Setiawan, Agus (2026) Analisis Performa Mekanis Struktur Jembatan Pelengkung Rangka Baja Dengan Perbedaan Elevasi Dudukan Pada Studi Kasus Jembatan Kereta Api Cisomang 3. Masters thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Penelitian ini menyelidiki permasalahan koefisien stabilitas terhadap deformasi vertikal dan lateral pada titik vault sebuah struktur jembatan rangka pelengkung baja yang meliputi validasi terhadap nilai frekuensi natural pada model struktur referensi, serta analisis hubungan antara grafik koefisien stabilitas terhadap perpindahan vertikal dan lateral puncak lengkung (vault) pada beberapa kondisi nonlinier dengan mempertimbangkan pengaruh nonlinieritas geometri saja, nonlinieritas ganda, dan kondisi modifikasi asimetris pada dudukan pelengkung. Permasalahan tersebut dianalisis melalui pemodelan struktur dengan menggunakan perangkat lunak MIDAS CIVIL. Dimulai dengan membuat model struktur identik sebagai model acuan dalam melakukan analisis yang mempertimbangkan berbagai kondisi non linier. Adapun boundary condition yang diterapkan adalah 8 buah perletakan jepit pada kolom vertikal, 4 buah perletakan sendi dengan pada girder lantai kendaraan, dan 4 buah perletakan sendi dengan memperbolehkan adanya rotasi arah sumbu Y pada dudukan pelengkung. Elastic link digunakan pada sambungan antara kolom vertikal dan girder. Analisis linear buckling dijalankan dengan menggunakan kombinasi pembebanan Kuat I sebagai kombinasi kritis terhadap deformasi arah vertikal, dan Kuat III pada arah lateralnya. Nodal acuan adalah nodal 44 yaitu nodal pada puncak lengkung (vault). Nilai eigen yang didapat dari pemilihan 2 kombinasi pembebanan tadi akan dijadikan sebagai nilai load amplification factor pada proses analisis nonlinier berupa sebuah proses iterasi yang menggunakan metode Newton-Rapshon dengan 40 buah load step. Hasil iterasi terhadap nilai deformasi arah vertikal dan lateral nantinya akan diplot menjadi grafik koefisien stabilitas terhadap deformasi puncak lengkung (vault). Hasil validasi menunjukkan bahwa perbedaan frekuensi alami sebesar 5% yang menandakan pendekatan terkait kondisi batas dan pemodelan struktur sudah mendekati jurnal acuan. Pada beberapa kondisi analisis nonlinier, imperfection dimasukkan sebagai parameter pembanding terhadap kondisi ideal/ no defects. Penurunan koefisien stabilitas struktur terjadi akibat imperfections dengan nilai yang tidak melebihi 5%. Pada analisis nonlinier, perenapan nonlinieritas geometri saja menghasilkan penurunan nilai koefisien stabilitas sebesar 5% pada arah vertikal dan 25% pada arah lateral. Penerapan nonlinieritas ganda menghasilkan penurunan nilai koefisien stabilitas sebesar 35% pada arah vertikal dan 87% pada arah lateral. Konfigurasi asimetris menghasilkan koefisien stabilitas yang lebih rendah dibandingkan konfigurasi simetris sebesar 24% pada arah vertikal dan 85% pada arah lateralnya, namun pengecekan terkait nilai deformasi vertikal pada tengah bentang jembatan masih berada dibawah nilai yang ditentukan pada peraturan PM 60-2012.
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Steel truss arch bridges are widely used for long-span crossings because of their high structural efficiency and load-carrying capacity. However, geometric imperfections, material nonlinearity, and asymmetric configurations may significantly affect their structural stability. This study investigates the relationship between the stability coefficient and the vertical and lateral deformations at the arch crown (vault) of a steel arch truss bridge. The research includes the validation of the natural frequencies of a reference structural model and evaluates the relationship between the stability coefficient and the vertical and lateral displacements of the vault under different nonlinear conditions, including geometric nonlinearity only, double nonlinearities, and asymmetric arch support configurations. A three-dimensional structure analysis model was developed using MIDAS Civil. An identical structural model was first established and validated against the reference model before conducting the nonlinear analyses. The boundary conditions consisted of eight fixed supports at the vertical columns, four pinned supports at the deck girders, and four pinned supports at the arch springings with rotational freedom about the Y-axis. Elastic links were assigned to the connections between the vertical columns and the deck girders. Linear buckling analysis was performed using the Strength I load combination for the critical vertical response and the Strength III load combination for the critical lateral response. Node 44, located at the arch crown (vault), was selected as the reference node for monitoring structural deformation. The corresponding eigenvalues obtained from the linear buckling analyses were subsequently used as load amplification factors in the nonlinear analyses, which were carried out using the Newton–Raphson iterative method with 40 load steps. The resulting vertical and lateral deformations were then used to establish the stability coefficient–vault displacement relationships. The validation results showed that the difference in the natural frequencies between the numerical model and the reference model was within 5%, indicating that the adopted boundary conditions and structural modeling accurately represented the reference structure. Initial imperfections were introduced as comparison parameters against the ideal (no defects) model. The presence of imperfections reduced the structural stability coefficient by less than 5%. Considering geometric nonlinearity only reduced the stability coefficient by approximately 5% in the vertical direction and 25% in the lateral direction. When both geometric and material nonlinearities were considered, the stability coefficient decreased by approximately 35% in the vertical direction and 87% in the lateral direction. Furthermore, the asymmetric arch support configuration produced lower stability coefficients than the symmetric configuration, with reductions of approximately 24% in the vertical direction and 85% in the lateral direction. Nevertheless, the calculated mid-span vertical deflection remained below the allowable limit specified in PM No. 60 of 2012. These findings demonstrate that double nonlinearities and arch springings configuration have a substantial influence on the stability performance of steel arch truss bridges and should be considered in the design and structural assessment of long-span steel arch bridges.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | cacat awal, analisis linier buckling, analisis nonlinier, konfigurasi asimetris, koefisien stabilitas, imperfections, linear buckling analysis, nonlinear analysis, asymmetic configuration, stability coefficient |
| Subjects: | T Technology > TA Engineering (General). Civil engineering (General) > TA645 Structural analysis (Engineering) |
| Divisions: | Faculty of Civil Engineering and Planning > Civil Engineering > 22101-(S2) Master Thesis |
| Depositing User: | Agus Setiawan |
| Date Deposited: | 27 Jul 2026 06:30 |
| Last Modified: | 27 Jul 2026 06:30 |
| URI: | http://repository.its.ac.id/id/eprint/138038 |
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- Analisis Performa Mekanis Struktur Jembatan Pelengkung Rangka Baja Dengan Perbedaan Elevasi Dudukan Pada Studi Kasus Jembatan Kereta Api Cisomang 3. (deposited 27 Jul 2026 06:30) [Currently Displayed]
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