Publications

Stress corrosion of glass fibre reinforced polymers for infrastructure applications

No abstract is provided for this article.

Reinforcement corrosion of the Phoenix caissons after 75 years of marine exposure

The reinforced concrete (RC) caissons, code-named Phoenix, still visible off the coast of Arromanches, France, have been exposed to marine immersion, tidal, splash and atmospheric conditions since 1944. Little evidence of corrosion of the steel reinforcement was observed during inspections in 2011, 2015 and 2019, although there was much structural damage. Archival material from the Second World War reveals the caissons were designed to low safety margins, without consideration of durability and constructed at a very fast rate mostly with unskilled labour, minimal material usage, without additives and no restrictions on adding water to aid concrete workability. Analysis of data that has recently become available indicates the concretes had a high cement content and were made with calcareous aggregates. It is concluded that these factors contributed to the high strength, low permeability and high remaining alkalinity of the concretes and hence to the very low evidence of reinforcement corrosion. When interpreted using recent experimental observations, these observations have implications for the design of new RC structures in marine exposures and for the prediction of the remaining life of older marine-exposed RC structures.

Corrosion of mild steel in elevated temperature hard freshwater

The bimodal model previously shown to be applicable to long term corrosion loss of mild steel in seawater is examined herein for hard freshwater at elevated temperatures. Laboratory data reported in the literature are reinterpreted using conventional corrosion theory and the bimodal model. The data fit the trends for the parameters of the model extrapolated from water temperature observations. One different set of data earlier can be reconciled if allowance is made for the effect on corrosion of water velocity. Overall the results show the bimodal model is applicable to freshwaters to 70°C.

On probabilistic absolute optimum design

No abstract is provided for this article.

Long-term corrosion of buried cast iron water mains: field data collection and model calibration

The external corrosion of buried cast iron water mains is a significant problem for the Australian Water Industry. To improve maintenance and replacement strategies for these mains the water industry requires a method to estimate their remaining service lives. Predictions of long-term corrosion losses, pit depths and pitting extents are therefore required. A conceptual model for the prediction of long-term corrosion has been developed and the external soil conditions influencing corrosion were identified in a previous study. To calibrate the model, long-term data of corrosion (average losses and maximum penetration) and associated soil parameters for pipes in service is required. Field data has been collected at 18 condition assessment sites within Hunter Water Corporations network. This paper presents the field observations from the first 11 sites, the model calibration procedure and results of the calibration. The evidence gathered in this work suggests that the long-term maximum corrosion penetration increases with increasing soil wetness (measured using degree of saturation) for the sites investigated. The initial model calibration produced model parameters for cast iron pipes buried at standard depths in relatively homogeneous, low-permeability, soils with degrees of saturation equal to 0.66 and 0.76.

Localized corrosion of steel sheet piling

When steel sheet piling suffers accelerated low water corrosion the webs and flange-web regions of individual piles often perforate first, for reasons not fully understood. To investigate this, samples of the cross-sections of typical U and Z profile sheet piling were exposed to natural seawater for 1, 2 and 3years. They showed localized corrosion in the central region and also near the flange-web junctions. These locations were found to have more material defects and segregation and show composition differences. It is proposed these observations are linked to localized sheet pile perforation after long exposure to seawater.

New results for the corrosion of reinforcement in marine environments

The apparently premature corrosion of steel reinforcement in reinforced concrete structures exposed to marine environments continues to be a matter of concern in practice despite decades of research effort and much research funding expenditure and despite much practical experience. Herein results are reported of a long-term (10 year) study of the influence of alkalis on the corrosion initiation and progression of 6mm diam. reinforcing bars centrally embedded in 40x40x160mm concrete specimens. These were made with seawater as mixing water and with a variety of mix proportions including some with added alkalis. All were equally well compacted by vibration. After 10 years continuous exposure in a fog-room only a limited amount of corrosion initiation was observed. These results are in stark contrast with those reported in the famous paper by Shalon & Raphael (1959) who found serious corrosion of reinforcement after only 1-2 years exposure for all mixes. It is shown herein that the corrosion loss trends in those tests are similar to those of steel exposed directly to seawater. This indicates that in the 1959 tests the concrete provided little protection against reinforcement corrosion. The reasons for this are considered herein and the practical implications discussed.

A new interpretation of the corrosion loss processes for weathering steels in marine atmospheres

Most available data sets for the long-term corrosion loss of various grades of weathering steel exposed to marine atmospheric environments are demonstrated to be consistent with the multi-phase corrosion model previously proposed for steels exposed to marine environments. This means that the early corrosion of weathering steels by oxidation is gradually inhibited by the build-up of corrosion products. These produce anoxic and sub-oxic conditions that may permit microbiological activity to govern the longer-term corrosion loss process. This new interpretation for the long-term corrosion of weathering steels may have implications for the design of such steels.

Investigation of Severe Corrosion of Mooring Chain In West African Waters

Closing Session - Future Directions

The final discussion session of the Newcastle Earthquake Conference outlines changes that need to be made in relation to earthquake engineering, hazard analysis, and response. The recommendations are based on a broad feeling of consensus by conference participants. The discussion also includes feedback of problems currently facing industry and civic professionals involved in the Newcastle earthquake of 1989., i.e insurance assessment, continuing ground movement, demolishment vs. repair, and the public perception of engineers.

Structural Modeling: An Overview

Overload failure of structural components under random crack propagation and loading – a random process approach

In this paper, the problem of overload failure of a structural component under random loading and under random crack propagation is addressed. The problem is formulated by combining the first passage failure model with stochastic models of crack propagation. Disadvantages of the standard random variable approach to the problem are discussed, and an alternative random process approach is developed. The developed solution addresses both overload and critical crack growth failure modes, requires a single mean crack growth computation, allows the consideration of non-destructive inspections and significantly speeds life-time analysis. The random process approach leads to a first passage problem involving crossings of a random barrier level, which is solved by means of the ensemble up-crossing rate approximation. Limitations of this approximation are addressed and related to typical problem parameters. The concept of barrier failure dominance is discussed, and extended to the case of a barrier-defined failure. Sensitivity studies involving different problem variables are performed, helping to identify the appropriate solution method for specific problems.

Deflection of Hyperstatic Thermoelastic Structures

In the classical theory of thermoelastic solids, the deflection of linearly elastic isotropic bodies as a result of applied thermal loads can be determined using Maisel's Integral Solution, a technique based on Betti's Reciprocal Theorem. It is a requirement of the technique that a solution to the isothermal equivalent linear elastic stress distribution problem is available. In the conventional structural analysis of linearly elastic structures, a particular adaptation of the virtual work method, known as the unit (dummy) load technique, may be used to obtain structure deflections. It has recently been shown that this technique can be adapted for the solution of hyperstatic structures where the hyperstatic stress distribution due to applied loading is not known. It will be shown that these approaches to deflection calculation are essentially equivalent, and that the application of either technique can considerably simplify deflection calculations for hyperstatic structures subject to temperature differentials.

Prediction of long term corrosion in soils using electrochemical tests

Previous work by the author has focused on some of the physical and practical issues of short term electrochemical testing of soils. This work has shown that electrochemical testing is valid and the results reproducible for soils. The technique can measure short-term corrosion rates and gives an insight to the different corrosion mechanisms present in an underground environment. What has not yet been well demonstrated using this electrochemical cell is whether short-term electrochemical testing relates to long-term field corrosion, particularly pitting corrosion. A successful correlation between short term corrosion testing and long-term field corrosion would give the asset owner access to a valuable predictive tool. The purpose of this paper is to critically examine the theory behind this commonly applied industry test and present some initial results of experimental testing undertaken as part of this current research. Over the past 5 years, as part of an ongoing condition assessment program, Hunter Water Australia has been collecting long-term field pipe corrosion data, and associated soil samples, for buried cast iron pipelines within the Hunter region. Various individual pipes were sandblasted and the corrosion data recorded. At each site a representative soil sample was collected for the purpose of assessment using the electrochemical test described previously (Dafter 2009). This sampling and testing program has provided an opportunity for long-term field pipe corrosion to be directly compared with short-term electrochemical tests. This paper provides a description of the short-term testing and long-term field corrosion recording that has been undertaken through this research program to date, and includes a discussion of the results of electrochemical testing that have been achieved.

Corrosion of steel in seawater - A poorly formulated but important practical problem

Mild and low alloy steels are used extensively for off-shore structures and for ship construction as well as for sheet piling and harbour-side facilities. Despite more than 60 years of effort, and some quite extensive, long term experimental test programs, the precise understanding of the mechanics of the marine corrosion of these steels and the influences of the various factors which are now known to be important has been slow to develop and, in the context of mathematical formulation, have been neglected by material scientists/engineers. The various factors of importance in marine corrosion and the models which have been proposed to describe time-dependent material loss as a function of time are reviewed.

Effect of small compositional changes on marine immersion corrosion of low alloy steels

Small changes in the composition of mild and low alloy steels can effect their immersion corrosion behaviour. A number of comprehensive test programs for coupons immersed at different locations and recovered at different times have been reported. Comparison between them has also been attempted with modest success as well as leaving some apparent inconsistencies in the effect of some alloying elements. In this paper, a new comparative analysis of previously reported observations is reported. It employs a recently reported multi-phase phenomenological corrosion–time model, with different corrosion phases governing corrosion behaviour. Each phase is a function of time. The analysis shows that metal composition can influence the first, kinetically controlled corrosion phase and also the long-term anaerobic corrosion phases. However, during the phase controlled by oxygen diffusion through the corrosion product, metal composition is largely irrelevant, in agreement with theoretical predictions. It is shown that the several observations in the literature about the effect of particular alloys can be reconciled, including apparently conflicting observations about the effect of chromium content.

Long term localised corrosion of marine steel piling welds

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.

Investigating the effects of corrosion on 45-year-old prestressed concrete bridge beams

No abstract is provided for this article.