Critical Load of Strut Lab Work

Just like beams, strut and columns are also structural members but unlike beams, strut and columns are designed to take axial loads. 

Strut and column both are design to take axial load, difference between both of them is the length of each with respect to its cross section. 

If length of the member is larger as compared to the cross section then that member is called strut and when length of the member is short as compared to the cross section then that member is called column.

In both of the cases there is a particular load above which the strut and column will show some buckling that load is called the critical load. 

Critical load is the factor which influences the design of the strut and column. Critical load of strut and column can be calculated from the following formula made for a particular condition called both ends pined.

Critical load of strut and column can be calculated from the formula

How to calculate Critical load of strut and column

In order to find the critical load of strut with the help of beam bending apparatus following is the experimental procedure for that.

1. First of all setup the apparatus in vertical direction in such a way that when strut is attached to the apparatus its one ends hit the ground and other is free for weight edition. Dial gauge that was used to check the deflection of beam will now be used to check the buckling of strut

2. After the apparatus has been setup, now it is time to set the dial gauge for the test. In order to get buckling reading during the test, dial gauge is given some initial reading by compressing its tip against the surface of the column. Now when strut moves from its position, dial gauge will show some change is its initial reading and that reading will be deflection shown by the strut.

3. Third step is to add weight on the free end of the strut and note the reading of the dial gauge. Weight should be added slowing and in increasing order like 2, 3, 4, 5 …… Newton. Weight at which dial gauge show some noticeable change is reading will be the critical load for that strut.

4. Experiment should be repeated at last three times to get the best average value of critical load.