Parameter study of chain trenching machines of Underwater Construction Robots via analytical model
Analytical model by considering the kinematics, dynamics, and energetics of the trenching machine is adopted and proposed to design an underwater chain trenching machine at UCRC-KIOST. In this paper, parameter study and sensitivity analysis is conducted to show how the variations of operational and geometric parameters, as well as cutting tools and material condition affect the forces, moment, weight, and power components. The study sheds some important insights about how the trenching machine behaves and thus the information from this study can be used to design a trenching machine for the required working condition. The parameter study shows that minimum weight requirement for self-propelled vehicle is increased during operation at steep bar angle, and to keep the traction of the vehicle getting worst, it is recommended to cut the trench at low bar angle and make sure the cutting tool is still sharp. The results also show that traverse speed, cutting depth, uniaxial compressive strength, and trench width are the most sensitive parameters affecting the power and angular speed. On the other hand, weight of the vehicle, nose radius, bar length, and pivot point location does not affect the total chain power at all.
Prediction the Performance Rate of Chain Type Trenching Machine
The mathematical analysis for estimating the performance rate "RP" of chain-type trenching machine was studied. The mathematical analysis ended with an equation for this type. This mathematical equation was checked under different operating conditions. The practical study of the performance rate showed that the deviation of the theoretical performance rate from the actual performance rate ranged from -3.4 to +2% only for the 150.7 cm and 120.7 cm trench depth respectively. The machine field efficiency ranged from 46.7 to 57% for the 150.7 cm and 120.7 cm depth respectively. It also showed an increase in machine field efficiency by decreasing the trench depth.
Using Fuzzy-Delphi technique to determine the concession period in BOT projects
BOT projects are affected by several risks and uncertainties. One of the most important issues in this type of contract is to determine the length of concession period considering these uncertainties. The previous studies have developed several models to determine the concession period. However, the uncertainties are not taking into account in most of the previous works. Moreover, none of the previous researches has the capability to aggregate the opinions of different experts being involved in a project regarding the values of the uncertain input parameters. In this research, a Fuzzy-Delphi technique is implemented to determine the length of concession period considering uncertainties. Using the proposed Fuzzy-Delphi technique, the values of different uncertain factors affecting a BOT project is determined considering opinions of a group of experts. The NPV value is calculated considering the resulted aggregated values of uncertain input parameters. Finally, the concession period is determined using fuzzy approach. A case study is conducted to evaluate the performance of the proposed methodology. It is shown that the concession period is determined more effectively using the proposed approach.