Three-dimensional joint flexibility element for modeling of tubular offshore connections

In tubular joints of offshore platforms, joints may exhibit considerable flexibility since the materials in the chord members near the intersection zone of brace–chord behave as shell-like structures. The resulting flexibility may have significant effects on the local and overall behavior of offshore platforms. This study describes the derivation of a three-dimensional joint flexibility element which is based on physical interpretation of behavior of a tubular joint upon deformation. The element is developed on the basis of flexibility matrix and implemented in a finite element program to account for local joint flexibility effects in numerical models of jacket-type offshore platforms. Results are validated by more sophisticated multi-purpose software and compared against conventional rigid-joint models which are widely employed in practice. According to the results, the accuracy of response predictions is improved when the effects of joint flexibility are considered. This model can be used for predicting more accurate response of jacket-type offshore platforms.