Excavations & Transfer Structures · 07

Ngabi Rongchu Bridge, Bhutan

A 120m long bridge with central arch span of 60m, was built using composite arch section. Being hollow and variable depth section as shown, the bottom and side walls of the hollow box used R&D based innovative site-produced/tested precast alphatruss avoiding costly forwork for the hollow box arch. One of the advantages of precast was to reduce the overall load on the temporary structures including tempoary foundations. For a 45m integral span PT varible depth twin box girder bridge over a river, design of tempoary work involved mainly the design of Belly bridge to bypass/divert the trafffic and design the support+scaffold system for the construction of the bridge girder+deck system. As can be seen, the scaffold system was supported by srong platform on large steel girders crossing the river below.