Abstract

۱٫ Introduction

۲٫ Methods

۳٫ Results and Discussion

۴٫ Conclusions

References

Abstract

     In Indonesia, infrastructure, such as port facilities, has been damaged by earthquakes. Therefore, evaluating rational earthquake ground motions (EGMs) for seismic design is necessary to mitigate earthquake disasters in the future. The EGMs in the Indonesian Seismic Code are stipulated based on the ASCE standards and not on site-specific ones. This study aims to propose site-specific EGMs for the seismic design of port facilities in Indonesia. The EGM records and ground data in Indonesia were used for analysis. The EGM incidents in the bedrock were evaluated with deconvolution analysis. The obtained EGMs were amplitude-adjusted to peak ground acceleration similar to that of the EGMs in the bedrock in the Indonesian Seismic Code. A seismic response analysis considering nonlinear soil characteristics was conducted, and 144 EGMs at port sites were obtained. Considering the variation in the obtained EGMs, we propose site-specific EGMs for the seismic design of port facilities. A comparison of the proposed EGMs with those in the design code reveals that the difference between them is significant.

Introduction

     Indonesia is an earthquake-prone country, and Sumatra is one of its high-seismicity regions. The seismic activity in Sumatra is characterized by two geological features: the Sunda megathrust, which is an inter-plate subduction zone between the Indo-Australian and Eurasian plates, and the Sumatra fault zone that divides Sumatra into two parts [1]. Indonesia’s infrastructure (e.g., port facilities) has been damaged by earthquakes, such as the Sumatra–Andaman Islands earthquake in 2004 [2], the South Sumatra earthquake in 2007 [3], the West Sumatra earthquake in 2009 [4], and the Mentawai earthquake in 2010 [5]. Port facilities are installed on soft soils in coastal areas; therefore, they are vulnerable to earthquakes. Earthquakes that occurred in other areas, such as the 1995 Kobe earthquake [6], the 1999 Kocaeli earthquake [7], and the 2020 Samos earthquake [8], also caused severe damage to port facilities and led to the stagnation of the social economy.

     Evaluating the rational earthquake ground motions (EGMs) for seismic design is necessary to mitigate seismic disasters in high-seismicity countries, such as Indonesia. The seismic design code applied to port facilities in Indonesia is SNI 1726:2019, “Seismic Design Criteria for Buildings and Other Structures” (SNI) [9]. The code provides EGMs based on ASCE 7–۱۶ [۱۰] and the 2017 Indonesian Seismic Hazard Maps (ISHM) [11]. We provide a brief overview of how EGMs for seismic design are set up in the SNI.

Conclusions

     The SNI provides SAs for seismic design, but these have not been obtained with site-specific measurements. The amplification factors of the SAs were referenced from ASCE 7–۱۶ [۱۰], which uses EGM records and ground data obtained from sites other than Indonesia. We proposed site-specific EGMs for the seismic design of port facilities in Indonesia by performing a seismic response analysis of 144 cases using EGM records and ground data obtained in Indonesia. The main conclusions drawn from this study are as flolows:

     ۱٫ The site-specific SAs showed very large variation, especially in the period range of a quay. The SAs became very large when the predominant frequency of the EGM incident in the bedrock agreed with the natural frequency of the ground. The sitespecific EGMs must be evaluated using a seismic response analysis that considers the ground conditions at the site of interest. Moreover, the nonlinear soil characteristics must be properly considered.

۲٫ We studied the site-specific EGMs for seismic design for cases where the ground data at the target sites were not obtained in detail. The proposed SA targeted the envelope of the average SAs obtained in the analysis. The comparison of the proposed SAs with those in the SNI revealed that the former is larger than the latter in the period range of 0.2–۲٫۰ s for site class SD and in the period range of 1.0 s or longer for site class SE. The SNI underestimates the amplification factor of the EGMs for site class SD. For site class SE, the SNI falls short of considering the nonlinear characteristics of the soft sediment layers. For both site classes, conducting a reasonable seismic design of port facilities was made possible by using the proposed SAs.