Modular steel scaffolds are commonly used as supporting scaffolds in building construction. They are highly susceptible to global and local instability, and traditionally, the load carrying capacities of these scaffolds are obtained from limited full-scale tests with little rational design. Structural failure of these scaffolds occurs from time to time due to inadequate design, poor installation and over-loads on sites. Initial geometrical imperfections are considered to be very important to the structural behaviour of multi-storey modular steel scaffolds. This paper presents an extensive numerical investigation on three different approaches in analyzing and designing multi-story modular steel scaffolds, namely, a) Notional Load Approach, b) Eigenmode Imperfection Approach, and c) Critical Load Approach. It should be noted that all these three approaches adopt different ways to allow for the presence of initial geometrical imperfections in the scaffolds when determining their load carrying capacities. Moreover, their suitability and accuracy in predicting the structural instability of typical modular steel scaffolds are presented and discussed in details
