Probabilistic Modeling of Updating Epistemic Uncertainty In Pile Capacity Prediction With a Single Failure Test Result
DOI:
https://doi.org/10.5614/jts.2017.24.3.1Keywords:
Axial pile capacity, bayesian theorem, epistemic uncertainty, factor of safety, model error.Abstract
Abstract
The model error N has been introduced to denote the discrepancy between measured and predicted capacity of pile foundation. This model error is recognized as epistemic uncertainty in pile capacity prediction. The statistics of N have been evaluated based on data gathered from various sites and may be considered only as a general-error trend in capacity prediction, providing crude estimates of the model error in the absence of more specific data from the site. The results of even a single load test to failure, should provide direct evidence of the pile capacity at a given site. Bayes theorem has been used as a rational basis for combining new data with previous data to revise assessment of uncertainty and reliability. This study is devoted to the development of procedures for updating model error (N), and subsequently the predicted pile capacity with a results of single failure test.
Abstrak
Rasio antara kapasitas aksial pondasi tiang yang diukur melalui percobaan uji beban dengan kapasitas yang dihitung melalui formula dapat dianggap sebagai model error N yang menggambarkan kesalahan epistemic dalam perhitungan pondasi tiang. Data statistik N yang diperoleh dari berbagai lokasi dapat dianggap sebagai kecendrungan umum kesalahan (general error trend) yang melekat pada formula yang digunakan. Hasil percobaaan beban pada lokasi tertentu dimana bangunan terletak harus menjadi indikator langsung akan variasi kapasitas aksial tiang pada lokasi tertentu. Pada studi ini model error awal sebagai nilai kecendrungan umum dapat di update melalui kerangka teorema Bayes. Pengaruh kesalahan akibat friksi dalam alat tekan hidrolik disertakan dalam formulasi. Statistik nilai N yang baru dapat digunakan untuk menentukan kapasitas tiang ataupun angka keamanan yang dipakai dalam perencanaan untuk mencapai target keandalan tertentu.
References
American Petroleum Institute, 1984, Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platform, API RP 2A, January.
Ang, A.H-S., and Tang, W.H., 1975, Probability Concepts in Engineering Planning and Design, Vol. I - Basic Principles, John Wiley, New York.
Ang, A.H-S., and Tang, W.H., 2007, Probability Concepts in Engineering, Emphasis on Applications to Civil and Environmental Engineering, John Wiley, 2nd Edition, New York.
Coyle, H.M., and Sulaiman, I.H., 1970, Bearing Capacity of Foundation Piles: State of the Art, Pile Foundations, Highway Research Record, No. 333, pp. 87-102.
Fellenius, B.H., 1984, Ignorance is Bliss and That is Why We Sleep So Well, Geotechnical News, Vol. 2, No. 4, December, pp. 14-15.
Kay, J.N., 1976, Safety Factor Evaluation for Single Pile in Sand, Journal of the Geotechnical Engineering Division, ASCE, Vol. 102, No. GT10, October, pp. 1093-1108.
Madhav, M.R., and Arumugam, A., 1979, Pile Capacity - A Reliability Approach, 3rd International Conference on Application of Statistics and Probability in Soil and Structural Engineering, Proceedings, Jan. 29 - Feb. 2.
Moses, F., 1979, Bayesian Calibration of Platform Reliability, Specialty Conference on Probabilistic Mechanics and Structural Reliability, Proceedings, Tucson, Arizona, January 10-12, pp. 219-223.
Olson, R.E., and Dennis, N.D., 1982, Review and Compilation of Pile Test Results, Axial Pile Capacity, Geotechnical Engineering Report, CR83-4, Department of Civil Engineering, University of Texas, Austin, December.
Tang, E.H., 1971, A Bayesian Evaluation of Information for Foundation Engineering Designaa, 1st International Conference on Application of Statistics and Probability to Soil and Structural Engineering, Proceedings, Hong Kong, pp. 173 - 185.
Tang, W.H., 1981, Updating Reliability of Offshore Structures, Symposium on Probabistic Methods in Structural Engineering, Proceedings, St. Louis, Missouri, October 26-27, pp. 139-156.
Tang, W.H., and Ang, A.H-S., 1973, Modeling, and Updating of Uncertainties, ASCE National Structural Engineering Meeting, April 9-13, San Fransisco, California.
Tang, W.H., and Sidi, I., 1984, Random Field Model of a Two-State Medium, Probabilistic Mechanics and Structural Reliability, Proceedings, 4th ASCE Specialty Conference, January 11-13, Berkeley, California, pp. 210-213.
Sidi, I.D., 1986, Probabilistic Prediction of Friction Pile Capacities. Ph.D. Dissertation submitted to Civil Engineering Department, University of Illinois at Urbana Champaign.
Vanmarcke, E.H., 1977, Probabilistic Modeling of Soil Profiles, Journal of Geotechnical of Engineering Division, ACSE, Vol. 103, No. GT 11, November, pp. 1227 - 1246.
