Demos C. Angelides

Offshore wind turbine risk quantification/evaluation under extreme environmental conditions

A simulation-based framework is discussed in this paper for quantification/evaluation of risk and development of automated risk assessment tools, focusing on applications to offshore wind turbines under extreme environmental conditions. The framework is founded on a probabilistic characterization of the uncertainty in the models for the excitation, the turbine and its performance. Risk is then quantified as the expected value of some risk consequence measure over the probability distributions considered for the uncertain model parameters. Stochastic simulation is proposed for the risk assessment, corresponding to the evaluation of some associated probabilistic integral quantifying risk, as it allows for the adoption of comprehensive computational models for describing the dynamic turbine behavior. For improvement of the computational efficiency, a surrogate modeling approach is introduced based on moving least squares response surface approximations. The assessment is also extended to a probabilistic sensitivity analysis that identifies the importance of each of the uncertain model parameters, i.e. risk factors, towards the total risk as well as towards each of the failure modes contributing to this risk. The versatility and computational efficiency of the advocated approaches is finally exploited to support the development of standalone risk assessment applets for automated implementation of the probabilistic risk quantification/assessment.

A strategic approach for supporting the future of civil engineering education in Europe

A new strategic vision of the extensively debated European higher education is proposed with focus on civil engineering. Civil engineering education for the future is considered with relevance to potential world-wide trends and anticipated societal requirements and, therefore, required employee qualifications of the construction-related providers to society. These employee qualifications include proper knowledge, skills and attitudes of the civil engineer to be developed with the proper civil engineering educational system. The influence on this system of intrinsic characteristics of knowledge, extrinsic requirements, constraints and drivers, and the ‘Bologna process’, is highlighted. It is emphasized that future civil engineering education in Europe should be developed in a systematic way. The strategic approach presented addresses the societal requirements influenced by world-wide trends, the requirements of the customers of civil engineering education, and several pertinent constraints and drivers. It is believed that the proposed strategic framework could have an impact towards the direction of making changes in a systematic way, with the implication of congruence and better communication among all stakeholders of European civil engineering education.

A prototype system for the prediction of final cost in construction projects

Civil engineering projects include several uncertainties and risks, due to the special characteristics of construction industry. Time and cost are two parameters that could potentially lead to successful and conforming to regulations production of projects. It is imperative to estimate correctly the development and the final outcome of these parameters. Various tools have been applied in order to create more accurate estimations. In this paper, a prototype system will be presented, which aims at predicting the final cost, based on information available at the bidding stage. The methodology will be based on a combination of regression analysis and case-based reasoning in order to produce models for the prediction of final cost. These models will incorporate a process view and will depend on activity based costing methodology to estimate the process cost.

Fuzzy vs. Probabilistic Methods for Risk Assessment of Coastal Areas

Coastal zones are dynamically evolving systems comprising three components, i.e. the marine, the coastal, and the land subsystem. This is a typical division of a coastal zone and the only common feature that two different coastal zones may present. Concerning other features such as landscape morphology, ecological habitats, land uses, residential development and economic activities, etc., coastal zones present a multivariate environment with various characteristics. In general, there may be three different typologies of coastal zones based on morphological criteria. However, the number of coastal zones types is extremely increased when the specific conditions met in each one of these types are taking into consideration. Several types of human settlements and habitats along with various processes of human and natural origin render an environment with many interdependenciesand risks.

Material supply simulation for off shore pipelaying construction

The planning and execution of offshore construction projects such as pipelaying, traditionally rely to a great extent on the expertise of the offshore personnel. The state of practice that is facilitated by this expertise often leads to good solutions, but it has the following limitations: (1) the expertise resides with a few experienced people who are not always available; (2) communication between the contractor and the customer is based on opinions and past experiences, and not necessarily on objective information; (3) consideration and comparison of alternative solutions and their impact on cost and time is not straightforward; (4) estimation, planning and control under new conditions and different ones from the past are not always effective leading to either conservative or inadequate solutions. Simulation is used as a decision support, planning, control, and process improvement tool. The simulation model developed is applied to the loading of the barge at the coating yard, the transportation of the material to the pipelaying site, and the pipelaying activity performed by the pipelaying vessel. The model captures the expertise of the offshore personnel and addresses effectively the limitations listed above. An object oriented environment is used to develop the simulation model that is proven to be very effective for the particular project for which it was developed and easily adjustable to any new pipelaying project.

Analysis and design of offshore energy conversion devices under modeling uncertainties

A comprehensive, versatile framework is discussed for analysis and design of offshore energy (waves and/or wind) conversion devices in presence of modeling uncertainties. The framework is founded on a probabilistic characterization of the uncertainty in the models for the excitation, the system (wave energy conversion device) and its performance. Stochastic simulation is proposed for evaluating the associated probabilistic integral quantifying, in this setting, the stochastic performance. For improvement of the computational efficiency, a surrogate modeling approach is suggested, based on moving least squares response surface approximations. An innovative sensitivity analysis is also presented that aims to identify the importance of each of the uncertain model parameters in affecting the overall stochastic performance. The optimal robust design within this stochastic modeling setting is finally discussed. The versatility of the framework is demonstrated in an example involving the risk assessment for an offshore wind turbine under extreme environmental conditions.

A Risk-Based Decision Making Methodology for Planning and Operating Safe Infrastructure Systems Against Various Hazards

Decision-making for infrastructure systems is a difficult task to perform because of the complexity and the variety of the types of risks that may occur in the different phases of the life-cycle of an infrastructure system. To overcome these difficulties a new methodology for a risk-based decision making for planning and operating infrastructure systems is proposed. This methodology integrates: (i) the variability of impact upon risk occurrence, (ii) the available risk-response strategies, and (iii) the preference of the decision maker over these strategies with regard to the criticality of the various impacts upon risk occurrence. The proposed methodology considers four risk-response strategies, namely: (a) acceptance, (b) mitigation, (c) transfer, and (d) avoidance. Three approaches are applied, in order to determine the preference margins between these strategies: (i) compliance with regulations and specifications, (ii) determination based on data elaboration, and (iii) subjective judgment. Once, the expected value of the impact upon risk occurrence is estimated, the decision maker is capable to decide for the respective risk-response. An application example is presented as a proof-of-concept of the proposed methodology.

VALIDATION OF VISION TRACKING AT EGNATIA ODOS MOTORWAY

Tracking applications provide real time on-site information that can be used to detect travel path conflicts, calculate crew productivity and eliminate unnecessary processes at the site. This paper presents the validation of a novel vision based tracking methodology at the Egnatia Odos Motorway in Thessaloniki, Greece. Egnatia Odos is a motorway that connects Turkey with Italy through Greece. Its multiple open construction sites serves as an ideal multi-site test bed for validating construction site tracking methods. The vision based tracking methodology uses video cameras and computer algorithms to calculate the 3D position of project related entities (e.g. personnel, materials and equipment) in construction sites. The approach provides an unobtrusive, inexpensive way of effectively identifying and tracking the 3D location of entities. The process followed in this study starts by acquiring video data from multiple synchronous cameras at several large scale project sites of Egnatia Odos, such as tunnels, interchanges and bridges under construction. Subsequent steps include the evaluation of the collected data and finally, performing the 3D tracking operations on selected entities (heavy equipment and personnel). The accuracy and precision of the method’s results is evaluated by comparing it with the actual 3D position of the object, thus assessing the 3D tracking method’s effectiveness.