Evaluation of concrete structures : strength development and fatigue capacity

Abstract: This licentiate thesis consists of four papers. In paper A the development of tensile and compression strength are presented for old concrete railway trough bridges. The compression strength has usually increased 50 to 100% over the years. However the same could not be said for the tensile strength. The so-called Capo-test has been used and an improved formula is presented. In paper B load carrying capacities of cracked as well as un-cracked concrete railway sleepers have been investigated. The cracking is believed to be caused by delayed ettringite formation. Test results, information on how the visual inspection and the classification of damages are performed are presented together with possible failure mechanisms of the fastener when loaded horizontally. In paper C results and analyses are presented from cyclic tensile fatigue tests. The fatigue tests have been compared to a strain criterion proposed by Balázs (1991). In paper D a comparison is made between the Swedish Codes and Eurocode regarding fatigue load for concrete. The results show that the codes are conservative.