SEISMIC DAMAGE PREDICTION OF SELECTED REINFORCED CONCRETE STRUCTURES IN MARIKINA CITY USING FRAGILITY CURVE

Abstract

The West Valley Fault, the source of the anticipated 7.2 magnitude earthquake or the "Big One," is said to have a return period of 500 years and has not moved since the 1600s. This study aims to predict the structural damage to be sustained by six existing reinforced concrete structures within a two-kilometer range from the fault line in Marikina City if the anticipated earthquake hits using a fragility curve. Nonlinear static pushover analysis was done to generate the idealized force-displacement curve, and then capacity spectrum conversion was performed to determine the structural damage states. Four distinct graphs are plotted in a single fragility curve; each represents a structural damage state, which is qualitatively and quantitatively defined. Due to the unpredictability of seismic motion, damage prediction is conducted separately in two different seismic directions. Given each structure's critical direction, it shows a probability ranging from 63.53% to 90.97% that it would suffer from some degree of structural damage. The structure with the highest likelihood of collapse is 21.16%, while the rest of the structures' collapse probability ranges from 1.14% to 7.17% in their critical direction. The severity of structural damage varies depending on the structure's configuration with respect to the fault line, the direction of the seismic motion, and the column dimension. A special moment frame for reinforced concrete structures is recommended since Marikina City is under Seismic Zone 4, and a minimum dimension of 300mm for all structural columns should be complied with.