UCLA

Reinforced concrete structural (shear) walls are commonly used as lateral load resisting systems in high seismic zones because they provide significant lateral strength, stiffness, and deformation capacity. Understanding the response and behavior of shear walls is essential to achieve more economical and reliable designs, especially as performance-based design approaches for new buildings have become more common. Results of a case study of 42-story RC dual system building, designed using code-prescriptive and two different performance-based design approaches, are presented to assess expected performance. Median values and dispersion of the response quantities are, in general, well-below acceptable limits and the overall behavior of the three building designs are expected to be quite similar. However, the ability to define shear failure and collapse proved difficult and provided motivation to conduct additional studies.

For both design of new buildings and evaluation/rehabilitation of existing structural wall buildings, an accurate assessment of median (expected) and dispersion of wall shear strength and deformation capacity are needed. A wall test database (124 specimens) was assembled to investigate the influence of various parameters on wall shear strength and deformation capacity, and to recommend alternative relations for strength and deformation capacity depending on expected wall behavior. Test results indicated that ACI 318-11 underestimates the shear strength of the shear-controlled walls. Mean curvature ductility ratios were obtained as about 3 and 7 for shear- and flexure-controlled walls, respectively. The new relations will allow improved damage and failure assessment of buildings utilizing structural walls for lateral load resistance.

Failure assessment of RC shear walls also was conducted for the 15-story Alto Rio building which collapsed in the 2010 Chile earthquake. Possible reasons for collapse were identified using post-earthquake observed damage, structural drawings, and nonlinear static and dynamic response analyses. Analysis results indicate that collapse was likely influenced by various factors, including compression failure at the web boundary of T-shaped walls on the east side of the building, large shear demands at the filled-in corridor walls at the first level, and tensile fracture and splice failures at the west side of the building.

Nonlinear modeling and analysis of the four-story RC building that was tested on E-Defense shaking table (2010) was investigated to assess current modeling approaches and assumptions, and to identify issues that require additional study. Including concrete tension strength, stiffness degradation, and strength degradation significantly improved the correlation between the analytical and test results.