Penilaian Kerentanan Seismik pada Jembatan Box Girder Beton Prategang Menerus Bentang Majemuk Eksisting melalui Pengembangan Kurva Fragilitas Analitik
Keywords:
Kurva fragilitas, Kerentanan seismik, HAZUS, NLTHA, NCHRP 440.Abstract
Pengembangan kurva fragilitas merupakan salah satu metode penilaian kerentanan jembatan terhadap beban gempa yang dilakukan untuk memastikan keamanan dan kemampuan layan jembatan selama dan pasca gempa. Kurva fragilitas menunjukkan nilai probabilitas terjadinya suatu tingkat kerusakan pada struktur jembatan akibat suatu intensitas gempa, sehingga dapat digunakan untuk mengidentifikasi potensi kerusakan dan menentukan level kinerja jembatan. Studi ini mengembangkan kurva fragilitas untuk Jembatan Box Girder-Beton Prategang-Menerus-Bentang Majemuk eksisting yang berlokasi di Jakarta, dengan studi kasus pada Jembatan JLNT Tendean. Pengembangan kurva fragilitas mengacu kepada standar HAZUS. Kurva fragilitas dikembangkan dengan melakukan Non-Linear Time History Analysis (NLTHA) pada Model Analisis 3D Jembatan menggunakan program MIDAS CIVIL 2011. Input beban gempa pada NLTHA berupa serangkaian ground motion spesifik situs Jakarta, yang telah diskalakan terhadap Respon Spektra Target baik pada kondisi Beban Gempa Rencana Jakarta maupun pada berbagai level intensitas gempa. Tingkat kerusakan struktur jembatan akibat suatu intensitas gempa ditentukan dari respon seismik hasil NLTHA, berdasarkan nilai parameter kinerja jembatan - NCHRP 440 (2013). Kurva fragilitas yang dihasilkan menunjukkan bahwa Jembatan JLNT Tendean berpotensi mengalami tingkat kerusakan menengah akibat Beban Gempa Rencana, dengan kategori level kinerja "Life Safety". Tingkat kerusakan runtuh dengan probabilitas terlampaui 50%, akan terjadi pada kejadian gempa dengan PGA sebesar 1.18g. Dengan demikian, dari studi ini dapat disimpulkan bahwa Jembatan JLNT Tendean memiliki fragilitas seismik yang rendah.
The development of fragility curve is one of method to assess the bridge vulnerability to seismic loading in order to ensure bridge"Ÿs safety and serviceability during and after an earthquake. Fragility curve describes the probability of a bridge reaching or exceeding a particular damage state for a given ground motion Intensity Measure (IM). Therefore, it can be used to identify bridge"Ÿs potential damage and performance level at certain level of seismic intensity. This study presents the fragility curve development of an existing Multi Span Continuous-Prestressed Concrete-Box Girder-Highway Bridge, namely JLNT Tendean, which is located in Jakarta. The development of fragility curve refers to HAZUS standard. The fragility curve is developed by performing Non-Linear Time History Analysis (NLTHA) on 3D analytical bridge model using MIDAS CIVIL 2011 program. A suite of Jakarta"Ÿs site-specific ground motion, which has been scaled both to Seismic Design Load and various level of seimic intensity Target Response Spectrums, will be used as seismic load input. Based on bridge performance parameters refer to NCHRP 440 (2013), the bridge"Ÿs structural Damage States due to various earthquake loadings, are defined from the seismic responses resulted from NLTHA. The developed fragility curve shows that moderate damage state can occur at JLNT Tendean due to Seismic Design Load, and the performance level is categorized as "Life Safety". The complete damage state with 50% probability of exceedance can occur on seismic event with PGA of 1.18g. Based on this study, it is concluded that the JLNT Tendean has low seismic vulnerability.
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