One inspection is not enough to estimate durability in building : a simulation study

Decisions about intervention in existing buildings are generally based on information gathered from inspections, as a systematic tool for the identification of some injury in buildings. The goal of this research is to present a simulation study that aims to analyze the accuracy of the resulting estimators and allows the design of an efficient inspection planPeer ReviewedPostprint (author's final draft

IEMAE: mathematics & statistics applied to civil engineering & building

IEMAE (Institut d’Estadística i Matemàtica Aplicada a l’Edificació - Institute of Statistics and Mathematics Applied to the Building Construction) is an academic institution interested in solving Multidisciplinary problems in the civil and building engineering area by using statistics and mathematics disciplinesPostprint (published version

¿Cuán a menudo hay que inspeccionar el patrimonio edificado? Respuesta a partir de un estudio de simulación en durabilidad

La toma de decisiones sobre intervención en obra existente se basa, generalmente, en información recogida a partir de inspecciones, como herramienta sistemática fundamental para la identificación no sólo de los bienes sino también de los indicadores del estado de lesión o deterioro que padezcan los edificios. En este sentido, para llevar a cabo una eficiente tarea preventiva y de mantenimiento, es imprescindible el conocimiento de la distribución de la evolución de las lesiones que se consideren y sobre las que se desee intervenir. Esta información, desafortunadamente, no existe y son pocos los estudios que describan el ciclo de vida de los elementos constructivos en obra, por lo que se debe recurrir a estimadores de durabilidad basados en inspecciones. El principal problema de esta metodología es la gran variabilidad del estimador resultante. En consecuencia, el técnico o investigador se pregunta cuán lejos está la estimación obtenida de la distribución real de los tiempos y cuán precisa es esta estimación para, a partir de ella, llevar a cabo una toma de decisión eficiente respecto de la intervención. Naturalmente, una observación continuada y automática del patrimonio edificado permitiría obtener estimadores más precisos, pero para la mayoría de las lesiones no es posible dicha monitorización y su substitución por un seguimiento continuo basado en inspecciones realizadas por técnicos es inalcanzable por los costos que supone. El objetivo de este trabajo es presentar la investigación que se está llevando a cabo en el Institut d’Estadística i Matemàtica Aplicada a l’Edificació y el Laboratori d’Edificació de la UPC (Barcelona-España) sobre el diseño eficiente de planes de inspección sobre patrimonio edificado. La investigación se plantea en forma de simulación y pretende dar respuesta a las cuestiones planteadas en los párrafos anteriores.Peer ReviewedPostprint (published version

Is one inspection enough to estimate durability in buildings? a simulation study

Decisions about intervention in existing buildings are generally based on information gathered from inspections, as a systematic tool for the identification of some injury in buildings. In this sense, in order to carry out an efficient preventive task and maintenance, knowledge of the evolution of injuries and their distribution are essential. However, this information, unfortunately, does not exist and there are few studies that describe the lifecycle of constructive elements in play; so we must use durability estimators based on inspections. The main problem of this methodology is the high variability of the resulting estimator. The goal of this research is to present a simulation study that aims to analyze this accuracy and allows the design of an efficient inspection plan.Peer ReviewedPostprint (published version

The use of survival analysis techniques in building maintenance

We want, on one hand, to introduce survival analysis techniques for being used in building maintenance and, on the other hand, to apply this methodology for analyzing a large building stock in order to obtain information for maintenance strategies and/or prevention policies. For the time being, building follow-up is based on inspections. Data coming from building inspections are always censored, due to the fact that, at each inspection time, the event of interest is already happened, or not yet. After the analysis of this type of data, durability and hazard functions are derived. The possibilities of this proposal will be illustrated with the analysis of all the buildings façades in Hospitalet de Llobregat, the second most important city in population in Catalonia (Spain).Postprint (author’s final draft

Analysis of construction auctions data in Slovak Public Procurement

The requirement for efficient public spending leads contracting authorities to use electronic reverse auctions (e-RA), a tool that allows achieving financial savings. In this study, we aim to explore the relationships between the different acting e-RA variables and to check for predictive models in order to infer on the savings amount in construction public procurement. Data on real construction auctions in Slovakia were statistically analysed by means of graphics tools, multiple regression analysis, test, and statistics for measuring the association between categorical variables. The results revealed that one should take the type of contract into account when considering the use of e-RA. This research provides several implications for purchasing practitioners in the area of construction procurement, especially with regard to the level of competition in the auction and estimation of savings potential. Presented findings aid managerial decision-making process of e-RA adoption. At the end, recommended future research directions in the investigated area are outlined.Peer ReviewedPostprint (published version

Estimation of survival functions subject to order restrictions

This contribution is framed in, and is part of, the Durabiltiy of Building Facades studies carried out in the last decade in the Institut d’Estadística i Matemàtica Aplicada a l’Edificació and Laboratori d’ Edificació at the Universitat Politècnica de Catalunya. The goal of this presentation is to incorporate in the analysis of the estimation of the durability of building facades respect the severity degrees (low, medium or high) the order of the events of interest. In other words, we will take into account preliminary estimates of the survival probabilities of previous events (e.g. initial severities) as order constraints for the estimation of survival probabilities for subsequent events of interest (e.g. more advanced severities). Standard statistical analyses for this type of interval censored data are usually conducted by using the R statistical software, however it does not include libraries or packages neither for simultaneous estimation nor for the use of order constraints. For this reason, we will use AMPL and the solver SNOPT to implement the Turnbull's estimator with order restrictions, for the estimation of the survival function of each event of interest taking into account the information given by the survival function of some previous event of interest. The proposed methodology solves the inconsistency problem associated with a separate estimation of the respective survival probabilities. As a illustration the methodology will be applied to a simulated dataset. As a theoretical contribution, a conjecture on Turnbull's estimator Theorem under order restrictions will be proposed.Peer ReviewedPostprint (published version

Ordered durability functions estimation for inspection-based data: a computational issue

This contribution is framed in, and is part of, the Durabiltiy of Building Facades studies carried out in the last decade in the Institut d’Estadística i Matemàtica Aplicada a l’Edificació and the Laboratori d’Edificació at the Universitat Politècnica de Catalunya, Spain. The goal of this paper is to incorporate in the analysis of the estimation of the durability of building facades respect the severity degrees (low, medium or high) the order of the events of interest. In other words, we will take into account preliminary estimates of the survival probabilities of previous events (e.g. initial severities) as order constraints for the estimation of survival probabilities for subsequent events of interest (e.g. more advanced severities). Standard statistical analyses for this type of interval censored data are usually conducted by using the R statistical software, however it does not include libraries or packages neither for simultaneous estimation nor for the use of order constraints. For this reason, we will use AMPL language and the solver SNOPT and we will develop and implement a Survival Estimator Algorithm with Restrictions (SEAR), for the estimation of the survival function of each event of interest taking into account the information given by the survival function of some previous event of interest. The proposed methodology solves the inconsistency problem associated with a separate estimation of the respective survival probabilities. Application of the methodology to a simulated dataset, which reproduces a real collection data, will be presented and discussed.Peer ReviewedPostprint (published version

Use of UAVs for technical inspection of buildings within the BRAIN massive inspection platform

Unmanned Aerial Vehicles (UAVs) are becoming more and more popular for use in a various sectors of the economy. The paper presents the results of experiments using a UAV, equipped with a high resolution digital camera, for a visual assessment of technical condition of a building with connection to a big project implemented in Barcelona that required visual data about buildings and their changes with time. Authors try to find out possibilities for the usefulness of digital images obtained from the UAV deck in concrete examples and figure out if they may be complementary to traditional ways used so far in a project called Building Research Analysis and Information Network, which is a platform for analysis to allow strategic decision-making for the maintenance and the sustainability of building stock.Peer ReviewedPostprint (published version

Implementation of a multi-scale predictive system of the degradation of the urban front in Brno, Czech Republic

The unavoidable deterioration of the built urban front in the cities has been increasingly generating a huge environmental impact. From this perspective, it is necessary to develop systematized methods that facilitate strategic maintenance of the facades and which study the variables that can potentially play a significant role in the damage occurrence. Therefore it is convenient to implement analytical methodologies to the decision making process on conservation and sustainability of the built urban front with a macro-scale approach. The BRAIN platform (Building Research Analysis and Information Network) is a Multi-scale Predictive System of the Degradation of the Urban Front. By means of periodic inspections, BRAIN allows analyses of damage progression and prediction of the future affectation, based on survival/reliability statistical models. The aim of this paper is to introduce a preliminary study on the implementation of the Urban Laboratory in the city of Brno, Czech Republic. Results of this primary approach have been displayed and discussed.Peer ReviewedPostprint (published version