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A platform for research: civil engineering, architecture and urbanism
Assessment of fatigue resistance and strength in existing concrete structures
During the last few decades, it has become more and more important to assess, maintain and strengthen structures like bridges, dams and buildings. This is mainly due to the fact that: (a) many structures are getting old and many have started to deteriorate, (b) there is sometimes a need to increase the load carrying capacity of an existing structure due to e.g. a demand for higher loads or (c) the cost to build new infrastructure is often higher than to repair/strengthen existing structures. Therefore it is of great interest to find methods to evaluate existing concrete structures in an efficient way. In this thesis parameters influencing the evaluation process have been investigated and analysed and the results are presented in the appended papers. Below, findings from the main areas are presented. The development and variation of compressive and tensile strength of concrete are presented for old concrete bridges in Sweden. The mean increase in concrete compressive strength was about 70% for twenty bridges built during 1931-1962 (a rather high dispersion must be taken into consideration). The increase is related to the original 28-day concrete compressive strength which varied between 18 and 51 MPa. The compressive strength within a typical reinforced railway concrete trough bridge was approximately 15% higher in the longitudinal beams than in the bottom slab (measured on drilled cores). A pullout test method, the Capo-test, has been examined as an alternative to drilled cores to determine the in-place concrete compressive strength. A strength relationship is proposed between the compressive strength of a drilled core with the diameter and the height of about 100 mm, fcore, and the pullout force, F, from the Capo-test. A probabilistic approach has been proposed for the evaluation of the shear force fatigue capacity of a concrete bridge slab. In the reliability analysis three different combinations of shear and fatigue models have been compared. The models have been used to determine the safety index ¦Â (and the ...
Assessment of fatigue resistance and strength in existing concrete structures
During the last few decades, it has become more and more important to assess, maintain and strengthen structures like bridges, dams and buildings. This is mainly due to the fact that: (a) many structures are getting old and many have started to deteriorate, (b) there is sometimes a need to increase the load carrying capacity of an existing structure due to e.g. a demand for higher loads or (c) the cost to build new infrastructure is often higher than to repair/strengthen existing structures. Therefore it is of great interest to find methods to evaluate existing concrete structures in an efficient way. In this thesis parameters influencing the evaluation process have been investigated and analysed and the results are presented in the appended papers. Below, findings from the main areas are presented. The development and variation of compressive and tensile strength of concrete are presented for old concrete bridges in Sweden. The mean increase in concrete compressive strength was about 70% for twenty bridges built during 1931-1962 (a rather high dispersion must be taken into consideration). The increase is related to the original 28-day concrete compressive strength which varied between 18 and 51 MPa. The compressive strength within a typical reinforced railway concrete trough bridge was approximately 15% higher in the longitudinal beams than in the bottom slab (measured on drilled cores). A pullout test method, the Capo-test, has been examined as an alternative to drilled cores to determine the in-place concrete compressive strength. A strength relationship is proposed between the compressive strength of a drilled core with the diameter and the height of about 100 mm, fcore, and the pullout force, F, from the Capo-test. A probabilistic approach has been proposed for the evaluation of the shear force fatigue capacity of a concrete bridge slab. In the reliability analysis three different combinations of shear and fatigue models have been compared. The models have been used to determine the safety index ¦Â (and the ...
Assessment of fatigue resistance and strength in existing concrete structures
Thun, Håkan (author)
2006-01-01
2006:65
Theses
Electronic Resource
English
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