14. Selection and estimate of freight–catching devices
Selection of slings and other gripping equipment is implemented for each structural element of the building. One kind of the sling should be used for different types, but similar in size constructions of different weight characteristics.
Calculation of the selected sling length and selection of ropes diameter to be carried out for the greatest structural element of the group per the weight and dimensions for the of which will be used lifting slings.
Calculation of the slings is based on the breaking load and the selection of cable diameter according to the current GOST.
To be find the force (in kg) that occurs in one branch of sling:
S=(Q/cosα)K
where, 𝛼 – vertical deviation angle of the sling, no more than 45°;
Q– weight of lifted structures (3÷5 t);
m – number of sling branches (2 or 4);
K – factor of load unevenness to the sling branches (m<4 is taken, K = 1, with m≥4 K= 1,33),
Breaking strength in the sling branches is determined:
P=S Sf
where, Sf– safety factor, taken as Sf = 6
– for slings with inventory lifters, Sf =
стропов с инвентарными грузозахватами, Kз = 8 – для стропов с креплением груза обвязкой.Пользуясь таблицами ГОСТ 3079–80, для стальных канатов подбирают диаметр троса по разрывному усилию.
Проектирование производства бетонных работ
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