Electronic Theses and Dissertation

KAJIAN RESPON JEMBATAN DI ACEH UTARA TERHADAP GEMPA
BERDASARKAN DATA MIKROTREMOR

Zaki Mutaram
NIM 1804201010041

Program Studi Magister Teknik Sipil
Jurusan Teknik Sipil - Fakultas Teknik
Universitas Syiah Kuala
Abstrak

Kerusakan atau kegagalan pada infrastruktur jembatan akan memberikan dampak yang
besar pada usaha pelaksanaan evakuasi dan penyaluran logistik pasca bencana. Aceh
Utara termasuk daerah yang rawan terhadap bencana gempa, terdapat beberapa
patahan sekunder yang terdeteksi di Aceh Utara yaitu Patahan Peusangan dan Patahan
Nisam Antara. Pada beberapa kejadian gempa, tercatat kerusakan-kerusakan sehingga
penting untuk menganalisa performa jembatan saat dilalui oleh beban gempa, salah
satunya dengan pengukuran mikrotremor dengan menilai respon dinamik jembatan.
Pengukuran mikrotremor dilakukan pada dua tipologi jembatan yang berbeda yaitu
jembatan rangka baja dan jembatan beton bertulang. Tujuannya yaitu mengetahui nilai
karakteristik dinamik jembatan dan kelayakan jembatan berdasarkan batas periode
getar alami jembatan berdasarkan SNI 2833-2008. Metode HVSR (Horizontal to
Vertical Spectral Ratio) digunakan untuk menganalisis data mikrotremor pada tanah,
sedangkan pengolahan data mikrotremor pada jembatan menggunakan metode FSR
(Floor Spectral Ratio) dan RDM (Random Decrement Metode). Hasil penelitian pada
studi kasus pertama pada jembatan rangka baja nilai frekuensi natural tanah 1,25 - 1,35
Hz. Nilai frekuensi natural jembatan dari FSR adalah 0,81 - 3,29 Hz dan hasil RDM
adalah 1,12 - 3,46 Hz, frekuensi yang diperoleh kurang stabil pada komponen NS.
Hasil rasio redaman 2,02 - 4,97%. Pada studi kasus kedua, analisis dilakukan pada
jembatan beton bertulang, nilai frekuensi natural tanah diperoleh 1,11 - 1,47 Hz. Nilai
frekuensi natural jembatan dari FSR adalah 2,21 - 3,62 Hz dan hasil RDM adalah 2,30
- 3,62 Hz, frekuensi yang diperoleh cenderung stabil pada setiap komponen, hasil rasio
redaman 2,05 - 4,81%. Periode getar alami dari hasil pengukuran lapangan
menunjukkan hasil yang identik dengan periode hasil perhitungan teoritis dengan ratarata
peningkatan
7,24%.
Rata-rata
nilai
rasio
redaman
jembatan
berkisar
3,16%,
hasil

ini
sesusai
dengan
literatur
yakni
berkisar 2
–
5
%.
Kata kunci: Jembatan, Mikrotremor, Frekuensi Natural dan Resonansi.

THE STUDY OF BRIDGE RESPONSE IN NORTH ACEH TO THE EARTHQUAKE BASED ON MICROTREMOR DATA Zaki Mutaram Student Number 1804201010041 Master Program of Civil Engineering Civil Engineering Department of Engineering Faculty University of Syiah Kuala Abstract Damage or failure to bridge infrastructure will have a major impact on the implementation of evacuation efforts and post-disaster logistics distribution. The Peusangan Fault and the Nisam Antara Fault are two secondary faults that have been found in North Aceh, an area that is prone to earthquakes. The performance of the bridge when it is traversed by earthquake loads must be analyzed since damage has been observed in a number of earthquake events. One method of doing this is by measuring microtremor by evaluating the dynamic response of the bridge. Microtremor measurements were carried out on two different bridge typologies, namely steel truss bridges and reinforced concrete bridges. The objective is to assess the value of the bridge's dynamic properties and its viability based on the natural vibration period limit of the bridge based on SNI 2833-2008. The microtremor data processing on the bridge used the FSR (Floor Spectral Ratio) and RDM (Random Decrement Method) methods, whilst the microtremor data processing on the ground used the HVSR (Horizontal to Vertical Spectral Ratio) method. The natural frequency value of the soil is 1.25 to 1.35 Hz, according to the research findings in the first case study on a steel truss bridge. In contrast to the RDM results, which range from 1.12 to 3.46 Hz, the natural frequency of the bridge determined by the FSR is less consistent on the NS component. The calculated damping ratio is 2.02 - 4.97%. The soil's natural frequency value ranged from 1.11 to 1.47 Hz in the second case study, which involved the investigation of a reinforced concrete bridge. The attenuation ratio results are 2.05 - 4.81, and the frequency acquired tends to be constant in each component. The natural frequency value of the bridge derived from the FSR is 2.21 - 3.62 Hz, and the RDM values are 2.30 - 3.62 Hz. With an average rise of 7.24%, the results of field measurements for the natural vibration period match those of the theoretical calculation period exactly. The average value of the bridge damping ratio is around 3.16%, this result is in accordance with the literature which is around 2 - 5%. Keywords: Bridge, Microtremor, Natural Frequency and Resonant.