The feasibility of using electromagnetic waves in determining membrane failure through concrete

Concrete flat roof defects such as water leakage present a significant and common problem in large buildings, particularly in tropical countries, where rainfall is high. To monitor this condition, effective non-destructive test methods are required to detect problems at an early stage, especially hidden defects within the concrete roof, which are critical. This paper presents the potential use of electromagnetic (EM) waves for determining possible leakage of the concrete flat roof as a result of failure of the waterproof membrane layer. This study was assessed, experimentally by investigation of the propagation of EM waves through the roof and their interaction with water. Novel Microwave sensors described in the paper operate in the 6 GHz to 12 GHz frequency range using a Marconi 6200A microwave test set. A range of existing methods was reviewed and analysed. Results of experimental tests confirmed that microwaves could be used as an alternative non-destructive method for identifying water ingress caused by membrane failure into the concrete roof surface

Masonry compressive strength prediction using artificial neural networks

The masonry is not only included among the oldest building materials, but it is also the most widely used material due to its simple construction and low cost compared to the other modern building materials. Nevertheless, there is not yet a robust quantitative method, available in the literature, which can reliably predict its strength, based on the geometrical and mechanical characteristics of its components. This limitation is due to the highly nonlinear relation between the compressive strength of masonry and the geometrical and mechanical properties of the components of the masonry. In this paper, the application of artificial neural networks for predicting the compressive strength of masonry has been investigated. Specifically, back-propagation neural network models have been used for predicting the compressive strength of masonry prism based on experimental data available in the literature. The comparison of the derived results with the experimental findings demonstrates the ability of artificial neural networks to approximate the compressive strength of masonry walls in a reliable and robust manner.- (undefined

Is toughness a better metaphor than resilience?

Toughness is arguably a better metaphor than resilience to describe the characteristics of wider systems for which the term ‘resilience’ is currently employed. This argument is presented by describing the various features of a stress–strain curve, to which the two terms relate. In particular, it is the large energy-absorbing and strain capacities of the plastic region that make toughness a more apt metaphor. System toughness can be seen as having three aspects, namely robustness, redundancy and element toughness. Similarities are demonstrated between the analogical source of structural mechanics and two analogical targets, namely transportation and social systems. ‘Post-yield’ behaviour in such wider systems can be classified as to whether they are ductile or brittle; and as to whether they display strain hardening or strain softening

Pompeii by Robert Harris : an engineering reading

Pompeii, the bestselling novel by Robert Harris, is a rich source of ideas regarding engineering attitude and outlook. Its main protagonist is a young Roman hydraulics engineer in charge of the Roman aqueduct that served Pompeii and skirted Vesuvius at the time of the destruction of the former by the eruption of the latter in AD 79. Logic, leadership, ethics, science, nature, culture and public service are some of the wide ranging themes that come under the purview of the novel, all of them related to the art and practice of engineering

Philosophical underpinning for systems thinking

The key characteristics that distinguish soft systems from hard ones are spelt out. The writings of Michael Polanyi and Martin Heidegger, despite their very different worldviews, are used to give philosophical underpinning to these characteristics, especially the notion of practitioner involvement. In addition, the complementary nature of Polanyi’s ‘emergence’ and Heidegger’s ‘breakdowns’ is highlighted. In conclusion, a reflection is given on what constitutes a soft systems approach

Aesthetics and ethics in engineering: Insights from Polanyi

Polanyi insisted that scientific knowledge was intensely personal in nature, though held with universal intent. His insights regarding the personal values of beauty and morality in science are first enunciated. These are then explored for their relevance to engineering. It is shown that the practice of engineering is also governed by aesthetics and ethics. For example, Polanyi’s three spheres of morality in science—that of the individual scientist, the scientific community and the wider society—has parallel entities in engineering. The existence of shared values in engineering is also demonstrated, in aesthetics through an example that shows convergence of practitioner opinion to solutions that represent accepted models of aesthetics; and in ethics through the recognition that many professional engineering institutions hold that the safety of the public supersedes the interests of the client. Such professional consensus can be seen as justification for studying engineering aesthetics and ethics as inter-subjective discipline

Influence of drying on concrete sorptivity

The experimental programme described in this paper indicated that concrete grade and specimen preconditioning were the major factors influencing sorptivity, whereas specimen size and coating had relatively little effect. The paper recommends that sorptivity be carried out on specimens coated on their side surfaces—that is, the curved surface in the case of cylinders. A 25 mm thick slice incorporating the original cast surface of a cylinder or core could be used as a sorptivity specimen, leaving the rest of the specimen for strength testing. A moderate amount of oven drying (e.g. 3 days at 508C) is also recommended in order to increase the sensitivity of the sorptivity index. This research also demonstrated that sorptivity results from a variety of conditions could be generalised as a function of the desorption ratio; this is an index of the amount of drying that has taken place at the time of sorptivity testing

Comparing the systems approaches of Checkland and Blockley

It is argued that systems approaches from even different backgrounds can nevertheless end up with similar features, promoting the idea that such approaches are grounded in reality, as science is taken to be. The systems approaches of Peter Checkland and David Blockley, from management and engineering backgrounds, respectively, are explored with a view to highlighting similarities and differences. This is done by looking at summaries of their approaches and examples of their use. Both Checkland’s and Blockley’s approaches have a set of common features such as layers; purpose; top-level outcome; attributes such as what, how and why; measures; uncertainty and conversation. Such similarities prompt us to see systems approaches as being objective rather than relativistic. The differences in their overall approaches reflect the hierarchically structured nature of reality that requires hierarchically ordered approaches to deal with it

Reduction of concrete sorptivity with age through carbonation

Ordinary Portland cement (OPC) concrete specimens that had been air - dried for 3.5 years were found to have an increase in weight and reduction in sorptivity, with weight and sorptivity changes being greater for specimens with higher original sorptivity. Since this was attributed to carbonation of the surface zone, the porosity differences between end slices and the specimen interior in cylindrical specimens from another test series (of 4 years of age) were measured, together with the depths of carbonation. It was found from sensitivity analyses performed on a neural network model that the porosity difference can be attributed, in increasing order of importance, to (i) depth of carbonation, (ii) original sorptivity (which reflects both the quality of the mix and the efficiency of curing), and (iii) whether the end slice was a top or bottom one (reflecting the direction of casting and compaction). Tests on existing structures also showed that sorptivity decreased with age and also that (carbonated) surface sorptivities were lower than interior sorptivities, further confirming that the reduction of sorptivity with age is due to surface carbonation and that this carbonation occurs in and benefits surfaces with poorer initial quality more. This implies that carbonation could have mutually compensatory effects on some aspects of concrete durability