10 Nov 2008: Design base Earthquake
12 Nov 2008: Design base Earthquake increased by 20%
- Moderate Damage
13 Nov 2008: Maximum Considered Earthquake
- Significant Damage
18 Nov 2008: (if structure allows)
- Severe Damage
20 Nov 2008: (if structure allows)
- Structure near collapse
One of the main challenges in earthquake hazard mitigation today is the performance assessment of existing buildings that were not designed according to modern code standards and the development of effective techniques to strengthen these structures. Non-ductile reinforced concrete (RC) frame structures with masonry infill panels, in particular, present a tremendous challenge because of the complicated and sometimes catastrophic failure mechanisms that could be induced by the frame-panel interaction.
The unreinforced masonry infills are normally treated as non-structural elements. However, unlike most non-structural components, they can develop a strong interaction with the bounding frames when subject to earthquake loads and, therefore, contribute significantly to the lateral stiffness and load resistance of the structure. In spite of the research efforts that have spanned several decades, the performance of these structures in a severe earthquake remains a major controversy among structural engineers and researchers today.
Understanding and assessing the seismic performance of masonry-infilled non-ductile RC frames presents a most difficult problem in structural engineering. Analytical tools to evaluate the complicated frame-infill interaction and the resulting failure mechanisms need to be built on the fundamental principles of mechanics and sound engineering judgment. It is far more challenging than analyzing a pure RC or masonry structure. This research will fill a major gap in the modeling and performance assessment of this class of existing structures that can be frequently found in regions of high seismic risk. Effective retrofit strategies will be developed for the seismic retrofit of these structures, which prohibit the undesired failure mechanisms from a system perspective, using conventional and innovative materials. The project will involve the development of new design and assessment techniques, new materials, and cutting-edge computational methods, which will be intellectually stimulating and can be used in engineering practice.
The George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Program of the National Science Foundation