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Structures Design Office - 17th Street Causeway
Approach Slabs
Phase 1 West Approach Spans Phase 1
West Approach Spans		 Balanced Cantilever Method:
The method derives its name, "Balanced Cantilever", from the construction sequence. As shown in the figure below, construction starts by placing a pier segment on top of the pier.  This is followed by erection of the next two segments, one on either side of the pier segment. As the structure grows by placing one segment at a time on each side of the pier, a "balanced" cantilever is formed. This cycle is repeated until the cantilevers reach midspan.

Progressive Cantilever Method:
Since it was not practical to use Cantilever Construction off the back of the Carina Pier, temporary towers were placed in the waterway to prop the cantilever and allow for the completion of the span adjacent to the Carina Pier.
    The Progressive Cantilever Method consists of initially building part of  the span by the Balanced Cantilever Method. Then, once the cantilever exceeds half the previous span, a temporary tower or prop is added. Segments are added to the long span side of the pier with the temporary tower carrying the out of balance loads

 
Pier Segments built in halves to reduce lifting weight. Pier Segments built in halves to reduce lifting weights.
Phase 1West approach span from below Phase 1
West Approach
Lifting of Last Segment Cantilever prior to Closure Pour. Lifting of Last Segment Cantilever prior to Closure Pour.
View Looking East at Carina Pier #6. View Looking East at Carina Pier #6.
View shows temporary tower that will support Progressive Cantilever Construction.


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Balanced Cantilever Construction Method

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Progressive Cantilever Method