Analysis of field applicability of the rotation-controllable tower-crane hook block

Abstract

Abstract The rotation-controllable tower-crane hook block can control the horizontal rotation angle of a steel beam being lifted by a tower crane using a mechanical apparatus. It is expected that the mechanized hook block can relieve safety concerns; however, at the same time, there are several concerns: Is precise control of the rotation angle possible? Won't it be slower than rotating a beam by hand? If a mechanized system is faster, how fast is it? In order to test these, experiments were conducted. The precision of the rotating angle and the time for rotating and stopping the rotation controllable hook block were measured using an orientation sensor and a laser point. The results were compared to those of the conventional manual method. Since a steel beam usually has a symmetrical shape, π/2 rad (= 90°) is the maximum angle for placing a beam in the target location. The experiment results showed that a steel beam stopped after it moved 7π/600 rad (= 2.1°) and 9π/200 rad (= 8.1°) more, on average, due to inertia when the steel beam was rotated π/12 rad (= 15°) and π/2 rad (= 90°), respectively. However, it appeared that when an operator became used to the remote controller, the operator could reduce the rotation speed to stop a steel beam in the target location by reversing the motor direction. In terms of time, it took 5.80 s, 8.69 s, and 17.12 s, on average, to rotate a steel beam π/12 rad (= 15°), π/4 rad (= 45°), and π/2 rad (= 90°), respectively. The time for rotating steel beams using the conventional manual method at a construction site was also measured for comparison. The rotation time using the conventional manual method ranged from 11.96 s to 91.00 s depending on how easy it was for workers to reach and rotate a beam because workers rotate beams while hanging on a column. The results showed that the deviation could be reduced and work efficiency could be improved when a mechanized hook block is adopted on a construction site.