Experimental investigation of cyclic response of stainless steel reinforced concrete columns

Corrosion of carbon steel reinforcement is the major cause of premature deterioration of reinforced concrete buildings and infrastructure. There are increasing interests in the use of maintenance-free materials such as stainless steel reinforcement in concrete, with inherent durability and resistance to various forms of corrosion and favourable mechanical properties, in particular excellent ductility and cyclic resistance. This paper presents the main results of an experimental programme designed to investigate the potential benefits of the relatively high ductility and substantial strain hardening of stainless steel on the cyclic performance of reinforced concrete columns with stainless steel reinforcing bars. Three experimental tests were performed on full-scale columns, two with duplex EN 1.4462 stainless steel reinforcement, one tested under cyclic lateral loading and one tested monotonically, and one control specimen with A500 carbon steel reinforcement tested under cyclic lateral loading. In addition, conventional pull-out tests and tensile tests were conducted for a comparative assessment of the bond and mechanical properties of the reinforcement bars. The force-displacement global response and the dissipated energy evolution of the tested columns are presented and discussed

Testing, numerical simulation and design of prestressed high strength steel arched trusses

The structural behaviour of prestressed high strength steel arched trusses is studied in this paper through experimentation and numerical modelling. Four 11 m span prestressed arched trusses fabricated from S460 hot finished square hollow section members were loaded vertically to failure. Three of the tested trusses were prestressed to different levels by means of a 7-wire strand cable housed within the bottom chord, while the fourth truss contained no cable and served as a control specimen. Each truss was loaded at five points coinciding with joint locations along its span, and the recorded load-deformation responses at each loading point are presented. Inclusion and prestressing of the cable was shown to delay yielding of the bottom chord and enhance the load carrying capacity of the trusses, which ultimately failed by either in-plane or out-of-plane buckling of the top chord. For the tested trusses, around 40% increases in structural resistance were achieved through the addition of the cable, though the self-weight was increased by only approximately 3%. In parallel with the experimental programme, a finite element model was developed and validated against the test results. Upon successful replication of the experimentally observed structural response of the trusses, parametric studies were conducted to investigate the effect of key parameters such as prestress level, material grade and the top chord cross-section on the overall structural response. Based on both the experimental and numerical results, design recommendations in the form of simple design checks to be performed for such systems are provided

Influence of the degree of utilization on the structural behaviour of stainless steel frames subject to fire

Stainless steel is known to have a better behaviour at elevated temperatures than carbon steel. This, combined with its aesthetic appeal and corrosion resistance, makes stainless steel structures an attractive alternative to carbon steel structures. However, EN 1993-1-4 does not establish de-sign rules associated with global analysis of stainless steel frames and EN 1993-1-2, devoted to carbon steel, provides a conservative approach for the fire design of stainless steel structures. Hence, current European codes do not provide efficient design guidelines for stainless steel frames subject to fire and therefore the response of this type of structures should be assessed by means of experimental tests and/or numerical analyses. The main objective of the paper is to assess the nonlinear structural response of stainless steel frames subjected to fire, focusing the investigation on the influence of the degree of utilization. A comprehensive numerical analysis on Class 1 and Class 3 stainless steel frames and Class 1 carbon steel frame subjected to fire is carried out varying the degree of utilization. Calibration of the FE models has been carried out as a part of a study of transient thermo-mechanical models, which are needed to assess the response of stainless steel frames subjected to fire.The authors acknowledge the funding from the MINECO (Spain) un-der Project BIA2016-75678-R, AEI/FEDER, UE “Comportamiento estructural de pórticos de acero inoxidable. Seguridad frente a ac-ciones accidentales de sismo y fuego”.Peer ReviewedPostprint (author's final draft

Structural behaviour of cold-formed stainless steel tubular members

This thesis examines the behaviour of cold-formed stainless steel tubular structural members, with an emphasis on ferritic stainless steels. Owing to the high comparative expense of stainless steel relative to traditional carbon steel, this study aims to identify and develop means of utilising the material more efficiently. A comprehensive material test programme was carried out as part of an extensive study into the prediction of strength enhancements in cold-formed structural sections that arise during production. Material tests on a total of 51 flat coupons and 28 corner coupons, extracted from a total of 18 cross-sections formed from a wide range of materials, were performed. A new, simple and universal predictive model for harnessing the cold-formed induced strength enhancements was developed which offers, on average, 19% and 36% strength enhancements for the cross-section flat faces and corner regions, respectively, relative to the strength of the unformed material. Ferritic stainless steels, having no or very low nickel content, offer a more viable alternative for structural applications to the more commonly used austenitic stainless steels, reducing both the level and variability of the initial material cost. There is currently limited information available on the structural performance of this type of stainless steel. Therefore, to overcome this limitation, a series of material, cross-section and member tests have been performed on two ferritic grades - EN 1.4003 and EN 1.4509. The experimental results were used to assess the applicability of the current codified design provisions to ferritic stainless steel structural components. Moreover, the elevated temperature performance of ferritic stainless steels, covering the material response and the flexural buckling behaviour, was investigated through analysis of experimental and numerical results, leading to proposals for suitable design recommendations. Finally, simplifications and refinements to the recently developed continuous strength method (CSM) were made. Comparison of the predicted capacities with over 140 collected test results on stainless steel stub columns and cross-sections in bending shows that the CSM offers improved accuracy and reduced scatter relative to the current design methods. The reliability of the approach has been demonstrated by statistical analyses, enabling its use in structural design standards.Open Acces

Performance of axially restrained carbon and stainless steel perforated beams at elevated temperatures

This paper compares the fire performance of axially restrained perforated carbon and austenitic stainless steel composite beams with circular and rectangular web openings. Finite element models, validated against experimental tests from the literature, were used to perform parametric analysis. The beams were analysed under various levels of load ratio and axial restraint stiffness covering the ranges which may exist in practice. It is concluded that austenitic stainless steel perforated beams show a more ductile fire response compared to carbon steel beams of similar geometry. It is shown that despite stainless steel’s higher thermal expansion, the beams exhibit lower thermal-induced peak compressive forces than carbon steel beams giving rise to lower levels of thermal-induced compressive force on the adjacent cold structures. The load ratio was found to determine the relative survivability of stainless steel and carbon steel beams, where at load ratios lower than 0.6, stainless steel beams show superior fire resistance than their carbon steel counterparts. The paper also assesses the applicability and accuracy of the SCI method for the design of carbon and stainless steel perforated beams, and recommendations for future improvements are made