Igor A. Chaves

Reliability-based evaluation of design guidelines for cold-formed steel-concrete composite beams

This paper presents an analysis of design guidelines for steel-concrete composite beams, formed by concrete-filled cold-formed steel sections. The study is based on experimental results for connector resistance (push-out) and for four full-scale beam bending tests. The accuracy of analytical design equations is evaluated by comparing their predictions with experimental results. Model bias and model uncertainty of analytical design equations are evaluated. The uncertainty in design variables (steel and concrete resistance, dead and live loads, model errors) is taken into account, and reliability index of code-compliant beams is evaluated. Results show that the models for shear connector and for beam bending resistance are fairly accurate, and represent very little contribution to problem uncertainty and failure probabilities. Results show that for practical beam lengths, full material interaction is guaranteed, and failure is dominated by bending. Reliability indexes of the order of 2.2 to 2.8 are obtained, reflecting reliability of the design procedures studied. These values are low, in comparison to target reliability levels of 3.0 used in code calibration, and should be interpreted carefully in future code revisions.

Technical Note: Rust Removal from Steel Coupons After Short-Term Marine Immersion

The quantification of mass loss, surface topography, depth of pitting, and localized corrosion for steels subject to marine corrosion requires the removal of rusts, preferably without causing addit...

Long term localised corrosion of marine steel piling welds

Abstract Localised or pitting corrosion can be detrimental for steel pipes and containment structures, since wall perforation may cause system failure. Herein maximum pit depth quantification and its development with time are considered for samples taken from longitudinal welds on 33-year-old tubulars exposed in Newcastle Harbour. Relationships between pit depth and material metallurgy and corrosion properties were investigated by means of standard macro-etching, rest potential and zero resistance ammetry techniques. It is considered that the observed results are the result of the lack of homogeneity at the corrosion interface caused by differences in grain size, grain structure and the potential for pitting to occur preferentially along boundaries. The results are compared to measurements for longitudinal welds obtained previously on samples of API X56 Spec 5L pipe exposed in similar waters for up to 3·5 years, showing a reasonable degree of consistency between the two sets of data. The reasons for this are discussed.

Service life estimation of concrete infrastructures

Abstract The adequate, long-term performance of reinforced concrete infrastructure depends greatly on being able to resist deterioration mechanisms such as reinforcement corrosion. The main mechanisms for this are described and critically reviewed in the light of properly-analyzed experience for, and behavior of, actual reinforced concrete structures. Recent research has shown that, for structures in the marine environment, the role of chlorides lies mainly in the reduction of the alkalinity of the protective, high-pH concrete, rather than in the direct attack on the reinforcement steel.

Long-term immersion exposure of perlite–aluminium syntactic foam in seawater:

Perlite–metal syntactic foam is a novel lightweight material with good specific strength and excellent energy absorption capabilities. To analyse its suitability in marine applications, perlite–metal syntactic foam has been immersed for 2 years in natural flowing seawater. The change of mass and mechanical properties has been studied as a function of exposure time. Results indicate a slow degradation of mechanical properties that can be attributed to a change of the macroscopic deformation mechanism. Interestingly, no evidence of significant corrosion was observed. Instead, the change in mechanical properties is triggered by the sedimentation of oxides and sulphates within the expanded perlite particles. Implications towards the long-term viability of such perlite–metal syntactic foam in marine applications are discussed.

Complex Pitting Corrosion in Long-Term Immersed Exposures of 6060 Aluminum Alloys in Temperate Natural Seawater

Novel observations of changes in pitting morphology of 6060 aluminum alloys immersed for periods of 3 y, 3.5 y, and 4 y in temperate seawater are reported. They indicate that the initiation and pro...

Corrosion performance of low alloy steels in sub-arctic natural seawater

Corrosion mass loss trends for low alloy and for high-strength structural steels of grades A, B, D, AH, and DH exposed for up to 5 years in sub-Arctic seawater near Vladivostok are compared with tr...

Long-term durability of reinforced concrete piles from the Hornibrook Highway Bridge

Abstract After more than 75 years continuous exposure to the Pacific Ocean waters on the Queensland coast, the 879 reinforced concrete driven piles that supported the superstructure of the Hornibrook Highway Bridge appeared to be in remarkably good condition when the bridge was demolished during 2011–2012. Detailed investigations revealed excellent, very hard concrete with pH values still around 12 and very little evidence of serious corrosion of the steel reinforcement. The concrete chloride content at the reinforcement was considerably more than the usually accepted limits. However, a few isolated occurrences of very severe localised reinforcement corrosion were found during demolition even though there was little visual external evidence. Possible reasons for the various observations are discussed, together with the practical implications.