EXPERIMENTAL STUDY ON LOAD CAPACITIES OF ISOLATED HEAVY-DUTY SCAFFOLDS USED IN CONSTRUCTION

摘要

The isolated heavy-duty scaffolds, which have higher load capacity, are often considered to serve as the falsework during the construction stage of a building with high clearance, large spans and thick slabs in order to meet the load demand of the building. Because isolated heavy-duty scaffolds serve as temporary structures and are promptly dismantled after the construction is complete, their importance is often neglected. Until now, data regarding the structural design of isolated heavy-duty scaffolds has been rather scarce, and the assembly of isolated heavy-duty scaffolds on construction sites still relies mainly on the experience of construction workers. This phenomenon results in a high risk of collapse of isolated heavy-duty scaffolds actually applied on construction sites. This study explores the critical loads and the failure modes of isolated heavy-duty scaffolds in various setups by testing actual setups of isolated heavy-duty scaffolds on construction sites. The results show that, since the bending moment stiffness provided by the base screw jacks of isolated heavy-duty scaffolds is negligible, the base screw jack has a limited effect on the overall load capacity of isolated heavy-duty scaffolds. When isolated heavy-duty scaffolds are set up on ground with varying elevation or on ground under an inclined top slab with varying elevation, their load capacity is not substantially affected as long as the difference in elevation is less than 56 cm. When assembled in multiple layers on construction sites, isolated heavy-duty scaffolds are often erected with steel tube shores on the top layer. However, this combined scaffolding structure reduces the load capacity of isolated heavy-duty scaffolds by as much as 70%. In this case, directly extending the top screw jacks of the isolated heavy-duty scaffolds is better than using a combined scaffolding structure. As for the isolated heavy-duty scaffolds after being repeatedly used, this study uses a repeated loading test to simulate the lower bound strength of isolated heavy-duty scaffolds on construction sites. Contractors can choose an appropriate reduction factor based on cost and construction safety considerations when engineers design the strengths of reusable isolated heavy-duty scaffolds.