Risk Analysis and Reliability Assessment of Overhead Cranes Using Fault Tree Analysis Integrated with Markov Chain and Fuzzy Bayesian Networks

Establishing an adequate level of reliability in the overhead crane operations is an important and vital principle to avoid undesirable consequences. To do this, it is appropriate to have a comprehensive approach for risk and reliability assessment of the most probable failure scenarios during overhead crane operations. In this study, fault tree analysis (FTA) in combination with fuzzy set theory, Bayesian network (BN), and Markov chain was used to evaluate the probability of top event and reliability of overhead cranes. A total of 47 basic events were identified for ladle fall in overhead cranes. The results showed that the probability of the ladle fall in the FT approach is equal to 0.0523035 and in the BN approach in the prior event is equal to 0.0273394 which is less than the FT method. Based on the values predicted by Markov chain, the reliability of the system decreases over time by 67.9% after 60 months. This study showed that the plan for ladle fall prevention should consider all influencing parameters identified by proper risk assessment methodologies.

Seismic assessment of reinforced concrete columns with short lap splices

Existing reinforced concrete (RC) columns with short splices in older-type frame structures are prone to either a shear or bond mechanism. Experimental results have shown that the force–displacement response of columns exhibiting these failure modes are different from flexure-critical columns and typically have lower deformation capacity. This article presents a failure mode-based approach for seismic assessment of RC columns with short splices. In this approach, first, the probable failure mode of the component is evaluated. Subsequently, based on the failure mode, the force–displacement response of the component can be predicted. In this article, recommendations are proposed for evaluating the probable failure mode, elastic rotation, drift at lateral failure, and drift at axial failure for columns with short splices experiencing shear, flexure, or bond failures.

Analysis of the factors affecting probable failure of local entrepreneurs

Purpose This study aims to investigate and analyze the factors affecting the probable failure of rural entrepreneurs so that the most important factors responsible for failure in the business of small and local entrepreneurs are identified. Design/methodology/approach The present survey was conducted through the descriptive-analytical method by using a researcher-made questionnaire. The statistical population of the study included 1,641 greenhouse owner entrepreneurs in five rural communities. To clarify the key criteria affecting probable failure of greenhouse businesses, LISREL 8.8 computer software was used and the effects of selected indices on the process of probable failure of entrepreneurs were assessed using stepwise regression in the SPSS computer application environment. Findings According to the results, individual and managerial skills factors, deterrent financial and legal issues, social barriers and infrastructural issues investigated in this study were of the first to the fourth priorities in clarifying factors affecting probable failure of greenhouse businesses. Considering the intragroup relations in these factors, it could be said that individual and managerial skills factors and infrastructural issues had the highest correlation coefficient which could be attributed to individual and management weaknesses of entrepreneurs in understanding infrastructural issues as the most important parameters to be considered in starting businesses. Originality/value So far, few studies analyzed the failure of rural entrepreneurs and evaluated the probable factors affecting it. Thus, the present study is among the earliest instances in the field and its results could be of great benefit to domestic entrepreneurs and similar cases in other countries.

Landslide Susceptibility Modelling for Agricultural activities in Hilly Areas

The slope failure risk assessment of a particular area can be prepared by considering the data available. Many attempts have been made to classify the risk where evaluations are made in rating or in grading the slopes based on their characteristics and erosion problems. The assessments were done for geo-hazard such as erosion and landslide recognized in planning and guidance. Most of the hazard risk analyses require detailed knowledge of the geo- environmental predisposition factors and initial events that led to failure. The results of these analyses consist of identification and mapping of all erosion induced landslide phenomenon and are often translated in the form of maps, which is the fundamental step of the hazard assessment. The ranking of susceptibility areas and the delineation of probable failure areas are among essential features relevant to the production of these maps. In this study, Landslide Susceptibility Modelling was developed by taking into consideration all the landslide susceptibility factors in Cameron Highlands. The landslide susceptibility map was produced based on the historical records of a landslide in that area for 20 years and the frequency ratio model was developed using mapoverlaying techniques. The susceptibility map offers substantial benefits as a regional-scale tool over earlier susceptibility maps and Cameron Highland landslide- susceptible terrain zoning. The susceptibility map has the advantage of assisting with the implementation of suitable efforts to prevent landslides.

Improved Nonprobabilistic Global Optimal Solution Method and Its Application in Bridge Reliability Assessment

Utilizing the improved one-dimensional optimization algorithm conveniently solved the nonprobabilistic reliability index, however, only searching the part of probable failure points. Utilizing the global optimal solution method produced heavy computation, although it was capable of searching all probable failure points. This paper, based on these two methods, proposed an improved nonprobabilistic global optimal solution method. The presented method possessed the advantages of searching all probable failure points and generating less computation, by means of which the values of interval variables were determined based on the monotonicity of performance function to the corresponding variables. Without losing any probable failure points, this method was contributive to reducing root value point equations, lowering the computational complexity, and improving the computational efficiency. The effectiveness and feasibility of the presented method were verified by two examples. The proposed method was also introduced to build the nonprobabilistic reliability evaluation process of existing bridges. Taking the Longganhu bridge for example, the nonprobabilistic reliability index of it was calculated using the presented nonprobabilistic reliability evaluation process. The computed nonprobabilistic reliability index η = 0.737 < 1 indicated that the Longganhu bridge was unreliable and needed to be reinforced. Reinforcement measures were carried out for a hollow slab and bridge deck of the Longganhu bridge, respectively. The reinforced bridge was reevaluated as η = 2.159 > 1. The results showed that the bridge was reliable after reinforcement. The study illustrated the application and feasibility of the improved nonprobabilistic global optimal solution method and nonprobabilistic reliability evaluation process in reliability assessment and reinforcement of existing bridges.

Characterization of the geological and geotechnical conditions at the village of Monsanto

The stability of slopes and hillsides involving rock or soil masses depends crucially on the occurring geological and geotechnical conditions. The village of Monsanto, municipality of Idanha-a-Nova, is located on a granitic inselberg. The tourist interest of the village lies largely in the fusion of the granitic rock mass with the man-made constructions and in the aesthetics of several granitic boulders scattered throughout the village. In the present work the geological and geotechnical characterization of the rock mass has been carried out, namely by the field survey of the entire intervention area and by a set of laboratory tests on samples collected in the field (ultrasound propagation velocity and the uniaxial compression test). Based on this information, the shear strength of the discontinuities was estimated and a kinematic analysis was performed using the Dips 7.0 commercial software, with the objective of defining the predominant sets of joints and identifying the most probable failure mechanisms in each hillside.

Proposal of Failure Mode Map Under Dynamic Loading—Ratcheting and Collapse

Ratcheting, collapse, and fatigue are the probable failure modes which can occur under alternate dynamic loading like seismic loading. The objective of this study is to propose a failure mode map for rectangular beams by determining the conditions of occurrence of the ratcheting and collapse failure modes. The paper considers the analogy between thermal ratcheting and dynamic ratcheting. The nonlinear dynamic finite element method was used to analyze a rectangular beam model for different loading conditions. The results were plotted on a nondimensional primary and secondary stress parameter graph similar to the Bree diagram for thermal ratcheting. The similarity between thermal load and dynamic load was observed. The main difference between thermal and dynamic loading is the effect of the frequency of dynamic loading on the occurrence of ratcheting and collapse. Experimental observations of ratcheting have been obtained and are used for comparison to validate the analytical predictions. From the above results, a failure mode map has been proposed which can evaluate the occurrence conditions of ratcheting and collapse under dynamic loadings.