Maria Rashidi

A decision support methodology for remediation planning of concrete bridges

Bridges are critical and valuable components in any road and rail transportation network. Therefore bridge remediation has always been a top priority for asset managers and engineers, but identifying the nature of true defect deterioration and associated remediation treatments remains a complex task. Nowadays Decision Support Systems (DSS) are widely used to assist decision makers across an extensive spectrum of unstructured decision environments. The main objective of this research is to develop a requirements-driven methodology for bridge monitoring and maintenance which has the ability to assess the bridge condition and find the best remediation treatments using Simple Multi Attribute Rating Technique (SMART); with the aim of maintaining a bridge within acceptable limits of safety, serviceability and sustainability.

A methodology for bridge condition evaluation

Due to the substantial role of bridges in transportation networks and in accordance with the limited funding for bridge management, remediation strategies have to be prioritised. A conservative bridge assessment will result in unnecessary actions, such as costly bridge strengthening or repairs. On the other hand, any bridge maintenance negligence and delayed actions may lead to heavy future costs or degraded assets. The accuracy of decisions developed by any manager or bridge engineer relies on the accuracy of the bridge condition assessment which emanates from visual inspection. Many bridge rating systems are based on a very subjective procedure and are associated with uncertainty and personal bias. The developing condition rating method described herein is an important step in adding more holism and objectivity to the current approaches. Structural importance and material vulnerability are the two main factors that should be considered in the evaluation of element structural index and the causal factor as the representative of age, environment, road class and inspection is implemented as a coefficient to the OSCI (overall structural condition index). The AHP (analytical hierarchy process) has been applied to evaluate the priority vector of the causal parame

A new model for bridge management: Part A: condition assessment and priority ranking of bridges

Abstract Due to substantial role of bridges in transportation networks and in accordance with the limited funding for bridge management, remediation strategies have to be prioritised. A conservative bridge assessment will result in unnecessary actions, such as costly bridge strengthening or repairs. On the other hand, any bridge maintenance negligence and delayed actions may lead to heavy future costs or degraded assets. The accuracy of decisions developed by any manager or bridge engineer relies on the accuracy of the bridge condition assessment which emanates from visual inspection. Most of the bridge ranking systems are commonly based on structural condition. Parameters such as functionality and client preferences are used in an isolated fashion. The developing prioritisation method described herein is an important step in adding more holism and objectivity to the current approaches. To achieve this goal, all important parameters have been identified, weighted and finally synthesised in an index introduced as Priority Index (PI). PI is expressed as a number which enables the decision-makers to simply understand and compare the overall condition of a variety of bridges in the network. It embraces three factors: structural efficiency, functional efficiency and client impact factor. The proposed model was tested through case studies and qualified experts (senior bridge inspectors, engineers and asset managers) from about 30 private and public transportation authorities.

A new model for bridge management: Part B: decision support system for remediation planning

Abstract Bridges are fundamental elements in any road network and characterize a major capital asset of community resources. Because of their strategic location over obstacles, any failure may limit and restrict road traffic and cause inconvenience and economic loss. It is therefore important to manage bridge assets, to ensure that all the bridges are maintained in a safe condition, with the most cost-efficient use of resources. Most of the existing bridge management systems are to some extent subjective and based on cost optimization which does not address the indirect impact of the remedial actions. The subjective nature of decision-making in bridge remediation could be replaced by the application of a multi-criteria decision support system that supports decision-makers through balanced consideration of multiple criteria. The main goal of this paper is to present a requirements-driven decision support methodology for remediation of concrete bridges with the aim of maintaining bridge assets within acceptable limits of safety, serviceability and sustainability. The simplified analytical hierarchy process is used as a multi-criteria decision-making technique. A method for selection of the best remediation plan in terms of fund allocation for top-ranked bridges of the network is also proposed using the outputs of the previous procedures considering the budget as the main constraint.

A decision support system for concrete bridge maintenance

The maintenance of bridges as a key element in transportation infrastructure has become a major concern for asset managers and society due to increasing traffic volumes, deterioration of existing bridges and well-publicised bridge failures. A pivotal responsibility for asset managers in charge of bridge remediation is to identify the risks and assess the consequences of remediation programs to ensure that the decisions are transparent and lead to the lowest predicted losses in recognized constraint areas. The ranking of bridge remediation treatments can be quantitatively assessed using a weighted constraint approach to structure the otherwise ill-structured phases of problem definition, conceptualization and embodiment (1). This Decision Support System helps asset managers in making the best decision with regards to financial limitations and other dominant constraints imposed upon the problem at hand. The risk management framework in this paper deals with the development of a quantitative intelligent decision support system for bridge maintenance which has the ability to provide a source for consistent decisions through selecting appropriate remediation treatments based upon cost, service life, product durability/sustainability, client preferences, legal and environmental constraints. Model verification and validation through industry case studies is ongoing.

Decision making on the optimised choice of pneumatic formwork textile for foam-filled structural composite panels

The selection of an appropriate formwork system not only affects the entire construction duration and cost, but also affects subsequent construction activities such as electrical, mechanical, and finishing work. The current intuitive judgment approach in the selection of fabric formwork systems cannot assure an optimal and consistent result. This paper introduces a decision-making method for selection of the most appropriate pneumatic fabric formwork for foam-filled structural panels in rapidly assembled buildings (RABs) that will be used in semi-permanent housing such as post disaster sheltering. First, using a questionnaire survey, six most effective criteria for a suitable pneumatic fabric formwork; permeability, strength, relative cost, durability, sew-ability, and aesthetics are identified. Some experimental tests were conducted to determine the selection indicators for the criteria like durability and strength for each candidate. Then a value matrix for these factors has been defined and calculated, and the best pneumatic formwork candidate for foam-filled structural composite panels is selected from a list of seven potential candidates, using Analytical Hierarchy Process (AHP).

Seismic Performance and Ice-Induced Vibration Control of Offshore Platform Structures Based on the ISO-PFD-SMA Brace System

Pall-typed frictional damper (PFD) has higher capacity of energy dissipation, whereas shape memory alloy (SMA) has excellent superelastic performance. Therefore, combining PFD and SMA together as a brace system has a great prospect in vibration control of structures. This paper investigates the performance of offshore platform with three structural configurations including the SMA brace system, the ISO-SMA (where ISO stands for isolation) brace system, and the ISO-PFD-SMA brace system, which are subjected to seismic and ice-induced excitations. In this study, PFD-SMA brace system is installed on the isolation layer of jacket platform, which is under earthquake excitations and ice loading. Then, the reduction of vibration is evaluated by using ANSYS program. The results show that the PFD-SMA brace system is useful in reducing the seismic response and ice-induced response of offshore platform structures; meanwhile, it also demonstrates excellent energy dissipation and hysteretic behavior.

Optimum spanning for rectangular floor systems – part 2: an algorithm and practical applications

Abstract In practice, structural optimum geometric design consists of selecting the best combination of a finite number of structural elements and available parameters. It gives the optimum design procedure a combinatorial nature. In this paper, first a bi-objective combinatorial optimisation problem is formulated for the floor spanning design of multi-story buildings. The aim is to achieve an optimum spanning of rectangular reinforced concrete (RC) floor systems with the minimum cost and plan eccentricity. Two popular types of floor systems are studied: flat plates and beam-slab floor systems. Then a bi-objective Ant Colony Optimization approach, as a robust algorithm for discrete optimisation, is developed to solve the combinatorial optimisation arisen from the optimum geometric design of reinforced concrete floors. Numerical Examples are included to demonstrate the application of the methodology and robustness of the algorithm.

Life Cycle Assessments of Incineration Treatment for Sharp Medical Waste

Treatment of sharp medical waste (waste disposable syringes) produced in hospitals or health care facilities in an environmentally sound ways have raised concerns relating to public health and occupational safety. Life cycle assessment (LCA) is a decision-supporting tool in waste management practice; but relatively little research has been done on the evaluation of sharp medical waste treatment from a life cycle perspective. Our study assesses the environmental performances of medical waste incineration as a type of dominant technology for specific medical waste of average composition. Inventory models were used for waste incineration and residues landfill. Background data were derived from modelling performed in HSC Chemistry thermochemical package linked with GaBi environmental assessment tool. Two scenarios have been considered and compared: Waste disposable syringes partially replacing coke in Electric Arc Furnace (EAF) steelmaking (WSI) and conventional incineration with pure metallurgical coke without adding waste syringes (CI). The results of this study could support the medical waste hierarchy and indicate that from a life cycle perspective, replacing part of metallurgical coke with waste syringes in electric arc furnace steelmaking leads to fairly significant reduce in most of environmental impact categories.

Bridge Abutment Movement and Approach Settlement — A Case Study and Scenario Analysis

Movement of bridge abutment is a significant issue affecting the overall reliability and safety of the structure. However, despite considerable consequences, potential movement of abutment is usual...