| 摘要 |
PROBLEM TO BE SOLVED: To prevent moving of a suspended cargo in a dynamic lift off of lifting the suspended cargo or when placing down the suspended cargo. SOLUTION: A jib 18 having a truss structure has an upper chord member 20 protruding toward an upper side and a lower chord member 21 protruding toward a lower side with respect to a load acting line 19 connecting a hoisting point 14 and a support pin 6. The jib 18 is supported so as to allow derricking by a derricking rope 8 attached to a longitudinal intermediate part. A cross-sectional area Au of the upper chord member 20 and a cross-sectional area Al of the lower chord member 21 are determined in accordance with a protruding eccentricity length Eu of the upper chord member 20 and a protruding eccentricity length El of the lower chord member 21 with respect to the load acting line 9 so that an upper part of the jib 18 is bent back toward a crane body side when hoisting a maximum load.
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