Studi Penerapan Lead Rubber Bearing pada Jembatan PCI Girder untuk Optimasi Substruktur Berdasarkan Nonlinear Time History Analysis

Aushaf Fathin Hasyim, Prof. Ir. Bambang Suhendro, M.Sc., Ph.D., IPU.

2026 | Skripsi | TEKNIK SIPIL

Jembatan PCI girder di Kabupaten Kudus berada pada kawasan dengan tingkat bahaya gempa yang tinggi akibat kedekatannya dengan Sesar Muria. Kondisi tersebut menyebabkan struktur berpotensi mengalami respons seismik yang besar sehingga diperlukan upaya untuk mengurangi gaya gempa yang diteruskan ke substruktur. Salah satu alternatif yang dapat diterapkan adalah sistem isolasi seismik berupa Lead Rubber Bearing (LRB). Penelitian ini bertujuan untuk mengevaluasi pengaruh penggunaan LRB terhadap karakteristik dinamik, respons struktur, dan kapasitas substruktur jembatan yang telah terbangun, serta menilai potensi optimasi substruktur berdasarkan perubahan respons akibat penerapan sistem isolasi.

Penelitian dilakukan menggunakan perangkat lunak MIDAS Civil dengan membandingkan model dengan tumpuan elastomeric bearing, LRB-K_eff, LRB-K₁, calibrated LRB-K_eff, dan calibrated LRB-K₁. Analisis meliputi analisis modal, linear time history analysis pada model elastomeric bearing, dan nonlinear time history analysis menggunakan tujuh rekaman gempa hasil spectral matching metode Hancock terhadap spektrum respons 1,2×MCER pada model LRB. Evaluasi dilakukan terhadap karakteristik dinamik, respons struktur, perilaku histeretik isolator, kapasitas pier, dan kapasitas fondasi.

Hasil penelitian menunjukkan bahwa penggunaan LRB mampu mereduksi respons seismik melalui kombinasi perpanjangan periode fundamental dan peningkatan redaman efektif hingga 27%, dengan perpindahan lateral isolator yang masih berada dalam batas kapasitas desain. Sebaliknya, model elastomeric bearing menunjukkan shear strain sebesar 231,95% yang melebihi batas regangan geser yang direkomendasikan sehingga berpotensi mengalami kerusakan. Pada model LRB-K_eff, gaya geser maksimum dan momen maksimum berkurang masing-masing sebesar 57,10?n 61,76% dibandingkan model elastomeric bearing. Kalibrasi parameter kekakuan efektif menurunkan rasio K_eff aktual terhadap K_eff input dari 2,03-2,36 menjadi 0,91-1,02. Reduksi respons tersebut memungkinkan optimasi substruktur dengan mengurangi diameter pier dari 2,5 m menjadi 2,2 m serta jumlah pile dari 16 menjadi 11 tanpa mengurangi tingkat keamanan struktur. 

The PCI girder bridge located in Kudus Regency is situated in a high seismic hazard area due to its proximity to the Muria Fault. This condition may result in significant seismic responses, making it necessary to reduce the earthquake forces transmitted to the substructure. One effective approach is the use of Lead Rubber Bearings (LRB). This study aims to evaluate the effect of LRB implementation on the dynamic characteristics, structural responses, and substructure capacity of a PCI girder bridge, as well as the potential for substructure optimization.

The study was conducted using MIDAS Civil by comparing five structural models consisting of an elastomeric bearing, LRB-K_eff, LRB-K₁, calibrated LRB-K_eff, and calibrated LRB-K₁. Structural performance was evaluated through modal analysis and time history analysis using seven ground motion records that were spectrally matched using the Hancock method to the 1,2×MCER response spectrum. Linear time history analysis was applied to the elastomeric bearing model, while nonlinear time history analysis was performed for the LRB models. In addition, effective stiffness calibration and capacity evaluation of the pier and foundation were carried out.

The results indicate that LRB implementation reduces the seismic responses transmitted to the substructure through a combination of an extended fundamental period and an increase in effective damping up to 27%, while maintaining the lateral displacement of the isolators within their design capacity. In contrast, the elastomeric bearing model exhibited a shear strain of 231,95%, exceeding the recommended shear strain limit and indicating potential bearing damage during seismic loading. Compared with the elastomeric bearing model, the LRB-K_eff model reduced the maximum shear force and maximum bending moment by 57,10% and 61,76%, respectively. Effective stiffness calibration reduced ratio between the actual and input effective stiffness from 2,03-2,36 to 0,91-1,02. The reduction in structural responses enabled substructure optimization by reducing the pier diameter from 2,5 m to 2,2 m and decreasing the number of piles from 16 to 11 without compromising structural safety. 

Kata Kunci : Lead Rubber Bearing, Isolasi Seismik, Nonlinear Time History Analysis, Optimasi Substruktur, Jembatan PCI Girder