Prop calculation
Ceiling jacks are the most suitable and economical means for the implementation of concrete slabs and joist blocks, which are produced at heights of 3 to 4.5 meters and are made of first-class pipes of 5 and 6 centimeters in diameter, which also have holes for height adjustment.
Prop made from two part that adjustable in length, up and down parts. The lower part is made of tube with a diameter of 60 mm and thickness is 2.5 mm. the upper part is made of tube with a diameter 50 mm and thickness is 2.5 mm too. For example if the height of the prop is 3.5 meter, the design is as follows
For safety in design, you can use tube with a diameter of 50mm:
For slenderness ratio of 195, the allowable stress is:
For safety the end of prop must be fixed. There are many reports on formwork failure as result of out of alignment of props during concrete pouring. By using prop brace, you can decrease unbraced length and increase allowed stress and loading capacity of props.
In the first example if you brace the prop in the middle, the slenderness ratio will change to 97 and allowed stress will increase to 904 kg/cm2.
Finally the loading of capacity will increase to 3.5 ton. So, in here if you brace the prop in the middle of the length, the loading capacity of the prop will be more than twice.
Accordingly, you can calculate allowed load for props with different lengths.