Life Cycle Assessment Of Structures Research Articles

Design-related reassessment of structures integrating Bayesian updating of model safety factors

In the semi-probabilistic approach of structural design, the partial safety factors are defined by considering some degree of uncertainties to actions and resistance, associated with the parameters’ stochastic nature. However, uncertainties for individual structures can be better examined by incorporating measurement data provided by sensors from an installed health monitoring scheme. In this context, the current study proposes an approach to revise the partial safety factor for existing structures on the action side, γ E by integrating Bayesian model updating. A simple numerical example of a beam-like structure with artificially generated measurement data is used such that the influence of different sensor setups and data uncertainties on revising the safety factors can be investigated. It is revealed that the health monitoring system can reassess the current capacity reserve of the structure by updating the design safety factors, resulting in a better life cycle assessment of structures. The outcome is furthermore verified by analysing a real life small railway steel bridge ensuring the applicability of the proposed method to practical applications. • An approach to revise the model safety factor within the semi-probabilistic design concept for existing structures is presented employing Bayesian inference theory. • The study has demonstrated the importance of knowing the prior distribution of the structural parameters in advance, as well as how to integrate new measurement data into the evaluation process to update the current state of the structure. • Measurement data uncertainties have a considerable impact on posterior probability, as demonstrated by varying the uncertainty values from 1% to 10% in different sensor configurations. • The proposed method is verified using a real life structure, a small railways steel bridge, and is shown that, even data from a single sensor is helpful to revise the initial design parameters. • For heavily utilized structures, the proposed measurement-based design adjustment aids in more accurate evaluation and utilization of capacity reserves, emphasizing the need of incorporating measurement data into the design calibration process.

A Delphi study to identify and prioritize research gaps for the incorporation of a fire into life cycle assessment of structures

The current life cycle assessment (LCA) methodology used in structural engineering does not consider hazards like fires within its scope. Various efforts have been made to identify research gaps that need to be filled in order to accomplish a Fire-LCA. This study presented research gaps from literature to experts to determine the research gap's impact, desirability, and probability of occurrence by the year 2030. The study provides insight into what researchers should prioritize to accomplish the proposed Fire-LCA methodology. In each round the experts were asked to evaluate and comment on the impact, desirability, and probability of occurrence by the year 2030 of each identified research gap. The results of the Delphi questionnaire identified high priority research gaps for the implementation of the proposed Fire-LCA methodology. The most prioritized research gap was statistical data that would describe the number and severity of fires, fire origin, and extent of fire spread in different types of building. The results of this study can guide researchers and funding agencies to prioritize research that will fill key gaps in knowledge that prevent the implementation of a Fire-LCA methodology for building structures. • Gaps in knowledge exist and prevent the implementation of a Fire-LCA methodology for buildings. • Statistical data and reporting of real building fires is needed for the implementation of a Fire-LCA methodology. • Experts across the world do not agree on research priorities to fill gaps in knowledge needed to implement a Fire-LCA.

Environmental Performance of Residential Buildings: A Life Cycle Assessment Study in Saudi Arabia

The building and construction sector has a huge impact on the environment because of the enormous amounts of natural resources and energy consumed during the life cycle of construction projects. In this study, we evaluated the potential environmental impact of the construction of a villa, from cradle to grave, in the Saudi Arabian context. Centrum voor Milieukunde Leiden (CML) for Centre of Environmental Science of Leiden University-IA baseline v3.03 methods were used to obtain the environmental profile for the impact categories, and Cumulative Energy Demand v1.09 was used to measure the embodied energy of the villa life cycle. The analyzed midpoint impact categories include global warming (GWP100a), ozone layer depletion (ODP), acidification (AP), eutrophication (EP), photochemical oxidation (POCP), and indicator cumulative energy demand (CED). The operation use phase of the villa was found to have the highest global warming potential and acidification with 2.61 × 106 kg CO2-eq and 1.75 × 104 kg SO2-eq, respectively. Sensitivity analysis was performed on the Saudi Arabian plans to increase the share of renewable sources and reduce the amount of electricity generated from hydrocarbons, which currently represents 46% of the total installed power, by 2032. The results showed that compared with the current electricity environmental impact, the CO2 emission from electricity will decrease by 53%, which represents a significant reduction in environmental impact. The findings will help with the life cycle assessment of structures during future planning and for energy conservation.

Repercussion the use phase in the life cycle assessment of structures in residential buildings using one-way slabs

Abstract This study incorporates the use phase in the life cycle assessment (LCA) of reinforced concrete structures that are composed of one-way slabs. Sustainable construction is one of the main future objectives of the European Union; therefore, useful and reliable tools will be necessary for its implementation. The usefulness of the LCA for the selection of structural alternatives depends on the data quality. The Environmental Product Declarations collect the production phase of building materials, but it is necessary to incorporate the particularities in the implementation and use phases. This work proposes a stage that considers the use phase in the structural part that does not belong to the building envelope and provides a methodology that reflects the characteristics of each climate zone where it is applied. All of the representative variables to define the structure of a building are combined: column grids, variations in the geometry of one-way slabs, and different materials. A discrete model that incorporates 360 cases is constructed to compare the reliability of the model with a study on real structure projects. The results show the importance of the use phase in residential buildings with respect to the effects generated during the other phases (production, execution and demolition), as well as its high variations, up to 140.4%.

The use of a credibility index in the life-cycle assessment of structures

The behaviour of structural systems can change during their service lives due to unexpected loadings, environmental effects and deterioration processes. In order to optimise maintenance interventions, the life cycle of a structure has to be properly assessed. Structural health monitoring (SHM) using collected experimental data provides a method for assessing structural behaviour over time. As the cost related to SHM is substantial, sometimes that monitoring is limited in space and time. However, the modelling of the structural behaviour using experimental data-sets is characterised by increased uncertainty both in the choice of the appropriate model (epistemic uncertainty) and in parameters estimation (aleatory uncertainty). This paper provides an original procedure to support decisions in the presence of epistemic uncertainty. The procedure provides the development of a credibility index able to catch, between two possible models, which is the most reliable to describe the evolution of parameters of interest. Considering as a case study the occurrence of a foundation settlement in an arch bridge, the efficacy of the model proposed is assessed. The approach can be applied to investigate the behaviour of other aspects of the life-cycle assessment: the evolution of structural resistance, the failure time of an element or of the whole system.

Enabling optimization in LCA: from “ad hoc” to “structural” LCA approach—based on a biodiesel well-to-wheel case study

Applied life cycle assessment (LCA) studies often lead to a comparison of rather few alternatives; we call this the “ad hoc LCA approach.” This can seem surprising since applied LCAs normally cover countless options for variations and derived potentials for improvements in a product life cycle. In this paper, we will suggest an alternative approach to the ad hoc approach, which more systematically addresses the many possible variations to identify the most promising. We call it the “structural LCA approach.” The goals of this paper are (1) to provide basic guidelines for the structural approach, including an easy expansion of the LCA space; (2) to show that the structural LCA approach can be used for different types of optimization in LCA; and (3) to improve the transparency of the LCA work. The structural approach is based on the methodology “design of experiments” (Montgomery 2005). Through a biodiesel well-to-wheel study, we demonstrate a generic approach of applying explanatory variables and corresponding impact categories within the LCA methodology. Explanatory variables are product system variables that can influence the environmental impacts from the system. Furthermore, using the structural approach enables two different possibilities for optimization: (1) single-objective optimization (SO) based on response surface methodology (Montgomery 2005) and (2) multiobjective optimization (MO) by the hypervolume estimation taboo search (HETS) method. HETS enables MO for more than two or three objectives. Using SO, the explanatory variable “use of residual straw from fields” is, by far, the explanatory variable that can contribute with the highest decrease of climate change potential. For the respiratory inorganics impact category, the most influencing explanatory variable is found to be the use of different alcohol types (bioethanol or petrochemical methanol) in biodiesel production. Using MO, we found the Pareto front based on 5 different life cycle pathways which are nondominated solutions out of 66 different analyzed solutions. Given that there is a fixed amount of resources available for the LCA practitioner, it becomes a prioritizing problem whether to apply the structural LCA approach or not. If the decision maker only has power to change a single explanatory variable, it might not be beneficial to apply the structural LCA approach. However, if the decision maker (such as decision makers at the societal level) has power to change more explanatory variables, then the structural LCA approach seems beneficial for quantifying and comparing the potentials for environmental improvement between the different explanatory variables in an LCA system and identifying the overall most promising product system configurations among the chosen PWs. The implementation of the structural LCA approach and the derived use of SO and MO have been successfully achieved and demonstrated in the present paper. In addition, it is demonstrated that the structural LCA approach can lead to more transparent LCAs since the potentially most important explanatory variables which are used to model the LCAs are explicitly presented through the structural LCA approach. The suggested structural approach is a new approach to LCA and it seems to be a promising approach for searching or screening product systems for environmental optimization potentials. In the presented case, the design has been a rather simple full factorial design. More complicated problems or designs, such as fractional designs, nested designs, split plot designs, and/or unbalanced data, in the context of LCA could be investigated further using the structural approach.