640 publications from this institution
The serviceability design requirements of various structural elements and the provisions of building regulations, codes and standards are discussed in the paper. Results of the questionnaire survey of; a) engineers in Australia and England on the serviceability design requirements of structures, b) owners of buildings on their reaction to existing serviceability design provisions, as reflected in the building, and the cost implication of such serviceability requirements, and c) occupants of residential and commercial buildings on their reaction to any noticeable deflection and/or vibration of buildings, are summarised. The paper concludes by identifying the shortcomings in the current method of design for serviceability, by proposing a method for formulating realistic limits and an improved method of design for serviceability by computing the actual deflection and vibration of structural components and by recommending the preferred direction for future research.
In the past decade, there have been numerous advances in probability-based structural codes and codified
Corrosion on the interface between a metal alloy, such as steel, and a wet, permeable non-metallic medium is of considerable practical interest. Examples include the interface between steel and water, the atmosphere or concrete, as for steel reinforcement bars; between metal and soil, as for buried cast iron or steel pipes; deposits of some type, as in under-deposit corrosion; and the interface with insulation, protective coatings, or macro- or micro-biological agents. In all cases, corrosion initiation depends on the characteristics of the interfacial zone, both of the metal and the medium, and the spatial variability. For (near-)homogeneous semi-infinite media with good interfacial contact, the pitting, crevices and general corrosion of the metal will be largely controlled by the metal (micro-)characteristics, including its inclusions, imperfections and surface roughness. In other cases, these may be overshadowed by the macro-characteristics of the medium and the degree of interfacial contact, possibly with severe resulting corrosion. Where the build-up of corrosion products can occur at the interface, they will dominate longer-term corrosion and govern the long-term corrosion rate. For media of finite thickness, diffusion issues and material deterioration may also be involved. The practical implications are outlined. It is argued that with the presence of a suitable medium, it is possible to achieve negligible long-term corrosion but only if certain practical actions are taken.
Estimates of the expected life (durability) of protective (organic) coatings for ships are increasingly desired for the rational management of maintenance practices and the setting of asset policies. The life of coatings also has an influence on the prediction of safe remaining structural life, particularly for ships already subject to coating deterioration. Methods for estimating the life of organic protective coatings are briefly reviewed. It is concluded that despite attempts to develop mathematical models of coating deterioration, there is still insufficient unbiased data obtained from actual field experience for sufficiently well-defined vessel areas such as ballast tanks, known to be particularly prone to coating breakdown and poor inspection. Herein a preliminary survey to obtain initial estimates of models for coating durability for water ballast tanks in commercial vessels is described. The survey was conducted using experts from vessel users, coating contractors and suppliers, and an independent expert. As might be expected, the users tended to be more pessimistic and the contractors/suppliers more optimistic in their estimates compared with those of the independent expert. The collective estimates are reasonably consistent with a normal distribution. It was also found that coating life, described as percentage area breakdown, is approximately normal distributed with both increasing mean deterioration and variance.
A large scale atmospheric corrosion trial extending over five years is currently being conducted at Belmont Beach near Newcastle, Australia. The intent is to obtain information about the effects of orientation, height and bold exposure versus shielding effects as well as detailed chronological observations and variability data for nominally identical exposures. Such comprehensive data has not previously been obtained for the one site and under the one local climatic regime for all coupons. This provides a much better and more controlled environment in which to compare the various effects. Failure to achieve this in previous studies renders the study of such influences problematic. Also, variability of nominally identically exposed coupons has not previously been given attention. The paper deals with the three-year results and compares these with information available in the literature. After three years most of the boldly exposed coupons have completely corroded but most of the single sided coupons remain in varying degrees. A comparison is given between individual coupons exposed at different heights and single strips of steel exposed over the same vertical distance.
For structural systems of practical size, it has been recently recognised that identification of all the stochastically dominant failure modes is a key to further development in reliability theory. This paper presents a search algorithm called 'truncated enumeration method', which generates only stochastically dominant modes and satisfies a specified truncation criterion. An example is demonstrated. The relationship of this method to other techniques is noted (a).
The conventional procedure for calculating the strength of reinforced concrete frames consists of an elastic analysis with, sometimes, a limited amount of moment adjustment permitted to allow for inelastic effects. From such an adjusted moment field, the cross-sectrional properties may then be checked by so-called ultimate load principles. It is well recongised that this procedure is quite irrational, and numerous attempts have been made to provide a more consistent method for non-linear reinforced concrete frame analysis. This paper reviews those methods briefly, and compares the predictions and foundations of these methods to experimental observations on real or model frames. It will be shown that the theories singularly ignore the behaviour of beam-column joints, which are shown to play an important part in real frame behaviour. The number of the covering absatract for the conference is TRIS no 394142. (Author/TRRL)
Theoretical and laboratory studies indicate that the corrosion of mild and low-alloy steels should be a function of temperature. In practice, however, it is usually held that this cannot be discerned from actual field corrosion data, being confounded by many other influences. The present study considers data from a recent ASTM-sponsored field study, which reported observations for more than 5 years for the immersion corrosion at 14 different sites around the world for copper-bearing carbon steel (UNS K01501). It also considers data reported historically in the literature, both for copper-bearing steel and for structural-grade steel. For these steels, general or uniform corrosion is the main interest because pitting is usually limited. When data is restricted to conditions that might be expected to prevail at sea and is carefully scrutinized and supplemented by information about (the likely) environmental conditions, it can be arranged to suggest that there is a clearly defined effect of temperature on corrosion behavior. This effect is consistent with laboratory observations but extends them in the lower temperature region even though the available data in this region is sparse. The dependence on temperature for steel is not inconsistent with earlier reported observations on the temperature dependence of 90:10 copper-nickel and aluminum. The effects of the degree of dissolved oxygen saturation and dilution by fresh water (and calcium carbonates) are apparent in the reported data, as is the influence of water velocity.
A transcript of a discussion on the non-structural engineering aspects of buildings. The discussion also focuses on the special needs which are important for the construction and maintenance of heritage buildings.
Measures of Structural Reliability. Structural Reliability Assessment. Integration and Simulation Methods. Second-Moment and Transformation Methods. Reliability of Structural Systems. Time Dependent Reliability. Load and Load Effect Modelling. Resistance Modelling. Codes and Structural Reliability. Probabilistic Evaluation of Existing Structures. Appendices. References. Index.
The next section outlines the recent development of an appropriate model for fn(t, E) based on actual and very detailed observations of steels exposed to natural seawater. The model has been shown to be applicable to immersion, tidal and coastal atmospheric corrosion environments (Melchers 2003a, 2007b). Next is described how the model may be slightly simplified for practical application under longer-term exposure conditions. Field data is then used to estimate the variability in maximum pit depth at a given exposure location, derived from the application of extreme value statistics. Some comments are made also about the application of the simplified model.
Resistance deterioration which is purely a time function such as typified by simple corrosion problems is considered herein for structural systems subjected to one or more stochastic load processes. The resistances are modelled as Gaussian random variables and the loads as Gaussian random processes. Deterioration is considered by either of two simple models -exponential or parabolic functions of time. Both an upcrossing and an outcrossing formulation is used to estimate the up (out) crossing rate through linear domain boundaries. Numerical integration is employed to evaluate the resulting integrals, although significant simplifications are occasioned through the use of Gaussian random variables and processes. Results are given for two simple structural examples and compared to purely simulation results both for the outcrossing rate and for various sensitivity results. Good agreements is found. The results suggest that results for failure probability based on mean values of the deterioration models may be satisfactory in some cases.
The corrosion process in large-particle porous media is investigated with particular reference to corrosion in bulk carriers (ships). Examples of large-particle porous media include raw materials such as coal and iron ore which typically have particle sizes ranging up to approximately 50 mm diameter. It is proposed that the corrosion process is dominated by finer particles which co-exist with the larger particles. A mathematical model of the corrosion process is developed and used to estimate corrosion rates. These are shown to compare well with experimental results. The analysis indicates that to minimise corrosion it is desirable to maintain the moisture content of porous media in contact with mild steel either to less than 50%, or to more than 80%, of the maximum water holding capacity of the media.
No abstract is provided for this article.
Results are reported of a survey, conducted among practising structural engineers, to obtain a preliminary assessment of the degree to which errors in design calculations are detected. A set of calculations for wind loadings acting on a low rise frame was used as the survey instrument. Several errors were artificially placed in the calculations. The effectiveness of checking was compared to the magnitude of both the error itself and its effect on the design. Similarly, the effectiveness of checking as a function of time spent is noted. The empirical results are compared to models which have been suggested in the literature; the present results suggest that these models are too simplistic. Alternative models are suggested. (Author/TRRL)
For materials such as stainless steel, it is well known that the surface condition (roughness) can have an effect on corrosion loss or pitting as a function of exposure time. Although some isolated observations exist of this effect for mild steel under marine immersion, there appears to have been no systematic investigation. The present paper describes results obtained in field tests carried out over a period of 13 months in temperate waters on the Eastern Australian seaboard. Surface conditions considered were mill scale, surface ground, grit blasted, polished, acid cleaned, and pre-rusted. The effect of surface roughness on corrosion was found to be approximately proportional to the surface roughness index. Surface roughness has the most effect in the first few weeks of exposure, with the net effect then remaining approximately constant with time. The acid-cleaned coupons show only a low value of roughness index, but on the basis of scanning electron microscope (SEM) images and high early insta...
