Effects of the position of confining transverse links on lap strength

The article presents the results of an experimental campaign to investigate the effect of the position of transverse links on the strength of lap splices in tension. Lap splices with transverse links either adjacent to the lapped bars or at a distance of 4.5 times the bar diameter from the lap were tested. The stirrups index of confinement was similar in all the specimens. The results show a reduction of the lap strength up to 15% when the transverse links are not close to the lapped bars because of the splitting crack propagation which is not adequately counteracted by the confining action of the links. The test results show that the provisions of MC2010 for lap splices, with links relatively far, may be unconservative. Furthermore, an experimental database on the strength of lap splices with different distances of transverse links to the lapped bars is gathered from studies published in literature. This database enables to assess the accuracy of the efficiency factor km of confining reinforcement in the fib MC2010 formulation. Based on the statistical analysis of the test results concerning the confining reinforcement, a reduction is proposed for the effectiveness factor (km), to be applied whenever the distance of laps to the transverse links exceeds four times the bar diameter.