Studi Numerikal Grup Fondasi Elevated Pile Cap Pada Tanah Pasir

Abstract

Abstrak

Elevated Pile Cap (EPC) merupakan fondasi tertanam sebagian di dalam tanah yang rentan terhadap beban gempa karena momen fleksural yang terjadi lebih besar daripada jenis fondasi yang tertanam sepenuhnya. Studi numerikal dengan metode BNWF menggunakan aplikasi OpenSees berbasis eksperimen yang dilakukan peneliti lain dilakukan untuk mempelajari perilaku non-linear fondasi di tanah pasir. Fondasi berkonfigurasi tunggal, 2x2, dan 2x3 dimodelkan dan divalidasikan terhadap penelitian tersebut. Variasi nilai densitas pasir dan pemberian nilai p-multiplier yang berbeda diperhitungkan per baris fondasi grup. Analisis pushover monotonik dilakukan untuk mengetahui perilaku ineastik fondasi. Semua model membentuk sendi plastis pada sambungan dan di bawah tanah pada tiang leading row. Perbandingan respons individu tiap tiang dengan respons rata-rata fondasi per tiang digunakan untuk mengetahui distribusi gaya pada fondasi yang dipengaruhi oleh nilai p-multiplier. Kuat geser tanah divariasikan untuk mengetahui keelastisitasan tanah saat pembebanan di titik tertentu, di mana semakin padat tanah maka semakin cepat fase plastis tercapai. Secara keseluruhan, variasi kepadatan tanah dan nilai p-multiplier mempengaruhi perilaku inelastis fondasi.

Kata kunci: EPC, fondasi grup, sendi plastis, p-multiplier, analisis pushover

Abstract

Elevated Pile Cap (EPC), a partially-embedded foundation, is vulnerable under seismic loadings since it suffers more flexural moment than average foundations. A BNWF numerical study was performed using OpenSees based on an experiment conducted in China. The 1x1, 2x2, and 2x3 rectangular EPC groups were modeled and validated by the test result. Each model is embedded in sand with a varied density and A different value of p-multiplier for each pile rows was considered. Monotonic pushover analysis was performed, and its inelastic behavior were investigated. All models suffer double plastic hinges on the leading row, located in connection and underground, depending on the soil density. The ratio of each pile row response to the average pile group response is an indicator to examine the forces distribution, influenced by p-multiplier only. The soil shear strength was investigated to observe the elasticity of soil when it reach its yield, ultimate, and the formed of plastic hinges. The p-multiplier and varied soil density affects the soil strength for pile rows, the denser the soil, the faster it reaches its plastic state. Overall, both p-multiplier and soil density affect inelastic behavior of foundations.

Keywords: EPC, group foundation, plastic hinge, p-multiplier, pushover analysis