Hygrothermal analysis of masonry wall with wool glass interior insulation

ArticleWhen the external appearance of the building is fixed due to heritage requirements the interior thermal insulation is the only possible solution for thermal upgrade of the building envelope. Applying internal insulation to existing buildings is known to pose a challenge in relation to hygrothermal risks, as this can lead to high relative humidity levels, condensation and ultimately, mould growth and decay. The case study building is under historical preservation and therefore this is not allowed to be insulated from outside. The paper describes the hygrothermal assessment of applying internal glass wool insulation and vapour barrier in masonry wall with air gap. In addition to the calculations the condition investigation was also performed. Data loggers measuring temperature and RH were applied during the period of 31.01.2013–16.02.2013. The conclusions were based to theoretical calculations (case study and DIN 4108-3) and practical measurement results based on the data logger values obtained. The calculations showed that glass wool and vapour barrier insulated system were in risk on condensation but the condensed water dries out during summer time. Due to the fact that logger measurements were recorded during the time when inside plastering was still in progress the relative humidity in the room was very high. As a result of calculations it is possible to build this type of wall effectively, but in this case it was not the most reliable way because of ongoing interior fitting

Evaluation of retention stresses of prestressing bars of a concrete ribbed panel from agricultural building after 20 years of service

ArticleIn Estonian agricultural buildings there exist a lot of precast concrete load-bearing structures, which were manufactured in the 1970s and 80s. By now, some of these are rather near for reaching their designed service life. 20 years old prestressed concrete ribbed ceiling panels (type PNS-12) with the dimensions of 6 m (length) by 1.5 m (width) from an existing agricultural building (pigsty) are the subject of current study. The objective of current study was to evaluate the retention stress of prestressing bars (PSBs) of a ribbed panel PNS-12. In other words the purpose was to find out how much of the factory-issued initial prestress was left at the PSBs after 20 years of service. As a novel application in civil engineering strain gauges were applied in the evaluation of retention stress of PSBs in current study. The active strain gauges were glued to the opposite sides of PSBs at the middle-span of the ribbed panel, dummy gauges were glued to the unloaded steel slab. Strain gauges were connected to the half-bridge and measured with strain indicator and recorded. Retention stresses were calculated using the Hooke’s law through the measured strains and elastic modulus of steel. Elastic modulus of PSBs was also measured using the universal testing machine Instron 3369 and software Bluehill 2, based on two standards. The results demonstrated about 20.8% and 10.0% of retention stress of PSBs, respectively. The possible errors created by different aspects in experiment are also discussed

Half-cell potential mapping for corrosion risk evaluation of prestressed concrete ribbed panels from agricultural building after 20 years of service

ArticleCorrosion of steel is a significant problem in prestressed concrete structures as it decreases structural capacity and performance. In this research the 20-year-old prestressed concrete ribbed ceiling panels (of type PNS-12) with dimensions of 6 m (length) by 1.5 m (width) from an existing Estonian agricultural building (pigsty) are studied. The objective is to evaluate the corrosion risk of steel reinforcement of ribbed panels by means of a indirect (non-destructive) method and compare the results with a direct method. The methodology consists of a) non-destructive measurements of half-cell potential and b) comparision with actual condition of steel reinforcement after concrete removal (demolition). Non-destructive measurements were performed on the 10 longitudinal ribs of 5 ribbed panels, respectively. Steel half-cell potential maps were developed based on 900 measurement points recorded by half-cell (Great Dane). After destructive tests the ribbed panels including their longitudinal ribs were demolished and the concrete was carefully removed. The position and condition of steel details was photographed (direct method), which enabled the comparison with potential maps (indirect method). The results demonstrated that in general, half-cell potential maps give a rather good indication on the condition of corroding steel rebars with respect to intact details. Also, half-cell potential maps were found relatively useful in estimating the corrosion risk in the studied precast ribbed panels

Utjecaj namakanja i sušenja u sušioniku na mehanička i fizička svojstva furnirske ploče od brezovine (Betula spp.)

The objective of this study was to explore some of the physical and mechanical properties of 9-layer birch (Betula spp.) plywood with the addition of phenol-formaldehyde glue, in cases in which the cutting edges of the samples are coated with the damp-proof mastic Fibergum, and in case in which they remain unprocessed (uncoated), following a total of ten cycles of soaking/oven-drying. The properties to be determined were the bending strength (BS), modulus of elasticity in bending (MOE), thickness swelling (TS) and restore dimensions (RD), which were tested according to the European standards (EN). A linear-fractional equation and linear relationship were used for the approximation of any change in the physical and mechanical properties of the samples depending upon the number of soaking/oven-drying cycles. It was shown that the values of the properties investigated were most affected by the first soaking and drying cycle. Thereafter, BS and MOE levels decreased smoothly at a low rate, but the values of TS became stabilised. The BS and MOE values for the wet samples with coated cutting edges were higher than when they were uncoated, as the moisture levels in the former case were lower. After the first soaking of the samples with coated cutting edges, the retention values were as follows: BS at 52.8 % and 66.7 % for the major and minor axes, respectively, with the same applying to MOE at 61.9 % and 64.2 %, while TS was at 105.2 %. To clarify the phenomenon that causes a decrease of the properties, the face plies and edge structures of the initial dry samples and of the samples after the first, second and ninth soaking/oven-drying cycles were studied using the X-Ray technique.Cilj ovog istraživanja bio je odrediti neka fizička i mehanička svojstva furnirske ploče od brezovine (Betula spp.) izrađene od devet slojeva furnira i uz dodatak fenol-formaldehidnog ljepila. Uzorci čiji su rubovi premazani za vlagu nepropusnim premazom Fibregum i uzorci s nepremazanim rubovima namakani su i sušeni u sušioniku tijekom deset ciklusa. Prema europskim standardima, ispitivana su ova svojstva ploče: čvrstoća na savijanje, modul elastičnosti, debljinsko bubrenje i vraćanje dimenzija uzoraka. Za aproksimaciju promjena fizičkih i mehaničkih svojstava uzoraka ovisno o broju ciklusa namakanja i sušenja u sušioniku primijenjeni su linearna frakcijska jednadžba i linearni odnos. Utvrđeno je da je na vrijednost ispitivanih svojstava najviše utjecao prvi ciklus namakanja i sušenja. Nakon tog ciklusa namakanja i sušenja čvrstoća na savijanje i modul elastičnosti polako su se smanjivali, dok su se vrijednosti debljinskog bubrenja stabilizirale. Vrijednosti čvrstoće na savijanje i modula elastičnosti vlažnih uzoraka s premazanim rubovima bile su veće nego za uzorke s nepremazanim rubovima zbog manjeg sadržaja vode u uzorcima premazanih rubova. Nakon prvog namakanja uzoraka s premazanim rubovima zadržane su ove vrijednosti: čvrstoća na savijanje na 52,8 i 66,7 % te modul elastičnosti na 61,9 i 64,2 % za glavnu odnosno sporednu os, dok je debljinsko bubrenje iznosilo 105,2 %. Za objašnjenje fenomena smanjenja ispitivanih svojstava, lica slojeva furnira i rubne strukture uzoraka nakon prvoga, drugoga i devetog ciklusa namakanja i sušenja u sušioniku primijenjena je rendgenska metoda

The experimental investigation of the mechanical properties of steel fibre-reinforced concrete according to different testing standards

Steel fibre-reinforced concrete (SFRC) is widely applied in the construction of civil infrastructure projects, including the following: industrial floors, slabs, walls, and foundations. The application of steel fibres in the reinforcement of concrete remarkably improves the postcracking behaviour of such concrete. In order to estimate this property, the energy involved in absorption is measured by using several valid testing standards: EVS-EN 14651:2005, EVS-EN 14488-5:2006, and ASTM C1550-12a. The objective of this study was to carry out a comparable analysis of the results that have been obtained using previously-mentioned standards and to be able to find a more reliable method for the determination of the fracture toughness of SFRC specimens. Experiments were carried out in accordance with the chosen standards. It was concluded that procedure involved in the ASTM standard provides a smaller variability of results with better levels of repeatability, therefore a smaller volume of specimens can be tested in one series in order to achieve reliable results

Energy Retrofits in Multi-family Buildings in North-east Europe: The Impacts on Thermal Conditions

AbstractWe have conducted a project to develop a common protocol for indoor environmental quality (IEQ) assessment and to assess the effects of energy retrofits on IEQ. This paper focuses on thermal comfort, which was first assessed based on 2-month continuous monitoring in 16 multi-family buildings (94 apartments) in Finland and 20 buildings (96 apartments) in Lithuania during heating season before retrofits. In addition, corresponding data after retrofits were available from three buildings (17 apartments) from Finland and seven (30 apartments) from Lithuania. Two data loggers per apartment were placed to evaluate Tw and RHw (warm area), and Tc and RHc (coldest spot). Questionnaire data regarding housing quality and health were collected from the occupants. The results before retrofits indicated high Tw (>23°C) for a large proportion of time in Finnish apartments, whereas opposite trend was observed in Lithuania. After retrofits, proportion of time with high Tw was higher while proportion of apartments with low RHw was lower in Finland, whereas in Lithuania, about one fourth of the apartments had higher Tw and RHw, hence fulfilling the national guidelines. The average absolute humidity was higher after retrofits in both countries, especially in Lithuania (by 15%). Occupant responses indicated improved thermal comfort. Therefore, potential effects of energy retrofits on occupants’ thermal environment and satisfaction were demonstrated, and simply adjusting indoor temperature could help to save energy. Further analysis is needed to include the effects of outdoor conditions, as well as overall IEQ to the assessment

Air Pressure Differences over External Walls in New and Retrofitted Schools and Daycare Centers

Air pressure differences are a key factor in the behavior of building ventilation and air leakages through the building envelope. Field measurements of the air pressure differences over the building envelope were conducted in 24 Finnish municipal service buildings. The measured buildings were mainly schools and daycare centers, of which half were new buildings and half recently retrofitted. All buildings had mechanical ventilation. The measurements were conducted during 2016–2018. The total number of measurement points was 100, and the duration of individual time series varied. According to the results, the mean air pressure difference was within the range of national recommendations (small underpressure indoors) in 81–89% of measurement points, but some cases experienced either strong underpressure or overpressure conditions. In some cases, the air pressure difference showed a clear stepwise constant behavior, while other cases showed larger temporal variation. The conditions varied between different operating situations and the time of year. The study also supports the current recommendation that air pressure difference measurements should be done as continuous measurements of at least one week duration.publishedVersionPeer reviewe

Improving energy efficiency of multi-family buildings, impacts on indoor environmental quality and health

Ilmestynyt suomenkielisenä nimellä Asuinkerrostalojen energiatehokkuuden parantaminen ja sen vaikutukset sisäympäristön laatuun ja terveellisyyteen (Tutkimuksesta tiiviisti 14/2016

Daugiabučių pastatų energinio efektyvumo gerinimas, poveikis vidaus aplinkos kokybei ir sveikatai

Ilmestynyt suomenkielisenä nimellä Asuinkerrostalojen energiatehokkuuden parantaminen ja sen vaikutukset sisäympäristön laatuun ja terveellisyyteen (Tutkimuksesta tiiviisti 14/2016