SEISMIC RELIABILITY ANALYSIS OF LIFELINE: A CASE STUDY ON THE WATER NETWORK SYSTEM OF BIÑAN CITY, LAGUNA

Abstract

Lifelines are essential networks and it is vital for these network systems to remain properly functional during or after destructive earthquakes. In the Philippine geographical context, the West Valley Fault which traverses Metro Manila is a seismic threat capable of producing a maximum magnitude of 7.2. In this study, the reliability of Laguna Water network system was assessed under earthquake loads due to West Valley Fault. Probabilistic seismic hazard analysis (PSHA) was utilized to estimate the seismic hazard of the network area. Recorded earthquake history from the Philippine Institute of Volcanology and Seismology was used as part of the seismic analysis. The analysis estimated the ground motion values by using a similar Ground Motion Prediction Equation (GMPE) used in the latest Philippine Earthquake Model (PEM). Seismic hazard analysis shows that the earthquake hazards for the site are peak ground accelerations of 0.52g and 0.62g for return periods of 500 and 2500 years respectively. Using the ground motion intensity, ground strain value was attained ranging from 0.02% to 0.16% at scales of 0.1g to 1.0g. Monte Carlo simulation was used to determine the probability of damage. Using the unscaled peak ground acceleration, the probability of minor damage ranges from 15% to 19%. Given a 2500-year return period, seismic hazard analysis resulted to a peak ground acceleration of 0.62g which has a 20% probability for pipes to experience minor damage. Subsequently, the entire network system has a 1% probability of minor damage given the same return period of seismic hazard.