Research Needs for Seismic Rehabilitation of Sub-standard Buildings using Stiff Rocking Cores: Fid-Bau Portal

Research Needs for Seismic Rehabilitation of Sub-standard Buildings using Stiff Rocking Cores

Pollino, M. / Sabzehzar, S. / Qu, B. / Mosqueda, G.

Seismic demands on steel building frames can result in concentrated inter-story drift and a "soft-story" mechanism in multistory buildings which has led to severe structural damage or collapse in past earthquakes. Such deficiencies in building structures can be found in seismic regions throughout the world and are especially problematic in developing countries. Furthermore, structures near an active fault may be subjected to near-fault ground motion pulses that have tendency to induce very large, concentrated ductility demands in the lower stories of buildings. Economic and sustainable solutions for rehabilitation of such structures are needed in order to reduce seismic risk. An approach for rehabilitation of seismically sub-standard buildings through implementation of stiff elastic rocking cores (SRCRehab) is currently being investigated by researchers. The stiff rocking core (SRC) has the potential to re-distribute seismic forces along the core height, creating a more uniform drift and ductility demand distribution. Due to the core's low rotational resistance at its base and high inter-story stiffness, it does not attract all of the seismic forces through the core to the foundation however re-distributes seismic ductility demands from floors that would otherwise have significant concentrated ductility demands, potentially preventing collapse. The fundamental behavior and interaction of rehabilitated steel frames using a stiff rocking core is presented along with the results of nonlinear, response history analyses which applies suites of ground motions typical of far-field and near-field sites. The results are used to identify the key parameters for effective rehabilitative design of sub-standard frames. The paper also describes the planned hybrid experimental testing program which will be performed at the UB-NEES site. The hybrid testing technique will allow for computational modeling of the existing sub-standard framing and experimental testing of the SRC.