The objective of the current study is to investigate and evaluate the flexural behavior of the continuity connection of precast prestressed concrete beams in negative bending when the tendons are located at the compression side. The experimental program included four T-shaped composite cantilever beams which were loaded up to failure. The main variable of the tests was the amount of prestress force of the connected precast beams. The reinforcement ratio of continuity connection was high. The ultimate flexural capacities and moment-curvature relations were calculated theoretically. A comparison was then carried out between both the experimental and theoretical results. These experiments revealed that prestress force did not influence the ultimate hogging moment capacity of the continuity connection, but it had an effect on its soffit's compression cracking and spalling of the concrete cover before failure. This study also indicated that confinement of the concrete had a massive influence on the connection's behavior, and it increased both its negative moment capacity and ductility.

Structural ductility in the case of plastic hinges forming close to a lap splice has been an open issue with the revision process of the next version of Eurocode EC2 concerning reinforced‐concrete structures. This research has provided experimental evidence by the large experimental campaign for the background for revision of the Eurocode EC2. Within this context, 38 specimens were tested in four‐point bending, with the longitudinal bars either lap‐spliced (partly or fully), or un‐spliced (for reference). The tests were carried out involving the variation of the bar diameter (12, 16, 20, and 25 mm), and the lap length (20–60 times the bar diameter). The main result is the sizeable enhancement of the structural ductility brought in by the extension of the lap length in excess of the length required by the yielding of the longitudinal bars. Based on these findings, a preliminary model is developed to describe the bond‐stress profiles in lap splices, after the yielding of the bars.

The compressive strength of concrete is highly influenced by the properties of test specimens, such as size and moisture content. This paper presents the results of compression tests on more than 650 test specimens made with four different concrete types, which are mainly air‐entrained. The differences in compressive strength between different types of concrete specimens were investigated with similar compaction and curing conditions. The tested specimens were 50 × 50 mm, 80 × 80 mm, 100 × 100 mm, and 150 × 300 mm cores, which were drilled from the cast cylinders. In addition, 150‐mm cubes, 100 × 100 mm and 150 × 300 mm cylinders were included in the test programme. The ratios of compressive strength between different core sizes and core strength comparability to the cast specimens were found to be strongly dependent on the concrete type. Drilling was found to have a clear weakening effect on obtained compressive strength. The conversion factors for the compressive strength between the core and the same size cast specimen was proposed for 150 × 300 mm and 100 × 100 mm specimen sizes.

<p>This paper deals with testing of pre-stressed I-beams, the behaviour of the beams under loading, strengthening methods and their function.</p> <p>In the near history in Finland large commercial buildings have been built using pre-stressed pre-fabricated beams. The cost efficiency has led to designing very slender beams with higher pre-stress forces. This has caused problems in pre-stressed beams around Finland. Damages has been so se-vere that immediate repair of the beams has been necessary in some cases. Tampere University of Technology helped develop and tested these strengthening methods.</p> <p>The results of the tests led to development of a formula that estimates the beam’s extra capacity after post-tensioned strengthening method.</p>

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