Experimental and analytical studies on steel scaffolds under eccentric loads

Steel scaffolds collapse quite often in many places with a considerable number of reported casualties, but their behaviour has not been studied to the extent of many other permanent structures. This paper investigates the effect of eccentric loads on steel scaffolding systems used in construction sites. The type of scaffold considered here is the door-shaped steel scaffold with an inner reinforced gable sub-frame. The single-side cross-brace scaffolding systems with various eccentric loads are mainly focused on two issues, namely, the unrestrained boundary and the removal of cross-braces at the access location. This study shows that regardless of the lowest layer of cross-brace in a scaffold being removed or not, the critical load of a scaffolding system under an eccentric load is the lowest, whereas that of scaffolding system under a concentric load is the maximum. If the bottom jack base of a scaffolding system in construction sites is strengthened to a fixed end, the critical load of this scaffolding system will be greatly increased. If a scaffolding system is erected more than 8 stories high, the critical load of the scaffolding system with the fixed end base can be increased to 2.4 times that with the hinged base. However, whether the cross-braces at the lowest story of a scaffolding system are removed or not, the simulated scaffolding test indicates that the critical load of a used scaffolding system under the eccentric load is the lowest and its load reduction also appears significant.