Lifetime cost optimization of structures by a combined condition–reliability approach

Cost optimization for the determination of the most effective maintenance strategy of deteriorating structures has recently been used by researchers and accepted by experts. The main reasons for this lie in strict requirements of budgetary efficiency and in reliability requirements for structures. Accessible data directly related to structural performance include the condition state, obtained from generally stipulated visual inspections, and the reliability state, derived from the inspection or monitoring programs combined with numerical computations. In this paper, a novel approach to cost models for condition and reliability profiles is described. Global cost optimization can be achieved by means of multi-objective optimization or by means of a Cost-Optimized Condition-Reliability Profile (COCRP) approach. Since the assessment of structures is under uncertainty, it is essential to embed the COCRP concept in a full probabilistic framework. Probabilistic COCRP computations can be performed, even for complex structures, within a reasonable time by using advanced Monte Carlo Methods such as Latin Hypercube Sampling. The proposed COCRP approach allows realistic and efficient treatment of structures that involve uncertainties and detects the parameters having the most significant effects on lifetime cost.     

Optimized maintenance and renovation scheduling in multifamily buildings – a systematic approach based on condition state and life cycle cost of building components

Proactive maintenance strategies in principle are devised to control degradation and sustain optimal performance of building components. While realizing the technical necessities, they also serve as an instrument towards multiple and often conflicting objectives during financial constraints. An optimal proactive maintenance strategy therefore should comprise a multiannual maintenance action plan optimized on different criteria corresponding to owners’ objectives under existing constraints. This study offers a systematic approach based on a condition-deterioration model to address the complexity involved in decision making regarding optimized maintenance and renovation planning. Life-cycle cost analysis in form of Equivalent Annual Cost (EAC) is used for the economic assessment of maintenance/renovation scenarios. In this paper, the model is used to compare the economy of different maintenance/renovation plans in a chosen scenario in order to determine the optimal maintenance interval for a single and a combination of building components. Two façade elements, windows and façade rendering, are used to illustrate the application of the proposed method. This method is intended to help decision makers at both design and post-construction phases in the choice of both building components and maintenance/renovation strategies.     

Real-time optimization of a double-skin façade based on lumped modeling and occupant preference

Real-time optimization of a double-skin façade system is developed for the so-called smart façade systems. It optimizes the performance of the system by rotating a motorized louver slat in the cavity and ventilation dampers at the top and bottom of exterior and interior glazing. One prominent feature of the system is the capability of dynamically reacting to the environmental input data through real-time optimization in terms of energy, visual comfort and thermal comfort. Users interaction with the system is Web enabled. Current state variables, weather data and energy flows are posted on a web page and an occupant with given privileges can choose the preferred operation mode or override the devices (louvers, ventilation inlet/outlet).     

The cost of satisfying design requirements on progressive collapse resistance – Investigation based on structural optimisation

This work is concerned with the explicit treatment of progressive collapse resistance within the structural design process. Progressive collapse resistance is associated with the damage tolerance of a structural system and controls the ability of the system to sustain local damage by absorbing the potential of triggering system collapse and suffering disproportionally large consequences. This work focuses on the design of elastoplastic steel frames. The measure of progressive collapse resistance employed is expressed as a ratio comparing the limit loads obtained with elastoplastic analyses of the intact structure and of an artificially damaged structure (‘damage’ is caused by the notional removal of a column from the intact structure). This measure is used to incorporate a constraint on progressive collapse resistance into a structural design optimisation formulation, which – in its classical form – takes only standard design code constraints into account and aims at minimising the structural cost. The developed optimisation approach is capable of producing cost-effective structural designs with acceptable system damage tolerance. By enforcing the satisfaction of the additional design requirement on progressive collapse resistance, structural cost is inevitably increased due to the need for extra material. This increase is quantitatively explored with the presented structural design optimisation approach.     

Energy and emergy based cost–benefit evaluation of building envelopes relative to geographical location and climate

This paper presents an environmental evaluation of building envelopes, made of three different technologies: a traditional air-cavity wall, a plus-insulated wall (with an external cork covering), and a ventilated wall (with external brick panels fixed on extruded frames). An environmental accounting method, namely Emergy Evaluation (EE), was performed for assessing environmental resource use (energy and material flows), both directly and indirectly, for the construction of a façade (1000 m²). Then, energy use during the building lifetime was assessed as a constant inflow to the building depending on the thermal skills of building envelopes, besides thermal efficiency of air-conditioning system. In particular, this energy inflow is needed for maintaining constant indoor climate conditions (18 °C) and has to balance heat dissipation through envelopes (heat loss in winter and heat gain in summer). Outcomes were compared with an Energy Analysis (EA) based on an embodied energy accounting. Finally, costs for manufacturing walls (with enhanced performance) and benefits (energy saving) were compared in a unique balance, through both EA and EE. Moreover, outcomes were obtained for three scenarios corresponding to three geographic locations (Berlin in northern Europe, Barcelona on the Mediterranean coast and Palermo in the south of Italy). Results highlighted that performances of building envelopes depend on technologies relative to external climate conditions. Different environmental accounting methods, such as EE and EA, provided outcomes with some difference that are not contradictory to each other but complementary.     

Proximity,accessibility and choice: A matter of taste or condition?*

Drawing on a combination of register data and travel survey data, this research explores changes in the accessibility to different amenities for the Swedish population between 1995 and 2005, as well as the reasons behind the changes: redistribution of either amenities or the population. Overall, proximity has increased concerning most of the amenities during the period. However, despite decreasing ‘potential’ distances, actual travel distances are growing longer due to, for example, an increasing selectivity in preferences. An analysis of the accessibility development for service amenities shows that restructuring within the service sector is the main cause of the changes, and to a lesser extent population redistribution. Resumen. Haciendo uso de una combinación de datos de registros y encuestas de viajes, este estudio explora cambios en la accesibilidad de diferentes servicios y lugares de recreo para la población sueca entre 1995 y 2005, así como las razones detrás de dichos cambios: una redistribución de los servicios o de la población. En conjunto, la proximidad ha aumentado con respecto a la mayoría de los servicios durante el periodo estudiado. Sin embargo, a pesar de las reducciones en distancias “potenciales”, las distancias de viaje están aumentando debido a por ejemplo una mayor selectividad en las preferencias. Un análisis del desarrollo de la accesibilidad de servicios y ocio muestra que la reestructuración dentro del sector servicios es la causa principal de los cambios y, en menor medida, la redistribución de la población.      

Genetic algorithms based optimization of artificial neural network architecture for buildings’ indoor discomfort and energy consumption prediction

Growing concerns about energy consumption reduction and comfort improvement inside buildings make it more and more necessary to be able to predict with fine precision building’s heating loads and indoor discomfort. This article proposes a method based on genetic algorithms (GAs) to optimize the architecture, training parameters and inputs of an artificial neural network (ANN). The ANN is doomed to predict energy consumption and indoor discomfort in future work on the development of an on-line method for control setting optimization. Simple and advanced controllers were used in this study: ON-OFF, PID and fuzzy controllers. Validation of the optimized ANN showed good prediction accuracy, as regression coefficients R ² for consumption and discomfort were respectively greater than 0.77 and 0.84 for the three tested controllers. Various prediction “distances” and ANN training data quantities were tested. Conclusion is that prediction at a 2-hour “distance” and a 3-day quantity of data are the best tested optimization conditions.     

Estimation of radiance reflectance and the concentrations of optically active substances in Lake Mälaren, Sweden, based on direct and inverse solutions of a simple model

A semi-analytical model which predicts radiance reflectance just below the water surface (Lu/Ed 0-) has been developed and used to predict the spectral variability of radiance reflectance in Lake M?laren, Sweden. Radiance reflectance is predicted as a function of the optically active substances in the water, which include the concentrations of chlorophyll-a + phaeophytin-a, suspended particular inorganic material (SPIM), suspended particulate organic material (SPOM), and dissolved yellow substances. These substances are linked to the absorption and backscattering coefficients through a series of empirical relationships, and ultimately radiance reflectance is estimated as a function of the ratio of backscattering to absorption. Parameterization of the model, i.e. the development of the empirical relationships linking the optically active substances to the inherent optical properties (IOPs), is based on both in situ measurements and laboratory analyses. We have collected data that allowed us to examine the potential variability in radiance reflectance, as predicted by our model, due to both variations in the optically active substances, and in the model parameterization. Simulations based on a data set collected during the fall of 1997 from 12 sites, which span a large range in water quality (secchi depth 0.8-5.0 m), suggest that, with the proper parameterization, the model can accurately predict the spectra of radiance reflectance as a function of the concentration of optically active substances. Variations in the concentrations of optically active substances accounted for a large portion of the total simulated variability in radiance reflectance (i.e. that resulting from variations in parameterization and in the concentrations of optically active substances). However, the measured variability in parameterization could account for up to 50% of the total variability in simulated radiance reflectance. This suggests that variability in the model parameterization, arising from both real variability and experimental error, will limit the use of this model for interpreting remote sensing data. Nevertheless, inverse solutions of the model are able to estimate the concentrations of chlorophyll, suspended inorganic material (SPIM) and the absorption of yellow substances from measured radiance reflectance spectra The average error for the 12 sites was a -0.07 for chlorophyll, -0.15 for dissolved yellow substances (measured as the absorption at 400 nm) and 0.07 for SPIM, even though individual errors could be as great as 50%.     

Materiality investor perspectives on utilities’ ESG performance. An empirical analysis of ESG factors and cost of equity

The last years have seen significant growth in the demands and use of Environmental, Social, and Governance (ESG) data and ratings, which have relevant market implications and affect the value of firms based on prior evidence. However, little is known about the materiality of ESG factors to investors’ risk perceptions. This paper contributes to this debate by analyzing the relationship between the ESG performance of utility companies and the cost of equity capital. Using fixed-effect panel regressions on a sample of 273 firm-year observations between 2017 and 2021, this paper provides novel insights with significant theoretical and practical implications.     

Realization of uniform deformation of soil specimen under undrained plane strain condition based on soil–water coupled finite deformation analysis considering inertia forces

Based on a soil–water coupled finite deformation analysis, theoretical considerations and numerical calculations were carried out under the undrained plane strain condition in order to reproduce a uniform deformation field. Rather than the “quasi-static” equation of motion, which does not include inertia forces, a dynamic equation of motion which includes inertia forces was used. At first, a theoretical consideration was carried out to realize uniform deformation for a saturated soil that satisfied the element-wise undrained/constant-volume condition. This presents an “infinitely slow loading” case without ignoring the inertia term based on the u–p formulation. In other words, it can be seen that under general slow loading that is not infinitely slow, a gradient in the pore water pressure will always be produced, resulting in the migration of pore water and loss/collapse of uniformity. This first conclusion is useful for verifying numerical analysis code made in the finite deformation regime. Next, the uniform deformation of a plane strain rectangular soil specimen was measured under constant cell pressure and undrained boundary conditions using a dynamic soil–water coupled analysis in which the SYS Cam-clay model was employed as the elasto-plastic constitutive model for the soil skeleton. In addition, the effects of the loading rates as well as loading applications, with/without inertia forces, on the loss of uniformity in deformation were shown to have a significant influence on the inertia term even though the loss itself was extremely small.     

Quantitative evaluation of rock brittleness based on crack initiation stress and complete stress–strain curves

Bulletin of Engineering Geology and the Environment - Brittleness is an important rock material property, and its accurate evaluation has guiding significance in construction as well as in disaster...     

Selectivity of new inorganic ion–exchangers based on oxides of titanum and manganese at sorpion of lithium from aqueous media

We have obtained new composite materials of TiO₂–MnO₂ saturated with lithium ions and treated at 500 and 600°C. Using methods of low-temperature adsorption of nitrogen, infrared and X-ray spectroscopy their structural properties were investigated. It has been shown that given ion–exchangers display substantial selectivity at sorption of lithium ions with respect to other cations.     

Bridge user cost estimation – a synthesis of existing methods and addressing the issues of multiple counting,workzones and traffic capacity limitation

Efforts to incorporate the concerns of bridge users in bridge investment evaluation are often stymied by lack of a comprehensive framework for assessing different user costs. There is a need to synthesise and update existing user cost estimation techniques so that the incorporation of user costs in bridge investment evaluation can be more consistent and streamlined. Secondly, a bridge detour may occur for more than one reason, thus there is a danger of multiple counting that could cause overestimation of user costs. Thirdly, user costs during bridge workzones have rarely been considered in the literature. To address these issues, this article presents a framework for comprehensive estimation of bridge user costs, an approach to address the multiple-counting problem, and a methodology for bridge workzone user cost estimation. Furthermore, the article develops a method to estimate bridge user delay cost due to traffic capacity limitation. The methodologies are demonstrated using a case study.     

Project management and burnout: Implications of the Demand–Control–Support model on project-based work

Project-based work has long been characterized as frenetic, fast-paced, and dynamic. The often competing constraints imposed by schedules, stakeholders, and budgetary restrictions make project activities conflict-laden and highly conducive to work-related stress. Stress is not an end unto itself but instead, is often a precursor for burnout. Burnout is a psychological syndrome of emotional exhaustion, cynicism, and reduced personal accomplishment. This paper reports on the results of a study of burnout among project management personnel. Using the Demand–Control–Support model as our conceptual framework, we analyzed a sample of respondents from four project-intensive organizations. Our findings demonstrated that women tend to experience emotional exhaustion to a greater extent than their male counterparts. Further, control and social support do serve as moderators for the burnout dimensions of emotional exhaustion and cynicism, suggesting limited support for the Demand–Control–Support model. Implications of this study for project management and workplace burnout are discussed.     

Effects of pre-existing cracks and infillings on strength of natural rocks – Cases of sandstone,argillite and basalt

This study aims to examine the influence of pre-existing discontinuities on the strengths of four natural rocks of different origins. A series of unconfined compression tests was performed on specimens of two types of sandstones, argillite and basalt that contain open and filled cracks. It was found that the presence of cracks tends to decrease the overall strength for all studied rocks; however, the magnitude of strength reduction is related to the property of rock. The larger strength decrease was observed for the relatively harder argillite and basalt, compared to the softer sandstone. It was also found that the infill material could increase the strength of rock specimens, while the obtained strength depended on the characteristics of the fill material.     

Mixture design concept and mechanical characteristics of PS ash–cement-treated clay based on the water absorption and retention performance of PS ash

In an attempt to reduce environmental impact, paper sludge ash (PS ash) has recently been studied for its complementary reuse with cement for soil stabilization. In order to establish the optimal mixture design for combining PS ash and cement in soils, a detailed investigation into the stabilizing mechanism is required. To assess the combined effects of PS ash and cement on the strength development of stabilized clay soil, referred to as PS ash–cement-treated clay, a new critical parameter, the unabsorbed and unretained clay-water/cement ratio W*/C, was proposed. To determine W*/C, a new testing method for evaluating the water absorption and retention performance of PS ash was developed. It was revealed that the water absorption and retention rate W_ab of PS ash increased with curing time. Unconfined compression tests conducted on the PS ash–cement-treated clay with various water-cement–PS ash mixture proportions and different curing times affirmed that the strength development was fundamentally governed by the parameter W*/C. This suggests that the water absorption and retention rate W_ab obtained by the developed method is an essential material parameter in the mixture design for the PS ash–cement-treated clay. It was also found that the effect of the hybrid treatment method, which uses both cement and PS ash, was better than that of the method which uses cement alone, particularly under high W*/C conditions. This indicates that the water absorption and retention performance of PS ash can be fully utilized when the mixture has sufficient unabsorbed and unretained water for cement hydration.     

Spatial patterns of residents’ daily activity space and its influencing factors based on the CatBoost model: A case study of Nanjing,China

The complexity and fragmentation of people's activity space are challenging to planners. However, the relevant studies are mostly concerned on the relationship between the social attributes and the activity space of residents in a single or several communities, or the spatiotemporal laws of activity space on a macro scale. The research on the spatial characteristics of residents' activity space still needs to be strengthened. The present study analyses the spatial patterns of residents' activity space based on mobile phone signaling data to fill the gap of previous studies that assessed residents' activity space across small geographic areas. First, according to the spatial scope and direction of an activity space and residents' activity coverage rate, spatial patterns can be divided into three types: compact, extended, and directional extension patterns. The CatBoost method is then used to statistically analyze the influencing variables of spatial patterns, and the order of importance of the following influencing factors is determined: the built environment is more influential than social and economic situations. This study aims to strengthen the understanding of residents' activity space at the spatial level and provide a basis for the optimization of communities with different spatial patterns.