1) is obtained, which indicates the condition of the bridge is safe and feasible to operate."> 1) is obtained, which indicates the condition of the bridge is safe and feasible to operate.">
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Uji Kelayakan Balok Prategang Berdasarkan Analisis Perilaku Frekuensi dan Lendutan Balok Hasil Pengujian Laboratorium

WAHYU SETYANINGSIH, Prof. Ir. Henricus Priyosulistyo, M.Sc., Ph.D.

2024 | Skripsi | TEKNIK SIPIL

Salah satu parameter yang dapat menentukan syarat kelayakan jembatan secara teoritis maupun eksperimen adalah nilai frekuensi alami jembatan. Laju kerusakan struktur jembatan dapat dideteksi dengan perubahan nilai frekuensi alami jembatan. Semakin tinggi tingkat kerusakan dan beban yang dipikul maka nilai frekuensi alami jembatan umumnya semakin rendah. Namun, dengan adanya gaya prategang pada tendon struktur jembatan beton prategang, nilai frekuensi alami tidak mengalami penurunan yang signifikan antara sebelum dan setelah dilakukan pengujian. Tujuan penelitian ini adalah menilai kapasitas jembatan prategang dengan mengetahui perilaku frekuensi dan lendutan jembatan beton prategang terhadap pengujian laboratorium.  

Pengujian mengacu pada SNI 1725:2016 terkait beban hidup berupa beban lajur “D” terbagi rata “BTR” dan uji evaluasi batas lendutan. Sedangkan beban terpusat ditambahkan guna mencapai batas izin lendutan maksimum pada jembatan, menggunakan hydraulic actuator. Parameter lendutan diukur dengan alat LVDT yang diletakkan pada 1/3, ½, dan 2/3 bentang. Saat pengujian, getaran pada jembatan direkam menggunakan alat accelerometer. Secara teoritis, penilaian beban ditentukan menggunakan metode load rating factor yang mengacu pada Pedoman Penentuan Nilai Sisa Kapasitas Jembatan (2011). Metode ini berfungsi memperkirakan kapasitas dan mengetahui faktor keamanan struktur jembatan.

Berdasarkan hasil pengujian laboratorium dan pengolahan data, diperoleh frekuensi balok  sebelum dibebani sebesar 20,5 Hz dan setelah dibebani (seluruh beban diunload) sebesar 19,57 Hz. Meskipun selisih nilai frekuensi tersebut tidak signifikan, penurunan nilai frekuensi menandakan adanya retak halus pada balok. Retak terjadi ketika balok diberi beban actuator 4,5 ton yang mencapai lendutan 5 mm. Hal tersebut dibuktikan dengan perbandingan massa dan frekuensi dengan asumsi nilai kekakuan yang sama. Ketika diberi beban actuator, microcrack terbuka, setelah release beban actuator  microcrack kembali tertutup oleh pengaruh gaya prategang. Dari hasil perhitungan load rating pada jembatan, diperoleh rating factor (RF) sebesar 1,16 (>1), yang menandakan kondisi jembatan aman dan layak beroperasi.

One of the parameters that can determine the eligibility requirements of the bridge theoretically and experimentally is the natural frequency value of the bridge. The rate of damage to the bridge structure can be detected by changes in the natural frequency value of the bridge. The higher the level of damage and the load carried, the lower the natural frequency value of the bridge generally. However, in the presence of prestressing forces on the tendons of the prestressed concrete bridge structure, the natural frequency value does not experience a significant decrease between before and after testing.

The purpose of this research is to assess the capacity of prestressed bridges by knowing the frequency and deflection behavior of prestressed concrete bridges against laboratory tests.  Testing refers to SNI 1725: 2016 related to live loads in the form of "D" lane loads divided equally "BTR" and deflection limit evaluation tests. While the centralized load is added to achieve the maximum deflection permit limit on the bridge, using a hydraulic actuator. Deflection parameters were measured with LVDT devices placed at 1/3, ½, and 2/3 of the span. During the test, the vibration of the bridge was recorded using an accelerometer. Theoretically, the load assessment is determined using the load rating factor method which refers to the Guidelines for Determining the Residual Value of Bridge Capacity (2011). This method serves to estimate the capacity and determine the safety factor of the bridge structure.

Based on the results of laboratory testing and data processing, the beam frequency before loading was 20.5 Hz and after loading (all loads were unloaded) was 19.57 Hz. Although the difference in frequency value is not significant, the decrease in frequency value indicates the presence of fine cracks in the beam. The cracking occurred when the beam was loaded with a 4.5-ton actuator that reached a deflection of 5 mm. This is evidenced by the comparison of mass and frequency assuming the same stiffness value. When given an actuator load, the microcrack is open, after releasing the actuator load the microcrack is closed again by the influence of the prestressing force. From the calculation of the load rating on the bridge, a rating factor (RF) of 1.16 (>1) is obtained, which indicates the condition of the bridge is safe and feasible to operate.

Kata Kunci : Prategang, Frekuensi, Lendutan, Microcrack, Rating factor

  1. S1-2024-456358-abstract.pdf  
  2. S1-2024-456358-bibliography.pdf  
  3. S1-2024-456358-tableofcontent.pdf  
  4. S1-2024-456358-title.pdf