2012 Volume 61 Issue 7 Pages 263-268
In the port of Kamsar, the PW method has been used for assessing the repair methods of the structure. The assessment requires cashflow data, which should normally include costs and incomes. If all the costs and incomes in a cashflow are discounted to their PW values using the chosen discount rate (r) and then summed, the result is the PW value of the cashflow. And there are some variations of the PW equation corresponding to the costs and incomes in a cashflow.
In accordance with the relationships between discount factors and time for different rates, it is supposed that the future is too uncertain to justify costing beyond 30 years. In practice, the lives of concrete bridges have to be significantly longer. For this problem, a tapering discount rate has been proposed which may be 8% up to 20 years but thereafter it tapers linearly down to 3%.
In this paper, the variations of the PW equation, the terms on the PW, and the application of a tapering discount rate to the port structure in Kamsar are shown.