Reliability of structural wall shear design for tall reinforced-concrete core wall buildings

The developments of shear design acceptance criterion for structural walls in tall reinforced-concrete core wall buildings were reviewed and reliability studies were conducted. Over the past 10 years, the seismic action portion of the shear design acceptance criterion has consistently been in the general format of gamma F-u = phi F-n,F-e,F- where. is the demand factor, F-u is the mean shear demand resulting from a suite of ground motions, F-n,F-e is the nominal shear strength computed from expected material properties, and phi is the uncertainty in F-n,F-e. Between the governing code, ASCE7-16, and the tall building guidelines, PEER TBI (2010, 2017) and LATBSDC (2011, 2014, 2017, 2020), there has been a lack of consensus in the recommendations for. and gamma factors phi Thus, reliability studies were conducted on the shear design acceptance criterion, with 20- and 30-story case study buildings designed and analyzed per LATBSDC (2014) guidelines. Using closed-form solutions and Monte Carlo simulations, for the range of f'(c) considered, the shear design acceptance criterion using gamma = 1.5, phi = 1.0, and a conservative dispersion in shear demand of rho(D) = 0.50 resulted in at least 94.2% reliability, conditioned upon MCE hazard level ground shaking, suggesting that the current LATBSDC (2020) recommendations provide adequate safety. For a reduction in safety (e.g., use of. < 1.5), further reliability studies including a larger population of tall buildings will be needed to calibrate gamma and phi factors.