Testing of ferritic stainless steel tubular structural elements.

Stainless steel is gaining increasing usage in construction owing to its durability, favourable mechanical properties and its aesthetic appearance, with the austenitic grades being the most commonly utilised. Austenitic stainless steels have a high nickel content (8%-11%), resulting in high initial material cost and significant price fluctuations; this, despite its desirable properties, represents a considerable disadvantage in terms of material selection. Ferritic stainless steels, having no or very low nickel content, may offer a more viable alternative for structural applications, reducing both the level and variability of the initial material cost. In comparison to the most widely used austenitic grades, the ferritic grades typically have higher yield strengths (250-350 N/mm2) and are easier to machine and work. Furthermore, by varying the chromium content (10.5%-29%), and with additions of other alloying elements, the required corrosion resistance for a wide range of structural applications and operating environments can be achieved. 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 and rosssection tests have been performed, covering both the standard 1.4003 grade and the 1.4509 grade, which has improved weldability and corrosion resistance. The experimental results are reported, analysed and compared to the results of tests performed on other stainless steel grades. Finally, design recommendations suitable for incorporation into Eurocode 3: Part 1.4 (2006) have been proposed

Experimental study of cold-formed ferritic stainless steel hollow sections

Stainless steel is gaining increasing use in construction because of its durability, favorable mechanical properties, and aesthetic appearance, with the austenitic grades being the most commonly used. Austenitic stainless steels have a high nickel content (8–11%), resulting in high initial material cost and significant price fluctuations; this, despite its desirable properties, represents a considerable disadvantage in terms of material selection. Ferritic stainless steels, having no or very low nickel content, may offer a more viable alternative for structural applications, reducing both the level and variability of the initial material cost while maintaining adequate corrosion resistance. 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, covering both the standard EN 1.4003 grade (similar to the chromium weldable structural steel 3Cr12) and the EN 1.4509 grade (441), which has improved weldability and corrosion resistance. In total, 20 tensile coupon tests, 16 compressive coupon tests, eight stub column tests, 15 flexural buckling tests, and eight in-plane bending tests were carried out. Precise measurements of the geometric properties of the test specimens, including the local and global geometric imperfections, were also made. The experimental results are used to assess the applicability of the current European (EN 1993-1-4) and North American (SEI/ASCE-8) provisions to ferritic stainless steel structural components. In addition, the relative structural performance of ferritic stainless steel to that of more commonly used stainless steel grades is also presented, showing ferritic stainless steel to be an attractive choice for structural applications

Buckling response of ferritic stainless steel columns at elevated temperatures

This paper presents a numerical study on the buckling behaviour of ferritic stainless steel columns in fire. Finite element models were developed and validated against existing test results to predict the elevated temperature non-linear response of ferritic stainless steel columns. A total of nine austenitic and three ferritic stainless steel column tests were replicated using the finite element analysis package ABAQUS. Parametric studies were performed to investigate the effects of variation of load level and global slenderness on the elevated temperature buckling response of ferritic stainless steel columns, and to extend the range of structural performance data. Both the experimental and numerical parametric study resultswere compared with the current design rules in EN 1993-1-2 (2005) and recent proposed modifications thereof by Ng and Gardner (2007), Uppfeldt et al. (2008) and Lopes et al. (2010).The European Community's Research Fund for Coal and Steel (RFCS) under grant agreement no. RFSR-CT-2010-00026, Structural Applications of Ferritic Stainless Steels

Effect of ketorolac on postoperative pain relief in dental extraction cases--a comparative study with pethidine

Objective: To compare the analgesic efficacy and side effects of ketorolac with pethidine in a day care procedure.STUDY Design: Single dose, double blind, case matched study.Methods: Sixty patients were divided into group A and group B, who received either ketorolac 30 mg or Pethidine 0.8 mg/kg ( both IN ) respectively at the time of induction of general anaesthesia. Patients were assessed in recovery room for pain according to visual analogue scale and any side effects. Amount of rescue analgesia required by both groups were also recorded. Odds Ratio and and Chi Square test were used for statistical analysis.Results: Statistical analysis showed no significant differences between these two drugs at any time interval, however a significantly decreased incidence of nausea and drowsiness was found in ketorolac group.CONCLUSION: Ketorolac 30 mg intravenously provides similar analgesic effects as Pethidine with much less incidence of nausea and drowsiness

Reliability assessment of design rules for stainless steel structures

This paper presents a re-evaluation of the current partial resistance factors recommended in EN 1993-1-4 for the design of stainless steel elements. Material data from key stainless steel producers were collected and carefully analysed, and representative values of the over-strength and the coefficient of variation (COV) of the material yield strength and ultimate tensile strength, necessary for performing reliability analysis, were established. The EN 1990 Annex D First Order Reliability Method (FORM) was applied to a substantial pool of experimental results. At the cross-section level, stub column and in-plane bending test results were used to assess the γM0 partial resistance factor. At the member level, flexural buckling and lateral-torsional buckling test results were used to evaluate the γM1 partial resistance factor. It is revealed that the current recommended partial resistance factors in EN 1993-1-4 (γM0 = γM1 = 1.1) cannot generally be reduced, and in some cases, modified design resistance equations are required, if the current safety factors are to be maintained

Investigating the effect of tunnelling on existing tunnels

A major research project investigating the effect of tunnelling on existing tunnels has been completed at Imperial College London. This subject is always of great concern during the planning and execution of underground tunnelling works in the urban environment. Many cities already have extensive existing tunnel networks and so it is necessary to construct new tunnels at a level beneath them. The associated deformations that take place during tunnelling have to be carefully assessed and their impact on the existing tunnels estimated. Of particular concern is the serviceability of tunnels used for underground trains where the kinematic envelope must not be impinged upon. The new Crossrail transport line under construction in London passes beneath numerous tunnels including a number of those forming part of the London Underground networ

Synthesis and crystal structure analysis of 2-​(4-​fluorobenzyl)​-​6-​phenylimidazo[2,​1-​b]​- [1,​3,​4]​thiadiazole and its chlorophenyl derivative

Prepns. of 2-​(4-​fluorobenzyl)​-​6-​phenylimidazo[2,​1-​b]​[1,​3,​4]​thiadiazole and its chlorophenyl deriv. were described. Preliminary anal. was done spectroscopically by means of 1H NMR, 13C NMR spectra, mass spectra and elemental analyses. Further the structures were confirmed by X-​ray crystal structure analyses. The 4-​fluorophenyl compd. crystd. in a triclinic P-​1 space group with three independent mols. in the asym. unit, while the 4-​chlorophenyl compd. belonged to P21/c space group with one mol. in the asym. unit. The imidazo-​thiadiazole entity was as usual planar. Intramol. C-​H···N hydrogen bonding between the imidazole and the Ph ring of the mol. was obsd. in both compds. The mols. of 4-​fluorophenyl deriv. was linked into two dimensional supramol. hexagonal hydrogen bonded network sustained by C-​H···F interaction, while those of 4-​chlorophenyl deriv. was linked by bifurcated C-​H···N interactions. Further, the mol. packing of both the compds. was stabilized by π-​π stacking interactions between the benzene and imidazo-​thiadiazole ring systems

Structural response and continuous strength method design of slender stainless steel cross-sections

In current structural stainless steel design codes, local buckling is accounted for through a cross-section classification framework, which is based on an elastic, perfectly-plastic material model, providing consistency with the corresponding treatment of carbon steel cross-sections. Hence, for non-slender cross-sections, the codified design stress is limited to the 0.2% proof stress without considering the pronounced strain hardening exhibited by stainless steels, while for slender cross-sections, the effective width method is employed without considering the beneficial effect of element interaction. Previous comparisons between test results and codified predictions have generally indicated over-conservatism and scatter. This has prompted the development of more efficient design rules, which can reflect better the actual local buckling behaviour and nonlinear material response of stainless steel cross-sections. A deformation-based design approach called the continuous strength method (CSM) has been proposed for the design of stocky cross-sections, which relates the strength of a cross-section to its deformation capacity and employs a bi-linear (elastic, linear hardening) material model to account for strain hardening. In this paper, the scope of the CSM is extended to cover the design of slender stainless steel cross-sections under compression, bending and combined loading, underpinned by and validated against 794 experimental and numerical results. The proposed approach allows for the beneficial effect of element interaction within the cross-section, and is shown to yield a higher level of accuracy and consistency, as well as design efficiency, in the capacity predictions of slender stainless steel cross-sections, compared to the effective width methods employed in the current international design standards. Non-doubly symmetric sections in bending, which may be slender, but still benefit from strain hardening, are also discussed. The reliability of the CSM proposal has been confirmed by means of statistical analyses according to EN 1990, demonstrating its suitability for incorporation into future revisions of international design codes for stainless steel structures

Flexural behaviour of concrete filled tubular flange girders

In this paper, the behaviour of concrete filled tubular flange girders (CFTFGs) is investigated through both numerical and analytical modelling. These are new and complex members and their behaviour is governed by a number of inter-related parameters. This work aims to study the relative influence of a number of these variables on the flexural behaviour, particularly for CFTFGs with stiffened webs. A nonlinear three-dimensional finite element (FE) model is developed in the ABAQUS software and is validated using available experimental data. The validated model is then employed to conduct parametric studies and investigate the influence of the most salient parameters. For comparison purposes, and to observe the effect of the concrete infill, steel tubular flange girders (STFGs) with a hollow flange are also studied. The finite element models consider the effects of initial geometric imperfections, as well as other geometrical and material nonlinearities, on the response. In addition, simplified analytical expressions for the flexural capacity are proposed, and the results are compared to those from the FE analyses. It is found that CFTFGs and STFGs with the same dimensions have similar buckling shapes but different buckling loads, with the CFTFG offering greater buckling resistance. This highlights the influence of the concrete infill which increases the stiffness of the upper flange, and hence allows the member to carry additional bending moments compared to STFGs. The proposed analytical expressions, which are suitable for design, are also shown to be capable of providing an accurate depiction of the behaviour and bending moment capacity

Analytical Studies on the oxidation of cysteine, cystine and Methionine with V(v) reagent

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