A systematic approach for maintenance budgeting of buildings façades based on predictive and preventive strategies

Maintenance strategies are essential to control the first stages of degradation and prevent the failure of building elements. The selection of the most cost-effective and appropriate strategies can enable better budget allocation and can also minimize the decline in the performance of buildings during their whole life cycle. This paper characterizes a systematic methodology for selecting optimal maintenance strategies for façades based on different maintenance policies and interaction with the user. Life-cycle cost analysis is used to compare different maintenance scenarios using equivalent uniform annual cost (EUAC) for five façades’ claddings. These scenarios are compared through the simulation of performance–degradation models and characterization of several parameters: service life, performance, minimum level of quality, maintenance operations, frequency and costs. The results allow the comparison of preventive and predictive maintenance strategies. This methodology, the result of a two-year academic research program, is intended to help clients, users, practitioners and decision-makers in the choice of facades’ interventions (type, frequency and cost estimation) at buildings’ design and post-occupancy stages. Finally, the future drawbacks and benefits of this study are discussed.     

Maintenance and management of civil infrastructure based on condition,safety, optimization,and life-cycle cost∗

Cost-competent maintenance and management of civil infrastructure requires balanced consideration of both the structure performance and the total cost accrued over the entire life-cycle. Most existing maintenance and management systems are developed on the basis of life-cycle cost minimization only. The single maintenance and management solution thus obtained, however, does not necessarily result in satisfactory long-term structure performance. Another concern is that the structure performance is usually described by the visual inspection-based structure condition states. The actual structure safety level, however, has not been explicitly or adequately considered in determining maintenance management decisions. This paper reviews the recent development of life-cycle maintenance and management planning for deteriorating civil infrastructure with emphasis on bridges using optimization techniques and considering simultaneously multiple and often competing criteria in terms of condition, safety and life-cycle cost. This multiple-objective approach leads to a large pool of alternative maintenance and management solutions that helps active decision-making by choosing a compromise solution of preferably balancing structure performance and life-cycle cost.     

Goal directed life cycle costing as a method to evaluate the economic feasibility of office buildings with conventional and TI‐façades

Transparent insulation systems (TI‐systems) of less than 20cm thick have been developed as an alternative to opaque wall insulation and windows, which provide a financial return to building occupants when applied to building façades. Lack of detailed cost analysis of TI‐systems is a major constraint to the application of TI‐wall and TI‐glazing in buildings. A goal directed life cycle costing (LCC) technique and sensitivity analysis used to evaluate the economic feasibility of TI‐applications in office buildings form the basis of this research. It was undertaken as part of research to determine optimum energy and cost performance of TI‐systems for external cladding of high‐rise and low‐rise office buildings in temperate and tropical climates. The LCC of the buildings with conventional façades were compared with those with TI‐façades. The results show that LCC can be used to evaluate the economic feasibility of low carbon technologies such as TI‐systems effectively. A detailed account is provided of how different sources of cost data can be captured, collected and integrated to perform selective goal directed LCC analysis in the absence of detailed historical LCC data. The use of the goal directed LCC method and cost influence diagram presented in this research can be adopted as a standard method for assessing the economic feasibility of applying low carbon technologies to buildings.     

A study on the building of a new “output–output model” and its usefulness: based on a comparative analysis of the input–output model

This paper describes the building of a new open static “output–output” (O–O) model in comparison to the open static input–ouput (I–O) model developed by Leontief (Rev Econ Stat 18:105–125, 1936). While the I–O model can be characterized as a system that relates final demand to gross output, the O–O model relates gross output for final demand (endogenous or exogenous) to gross output for output (endogenous). We perform a comparative analysis between the two models in structure and characteristics and illustrate the usefulness of the O–O model, for example, by formulating I–O multipliers that can accept output as an initial change. The comprehensive analysis conducted in this paper, including a numerical illustration with an example, shows that the two models form a mutually supplementary relationship and could give rise to a fundamental framework for the analyses of various regional and national economic activities.     

Mirror of the state or independent image? – Conceptual perspectives on the question of a legitimacy shift to the output dimension in local democracy

This contribution discusses the theoretical and conceptual implications of asking about the legitimacy of local democracy and the relevance of discussing ‘performance legitimacy’. The role of local government in generating or undermining democratic legitimacy is ambivalent. It is questionable whether there can be something like a genuine legitimacy of local government at all, considering its subordinate and functionalised role in the modern (welfare) state. In the first part of the article, the complexity and controversial status of political legitimacy in general and local government in particular is exposed. It is argued that the effective interplay of justification (giving acceptable reasons for policies) and demonstration (performing successfully by fulfilling promises), which is at the core of generating legitimacy, cannot be deduced from general concepts and fixed in a general model. Generating a self-reinforcing dynamic of public support and linking different dimensions of legitimacy (input, throughput, output) is a matter of reflexive institutionalisation. Being part of a democratic welfare state has provided local governments in Western democracies with a stabilised focus of legitimacy. At the same time, local governments are particularly under pressure to adapt, to innovate and to modernise. Four broader narratives of changing democratic legitimacy sources with respect to local government are discussed. The shift to ‘performance legitimacy’ has to be seen in a wider context of redefining the meaning of (local) democracy as mapped out by the four narratives.     

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%.     

Perspectives in planning history: planning and the dream of a better city in a global world – reflections on Helen Meller’s ‘Imagining Culture and the City in Planning History’

In the last decade of the nineteenth century, Bombay City was rocked by a series of events that undermined the systems of rule patched together over the course of the preceding century and triggered a crisis of the colonial ‘information order’ on which these were based. Saliently, these developments led to significant changes in the modes of colonial urban governance, in which a new planning agency played a key role. Integral to this shift was a reappraisal, on the part of the colonial state, of its mechanisms of information gathering and the growing recognition of the need for more knowledge about the swiftly expanding city and its rapidly diversifying population. The census of 1901 reflected, to a large extent, these new imperatives of colonial governance.     

Effects of ferric iron on the anaerobic treatment and microbial biodiversity in a coupled microbial electrolysis cell (MEC) – Anaerobic reactor

Adding Fe(III) into a MEC – anaerobic reactor enhanced the degradation of organic matters. To clarify the respective effects of combining Fe(III) dosage and a MEC and Fe(III) dosage only on strengthening anaerobic digestion, three anaerobic reactors were operated in parallel: a MEC – anaerobic reactor with dosing Fe(OH)₃ (R1), an anaerobic reactor with dosing Fe(OH)₃ (R2) and a common anaerobic reactor (R3). With increasing influent COD from 1500 to 4000 mg/L, the COD removal in R1 was maintained at 88.3% under a voltage of 0.8 V, which was higher than that in reactor R2 and R3. When the power was cut off, the COD removal in R1 decreased by 5.9%. The addition of Fe(OH)₃ enhanced both anaerobic digestion and anodic oxidation, resulting in the effective mineralization of volatile fatty acids (VFAs). The reduced Fe(II) combined with electric field resulted more extracellular polymeric substances (EPS) production. Quantitative real – time PCR showed a higher abundance of bacteria in the anodic biofilm and R1. Pyrosequencing and denaturing gradient gel electrophoresis (DGGE) analysis revealed that the dominant bacteria and archaea communities were richer and more abundant in the anode biofilm and R1.     

Characterizing the influence of stress-induced microcracks on the laboratory strength and fracture development in brittle rocks using a finite-discrete element method-micro discrete fracture network FDEM-μDFN approach

Heterogeneity is an inherent component of rock and may be present in different forms including mineral heterogeneity,geometrical heterogeneity,weak grain boundaries and micro-defects.Microcracks are usually observed in crystalline rocks in two forms:natural and stress-induced;the amount of stressinduced microcracking increases with depth and in-situ stress.Laboratory results indicate that the physical properties of rocks such as strength,deformability,P-wave velocity and permeability are influenced by increase in miciocrack intensity.In this study,the finite-discrete element method(FDEM)is used to model microcrack heterogeneity by introducing into a model sample sets of microcracks using the proposed micro discrete fracture network(μDFN) approach.The characteristics of the microcracks required to create μDFN models are obtained through image analyses of thin sections of Lac du Bonnet granite adopted from published literature.A suite of two-dimensional laboratory tests including uniaxial,triaxial compression and Brazilian tests is simulated and the results are compared with laboratory data.The FDEM-μDFN models indicate that micro-heterogeneity has a profound influence on both the mechanical behavior and resultant fracture pattern.An increase in the microcrack intensity leads to a reduction in the strength of the sample and changes the character of the rock strength envelope.Spalling and axial splitting dominate the failure mode at low confinement while shear failure is the dominant failure mode at high confinement.Numerical results from simulated compression tests show that microcracking reduces the cohesive component of strength alone,and the frictional strength component remains unaffected.Results from simulated Brazilian tests show that the tensile strength is influenced by the presence of microcracks,with a reduction in tensile strength as microcrack intensity increases.The importance of microcrack heterogeneity in reproducing a bi-linear or S-shape failure envelope and its effects on the mechanisms leading to spalling damage near an underground opening are also discussed.