Reliable Design Method Research Articles

The Actualities and Development of Fatigue Reliability Design Methods of Pressure Vessels

Petrochemical pressure vessel equipment develops to be large-scale and super large-scale under extreme working conditions such as high temperature and high pressure, which puts forward new demands for the reliability of the pressure vessel. The present paper discusses the fatigue design theory of pressure vessels and analyzes the fatigue design methods of ASME, BS5500 and JB4732. Pressure vessel loads absorbed (pressure, temperature, earthquake, wind, snow, etc.) have significant stochastic dynamic characteristics and coupling characteristics. The random load of the current design is simplified, with a large safety factor in exchange for equipment safety. However, it is difficult to guarantee the rationality and accuracy of the result. With the development of data acquisition, processing and finite element technology, it is inevitable to be based on measured load spectrum and consider the coupling of the random loads to work out fatigue reliability design methods of pressure vessels.

Calculation of moment capacity of cold-formed steel members

The growing of application of cold-formed steel in building industries requires the development of not only simple but also reliable design methods. This paper provides an overview on the recent development in determining the moment capacity of cold-formed steel members with a particular focus on the calculation of bending strength due to local, distortional and lateral-torsional buckling. Methods used to calculate the critical stresses of local, distortional and lateral-torsional buckling are addressed and compared. The design methods for determining the bending strength corresponding to these buckling modes are also described briefly.

Direct Displacement Based Design of Regular Steel Moment Resisting Frames

Displacement Based Design method represents a new approach to performance-based design. This research tries to assess the Direct Displacement Based Design (DDBD) method for regular steel moment resisting frames and develop a reliable design method for them so that they withstand various seismic levels within certain performance levels. For this purpose, regular steel frames with 4, 8, 12, 16 stories are designed based on DDBD approach utilizing displacement spectrum of the Iranian Code of Practice for Seismic Resistant Design of Buildings (Standard No. 2800). In order to evaluate seismic response of the designed structures, a series of non-linear time-history analyses have been performed under different records compatible with Standard No. 2800. All the non-linear analyses were carried out using the fiber-element models developed in Seismostruct computer program. According to the results, inter-story drift profile of the structure which is corresponding to its damage was less than the allowable value in most cases. Also, Maximum displacement profile of the structure along its height is completely matched with the primary assumed design profile. The structures have mostly experienced similar residual drift values under different records. In summary, the method performed quite satisfactorily in terms of story maximum displacements, maximum interstory drifts and story ductility demands, even for tall models.

Influence of the Resin Layer Thickness at the Interface of Hybrid Metal-composite Co-cured Joints

As discussed in literature, the accurate analysis of the modern co-cured joints between composite materials or between a metal and a composite material (hybrid joints) is complicated by the influence of the interface resin layer on the interface singular stress field. In such joints, in fact, there is not a proper adhesive layer and the thickness of the resin layer, that plays the role of the adhesive, is not constant due to the presence of the reinforcing fibers in the composite adherent. For this reason several authors assume that a generic co-cured joint can not be studied as a simple bi-material joint, without considering the particular characteristics of the actual resin layer. This problem is also involved into the development of reliable design methods able to give accurate predictions of the joint efficiency. In this work, by theoretical analyses performed by using the Lekhnitskii theory, numerical simulations carried out by means of the boundary element method and experimental investigations based on the combined use of the generalized Dundurs parameters and digital photoelasticity, the influence of the resin layer on the singular stress field at the interface of a generic hybrid metal-composite joint, has been investigated.

Intermediate Crack Debonding of Polymer Cement Mortar Overlay-Strengthened RC Beam

The bond behavior at the polymer cement mortar (PCM)-concrete interface particularly affects the structural behavior of overlay-strengthened slabs or beams, and the debonding of the PCM overlay was one of the major failure modes. The design procedure of PCM overlay to strengthen an RC element should avoid these premature debonding failures. Because no reliable design method for retrofitting with the PCM overlay is currently available for the practitioner, a need exists to understand the mechanism of the PCM overlay debonding process to prevent failure. This paper presents an analytical approach for a PCM overlay-strengthened beam failed by intermediate crack (IC) debonding. The limit of transferred shear force along the PCM-concrete interface to avoid any occurrence of debonding is analytically provided. The reliability and accuracy of the proposed analytical procedure have been successfully verified by knowing the ratio of analytical and experimental strength of the PCM-strengthened beams compiled in a bending test database, which has a mean value of 1.10 and a standard deviation of 0.14.

Robust reliable tracking controller design against actuator faults for LPV systems

AbstractA robust reliable tracking controller design method is developed against actuator faults for linear parameter varying (LPV) systems under a passive control framework. This method is based on a newly proposed stability condition for LPV systems, which is a more general condition than the existing results. An important contribution of this method is that it could handle relatively wider range of actuator faults due to the extra freedom degree introduced by a new slack variable in the stability condition. Numerical example shows the effectiveness and superiority of our method.Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

Health-monitoring method of note PC for cooling performance degradation and load assessment

Health monitoring technologies, which can evaluate the performance degradation, load history and degree of fatigue, have the potential to improve the effective maintenance, the reliability design method and the availability in the improper use conditions of electronic equipment. In this paper, we propose a method to assess the cooling performance degradation and load history of printed circuit boards in electronic equipment by use of a hierarchical Bayes model based on Computer Aided Engineering (CAE) results of thermal–stress simulation and experiment data from observed measurements. We applied this method to note PC that can monitor the device load factor and revolution number of cooling fan. It is shown that this method can estimate the temperature and deformation distribution of the printed circuit board from monitoring variables through latent variables such as thermal dissipation of the device and thermal boundary condition by use of the hierarchical Bayes model. And it is confirmed that the statistical load assessment concerning thermal cyclic load and the maximum load distribution can be conducted using the estimated temperature and deformation data. Furthermore, we verified that the cooling performance degradation can be assessed, if the temperature difference per unit thermal value between two suitable points on the printed circuit board can be obtained. It is concluded that the proposed method can be effective to assess the thermal load history and cooling performance degradation.

Gear Reliability Design Using Probability Finite Element Method Based on Response Surface

The paper studies on the gear reliability design method using probability finite element method based on response surface and it indicates that the reliability sensibility calculation method of function in response surface can be used when limit state function is unknown. The limit state function established on response function is quadratic polynomial with simple form and it makes the calculation of variance and deviation very convenient, which realizes the simple and easy calculation of reliability sensitivity and largely increases calculation velocity and precision. The method can be applied for general purpose with certain standard, which is easy for programming and accomplishing gear reliability design in a rapid and precise way.

Complete Proceedings - Single PDF Download

The Conference on Coastal Engineering at Long Beach was conceived originally as a local meeting of engineers and scientists interested in shoreline problems and was sponsored by the University of California. It early became evident that there was widespread interest in the subject and that the program should be planned on a more ambitious scale. The aim was to aid engineers by summarizing the present state of the art and science related to the design and planning of coastal works rather than to present a series of original scientific contributions. Starting from a rather comprehensive outline, invitations were issued to recognized authorities to report on specific phases of the subject, and the authors cooperated splendidly both in their treatment of the subjects assigned and in their avoidance of overlapping other subjects. Although much remains to be done in the way of developing reliable design methods, the series of papers presented at the conference and published in this volume do represent a rather thorough summary of coastal engineering as now practiced.
 Engineers engaged in the design of coastal works have had available to them a large number of papers dealing with various phases of the science related to their problems, but proper dealing with design were limited in number and scope. Only a few books on coastal engineering have been published. The quality and scope of the papers and the need for a comprehensive and modern treatment of the subject convinced the sponsors of the conference that publication in a single volume was desirable rather than piecemeal in the scientific and technical journals. The newly-formed Council on Wave Research secured funds to underwrite the publication costs from its parent organization, the Engineering Foundation.
 A word about the term "Coastal Engineering" is perhaps in order here. It is not a new or separate branch of engineering and there is no implication intended that a new breed of engineer, and a new society, is in the making. Coastal Engineering is primarily a branch of Civil Engineering which leans heavily on the sciences of oceanography, meteorology, fluid mechanics, electronics, structural mechanics, and others. However, it is also true that the design of coastal works does involve many criteria which are foreign to other phases of civil engineering and the novices in this field should proceed with caution. Along the coastlines of the world, numerous engineering works in various stages of disintegration testify to the futility and wastefulness of disregarding the tremendous destructive forces of the sea. Far worse than the destruction of insubstantial coastal works has been the damage to adjacent shorelines caused by structures planned in ignorance of, and occasionally in disregard of, the shoreline processes operative in the area.
 The Council on Wave Research takes this opportunity to thank the authors of the papers and the many others who assisted in organization of the conference and in the preparation of this volume for publication.

Predictive tools for the estimation of downcomer velocity and vapor capacity factor in fractionators

Abstract Fractionation is one of the pivotal unit operations in refineries and gas processing industries which is single largest energy-degrading processing unit utilized to separate mixtures into individual products. A reliable design method for sizing tray fractionators must take into account of foaming which is a major consideration in many process systems. The aim of this study is to develop simple predictive tool, which is simpler to use than current available techniques avoiding large number of parameters requiring less complicated and shorter computations, for accurate determination of downcomer velocity and vapor capacity factor as a function of tray spacing and density. The results can be used in follow-up design calculations to size fractionators without foaming formation for tray spacing up to 1.2 m, vapor densities up to 100 kg/m 3 and liquid and vapor density differences up to 950 kg/m 3 . The accuracy of the proposed equations was tested and found to be in excellent agreement with the reported data for the wide range of conditions, wherein the average absolute deviation percent of proposed equations are 0.77% and 2.35% for downcomer design velocity and vapor capacity factor respectively. The proposed predictive tool detailed in the paper can be very helpful for design engineers to handle sizing calculations for tray fractionators.

Development of advanced pattern recognition model for evaluation of lateral displacement on soft ground using support vector machine

With the increase of the number of construction projects on soft ground due to the growth of regional industry, various construction problems related to soft soil behavior have also been reported. Especially, foundation piles of abutments and/or buildings which were constructed on soft ground have suffered from a great deal of stability problems due to excessive displacement accompanied by the lateral flow of soft ground. Although many researchers have studied this problem, it is still difficult to assess the mechanism of lateral flow quantitatively. Furthermore, a reliable design method for the judgment of lateral flow occurrence is not established yet. In this study, an advanced pattern recognition theory — i.e., the support vector machine (SVM) theory — was applied to develop a soft computing model for the judgment of lateral flow occurrence based on real data compiled from Korea and Japan. Predicted results from SVM models were compared with those from the conventional empirical methods. It has been found that the proposed SVM pattern recognition model can predict lateral flow occurrence practically and more accurately than the conventional empirical methods.

Robust reliable control for uncertain switched nonlinear systems with time delay under asynchronous switching

This paper investigates the problem of robust reliable control for a class of switched nonlinear systems with time delay and actuator failures under asynchronous switching. When the switching instants of the controller experience delays with respect to those of the system, a kind of reliable controller design method is proposed, and the dwell time approach is utilized for the stability analysis. Sufficient conditions for the existence of the reliable controller are formulated in terms of a set of LMIs. Then the proposed approach is extended to take into account switched delay systems with Lipschitz nonlinearities and structured uncertainties. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.

Comparison of AASHTO LRFD and ASD specifications for structural design of cantilever abutments and retaining walls

The American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specification became the mandatory design specifications for United States highway structures in October 2007. This has introduced a number of changes in mandatory engineering design and analysis procedures. The differences between the allowable stress design (ASD) standard specifications and the LRFD specification are evaluated in this paper, as well as how they apply to earth retaining structure design. The effect of the new design standards on structural proportioning and cost were examined through several design examples. The difference between the LRFD specifications and the ASD standard specifications was insignificant for cantilever abutments and retaining walls 4.6 m and taller. However, an increase in footing length of about 30% and an increase in cost of approximately 10% of the cost of the retaining structures can result from designing shorter abutments and retaining walls using the LRFD specifications. While in some designs, these cost impacts to a structure can be significant, the AASHTO LRFD specifications provides a safe and reliable design method of paramount importance to engineers and the public.

Methodology design for reliability power transmission systems of vehicles

With the worldwide competition being so strong, it is essential for motor vehicles to have high reliability. The methodology for motor vehicle reliability design, namely Power Transmission (PT) of vehicle, is one of the ways to reach this objective. The stage of design is the most important one in the life cycle of a motor vehicle. Reliability design, within the designing stage, correlates directly with the vehicle reliability. The problem of a practical vehicle design methodology has been solved by developing a methodology suited to the purpose. The basis of the developed methodology represents a contemporary approach to designing, comprising the phases of conceptual, preliminary and detail designs, with applying of the reliability design method within these phases.

Practical Determination Method for Soil Parameters Adopted in the New Performance Based Design Code for Port Facilities in Japan

The Japanese design code for port facilities was revised in April 2007, and a performance-based reliability design method was introduced. This report introduces a new practical method, which has been adopted in the annex of the design code, to evaluate soil parameters. The new method uses a correction factor corresponding to the coefficient of data variation. In this method, the characteristic value automatically reflects the variation of the derived values in association with the testing method and the reliability of the data interpretation. Compared to the lower limit of 95% confidence interval, which is widely adopted in general design codes such as Eurocode 7 and JGS4001, the characteristic value determined by this method is conservative when the number of data entries is larger than 10. This tendency is caused by the concept, in which characteristic values always reflect the data variation, even though the number of data entries are significantly large. Generally, data variation in the depth profile can be reduced when the depth distribution is appropriately modeled. Also, data variation can be reduced by adopting a more reliable soil test. Accordingly, any efforts to reduce the variation are awarded in this new design code.

DESIGN FOR RELIABILITY AND ROBUSTNESS: A CASE STUDY

Resistance welding is to bond two pieces of metal materials together by melting the materials in the contact area. An elevated temperature is generated by contact resistance when electrical current flows through the contact area of the two materials. Generally, a current is applied through two close electrodes. Sometimes, however, it is necessary to set the two electrodes far apart when the contact area is physically unreachable. The far separation of the electrodes makes difficult to generate reliable welds. This paper describes a reliability and robustness design method for the welding process. In particular, a concept design was conducted to avoid welding failure modes. The critical dimensions of a work piece were defined to make a successful weld. Then the welding processes for various dimensions of the work pieces were optimized using Taguchi's parameter design method. A thermal cycle test was performed to evaluate the reliability of the welds. It is shown that the welding process is robust and the welds have high reliability.

Improved utility and application of probabilistic methods for reliable mechanical design

In a modern product development process such as in the automotive and aerospace sectors, extensive analytical and simulation approaches often are used to assess the ability of a design in fulfilling its requirements. Consideration of uncertainty in such situations is critical in ensuring a reliable design is produced. Probabilistic methods facilitate an improved understanding of design performance through characterization of uncertainty in the design parameters. The probabilistic methods developed over the past several decades have a range of capabilities and modes of application, for example, to predict reliability, for optimization, and to perform sensitivity studies, but have yet to be taken up routinely by industry due to a number of reasons. In this paper, issues that have typically inhibited their use or prevented a successful outcome are addressed through a systematic framework for improved utility and successful application of probabilistic designing for mechanical reliability.

Flexible fabrication, packaging, and detection approach for microscale chromatography systems

This paper describes a simple manufacturing and packaging method to fabricate microfluidic channels and obtain an optical detection interface for rapid prototyping of microscale chemical and biological analysis systems. Specifically, this work reports on efforts to develop new methods for simple, fast and reliable design and fabrication of microscale field flow fractionation (FFF) based biological analysis systems and a compatible optical detector flow cell. First, a rapid prototyping technique is used to realize electrical FFF microchannels and second, a modular detector interface with a 38nl detection region is employed, which when connected to an appropriate microfluidic channel, results in a ElFFF prototype. Detector characterization is carried out to evaluate important figures of merit such as sensitivity, S/N ratio and limit of detection. Plate height, a primary performance metric for field flow fractionation is determined and compared with an on-chip detector. Separation of a multicomponent mixture of polystyrene particles is also demonstrated. The developed system allows for an easy plug-and-play approach to the optical interface and has resulted in improved operational flexibility and robustness of the microsystem.

Face stabilisation of shallow tunnels using fibreglass dowels

Stability of the excavation face in shallow tunnels and in poor ground is at present a relevant problem in tunnelling. Even though face reinforcement with fibreglass dowels has proved to be efficient, there is still no reliable routine design method available. A new calculation procedure is illustrated in this paper for the analysis of face reinforcement with fibreglass dowels in shallow tunnels. The procedure is based on the limit equilibrium method (LEM) applied to the ground core ahead of the face, and it is able to offer a detailed evaluation of the interaction between each reinforcement element and the surrounding ground. The main result of the calculation concerns the safety factor of the excavation face with dowel reinforcement. Based on this safety factor, it is possible to identify the appropriate length and number of dowels. The procedure has been applied to two real cases, and satisfactory results have been obtained.

Design Proposal to Avoid Peeling Failure in FRP-Strengthened Reinforced Concrete Beams

According to the available experimental work, the most common failure in existing structures strengthened by plate bonding is the laminate peeling off. In the last few years, an important effort in the development of mathematical models to avoid premature peeling failures has been made. However, a suitable and reliable design method to predict debonding due to the shear flow between crack discontinuities or at the laminate end is still not available. This paper describes a new design procedure for structures strengthened by plate bonding to avoid peeling failure at any location. After calculating the laminate area required for flexural strengthening, a two-step procedure to prevent peeling failure is proposed. The first step, to avoid peeling failure along the span, is based on a shear-bending interaction diagram associated with the theoretical maximum transferred force between laminate and support along the crack spacing before laminate debonding. This interaction diagram can be obtained through the appl...