Reliability based design optimization of foundations and reliability based design of shallow foundations considering earthquake loading in cohesionless soils

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Thesis Type: Doctorate

Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, -, Turkey

Approval Date: 2012

Thesis Language: Turkish

Student: ERHAN TEKİN

Co-Supervisor: SAMİ OĞUZHAN AKBAŞ, NAİL ÜNSAL

Open Archive Collection: AVESIS Open Access Collection

Abstract:

In this thesis, reliability based design optimization of shallow foundations, drilled shafts and reliability based design of shallow foundations considering earthquake loading in cohesionless soils were studied. Defining geotechnical analysis parameters, typical values of them were summarized and relationship between each other was investigated. Traditional bearing capacity and settlement methods were examined for ultimate limit state and serviceability limit state. Considering the limited success of traditional bearing capacity and settlement methods new bearing capacity and settlement methods were developed with artificial neural networks. Presenting statistical background information which is necessary for reliability-based design, First Order Reliability and Monte Carlo simulation methods were explained. Literature survey was conducted to determine typical uncertainties of geotehnical variables. The basic aim of reliability based design is to calibrate the load and resistance factors in some simplified design formats until a selected target reliability index is achieved. In this aspect, The Load and Resistance Factor Design format was selected to calibrate shallow foundations under seismic loading. For ultimate limit state, choosing target reliability index of 2.3, resistance factors were evaluated using first-order reliability method considering shallow foundations subjected to seismic loads. Deterministic optimization of shallow foundations subjected to compression, seismic loading and drilled shafts subjected to uplift, compression loading were carried out. Realibility based design optimization studies were investigated using load resistance factor design (LRFRBDO) and genetic algorithm (GABRO). Relibility based design optimization of shallow foundations subjected to compression, seismic loading were studied using LRFRBDO, GABRO and drilled shafts subjected to compression, uplift loading were computed using LRFRBDO. In optimization based design, sensitivity study was carried out by considering effects of elastic modulus, effective internal friction angle, vertical load, unit weight of soil, factor of safety, maximum allowawed displacement, and unit price variables on the construction cost. Deterministic and reliability based design optimization results were compared.