Pathologies of Industrialized Buildings Made by Bearing Precast Concrete Panels
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Pathologies of Industrialized Buildings Made by Bearing Precast Concrete Panels. The Case Study of Intervention with the Same Building System at Chiaromonte (27 dwellings), Francavilla in Sinni (27 dwellings) and Lagonegro (36 dwellings) Filiberto Lembo 1 ABSTRACT The research concerns some residential buildings, realized by Potenza's IACP - Autonomous Institute for Popular Houses, by means of a call for bids made in 1984. Work begun the same year but, following the bankrupcy of the firm, occurred in 1986, it was necessary to re-assign it, and by doing so the work has been going on until 1991 for dwellings at Chiaromonte, 1995 for those at Francavilla and 1996 for those at Lagonegro. Since the oneness of the system building in the three different locations, the interest of the research lies in the comparison between environmental features on one side, and on the other the state of preservation and pathologies who are there in the three interventions, with the aim of specifying how much these are connected with local environmental conditions, and how much on the contrary they follow on from defects of building systems of their's one, or from their use. Since to date in many parts buidings are before made subjected to further retrofitting operations, with not completely satisfacting results, it is possible also to express some good practice criteria and workmanlike assessment in order to maintenance and thermal upgrade of this kind of buildings. KEYWORDS Durability & environmental exposition, Pathologies of envelope, Management mistakes, Design mistakes. 1 Faculty of Engineering of the University of Basilicata (Department DAPIT), Potenza, ITALY, [email protected] Filiberto Lembo 1 INTRODUCTION The research, made in 2005-2006 thanks to the Master Thesis work of Eng. Adele Oliveto, coordinated by the writer, concerns some residential building of a public housing program, made by means of a call for bids of Potenza’s IACP – Autonomous Institute for Popular Houses - in 1984, originally designed to achieve 180 housing, but reduced to 90 due to problems of availability of land. The work begun the same year but, following the bankruptcy of the firm, occurred in 1986, it was necessary to re-assign it, and by doing so the work has been going on until 1991 for dwellings at Chiaromonte, 1995 for those at Francavilla and 1996 for those at Lagonegro. The project was drawn up by the Firm successful undertaking of contract, the direction of the work was carried out by technical staff of IACP; for this reason it was possible a direct and continuous control on the quality of the project and works, in the course of their implementation. But such monitoring was not able to ensure good durability and the absence of diseases. 2 DESCRIPTION OF THE BUILDINGS 2.1 Typological characteristics The 90 homes of three interventions in terms of types relate to a single model, which has three apartments to "windmill-type", around the staircase, repeated for a number of floors three to six. The coupling of two mirror image of the model determines unit buildings apparently different. The different size of housing, which are repeated across the column equal, does the rest (see Fig.1). Figure 1. Plan of the basic model "windmill"(left) and specular double (right). The orientation of housing is random, and the same blade mill basic model makes the housing environment (living rooms, bedrooms, kitchens and bathrooms) are pointing in all directions. 2.2 System Building The building system, patented by successful undertaking of contract, the SACEP S.p.A., is called "S.B.S. System" and is characterized by large multitubular bearing precast panels, modular 120 cm, with the possibility of sub 30 cm, and this, for both floors, and walls, that are built on foundations made on site, with piles and continuous beams connection (see Fig.2a-b). The multitubular panels consist of two reinforced concrete walls R 30 with a thickness of 6.5 cm, connected to each other, each 60 cm, by 3.5 cm thick ribs to the panels of the facade, and 9 cm for those of floors. The cavities can be empty or (for facade panels) filled with high density polyurethane foam, thus achieving an average transmittance (according to the manufacturer) U = 0.64 W/m 2 K. Of course, on the two vertical edges, the need to connect the adjacent panels from the static point of view, they have each one vertical cavity of about 30 cm in length for the entire height of the panel, which is completely filled with concrete and reinforcement. It thus forms a thermal bridge 60 cm wide, all over the height of the panels, each time there are joints in line, in the corners to L, and T-junctions with internal bearing walls. A similar thermal bridge occurs horizontally, at the junction between the external chaining between bearing wall and floors. The joints between the panels forming the exterior walls 2 XII DBMC, Porto, PORTUGAL, 2011 Management Mistakes & Durability/Pathologies of Industrialised Buildings are butt joint type, with silicone jointing compound (see Fig.2c). Prefabricated structural components for the flights of stairs, cantilevering from the side panels, balcony railings and crown, complete the system. The roofs are sloping with fake cold ventilated roof with two slopes, with a slope of 8-10%, bitumen sheet coated, in Chiaromonte and Francavilla (see Fig.3), and of 30% in Lagonegro, covered with concrete tiles. Figure 2. Precast panels for bearing walls and floors (a, b) and vertical joint between precast bearing panels for walls and floors (c). Figure 3. Roof sections, Chiaromonte and Francavilla; typical (left), edge (right). 3 GEOGRAPHICAL AND CLIMATIC DATA OF THE THREE LOCATIONS 3.1 Geographical data The municipalities of Lagonegro, Chiaromonte and Francavilla in Sinni are located in the inner part of the mountain of Basilicata, at a latitude between 40°7'29" and 40°4'56" and a longitude 15°46'6 " and 16°12'51". The heights above sea level of municipalities and of places of work are very different between them: they are in Lagonegro 772 m, in Chiaromonte 645 m and in Francavilla 355 m a.s.l. The configuration of the planimetric and altimetric sites where there are the buildings is quite different: at Lagonegro the building is located at the top of the country, along the contours of a slope of 13%, and is oriented with the axis in the sense North-South (see Fig.5); in Chiaromonte buildings are located on the southeast side of the mountain, along the contours of a slope of 25%, and oriented in the direction southwest-northeast (see Fig.6); in Francavilla they are placed at the foot of the hill on which stands the town, north of it, on a slope of 12%, and oriented in the west-east direction (see Fig.7).The insolation of the rooms - as a physical fact of departure - is similar for the three locations, but is strongly influenced by the layout plans of the buildings, which have random orientations, and rooms facing all sides, with therefore strong differences of insolation in the various seasons, for different exposures, and no bioclimatic attention. It should be noted that all the balconies are actually XII DBMC, Porto, PORTUGAL, 2011 3 Filiberto Lembo internal loggias, surrounded on three sides by walls and railings bordered by two small vertical slots filled with 12 cm wide side, and then they determine strong shadows and stop the passage of air, while (including the absence of suitable eaves sprout) are suitable for accumulating rain water blown by the wind, resulting in stagnant water, water penetration, and therefore internal and external stains. Surface/Volume ratio is 3:1 for basic "windmill model ", 2.3:1 for two mirror image e 2.6:1 for the same in Lagonegro (six floors high). 3.2 Climatical data The research, which examined the years 1988 to 1999, showed that, despite being located close together, the three sites have very different climatic conditions, but all with cold winters. Lagonegro is characterized by long, harsh winters with frequent snowfalls and long rainy seasons, and summers are short and cool; Chiaromonte has a humid climate, mild, hot summer's, but quite hard winter' s, with significant rainfall and also (albeit brief) of snow, with large daily temperature ranges, even in summer; Francavilla in Sinni has similar climatic characteristics to the nearby Chiaromonte, but with less rainfall (see Fig.4). Figure 4. Maximum and minimum temperatures in the three sites, 1988-1999 (a), and Quantity of rain in the three sites, 1988-1999 (b). The presence of a meteorological station in Lagonegro allowed to conduct a complete analysis of the wind direction and strength between January 1996 and April 2005. The results can be applied in two other locations, with details that say, plano-altimetric configurations on the sites, which influence their exposure to wind and wet clouds, or rain and snow. The remainder of the climatological data of Chiaromonte was derived from weather stations and Valsinni and Noepoli, and those of the weather station of Francavilla from Agromonte. It appears that in winter the winds are predominantly from West and South-West (between 200° and 240°), with seasonal average intensities ranging between 1.4 m/s and 3 m/s, unless isolated on a weekly basis (especially during the months of January-February), in which the wind speed reached and even exceeded, the 5 m/s, posing a real threat to the proper maintenance of the functionality of the building envelopes. These periods appear to be also the wettest, so the danger of environmental conditions becomes greater.