Sensitivity Analysis of Pile Supported Wharves against Directional Uncertainty of Earthquakes Using Fragility Curves

Abstract

This paper aims to tackle an important uncertainty which extremely affects seismic performance of wharf structures in earthquake events. According to previous studies performed for structures on land, it is shown that structures on land are highly susceptible to unknown orientation of earthquakes called as the directional uncertainty. However, for marine structures, especially pile supported wharves, research efforts are rare to assess the effect of directional uncertainty of earthquakes on structural responses. Therefore, to show this effect on seismic performance of pile supported wharves, fragility analysis is performed based on methodology suggested by Pacific Earthquake Engineering Research Center (PEER) for the modeled pile supported wharf located in Maah-shahr port as a case study. As the first phase of this methodology, nonlinear static pushover analyses are performed for randomly chosen incident angles in order to quantitatively measure damage states suggested by marine design code. After damage states are obtained, IDA analyses are conducted in the selected incident angles to obtain nonlinear structural responses which are supposed to be used for fragility analysis as inputs. Finally, once fragility curves have been developed according to the last phase of PEER methodology, the more vulnerable direction(s) of wharf from those incident angles is represented.

Effect of earthquake directional uncertainty on the seismic response of jacket-type offshore platform

“…In the first one, the two horizontal components of the records are applied along two orthogonal principal axes, and According to the second procedure MIDA is performed over a sample of incident angles from 0 to 180 degrees that is DMIDA. In this study, we have rotated the axis of the coordinates of the incidence by 22.5 degrees [35,55], and the angles of 0, 22.5, 45, 67.5, 90, 112.5, 135, 157.5, and 180 are the angles of the earthquake incidence according to figure 4. final step is to adopt the 16%, 50%, and 84% fractile MIDA and DMIDA curves for developing the limit state fragility curves. It should be mentioned that according to API standard, seismic load and other environmental loads such as wave, wind, and current should not apply simultaneously to offshore structures [32].…”

“…EDPs and DMs are used. In this phase, the conditional probability of structure responses exceeding damage states of Si at a specific PGA level is obtained as fragility curves (Eq.1) [54,35].…”