Strengthening of pre-stressed I-roof-beams with external post-tension

This paper handles strengthening of pre-stressed I-beams.

During last year's, in Finland, many buildings were built using pre-stressed pre-fab concrete beams. Trying to reach very low cross-sections, concrete industry forgot to check the compression in concrete. This caused several problems. To solve these problems and create a system to strengthen these beams, Tampere University of Technology planned a testing pattern of specimens with span of 15 meters. Test samples were loaded until brake.

At the same time a post-tensioning technique was used to strengthen these beams. The study is handling the strengthening system and influence of its geometric variation. A simple formula to estimate the influence of systems geometric variation was developed according calculation results.

Results showed that developed technique is very effective and the formula gives reliable results.