UC Berkeley

During the last two decades, the structural engineering profession has realized the need for a change in the traditional code design philosophy to assess existing structural systems and the design of new ones. Traditionally, researchers use deterministic methods, and the outcomes are typically presented in terms of variables only relevant to the structural engineers, such as forces or displacements. Instead, modern methods follow a Performance-Based Earthquake Engineering (PBEE) approach. This trend of PBEE has been motivated by observations after past earthquakes. Even with a small number of or no collapse cases and when buildings met the life safety objective of the traditional design philosophy, the socio-economic losses due to damage, monetary losses, repair costs, or downtime, could be significantly high and unacceptable to the owners of the structures and the community as a whole.To overcome the shortcomings of the traditional code design philosophy, probabilistic methods that consider all sources of uncertainties that affect the seismic performance of structures are gaining popularity not only in academia, but also in the practicing engineering community. The Pacific Earthquake Engineering Research (PEER) Center developed the PBEE methodology to evaluate and design structures using performance measures which are in the directinterest of stakeholders, instead of engineering parameters. The PEER PBEE methodology decomposes the problem into four different phases of analyses: hazard, structural, damage, and loss. Furthermore, it considers uncertainties in all the four phases, along with a robust formulation of their accumulation. This study presents a Performance-Based framework for the seismic assessment of Reinforced Concrete (RC) frame buildings with Unreinforced Masonry (URM) infill walls. The selection of this structural typology is motivated by its widespread presence in countries with developing economies worldwide in high seismicity regions with high vulnerability and exposure. Case studies are presented with geometric features and reinforcement configuration of buildings compatible with the Colombian building typology in high-risk seismic zones. The performance of the archetype buildings in the case studies are estimated in terms of economic losses using the PEER-PBEE methodology. One key finding was that, at least for the considered two buildings, there is not a significant change in the loss estimation due to the uncertainty in the damage and loss functions for the URM infill wall. The impact of including or not including the infill walls on the loss estimation process was also assessed, for the 4-story ductile building which had high strength infill walls, there was not a significant change in the loss curves of the bare frame case compared to the infilled case. On the other hand, for the 6-story non-ductile building which had low strength infill walls, the inclusion of the infills in the loss estimation process did increase the expected losses when compared to the bare frame case. Finally, the loss estimation for both case study buildings was compared; it was noted that for both cases, infilled and bare frames, the probability of exceeding a given threshold of economic loss is much smaller for the 4-story ductile case study compared to the 6-story building, as expected, a ductile building performs better under seismic loads when compared to a non-ductile building, which translates into less economic losses.