Engineering Judgment Research Articles

Comparing Optimization Techniques with an Engineering Judgment Approach to WDN Design

AbstractThe design of water distribution networks (WDNs) is a complex nonlinear problem that has been solved using optimization techniques attempting to find near-globally optimal solutions. This paper demonstrates that relying on engineering judgment, with very limited use of optimization, can generate reasonable quality approximations of the Pareto front of multiobjective WDN design problems without intensive computational requirements. First the results of the implementation of a previous implementation of the engineering judgment approach to the Battle of Background Leakage Assessment for Water Networks (BBLAWN) design competition is summarized. Additionally, a simplified version of the BBLAWN problem is solved using both the engineering judgment approach and a multiobjective optimization algorithm and the corresponding Pareto fronts are compared. Relative to other BBLAWN solutions, the engineering judgment solution produced a high-quality result with a very small computational budget and was able to ...

Discussion of assumptions behind rule-based ice loads due to crushing

Forecasts and trends indicate an increase in marine operations in polar waters. The design of new ships for severe polar conditions is usually solved via theoretical considerations that are combined with previous experience and engineering judgment. A deeper understanding of the theoretical considerations that underlie rule-based formulations is required for designing safe and efficient structures. This paper focuses on the assumptions that are hidden in the ice load formulations of the International Association of Classification Societies (IACS) Unified Requirements for Polar Ships (IACS, 2011) and of the Russian Maritime Register of Shipping (RMRS) Rules for the Classification and Construction of Sea-going Ships (RMRS, 2014), particularly the Daley ice load model and the Kurdyumov and Kheisin hydrodynamic model for ice crushing. A qualitative comparison of the two models is presented. The assumptions that underlie rule-based ice loads in the bow area are placed in the context of current understanding of ice–structure interaction process. The comparison of the models demonstrates that the underlying assumptions regarding the pressure–area relationship, ice edge spalling characteristics, dynamic viscosity and strength of the crushed ice are the most important assumptions, although they are highly contentious.

Combining Engineering Judgment and an Optimization Model to Increase Hydraulic and Energy Efficiency in Water Distribution Networks

AbstractThis paper presents a methodology for optimizing the operations of water distribution networks. The methodology combines the use of best management practices with a pseudogenetic algorithm, and has been applied to solve the problem of the battle of background leakage assessment for water networks. This problem involves more than 70,000 decision variables. To reduce this number, the problem was divided into three steps. First, a preliminary analysis was performed to define criteria for the replacement of pipes and pumps with a definition of potential subareas. Then, an optimization model was used to determine the pump schedule and pipe replacement. Finally, fine adjustments were performed including pump replacement, control pressure valve usage, and valve-setting definition. The main conclusion derived from this work is that a proper combination of optimization techniques and manual adjustments based on the use of engineering judgment is suitable to solve generic problems in water supply networks.

Conservation compendium. Part 11: A career in ruins (challenges presented by derelict structures)

Our built heritage is a finite resource stretching back thousands of years. Protecting and conserving this heritage is a challenge requiring knowledge, skills and experience, together with an ability to bring practical engineering judgement and often creative and imaginative solutions. This paper sets out the challenges faced by engineers and some of the approaches taken in the appraisal and protection of ruins.

Aggregation of group fuzzy risk information in the railway risk decision making process

Railway risk assessment is a hierarchical process where risk information obtained at lower levels may be used for risk assessment at higher levels. Fuzzy analytical hierarchy process (FAHP) is widely used in risk decision making process to solve imprecise hierarchical problems where the risk data are incomplete or there is a high level of uncertainty involved in the risk data, particularly, in the process of railway safety and risk decision making. However, the application of FAHP in risk decision making the risk analysts often face the circumstances where a large number of pairwise comparison matrices have to be established by expert knowledge and engineering judgements. There may be a lack of confidence that all comparisons associated with a railway system are completely justified in a rigorous way. This is particularly true when a complex railway system needs to be analysed or when subjective judgements should be involved. This paper presents a modified FAHP approach that employs fuzzy multiplicative consistency method for the establishment of pairwise comparison matrices in risk decision making analysis. The use of the proposed method yields a higher level of confidence that all of comparisons associated with the system are justified. In the meanwhile, the workload in determining the consistency of the judgements can be reduced significantly. A case example is used to demonstrate the proposed methodology. The results indicate that by using the proposed method, risks associated with a railway system can be assessed effectively and efficiently, and more reliable and accurate results can be obtained.

Redesigning Water Distribution Networks Using a Guided Evolutionary Approach

AbstractThe paper describes and discusses the application of a guided evolutionary approach for the optimization of water distribution networks. Initially developed for the Battle of the Water Networks II (BWN-II), the approach was adapted and improved for competing in the Battle of Background Leakage Assessment for Water Networks (BBLAWN). The proposed evolutionary approach operates in an exclusively discrete solution space and is intended to require as little engineering judgment and time as possible while attaining acceptable and informative results that are useful for decision making. Its main features are custom crossover and mutation operators specific for water distribution network optimization tasks. A simple postprocessing greedy algorithm to locally refine pipe replacements is introduced as a means of complementing the evolutionary approach.

Close range photogrammetry for dynamically tracking drifted snow deposition

Snow drifting along with snow blowing is a major concern for transportation efficiency and driving safety in regions where it develops. Common means to mitigate snow drifting on roadways are snow fences. Designing snow fences requires sound engineering judgment and a thorough evaluation of the potential for snow blowing and drifting at the construction site. The evaluation includes site-specific design parameters typically obtained with semi-empirical relations characterizing local transport conditions. Among the critical parameters involved in fence design and assessment of their post-construction efficiency is the quantification of snow accumulation at the fence site. Conventional methods for quantification of snow accumulation are tedious, expensive, and, given the harsh winter weather environment, risky at times. The present paper proposes an innovative assemblage of a close range photogrammetry (CRP) system to enable non-intrusive remote estimation of the snow deposit volume using real-time, automated data acquisition protocols. The study illustrates practical means for CRP implementation for snow mapping and tracking by highlighting the benefits and limitations of the method, comparing it with alternative measurement approaches, and pointing to circumstances where the technique is valuable for design and monitoring.

Expeditious seismic assessment of existing moment resisting frame reinforced concrete buildings: Proposal of a calculation method

Recent earthquakes that have struck Italian territory have emphasized the necessity to assess the seismic safety of the existing built heritage, comprising, for a substantial part, Reinforced Concrete (RC) buildings designed between the 50s and 80s. Those buildings were designed in accordance with regulations that, although showing a growing seismic awareness, were certainly inadequate to design buildings capable to withstand the design earthquakes prescribed by the more recent Italian Technical Standards for Constructions (NTC 2008). At the same time, the recent proposal made by the technical community to equip each existing building with a seismic suitability certificate encourages the development of a rapid method for seismic safety assessment. This paper presents a method to carry out a simplified and fast non-linear static seismic assessment of an existing RC building. This method is based on: (a) the selection of the RC elements that, based on engineering judgment, are expected to be the most vulnerable ones, and on (b) the subsequent evaluation of the structure displacement capacity corresponding to their failure. Simple and conservative plane structural models are proposed to carry out such evaluations. With the aim to appraise its potentialities, the proposed procedure is also applied to some RC buildings whose experimental and numerical results were published in the latest scientific literature. Strengths, weaknesses and possible further developments are highlighted.

Quantification of prior knowledge in geotechnical site characterization

Geotechnical characterization of a project site often starts with desk-study and site reconnaissance, which provide site information available prior to the project (e.g., existing data in literature, engineering experience, and engineers' expertise). Such information can be used as “prior knowledge” under a Bayesian framework and be quantitatively reflected by a prior distribution in Bayesian methods. However, it is not a trivial task for engineering practitioners to properly quantify prior knowledge as a prior distribution. This paper develops two different methods to quantify prior knowledge during geotechnical characterization of a project site. Where there is no prevailing prior knowledge on the site, a non-informative prior distribution (e.g., uniform prior distribution) is used to reflect quantitatively the engineering common sense and judgment. As prior knowledge improves and becomes much more informative, a subjective probability assessment framework (SPAF) is proposed to estimate the prior distribution from prior knowledge. The proposed SPAF framework assists geotechnical engineers in formulating and expressing their engineering judgments in a quantifiable and transparent manner. These two different methods are illustrated using information from a sand site of the US National Geotechnical Experimentation Sites (NGES) at Texas A&M University (TAMU).

Response modification factor of elevated water tanks with reinforced concrete pedestal

A probabilistic method based on FEMA P695 is employed for validating the response modification factor of reinforced concrete pedestals in elevated water tanks. In the current codes and standards, the response modification factor of elevated water tanks is mainly based on engineering judgement. Ten models of elevated water tanks with different tank sizes and pedestal heights are selected for the investigation. Initially, the prototypes are designed based on the current codes and standards. Next, the finite element models of the prototypes are developed. By performing incremental dynamic analysis, the probability of collapse for each prototype is calculated under different seismic loading conditions and system uncertainties. The results of the study validate and confirm the current response modification factor values and show that the tank size has a significant effect on the nonlinear seismic response behaviour of elevated water tanks. In addition, it is revealed that heavy tank sizes that are designed in accordance with codes and guidelines are more vulnerable under seismic loading compared with light and medium tank sizes.

Seismic fragility of reinforced concrete girder bridges using Bayesian belief network

SummaryInfrastructure owners and operators, or governmental agencies, need rapid screening tools to prioritize detailed risk assessment and retrofit resources allocation. This paper provides one such tool, for use by highway administrations, based on Bayesian belief network (BBN) and aimed at replacing so‐called generic or typological seismic fragility functions for reinforced concrete girder bridges. Resources for detailed assessments should be allocated to bridges with highest consequence of damage, for which site hazard, bridge fragility, and traffic data are needed. The proposed BBN based model is used to quantify seismic fragility of bridges based on data that can be obtained by visual inspection and engineering drawings. Results show that the predicted fragilities are of sufficient accuracy for establishing relative ranking and prioritizing. While the actual data and seismic hazard employed to train the network (establishing conditional probability tables) refer to the Italian bridge stock, the network structure and engineering judgment can easily be adopted for bridges in different geographical locations. Copyright © 2015 John Wiley & Sons, Ltd.

Incorporation of Velocity Pulses in Design Ground Motions for Response History Analysis Using a Probabilistic Framework

Ground motions that contain velocity pulses may cause greater structural damage than ground motions that do not contain pulses. The effects of pulse-like motions are best approximated in the time domain using nonlinear response history analysis. Current approaches for incorporating pulse effects are not reproducible since they largely rely on engineering judgment and often result in unrealistic representation of the hazard. This study extends a method by Shahi and Baker (2011) that incorporates the effects of pulse-like motions in probabilistic seismic hazard analyses (PSHA). It uses disaggregation information from the PSHA to construct suites of target spectra that are used for matching an appropriate proportion of pulse-like motions with characteristics (pulse amplitude and pulse period) representative of a desired hazard intensity level. The methodology has been successfully employed for several high-profile projects in California that were subjected to a rigorous peer review process, including the Transbay Tower in San Francisco.

Geohazard assessment lifecycle for a natural gas pipeline project

This paper is a walkthrough of the geohazard risk assessment performed for the Front End Engineering Design (FEED) of a planned large-diameter natural gas pipeline, extending from Eastern Europe to Western Asia for a total length of approximately 1,850 km. The geohazards discussed herein include liquefaction-induced pipe buoyancy, cyclic softening, lateral spreading, slope instability, groundwater rise-induced pipe buoyancy, and karst. The geohazard risk assessment lifecycle was comprised of 4 stages: initially a desktop study was carried out to describe the geologic setting along the alignment and to conduct a preliminary assessment of the geohazards. The development of a comprehensive Digital Terrain Model topography and aerial photography data were fundamental in this process. Subsequently, field geohazard mapping was conducted with the deployment of 8 teams of geoprofessionals, to investigate the proposed major reroutes and delve into areas of poor or questionable data. During the third stage, a geotechnical subsurface site investigation was then executed based on the results of the above study and mapping efforts in order to obtain sufficient data tailored for risk quantification. Lastly, all gathered and processed information was overlain into a Geographical Information database towards a final determination of the critical reaches of the pipeline alignment. Input from Subject Matter Experts (SME) in the fields of landslides, karst and fluvial geomorphology was incorporated during the second and fourth stages of the assessment. Their experience in that particular geographical region was key to making appropriate decisions based on engineering judgment. As the design evolved through the above stages, the pipeline corridor was narrowed from a 2-km wide corridor, to a 500-m corridor and finally to a fixed alignment. Where the geohazard risk was high, rerouting of the pipeline was generally selected as a mitigation measure. In some cases of high uncertainty in the assessment, further exploration was proposed. In cases where rerouting was constrained, mitigation via structural measures was proposed. This paper further discusses the cost, schedule and resource challenges of planning and executing such a large-scale geotechnical investigation, the interfaces between the various disciplines involved during the assessment, the innovative tools employed for the field mapping, the classifications developed for mapping landslides, karst geology, and trench excavatability, determining liquefaction stretches and the process for the site localization of the Above Ground Installations (AGI). It finally discusses the objectives of the FEED study in terms of providing a route, a ± 20% project cost estimate and a schedule, and the additional engineering work foreseen to take place in the detailed engineering phase of the project.

System reliability analysis of granular filter for protection against piping in dams

Granular filters are provided for the safety of water retaining structure for protection against piping failure. The phenomenon of piping triggers when the base soil to be protected starts migrating in the direction of seepage flow under the influence of seepage force. To protect base soil from migration, the voids in the filter media should be small enough but it should not also be too small to block smooth passage of seeping water. Fulfilling these two contradictory design requirements at the same time is a major concern for the successful performance of granular filter media. Since Terzaghi era, conventionally, particle size distribution (PSD) of granular filters is designed based on particle size distribution characteristics of the base soil to be protected. The design approach provides a range of D15f value in which the PSD of granular filter media should fall and there exist infinite possibilities. Further, safety against the two critical design requirements cannot be ensured. Although used successfully for many decades, the existing filter design guidelines are purely empirical in nature accompanied with experience and good engineering judgment. In the present study, analytical solutions for obtaining the factor of safety with respect to base soil particle migration and soil permeability consideration as proposed by the authors are first discussed. The solution takes into consideration the basic geotechnical properties of base soil and filter media as well as existing hydraulic conditions and provides a comprehensive solution to the granular filter design with ability to assess the stability in terms of factor of safety. Considering the fact that geotechnical properties are variable in nature, probabilistic analysis is further suggested to evaluate the system reliability of the filter media that may help in risk assessment and risk management for decision making.

Developing seismic vulnerability curves for typical Iranian buildings

Iran is one of the most earthquake-prone countries in the world. In recent earthquakes, the low quality of constructions has caused huge losses, both in human and economic terms. The high level of seismic hazard in combination with a high physical vulnerability of structures leads to a high earthquake risk of Iran, which has to be managed in some ways. Earthquake happening in populated areas causing economic and human losses has shown the vital role of assessing buildings’ vulnerabilities as well as loss estimations. Vulnerability curve is one of the essential instruments to evaluate structural losses before the events. Regarding the lack of categorized vulnerability curves for Iranian buildings, this study focuses on filling this critical gap. For this reason, empirical approach involving statistical processing on existing data from the previous studies is used to develop vulnerability curves for Iranian buildings by critiquing the existing fragility/vulnerability curves in Iran and other countries. The logic-tree method is used to combine these curves by weighting in accordance with the condition of construction provisions, seismic code and engineering judgment. Finally, vulnerability curves are developed for the 42 Iranian building types. Results are presented by median ( Sa) and lognormal standard deviation [Formula: see text] values for all types of selected buildings and related uncertainties are considered as well.

Technology Focus: Reservoir Simulation (July 2015)

Technology Focus Coupled, full-field, integrated, holistic, or asset: Call it what you will, this class of modeling is becoming increasingly commonplace. The ability to interrogate the response of a system, from the reservoir to fiscal meter, is quite potent and encourages integration in all senses of the word—technically, operationally, and organizationally. Such end-to-end models may reveal bottlenecks, constraints, and potential flow-assurance issues. While the benefits are manifest, two related issues are worthy of consideration: complexity and piloting. The complexity of any individual component (such as the reservoir model) refers to the engineering judgment required to ensure that it is fit for purpose. For example, should one use a simple model (computationally rapid but approximate) or should a more complex model (computationally slower but accurate) be adopted? The former is better suited for rapid scenario screening and sensitivity analysis, while the latter is better suited for detailed engineering, with a spectrum of models in between. Piloting is another consideration. The degree of technical insight required to competently steer any single component simulator is often quite high. Having several simulators under a single, seamless platform places an extra burden on the pilots involved because the added layer of software (the integration platform) may mask possible shortcomings in a model, thus rendering potentially incorrect results and even suboptimal capital decisions. These considerations notwithstanding, I am genuinely optimistic about the potential these full-field models will bring and the insights they can deliver. More articles are certain to appear detailing predictions vs. observations and how planning, operations, and economics benefited from such integrated studies. I respectfully submit that the story of fully coupled, full-field, integrated asset modeling has only just begun. JPT

RCM and AHP hybrid model for road network maintenance prioritization

Category1 defects such as potholes significantly accelerate structural deterioration and pose imminent hazards on trunk road networks. Frequent occurrences of category1 defects have increased service disruptions on trunk road networks. Road maintenance agencies are now required to effectively prioritize trunk road network category1 defects maintenance works. However, existing road maintenance prioritization methods such as value engineering and traditional expert judgment methods have limitations. Value engineering is resource and time intensive thus best suited for project level prioritization and traditional expert judgments are subjective and lack audit trails. In an attempt to address the limitations of above methods, this study presents a Reliability Centered Maintenance and Analytical Hierarchy Process based hybrid model for trunk road network maintenance prioritization. The proposed hybrid model is used to establish failure diagnostic and Multi-criteria Decision Making respectively. As a case study, the hybrid model is implemented on a trunk road network in the United Kingdom. Relevant category1 defect failure information linked to trunk road network subassets are extracted from databases and relevant information elicited from maintenance experts. The criticality analysis results presented show the risk priority numbers of category1 defect related failures and cost effective preventative maintenance tasks are proposed. The Analytical Hierarchy Process results are used to address the complex prioritization process. The proposed hybrid model facilitates a systematic prioritization of a large number of trunk road network category1 defect failure maintenance activities consistently.

Impact of global climate change on the health, welfare and productivity of intensively housed livestock

Major scientific studies have shown that global warming (i.e. increasing average temperature of the Earth) is now a reality. The aims of this paper are to broadly review the underlining causes of global warming, the general effects of global warming on social and environmental systems and the specific effects of resulting from global warming phenomena severe fluctuations in weather patterns, particularly heat waves on livestock health, welfare and productivity. Finally this article aims to summarise some common sense climate control methods and more importantly to highlight the required future research and development (R&D) work that is necessary to achieve a new level of building environment control capability, and thus ensure that the intensive livestock industries will be able to cope with the changed external climate. With the increasing temperatures on a global scale, the most direct effect of the high temperature on the animals is heat stress, which has been proven to have a variety of negative effects on animal health, welfare and productivity. Different potential measures could be taken in future to alleviate the increased heat stress. Some of these measures are mere adaptations or improvements of current engineering solutions. However, facing the complex challenges of global warming and particularly resulting from it the rapid increase of the number of consecutive days with significantly higher than average temperatures will probably require novel solutions, including new designs based on solid engineering judgment, development of new engineering standards and codes to guide designs, the exploration of new and superior building materials, the need for better energy management, and the development of substantially more intelligentcontrol systems that will balance changing exterior disturbances, interior building loads and demands to the biological needs of the occupants of the structures.

From Code Compliance to Holistic Approaches in Structural Design of Bridges

In the process of designing structures such as bridges, engineers have to make design choices in light of uncertainty with the expectation that the structures they design, once built, perform as intended and do so with a sufficient degree of safety against failure and nonperformance. Consequences as a result of structural failures can be very high indeed, and it is vital that events such as these rarely occur. To achieve this end, the risks of failure should be addressed, understood, and controlled in such a way that they are deemed within acceptable limits for all stakeholders involved. According to Elms (1992), two primary strategies are used for controlling risks in engineering design: the first “is to be more conservative in design to allow for uncertainties : : : [and the second] : : : is to put more effort into careful risk assessment, to maintain safety levels and reduce risk while refining designs and reducing costs.” The prior strategy is a form of engineering heuristics (Koen 2003), which by definition cannot be absolutely proven but is, nevertheless, considered legitimate because it has been successfully implemented by generations of engineers in the past without any disproportionate rates of failure; examples include factors of safety applied in allowable stress design (ASD). The second approach to control risk, although arguably also a form of heuristic (e.g., Koen 2003), has its basis in the rational treatment of uncertainty as a calculable entity— something that can theoretically be reduced and altered such that risk-optimal design solutions can be obtained that are both safe as well as being cost-effective. The scientific rationalization and formalization of risk assessments in engineering design has led to theories, such as structural reliability theory (Freudenthal 1956), which are necessarily confined in their application compared with previous tried-and-tested methods of risk control based on design conservatism and engineering judgment. It is the virtue of a competent engineer to understand the limitations of such theories and give equal thought to the importance of heuristics in engineering design and the role of engineering judgment in yielding good (quality) designs (Addis 1990; Vick 2002; Davis 2012; Bulleit et al. 2014). The aforementioned approaches focus on what engineers themselves can do to help control risks in the process of designing structures. Viewed from a wider societal standpoint, the management of risks in engineering design requires addressing the broader issue of providing assurances that engineering professionals achieve this goal satisfactorily. To help address these issues (and to help legitimize the engineer as a professional), design codes and other formal standards of practice have been established (Shapiro 1997). Some of the primary purposes of these documents, hereafter simply referred to as design codes, include codifying current best engineering knowledge and practices as well as helping to ensure (and assure) that design risks are adequately treated by engineers, i.e., the design codes act as instruments for controlling risk. This development is important because it indicates a transfer of responsibility for controlling risk away from the individual engineers carrying out the design to the code-writing committees.

SPE Publishes Technical Report on Worst-Case Discharges

SPE Report In March, the SPE Board of Directors approved the publication of a technical report on the calculation of worst-case discharges (WCDs). The report, titled Calculation of Worst-Case Discharge, documents the consensus from an SPE-sponsored summit held in March last year. At the summit, 68 subject-matter experts met in New Orleans with the goal of improving the methods of calculating and reporting WCD scenarios. The attendees—representing operators, regulators, academia, and service providers—developed the report, which was made available for comment for 30 days and edited to include comments before being approved by the Board. The focus of the technical report is on the calculation of WCD rather than well design or intervention. Its primary application is in the US Gulf of Mexico, although the report may be used for wells elsewhere. Deterministic methods are proposed because of the wording of regulations and requirements for detailed well design and response planning. Probabilistic modeling and statistical analysis are unacceptable. All reservoir properties, the report says, should be best-estimate, success-case values based on sound geology, geophysics, and engineering judgment. All calculation parameter values should be explained and justified to ensure consistency and transparency. Parametric sensitivity is recommended for identifying the major variables and their impact on the WCD calculation. Topics covered in the technical report include reservoir properties, inflow modeling, outflow modeling, total volume, special cases, and reporting. Future improvements could include flow correlations for high rates in large-diameter pipes, sonic velocity effects, and probabilistic methods. The summit focused on defining methods for determining reasonable reservoir properties and fluid analog data to be used as modeling inputs for both shallow-water and deepwater wells. Discussions included the interaction of water sands and gas sands interspersed with oil sands, multiple sands in the same wellbore in various states of depletion, and the effects of secondary gas caps and water encroachment on calculated WCD values.