After a resounding success at highway S3 construction in 2016, the prefab highway construction method has now just one year later, been established as Shanghai’s new normal. Construction work on the S7 highway was turbo charged to completion at the same hair-raising speed as the S3.
 


Shanghai has taken pre-fabrication of highways to the hilt: all columns, cover beams, and girders are produced offsite in a manufacturing plant 10km away from the building site. Compared to traditional construction methods project completion times are halved. Producing all concrete components offsite in a controlled manufacturing environment, also means less pollution from temporary work-stations. Mud, dust, and sound pollution are all greatly reduced.

Step 1: Foundations

The most critical foundations, where the S7 highway crosses the S20 and S6 highways, are built with permanent steel foundations. In the spots where the S7 traverses the S20 and S6, damage to adjacent foundations and disruption to traffic are intolerable. The Shanghai Greenland Construction Group used a resonance free hammer for the foundations of these piles. The RF hammer has a frequency that far exceeds the natural frequency of the soil and the elevated highways. This ensures that the existing structures are wholly unaffected by the construction work. Greenland drives the piles in two sections, welding the second section after the first has been driven. The pile is driven free hanging from a crawler crane without the use of a positioning frame. The verticality of the pile is monitored by a theodolite and corrected by the movement of the boom by the crane operator. The driving speed is exceptionally fast, under ten minutes for each pile; this meant the 128 piles were easily completed within a month. For each pillar foundation twelve 55m long, 700mm diameter steel casings are vibrated into the soil with a 70RF resonance free vibratory hammer. The top 5 meters of soil in each casing is removed to insert rebar that connects to the column support.
 


Foundations further away from existing structures are made with PHC piles. For the S7 project diesel hammers were used for these 1200mm diameter PHC piles, but in future highway projects when the highway moves closer to urban centers a 14NL impact hammer will be a much more suitable choice. The 14NL hammer has a higher daily production rate, is quieter and has no diesel particulate pollution. It can be operated free-hanging from a crane and can be powered by the same power pack used for the resonance free vibratory hammer.

 
Step 2: installing the pillars

The pillars are lifted on the steel connectors on the foundation platform, the connections are filled with grout which anchor the column to the foundation.

 
 
Step 3: lifting the girders

The girders are lifted on the pillars and the ribs are installed, typically one rib for each traffic lane.

 

This production line type construction method is the future of bridge construction. The streamlined building process improves efficiency, saving construction cost, and shortening completion time, while also ensuring stringent environmental targets are met. ICE’s vibratory and impact hammer equipment make a significant contribution to achieving Shanghai Highway Investments ambitious goals. Together with all stakeholders we are now working to introduce this construction method across China. Leave a message below or pick up the phone if you see opportunities in your area for the application of this technology!