ACI 318-19 Changes to the Concrete Design Standard-Seismic

Video Transcription

Video Summary

The discussion elaborates on seismic design according to ACI 3.18.19, emphasizing nonlinear design philosophy in the United States, which permits the response of concrete and reinforcement in the inelastic range. The design philosophy focuses on strength rather than service-level forces, allowing yielding of reinforcement and concrete cracking. Emphasis is placed on accounting for non-linear behavior using parameters like the overstrength factor (omega), displacement factor (C sub d), and ductility factor (R).<br /><br />An example outlines specific parameters for specially reinforced concrete shear wall systems with design limitations in various seismic design categories. The inelastic action, such as plastic hinge formation, enhances energy dissipation. Strength is maintained by controlling inelastic action at predetermined locations. Prescriptive rules for reinforcement detail are key for robust plastic hinges.<br /><br />The code incorporates recent changes, like using 80 KSI yield strength reinforcement in moment frames, improving seismic design layouts. The strong column-weak beam concept is underscored, highlighting column strengthening to promote beam hinging. Detailed reinforcement rules, including bond splitting prevention and improving detailing for ductile performance, have been refined for current construction and future resilience.<br /><br />Building codes necessitate design adaptations considering walls' drift capacity, shear demand, and reinforcement ratios. New metrics for ductile coupled walls have been identified, ensuring enhanced seismic resilience. Standards for deep foundations, like piles and piers, are defined with considerations for longitudinal reinforcement, transverse confinement, and tension load pathways, underscoring code amendments to ensure structure integrity under seismic conditions.

Keywords

seismic design

ACI 3.18.19

nonlinear design

inelastic range

reinforcement yielding

overstrength factor

plastic hinge

strong column-weak beam

ductile performance

deep foundations