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RISS 인기검색어
- 검색키워드
- 저자 : Seyed Hooman Ghasemi (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Reliability analysis of circular tunnel with consideration of the strength limit state
Ghasemi, Seyed Hooman,Nowak, Andrzej S. Techno-Press 2018 Geomechanics & engineering Vol.15 No.3
Probability-based design codes have been developed to sufficiently confirm the safety level of structures. One of the most acceptable probability-based approaches is Load Resistance Factor Design (LRFD), which measures the safety level of the structures in terms of the reliability index. The main contribution of this paper is to calibrate the load and resistance factors of the design code for tunnels. The load and resistance factors are calculated using the available statistical models and probability-based procedures. The major steps include selection of representative structures, consideration of the limit state functions, calculation of reliability for the selected structures, selection of the target reliability index and calculation of load factors and resistance factors. The load and resistance models are reviewed. Statistical models of resistance (load carrying capacity) are summarized for strength limit state in bending, shear and compression. The reliability indices are calculated for several segments of a selected circular tunnel designed according to the tunnel manual report (Tunnel Manual). The novelty of this paper is the selection of the target reliability. In doing so, the uniform spectrum of reliability indices is proposed based on the probability paper. The final recommendation is proposed based on the closeness to the target reliability index.
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Reliability index for non-normal distributions of limit state functions
Seyed Hooman Ghasemi,Andrzej S. Nowak 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.3
Reliability analysis is a probabilistic approach to determine a safety level of a system. Reliability is defined as a probability of a system (or a structure, in structural engineering) to functionally perform under given conditions. In the 1960s, Basler defined the reliability index as a measure to elucidate the safety level of the system, which until today is a commonly used parameter. However, the reliability index has been formulated based on the pivotal assumption which assumed that the considered limit state function is normally distributed. Nevertheless, it is not guaranteed that the limit state function of systems follow as normal distributions; therefore, there is a need to define a new reliability index for no-normal distributions. The main contribution of this paper is to define a sophisticated reliability index for limit state functions which their distributions are nonnormal. To do so, the new definition of reliability index is introduced for non-normal limit state functions according to the probability functions which are calculated based on the convolution theory. Eventually, as the state of the art, this paper introduces a simplified method to calculate the reliability index for non-normal distributions. The simplified method is developed to generate non-normal limit state in terms of normal distributions using series of Gaussian functions.
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Damage detection using both energy and displacement damage index on the ASCE benchmark problem
Mohammad Javad Khosraviani,Omid Bahar,Seyed Hooman Ghasemi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.2
This paper aims to present a novelty damage detection method to identify damage locations by the simultaneous use of both the energy and displacement damage indices. Using this novelty method, the damaged location and even the damaged floor are accurately detected. As a first method, a combination of the instantaneous frequency energy index (EDI) and the structural acceleration responses are used. To evaluate the first method and also present a rapid assessment method, the Displacement Damage Index (DDI), which consists of the error reliability (β) and Normal Probability Density Function (NPDF) indices, are introduced. The innovation of this method is the simultaneous use of displacement-acceleration responses during one process, which is more effective in the rapid evaluation of damage patterns with velocity vectors. In order to evaluate the effectiveness of the proposed method, various damage scenarios of the ASCE benchmark problem, and the effects of measurement noise were studied numerically. Extensive analyses show that the rapid proposed method is capable of accurately detecting the location of sparse damages through the building. Finally, the proposed method was validated by experimental studies of a six‐story steel building structure with single and multiple damage cases.
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Mohammad Javad Khosraviani,Omid Bahar,Seyed Hooman Ghasemi 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.2
This paper attempts to detect damage in the length of continuous deck bridges by providing new methods based on acceleration responses and their Instantaneous Amplitudes (IAs). The DD in this paper has two steps: firstly, determining the vicinity of damage in global damage detection; secondly, determining the location of damage in local damage detection. Then by acceleration signals, the IA values of healthy and damaged structural responses extracted using Hilbert-Huang Transform (HHT). Further, with the impression of the IA energy damage index (EDA), damage location is detected. Moreover, for the accurate evaluation of the proposed method, damage locations are determined using the cross-correlation damage index (CCDI). To assess the feasibility and reliability of the proposed methods, several analytical models of concrete bridges of one to three-spans, as well as experimental models of a simply supported steel beam, slab-on-girder composite bridge, and the UFC benchmark bridge are investigated. To consider noise pollution during data acquisition, a certain amount of noise is added to the response. The comparison of the obtained analytical results with the experimental ones showed that the proposed methods can determine the damage locations with appropriate accuracy for different damage scenarios. Also, the results of the CCDI index concluded to the acceptable exact results associated with a rapid estimation.
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