Acceptable Design Solutions Research Articles

Scientific basis for the development of structural and technological devices made of modern domestic materials to ensure the functional reliability and safe operation of surface water intakes

The article provides a classification list of a large number of heuristic techniques for solving various problems of designing a class of hydraulic structures, taking into account the conditions of functional operation of soft floating structures (MNCs) as water intake structures. The concept of rational use of surface water resources provides for an ecosystem approach that allows us to consider a water body together with the catchment area of the hydrographic river network, the surface layers of the atmosphere above it, measures taken to select the calculated water flow rate (Q m3/s), taking into account the consideration of environmental safety in the zones of influence of water intake - as a single system in as a whole. Providing EC in VTK puts forward a number of main tasks to improve existing structural and technological devices and create new ones using modern domestic materials, for example, high-strength synthetic fabric materials. When creating environmentally acceptable design solutions to provide EC in the zones of influence of VTK, one of the most promising areas at present is the methodological basis for the synthesis of soft-coated structures in the composition of VTK. The reliable functioning of both a separate structural element and the structure as a whole should be conditioned by the possibility of periodic updating of its constituent structural elements.

Multi-criteria performance-based optimization of friction energy dissipation devices in RC frames

A computationally-efficient method for multi-criteria optimisation is developed for performance-based seismic design of friction energy dissipation dampers in RC structures. The proposed method is based on the concept of Uniform Distribution of Deformation (UDD), where the slip-load distribution along the height of the structure is gradually modified to satisfy multiple performance targets while minimising the additional loads imposed on existing structural elements and foundation. The efficiency of the method is demonstrated through optimisation of 3, 5, 10, 15 and 20-storey RC frames with friction wall dampers subjected to design representative earthquakes using single and multi-criteria optimisation scenarios. The optimum design solutions are obtained in only a few steps, while they are shown to be independent of the selected initial slip loads and convergence factor. Optimum frames satisfy all predefined design targets and exhibit up to 48% lower imposed loads compared to designs using a previously proposed slip-load distribution. It is also shown that dampers designed with optimum slip load patterns based on a set of spectrum-compatible synthetic earthquakes, on average, provide acceptable design solutions under multiple natural seismic excitations representing the design spectrum.

Analysis of the mechanism of transition to the limit state of Series 111 residential buildings during the 1988 Spitak earthquake

The study aimed at investigating the reaction of a residential building (Series 111 nine -story block section ) to seismic impacts that can lead to destruction of the building . The article presents the results of the retrospective analysis of the seismic resistance of nine -story block sections in the city of Gyumri (Leninakan) under the influence of the 07.12.1988 Spitak earthquake . The seismic resistance of the block section wa s calculated using the ‘ pushover analysis ’ method . D irect dynamic calculation s were performed using a model of complex elastoplastic deformation of a mechanical system with two degrees of freedom. A n external impact was represented by the earthquake records taken at the Ghukasyan station . M acroseismic survey data collected after the 1988 earthquake are presented. T he block sections of Series 111 multistory residential buildings were designed by the Armenian research and design institutions ArmNIISA and Armgosproekt in 1975 for construction in the Armenian Republic on sites with seismicity of 7–8 points. V ibration tests were conducted to test the strength of a nine -storey block section in Yerevan in 1976, and it was discovered that the actual seismic resistance of the building d id not comply with the current earthquake-resistant construction standards. However, the test results were ignored . O n December 7, 1988 , the earthquake took place, and the Series 111 buildings collapsed in the cities of Gyumri (Leninakan) and Vanadzor (Kirovokan). In the State Commission Report regarding the Series 111 design , it was concluded that considering the damage due to the violations of the design and construction standards and taking into account the inspection calculations , the accepted design solutions of the residential buildings d id not meet the requirements of the regulatory documents for buildings designed to sustain seismicity of 8 points. Such design should not be used for seismic areas and must be critically revised . The retrospective analysis performed by the authors of th is article on the basis of experimental data not only confirmed the conclusions of the State Commission, but also made it possible to establish a mechanism for the transition of Series 111 block-section s to the limit state. Unfortunately, the state management of the construction industry failed to use this information and did not take any urgent preventive actions. In fact, t he authorities of the USSR supported the position of the Gosstroy of Armenia and allow ed them to continue the construction of Series 111 residential buildings with minor changes. I t was impossible to prevent the Spitak earthquake, but proper preventive actions could have reduced the amount of social and economic damage incurred due to the earthquake . The consequences of obvious design and construction errors discovered 12 years before the Spitak earthquake were ‘ written off ’ and explained by the natural disaster, including underestimated standard seismicity, features of the engineering-geological s ettings , and the unfavorable spectr um of the actual impact. T housands of people lost their life, and huge material damage was caused due to the loss of Series 111 residential buildings ( 300 000 square meters) . Such was the price of professional incompetence and departmental ambitions.

RELIABILITY-BASED SELECTION OF STANDARD STEEL BEAMS

A reliability-based design approach using sensitivity analysis is presented for the selection of standard steel beams subjected to concentrated and or distributed loads, assuming lognormal probability density function. Serviceability criteria of bending stress, transverse deflection, and web maximum shear stress are considered. The load, strength, and geometric parameters are considered to be log normal in distribution. Equations are developed for the coefficients of variation for the mentioned serviceability criteria so as to determine design reliability. Deterministic design equations are transformed into probabilistic ones by replacing the traditional “safety factor” with a “reliability factor”. The reliability factor is determined from a specified reliability goal and the coefficients of variation in design models and parameters. Design examples are presented and results are compared with solutions based on the traditional ASD (Allowable Stress Design) method. Two of the four design examples have identical solutions with the ASD method. The third example result is practically the same as that of ASD method, except that the beam is slightly lighter. The fourth example has a similar result as the ASD method but the beam is deeper. The deeper beam solution stems from the use of both bending stress and deflection serviceability criteria in the new approach while only the bending stress criterion was used in the ASD method. All the chosen beams indicate a reliability of at least 99.73% for bending stress and at least 95.22% reliability for deflection. In all the chosen beams, the web maximum shear stress has a reliability factor of at least 4.91, making shear failure improbable. The agreement between the results of these different methods is amazingly interesting. All computations in the study were done on Microsoft Excel Spreadsheet, demonstrating that probabilistic design can be done with inexpensive computer resource and not too advanced analytical skills. This study shows that acceptable design solutions can be achieved by modification of deterministic or traditional design method through probabilistic consideration of “design or safety factor”. From the very favorable comparison of the results between the new approach and ASD method, it appears reasonable to conclude that the method proposed in this paper is satisfactory for the probabilistic design of standard steel beams. The covs for practical design applications should be based on data from material vendors and historical data on loads. Engineering companies providing design services would have such data and a simple statistical analysis will give realistic cov values for use in their design practice.

Reliability-based evaluation of the inherent safety presumptions in common fire safety design

The structural safety of a simply supported one-way concrete slab exposed to the ISO 834 standard fire curve is investigated. The proposed methodology allows for an objective comparison of the structural performance of different concrete slab design alternatives and to derive indirectly a lower bound of the fire ignition frequencies that can be associated to the Eurocode guidelines. A comparison is made with empirical fire ignition frequencies found in literature and a detailed study is presented of the significance of the concrete cover and its uncertainty on the safety level and fire resistance time. Results indicate that the safety level during fire and the fire resistance time are both highly sensitive to the ratio of the variable to the permanent load and that the accepted design solutions given in EN 1992-1-2 are rather conservative.

Whole life sustainability in the design of tourist resorts

PurposeThe purpose of this paper is to argue that it is possible to identify a number of physical design properties of plots that are associated with coastal alteration and to develop a predictive model or metric to evaluate the potential alteration caused by that resort. Investors may have economic plot size concerns not considered by planners, tourists may prefer close proximity to deep waters, and urban planners may have failed to realize the importance of certain plot ratios or minimum dimensions etc.Design/methodology/approachA combination of geographical information system and statistical tools is used to identify and model these properties. The research uses data from three different resorts in two countries along the Red Sea coast (Hurghada and Safaga in Egypt and Jeddah in Saudi Arabia). Landsat TM7 images are obtained for each location and analysed to detect regions with the largest alteration along the coast using the post‐classification change technique. Physical properties of each village are generated using ArcGIS 9.2 both before and after alteration. Finally, a predictive decision‐support tool for urban planners and environmental auditors is formulated using stepwise discriminant analysis.FindingsTwo‐step cluster analysis and discriminate analysis show that alteration takes place based on factors that include original width and original distance to deep water in three distinct groups. The predictive model that is developed classifies any given resort into one of three clusters, by virtue of their physical design characteristics. This gives a rough prediction of the likely alteration that might take place under a given condition. Subdivision plans that ignore the power of these two factors literally “invite” owners to violate shorelines and encroach on the sea. Planners are urged to join hands with policy makers and developers to formulate guidelines to plot subdivision and environmentally acceptable design solutions to facilitate access to deep water.Originality/valueTill now, there has been no metric to relate a plot's geometric properties with the encroachment it makes. If such an association could be made, a developer's resort plans may be evaluated to predict the degree by which an encroachment is likely. The model can be used to identify resorts whose properties present a risk to shorelines, dredge or fill to maximize usable land. Two benefits may be thought of for this approach. First, the model helps urban planners develop a sustainable coastal area by bearing in mind the needs of tourist‐developers as well as the properties of their adjacent coast. Second, the factors can be used to rationalize building guidelines and land use regulations to minimize such risk.

An Advanced Computational Approach to System Modeling of Tokamak Power Plants

A new computational model for fusion power plant system studies is being developed for the ARIES program. An operational design space has been created to explore the most influential parameters in the physical, technological and economic trade space related to the developmental transition from experimental facilities to viable commercial power plants. This allows examination of a multi-dimensional trade space as opposed to traditional sensitivity analyses about a baseline design point. The influence of multifunctional, highly dependent parameters can easily be visualized, which may highlight one or a few difficult-to-achieve parameters that would yield a highly acceptable design solution. The new ARIES systems code consists of adaptable physics, engineering and costing modules which capture the current tokamak knowledge database and reflect both near-term as well as advanced technology solutions that are higher risk but have higher performance potential. To fully assess the impact of the range of physics and engineering implementations, the plant cost accounts have been revised to reflect a more functional cost structure. All of these features have been validated against the highly respected ARIES-AT baseline. The present results demonstrate novel visualization techniques for trade space assessment of attractive tokamaks for commercial use.

Conversational grounding and visual access in collaborative design

The present study investigates the role of visual access in supporting the exchange of positive evidence of mutual understanding in collaborative design. Pairs of designers worked on two design problems differing in the mix of gestural and speech cues needed to signal mutual understanding, either in full view of each other, or within each others' hearing but without shared visual access to each others' design activities. Designers' use of conversational speech, gesture, and representational media varied systematically as they adjusted to the loss of visual access. Nevertheless, they did achieve acceptable design solutions under these conditions. The changing patterns of conversational and workspace activity we observed have the potential to inform the design and application of augmented reality interfaces that attempt seamlessly to blend real and virtual images and objects, and we draw out some human factors implications of these interfaces for helping designers think and share design ideas.

A generalized performance sensitivity synthesis methodology for four-bar mechanisms

A generalized accuracy performance synthesis methodology for planar closed chain mechanisms is proposed. The relationship between the sensitivity to variations of link lengths and the location of the moving pivots of four-link mechanisms is investigated for the particular objective of three and four position synthesis. In the three design positions case, sensitivity maps with isosensitivity curves plotted in the design solution space allow the designer to synthesize a planar mechanism with desired sensitivity value, or to optimize sensitivity from a set of acceptable design solutions. In the case of four design positions, segments of the Burmester design curves that exhibit specified sensitivity to link length tolerance are identified. A performance sensitivity criterion is used as a convenient and a useful way of discriminating between many possible solutions to a given synthesis problem.

A prototype expert system for the conceptual synthesis of thermal processes

An expert system capable of assisting the process engineer in thermal processes design selection can improve both the quality and the variety of the solutions proposed. Conceptual design is part of the engineering design process which converts design requirements into an acceptable design solution. Nowadays, engineering design problems have become more and more complex and the increasing complexity has made synthesis a very difficult task: it is during this stage of the design process that the creativity and experience of an engineer are most needed. Inappropriate component requirements and/or coupling can significantly reduce the capability of a process to meet design demands. The prototype presented in this paper (COLOMBO) is an attempt to show that an expert system can be of valid help in finding answers to conceptual process selection. An exhaustive search across the data base allows the user to evaluate plant configuration constituted by virtually every technically feasible combination of components. Generally, the problems under exam result in a goal-driven search process and, therefore, a backward chaining approach is used here. The data base has been subdivided into two main classes: equipment and resources. Each “equipment” object has in-flows and out-flows (energy, matter,…) which define its operational capabilities. Interconnection of these objects is possible when there is compatibility between the out-flows of one and the corresponding in-flows of the next object. Of course, connectivity must satisfy all the constraints imposed to the problem domain. Presently only a few components have been included in the data base and, therefore, only few conventional configurations are produced by the expert system. Nevertheless COLOMBO produced four configurations for a power generation plant and three process configurations for a cogeneration plant which resolve to be equivalent to the human expert choices.

The demise of military standards may affect ergonomics

Anticipating reduced emphasis on human factors engineering, some companies have already cut back on human factors engineering staff. A consortium of defense industries, spearheaded by the electronics firms who were required by military specification and standards to maintain separate production lines for military components, has persuaded the Secretary of Defense to direct that military specification and standards should not be used, or if used, to require special permission by high-level officials. Clearly, electronics, or any other rapidly evolving technology should not be constrained by inappropriate standards. In the rush to economize, has it been forgotten that the human operator or maintainer has not evolved significantly in the last hundred years? The human factors engineering standards embody the lessons learned over the past 40 years into acceptable design solutions, as well as much of what we think of as systems safety. Both government and industry have worked to keep these standards up-to-date and relevant.

Intelligent design synthesis: an object-oriented approach

Conceptual design is a process of converting design requirements into an acceptable design solution. An object-oriented system for conceptual design is presented. The process of component synthesis is guided by production rules. An object-oriented programming paradigm is chosen since it simulates the designer's way of thinking during conceptual design. The system is implemented in Smalltalk-80 programming language and environment. Besides providing all the characteristics of an object-oriented language, Smalltalk-80 allows for development of highly user-friendly interfaces. The design synthesis process is presented using a graphical and textual description.

Multifunctional Material System Design

The design of multifunctional material systems is presented as a multivariable, multicriteria optimization problem, and a formalized methodology which makes no implicit preference, independence, and convexity assumptions is proposed for its solution. The methodology utilizes dynamic programming with Pareto optimization, cluster analysis, and inverse goal programming to identify a subset of acceptable design solutions. It takes into consideration the properties of materials and relates these to various functional requirements of building enclosure. Functional performances under consideration are thermal, resource conservation, structural, economic, and space utilization. An illustrative material system design example is included in detail to show how various conflicting functional requirements can be taken into account simultaneously and generate qualitative and quantitative information to aid the designer in making decisions.

Glenwood Canyon I‐70: Environmental Concern

Environmental concerns and physical constraints involved in the design of Interstate 70 through Glenwood Canyon, a scenic river gorge in Colorado, resulted in a design approach unique for highway projects. The Highway Act of 1976, which allowed variance from interstate standards, led to a complex and lengthy process to develop a functional and environmentally acceptable design solution. The design process is examined and several elements of the design solution are described, including terraced roadways, cantilevered roadways, retaining walls, tunnels, and a comprehensive revegetation program. The unique design process has resulted in an environmentally sensitive highway design, but the delay in implementation significantly increased the cost of the project.

What if? Exploring the consequences of design and performance decisions in computer-aided design

A fundamental part of design is the process of prediction and postulation. A designer attempts to predict the performance consequences of his design decisions and postulate the design decisions which will lead to desired performance results. This paper describes a formalised methodology in computer-aided design which provides a framework for exploring such design and performance relationships for multi-variable multi-objective problems. The concept of inverse goal programming is introduced as a means of operating on the Pareto set to identify a subset of acceptable design solutions. An example of this approach applied to the design of multi-functional materials is presented in detail.

Operating experience gained with the hydraulic structures and equipment of the Narva hydroelectric station

1. Operating experience at the Narva hydroelectric power station has confirmed the accuracy of a majority of accepted design solutions. The successful operation of the station is attributed to high-quality workmanship. 2. Basic problems associated with the elimination of equipment and hydraulic-structure shutdowns were solved during the previous operating period. 3. Work is constantly in progress at the station to upgrade the efficiency of the water use and the reliability of the equipment.