Browsing by Author "Piironen, Jukka"
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Item Conceptual structural design of a reactor tower of reinforced concrete(2010) Jauhiainen, Lena; Piironen, Jukka; Insinööritieteiden ja arkkitehtuurin tiedekunta; Insinööritieteiden korkeakoulu; School of Engineering; Puttonen, JariThe purpose of the studied reactor tower is to function as a part of a hydrometallurgical process. The tower is 70 meters high and the middle part of the load bearing structure is a 42 meter high cylindrical shell. The environmental and process circumstances that surround the shell structure are challenging. It has to, among other things, withstand the wind pressure, the high temperature (104 °C) and aggressive (pH 1) solution inside the reactor as well as the hydrostatic pressure of the solution (density 1400 kg/m3). The aim of this thesis is to study the parameters that influence the dimensioning of the middle part and to make a preliminary assessment of the structure. This thesis includes a literature review and a part of structural dimensioning of the cylindrical shell. In the literature review there are studied structures and production methods that are used in high reinforced concrete structures, such as silos, water towers and cooling towers. The part of structural dimensioning includes an analytical part and a part of Finite Element Method analysis with Abaqus/CAE software. The cylindrical shell was studied with the help of two different types of wall structures: a concrete cross-section with an inner protective cover and a laminate-concrete-laminate composite cross-section. The parameters that where studied are: the strength class of the concrete, pre-stressing, and the use of insulation, the thickness of the cross-section and the boundary conditions of the lower edge. The calculations, that where made proved that the temperature load is the dominant load. It is possible to influence on the cross-section size and amount of reinforcement by reducing the temperature load. Parameters that reduce temperature stress are the use of insulation that reduces the temperature differences and making the wall more flexible by reduction of the cross-section thickness. Neither had the use of a high strength concrete nor the different boundary conditions a notably effect on the amount of reinforcement. In the outer parts of the cross-section it was not possible to compensate the tension stress caused by the temperature load by pre-stressing the structure with ordinary methods. Both types of wall structures are possible to execute if it is possible to ensure the collaboration of the materials. In future research the following items should especially be considered: the reduction of the temperature load and the interaction between the materials. The following items should also be taken into account in future research: optimization of the construction method of the tower and properties of laminate and consideration of the whole process from filling of the reactor to its emptying including special situations.Item Developing a Computerized Aging Management System for Concrete Structures in Finnish Nuclear Power Plants(EDP Sciences, 2013) Al-Neshawy, Fahim; Piironen, Jukka; Sistonen, Esko; Vesikari, Erkki; Tuomisto, Mikko; Hradil, Petr; Ferreira, Miguel; Department of Civil and Structural Engineering; Department of Civil Engineering; L’Hostis, V.; Gens, R.Finland has four nuclear reactors units in two power plants. The first unit started operation in 1977 and in the early 1980's all four units were in use. During the last few years the aging management of the Nuclear Power Plant's (NPP) concrete structures has grown an important issue because the existing structures are reaching the end of their licensed operating lifetime (about 40 years). Therefore the nuclear power companies are developing aging management systems to avoid premature degradation of NPP facilities and to be able to extend their operating lifetime. This paper is about the development of a computerized ageing management system for the nuclear power plants concrete structures. The computerized ageing management system is built upon central database and implementation applications. It will assist the personnel of power companies to implement the aging management activities at different phases of the lifetime of a power plant. It will provide systematic methods for planning, surveillance, inspection, monitoring, condition assessment, maintenance and repair of structures.Item Different Facade Repairs and Their Risks and Advantages(2001) Kaustinen, Raila; Piironen, Jukka; Rakennus- ja ympäristötekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Huovinen, SeppoItem The effect of cracking on chloride diffusion in concrete(2010) Sillanpää, Markku; Piironen, Jukka; Insinööritieteiden ja arkkitehtuurin tiedekunta; Insinööritieteiden korkeakoulu; School of Engineering; Sistonen, EskoThe major degradation mechanism in concrete structures is the corrosion of the reinforcements as a result of chloride penetration. The corrosion reduces serviceability and safety because of the cracking and spalling of the concrete and the loss of the steel cross section. The current approach aims at postponing the initiation of corrosion until the end of the required service life with a predetermined reliability, based on the simplified modelling of transport in uncracked concrete and the testing of laboratory samples for chloride diffusion. The main focus of this research was on investigating non-steady-state chloride migration in cracked and uncracked concrete. Another aim was to compare the non-steady-state migration results in cracked and uncracked concrete and check if the test method described in the NT BUILD 492 method can be used for cracked concrete. The Nordtest Method NT BUILD 492 describes the method used to determine the chloride migration coefficient in concrete. The experiment is a non-steady -state test with an external power supply to carry chloride ions to concrete. In the experimental test cracked and uncracked specimens from eight different concretes are used. The electrical potential forces the chloride ions outside to migrate into the specimen. The depth of the chloride penetration can then be measured by spraying silver nitrate solution onto the freshly split surfaces. The migration coefficient for cracked and uncracked concrete is calculated from the measurements. The experimental results are compared with numerical simulation. The numerical simulation is performed with the Comsol Multiphysics software. The baseline for the numerical simulation values was the experimental test results. The results are used to evolve better models of chloride penetration in cracked concrete and possibly in the future to create better service life models. The cracks are fast routes to drive chlorides deep into the concrete structure. As the experimental tests and results of the numerical calculations show, this must not be undervalued in chloride penetration estimations.Item Esimerkkirakenteen kunnonhallinta ja elinkaarianalyysit(2009) Jalonen, Jarno; Piironen, Jukka; Insinööritieteiden ja arkkitehtuurin tiedekunta; Aalto, JukkaItem Experimental and numerical study of a shear wall of reinforced concrete(2015-11-23) Khan, Ghaffar; Piironen, Jukka; Insinööritieteiden korkeakoulu; Puttonen, JariReinforced concrete shear walls are popular structural members with a particular importance in seismically active regions. This study aims to analyze a reinforced concrete shear wall by a finite element software suite using a material model based on damage plasticity and compare the numerical results with experimentally observed behavior. A reinforced concrete shear wall designed for this particular study has been tested in the laboratory using cyclic loads. The corresponding damage was evaluated after each load increment using the damping ratios computed using the log-decrement method. The wall was modeled and analyzed by a finite element software suite ABAQUS using ABAQUS/ Explicit analysis. In the numerical analysis, concrete has been modeled using the Concrete Damage Plasticity (CDP) material model and reinforcing steel by a bilinear stress-strain relation. The two materials were combined to represent reinforced concrete. Properties of the CDP material model have been derived based on the literature. A material model was first verified using bending tests on reinforced concrete beams with different load and support conditions and was then extended to modeling the shear wall in the present study. Results from laboratory testing of the shear wall and numerical analyses were compared and discussed. The CDP material model provides a good perspective of the cracking pattern and failure load of the structure. However, quantitative results could not be verified due to accidental dynamic loads during laboratory testing. They caused numerous hairline cracks in the test structure and may have affected the measured values in the strain transducers. However, both approaches gave a similar type of response in terms of strain increase within elastic range and crack opening upon the post-elastic range. Discrepancies and shortcomings between the numerical and experimental results were identified and suggestions presented for improving numerical modeling. Also, recommendations were given for future research on the topic.Item Impact of interacting deterioration phenomena on concrete(2012) Nordqvist, Cecilia; Piironen, Jukka; Rakennustekniikan laitos; Insinööritieteiden korkeakoulu; School of Engineering; Sistonen, EskoConcrete structures are constantly exposed to various deteriorating phenomena, most of which are associated with different environmental or weather conditions. The deteriorating impact of these phenomena mainly results in reduced service lives of the concrete structures. Under ordinary circumstances, the vast majority of all concrete structures become exposed to a combination of deteriorating attacks. These attacks often occur concurrently within the same environment, and therefore, the effect of the combined loads must be taken into consideration in order to provide more accurate durability and service life calculations. The main objective of this research was to investigate the impact of the interaction between different deterioration parameters on concrete. The research focused on pairing three forms of deterioration: frost deterioration, carbonation and chloride penetration. Another aim was to investigate whether the outcome of the test results is affected by mix proportion and concrete properties, such as water/cement ratio, amount of air and usage of various binding materials. Experimental testing was performed to numerous test specimens, which were cast from different types of concretes and mortars. The test equipment used for the experimental testing included the so-called PROOVE'it© rapid chloride migration (RCM) test equipment by Germann Instruments. The equipment is designed for the ASTM C 1202-97 or AASTHO T 277-831 test methods, which are similar to the NT BUILD 492 method used in this research. Additionally, several climate chambers were utilized in order to produce the right exposure climate for the test specimens. These included weather rooms with varying relative humidity (RH) of 65 % and 95 %, in addition to chambers producing repeated freezing and thawing cycles and constant CO2-levels for exposure to accelerated carbonation. According to the results of the experimental testing, the increased level of internal deterioration (RDM) increased both carbonation and chloride migration surprisingly little. A possible reason for this could be the direction of the internal deterioration. It can be assumed, that the frost deterioration caused horizontal cracking in the specimens, instead of vertical cracking. The test results also indicated that exposure to carbonation prior to chloride ingress remarkably reduced the ability to resist chloride migration (Dnssm) of all mortars. Additionally, the results indicate that the concrete and mortar types used in the research were perhaps a bit too durable.Item Kohtuullisesti kohonneen lämpötilan pitkäaikaisvaikutukset betonin ominaisuuksiin(2013-05-08) Turunen, Mikko; Piironen, Jukka; Insinööritieteiden korkeakoulu; Pakanen, JoukoItem Long-time durability of a hot-dip galvanized coating of a steel combine deck in a open parking building(1998) Piironen, Jukka; Lydman, Mika; Rakennus- ja yhdyskuntatekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Kanerva, PekkaItem Seismic analysis of a liquid-filled tower-type shell structure(2014-03-24) Matilainen, Jussi; Piironen, Jukka; Insinööritieteiden korkeakoulu; Puttonen, JariThe purpose of this study is to introduce a numerical technique for analyzing a liquid-filled shell structure under EN 1998 compliant earthquake ground motions. Prescriptions of the EN 1998 to the representation of earthquake ground motion as accelerograms are explained. Accelerograms representing the ground motion are generated by matching recorded accelerograms to a response spectrum and, alternatively, artificial accelerograms are generated for reference.For the numerical simulations, structures are treated with traditional Lagrangian formulation while the liquid is represented by arbitrary Lagrangian-Eulerian (ALE) formulation. Governing equations of the ALE formulation, the Mie-Grüneisen equation of state representing the fluid and a solving strategy based on operator splitting are introduced. Euler-Lagrange coupling algorithm is employed to achieve the fluid-structure interaction. Coupling mechanism based on a spring-damper system and its possible drawbacks are illustrated. The numerical method is verified with three examples based on previous research papers which demonstrate its reliability. An industrial-sized liquidfilled tower subjected to both the matched and artificial tri-axial accelerograms is analyzed. Horizontal deflections of both the liquid-filled and empty towers due to the matched and artificial accelerograms are determined. The liquid-fill is also taken into account by simply adding the liquid mass to the mass of the empty tower in order to evaluate how much the liquid motion affects the structural response. As a result of this study, information is gained from both the effect of ground motion selection process and liquid fill on the structural response of the tower. Vertical ground motion had no effect on the response because the tower as a vertical cantilever does not possess any modes of importance in the vertical direction. The use of artificial accelerograms resulted in much larger deflections in the case of an empty tower and moderately larger deflections in the case of an added mass model than the use of matched accelerograms. This is attributed to the assumption that artificial accelerograms carry higher frequency content than the matched accelerograms. In the case of liquid-filled tower, the source of an accelerogram had a negligible effect on the response which demonstrates that the liquid fill increases the fundamental period compared to the added mass model. The liquid fill was noted to affect the structural response not only by its mass but also by its motion. Analyses conducted with the empty tower and the added mass model resulted in underestimation of deflections by 37.1 % and overestimation of deflections by 35.1 %, respectively. In conclusion, this study demonstrates that the fluid-structure interaction significantly affects the dynamic behavior of a structure during a seismic event.Item Structural optimization of middle part of reinforced concrete reactor tower in mining industry(2011) Al-Hello, Aid Abdul; Piironen, Jukka; Rakennustekniikan laitos; Insinööritieteiden korkeakoulu; School of Engineering; Puttonen, JariThe purpose of researching a new type of reaction tower is to make the utilization of the poor ores more efficient by improve hydrometallurgical processes. This research is now in the development stage. The total height of the reactor is planned to be about 70 meters and it consists of lower part, arm and upper part. The arm is planned to be about 42 meter high cylindrical shell. The greatest load challenge on the arm is the temperature difference between the internal and external surfaces of the wall structure. Internal temperature is +104°C and the lowest external temperature is assumed to be -20°C. The arm has to, among other things; withstand the wind pressure, acidity of the solution inside the reactor as well as the hydrostatic pressure of the solution. Thus, the aim of this thesis is to find an optimal structure for the wall of the tower arm in particular with the response of temperature load. The acidity (PH) of the solution is a class 1 and the density of it is 1500 kg/m3. It has been found in the previous study (Lena Jauhiainen, 2010), that the heat load is the dominant load for examined structure types. The literature part of this study reviews the heat transfer mechanisms and the temperature distributions in the multi-layer cylindrical structures. Heat transfer was studied in both steady state condition and transient condition. Transient condition is generated during the reaction start-up or shutdown. The middle part dimensioning calculations contains the manual calculations and Abaqus program calculations, which based on the finite element method. The parameters of this study are to investigate the need of internal and external thermal insulations and the thicknesses of the structure layers. As a result of this study the optimal wall structure consist of four layers. The layers are as follows (from inner to outer layer): 50 mm reinforced plastic, 50 mm mineral wool, pre-stressed reinforced concrete and 50 mm polyurethane. The results of the calculations conclude that both the internal and external thermal insulations are necessary to keep the temperature of the concrete layer within the acceptable range (<= +65°C), and the temperature difference between the concrete layer surfaces, which cause temperature stress, low. It also concludes that the use of tension cables compensates the tension stresses on the external surface of the concrete layer. The further researches should pay attention to the interaction between the material layers of this structure, constructability and implementation of pre-stressing.Item Structural optimization of tower-like reactor of reinforced concrete in mining industry(2013) Salimi, Yadollah; Piironen, Jukka; Rakennustekniikan laitos; Insinööritieteiden korkeakoulu; School of Engineering; Puttonen, JariThe aim of the studied tower-like reactor is to utilize poor ores by improving hydrometallurgical processes. The reactor is about 70 meters high and it consists of three parts; lower tank, shaft and upper tank. The main aim of this thesis is to optimize the structures of the lower tank under hydrostatic and temperature loads. Also the axisymmetric shaft of the reactor with free and fixed bottom and the joint between the shaft and lower tank are studied. The greatest load challenge is hydrostatic pressure and temperature load in the lower tank. The literature part is a review over the calculations of axisymmetric shells. The structural optimization of the shaft is defined and also studied as a reinforced and a pre-stressed structure. The shape of the lower tank is defined as well as its structural optimization is carried out. The lower tank is divided into two parts: lower part and upper part. An axisymmetric pre-stressed method is applied on upper part. The joint is strengthened with a box-shaped concrete structure against hydrostatic pressure. The joint is also studied both as composite and steel structure. The analysis was carried out with Abaqus software, According to heat transfer calculations the internal mineral wool in the shaft should be at least 100 mm thick in order to keep the temperature of the concrete layer within the acceptable range (<=+65 °C). The concrete layer of the shaft with a fixed bottom will be exposed to high tensions if the temperature of the structure is -20 °C. Tensions caused by temperature load could be reduced with different structural solutions in both parts of the lower tank. Based on the study the optimized structure in the lower part is: 50 mm reinforced plastic, 25 mm mineral wool, 125 mm polyurethane, concrete layer and 100 mm polyurethane and in the upper part: 50 mm reinforced plastic, 150 mm mineral wool, 700 mm pre-stressed concrete layer and 100 mm polyurethane. The internal and external insulations are necessary to keep the temperature of the concrete layer within the acceptable range. The tension in the upper part may be nullified by the applied pre-stressing method, Hydrostatic pressure is the largest load loading the joint and the stresses caused by it cannot be reduced efficiently with strengthening. Only a small portion of the steel could be utilized if the joint is designed as a composite structure of steel and concrete. If the load in the joint area is carried out by a steel structure its thickness should be at least 150 mm. However, in future a more exact study should be made for the joint area and for the distribution of temperatures around structural discontinuities. Also the interaction between the material layers of the structures, constructability and implementation of pre-stressing should be paid attention to.Item Teräsbetonisen merivesirakenteen vauriomekanismit ja niiden yhteisvaikutukset(2010) Salo, Mikko Johannes; Piironen, Jukka; Kari, Olli-Pekka; Insinööritieteiden ja arkkitehtuurin tiedekunta; Vahala, RikuItem Thermal and strength analysis of a tower structure made of concrete and fiber reinforced plastic(2013) Vainio, Juha; Pärnänen, Tuomas; Piironen, Jukka; Insinööritieteiden korkeakoulu; Insinööritieteiden korkeakoulu; School of Engineering; Saarela, OlliApproximately 70 meters high reactor tower is studied in this research. The aim of the thesis was to find feasible solutions for the connection of the primary concrete structure and inner fiber reinforced plastic (FRP) shell. In the literature review different methods for bonding concrete and FRP members are introduced. Three proposed structures for the connection of the reactor structures are stiff insulation, ring stiffener and dowel support. The second objective was to numerically evaluate how proposed structures behave under loading and how structural and material parameters affect the loading of structural members. The tower structure is loaded by hydrostatic pressure, deadweight of the structure and thermal loading. The analysis was conducted using finite element software Abaqus. Based on the results two feasible structures were found which are stiff insulation and ring stiffener. The recommended solution is stiff insulation. Main parameters affecting strains in the FRP layer are Young's modulus and thickness of the insulation material. Thickness of the insulation layer and long term properties in elevated temperatures of insulation materials need further investigation.Item Tilaelementtien käyttö ja mahdollisuudet asuinkerrostalojen saneeraamisessa(2010) Hartonen, Miia; Piironen, Jukka; Insinööritieteiden ja arkkitehtuurin tiedekunta; Vahala, Riku
