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The most recent set of construction photos appear on the main Photo Album page.

January-March 2005: Pier 37, Bow-tie Strut Construction
As 2005 begins, Pier 37 is approximately 200 feet (61m) out of the water. The wooden forms at the tops of the tower legs are at the level where the "bow-tie" strut will be constructed.
The bottom half of the form used to create the strut sits on a barge, awaiting transport to Pier 37. The completed strut will measure 80 feet across, 22 feet wide, and 23 feet high at its tallest point.
The bottom half of the form for the bow-tie strut. Note the pitch of the floor, which comes to a point in the center of the form.
The form in place at Pier 37, supported by falsework (temporary) supports.
The form in place at Pier 37, supported by falsework (temporary) supports. Note the workers on scaffolding along the outer face of the form.
Workers begin preparations inside the form.
Workers begin preparations by stabilizing the form against the tower legs.
Workers begin to connect reinforcing steel that will join the tower leg to the bottom slab of the strut.
Workers begin to connect reinforcing steel that will join the tower leg to the bottom slab of the strut. Threaded steel rods are screwed into coupler inserts that were cast into the concrete tower leg. Ductwork for post-tensioned steel cable will be run through the larger holes.
Two mats of reinforcing steel are built across the bottom of the form. Silver ductwork for post-tensioned cable is visible within.
Reinforcing steel has reached the peak of the bow-tie, and is visible along the walls of the form. Silver ductwork for post-tensioned cable is visible in the steelwork.
Three sides of the box of steelwork reach completion inside the form. Silver ductwork for post-tensioned cable is visible along the floor. The concrete floor slab will be poured first, with the walls of the box formed next.
With three sides of the bow-tie box complete, concrete is placed to form the top slab.
With three sides of the bow-tie box complete, concrete is placed to form the top slab.
Workers prepare to push nineteen strands of 7-wire steel cable through the ductwork inside the completed strut.
Steel cable protrudes from ductwork in the bridge tower prior to post-tensioning.
Workers use a pneumatically-driven "strand pusher" to feed 19 strands of 7-wire cable through the ductwork. The worker on the right is holding a steel "bullet", which is attached to the end of each strand, allowing the cable to pass smoothly through the ductwork.
The 19 strands of cable are fed into individual holes within a steel "anchorage cylinder". Each cable end is fitted with a cone-shaped wedge, which grasps the cable and holds it firmly within the cone-shaped holes of the anchorage. The cables are then pulled to a pre-determined force of tension. This is the same method that will be used when steel superstructure is attached to the tower legs -- the cable-stayed design.
In the post-tensioning process, the steel cable is pulled to tension with a hydraulic jack. The inset photo shows the jack extending as it tensions the cable. Post-tensioning, along with the reinforcing steel, provides structural continuity and adds great strength and rigidity to the entire structure.
Engineers measure the extension of the cable. This strand of 19 cables was "elongated" approximately 7 inches (18cm), a predetermined specification. As force of tension is mathematically related to elongation, the tension/elongation required in various locations can be readily determined. After post-tensioning, grout is pumped into the cable ducts to prevent corrosion.
Workers stand atop the completed bow-tie strut.
Web cam view of the completed strut. The circle indicates locations where post-tensioning blockouts were filled in.
Late March 2005: Pier 37 with the completed bow-tie strut.
Late March 2005: Pier 37 (right) with the completed bow-tie strut. Construction on the strut for Pier 38 (left) begins in April 2005.