Seismic performance of steel and shape memory alloy reinforced concrete framed buildings.

摘要

Reinforced Concrete (RC) framed buildings are generally seismically designed for safety, where earthquake energy is dissipated through yielding of the reinforcing bars. During strong earthquakes, high inelastic deformations take place and severe damage occurs resulting in significant permanent deformations. The severity of the damage is magnified when the earthquake has a strong vertical component. If buildings could regain their original state following a seismic event, then problems associated with permanent damage could be mitigated. Superelastic Shape Memory Alloys (SMAs) are unique materials with the ability to regain their original length upon unloading. If superelastic SMA bars are used to reinforce concrete frames, earthquake energy can be dissipated while the residual deformations are kept at minimal values. SMA has two drawbacks: the high price and the relatively low modulus of elasticity. Minimizing the amount of SMA bars can address these disadvantages. This thesis studies the use of SMA bars to improve the seismic performance of RC frames in terms of residual deformations and failure mechanism.;Engineers need a practical tool to judge on the serviceability of a seismically damaged building and to identify locations of severe damage. A simple method to predict the local seismic damage of RC frames is developed. The method is valid for earthquakes having a strong vertical component. The method uses static pushover analyses to define maximum and residual drift limits for each storey. These drifts are then magnified to account for the reduction of the lateral stiffness due to the rotation of the lower column ends. The method is validated using analytical/experimental work by others. A six storey building is used to provide a comprehensive case study to evaluate the developed method.;Due to the aforementioned drawbacks of SMA, a design technique to minimize the use of SMA reinforcing bars in RC frames is introduced. This technique uses the developed method to identify local damage and modal analyses to define the critical sections. The proposed technique is then validated by designing two SMA RC frames (9 and 12 stories). The seismic performance of the two frames is compared with similar steel RC frames. The designed SMA RC frames provide outstanding seismic performance with lower damage, reasonable values of MID, and significantly low values of MRID.;KEYWORDS: reinforced concrete frame, shape memory alloy, superelasticity, plastic hinge, static pushover analysis, Incremental dynamic analysis, residual drift, Inter-storey drift, vertical earthquakes, damage scheme.;A six-storey steel RC frame is designed according to current seismic standards and subjected to scaled versions of the horizontal (and vertical) component(s) of five ground motion records. The observed damage schemes allowed defining the critical sections. The RC frame is redesigned by utilizing SMA bars in the vicinity of the critical sections, creating a total of seven SMA RC frames. The seismic performance of these frames is compared to that of the steel RC frame in terms of damage schemes, Maximum Inter-storey Drift (MID), and Maximum Residual Inter-storey Drift (MRID). The frame with SMA bars at the critical beam sections and at the beams adjacent to the critical columns is found to have the best seismic performance when considering or ignoring the vertical seismic component.