Life Cycle Costs

Abstract

In December 2002 the highly innovative inflatable storm surge barrier near Kampen in the Netherlands was finished. This Ramspol barrier (named after the small villages next to it) has to protect the area surrounding the "Zwarte Meer" during north-western storms. These storms result in water setup that can cause severe problems for the very low area in the Eastern part of the Netherlands. One of the reasons to build an inflatable barrier instead of a more traditional barrier, amongst others reasons, was that it was expected to be an economically preferable solution. No real proof for this claim exists until now. This thesis focusses on a Life Cycle Cost (LCC) comparison between inflatable barriers and 'traditional' vertical lifting gate barriers. This means that all costs that occur during the lifetime of the barriers are taken into account. During this thesis a case study has been performed for the location of the Hartel barrier near Spijkenisse in the Netherlands. An inflatable barrier based on Ramspol has been designed for that location with the same requirements that hold for the original Hartel barrier. Based on this design the construction costs have been determined for such a barrier and these have been compared to the construction costs for the original barrier. Then maintenance strategies based on decompositions for both types of barriers have been determined in order to predict and calculate the expected maintenance costs in a deterministic way. In order to increase the reliability and get an insight in sensitivities a sensitivity analysis has been performed by making use of a Monte Carlo simulation. This provides results with a 5%, 50% and 95% confidence level. The LCC costs for both barriers are compared and checked with the deterministic results. Since this thesis is about a LCC comparison between the general types of barriers some general aspects, e.g. the influence of gate length, water depth, ship collision, etc., have been investigated. This is done mainly in a qualitative manner due to time considerations. The possible effects of the phenomena on both types of barriers are studied per phenomenon. These results are linked to the case study results and combined. The most important conclusions that follow from this thesis are: • For an inflatable barrier at the Hartel location both the construction- and the maintenance costs are lower compared to the original vertical lifting gate barrier. Over the total life cycle a cost reduction of about 20% could be achieved. The LCC with a 95% confidence level (upper bound) for the inflatable barrier is still about €9 million less lower than the LCC for the original barrier with a confidence level of 5% (lower bound). • In general can be said that inflatable barriers appear to be economically (and structurally) preferable when barriers are required with increased gate lengths or in deeper water. Furthermore, the design of inflatable barriers can possibly be improved by leaving out the abutments or by making it adaptable for increased water levels. This options increase the number of applications for inflatable barriers. • Based on the findings of this thesis the scores for inflatable barriers in a comparison between storm surge barriers is updated. Based on this updated comparison can be said that inflatable barriers should be considered as a serious option for almost all circumstances.