Interrupted interface on the cybernetics of digital design process

From the viewpoint of Batesonian cybernetics, ‘conscious purpose’ and ‘artistic process’ are distinct ends of a spectrum of the functioning of ‘self’. The conceptual stage of the design process is essentially an artistic activity unencumbered with accuracy, dimensionality, scale, program or even tectonics, albeit all of these maybe tacitly present at the ‘back of a designer's mind’. Artistic activities involve broad mental processes that are beneath the stratum of consciousness. By definition, consciousness is selective awareness; it is linear in execution and limited in its capability to synthesize complex parameters. One of the central questions of this paper is “if artistic process requires one to abandon, or relinquish conscious purpose at the time of the generation of the work of art, and if the early stages of artistic process is a result of a vast number of ‘unconscious’ forces and impulses, then how can the computer, which demands (and thus propagates) geometric precision, focused operation and rational execution, be part of that process?” This paper will explore how, cybernetically, the computer can be ‘coupled’ with ‘self’ (via a visual interface) and the artistic process. Three specially devised conceptual design exercises—namely BlurrDesign, BlinDesign and BlitzDesign—and three corresponding “interruptive” computer interface modifications were deployed in an introduction to digital media course. The results of this study are now under consideration for their effectiveness in promoting conceptual design using the computer, and how the ‘self’ might form a cybernetic whole with the machine. The findings could have implications in design pedagogy, informatics and interface design.     

A review of the emission of VOCs from polymeric materials used in buildings

Building and furnishing materials and consumers products are important sources of formaldehyde and other volatile organic compounds (VOCs) in the indoor environment. The emission from materials is usually continuous and may last for many years in a building. The available evidence indicates that VOCs can cause adverse health effects to the building occupants and may contribute to symptoms of ‘Sick Building Syndrome’.

Control of VOC emission should increasingly become an important consideration for the design and manufacture of polymeric materials used in buildings. The EC Construction Products Directive ‘Essential Requirements’ set a framework for limiting the use of materials that could pose a health risk to building occupants. Furthermore, the on-going development of voluntary labelling schemes and data bases of material emissions that could be used by building designers, should further strengthen the demand for ‘low VOC emitting’ products.

This paper reviews available information about the emission of VOCs from polymeric building materials, the level of emissions in the indoor environment and the requirements for testing of the materials.     

Representation of uncertainty in maximum depth of marine corrosion pits

Pitting can be a critical form of corrosion for mild and high strength low alloy structural steels subject to saline environments. For pipelines, tanks and nuclear and other containers perforation is the main design criterion. The present paper outlines a recently developed model for the progression of ‘maximum’ observed pit depths, based on new field trials using conventional coupon testing. The variability of the maximum pit depth and its changing behaviour with time of exposure is an important aspect for structural reliability studies. The most common approach uses the Gumbel distribution. However, recent data for mild steel reveals inconsistencies. These are described and have been noted also for pitting in some other metals. It is proposed that proper account has not been taken of sample inhomogeneity and, more importantly, that extreme pits are unlikely to be independent events, even asymptotically, as required by extreme value theory. A much simpler approach based on structural systems reliability theory is proposed. This has important practical implications for extrapolation to larger areas of steel plate or for long-term exposures, such as for nuclear containers.     

Use of meteorological/constructional statistics to estimate building heat needs

Building heat needs over a month or a year are often estimated on the basis of the relevant degree day value, in which some crude account is taken of solar and other casual gains in the choice of the base temperature. A more realistic assessment of building heat needs including the effects of passive gain (through a window or glazed wall) can be made using the ‘empirical’ approach of Davies. In this article a statistical approach is developed in which use is made of degree day type data, and measures of days which are ‘disadvantageous’ and ‘advantageous’ from the point of view of saving back-up heating, together with the first four moments of the distribution of advantageous days (7 statistics in all). From five of these statistics a curve can be fitted to the distribution. After suitable integration of the fitted curves another estimate of building heat needs is obtained (the ‘curve fitting’ value). The heat needs as obtained empirically and by curve fitting agree closely. The 7 statistics are easily handled by a mini computer. They thus provide a convenient and accurate extension to degree day methods when local meteorological information has been processed in conjunction with passive solar collector characteristics. Window area, or glazed wall resistance, and assumptions about ventilation rate are only needed in the final stage of computing heat needs.     

Aesthetics of thin-walled structures

Thin-walled structures are assumed to include all ‘surface-acting’ structures. This is a brief review of the factors generally considered to influence our emotional and intellectual response to built forms. General problems arising from the strong forms and large plain surfaces of thin-walled structures are considered. A number of specific types are then treated under the headings of ‘bridges’, ‘shells’, ‘silos’, ‘tents’ and ‘air-supported structures’.     

Fire detector systems with ‘distributed intelligence’ the pulse polling system

Well over a million fire detectors are currently in use in the Federal Republic of Germany. Provided they are correctly installed and efficiently maintained, they detect fires reliably at a very early stage. At the present time, the false alarm rate equals about 1% of the number of installed detectors per annum. This false alarm rate must be at least proportionately reduced as further detectors are installed.

Since it is scarcely possible to improve tried-and-tested detector designs, the employment of higher-grade detector signal processing methods suggests itself.

However, ‘more intelligent’ detector signal processing using microprocessors calls for an entirely new fire detection system structure: detectors which independently ‘decide’ whether an alarm criterion is met and then initiate an alarm are replaced by sensors which continuously transmit their measured values to the ‘intelligence’ panel for evaluation. Passive panels which simply receive alarm signals from activated detectors and indicate these or transmit them to the fire brigade are replaced by active processors using permanently improved algorithms for the detection of real fires.

A structural change of this type is possible provided the positive — and the customary — characteristics of the conventional technique are not lost, viz. two-wire lines between detector and panel, simple installation and handling, easy detector replaceability, low cost, etc.

The pulse detector technology is described in detail; it combines the simplicity of conventional fire detection systems with new characteristics, e.g. identification of individual detectors, permanent functional check of all connected detectors, automatic notification of maintenance requirement prior to a slowly developing fault (e.g. such as that caused by corrosion or contamination), uniform response sensitivity unaffected by drifting from the operating points of the detectors and, above all, greater protection against false alarms.     

Loading arrangement and structures, as one system—temporary instability of elements and structure

The paper deals with some special questions of experimental research being important when frames are tested and the load carrying capacity of the structure is lost because of any instability phenomena. Computer simulation results are presented:

• -to illustrat the difference between the real and ‘virtual’ structural behaviour, which is dependent on the character of loading, and

• -to show that in certain conditions a structure, which became unstable because of the instability of one of its elements, is able to turn to a stable state and to carry increasing loads before complete loss of its load carrying capacity.

This paper is a modified (slightly extended) version of that which was presented during the ‘First International Conference on Coupled Instabilities in Metal Structures’. Reflections of participants initiated some modification.     

Tangible virtuality—perceptions of computer-aided and physical modelling

Designing—giving form to new objects or environments—is largely a question of anticipating the workings of spatial and material environments, which can become ‘reality’ only by being built. Until ‘realized’, a design is essentially a figment of the designer's imagination, although his or her ideas may be laid down and conveyed to others via specialized design media. In this way, impressions of the design may be shared with clients, colleagues or other ‘actors’ in the design process.

Such products of the designer's imaging process can be relatively abstract or begin to approach future reality. Form & Media research can be ‘revealing’, stimulating insights concerning preferences, working processes and the effects of products of the designer's imagination. In the past 10 years, we have gained considerable practical experience with both virtual and tangible (scale) models. We have compared different techniques in conference workshops, within educational settings and in our Form & Media research laboratory. The research projects ranged from the development of practical techniques and working methods to protocol analyses of designing architects.

This contribution draws comparisons between different computer-aided modelling techniques, with an indication of their perspectives, making use of the experience gained from various experiments in an educational context, and will highlight the potentials for different combinations of digital and physical modelling techniques.     

Buckling of vibrations of shear-flexible orthotropic plates subjected to mixed boundary conditions

An approximate technique is presented for the analysis of buckling and vibrations of free-form, orthotropic, shear-flexible (‘Mindlin’) plates subject to mixed boundary conditions. The method falls into the category of Rayleigh/ Ritz-techniques; however, by using Lagrangian multipliers to ‘relax’ the geometric boundary conditions, the selection of appropriate trial functions is made considerably simpler. Accuracy and reliability of the proposed technique is demonstrated on the basisof several sample problems.     

A computational intelligent fuzzy model approach for excavator cycle time simulation

The tracked hydraulic excavator is one of the most versatile and widely utilised piece of earthmoving equipment. In many instances, the ‘excavator’ represents the first choice of earthmoving plant for both construction managers and estimators, since when properly employed (i.e. with a competent operator and in an appropriate working environment), it offers high production rates at economical cost. Nonetheless, predicting machine production performance is difficult; given the typical multiple operational parameters (e.g. machine weight, machine configuration, ground conditions, operator ability) that can apply. Consequently, determination of accurate cost estimates and predicted contract durations are subject to considerable inaccuracy, especially where a significant amount of site work is needed.

To address this inadequacy, this paper presents a computational intelligent ‘fuzzy’ model with the ability to forecast excavator cycle time. In this context, a cycle is defined as one complete revolution, from ‘place empty bucket in dig material’ through ‘fill bucket’, ‘move charged bucket to target’, ‘empty charged bucket’ and ‘return bucket to dig material’. The developed model is based upon 70 separate cycle time observations obtained from four plant manufacturers. These data provide a representative spread of machine cycle times since they include a range on a continuum from optimum to adverse operational parameters. Tests on the derived model identified that its accuracy was acceptable; but the accuracy could be improved using larger samples and a more comprehensive and exhaustive range of variables to predict machine cycle time.     

Private owners'' perspectives

Upon reviewing the essential components of a landfill facility, focus is placed on liner system reliability, including seams. The remediation of a site is detailed illustrating that tremendous costs can be incurred as a consequence of excessive leakage. Clearly, ‘higher reliability means lower liability’. The paper concludes with a list of research goals focused on improved reliability to reduce, or eliminate, the unknowns involved in liner construction.     

An assessment of the sensitivity of lattice towers to fatigue induced by wind gusts

The dynamic properties of lattice towers are closely constrained by practical economic design. It is thus possible to generalize the prediction of dynamic response, using the stochastic wind gust model, with details as outlined in the seminar ‘Wind engineering in the eighties’ (CIRIA, London, 1980). An approximation to the combined effect of resonant and non-resonant components of the response is presented, as a factor to be applied to the effective stress range based on the dynamic response alone, computed at a single ‘reference wind speed’.

Results are presented for a range of practical structures, which indicate that good detailing can generally ensure that fatigue damage caused by wind gusts does not seriously limit design. The sensitivity of the normalized results to changes of location and of tower function and geometry is shown to be relatively small.     

Generating design activities through sketches in multi-agent systems

This study describes a multi-agent system that acts as a mediator between the designer and the information environment. The system enables designers to locate and retrieve information from distributed resources. There are three types of agents in the proposed model. The ‘user agents’ consist of designers, engineers, and technicians. The ‘information agents’ include various knowledge domains as legislation, codes, previous cases, expert domains. The ‘communication agents’ that identify and match agents are based on the goals and agent’s interest. The communication agents working over the Web use sketches as a collaboration medium in the conceptual phase of the design process. The results of the empirical study showed that the design domain and variables; and design strategies and activities are not independent of each other. The quality of a project increases as the communication increases among collaborators during the conceptual design phase and the Internet provides a suitable medium for communication through sketches.     

Development of a shredding genetic algorithm for structural reliability

Classical genetic algorithms (GA) have been previously proposed for structural reliability analysis but have not been widely adopted because of their inefficiencies. To improve the efficiency of the search process, this paper develops a modified algorithm, referred to as the shredding genetic algorithm (SGA). SGA follows the practice adopted in modern breeding technology where healthy animals are cultivated by interfering with the natural selection process and filtering out pubs with undesirable characteristics using the principle of elitism. By simulating this filtration process, SGA focuses the search around the most important genes thereby improving GA’s efficiency.Following the process used during the human genome project, the filtration criteria are established after shredding each chromosome into strings of genes each of which is associated with a fitness factor. The strings’ fitness factors are assembled into a fitness index matrix that is updated generation by generation as more information about the fitness of chromosomes is gathered. The chromosomes created during the crossover steps are filtered to eliminate those containing strings that do not satisfy a probabilistic filtration standard.Similarly to classical reliability analysis techniques, SGA identifies dominant structural failure modes and also gives detailed information about which random variables are primary contributors to the formation of these failure modes. Furthermore, SGA provides information about linkages that may exist between the random variables that control the safety of structural systems. These linkages allow the identification of sub-mechanisms or partial failures. Such useful information would eventually lead to better control of the safety of structural systems and improve the reliability of designs. Examples are provided to demonstrate the application of the proposed SGA method and its efficiency.     

An instrumented steep reinforced soil embankment at Åndalsnes, Norway

The design and construction of an instrumented steep reinforced soil embankment built over a competent foundation is described. The embankment, which is intended to act as a snow avalanche barrier, was constructed from a uniformly graded medium sand and ‘Tensar’ SR2 geogrid was used as the primary reinforcement. Reinforcement strains were measured using ‘Bison’ strain coils and measurements were also made of stresses and lateral displacements occurring in the soil. The measured values of reinforcement strain are shown to be substantially less than those obtained from a limit equilibrium analysis of the embankment in which the mobilized friction angle is based on pressure cell measurements of vertical and horizontal total stress. This result is consistent with other published field trials and indicates an excessive conservatism in the limit equilibrium methods currently used for design.     

Coupled dynamics of tensioned buoyant platforms and mooring tethers

A mathematical model is presented of the coupled dynamics of a tensioned buoyant surface platform and the lateral dynamics of its taut mooring tethers. A finite element model of the lateral mooring tether dynamics is extended to take account of nonlinear square law fluid damping by a simple global ‘whole tether’ linearization and an alternative computationally more expensive ‘element-by-element’ linearization scheme. The resultant finite element model is combined with the surface platform dynamic analysis and the coupled dynamic model is used to investigate the effects of water depth, surface platform mass and tether mass per unit length on the tether displacements and bending stresses as well as the resultant surface platform displacements. The results show that the bending stresses induced in the tethers due to their dynamic motions are quite small and that the tether dynamics only affect the motion response of the platform appreciably if the tethers are long (1500 m or more), have a large mass per unit length and have a relatively low tension; or if the platform mass is relatively small. It was also found that the additional computing time required for the local ‘element-by-element’ equivalent linearization was not matched by the small improvement in accuracy obtained over the global ‘whole tether’ technique.     

Long-term performance of geocomposites used as highway edge drains

Prefabricated highway edge drains have been widely used in the USA since 1985. Laboratory testing and initial on-site evaluations have been generally positive, however long-term performance is an unknown. The major areas of concern are ‘blinding’ of the filter fabric that would prevent water from entering into the geocomposite and the ‘clogging’ of the core with fines. This paper presents the results of 72 randomly selected sites that were excavated in 3 states representing a total of 900 000 m (3 000 000 ft) of installed geocomposite edge drain.     

The reconstruction of the Cathedral of Noto

The Cathedral of Noto, one of the most important baroque monuments that has given notoriety to the town of Noto, collapsed in the 13th of March 1996, approximately 5 years after the earthquake of ‘Santa Lucia’ that took place in December 13th 1990. The collapse has pointed out serious deficiencies in constructive materials of pilasters, even in their capacity to support vertical loads. That is why the earthquake of 1990 has acted as ‘the last blow’, coming after a long period of fatigue. Instead, the geometry of the church results to be ‘good’, and for this reason the reconstruction design consists merely in new pilasters, well made with local material, the well known ‘pietra di Noto’ and the replacement is going to take place both on the right, in the place of the collapsed pilasters, and on the left, in substitution of the old pilasters, really not adaptive for restoration. In this way, and with few other interventions, the ‘new’ church should result capable to resist to earthquakes similar to the one that occurred in 1693.