Ductile Design of Box Columns in Seismic Zones: Reducing Brittle Failure

Design Principles:
Box columns in seismic zones should follow the "strong shear, weak bending" principle, ensuring that shear bearing capacity is higher than bending bearing capacity to prevent shear brittle failure from occurring before bending ductile failure. At the same time, the requirements of "strong column, weak beam" and "strong joint, weak member" must be met to form multiple seismic defense lines.

Key Measures:
Increase the shear resistance of the column end by increasing the stirrup density and reinforcement ratio; optimize the section height-to-width ratio (such as controlling it within 3-5 times) to reduce stress concentration in the plastic hinge zone. Use haunch design in the joint area to avoid concrete crushing.

Performance Verification:
The calculated value of the ultimate displacement of a reasonably designed box pier is close to the measured value. When the height-to-width ratio increases, additional verification of curvature attenuation is required. In actual engineering, structural details should be adjusted in combination with quasi-static test data.