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Dynamic earthquake performance formulation with sustainability impacts

The earthquake performance formulation developed by the Pacific Earthquake Engineering Research Center (PEER) typically assumes that the structure is in its as-built condition. In addition, the seismic hazard is represented through the conventional time independent Poisson process. It is also important to consider the time value of money when making loss forecast for future time frame. In this presentation, the PEER performance based earthquake engineering equation (PBEE) is reformulated to account for the dynamic changes in its components. The new dynamic performance based earthquake engineering formulation (DPEE) is presented and its components are discussed. Structural deterioration affects both the demand and the capacity of the structure. Methods for evaluating the demand and the capacity of deteriorating structures are presented. Time dependent earthquake occurrences pertain primarily to large infrequent events that are also the most devastating. The hazard equation is modeled by a lognormal or Brownian passage time equations to account for the increasing occurrence hazard with increasing time since the last occurrence of such large events. The time value of money is captured by traditional discount equations. Each component in the PEER equation that is time dependent is identified and formulated in the new DPEE. The methodology is illustrated through the analysis of three reinforced concrete columns designed respectively according to pre-1979, between 1979 and 1990, and post 1990 seismic codes. The demand on the structure is evaluated by considering the time since construction and the degree of corrosion in the column. The design year also affects the capacity of the structure. The columns are subjected to earthquakes from the Hayward fault and are situated in two different corrosion exposure environments that include splash zone at the coastline and locations that are within 15 km from the coastline. The main conclusions from the analysis are (a) time independent seismic hazard assumption can lead to a large underestimation of potential losses for areas where the last earthquake occurred in a period of time longer than its average interarrival time; (b) structural deterioration has significant effect on both engineering demand and capacity formulations and the integrated fragility functions; (c) increased design requirements such as greater concrete cover significantly reduce deterioration due to corrosion; (d) corrosion in structures is not only a function of time but of the environment in which the structure is situated; (d) consideration of environmental impacts resulting from repair and replacement have an important contribution to the overall loss.

Author(s):

Anirudh Rao    
The Global Earthquake Model
Italy

Michael Lepech    
Stanford University
United States

Anne Kiremidjian    
Stanford University
United States