STRUCTURAL MEMBERS REQUIRED FOR TOP

STRUCTURAL MEMBERS REQUIRED FOR TOP-DOWN CONSTRUCTION
Design and construction principles for top-down method primarily call for two major structural elements.
· Columns with sufficient capacity must be pre-founded in bored piles or barrettes to sustain the construction load and to utilize as part of bracing system.
· Excavation for basement must be carried out with the support of permanent
retaining wall so that basement floor slabs can be utilized as lateral bracing.
Diaphragm wall of 0.8m to 1.2m in thickness with sufficient embedment in firm soil layers is commonly used as a retaining wall whereas prefabricated steel columns known as Stanchions embedded in either large diameter deep-seated bored piles or barrettes are utilized as structural columns. Figure 1 illustrates the top-down construction method with utilization of stanchions and diaphragm wall.