Elastic torsional response of L-shaped frames under earthquake wave passage excitation with varying low-frequency content

Torsional effects in planar irregular buildings can lead to structural damage, making torsional response analysis of buildings a critical aspect of structural design. This study conducts numerical simulations on L-shaped frames subjected to frequent earthquakes to investigate the influence of low-frequency content on the torsional responses of planar irregular frame structures (PIFSs). Five L-shaped frame models with varying length-to-width ratios (L/B) of the protruding limbs-1:1, 1.5:1, 2:1, 2.5:1, and 3:1 were developed using ABAQUS. Columns were modeled using solid elements, reinforcing steel with truss elements, and floor slabs with shell elements. The peak shear forces and bending moments in corner columns were compared under various conditions of low-frequency content to analyze the effects of low-frequency content and L/B ratios on wave passage effect in frames. The results indicate that when the low-frequency content of seismic waves is sufficient, wave passage effect occurs in outer corner columns, whereas inner corner columns remain unaffected. At apparent wave velocity of 2000 m/s, increasing L/B ratios amplify peak shear forces and bending moments in wave-facing outer corner columns by 28.3% and 43.8%, respectively. Conversely, when the low-frequency content of seismic waves is insufficient, neither outer nor inner corner columns exhibit wave passage effect.