step member-based design approach, in which internal actions are first obtained from a structural analysis, usually elastic, and the strength of each member and connection is subsequently checked using a structural design standard. However, the most recent versions of these standards already incorporate preliminary versions of the direct, or one-step, system-based design alternative, which is based on the design-by-analysis concept and allows evaluating the strength of structures directly from numerical simulations, although the standards in their current form do not provide reliability requirements for structural systems. Therefore, it is necessary to build a rigorous structural reliability framework to investigate acceptable target reliability indices for structural systems and to provide adequate system safety factors and system resistance factors. While this framework has been developed based on advanced Finite Element analysis for hot-rolled and cold-formed carbon steel structures in recent years in the form of the Direct Design Method (DDM), the framework does not exist for stainless steel structures. This paper presents an extension of the DDM to the analysis of stainless steel structures, in which system reliability calibrations are presented for six stainless steel portal frames under gravity loads covering the three most common stainless steel families and different failure modes using advanced numerical simulations. From the derived reliability calibrations, suitable system safety factors and system resistance factors are proposed for the direct design of stainless steel frames in the European, US and Australian design frameworks under gravity loads., This project has Received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement No. 842395., Peer Reviewed

This file includes data on system vertical and lateral stiffness of stainless steel frames under gravity and gravity plus wind load scenarios obtained from the finite element simulations carried out on six stainless steel frames.

Data was generated using the general purpose finite element software ABAQUS and performing advanced nonlinear analyses. The database is comprised of ultimate load factors corresponding to different random samples of six different nominal stainless steel frames under gravity and wind load combinations. The values of the random variable assignments are given for each case.

The full details of the finite element model can be found in: Arrayago, I.; Rasmussen, K.J.R.; Zhang, H. System-based reliability analysis of stainless steel frames subjected to wind loads. "Structural Safety", July 2022, vol. 97, art. No. 102211. DOI: https://doi.org/10.1016/j.strusafe.2022.102211

Traditional member-based two-step design approaches included in current structural codes for steel structures, as well as more recent system-based direct-design alternatives, require building rigorous structural reliability frameworks for the calibration of partial coefficients (resistance factors) to achieve specified target reliability requirements. Key design parameters affecting the strength of structures and their random variations are generally modelled by nominal or characteristic values in design standards, which are combined with partial coefficients that need to be calibrated from measurements on real samples. While the statistical characterization of material and geometric properties of structural steels has been consolidated over the last decades, information about the characterization of structural stainless steels is virtually non-existent due to the limited pool of available data. Thus, this paper presents the basic ingredient for developing reliability frameworks for stainless steel structures and components by statistically characterizing the main random parameters affecting their strength through a comprehensive database collected from the literature. Based on the collected data, appropriate probabilistic models are proposed for geometric properties, material properties, imperfections and residual stresses of different stainless steel alloys and cross-section or product types. The data is equally applicable to member-based reliability analyses as described in existing codes and system-based analyses targeted at the direct-design of stainless steel structures by advanced analysis., This research project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement No. 842395. The time dedicated by numerous authors of referenced papers to provide additional data and information is also much appreciated., Peer Reviewed

This file includes finite element simulation data (ultimate load factors) carried out on 60 steel and stainless steel frames, including regular and irregular frame configurations with different section sizes. Ultimate load factors corresponding to different initial imperfection combinations are included.

In the process of developing the next generation of design standards for steel structures, most relevant international structural codes including AISC 360, AISC 370, AS/NZS 4100 and Eurocode 3 already incorporate preliminary versions of system-based design-by-analysis approaches that allow a direct evaluation of the strength of steel and stainless steel structures from advanced numerical simulations. As a result, recent research works have focused on building rigorous structural reliability frameworks to investigate acceptable target reliability indices for structural systems and to develop new design methods in conjunction with adequate system safety factors and system resistance factors. Although design recommendations exist for the direct design of hot-rolled and cold-formed steel structures based on advanced finite element analysis, the extension of the method to other materials such as stainless steel is under development. This paper is part of a research effort to build a reliability framework for stainless steel structures subject to different load combinations and presents the results of system reliability calibrations carried out on six stainless steel portal frames subjected to combined gravity and wind loads. The study covers the most common stainless steel families and three international design frameworks (i.e., Eurocode, US and Australian frameworks). From the reliability calibrations derived, suitable system safety factors and system resistance factors are proposed for the direct design of stainless steel frames under combined gravity and wind loads using advanced numerical simulations., The project leading to this research has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement No. 84239., Peer Reviewed

First Order Reliability Methods (FORM) have been used by specification committees in the reliability analyses required for the calibration of resistance and safety factors for the past 40 years. However, these methods are iterative, require input information that may not be readily available, and make comparisons between different approaches or design frameworks difficult. This paper presents a set of simplified equations to estimate reliability indices , resistance factors and partial safety factors based on simpler First Order Second Moment (FOSM) considerations for the US and Eurocode frameworks, which are particularized for different load cases, and on the semi-probabilistic approach prescribed in the Eurocode 0. The equations provide direct relationships between the reliability calibration results corresponding to different design frameworks, and can be used to estimate resistance factors as simple cross-checks for the US framework based on the partial safety factors derived for the Eurocode (or vice versa) from basic statistical input information and given target reliability, including when the data available in the literature is insufficient to perform FORM analyses. The accuracy of the proposed equations is assessed against reliability results derived using FORM techniques for an extensive database of steel and stainless steel frames subjected to gravity and combined gravity plus wind load cases collected from the literature, and limitations for their applicability are recommended. The results demonstrate that the set of equations proposed in this paper provides accurate estimations of the reliability index, resistance factors and partial safety factors and can assist specification committees in the process of calibrating suitable system factors., Peer Reviewed

The Continuous Strength Method (CSM) provides accurate cross-section resistance predictions since allowance is made for the partial spread of plasticity and the beneficial effects of strain hardening. Although CSM design provisions for different loading conditions are available, the method was limited to the determination of cross-sectional resistance until recent research by Arrayago et al. (2020) proposed a consistent new approach to the design of stainless steel hollow section members subjected to compression. Extension of the CSM to the design of stainless steel members subjected to combined compression and bending moment is presented in this paper. The analysis is based on numerical results generated in the current study and existing results collected from the literature on stainless steel hollow section members. The results demonstrate that the adoption of the CSM design equations to predict column strength considerably improves the ac-curacy of the calculated beam-column capacities. The reliability of the proposed approach is demonstrated through statistical analyses performed in accordance with EN 1990., The authors acknowledge the funding from the MINECO (Spain) under Project BIA2016-75678-R, AEI/FEDER, UE “Comportamiento estructural de pórticos de acero inoxidable. Seguridad frente a acciones accidentales de sismo y fuego”. The first author would also like to acknowledge the financial support received from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 842395.

Current codes for steel structures, including AISC 360-10, AS4100 and Eurocode 3, are in the process of evolving from the current member-based design method to direct system-based approaches that allow evaluating the strength of structures directly from numerical simulations. However, these codes do not provide adequate safety factors nor reliability requirements for structural systems. Thus, it is necessary to build a rigorous structural reliability framework to investigate acceptable target reliability indices for structural systems and to provide adequate system safety factors. While this framework has been developed based on advanced Finite Element analysis for carbon steel structures in recent years in the form of the Direct Design Method (DDM), it does not exist for stainless steel structures. This paper presents the first step towards developing a system-based reliability framework for stainless steel structures by providing statistical distributions of the key parameters governing the strength of systems composed of stainless steel cold-formed hollow sections. The distributions are based on a comprehensive database collected from the literature including data on the main sources of uncertainty: geometric properties, imperfections and material parameters., The project leading to this research has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement No. 842395.

Austenitic stainless steels offer a suitable combination of high ductility, adequate toughness, considerable strain hardening and good fire resistance, making them excellent construction materials, especially for structures subjected to accidental loading such as seismic and/or fire events. With most of the research over the recent years devoted to the behaviour of single isolated stainless steel members, advances on structural systems are scarce, yet necessary, for the further development of design codes. Hence, an extensive experimental programme on EN 1.4301 austenitic stainless steel frames including tests at different structural levels –material, cross-section, member and frame levels– has been carried out at the Laboratory of Technology of Structures and Materials at Universitat Politècnica de Catalunya. The companion paper presents the tests carried out at cross-section and member level, and the knowledge gained from the planning of the experimental set-up for frame tests, including the adopted loading schemes, auxiliary elements and instrumentation. This paper presents the results of the four tests conducted on austenitic stainless steel frames under static vertical and horizontal loading. The analysis of the test results allowed to investigate the interaction of material and geometrical nonlinearities experimentally, as well as the assessment of the EN 1993-1-4 and EN 1993-1-1 provisions for the global analysis of stainless steel frames, where the influence of material nonlinearity on second order effects is evaluated, and which is currently limited to numerical studies only., "This experimental programme was developed in the frame of the Project BIA2016-75678-R, AEI/FEDER, UE “Comportamiento estructural de pórticos de acero inoxidable. Seguridad frente a acciones accidentales de sismo y fuego”, funded from the MINECO (Spain). The financial support received from the European Commission and Spanish Ministry for Science, Innovation and Universities through the Marie Sklodowska-Curie grant agreement No. 842395 and the FPI-MINECO PhD. fellowship Ref. BES-2017-082958 is also gratefully acknowledged.
Authors would like to acknowledge the support, advice and suggestions from Professor K. Rasmussen (The University of Sydney), Professor B. Young (Hong Kong University) and Professor L. Gardner (Imperial College London) in the preparation of this experimental programme, and the support from Acerinox and MeKano4. The time and effort from the staff at the Laboratory of Technology of Structures and Materials and the Geotechnical Engineering and Geosciences Department from Universitat Politècnica de Catalunya are also much appreciated.", Peer Reviewed

Acknowledging the potential of system-based design approaches, most international design standards for steel structures include preliminary versions of such alternative design methods. The Direct Design Method (DDM) is one of these approaches, which allows designing steel structures directly using advanced numerical analyses without requiring further member checks. This paper presents the DDM design (and verification) procedure and summarizes the key aspects of the advanced finite element model necessary for the determination of the system strength, with an emphasis on cold-formed stainless steel portal frames. Through the design of two frames, the DDM design procedure is illustrated and the resulting cross-sections are compared with those derived using the traditional two-step design approach in the Eurocode and ASCE design frameworks. The results demonstrate that the DDM verification process is simpler and more direct, and that lighter structures are obtained when designing using the DDM for strength considerations. Finally, this paper also highlights that allowing larger deformations in the ultimate limit state design for the DDM does not have additional negative effects on the serviceability requirements if compared to the traditional two-step design approach., The project leading to this research has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement No. 842395.

Austenitic stainless steel is an excellent construction material for structures required to withstand accidental loads such as seismic and/or fire events due to its appropriate mechanical properties, including high ductility, considerable strain hardening and good fire resistance. In recent years, a considerable amount of research has been devoted to the understanding of the structural performance of single isolated stainless steel members. However, new trends in the design philosophy moving from current member-based methods to direct system-based approaches will require more experimental evidence on more complex structural systems such as frames, which are currently scarce. With the aim of contributing to the advances in this field, one of the first known extensive experimental programmes on austenitic stainless steel frames is presented in this paper. The experimental programme comprised several sub-programmes, in which the performance of stainless steel structures at different levels was investigated. This paper describes a series of tests on austenitic stainless steel cross-sections and members, which were utilized in the planning and analysis of the subsequent frame tests. The paper also outlines the complex experimental set-up adopted for the stainless steel frame tests, including the implemented loading schemes, auxiliary elements and instrumentation, through a detailed explanation of the different issues encountered in the process of their definition. The knowledge gained and the experiences reported in this paper could assist researchers in planning similar experimental programmes., "This experimental programme was developed in the frame of the Project BIA2016-75678-R, AEI/FEDER, UE “Comportamiento estructural de pórticos de acero inoxidable. Seguridad frente a acciones accidentales de sismo y fuego”, funded from the MINECO (Spain). The financial support received from the European Commission and Spanish Ministry for Science, Innovation and Universities through the Marie Sklodowska-Curie grant agreement No. 842395 and the FPI-MINECO PhD fellowship Ref. BES-2017-082958 is also gratefully acknowledged.
Authors would like to acknowledge the support, advice and suggestions from Professor K. Rasmussen (The University of Sydney), Professor B. Young (Hong Kong University) and Professor L. Gardner (Imperial College London) in the preparation of this experimental programme, and the support from Acerinox and MeKano4. The time and effort from the staff at the Laboratory of Technology of Structures and Materials and the Geotechnical Engineering and Geosciences Department from Universitat Politècnica de Catalunya are also much appreciated.", Peer Reviewed

This file includes data used in the calibration of statistical models for the different random variables affecting stainless steel members.
This data was used in the analysis carried out and reported in the publication:
Arrayago I., Rasmussen K.J.R., Real E.
Statistical analysis of the material, geometrical and imperfection characteristics of structural stainless steels and members
Journal of Constructional Steel Research 175, 106378, 2020.
DOI: https://doi.org/10.1016/j.jcsr.2020.106378

Measured and nominal values are listed for geometry-related data.
Measured values are listed for material, imperfection and residual stress data.

This file includes data on system strength of stainless steel frames under gravity loads obtained from the finite element simulations carried out on six stainless steel frames.

This data was used in the analysis carried out and reported in the publication:

Input and output data is provided separately for each of the six frames investigated.

Frames 1 and 2 correspond to austenitic stainless steel, Frames 3 and 4 to duplex stainless steel and Frames 5 and 6 to ferritic stainless steel.

This document includes the pre-normative recommendations developed in the NewGeneSS research project for the design of stainless steel frames using advanced analysis, The research project NewGeneSS, the acronym of “NEW GENEration design methods for Stainless steel Structures” was financed by the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Actions (2018). The NewGeneSS project aimed at developing the basis of system-based direct design approaches for stainless steel structures in the European framework by calibrating suitable system safety factors from rigorous structural reliability considerations, and at delivering the pre-normative design recommendations included in this document., The project leading to this document has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement No. 842395 (NewGeneSS project).

System-based direct design approaches are poised to become the design method of the future. They do not only make the design of structures using advanced structural analysis possible, without requiring any further member resistance checks, but they also allow for the full exploitation of the load redistribution capacity, redundancy and robustness of structures when considering these as whole systems. The widespread and implementation of system-based design approaches require, however, the calibration of suitable system resistance factors to be incorporated in the next generation of structural standards to guarantee the reliability of the method. While system resistance factors have been already proposed in the literature for different types of steel structures in the US (ASCE) and Australian design frameworks, the extension of the method to other materials and design frameworks such as stainless steel alloys and the Eurocode was still lacking until recently. The development of the system-based direct design approaches for stainless steel frames for the Eurocode, ASCE and Australian design frameworks has been addressed in the NewGeneSS project, an overview of which is provided herein. This paper presents a summary of the reliability framework and advanced finite element models developed, as well as of the structural reliability analyses carried out for the calibration of suitable system resistance and safety factors for different loading conditions. Additional considerations concerning the serviceability limit state of the frames, the comparison with the traditional two-step design methods and the development of pre-normative design recommendations are also presented., The project leading to this research has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement No. 842395.