Formulation of Economic Assessment for Optimum Design Based on Structural Reliability.

Reliability design of structural system with cost effectiveness during life cycle

Life-cycle cost-based design procedure to determine the optimal environmental design load and target reliability in offshore installations

The present paper studies the reliability-based structural optimization of the civil engineering in the seismic zone. The objective is to minimize the sum of construction material cost and the expected failure loss under severe earthquake, which is obtained by the sum of the products of the failure probability and its failure losses for the important failure modes. The set of constraints includes the deterministic constraints, and the constraints based on structural reliability—the reliability index constraints of structural element failure for the serviceability state under minor earthquake and the failure probability of the structural system for the ultimate limit state under severe earthquake. By introducing the load roughness index, the structural system reliability computation under hazard load can be greatly simplified, which is approximately determined by its weakest failure mode. Finally, the numerical example of high rising shear RC frame is calculated.

This study presents a methodology for determining the optimal target reliability of a civil structure using the life-cycle cost (LCC) concept. The relationship between the reliability index and the estimated LCC is analyzed in order to find optimal target reliability. As a simple explanation of the method, the study uses steel bridges as an example. The analysis reveals that the LCC of steel bridges has great influence on target reliability, especially when the bridges have many lanes and long spans. It is also ascertained that higher target reliability is required to minimize the LCC when the number of lanes or average daily traffic (ADT) increases. Reliability analyses considering various traffic conditions were also conducted to observe changes in structural reliability with regard to such conditions. After the optimal target reliability is determined, target reliability adjustment can be performed. The analysis results show that the target reliability index can be adjusted consistently within the appropriate ranges by modifying the resistance factor in a limit state equation. In the last part of the study, an example bridge case study was performed to confirm the possibility of practical application of the presented method.

CHAPTER 11 - FILTER TESTING

An equivalent linear method for structural system reliability with nonlinear safety margins

<p>This paper compares the life cycle cost of two commonly used structural systems for buildings: the pre-fabricated steel structural system and the cast-in-situ concrete frame structural system. The case study of the No.2 experimental primary school building, located in Jiyang County in China, is presented as an illustrative example. The building is designed for six stories with 20.1 m in height and 9713.85 m2 construction area, considering 50 years life-span and 7 degrees seismic intensity scale. Ten design solutions are proposed for this case study covering these two types of structural systems, with the combination of different types of interior/exterior walls and slabs. A life cycle cost analysis is performed to evaluate the economic performance among these design alternatives, including the initial cost, construction cost, maintenance cost, removal cost and residual value. The result concludes that the pre-fabricated steel frame structural system has a significant advantage over the cast-in-situ concrete frame structural system from the total life cycle cost perspective.</p>

Uncertainty in the life cycle greenhouse gas emissions and costs of HDPE pipe alternatives

Improved X-Ray Safety, Quality Control, and Resource Management in Medical Imaging Using QATrack+

In this study, a comprehensive quality control (QC) system for in-situ precipitation data records was developed and applied to Canadian in situ precipitation datasets. The system includes a pair of screening procedures to screen for two types of random errors: one procedure is applied to the untransformed monthly total precipitation data series, which is good at finding erroneous data of unusually large values; another is applied to the log-transformed monthly precipitation data (in mm) series, log(P + 0.1), which is good at identifying erroneous zero or near-zero monthly total precipitation amounts. The system then applies three QC (threshold, kriging, and temporal) tests and a decision-making process to confirm whether the screened suspects are erroneous. There is generally good agreement between all the QC tests, while the decision-making process yields the most accurate results when compared to the manually reviewed results. The QC work on Canadian precipitation data sets revealed that it is necessary to apply a pair of screening procedures to identify both types of random errors. All the monthly values identified to be erroneous are set to missing, and so are the corresponding daily values, while keeping records of the original data.

The growing need for sustainable and resource-efficient materials increasingly promotes the use of block-glued laminated timber (glulam) in buildings and civil structures such as bridges. While timber is renewable and sustainable, the formaldehyde-based adhesives commonly used in glulam raise environmental and health concerns. This study addresses this gap by presenting one of the first combined life cycle assessment (LCA) and life cycle cost (LCC) analyses of bio-based versus synthetic adhesives for block-glued glulam. A pedestrian bridge in Zwolle, the Netherlands, serves as a case study. Three synthetic adhesives—melamine-urea formaldehyde (MUF), phenol resorcinol formaldehyde (PRF), and phenol formaldehyde (PF)—and two bio-based alternatives—lignin phenol glyoxal (LPG) and tannin-furfuryl alcohol formaldehyde (TFF)—are analyzed. The LCA covers raw material sourcing, transport, and end-of-life scenarios, with impacts assessed in accordance with EN 15804+A2 using Earthster and the Ecoinvent v3.11 database. The proposed method integrates environmental and economic assessments, with results presented both per kilogram of adhesive and per cubic meter of glulam to ensure comparability. Results show that synthetic adhesives have higher environmental impacts than bio-based adhesives: the carbon footprint of 1 kg of adhesive averages 0.60 kg CO2-eq for bio-based adhesives and 2.01 kg CO2-eq for synthetic adhesives. LCC are similar across adhesives, averaging EUR 400 per m3 of glulam. These findings suggest that bio-based adhesives can compete environmentally and economically, but their limited availability and uncertain long-term performance remain barriers. Overall, the study highlights trade-offs between sustainability and structural reliability and provides guidance for sustainable adhesive selection in timber engineering.

Civil infrastructure assets, such as roads, locks, bridges, treatment plants and storm surge barriers, are often characterised by long service lives and corresponding technical life cycles. When life cycles are long, the time value of money plays a role in asset management decision-making on capital investments and operation and maintenance expenditures. In this paper, a new life cycle costing (LCC) approach for discounting in two classes of maintenance optimisation models is developed. These models are the age replacement model and the interval replacement model. Three well-known LCC techniques, which are the present worth, the capital recovery and the capitalised equivalent worth, are combined and used to develop a stepwise methodology. This methodology is validated with the few case-specific mathematical equations that exist in the literature. The advantage of using this alternative LCC approach is its applicability and flexibility for reliability and maintenance engineers. The resulting LCC method builds on well-known LCC formula and enhances the understanding of the inclusion of discounting principles in reliability models. Understanding these principles makes the method flexible. Practitioners can extend or adapt the method to changing circumstances, such as additional cash flows and altering reliability modelling.

The results of a long-term, comprehensive CT quality control (QC) program were analyzed to investigate differences in failure rates based on QC test, scanner utilization pattern, and number of channels, as well as explore issues regarding testing frequency. CT QC data were collected over a 4-yr period for 26 CT scanners representing two different vendors and using three different QC programs culminating in over 100 scanner-years of QC data. QC tests analyzed included water tests [mean CT number, standard deviation, and uniformity], linearity tests [air, water, and acrylic], and artifact analysis [water phantom and large phantom]. The data were organized based on scanner use, number of channels, scanner modality, and QC test. Logistic regression model analysis with generalized estimating equation method was used to estimate failure rates for each group. A significant difference between failure rates with respect to QC test was found (p-value = 0.02). Large phantom artifacts, standard deviation of water, and water phantom artifacts had the three highest failure rates. No significant difference was found between failure rates organized by scanner use, scanner modality, or number of channels. Standard deviation of water is the most important quantitative value to collect as part of a daily QC program. Uniformity and linearity tests have relatively low failure rates and, therefore, may not require daily verification. While its failure rates were moderate, daily artifact analysis is suggested due to its potentially high impact on clinical image quality. Weekly or monthly large phantom artifact analysis is encouraged for those sites possessing an appropriate phantom.

Quality-control tests for OC4, OC5 and NIR-red satellite chlorophyll-a algorithms applied to coastal waters

PurposeThe aim of this research is to carry out a literature review of the use of life cycle costing (LCC) in the urban agriculture (UA) sector by analysing its evolution over a 22-year period from its beginning in 1996 to July 2018.MethodsA total of 442 references were obtained from two principal databases, Scopus and Web of Science (WoS). After a long refining process, 20 (4.5%) references containing the keywords LCC and UA were selected for analysis. Then, we classified and organized the selected references in 4 groups. Qualitative methods were used for analysis, and results on general characteristics of the 20 references and by each group were elaborated. Lastly, we discussed and concluded the most significant findings. Limitations and future research were also included.Results and discussionOur major findings were as follows: (i) urban horticulture was the most studied urban agriculture practice among studies that used LCC for UA; (ii) LCC plays a secondary role in its integration with LCA; (iii) only 4 of the10 papers in group 1 used additional financial tools; (iv) very few (3) papers appropriately applied the four main LCC stages; and on the other side, essential costs like infrastructure, labour, maintenance, and end-of-life were frequently not included.ConclusionsSince we found that life cycle assessment (LCA) was the predominant methodology, we suggest that future research apply both LCA and LCC analyses at the same level. The LCC analysis was quite incomplete in terms of the costs included in each LCC stage. We recommend that the costs at the initial or construction stage be considered a necessity in future studies in order to implement these new systems on a large scale. Due to the limited use of labour cost at the operation stage, we also suggest that labour be included as an essential part of the urban production process. Finally, for more complete LCC analysis for UA, we recommend (i) that all LCC stages be considered and (ii) that additional financial tools, such as net present value (NPV), internal rate of return (IRR) and payback period (PBP), be used to complement the LCC analysis.