Performance-Based Design of Squat Reinforced Concrete Shear Walls (NEESR-SG)
Structural walls are widely used as seismic lateral-force-resisting components in buildings and nuclear facilities. Since most building structures are low-rise with columns spaced at approximately 30 feet on center and walls cast between columns, most structural walls are squat with aspect ratios of 1.0 or less. Conventional walls are constructed of reinforced concrete (RC). Currently, the design of these walls is based on demand/capacity equations addressing shear strength and prescriptive detailing requirements, which were developed for tall (high aspect ratio) walls, to ensure ductility. However, analysis of squat wall test data shows that current design equations result in a significant bias and scatter in the ratios of estimated to measured strength. As such, squat walls stand out among RC structural elements because of the large uncertainties in characterizing their behavior. Such bias and uncertainties are unacceptable for modern performance assessment methodologies for which unbiased estimates of strength and stiffness are needed as a function of deformation and load history.
The goal of this project is to fill the substantial gaps in knowledge noted above by developing curated numerical and visual experimental data on the seismic response of large-scale squat reinforced concrete wall specimens, validated tools for simulation of the seismic response of squat reinforced concrete walls, code-oriented design equations and improved prescriptive details to achieve specified levels of performance, fragility data suitable for immediate use in performance-based seismic assessment and design of conventional and nuclear structures, and teaching tools to effectively explain the resistance and failure mechanisms of squat walls.
The unique experimental capabilities of the NEES equipment sites at Buffalo and Berkeley will be used to execute the large-scale cyclic and hybrid-simulation experiments that must be performed to develop the datasets required to prepare robust numerical simulation, design guidance, and loss modeling tools. Other researchers will be able to use the curated experimental results to further advance understanding with alternate theories and numerical models. Physical experiments followed by numerical simulations will be used to develop guidance for structural engineers and loss/risk modelers on how squat reinforced concrete walls in buildings and nuclear structures perform during earthquakes.
This project will advance fundamental science and knowledge in engineering with substantial intellectual benefits to the structural engineering and loss modeling communities. Both disciplines will contribute to and benefit from the integrated physical and numerical simulation studies. The project will also train Ph.D. students, bring in undergraduate students from a teaching university, engage underrepresented students, impact building code development and performance-based seismic design, and outreach to a broad spectrum of end-users in the United States and abroad via web-accessed media, a Virtual Annual Meeting, and a Practice Committee composed of expert design professionals.
National Science Foundation Award Abstract
Del Carpio, M, Whittaker, A. S., and Gulec C.K. "An evaluation of predictive equations for the peak shear strength of squat reinforced concrete walls," Journal of Earthquake Engineering, v.16, 2012, p. 159.
Gulec, C. K., B. Gibbons, A. Chen and A. S Whittaker, “Damage states and fragility functions for link beams in eccentrically braced frames,”Journal of Constructional Steel Research, Vol. 67, Issue 9, pp. 1299-1309, August 2011.
Gulec, CK; Whittaker, AS; Stojadinovic, B. "Peak Shear Strength of Squat Reinforced Concrete Walls with Boundary Barbells or Flanges,"ACI STRUCTURAL JOURNAL, v.106, 2009, p. 368. View record at Web of Science
Gulec, C. K., Whittaker, A. S., and Hooper, J. D. "Fragility functions for low aspect ratio reinforced concrete walls," Engineering Structures, v.32, 2010, p. 2894.
Gulec, C. K. and Whittaker, A. S. "Empirical equations for the peak shear strength of low aspect ratio reinforced concrete walls," ACI Structural Journal, v.108, 2011.