Torsional irregularity of NSC and HSC asymmetric multistory 3-D buildings

Abstract The reliability of the criteria adopted by the seismic codes in the United States (ASCE/SEI-7-16), in Europe (EC-8) and Egypt (ECP201-2012), that are used in distinguish torsionally irregular from torsionally regular Normal-Strength Concrete (NSC) and High-Strength Concrete (HSC) multistory 3-D buildings have been studied. The Static Equivalent Lateral Force (SELF) methods used by these codes for predicting the torsional moments have been examined when applied to NSCand HSCtorsionally asymmetric multistory buildings. Finite element model has been used to solve the nonlinear equations of motions for two multistory buildings examples with different eccentricity (e equal to 0.10Li, 0.15Li and 0.20Li) and constructed from NSC ( $$f_{c}^{\prime }$$ f c ′  = 25 N/mm2), HSC( $$f_{c}^{\prime }$$ f c ′ up to 75 N/mm2) and VHSC ( $$f_{c}^{\prime }$$ f c ′ up to 100 N/mm2). Many different earthquake records have been used in the seismic analysis. The results showed that the criteria adopted by ASCE/SEI-7-16 so as to distinguish torsionally regular from torsionally irregular NSC, HSC and VHSC multistory buildings are the most reliable and more simple and accurate when compared with the methods adopted by EC-8 and ECP201-2012. The provisions of ECP201-2012 for determination of the torsional irregularity of a building depending on the calculated structural eccentricity (between C. M. and C. R.) may lead to unsafe results. Using the SELF methods of the studied seismic codes in predicting the torsional moments of some torsionally symmetrical and torsionally asymmetrical multistory buildings constructed from NSCand HSCmay lead to unsafe and unconservative predictions. The value of the accidental eccentricity adopted by the studied seismic codes underestimated the torsional moments predicted using SELF methods of the studied codes in some torsionally symmetrical and torsionally asymmetrical multistory buildings.