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., Postprint (published version)

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., Postprint (published version)

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., Postprint (published version)

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.

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.

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.

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.

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., Postprint (published version)

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., Postprint (published version)