Practical Design Tool Research Articles

Probabilistic bearing serviceability of drilled shafts in randomly stratified rock using a geostatistical perturbation method

The bearing stiffness (i.e., the slope of load-displacement curve at the tip) of drilled shaft foundations is an important serviceability-design parameter, especially for rock-socketed application of shallow embedment depths. Numerical solution techniques, such as finite element analysis (FEA) models, provide useful tools for investigating the bearing (tip) stiffness under various boundary conditions both homogeneous and heterogeneous. However, for uncertain and spatially heterogeneous mechanical input parameters, computational costs are high when meaningful statistical parameters of tip stiffness are to be obtained from full Monte Carlo FEA simulations. In the present work, an analytical expression for a one-dimensional, linear load-displacement relationship is derived by making use of perturbation analysis on randomly-stratified rock layers and their effects in the development of the tip stiffness using two-dimensional axisymmetric FEA. Numerical results show that spatial variability in both elastic modulus and undrained shear strength (cohesion) of supporting rock layers affect tip stiffness. However, the influence of cohesion on expectation and uncertainty of tip stiffness may be safely neglected for serviceability design. The tip stiffness of a drilled-shaft foundation is found to be highly proportional to the harmonic average of elastic moduli with averaging weights decreasing exponentially from the shaft tip downward. Exponentially-weighted harmonic averaging of elastic moduli is then incorporated in Winkler models to reasonably predict the results of full Monte Carlo FEA for cases where (1) a depth profile of elastic modulus is available at the footprint of a shaft, and (2) only geostatistical characteristics (i.e., expectation, variance, correlation length) of elasticity of rock are known a priori at a construction site. The presented closed-form solution is in good agreement with predictions of Monte Carlo FEA, and thus, may offer a practical alternative tool for the serviceability design.

NaviGaTor: group decision-making methodology for the design of training programs

Purpose – The purpose of this paper is to present a systematic methodology (NaviGaTor) combining a structured method for the evolutionary design of training programs with Nominal Group Technique (NGT) setting supporting the involvement of a diverse set of participants and experts. Design/methodology/approach – The paper describes the necessity and efficiency of group decision making in the design of training programs, focussing on how participants can convey experience and knowledge and how NGT can enhance idea generation and support convergence of opinions. The methodology evolved from a paper-based format to a web-based format, thus supporting remote participation. Findings – The application of the methodology in a large-scale multi-national training design program confirms practical implications on the usability, efficiency and effectiveness of the proposed structured group decision-making methodology. Research limitations/implications – The systematic training design methodology presented herein not only enhances previous findings from the literature but also sets the foundations for future research on the importance of diversity of ideas and experiences from many experts in the design of training programs. Practical implications – After a series of successful applications for the design of training programs in several mid-scale intra-company projects, the methodology was applied successfully in a multi-national large-scale project focussing on the design of corporate training programs on stress management with very promising results. Originality/value – The proposed methodology was the first one to be applied through a systematic and structured process and constitutes a practical tool for the efficient design of training programs through an evolutionary and structured process based on idea generation from experts.

A Parametric Study on Friction Instabilities in Mechanical Face Seals

ABSTRACTThe present article aims to analyze and evaluate how dynamic parameter design influences the behavior of mechanical face seals and improves their performance by detecting undesirable phenomena like stick–slip and ringing. Those phenomena occur in situations of boundary lubrication.A new lumped parameter model is proposed to study mechanical face seals used in automotive cooling water pumps in order to examine how dynamic parameters such as mass, moment of inertia, and stiffness are involved in stick–slip phenomena. The aim of this work is to provide a practical design tool to predict stick–slip conditions and to choose the optimal mechanical specifications. Numerical simulations demonstrate how the critical service conditions vary with design parameters and permit tabulation of the results.

Bimetal cup hydroforming of Al/St and Cu/St composites: Adaptive finite element analysis and experimental study

An adaptive Finite element analysis (FEA) was proposed in this paper for the industrial design of bimetal conical-cylindrical cup hydroforming. Forming circumstances for the perfect and imperfect parts were concluded through adaptive FEA using the ANSYS parametric design language. Effective parameters, including pressure loading path, layer placement order, and thickness ratio, were investigated for hydroforming of Al/St and Cu/St composite sheets. Experimental tests were implemented to validate adaptive finite element results. Rupture failure upon the pressure path occurred on the contact area between the blank and punch tip radius at low pressures and on the transition area of the conical-cylindrical portion at high pressures. The proposed method is applicable for any cylindrical, conical, or cylindrical/conical shapes with different materials and dimensions. Therefore, this method is beneficial as a practical design tool for engineers and researchers working in the process design of hydroformed shell products.

New formulas for calculating mode II fracture energy of several typologies of GRP pipes under impact

Abstract The authors suggest a simple monomial formula to determine the delamination starting energy U0 under impact in GRP pipes with sand filled layer. By means of analytical procedures, deducted from the Mechanically Contaminated Layer Theory, a new equation in mode II of fracture, unique for all types and different manufacturers is developed. The shape of this equation adjusts in a 98.96% of the observed law and mainly depends on the square of the height of the tube and its resistance to internal hydraulic pressure, achieving numerical errors, using a general theoretical coefficient, of less than 10% for pipes of very different kinds, that can be improved using empirical coefficients customized for each manufacturer. Thus, it facilitates technicians with a practical design tool against the invisible effects of a blow and warrants seriously rethinking the current design criteria that does not take into account the brittleness of an impact.

Between Looking and Making: Unravelling Dom Hans van der Laan’s Plastic Number

Between 1920 and 1991, the Dutch Benedictine monk and architect Dom Hans van der Laan (1904–91) developed his own proportional system based on the ratio 3:4, or the irrational number 1.3247. . ., which he called the plastic number. According to him, this ratio directly grew from discernment, the human ability to differentiate sizes, and as such would be an improvement over the golden ratio. To put his theories to the test, he developed an architectural language, which can best be described as elementary architecture. His oeuvre — four convents and a house — is published on an international scale. His buildings have become pilgrimage sites for practicing architects and institutions that want to study and experience his spaces. His 1977 book Architectonic Space: Fifteen Lessons on the Disposition of the Human Habitat , translated into English, French, German and Italian, still inspires architects today, as does his biography, Modern Primitive , written by the architect Richard Padovan in 1994. But beyond the inspiration of his writings and realisations, the actual application of the plastic number in Van der Laan’s designs is unclear. Moreover, Van der Laan’s theories seem to be directed towards one goal only: to present the plastic number as the only possible means by which eminent architecture can be achieved, making them a target for suspicion and critique. To understand and evaluate Van der Laan’s application of the plastic number, this paper approaches it as a practical design tool. It analyses its genealogy and defines its key concepts. From that framework, Van der Laan’s architectonic space is interpreted as a design methodology that combines antique tectonic theories reminiscent of writers from Plato to Vitruvius with more recent atectonic approaches towards space through experience and movement.

Temporal evolution modeling of hydraulic and water quality performance of permeable pavements

Summary A mathematical model for predicting hydraulic and water quality performance in both the short- and long-term is proposed based on field measurements for three types of permeable pavements: porous asphalt (PA), porous concrete (PC), and permeable inter-locking concrete pavers (PICP). The model was applied to three field-scale test sites in Calgary, Alberta, Canada. The model performance was assessed in terms of hydraulic parameters including time to peak, peak flow and water balance and a water quality variable (the removal rate of total suspended solids). A total of 20 simulated storm events were used for model calibration and verification processes. The proposed model can simulate the outflow hydrographs with a coefficient of determination ( R 2 ) ranging from 0.762 to 0.907, and normalized root-mean-square deviation (NRMSD) ranging from 13.78% to 17.83%. Comparison of the time to peak flow, peak flow, runoff volume and TSS removal rates between the measured and modeled values in model verification phase had a maximum difference of 11%. The results demonstrate that the proposed model is capable of capturing the temporal dynamics of the pavement performance. Therefore, the model has great potential as a practical modeling tool for permeable pavement design and performance assessment.

Application of a Key–Value Paradigm to Logic Factoring

Over three decades ago an algebraic factoring algorithm was created as part of active logic synthesis efforts in the semiconductor industry. It initiated logic synthesis successes and steered synthesis in the direction of practical design tools: they can now take a design from its initial state to the final chip that meets a complex set of constraints. The evolved computing platforms today stimulate new exploratory avenues to extend the functionality of fundamental synthesis algorithms. We reexamine logic factoring in an effort to establish a stronger connection to the functional intent rather than structural implications of a design description within synthesis. A scalable factoring algorithm that reduces its dependence on the two-level minimization is described to improve the area of synthesized circuits. It is implemented using a new distributed environment that harnesses the key-value concept to find solutions through systematic transformations of a data set.

New formulas for the tortuosity factor of electrochemically conducting channels

Abstract Porous composite mediums consisting of multiple interpenetrating percolating phases are widely used in electrochemical cells and batteries. The electrochemical species, for example electrons, ions, and gaseous molecules, are confined to transport within the specific conducting phase networks. Our ability to understand physical and chemical processes within these tortuous networks is often limited by the lack of suitable mathematical representation of their tortuosity factor. Thus, the quantitative formulation of tortuosity factor is urgently needed in this regard. From purely geometric perspectives, this work has proposed new formulas to calculate the tortuosity factor for a single conducting channel and a bundle of channels, using the coordinates of the channel central line and the channel radius distribution along the channel central line. The formulas are easy to use and statistically identical to the ideal value of tortuosity factor. The new formulas can serve as a practical tool for analysis and rational design of the three-dimensional conducting networks.

CFD Benchmark Tests for Indoor Environmental Problems: Part 4 Air-conditioning Airflows, Residential Kitchen Airflows and Fire-Induced Flow

Computational Fluid Dynamics (CFD) has become practical design tool for indoor environment recent years and the application cases have been increasing. Though the improvement of the prediction accuracy of CFD is needed in connection with the upgrade of design quality in indoor environment and Heating, Ventilation and air-conditioning (HVAC) system, the prediction accuracy of CFD simulation depends on the understanding for the fundamentals of fluid dynamics and the setting of appropriate boundary and numerical conditions as well. Additionally, deeper understanding to a specific problem regarding indoor environment is also required. The series of this study aimed to provide with the practical information such as prediction accuracy and problematic areas related to CFD applications in air conditioning and ventilation, then performed benchmark tests and reported the results. Especially in this Part 4, benchmark test results for Air-conditioning airflows, Residential kitchen airflows and Fire-induced flow were introduced and discussed.

A novel Friday 13th risk assessment of fuel-to-steam efficiency of a coal-fired boiler

A novel Friday 13th (Fr 13) risk assessment is used for the first time to investigate the fuel-to-steam efficiency of a coal-fired-boiler (CFB). The aim was to quantitatively determine the risk to reduced CFB efficiency in the face of naturally occurring random (stochastic) changes in key parameters. Data from a new commercial plant in East Java, Indonesia are used. The approach was to define an underlying unit-operations model based on the indirect heat-loss method, together with an efficiency risk factor (p). Process behaviour is simulated using a refined Monte Carlo (Latin Hypercube) sampling of 20 key input parameters that include coal feed and quality. The CFB is expected to operate at an efficiency of η=82.82%. Below 77.82% the process is characterized as ‘fail’ due to the greater coal needed to produce steam quantity and quality, and the potential for damage to the boiler. Results reveal an underlying risk of 73 failures in CFB efficiency per 10,000 operations. This equates on average to three failures each year over a prolonged period. This new information cannot be obtained from alternative hazard and risk approaches. A number of changes to the CFB to cut efficiency failures are illustrated using Fr 13 methodology. It is shown to be a practical design tool for improving process reliability and costs. A major benefit is that it can be used in design synthesis and analysis. Findings will be of benefit to operators and manufacturers of boiler equipment.

Modeling of the hydrodynamics and energy expenditure of oxidation ditch aerated with hydrojets using CFD codes

This work uses computational fluid dynamics (CFD) as a design tool in wastewater treatment modeling practice to assess the specific use of the hydrojets in oxidation ditches. The hydrodynamics and the residence time distribution in an oxidation ditch are simulated using several turbulence models: Reynolds averaged Navier–Stokes simulations (RANS) and unsteady RANS with the standard k ‒ e model; and large eddy simulation with the Smagorinsky subgrid scale model. The influence of the mesh resolution, of the hydrojets placement on the oxidation ditch hydrodynamics and on the energy demand for mixing is assessed. Finally, the effect of the turbulence models on the macromixing data, which can be implemented in the activated sludge model, is also evaluated.

Performance in Fire of Fibre Reinforced Polymer Strengthened Concrete Beams and Columns: Recent Research and Implications for Design

This paper considers the fire performance of concrete beams and columns that have been strengthened with fibre reinforced polymers (FRPs). Results from four recent full-scale tests are presented. A newly developed type of insulation was employed and the thickness of the insulation (15 to 20 mm) was approximately half that provided in earlier tests. All of the members survived four hours of the fire exposure. A conceptual model for design to determine when insulation is required is also presented. Further research needed to fully develop the conceptual model to a more practical design tool is outlined.

Lateral displacement of PVD-improved deposit under embankment loading

ABSTRACT: The likely range of values of the maximum lateral displacement of the ground caused by embankment loading of a soil deposit improved by the installation of geosynthetic prefabricated vertical drains (PVDs) was investigated. This involved a study of 18 field cases and an empirical equation for predicting the maximum lateral displacement is proposed. The proposed equation considers the effects of the embankment load, loading rate, and the deformation, consolidation and strength properties of the soft subsoil. Combining the proposed equation with a previously established equation for predicting the lateral displacement of soft soil deposits under the combined action of embankment and vacuum pressure loading provides a method for estimating the likely range of values of the maximum lateral displacement of a PVD-improved deposit under embankment loading with or without the application of vacuum pressure. It is suggested that the proposed method can be used as a design tool in geotechnical practice.

Buckling of spherical cap gridshells: A numerical and analytical study revisiting the concept of the equivalent continuum

The use of gridshell structures in architecture and structural engineering has risen in the past decade, yet fundamental research on the mechanics of such structures is lacking. The majority of gridshells built use either quadrilateral or triangular grids. In this paper, we assess the effect of the grid shape (triangular or quadrilateral), the grid spacing, and the span-to-height ratio on the failure load of spherical cap gridshells. The failure load is calculated using finite element methods and analytical methods derived from the equivalent continuum. Both a linear eigenvalue and a nonlinear analysis using geometric imperfections are performed and compared. While a triangular grid is expected to be greater in structural capacity, it is found that for shallower shells there is less of a structural advantage to using a triangular grid. Further, the triangular grid is highly sensitive to imperfections whereas a quadrilateral grid is not. The equivalent continuum defined by area equivalence provides a conservative estimate for the buckling load and multiple definitions of the equivalent continuum can be used to establish a practical design tool in the early phases of design. By understanding the fundamental mechanical behavior of gridshells, design guidelines aimed to maximize their capacity and efficiency and intended to facilitate the discussion between architect and engineer are proposed.

Numerical investigation of the influence of texture, surface drip emitter discharge rate and initial soil moisture condition on wetting pattern size

Knowledge of the dimensions of the wetted zone formed under point source surface drip irrigation is essential to the design of cost-effective and efficient irrigation systems. Numerical simulations were carried out with Hydrus-2D/3D to investigate the influence of emitter discharge rates and initial soil moisture conditions on the wetting pattern dimensions of a series of soils with varying textures. Numerical simulations of simple 2D soil tank irrigation experiments were also conducted on two soil types. Based on the simulation results, the parameters of the Schwartzman and Zur model were refined. The results showed a small influence of discharge rates >1 L h−1 on the size of the wetting pattern. The only major difference was observed for the rates lower than 0.5 L h−1, where the largest wetting patterns were observed. Higher initial soil water content caused larger wetting pattern sizes in all directions. When compared to the 2D tank experimental results, Hydrus-2D/3D predicted the wetting pattern dimensions with a relatively small root mean square error not exceeding 2.6 cm. The numerical data obtained for a wide range of textures provided the opportunity to refine the parameters of the Schwartzman and Zur model, which, when compared to experimental data from the literature, provided good estimates of wetting pattern dimensions. This suggests that this simple model, for which the only soil parameter required is the saturated hydraulic conductivity, could provide a valuable and practical tool for irrigation design.

Practical use of computational fluid dynamics (CFD) in improving the efficiency of domestic ventilation waste heat recovery systems

Efficiency of domestic ventilation waste heat recovery systems (WHRS) depends not only on the amount of waste heat recovered, but also on the energy involved in running fans to drive air through the system. Computational fluid dynamics (CFD) can be a powerful tool for analysing WHRS losses (thus predicting fan energy usage), but the computational effort involved can limit the value of CFD as a practical design tool. This study presents a range of assumptions and simplifications that can be applied to reduce the computational effort associated with the CFD analysis of a WHRS. The importance of experimental validation to assess the effect of errors introduced by the simplifying assumptions is discussed. In an example case, application of the methods presented have allowed total pressure losses (excluding the fixed losses through the heat exchanger) to be reduced by over 50 % in comparison with an initial prototype design, with proportional reduction in fan energy usage. This highlights the value of sufficiently simplified CFD analyses within a typical WHRS product development cycle.

About Merging Threshold and Critical Flux Concepts into a Single One: The Boundary Flux

In the last decades much effort was put in understanding fouling phenomena on membranes. One successful approach to describe fouling issues on membranes is the critical flux theory. The possibility to measure a maximum value of the permeate flux for a given system without incurring in fouling issues was a breakthrough in membrane process design. However, in many cases critical fluxes were found to be very low, lower than the economic feasibility of the process. The knowledge of the critical flux value must be therefore considered as a good starting point for process design. In the last years, a new concept was introduced, the threshold flux, which defines the maximum permeate flow rate characterized by a low constant fouling rate regime. This concept, more than the critical flux, is a new practical tool for membrane process designers. In this paper a brief review on critical and threshold flux will be reported and analyzed. And since the concepts share many common aspects, merged into a new concept, called the boundary flux, the validation will occur by the analysis of previously collected data by the authors, during the treatment of olive vegetation wastewater by ultrafiltration and nanofiltration membranes.

A Practical Tool for the Preliminary Design of Bonded Composite Repairs

Composite structures are increasingly finding more applications in the aeronautical field as well as the automotive one, thanks to their low weight – performance ratios, in terms of strength and stiffness. However, composite materials, as well known, are characterized by a critical behavior in terms of detectability of damage and performances of damaged components. A critical aspect related to damaged composite structures is, for sure, the repair aimed to restore the original stiffness and strength characteristics of the component depending on the damage typology and location. In this paper, a preliminary repair design tool is presented. The tool is aimed to help the designer by suggesting different repair typologies and proper repair size. This tool, by means of optimization analyses can provide the best repair solution with minimal adhesive shear stress and size of the repair patch. The tool has been tested against a literature case study on multistep composite-metal joints.

Electro-thermal compliant mechanisms design by an evolutionary topology optimization method

Purpose – This paper aims to show an evolutionary topology optimization procedure for the design of compliant electro-thermal mechanisms. Design/methodology/approach – The adopted methodology is based in the evolutionary structural optimization (ESO) method. This approach has been successfully applied by this group for compliant mechanisms optimization under directly applied input loads and simple thermal loads. This work proposes an extension of this procedure, based on an additive version of the method, to solve the more complicated case of electro-thermal actuators optimum design, based on Joule's resistive heating. Findings – Examples solved for the design of plane compliant mechanisms are presented to check the validity of this technique. The designs obtained are compared favorably with results obtained by other authors to illustrate and validate the method, showing the viability of this technique for the optimization of compliant mechanisms under electro-thermal actuation. Research limitations/implications – This investigation is based on and additive version of the evolutionary method. Since this approach does not have the capability to remove material it could be combined with the classic element rejection evolutionary method to overcome these deficiencies, developing an improved bi-directional algorithm, which should be analyzed and applied for these types of designs in future works. Practical implications – Electro-thermal actuators have widespread use in MicroElectroMechanical Systems applications. Since these elements cannot be manufactured using typical assembly processes compliant mechanisms optimization play a crucial role for their successful design. The proposed methodology could help engineers to rapidly conceive complex and efficient actuators. Social implications – The topology optimization procedure developed in this paper enables systematic design of these devices, which can result in a save of manufacturing time and cost. Originality/value – Most applications of the ESO method have considered maximum stiffness structure design, and even if it has been successfully applied to some other optimum material distribution problems, electro-thermal actuators design has not been considered yet. This paper shows that this methodology could be useful also in the design of electro-thermal compliant mechanisms, and provides engineers with a very simple and practical alternative design tool.