New reinforced-concrete members in existing structures: Lapped joints with smooth and deformed bars

摘要

In building on existing structures, reinforced-concrete members are frequently placed against existing structural members. This is best achieved with lapped joints. Until the end of the 1950s, primarily smooth bars, as a rule, bars with low yield strength, were used. The deformed bars, which were introduced under a national technical approval in the 1950s, were regulated in the relevant design code DIN 1045 only since 1972. While historic lapping of smooth bars was possible only with end hooks and additional restrictions on impact contributions and steel stresses, lapping of single-layer lapped splices with deformed bars has been allowed already since the 1970s, making full use of the material and without stagger, with straigth bar ends. In contrast to the lapped splices of reinforcing bars of equal type and quality, whose implementation has been standardized since 1925, combin-able lapped splices of smooth and deformed bars of different yield strength are not regulated to this day.