Cranes – Design, Practice, and Maintenance phần 8

Áp lực cho phép nhiệm vụ bình thường σ v G100 N mm2 - nặng nhiệm vụ σ v G85 N mm2 - Rất nặng σ v G70 N mm2 Đối với tải xen kẽ những con số này đã bị giảm đi 30%. D chi tiết thiết kế công trình xây dựng đang được tiếp xúc để tải mệt mỏi thường có thể tránh được một số chi tiết thiết kế để ngăn chặn các vết nứt mệt mỏi. Những con số sau đây cung cấp cho một số những chi tiết này | Construction and Calculation Methods 225 LOADING SPECTRUM The loading spectrum characterizes the magnitude of the loads acting on a mechanism during its total duration of use. It is a distribution function summed y f x expressing the fraction x 0 x of the total duration of use during which the mechanism is subjected to a loading attaining at least a fraction y 0 y 1 of the maximum loading see Fig. . Table Spectrum classes Symbol Spectrum factor km L1 km L2 km L3 km L4 km GROUP CLASSIFICATION OF INDIVIDUAL MECHANISMS AS A WHOLE On the basis of their class of utilization and their spectrum class individual mechanisms as a whole are classified in one of the eight groups M1 M2_M8 defined in Table . Table Mechanism groups Class of Class of utilization load spectrum T0 T1 T2 T3 T4 T5 T6 T7 T8 T9 L1 M1 M1 M1 M2 M3 M4 M5 M6 M7 M8 L2 M1 M1 M2 M3 M4 M5 M6 M7 M8 M8 L3 M1 M2 M3 M4 M5 M6 M7 M8 M8 M8 L4 M2 M3 M4 M5 M6 M7 M8 M8 M8 M8 GUIDE FOR GROUP CLASSIFICATION OF INDIVIDUAL MECHANISMS AS A WHOLE Guidance for group classification of an individual mechanism as a whole is given in Table . Since appliances of the same type may be used in a wide variety of ways the grouping directions in this table can only be taken as a model. In particular where several groups are shown as appropriate to a mechanism of a given type it is necessary to ascertain on the basis of the mechanism s calculated total duration of use and loading spectrum in which class of utilization see and spectrum see it has to be placed and consequently in which group of mechanisms see . 226 Cranes-Design Practice and Maintenance Table Guidance for group classification of a mechanism Ref. Types of appliance Particulars concerning . nature of use 1 Type of mechanism Hoisting Slewing Luffing Traverse Travel Designation 1 Hand-operated appliances M1 M1 M1 2 Erection .