Improving Earthquake Response of RC Structures by Seismic Detailing
A. K. M. Abdullah
This work presents a study on the effectiveness of seismic detailing in buildings designed to minimize earthquake effect. Several RC buildings of different heights (3-, 6- and 10-storied) are considered as structural models. The structures are analyzed (by the software STAAD-Pro) and designed for vertical loads only by the Working Stress Design (WSD) and Ultimate Strength Design (USD) method.
The seismic detailing provisions of the Bangladesh National Building Code (BNBC) are incorporated in the structures, including considerations for shear vs. flexural failure and weak beam strong column condition. The moment-curvature relationship of various beam and column sections are derived numerically, using the Kent & Park model for concrete and two stress-strain models for steel (elastic perfectly plastic model and another incorporating strain hardening), showing the ultimate moment and curvature capacity of the sections with and without seismic detailing.
Seismic detailing increases the moment capacity and particularly the ductility of the sections, mainly by increasing the ultimate curvature of concrete due to confinement. This makes the structures more ductile, which is a vital requirement for seismic design. Although there are more noticeable changes in the longitudinal reinforcements of beams, the special transverse confining reinforcements of columns increase its ductility almost five times, surviving storey sidesways of 6~24 inches. This would ultimately prevent sudden collapse of the structure during major earthquakes.
The cost of incorporating seismic detailing provisions is also evaluated and is found to be very small (around 1% of the original cost, for all the structures considered) and affordable compared to the original cost of construction.