Time-based approach to obtain quantitative measures for ergonomics hazard analysis

The paper describes a methodology for conducting an ergonomic analysis that allows ergonomists to gather data while off site. The analysis described is carried out on portable computing devices, using common computer applications. It includes data collection via a camera on the manufacturing floor and conversion into a digital format. Software is suggested for playback and semi-automatic work sampling of work cycles while recording observations to electronic form, to generate rapidly the analysis of results. Snapshot observations are made on frozen video frames that are categorized into work elements, upper body joint posture and static/dynamic effort. Using two case studies, it is shown how the approach may be implemented as a procedure of choice to complete a quantitative work analysis.     

Fire safety assessment and optimal design of passive fire protection for offshore structures

The article presents a unified probabilistic approach to fire safety assessment and optimal design of passive fire protection on offshore topside structures. The methodology was developed by integrating quantitative risk analysis (QRA) techniques with the modem methods of structural system reliability analysis (SRA) and reliability based design optimisation (RBDO). Reliability analysis methodologies are presented for both plated (e.g. fire and blast walls) and skeletal structures (deck framing), which take into account uncertainties in fire and blast loading, thermal and mechanical properties of the steel and insulation. Probability of component and system failure are evaluated using first- and second-order reliability methods (FORM/SORM). The optimisation of passive fire protection is performed such that the total expected cost of the protection system is minimised while satisfying reliability constraints.     

A practical engineering method for fuzzy reliability analysis of mechanical structures

The fuzzy sets theory in reliability analyses is studied. The structure stress is related to several other variables, such as structure sizes, material properties, external loads; in most cases, it is difficult to be expressed in a mathematical formula, and the related variables are not random variables, but fuzzy variables or other uncertain variables which have not only randomness but also fuzziness. In this paper, a novel approach is presented to use the finite element analysis as a “numerical experiment” tool, and to find directly, by fuzzy linear regression method, the statistical property of the structure stress. Based on the fuzzy stress–random strength interference model proposed in this paper, the fuzzy reliability of the mechanical structure can be evaluated. The compressor blade of a given turbocharger is then introduced as a realistic example to illustrate the approach.     

A practical approach to evidence grading

BACKGROUND: The Institute for Clinical Systems Improvement (ICSI) is a collaboration of 17 Minnesota medical groups. Among other activities, ICSI develops health care guidelines and technology assessment reports. To maintain focus on the underlying evidence, ICSI has developed an evidence and conclusion grading system for use by the practicing clinicians who write the documents and use them in making decisions about patient care. THE EVIDENCE GRADING SYSTEM IN DETAIL: The centerpiece of the evidence grading system is the conclusion grading worksheet, which calls for statement of a conclusion, summarization of research reports that support or dispute the conclusion, assignment of classes and quality markers to the research reports, and assignment of a grade to the conclusion. EXPERIENCE AND RESULTS: The system has been used in the writing of more than 40 guidelines and numerous technology assessment reports. An example of a worksheet from the congestive heart failure guideline is presented. The system has helped the drafting groups to attend to the evidence. The methods have proven to be well accepted by practicing physicians and to be practical, although staff expertise in epidemiology is needed to support the system. Grading of conclusions appears to be reliable, although this characteristic of the system has not been rigorously tested. The outputs are valued by users of the documents. DISCUSSION: Although some residual problems remain to be solved, the system appears to be successful in overcoming the complexity of some published systems for grading evidence while still yielding a defensible classification of conclusions based on the strength of the underlying evidence.     

A stop-hole method for marine and offshore structures

Stop holes have been widely used as temporary repair means in marine and offshore engineering to extend the service life of cracked structural components that cannot be immediately replaced. However, there is a lack of guidance with respect to the appropriate size of a stop hole that is usually determined based on the judgment of the attending surveyor/inspector. In the present paper, a method is proposed for determining the appropriate size of a stop hole for cracked marine and offshore structures. In addition to the traditional concerns over the size and nature of the crack, the proposed method incorporates high-cycle and low-cycle fatigue analyses into remain service life prediction taking into account both long-term and short term wave-induced loading. The effects of the return period of the potential severest sea condition, the crack length, and the environmental severity factor on the remaining service life of a stop hole are investigated.     

Fatigue fracture mechanics analysis of offshore structures

An assessment of a fatigue fracture mechanisms procedure for fatigue life estimation of welded joints in offshore structures resulting from studies of variable amplitude loading, stress analysis and crack growth measurement in T-joints is presented.     

火灾烟气危害性研究及其进展

建筑火灾中，烟气是导致人员伤亡的最主要因素之一。较系统地说明并总结了烟气研究的实验方法和理论研究成果，介绍了烟气危害性评价的方法与相关指标，为进一步开展火灾烟气实验研究方案设计提供了参考。根据国外相关工作的进展，对理论计算的对象和今后重点研究的目标提出了建议。     

A practical approach to the reformed IPC

In a global collaborative effort, the Version 8 International Patent Classification Codes (IPC-8) have been applied to patent documents published prior to 2006 (backfile). This unprecedented effort employed multiple techniques, including use of earlier IPC versions, use of ECLA codes, and propagation of codes from one document to another within Inpadoc patent families. The result is that most records bear a relatively high number of codes, and family members from different authorities are coded relatively uniformly, at least at present. It is also notable that patent documents are not easily differentiated based on selective use of inventive codes because the vast majority of codes have been designated as inventive even where they cover subject matter that would be likely to figure as additional information in a substantial number of cases. Creating high precision search strategies relying on codes may be helped by requiring 2 or more codes to be present on individual documents or families. Sample searches presented are exemplary, and search strategies must be tested individually for optimizing searching in each subject matter area. Whether the reclassification effects and the propensity to make most codes “inventive” makes the IPC more akin to an indexing system is a question only time will answer.     

A fast first-order optimization approach to elastoplastic analysis of skeletal structures

It is classical that, when the small deformation is assumed, the incremental analysis problem of an elastoplastic structure with a piecewise-linear yield condition and a linear strain hardening model can be formulated as a convex quadratic programming problem. Alternatively, this paper presents a different formulation, an unconstrained nonsmooth convex optimization problem, and proposes to solve it with an accelerated gradient-like method. Specifically, we adopt an accelerated proximal gradient method, that has been developed for a regularized least squares problem. Numerical experiments show that the presented algorithm is effective for large-scale elastoplastic analysis. Also, a simple warm-start strategy can speed up the algorithm when the path-dependent incremental analysis is carried out.     

Grounded rubble fields adjacent to offshore structures

A continuum model of grounded ice rubble fields is developed in which bulk rubble is treated as a Mohr-Coulomb material at critical equilibrium. The surrounding ice sheet is considered to form a rigid boundary. Approximate stress distributions are obtained using the method of integral relations. Loads on an offshore structure adjacent to a rubble field are related to maximum stresses exerted by the floating ice sheet. The influence of field geometry, grounding resistance, and rubble properties is examined.     

A numerical integration approach for fractional-order viscoelastic analysis of hereditary-aging structures

In this paper, a novel numerical integration scheme is proposed for fractional-order viscoelastic analysis of hereditary-aging structures. More precisely, the idea of aging is first introduced through a new phenomenological viscoelastic model characterized by variable-order fractional operators. Then, the presented fractional-order viscoelastic model is included in a variational formulation, conceived for any viscous kernel and discretized in time by employing a discontinuous Galerkin method. The accuracy of the resulting finite element (FE) scheme is analyzed through a model problem, whose exact solution is known; and the most significant variables affecting the solution quality, such as the number of Gaussian quadrature points and time subintervals, are then investigated in terms of error and computational cost. Moreover, the proposed FE integration scheme is applied to study the short- and long-term behavior of concrete structures, which, due to the severe aging exhibited during their service life, represents one of the most challenging time-dependent behavior to be investigated. Eventually, also the Euler implicit method, commonly used in commercial software, is compared.     

Nonlinear wave theory in reliability analysis of offshore structures

The reliability analysis of offshore structures under wave and wind actions is considered using second order random wave theory. To represent non-Gaussian properties of the resulting wave kinematics, the Hermite moment transformation is used. Further, the so-called sample-specific linearization method developed already (to be used in conjunction with the directional simulation method and the linear wave theory) will be extended to take into account both (1) non-Gaussianity of wave/wind load due to nonlinear load processes and also (2) the non-Gaussianity of wave kinematics due to the nonlinear wave theory. This allows an out-crossing approach to be used to assess the structural probability of failure and the involving out-crossing rate (which is not generally available for non-Gaussian processes) is required to be estimated. Using the proposed procedure, simple structures are analyzed in one- and multi-dimensional cases and the results for structural probability of failure are compared with those obtained using simple linear wave theory. Outcomes show that the use of nonlinear wave theory may affect the results considerably.     

二维自由振动的有限元线法自适应分析新进展

该文建立圆弧形曲梁裂纹的截面损伤缺陷比拟方案,实现裂纹大小(深度)、位置、数目的模拟。引入变截面Euler-Bernoulli梁的h型有限元网格自适应分析方法,求解含裂纹损伤圆弧曲梁弹性屈曲问题,得到优化的网格和满足预设误差限的高精度屈曲荷载和屈曲模态解答。数值算例表明该算法中网格非均匀加密可适应裂纹损伤引起的屈曲模态变化,应用于各类曲梁夹角和裂纹损伤分布工况下的弹性屈曲研究,定量分析了裂纹损伤程度对圆弧曲梁的屈曲荷载和屈曲模态的影响,检验了该文算法的精确性和可靠性。     

Flow-graph approach for optical analysis of planar structures

The flow-graph approach (FGA) is applied to optical analysis of isotropic stratified planar structures (ISPS's) at inclined light incidence. Conditions for the presence of coherent and noncoherent light interaction within ISPS's are determined. Examples of the use of FGA for calculation of the transmission and the reflection of two-layer ISPS's for different types of light interaction are given. The advantages of the use of FGA for optical analysis of ISPS's are discussed.     

Extreme response statistics for drag dominated offshore structures

The paper presents a study of extreme response statistics of drag dominated offshore structures, subjected to severe sea states. The nature of the hydrodynamic forces acting on the structure is highly nonlinear under such conditions. Additionally to drag forces, the so-called inundation effect must also be taken into account. In the present paper a stochastic force model is introduced that captures both these phenomena in a fairly simple manner allowing for efficient calculation of the extreme response statistics. In fact, the proposed model opens up the possibility to calculate efficiently even long-term extreme response statistics, which is an important issue for the design of offshore structures. Comparison with the results of Monte Carlo simulations for a jacket structure indicates that good accuracy can be obtained for the extreme response predictions.     

A practical testing approach to determine mode II fracture energy GIIF for concrete

Continuing the experiments on the double-edge notched specimens on which the mode II fracture toughness K _IIc of concrete was measured, a practical testing approach to determine mode II fracture energy G _IIF is studied using the same geometry.     

A proposal for performing software safety hazard analysis

Techniques for analyzing the safety and reliability of analog-based electronic protection systems that serve to mitigate hazards in process control systems have been developed over many years, and are reasonably understood. An example is the protection system in a nuclear power plant. The extension of these techniques to systems which include digital computers is not well developed, and there is little consensus among software engineering experts and safety experts on how to analyze such systems.One possible technique is to extend hazard analysis to include digital computer-based systems. Software is frequently overlooked during system hazard analyses, but this is unacceptable when the software is in control of a potentially hazardous operation. In such cases, hazard analysis should be extended to fully cover the software. A method for performing software hazard analysis is proposed in this paper. The method concentrates on finding hazards during the early stages of the software life cycle, using an extension of HAZOP.     

海洋细长结构参数激励不稳定区的确定方法

分别采用变形参数法,改进的变形参数法及傅立叶分析法确定海洋细长结构参数振动Hill方程的不稳定区,比较三种方法的优缺点,并给出了前三阶不稳定区图像,为张力腿、立管等海洋细长柔性结构的设计提供参考。     

Filter approach to the stochastic analysis of MDOF wind-excited structures

In this paper, an approach useful for stochastic analysis of the Gaussian and non-Gaussian behavior of the response of multi-degree-of-freedom (MDOF) wind-excited structures is presented. This approach is based on a particular model of the multivariate stochastic wind field based upon a particular diagonalization of the power spectral density (PSD) matrix of the fluctuating part of wind velocity. This diagonalization is performed in the space of eigenvectors and eigenvalues that are called here wind-eigenvalues and wind-eigenvectors, respectively. From the examination of these quantities it can be recognized that the wind-eigenvectors change slowly with frequency while the first wind-eigenvalue dominates all the others in the low-frequency range. It is shown that the wind field can be modeled in a satisfactory way by taking the first wind-eigenvector as constant and by retaining only the first eigenvalue in the calculations. The described model is then used for stochastic analysis in the time domain of MDOF wind-excited structures. This is accomplished by modeling each element of the diagonalized wind-PSD matrix as the velocity PSD function of a set of second-order digital filters with viscous damping driven by white noise of selected intensity. This approach makes it easy to obtain in closed form the statistical moments of every order of the structural response, taking full advantage of the Itô calculus. Moreover, in the proposed approach, it is possible to reduce the computational effort by appropriately selecting the number of wind modes retained in the calculation.