Keywords: semi-rigid joint, reliability, advanced first order second moment method, Monte Carlo simulation, probability of failure, reliability index.

One of the possibilities of improving the accuracy of structural analysis is to evaluate the actual behaviour of joints. For these purposes the semi-rigid joint concept was introduced. The most relevant influence on the rigidity of the joint is produced by bending moments. In this case the behaviour of a semi-rigid joint is described by the moment-rotation curve of the joint. The joints are also influenced by axial and shear forces. These forces are not usually evaluated in calculating the rigidity and strength of the joints [1].

For typical structural systems, a failure state is defined as the formation of an unstable collapse state under some applied loads. The objective of this study is to propose the reliability analysis which can evaluate the probability of failure and the reliability index of steel frames with connections. In addition, the equation which represents the limit state of steel frames is investigated. In this study, the moment-rotation relationship of connections is formulated by the power model that has three parameters such as the initial stiffness, the ultimate moment capacity and the shape coefficient of the connection.

In order to calculate the probability of failure and reliability index of steel connections, an advanced first order second moment method and the Monte-Carlo method using an inverse transformation method are adopted. A strength limit state equation is presented for the reliability analysis of steel beams. For the purpose of reliability analysis, the advanced first order second moment (AFOSM) method is used here. The AFOSM method is one of Level II methods [2]. It makes the limit state equation become a first or second order function. And then by using a probability density function it can calculate the reliability index concerned with probability of failure. This proposed method is enough to include all types of connections.

To investigate the effect of the reliability index of three parameters according to each connection type, one parameter changes a random variable and two parameters are fixed. There random variables are systematically selected for three parameter , , , then a coefficient of variation is changed to 4%, 6%, 8%, 10%. In order to verify the proposed method, the reliability analysis, the errors of probability of failure using Monte Carlo method and the AFOSM are calculated.

1

A.M. Hasofer and N.C. Lind, "Exact and invariant second moment code format", Journal of Engineering Mechanics, 100(1), 111-121, 1974.

2

N. Kishi and W.F. Chen, "Moment-rotation relations of semi-rigid connections with angles", Journal of Structural Engineering, 116(7), 1813-1834, 1990. doi:10.1061/(ASCE)0733-9445(1990)116:7(1813)

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