Crack control of concrete structures in special cases
Kattilakoski, Jaakko (2013)
2013
Rakennustekniikan koulutusohjelma
Tuotantotalouden ja rakentamisen tiedekunta - Faculty of Business and Built Environment
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Hyväksymispäivämäärä
2013-12-04
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201312191505
https://urn.fi/URN:NBN:fi:tty-201312191505
Tiivistelmä
In this study, cracking and crack control of concrete structures is explored. Main focus of this study is put on controlling cracking behavior in cases that can be considered as special ones. That comprises massive concrete structures with heavy reinforcement and thick concrete covers that are present e.g. in nuclear power structures.
It was noted in the thesis, that in special cases cracking can be controlled with proper curing, casting arrangements, limiting of compressive stress of concrete and tensile stress of steel, right selection and arrangement of reinforcement, surface reinforcement, transversal reinforcement in the anchorage zone and in case of massive concrete structures minimizing the temperature difference in the structure.
The primary goal of this study is to explore and clarify, whether it is possible to control cracking in special cases by calculating crack widths according to EC2, when concrete cover is thick and surface reinforcement cannot be used. In addition the reliability of calculated crack widths was explored in such situations. This was conducted by calculating crack widths for a sample structure, and comparing the results with the experimental test results found in literature. For comparison crack widths were calculated not only according to EC2 but also three different available methods were used.
The crack width calculations proved that with thick concrete covers and heavy reinforcement calculated crack widths increased significantly. Comparison of calculated results with experimental tests showed relatively good relation between predicted and real crack widths in normal case, but, in special case calculated crack widths seemed to be greater than experimental widths. On the basis of this study crack width calculation according to EC2 will not be suitable for cases with thick concrete covers and heavy reinforcement without distinct lowering of steel stress, even though it was proven that real crack widths will likely remain lower than predicted ones.
It was noted in the thesis, that in special cases cracking can be controlled with proper curing, casting arrangements, limiting of compressive stress of concrete and tensile stress of steel, right selection and arrangement of reinforcement, surface reinforcement, transversal reinforcement in the anchorage zone and in case of massive concrete structures minimizing the temperature difference in the structure.
The primary goal of this study is to explore and clarify, whether it is possible to control cracking in special cases by calculating crack widths according to EC2, when concrete cover is thick and surface reinforcement cannot be used. In addition the reliability of calculated crack widths was explored in such situations. This was conducted by calculating crack widths for a sample structure, and comparing the results with the experimental test results found in literature. For comparison crack widths were calculated not only according to EC2 but also three different available methods were used.
The crack width calculations proved that with thick concrete covers and heavy reinforcement calculated crack widths increased significantly. Comparison of calculated results with experimental tests showed relatively good relation between predicted and real crack widths in normal case, but, in special case calculated crack widths seemed to be greater than experimental widths. On the basis of this study crack width calculation according to EC2 will not be suitable for cases with thick concrete covers and heavy reinforcement without distinct lowering of steel stress, even though it was proven that real crack widths will likely remain lower than predicted ones.