The presented problem consists in optimizing the pulling force of the luffing jib tower cranes, in order to reduce power and save energy by determining reasonable geometrical parameters such as placement of pulley assemblies, position of jib pin, and jib length. To determine the optimal parameters, a mechanical model was developed to calculate the pulling force of the research object. Then, the Taguchi method and Minitab software were applied to evaluate the influence of the parameters. The objective function was the minimum pulling force of the luffing jib. The calculation results show that the position of the pulley assembly used to pull the jib is the most influential factor on the objective function accounting for 81.15%, the less significant factors are the jib length, the pin position of the jib, and the pulley assembly that changes the direction of the load lifting cable. The result of the test presented in the article allowed for determining the rational parameters, and the optimal position of the pulley assemblies on the top of the crane. In the case of the pulley assembly located at the top of the crane, one obtains the optimal height of the crane head H≈0.4 L c.
In this study, we tried to understand the horizontal bearing performances of step-tapered piles using numerical simulations. The influence of the geometric parameters, e.g. the diameter (D) and the distance (L), and the length (H) of the pile were considered, and the soil distribution imposed on the horizontal bearing capacity of the piles was simulated. Numerical results show that when the other geometrical parameters of step-tapered piles are kept unchanged: (a) the increasing diameter (D) of the enlarged upper part of step-tapered piles improves the horizontal ultimate bearing capacity of step-tapered piles; (b) reduced distance (L) improves the horizontal ultimate bearing capacity of the step-tapered piles; (c) Increasing length (H) of the enlarged upper part of steptapered piles increases the horizontal ultimate bearing capacity; (d) the reduced length (H) decreases the bending moment of the pile body. Higher soil strength surrounding the enlarged upper part of step-tapered piles can increase the horizontal ultimate bearing capacity of step-tapered piles. The change of soil strengths at the end of the step-tapered piles does not influence the horizontal ultimate bearing capacity of step-tapered piles.
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