Construction of highway bridges was the principal task in this project.  The North Contract consisted of a 2.7 km long dual 3-lane viaduct. The application of the precast segmental method proved to be efficient and effective.  In the South Contract the Yau Ma Tei interchange, which is one of the most complicated grade-separated interchange in Hong Kong, was successfully constructed by means of conventional in situ method.

Pier and Abutment

The expressway decks are supported by a series of T-shape concrete columns sitting on the pile caps supported on bored piles or barrettes.  Some columns are offset from the positions directly below the deck box spine, in areas where access ramps are located or where the LAR tracks emerge from beneath the deck.  Where the offset is small, the deck is supported by a special column head arrangement offset on a single column.  Where the offset is great, a portal arrangement is used with the deck on a cross beam supported by two discrete columns straddling the obstruction.  In view of the LAR trains run near the columns, the columns are protected by reinforced concrete deflectors to minimize the impact in case of any derailment. 

The piers and abutment were construction in situ using grade 40/20 concrete.  To commence the construction of a pier, a scaffold-working platform was erected prior to the reinforcement installation. The platform facilitated the installation work and helped to maintain the rigidity of the reinforcement.  Drainage down pipes, services ducts and box-outs were installed and reserved where required.  The formwork was pre-assembled into several panels before erecting it in position.  The verticality was checked regularly during the erection.  Concrete was placed in layers by a crane and skip with assistance of chutes to control the free fall height of the concrete.  Compaction was maintained throughout the concreting work.  Sufficient time was allowed for curing before removing the formwork.  Bearing plinths were cast on top of the column heads to support the bearings.  They were cast after the column heads and were finished to ensure that accurate set-out could be achieved.  In the construction of an abutment, the outside formwork of the abutment wall was erected prior reinforcement installation.  Remaining formwork was erected after reinforcement had been installed.  The construction sequences are similar to the construction of piers.

Bridge Deck

Construction of decks started after the piers were completed.  Precast segmental method was utilized for the construction of the elevated viaduct.  Other bridge structures were constructed in situ using standard falsework and formwork.  Most of the decks were of pre-stressed concrete single or multi-cell box type.