Passive Structural Control with Sequential Coupling

Sequential coupling is a modification of a structural connection that permits an initial, zero resistance slip (or rotation) at each elastoplastic deformation cycle. A sequential structure is obtained when a specified number of connections of elements connected in parallel are replaced by sequential couplings. This modification decreases the yield resistance whenever the amplitude of an oscillatory deformation response is less than the length of the zero resistance slip, and is restored to its original value when the amplitude of the response exceeds the length of the slip. This property of the sequentially coupled structure increases the amplitudes of the local minimum (due to the reduced yield resistance) and thereby reduces the amplitude of the subsequent local maximum in each oscillatory sequence, resulting is a significant decrease of the global maximum response. The paper discusses this, hereto, unexplored phenomenon and its application to the design of structures subject to seismic excitation. The displacement response of a typical medium rise steel structure was computed by means of a single degree-of-freedom (SDOF) model. When sequential connections were introduced, it was found that the peak ductile response decreased by 30–50%. Inserting sequential connections leads to a significant improvement of the performance without increasing the size or number of structural members.