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This study presents an energy-based procedure for the design of RC frames under earthquake strong motions. For this purpose, three RC frames having 4, 8, and 12 stories that were used in FEMA P695 were selected. The code-based designed frames were analyzed and redesigned employing the proposed energy-based procedure. A comparison was conducted between the performance of the code-based and energy-based designed models. Results reveal that the energy-based models appeared to perform more effectively under strong ground motions in terms of more optimized use of beam capacity for dissipation of energy, higher ductility values, and more uniform distribution of plastic hinges in height of structure. Comparison of pushover curves showed that ductility value in energy-based frames increases nearly 1.5–2.0 times the ductility of code-based frames. Calculated hysteretic energy demand in energy-based frames is also proved to decline by 50% in lower stories and, instead, the contribution of upper stories is increased. The same pattern for distribution of interstory drift ratio is also observed. [ABSTRACT FROM AUTHOR]

A new bending connection between a steel beam and concrete-encased composite column (CEC S) with a bolted flange plate is proposed which maintains the integrity of the column and allows for the interchangeability of the beam for improvement of the connection. The confinement of the steel plates and the central steel core (H-section column) is provided by reinforced concrete and cover plates, thus lateral torsional and local buckling of the through plate (TP) and the central core is prevented. Three full-scale samples of the proposed exterior connection with variable TP thickness and different bending capacities under lateral cyclic and constant axial loads in the column were tested. The moment contribution in the components and seismic behavior of the connection were studied. The load transfer to the panel zone occurred through four components in the bending plane; TP, concrete performance, tensile studs, and side plates. The average share of the resistant elements which is immediately behind the front plate were determined as 56%, 26%, 12.50%, and 5.5%, respectively. The internal panel zone remained undamaged and the stresses were below the yield limit, so that the plastic hinge could occur outside the connecting members in the beam. In general, the specimens with sufficient pre-tensioning in the connection bolts had stable hysteresis curves and less pinching. In addition, these specimens showed acceptable energy dissipation that provided a high ductility index. • Integrity of the column and continuity of the longitudinal reinforcement in the internal panel zone • No requirement for transverse reinforcement in the region of the internal panel zone • The confinement of the through plate and the central steel core by reinforced concrete and cover plates • Determination of moment contribution of the connection components using analytical method and experimental tests • Showing acceptable cyclic behavior and appropriate energy dissipation [ABSTRACT FROM AUTHOR]