FINAL REPORT: Performance and Repair of Ordinary Structural Walls Subjected to Wind and Seismic Loading Protocols (RGA 1-21)
The Charles Pankow Foundation along with industry supporters are pleased to announce the completion of RGA 1-21, Performance and Repair of Ordinary Structural Walls Subjected to Wind and Seismic Loading Protocols. The completed report is available for download at the link below.
CLICK HERE TO DOWNLOAD THE FINAL REPORT
- Principal Investigator was John W. Wallace, PhD, PE, Professor, F. ACI, F. ASCE.
- Industry Champions were Ron Klemencic, David Fields, Tony Ghodsi, Brad Malmsten, Ian McFarlane, Viral Patel, Thomas Sabol, and Fernando Torrealva.
- CPF Allies and Supporters included the American Concrete Institute Foundation and the MKA Foundation
Abstract: The design of buildings under wind demands has traditionally been based on prescriptive code provisions such as ASCE/SEI 7, which require the building components to stay essentially linear elastic. Recent developments in wind tunnel testing, structural analysis techniques, and performance-based design procedures led to the publication of the ASCE/SEI Prestandard for Performance-Based Wind Design (ASCE/SEI, 2019). The Prestandard allows limited inelastic behavior in ductile elements of a building’s Main Wind Force Resisting System (MWFRS) under extreme wind events. However, because yielding of some building components has not historically been permitted, there is limited research available on the inelastic behavior of structural elements subjected to wind demands. The advantages of the performance-based wind design (PBWD) are considered to be most impactful for the design of tall buildings, where it is very common to use coupled reinforced concrete shear wall systems as the MWFRS. Although substantial research has been conducted to understand the inelastic behavior of reinforced concrete and steel-reinforced concrete coupling beams, there is no published research that investigates the inelastic behavior of reinforced concrete shear walls under wind demands. To fill this gap, four reinforced concrete Cshaped structural walls were tested in two phases under quasi-static, biaxial cyclic loading protocols simulating extreme wind events. Following the wind loading protocol, a seismic loading protocol was applied.
Summary of Key Findings: The wind test results indicated that, for the wall with the low-to-moderate reinforcement ratio (CW-1, ρl=0.75%), rotational ductility demands of 3.0 can be achieved without any damage (e.g., concrete spalling, bar buckling, or bar fracture) and with very small residual flexural crack widths (around 0.1 mm). Since CW-1 failed at a rotational ductility demand of 20 during the seismic loading protocol, modest inelastic response can be allowed during extreme wind events for the walls with 0.75% or lower longitudinal reinforcement ratios. Concrete spalling was observed at the flange-web corners and the flange edges during the wind loading protocol for the walls with the higher longitudinal reinforcement ratio (1.5%). Depending on the amount of axial load applied during the biaxial load application, concrete crushing and bar buckling were also observed. Phase II tests showed that the flange edges were more susceptible to damage than other locations of the C-shaped walls. With moderate confinement provided at the flange edges and with a reduction in wall axial load during the biaxial loading (when the flange edges were under compression), bar buckling and concrete crushing were not observed during the wind loading protocols. Application of the seismic loading protocol revealed that, for the walls that did not sustain any significant damage during the wind tests, rotational ductility demands of at least 8.5 could be achieved prior to 20% loss in lateral strength.