Doha's do-it-yourself tower crane

"Qatar is going through a major building project stage with some being commercial and some residential. In fact you could say the whole city is one big building site.

Most of the building workers are imports from countries such as India, Nepal, China, Vietnam, etc. The country is strictly Muslim.

There is no room for OH&S within the context as we here in Australia know it.

During my wandering around the various construction sites I saw some tower cranes that were acceptable within reason and some which would not make even basic standards.

I came across one of the latter erected on a government construction site where the building was for government use, the builder was a government department and the equipment was government-owned, according to a sign on the wall. The building was to be 12 floors and at my time of inspection was a messy three floors plus bits. As far as I could determine there would be no building ties.

The top section tower was angle iron maybe 200x200x20mm in the chord legs. Below the slew ring the tower was square hollow, maybe 200SHS. Further down, the tower was from circular tube and the tower sections were being manufactured on site.

I wrapped a shoelace around a bit of tube I could get at, tied a knot and when I got back home measured it and found the section to be 76mm in diameter by 4mm wall thickness. The boom is around 60m long and there is 10t of counterweight on the rear.

The major safety issue is from buckling collapse. First, the tower structure did not have adequate cross sectional properties to resist torsional buckling.

The driver also had to face danger twice a day. To leave the cabin, the crane operator climbed out of his front window and down the outside of the tower until he reached an internal
so-called ladder. In Australia, access into and from the crane follows such technical standards as ISO 11660-1.

During operation the stopping of the slew caused the tower to yaw in a big way - maybe 300mm. It was interesting to watch the tower movement, as it was consistent with the action shown by a frame analysis program when animated.

One leg of the middle tower appeared to have permanent distortion, but this was on the tension side hence it did not appear particularly relevant from ground level.

Given the condition of the crane and tower, the base supports are overkill in the extreme.

For all the faults in basic design, the crane worked well if we ignore things like fatigue, which was the other major safety problem. Every steel structure when cyclic loaded deflects or deforms while under load and then returns to its preloaded profile. Deflections are controlled with the elastic properties of the material from which it is manufactured. When the elastic property is continuously exceeded then fatigue will set in. Based on my experience, I believe that the deflections at least torsionally were excessive.

I did not have any discussions with site personnel but was told to stop taking photos and to leave the area, which for self preservation, I did with haste.”