Accidental impact is one of the main reasons causing failure of tubular structures in ocean engineering. Therefore, safety assessment of steel pipes subjected to impact loads is crucial to improving the safety of offshore structures that may frequently encounter impacts from berthing ships and dropped objects. Experimental study is carried out in this paper to investigate the dynamic responses of pipes under lateral impacts, by which the influences of impact location, impact energy and geometric parameters of pipes are analyzed. The upper surface profile and section shape are portrayed to clearly illustrate the deformation of a pipe. The obtained experimental results can be used as good references for the safe design of tubular structures.
Steel pipes are widely used in offshore engineering such as the brace members of offshore platforms and subsea pipelines for transporting oil and gas. Due to the complex ocean environment, pipes may be frequently subjected to accidental impact loads that may cause serious consequences such as contamination and property loss. There are data showing that the impact accidents account for 47% of all kinds of accidents on pipes (HSE, 2003). Jones et al. (1992) investigated the dynamic behavior of steel pipes subjected to transverse impacts based on the impact tests of a series of pipes. Brooker (2005) conducted quasi-static tests to investigate the influence of different shapes of indenters on the impact behavior of pipes. Pressurized submarine pipes are explored by Arabzadeh and Zeinoddini (2011) to study the dynamic response under lateral impact. Jones and Shen (1992) theoretically studied the lateral impact of fully clamped pipes based on their previous experimental results. Plastic analysis was made by Soares (1983) for pipes with different boundary conditions. Thomas et al. (1976) and Waston et al. (1976) divided deformation into three modes in different steps when subjected to transverse load, which makes the deformation phases more clearly. Dou and Liu (2014) provided a computational and analytical way to study the permanent deformation of pipes subjected to lateral impact load. Failure is another important problem of pipes, Dama et al (2007) mainly investigated the fatigue failure of pipes using experimental way and nonlinear finite element tools. Gresnigt et al (2005) focused on the dent of pipes which influenced by the internal pressure. One of the key points of those researches about dynamic or impact behavior of pipes is deformation mode. A suitable way to describe the deformation profile of pipes subjected to impact loads is significant to the industry. Both upper surface profile and section shape of pipes under impact loads are included in the present research. This paper introduces the experimental studies of the impact behavior of fully clamped steel pipes under lateral impacts. The impact test is carried out for five groups of pipes with different diameters using a wedged-shaped indenter. Different impact conditions are applied by changing the impact energy. The upper surface profile of pipes after impact is exhibited and some preliminary analysis of the deformation modes are made. Section shapes are portrayed and comparisons are made between the present results and those by Jones et al. (1992). At last, the permanent displacements at impact position for different impact locations are shown, which illustrates the influence of impact position on the rigidity of a pipe, and may be used as a reference in pipeline design. The purpose of this research is to investigate the deformation of a pipe subjected to lateral impact for better understanding of the dynamic response of pipes. Upper surface profile and section shape are portrayed according to the experiments results for clear illustration. The analysis is made to show the influence of impact energy on the deformation.
