Backanalysis of measured movements in ageing tunnels

The paper describes a procedure to perform backanalysis in a systematic manner in the context of ageing tunnels. Basically the input data include information on relative displacements or deformations of specific points in the lining of a tunnel exhibiting long term movements and the objective of the procedure is to identify a set of parameters that characterize the surrounding soil and the lining properties. Any damage in the infrastructure should give a change in those parameters identified. The analysis should be able to obtain useful information for the manager of the tunnel, in terms of maintenance, repair of some sections, warning in case of danger, etc. The paper presents the basic theory of parameter identification and an application to the backanalysis of a tunnel section from London Underground, where some measurements of rotation of lining segments are available

Backanalysis of preloading

The paper presents the application of a backanalysis methodology to the inverse analysis of preloading soft clays. The methodology is based on an appropriate selection of the objective function and it uses a novel adaptive genetic algorithm approach to solve the resulting optimization problem. The methodology is applied first to a synthetic example followed by an application to an intensely instrumented preload test. The selected observations are the evolution along time of displacements and pore water pressures. The key parameters to be identified are those with major influence on the results: compressibility and permeability of the soil. It is shown that the confidence in parameter estimation varies significantly depending on the time at which the observations are considered and the type of them (displacements vs. pore water pressure). The possibility of extrapolating early results to later stages of the preloading is also explored. The usefulness of the method in engineering problems is demonstrated by the application to a preloading performed to improve the soft ground of the Water Treatment Plant located in the Llobregat delta near Barcelona.Postprint (published version

Aging study of plastics to be used as Radiative cooling wind-shields for night-time radiative cooling - Polypropylene as an alternative to polyethylene.

Polyethylene has widely been used in radiative cooling applications because of high transmittance values in the atmospheric window. However, it presents optical and mechanical degradation when exposed to environmental conditions and must be replaced every few months. This paper aims to find an alternative to polyethylene to be used in a unique device, the Radiative Collector and Emitter (RCE), that combines solar collection and night-time radiative cooling. The aging evolution analysis of five cheap and market available plastic films (two low density polyethylene, one high density polyethylene, one polypropylene, and one fluorinated ethylene propylene) exposed to environmental conditions was performed. FT-IR spectra and mechanical traction tests were performed before and after 90 days of exposure to the environment. Results confirm that polyethylene undergoes a degradation process both when it is covered by a glass and when it is uncovered. However, it maintains high average transmittance values in the atmospheric window. Polypropylene has average transmittance values slightly lower than polyethylene, but its aging behaviour is better since no oxidative processes are detected when the material is covered with glass. For all this, PP-35 is an interesting candidate for night-time radiative cooling wind-shields.This publication is part of the grant RTI2018-097669-A-I00, funded by MCIN/AEI/10.13039/ 501100011033/ and by “ERDF A way of making Europe”. This publication is part of the grant PID2021- 126643OB-I00, funded by MCIN/AEI/10.13039/501100011033/ and by “ERDF A way of making Europe”. The authors would like to thank Generalitat de Catalunya for the project grant given to their research group (2017 SGR 659)

Thermal loads inside buildings with phase change materials: Experimental results

AbstractNowadays, European policies are promoting low energy buildings because of the high amount of energy consumption of the building sector. Phase change materials (PCM) have been studied in building implementation as a passive system to reduce the energy demand. Based in the experience obtained in the experimental set-up of Puigverd de Lleida (Spain), this paper pretends to analyze experimentally the PCM performance in a scenario with internal thermal gains. The experiments were done in three different cubicles with the same internal dimensions. The selection of the constructive systems used in these three cubicles allows the authors to evaluate the impact of using PCM in a typical Mediterranean building. A domestic heat pump for summer and an electric radiator for winter were installed to control the internal temperature of the cubicles. The results of summer period experiments show that the PCM cubicle stored the heat produced by the internal loads limiting the heat dissipation to the outer environment. Therefore, the energy consumed by the HVAC system of the PCM cubicle during the cooling period is higher than that of the other cubicles that dissipated the thermal loads according to the thermal resistance of their envelopes. Therefore, the PCM selection should take into account not only the comfort temperature but also the activity and functionality of the building

New green facades as passive systems for energy savings on buildings

2013 ISES Solar World CongressThe new technologies of plants integration on buildings offer new possibilities from the sustainable construction point of view, especially in energy savings. In previous studies the great capacity of double-skin green facade or green screen to intercept solar radiation was confirmed, observing differences up to 18 °C in surface temperatures between sunny and shade areas on the wall of the building. The experiment presented here consists of two identical house-like cubicles (3 x 3 x 3 m) located in Puigverd de Lleida, Spain. The only difference between the two cubicles is the double-skin green facade installed in one of them. In a first step only the South wall was covered by a provisional green facade. As the results from first experiment were positive with interesting low electrical energy consumptions when only the 50% of the South wall was covered by plants, a new stable green facade was built covering the South, East and West facades by a deciduous specie well adapted to the Mediterranean Continental climate. With this study the confirmation of the good operation of green facades made with deciduous species as passive system for energy savings in buildings is expected to be characterized.The work was partially funded by the Spanish government (project ENE2011-28269-C03-02 and ULLE10-4E-1305). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2009 SGR 534), and to City Hall of Puigverd de Lleida

Green roofs as passive system for energy savings when using rubber crumbs as drainage layer

1st International Conference on Solar Heating and Coolingfor Buildings and Industry (SHC 2012)This study is another step of a long-term work in order to study the thermal behaviour of extensive green roofs in dry Mediterranean Continental climate. In this paper there are two main goals. On one hand, the possibility of using rubber crumbs as a drainage layer in green roofs, substituting the porous stone materials used in some commercial solutions is studied. On the other hand, new data concerning the use of green roofs as passive system for energy savings in dry Mediterranean Continental climate is provided. First results correspond to summer 2011, when the roof was just planted and the irrigation system installed. The vegetation cover in those days was about 20% of the roof surface. With an internal set-point of 24 °C first results show an improvement in energy consumption with respect to the reference cubicle. New data will be recorded during 2012 when the vegetation has developed and it is expected better results than in 2011.This work was partially funded by the Spanish government (ENE2011-28269-C03-02) and the European Union (COST Action COST TU0802), in collaboration with the companies Gestión Medioambiental de Neumáticos S.L (Polígon Industrial Piverd s/n, Maials.) and Soprema. The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2009 SGR 534)