Mohaka Bridge Seismic Improvements
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Client: NZ Transport Agency
Location: Napier
Contract Value: $1.6m
Completed: Nov 2009
Main Contractor: Brian Perry Civil

 

Seismic strengthening to the Mohaka Bridge on SH5 on the Napier Taupo Road, 61 km's from Napier.  Work carried out included structural steel alterations, rock anchoring and soil nails to piers and abutments.  

Built in 1961 the bridge was found to be inadequate for the current seismic loading standards for bridges.  

The bridge was kept open at all times and work was completed within a nine month time frame.

Work Scope Included:

Structural Steel

Strengthening of various elements including piers, abutments, bearings and bracing horizontal and vertical.

Strengthening typically involved  removing existing connection plates, installing new connections, and stiffening of bracing by doubling elements, upgrading K bracing at abutments and piers.

Work was undertaken in a set sequence to ensure a balanced load path throughout the structure during construction, accessed from custom scaffolding.

Replacement of shear connections or "wind shoes" at the superstructure / substructure interface on all piers and abutments.

Ground Anchoring 

Abutment A (Napier side) was completely soil nailed and shotcrete to prevent failure during an earthquake. Work involved 59 soil nails up to 12m long with a total of 115 square meters of face shotcreted.

The Pier B (Napier side) pad foundation was strengthened by installing 12 rock bolts from an overhanging scaffold platform.