The project develops two innovations.
The first innovation promotes a construction measure by which the "soft storey" mechanism is obviated in the lower storeys of reinforced concrete (R.C.) frames by encasing steel profiles in R.C. columns in order to provide them with a basic reliable shear, bending and compression resistance. Tests are performed and comparison of the behaviour of reference reinforced concrete and composite specimens made. Several parameters are studied: axial load, length of anchorage, stiffeners in the panel zone, weak and strong axis bending, configurations with and without infills. The study defines design rules for steel
profiles to be encased in ductile R.C. columns, formulas for the behaviour of local strut and tie mechanism in presence of infills and formulas for the calculation of the shear resistance of a composite beam-to-column panel zone in configurations without infills.
The second innovation consists in using dissipative connections for diagonals of frames with concentric bracings. Two types of connections are studied: the “pin” connections, made of bent rounded or rectangular bars, and “U-device” connection, made of plates bent in U. Their behaviour is studied experimentally on connections and on complete bracings. Design rules are defined, especially for the
pin connection, and fatigue curves obtained. The applicability and interest are set forward by numerical studies and comparative design of structures with classical and with dissipative connections. The innovation demonstrates a higher capacity to dissipate energy. It can be translated into higher behaviour factor q
