A previous paper by Chan et al. (2000) reported a 3D finite element study investigating the effects of local impact between risers that can result from the movements induced by topside displacement, wave action, and vortex induced vibrations. This paper presents detailed results of finite element simulations of selected tests on bare-steel risers. An overview of the test programme (part of the NDP Riser Clashing Test Progranmle) consisting of eleven tests using bare steel riser sections and five tests using neoprene-coated risers carried out at the Impact Research Centre, Liverpool University, UK, is also presented. The finite modelling technique used was similar to that presented in Chan et aL (2000). The test conditions are shown to capture the localised effects of the impact between the risers and the F.E. modelling to be representative of the test conditions. The results showed very good agreement between the tests and the analyses and it was concluded that the F.E. analyses of Chart et aL (2000) are valid and can be shown to provide an accurate representation of the localised riser behaviour during impact events.
Depending upon the spacing between risers, clashing between them can result from the movements induced by topside displacement, wave action, and vortex induced vibrations. A 3D finite element study of two impacting risers (Chan et al. (2000)) was carded out using explicit dynamics and the behaviour established during the impact event, which is of the order of milliseconds. This behaviour was found to complex due to the coupling effect of the global and local impact responses, and the problem was simplified with a mathematical formulation for a beam-spring-beam model developed to describe the riser behaviour during the impact event.
