Condition Assessment Model Research Articles

Subway Station Diagnosis Index Condition Assessment Model

Condition assessment of subway stations is a major issue facing public transit authorities worldwide. The Societe de Transport de Montreal (STM) requires a rehabilitation budget of CAD 643.6 million (2006–2010) for its aged stations. The STM and most transit authorities lack planning strategies that reflect this increase due to deficiency of condition assessment models and scarcity of existing models. The research presented in this paper assists in developing a condition assessment model (subway station diagnosis index). The model identifies and evaluates the weights of different functional (structural/architectural, electrical, mechanical, and security/communication functions) condition criteria for subway stations using the analytical hierarchy process. It also utilizes both the Preference Ranking Organization METHod of Enrichment Evaluation and the Multiattribute Utility Theory to determine the station diagnosis index (SDI). Data are collected from experts through questionnaires and interviews. A case ...

Condition Assessment of Water Treatment Plant Components

Potable water treatment is one of the most challenging and complex systems that municipalities need to deal with considering limited resources. A study from mid-90s showed that the continuously deteriorating Canadian water supply system would require $3.1 billion to bring the system at satisfactory level. Drinking water treatment plants (WTP) include several components, such as tanks, basin, and pumps. Operators are able to spend a small portion of the available resources or their plant’s infrastructure and equipment compared to water quality and day-to-day operational activities. The research presented in this technical paper aims at developing condition assessment model(s) for the WTP components. Essential condition parameters of WTP include technical, physical, environmental, and operational aspects. To determine the condition index of a WTP component, value additive multi-attribute theory has been used where average weights and scores are considered for the model parameters. Data on WTP conditions are collected from experts and consultants across Canada and the United States. It is concluded from the model results that the average condition index for settling basins, ranges from 9.6 (best scenarios) to 1.9 (worst scenarios) and from 9.6 to 3.4 for pumps. Analysis reveals that, for tank and basins, design and construction parameter is the most important parameter for WTP condition, while the operational parameter is the most important one for pumps. The developed models are expected to benefit academics and practitioners (municipal engineers, consultants, and contractors) to prioritize inspection and rehabilitation planning for existing water treatment plants.

Fuzzy knowledge-based model for soil condition assessment in Argentinean cropping systems

A knowledge-based system (KBS) for assessing soil condition in agroecosystems is presented. The KBS was built through expert opinion elicitation and available scientific data using fuzzy logic. The system is structured into three main elements: (1) input variables that represent the physical domain of soil condition assessment and are related to environmental and crop management conditions; (2) primary modules that describe the fuzzy nature of the soil indicators and; (3) secondary modules that represent the elicited knowledge on soil condition assessment from an expert panel. The application of the KBS on data on crop fields from Inland Pampa (Argentina) indicated that soil nitrogen depletion poses a hazard for soil health as no crop was able to accomplish more than 50% of the sustainability criteria elicited for soil nitrogen extraction from the system. Conversely, soil carbon and physical conditions exhibited values closer to the desirable scenarios elicited by the fuzzy if-then rules, with values of 0.84, 0.71 and 0.74 for maize, soybean and wheat, respectively, where higher indicator values reflect better soil condition assessment. No significant differences were observed in the overall soil degradation module between crops, with values of 0.64 for maize and wheat and 0.67 for soybean. The KBS developed in this work provided an alternative modeling tool for assessing agroecosystem condition when knowledge regarding long-term assessment is imprecise and uncertain.

Infrastructure Condition Prediction Models for Sustainable Sewer Pipelines

The Federation of Canadian Municipalities reported that approximately 55% of sewer infrastructure in Canada did not meet current standards. Therefore, the burden on Canadian municipalities to maintain and prioritize sewers is increasing. One of the major challenges is to develop a framework to standardize the condition assessment procedures for sewer pipelines. Lack of detailed knowledge on the condition of sewer networks escalates vulnerability to catastrophic failures. This research presents a proactive methodology of assessing the existing condition of sewers by considering various physical, environmental, and operational influence factors. Based on historic data collected from two municipalities in Canada, structural and operational condition assessment models for sewers are developed using the multiple regression technique. The developed regression models show 82 to 86% accuracy when they are applied to the validation data set. These models are utilized to generate deterioration curves for concrete, asbestos cement, and polyvinyl chloride sewers in relation to traffic loads, bedding materials, and other pipe characteristics. The developed models are expected to assist municipal engineers in identifying critical sewers, prioritizing sewer inspections, and rehabilitation requirements.

Finite element model updating of existing steel bridge based on structural health monitoring

Based on the physical meaning of sensitivity, a new finite element(FE) model updating method was proposed. In this method, a three-dimensional FE model of the Nanjing Yangtze River Bridge(NYRB) with ANSYS program was established and updated by modifying some design parameters. To further validate the updated FE model, the analytical stress-time histories responses of main members induced by a moving train were compared with the measured ones. The results show that the relative error of maximum stress is 2.49% and the minimum relative coefficient of analytical stress—time histories responses is 0.793. The updated model has a good agreement between the calculated data and the tested data, and provides a current baseline FE model for long-term health monitoring and condition assessment of the NYRB. At the same time, the model is validated by stress—time histories responses to be feasible and practical for railway steel bridge model updating.

Characterisation of lead pipes used in the water industry: extrusion processing, alloy microstructure and their role in service failures

The issue of leakage within the water distribution system is one of importance not only at an economic level for the industry, but also as a result of an environmental agenda addressing issues of water sustainability. The present work is concerned with leakage from lead based assets, in particular distribution pipes. Very little is known about the failure mechanisms within lead based assets. The present paper presents the findings from a study in which lead samples from intact and failed pipes, sourced from the Thames Water area, have been examined. The failure mechanisms have been identified at the macroscopic level and the pipe microstructure has been characterised – aspects of the microstructure control particular properties of the pipe (e.g. strength, creep and fatigue behaviour) and so may contribute to the potential failure modes. The present study is the first stage in a programme of work designed to develop a better understanding of the failure modes in lead assets, leading to the formulation of a more effective condition assessment model.

Condition assessment of long span cable-stayed bridge

A condition assessment model for cable-stayed bridge was proposed, and a cable tension, elevation and frequency condition assessment model was then applied. With the optimized cable tensions as criterion, upper and lower bounds were then introduced. With the elevation of bridge completion as benchmark, and with the allowable vertical displacement of control points to interpolate to generate the upper and lower bounds of elevation, algorithm of condition assessment was programmed. Using moderate index model to interpolate linearly, and with the application of variable weight synthesizing principle (VWSP) and correlation of slope coefficient, according to a set of inspection and monitoring data, performance condition of cable tension, elevation and frequency were calculated. Results showed that with the decrease of balanced coefficient α, the assessment result is a process of degradation. The more divergent the variable weight is, the more severe is the degradation of the bridge component, and the larger is the curvature of curve α-V. Eventually, the model predicted that, for those bridge components whose grade of single survey point is exactly the same, the curvature of curve α-V is constant zero, i.e. there is no correlation between the assessment result and the balanced coefficient α. Numerical simulation showed that it agrees quite well with the expectation.

Development of a condition assessment model for transmission line in-service wood crossarms

Wood transmission structures, such as H frames, have been extensively used to support electrical transmission lines throughout Canada. The transmission infrastructure is in general aging, and fungal decay of wood crossarms poses a significant risk of failure under adverse weather conditions. A crossarm failure in the transmission system can result in forced outages and customer disruptions that lead to significant economic losses. This paper presents a condition assessment model to prioritize the replacement of transmission crossarms that are near the end of their service life. The proposed standard involves a visual condition rating system, which is validated by results of full-scale testing of a sample of in-service crossarms. Aerial inspection of transmission lines using the proposed visual rating system is a simple, economical, fast, and effective method of assessment. The proposed approach would ensure a more consistent compliance with the condition-based replacement standard specified in the Canadian (Canadian Standards Association Standard CSA 22.3 No. 1-01) and North American (US National Electric Safety Code 2002 edition) standards.Key words: transmission structure, wood crossarms, decay, condition assessment, full-scale testing, visual rating system, statistical data analysis, bending strength.

Bridge Structural Condition Assessment Using Systematically Validated Finite-Element Model

The structural condition assessment of highway bridges is largely based on visual observations described by subjective indices, and it is necessary to develop a methodology for an accurate and reliable condition assessment of aging and damaged structures. This paper presents a method using a systematically validated finite-element model for the quantitative condition assessment of a damaged reinforced concrete bridge deck structure, including damage location and extent, residual stiffness evaluation, and load-carrying capacity assessment. In a trial of the method in a cracked bridge beam, the residual stiffness distribution was determined by model updating, thereby locating the damage in the structure. Furthermore, the damage extent was identified through a defined damage index and the residual load-carrying capacity was estimated.

Revegetation on a Coal Fine Ash Disposal Site in South Africa

AbstractEight medium amendments were conducted on top of a fine ash coal dump (i) to evaluate a few cost‐effective treatments that could determine the minimum fertility status required for the local ash to support the establishment of a viable vegetation cover, and (ii) to select suitable grass species that would establish on the ash and could serve as a foundation for long‐term rehabilitation. Degree and success of grass establishment per medium amelioration treatment is expressed in terms of total biomass, percentage basal cover, and in terms of a condition assessment model. Both the chemical and physical nature of the ash medium before and after amendment was characterized, as were the concentrations of some essential and potentially toxic elements in leaf samples. In terms of medium amelioration 5000 kg ha−1 compost, or 500 kg ha−1 kraal manure or 480 kg 2:3:2 ha−1 proved to be most effective. The grass species that occurred with the highest frequency, irrespective of treatment, were the perennials bermudagrass [Cynodon dactylon (L.) Pers. var. dactylon], weeping lovegrass [Eragrostis curvula (Schrader) Nees], and the annual teff [Eragrostis tef (Zuccagni) Trotter]. Of the potentially toxic extractable metals monitored in the leaves of vegetation on the dump, only Se accumulated to an average level of 4.4 mg kg−1 that could be toxic to livestock.

Practice-Oriented Approach to Developing a Data Requirements Model for Bridge Condition Assessment

Data collection activities in the bridge management process have not been designed. Rather, they have evolved over time, creating inconsistencies within and between agencies in data collection methods, data items collected, data quality, and data uses. The development of a data requirements model for bridge condition assessment, based on an investigation of the state of the practice and the desired state, is described. Using data flow diagrams and influence diagrams as structuring tools, a process has been developed that an agency can use to assess and improve its data collection practices.

Construction and evaluation of condition assessment and grazing capacity models for use in grazing management in the Eastern Mixed Bushveld of southern Africa

The Integrated System for Plant Dynamics (ISPD) is a comprehensive system in which new and existing data and knowledge are quantitatively or qualitatively used as a basis for range condition and grazing capacity assessments and for denning appropriate management options to maintain or improve the condition and capability of the range. This study was carried out to investigate the degree to which the qualitative approach in ISPD can be implemented, and to determine the amount and availability of data and expert knowledge in a specific area for the purpose of constructing a database in ISPD. Large quantities of information were available for the construction of vegetation condition and grazing capacity models for direct implementation in the grazing industry. The results generated by the models corresponded to the proposed grazing capacity values for the study area. The models furthermore enable any user to assess rapidly and accurately the range condition and grazing capacity for any vegetation unit in any stage of degradation.

Bridge condition assessment using fuzzy weighted averages

Abstract This paper describes a bridge condition assessment model that is based upon the simplification of a computational technique called resolution identity of fuzzy sets. The proposed model utilizes a fuzzy weighted average to combine fuzzy bridge condition ratings. The procedure is based on the decomposition of fuzzy sets into non-fuzzy level-sets or intervals. The utility and effectiveness of this procedure are illustrated with an example of the bridge condition assessment problem.