Third Tacoma Narrows Suspension Bridge - Under Construction
This is an image set within the Bridgemeister collection.
| Bridge: | Third Tacoma Narrows Suspension Bridge - Under Construction |
| Location: | Tacoma and Gig Harbor, Washington, USA - Puget Sound |
| Coordinates and Maps: | See related inventory record(s). |
| Image Set Contributor: | Patrick S. O'Donnell |
| Related Suspension Bridge Inventory: | 2007 Third Tacoma Narrows - Tacoma and Gig Harbor, Washington, USA |
| Related Image Lists: | All from Patrick S. O'Donnell All in Washington All in USA All Vehicular Suspension Bridges |
| Credit: | All photos by Patrick S. O'Donnell. Please do not reuse without permission. |
Patrick's comments accompany his photos.
"I visited the existing (1950) and new currently under construction Tacoma Narrows Bridges on a late Sunday afternoon. I walked across the existing bridge accessing from it the western end (Gig Harbor) via the southern bicycle and pedestrian way. This would provide the best viewing platform. The temporary detour of the bicycle path across the nearly completed lanes that will be for the eastbound WA SR16 brought me to within 50 yards of actually stepping foot on the anchorage and catwalks of the new bridge."
"As the temporary path crossed what would be the eastbound highway's three lanes, it passed along a fence with a 12 foot gap as a result of an open gate. With not a soul present and absolutely no 'No Trespassing' signs anywhere, I did what comes naturally and entered. 50 yards later brought me to another fence right at the edge of the anchorage. This one did have one 'Authorized Persons Only Beyond This Point' sign. I figure I'd at least honor that one. Had I been 20 years older with my career behind me and my child raised well beyond college I'd give it a try and start walking up the catwalk. I'd also have to make sure I didn't have the 1GB compact flash card nearly full from the 40 previous bridges visited this trip in my camera - in case it would be impounded by an unsympathetic rent-a-cop."
"Clearly visible here is the Tram Frame over the anchor saddle. It is at this point where the main cable's 19 strands each containing 464 wires will splay down into the chamber in the lower left corner of this image. Note the security camera on the upper left outside edge of the Tram Frame. Likewise there's one on the adjacent tram frame looking over to this side."
"Anchorage of the cables used to keep the Tram Frames upright on the catwalks."
"Centered looking back on the Tram Frame cable anchors and of the pneumatic tugger (orange piece of equipment) used to power the red wheel, thus cable that will contain the cable spinning wheels across the Puget Sound from the far side anchorage to the anchorage just in front of here and back again."
"Well underway on my trek across the western side span. The web of cables under the catwalks of the new bridge are the tie-back cables. A process of modern suspension bridge building is to pull back - or tie back the towers at their summits several feet towards shore. The towers are then gradually returned back to plumb as more main cable and deck are added to the main span since it's proportionately heavier than the side spans."
"Although the new bridge's towers are concrete, some resemblance to the existing bridge is seen in the cross braces of the panels between the tower legs."
"It wasn't until my visit that I became sure of what type of deck will be used on the new bridge. While the ways of old are to build deep stiffening trusses like that of the existing bridge, most modern suspension bridges have an aerofoil deck that is much slender and only a few feet deep. After viewing these openings in the tower leg I now believe a stiffening truss will be used on the newer bridge - definitely parting from the norm, but continuing to maintain some resemblance to the existing bridge. The deep truss as evidenced by the distance between the two openings (the upper one at roadway level - the lower one most likely accessible from a catwalk within the lowest extremity of the truss) will provide expansion opportunities on the new bridge for a second level someday in the future."
"Looking down on the base of the newer bridge and of the myriad of equipment needed to build a bridge. The cables draped across the barges are part of the tie-back operation. With cables already extending from the tower's summit back to just in front of the anchorage (see upcoming images), these cables will pull down on those cables thus pulling the towers back towards shore."
"Porta Potties 500' up. By judging from the direction the flag is facing, one must rule out relieving themselves from the catwalk to avoid any confrontations from motorists on the existing bridge."
"Various images of the catwalks."
"Some humor [the sign says 'NO Fishing From Catwalk'] directed towards those willing to make the trek to mid-span of the existing Tacoma Narrows Bridge. I've been across this bridge four times on four separate trips (1993, 1996, 2003, and now 2005) and have not encountered anybody else using the walkways."
"Tram Frame and the tined main cable strand form. The cable spinning wheel will be guided through the Tram Frame laying down groups of four wires at each pass down into the tined main cable strand form. With the wire being nearly the diameter of a standard #2 pencil, it will take 2204 passes of the spinning wheel to accumulate the 8816 wires (19 strands of 464 wires) into a main cable of 20 1/2 inches in diameter. 19,000 miles of wire will be used between the two main cables."
"The western anchorage. The large opening is forethought given to the possibility that someday the new bridge may support a second level underneath within the stiffening girder and access to that would have to come through here. The roof is where the highway passes over onto the bridge deck."
"In the front portion of the anchorage below is where the tie-back cables from the tower summits are anchored. It appears that the inner assembly of the four on each side are already sharing their load and taking their pull as the remaining three are still slack on each side."
"The main cables will enter the anchorage at a point where the tram frames containing the blue cable guides are located. The main cable will then splay into it's 19 strands, then each strand even further splaying in half (or even quarters) forming loop(s) around a steel strand shoe. This will all take place just before reaching what would appear here to be the backside of the anchorage. The steel strand shoes are each fixed to a pair of 4 1/2 inch diameter high strength steel rods 50 feet long and buried further into the concrete that is not visible. Not only does this anchorage extend much further back, but down as well to resist the pull of the main cables from the load they'll bear."
"The opening that appears to be a doorway on the far wall enters the splay chamber just behind (to the right of) the solid concrete pillar supporting the rocker saddle above. The splay chamber extends to the left to a point I would imagine being where the angled section of concrete visible at the back corner is. It is at this angle to the lower right that the strand shoe rods are buried further and at which the main cables splay down into the splay chamber from the upper left."
"Close up of the tie-back cable assemblies. My visit was on Sunday, October 9. Cable spinning commenced on Thursday, October 13, 2005 Tightening up these assemblies and pulling the towers back towards shore may have been one of the last operations to tend to before the cable spinning could get underway."
"From the bridge viewing park a half mile south of the bridge. I was running out of daylight here."
