Keandalan Menara Televisi Rangka Baja Akibat Beban Gempa
DOI:
https://doi.org/10.5614/jts.2017.24.3.5Keywords:
Fungsi distribusi lognormal, kurva fragilitas, menara televisi, rangka baja, resiko keruntuhan, teori probabilitas total.Abstract
Abstrak
Perencanaan struktur menara telah bergeser dari konsep equal hazard menjadi konsep equal risk, dimana semuabangunan dirancang untuk mempunyai tingkat kegagalan atau risiko yang sama nilainya, dalam hal ini 1% dalammasa layan 50 tahun. Berkembangnya konsep ini disebabkan bahwa struktur menara televisi yang dirancangdengan konsep equal hazard ternyata mempunyai tingkat risiko yg tidak sama yang disebabkan oleh variabilitasdari tahanan menara terhadap gempa. Variabilitas kapasitas menara terhadap gaya gempa dipengaruhi olehvariasi gaya gempa yang bekerja yang dikenal sebagai record to record variation. Dalam makalah ini disampaikanmodel probabilitas untuk menghitung tingkat keandalan menara terhadap gaya gempa, dengan mengkombinasikankurva hazard dan kurva fragilitas struktur menara. Kapasitas menara atau kurva fragilitas didapatkan denganmencari peak ground acceleration (PGA) collapse dari menara dengan menggunakan incremental nonlinear timehistory analysis dari 40 pasang data time history. Reliability atau keandalan menara diperoleh denganmemanfaatkan total probability theorem yaitu dengan melakukan proses risk integral antara kurva hazard dankurva fragilitas.
Abstract
The new earthquake design code emphasizes on uniform risk concept at every structure and every location which is1% probability of collapse in 50 years, as stated in SNI 1726-2012. Indonesian television tower design, until thisresearch is conducted, still uses the concept of uniform hazard ground motion, sample tower that is assessed in thisresearch included. This research will assess probability of collapse of the sample tower as well as it's performance.Probability of collapse is calculated by risk integrating fragility curve from two different loading direction andhazard curve at the site. The result will then be summarized with the probability of each loading direction includedto get the total probability of collapse in 50 years. Fragility curve is generated by Incremental Dynamic Analysisprocess of 40 different earthquake records. The measured intensity is determined as PGA. The fragility curve iscalculated with lognormal distribution parameters of median ( ) and standard deviation (β) which are obtainedfrom the PGA data set of IDA result.
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