Experimental Compression Tests on the Stability of Structural Steel Tabular Props

Experimental studies are presented in this paper on the stability of structural steel props. Three full-scale prop specimens with various geometric properties were constructed and tested statically and elastically in the lab, in order to obtain the elastic strength of the props. The total unsupported length is 6 m for the three props. The outer and inner diameters are 150 mm and 140 mm, 138 mm and 132 mm for the outer and the inner lengths, respectively. Each specimen consisted of two pipes, one sliding inside the other for a certain length, and tightened together by three 20 mm bolts. Three different (outer, inner and inserted) length combinations were tried in order to maximize the elastic buckling capacity of the whole prop. The three props were loaded up to elastic buckling using R.SM/RCS flat jack cylinders with 30 tons (295 kN) capacity. Based on the experimental results, it can be concluded that the typical failure mode of steel prop is the elastic global buckling. The elastic buckling strength of the prop was found to be sensitive to the inserted length of the upper pipe. The prop buckling capacity increases with increasing the inserted length.