•Longitudinal shear resistance of stainless steel composite slabs via experiments.•The Partial Shear Connection (PSC) method is applied.•The design value of the longitudinal shear resistance τu,Rd ...for stainless steel composite slabs is given.•The ultimate resistance is compared to the one of slabs made of galvanized steel.
Steel-concrete composite floors are commonly used in construction due to their favourable weight-to-depth ratio and erection time. Typically, concrete is poured onto a galvanised steel deck acting as formwork. However in case of floors exposed to corrosive environments, stainless steel is likely to be chosen over galvanised steel. Besides its better corrosion resistance, stainless steel also offers desirable aesthetic appearance and good mechanical properties. Composite slabs can fail in bending, vertical shear or longitudinal shear. The latter failure mode is the most common, and its prediction depends on values obtained through full-scale tests. However, for stainless steel decks, no specific treatment exists in current design standards. This paper investigates the longitudinal shear resistance of stainless steel composite slabs through an experimental study. One short and three long span slabs, made using a Cofraplus 60 ferritic EN1.4003 stainless steel corrugated deck, are tested in accordance with Eurocode 4, annex B.3 1. The Partial Shear Connection (PSC) method is used to assess the longitudinal shear resistance. The experimental results, together with the results provided in Task 3.3 of the “Structural Applications of Ferritic Stainless Steels (SAFSS, RFSR-CT-2010-00026)” project 2, are used to draw conclusions on the applicability of ferritic stainless steel decks in composite floors.
•This paper presents a comprehensive numerical study on curved steel plate I-girders subjected to patch loading.•The results obtained from FE analyses were verified against experimental results.•The ...ultimate load decreases in curved I-girders when the radius of curvature decreases.•Practical recommendations are proposed to the applicability of the design provisions prescribed in EN 1993-1-5 for straight girders to curved I-girders.
Curved steel plate girders are often utilized in bridges built in congested urban areas, where intricate plan alignments are required. Their performance and design is, however, more complex than that of equivalent straight girders, especially regarding concentrated forces: while AASHTO adopts a simplified and empirical approach for the design of curved steel girders, the Eurocode for plated structures EN 1993-1-5 does not address the patch loading design of steel plate girders curved in plan, being only applicable to straight girders. Therefore, it is necessary to carry out further research in order to achieve a better understanding of the behavior of curved steel plate girders so that suitable design approaches accounting for the specific response of these structures can be developed. This paper presents a comprehensive numerical study on curved steel plate I-girders subjected to patch loading, considering material and geometric nonlinearities as well as initial imperfections. The numerical models are developed by means of the advanced finite element software ABAQUS and validated against experimental tests available in the literature. The numerical results demonstrate that the elastic critical buckling loads increase with increasing span-to-plan radii, which can be conservatively estimated using the EN 1993-1-5 provisions for straight steel girders, and that the ultimate patch loading resistance decreases with the radius of curvature. Based on this, practical recommendations are proposed to extend the applicability of the design provisions prescribed in the next version of EN 1993-1-5 for straight steel I-girders to the case of curved steel I-girders.
Stainless steel frames with compact cross-sections are capable of redistributing internal forces at room temperature and forming plastic failure mechanisms, which is reflected in the new generation ...of structural codes for stainless steel by allowing to carry out global plastic analyses on certain types of stainless steel if the joints conforming the structure are classified as full-strength joints. Nevertheless, the requirements for the fire design of stainless steel structures in current standards is still primarily based on the resistance of individual members, disregarding strain hardening effects and the redistribution of internal forces, mainly because the influence of the performance of stainless steel joints on the response of the frames under fire situation is yet unknown. On this basis, this paper presents a numerical study focused on stainless steel frames with compact rectangular hollow sections, both at room temperature and at elevated temperatures, to analyse the influence of full-strength joints on the frame's response by means of two joint modelling techniques, and to assess the plastic redistribution capacity of stainless steel frames, especially under fire situation. In addition, an exhaustive revision of the failure criteria for stainless steel frames under fire situation is carried out and a new failure criterion is proposed based on the results derived from the parametric study. The results demonstrate that stainless steel frames are also capable of redistributing internal forces and forming plastic collapse mechanisms under fire situations, suggesting a new procedure to predict the response of these structures under fire situation more accurately.
•A comprehensive parametric study on stainless steel frames is carried out at room and elevated temperatures.•The plastic redistribution capacity of stainless steel frames is investigated numerically.•The influence of the joint modelling technique on the performance of the frames is analysed.•Revised failure criteria are proposed for stainless steel structures under fire situation.•Stainless steel frames are found to be capable of redistributing internal forces and form plastic mechanisms under fire.
In this paper, the flexural response of extruded wrought aluminium girders is presented. This structural element is intended for usage in marine structures such as light docks, marinas and yacht ...ports. Ease of use, durability, reduced weight, manoeuvrability and the potential development of bespoke sections are appealing properties in such structures that are fulfilled satisfactorily by this type of aluminium elements. Both experimental and numerical analyses are presented. Experimentally, modules of the girders are tested with loading about both minor and major axes. Numerically, the tests are satisfactorily reproduced for the sake of validation and a subsequent exploitation of the model is addressed for further study of the structural response of the girders. A discussion of the results is presented with some design recommendations of these particular structural elements.
•The flexural response of extruded wrought aluminium girders is presented.•Bespoke cross-section according to operational needs are studied.•These elements are intended for usage in light marine structures.•Both experimental and numerical analyses are presented.
Initial geometric imperfections are unavoidable in steel members and frames due to erection and manufacturing tolerances. These include frame out-of-plumbness, member out-of-straightness and ...cross-sectional imperfections, and can have a significant influence on the response and resistance of steel structures. Thus, they need to be accounted for in the analysis and design of steel structures, especially when advanced design procedures are adopted. One of the easiest approaches to introduce geometric imperfections in structural finite element models is through the linear superposition of scaled eigenmodes, which are obtained from a priori elastic buckling analysis. Although the shape and magnitude of frame and member imperfections are specified in international standards, the rules for the combination of different types and directions of imperfections are unclear or impractical, and often require designers to consider many possible combinations to find the critical, or “worst case”, shape of the imperfection including the direction of each eigenmode. This paper investigates the influence of the direction of modes contributing to the imperfection on the ultimate load (i.e., resistance) of steel frames when using advanced analysis. Ultimate loads are estimated from advanced finite element simulations for 20 regular and irregular unbraced frames featuring steel and austenitic stainless steel compact sections, in which initial imperfections are modelled as linear superpositions of six scaled buckling modes considering all possible combinations of direction. The results show that the influence of the imperfection direction on the ultimate frame load is small, and that assuming a combination of all buckling modes with positive amplitudes provides a simple and accurate estimation of the critical imperfection combination.
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•Influence of the imperfection direction on the strength of steel frames is investigated.•Imperfections are modelled as a linear superposition of six scaled buckling modes.•Different regular and irregular steel and stainless steel frames with compact sections are examined.•Ultimate load factors for all possible direction combinations are obtained and compared.•The notion of worst case imperfection is challenged.
•Extension of the CSM to the stability design of stainless steel beam-columns is presented.•Accuracy of the CSM for beam-columns is assessed against experimental and FE data.•The CSM is more accurate ...than current provisions for members with stocky cross-sections.•The CSM is consistent with current provisions for members with slender cross-sections.•The reliability of the proposed design approach is demonstrated by statistical analyses.
The Continuous Strength Method (CSM) is a deformation based design approach that provides accurate cross-section resistance predictions by making rational allowance for the interaction between cross-section elements, the partial spread of plasticity and the beneficial effects of strain hardening. The CSM can be used in conjunction with advanced analysis for the design of members and frames, but, for hand calculations, member-level stability checks are currently limited to stainless steel hollow section columns failing by flexural buckling. Extension 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 and existing experimental data collected from the literature on stainless steel hollow section members, including members with stocky and slender cross-sections. Comparisons demonstrate that the adoption of the CSM design equations in conjunction with both current and revised interaction factors considerably improves the accuracy of beam-column capacity predictions for members with stocky cross-sections. The analysis on beam-columns with slender sections shows that similar resistance predictions are obtained using Eurocode 3 and the CSM. The reliability of the proposed approach is demonstrated through statistical analyses performed in accordance with EN 1990.
The Continuous Strength Method (CSM) provides accurate resistance predictions for both stocky and slender stainless steel cross-sections; in the case of the former, allowance is made for the ...beneficial effects of strain hardening, while for the latter, design is simplified by the avoidance of effective width calculations. Although the CSM strain limits can be used in conjunction with advanced analysis for the stability design of members, for hand calculations, the method is currently limited to the determination of cross-sectional resistance only, i.e. member buckling resistance is not covered. To address this limitation, extension of the CSM to the design of stainless steel tubular section columns is presented herein. The proposed approach is based on the traditional Ayrton-Perry formulation, but features enhanced CSM cross-section resistances and a generalized imperfection parameter that is a function of cross-section slenderness. The value of the imperfection parameter increases as the slenderness of the cross-section reduces to compensate for the detrimental effect of plasticity on member stability that is not directly captured in the elastic/first yield Ayrton-Perry approach. The accuracy of the proposed approach is assessed against numerical results generated in the current study and existing experimental results collected from the literature. The presented comparisons show that the CSM provides consistently more accurate member buckling resistance predictions than the current EN 1993-1-4 design rules for all stainless steel grades. The reliability of the proposed approach is demonstrated through statistical analyses performed in accordance with EN 1990. Finally, the paper presents a framework through which the proposed approach can be developed for other cross-section types and materials.
•A consistent CSM approach for the design of stainless steel members is presented.•The new approach allows for the influence of material nonlinearity and strain hardening.•The accuracy of the CSM for the design of columns is assessed against experimental and numerical data.•The CSM provides consistently more accurate member buckling resistance predictions than current design rules.•The reliability of the proposed approach is demonstrated through statistical analyses.
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.
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•A general framework for assessing the serviceability limit state reliability at system level is presented.•Vertical deflections under gravity loads and lateral drifts under wind loads are studied.•Six baseline cold-formed frames, including the three main stainless steel families, are investigated.•Reliability results are presented for the Eurocode, US and Australian design frameworks.•Derived reliability indices are compared with suitable target values for each design framework.
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.
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•Data on most relevant random variables is collected through a comprehensive literature review.•Data for different stainless steel alloys and cross-section types are analysed.•The variability of parameters affecting the strength of stainless steel structures is statistically characterized.•Appropriate statistical functions and probabilistic models are provided for geometry, material, imperfections and residual stresses.•Foundational data is provided for complete member- and system-based reliability frameworks, from which safety factors and resistance factors can be derived.
•Extension of the Direct Design Method to stainless steel structures is presented.•Rigorous reliability framework is built for stainless steel structures.•Six stainless steel portal frames are ...analysed, covering different families.•Reliability indices are presented for different design frameworks under gravity loads.•System γM,s and ϕs factors are proposed for different target reliability indices.
Current structural codes for steel and stainless steel structures such as AISC360-16, AISC370-21, AS/NZS4100 and Eurocode3 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 γM,s and system resistance factors ϕs are proposed for the direct design of stainless steel frames in the European, US and Australian design frameworks under gravity loads.
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