Editing Golden Gate Bridge (section)

===Seismic vulnerability and improvements{{Anchor|Seismic retrofit}}===
[[File:Details Golden Gate Bridge 04 2015 SFO 1951.jpg|thumb|South approach sub-structure with [[Seismic base isolation|seismic isolators]] (short black cylinders) added as part of the Seismic Retrofit Construction Project]]
Modern knowledge of the effect of earthquakes on structures led to a program to [[Seismic retrofit|retrofit]] the Golden Gate to better resist seismic events. The proximity of the bridge to the [[San Andreas Fault]] places it at risk for a significant earthquake. Once thought to have been able to withstand any magnitude of foreseeable earthquake, the bridge was actually vulnerable to complete structural failure (i.e., collapse) triggered by the failure of supports on the {{convert|320|ft|m|adj=on}} arch over Fort Point.<ref>{{cite news |title=70 Years: Spanning the Golden Gate: New will blend in with the old as part of bridge earthquake retrofit project |first=Carl |last=Nolte |author-link=Carl Nolte |newspaper=San Francisco Chronicle |date=May 28, 2007 |url=https://www.sfgate.com/bayarea/article/70-YEARS-Spanning-the-Golden-Gate-New-will-2558505.php }}</ref> A $392&nbsp;million program was initiated to improve the structure's ability to withstand such an event with only minimal (repairable) damage. A custom-built electro-hydraulic synchronous lift system for construction of temporary support towers and a series of intricate lifts, transferring the loads from the existing bridge onto the temporary supports, were completed with engineers from [[Balfour Beatty]] and [[Enerpac]], without disrupting day-to-day commuter traffic.<ref>[http://www.roadsbridges.com/showing-fancy-foot-work Showing fancy foot work] {{Webarchive|url=https://web.archive.org/web/20210123132652/http://www.roadsbridges.com/showing-fancy-foot-work |date=January 23, 2021 }}. ''Roads&Bridges'' (December 28, 2000).</ref><ref name = "retrofit">{{cite web |url=http://goldengatebridge.org/projects/retrofit.php |title=Overview of Golden Gate Bridge Seismic Retrofit |access-date=June 21, 2008 |author=Golden Gate Bridge Authority |date=May 2008 |archive-date=June 16, 2008 |archive-url=https://web.archive.org/web/20080616091141/http://goldengatebridge.org/projects/retrofit.php |url-status=dead }}</ref> Although the retrofit was initially planned to be completed in 2012, {{As of|2017|05|lc=y}} it was expected to take several more years.<ref name = "retrofit"/><ref>{{cite web |url=http://enr.construction.com/features/transportation/archives/050103-1.asp |title=Famed Golden Gate Span Undergoes Complex Seismic Revamp |access-date=June 21, 2008 |last=Gonchar |first=Joann |date=January 3, 2005 |publisher=McGraw-Hill Construction}}</ref><ref>{{Cite web|url=https://sanfrancisco.cbslocal.com/2017/05/24/costly-golden-gate-bridge-retrofit-still-years-away-from-completion/|title=Costly Golden Gate Bridge Retrofit Still Years Away From Completion|date=May 24, 2017|access-date=July 29, 2019}}</ref>

{{Anchor|Doyle Drive replacement project}}
The former elevated approach to the Golden Gate Bridge through the [[Presidio of San Francisco|San Francisco Presidio]], known as Doyle Drive, dated to 1933 and was named after Frank P. Doyle, a director of the [[California State Automobile Association]].<ref>{{cite book |url=http://www.presidioparkway.org/about/history.aspx |title=Presidio Parkway re-envisioning Doyle Drive |publisher=Presidio Parkway Project |access-date=May 6, 2010 |archive-date=December 26, 2009 |archive-url=https://web.archive.org/web/20091226180130/http://www.presidioparkway.org/about/history.aspx }}</ref> The highway carried about 91,000 vehicles each weekday between downtown San Francisco and the [[North Bay (San Francisco Bay Area)|North Bay]] and points north.<ref>{{cite web |url=http://www.sfcta.org/content/view/275/94/ |title=Doyle Drive Replacement Project |publisher=San Francisco County Transportation Authority |access-date=May 6, 2010 |archive-url=https://web.archive.org/web/20100426064515/http://www.sfcta.org/content/view/275/94/ |archive-date=April 26, 2010 }}</ref> The road was deemed "vulnerable to earthquake damage", had a problematic 4-lane design, and lacked shoulders; a San Francisco County Transportation Authority study recommended that it be replaced. Construction on the $1&nbsp;billion replacement,<ref>{{cite web |url=https://www.sfgate.com/bayarea/article/Doyle-Drive-makeover-will-affect-drivers-soon-3276621.php |archive-url=https://web.archive.org/web/20100316012125/http://articles.sfgate.com/2010-01-05/bay-area/17466642_1_doyle-drive-caltrans-closures |url-status=live |archive-date=March 16, 2010 |title=Doyle Drive makeover will affect drivers soon |last=Cabanatuan |first=Michael |date=January 5, 2010 |newspaper=San Francisco Chronicle |access-date=May 6, 2010}}</ref> temporarily known as the Presidio Parkway, began in December 2009.<ref>{{cite book |url=http://www.presidioparkway.org/construction_info/ |title=Current Construction Activity |series=Presidio Parkway re-envisioning Doyle Drive |publisher=Presidio Parkway |access-date=May 6, 2010 |archive-date=April 26, 2010 |archive-url=https://web.archive.org/web/20100426112839/http://www.presidioparkway.org/construction%5Finfo/ }}</ref>
The elevated Doyle Drive was demolished on the weekend of April 27–30, 2012, and traffic used a part of the partially completed Presidio Parkway, until it was switched onto the finished Presidio Parkway on the weekend of July 9–12, 2015. {{as of|2012|May|}}, an official at Caltrans said there is no plan to permanently rename the portion known as Doyle Drive.<ref>{{cite news |url=http://www.pressdemocrat.com/article/20120501/news/205011005?tc=ar |title=Smith: It's wrecked, but it's still 'Doyle Drive' |newspaper=Press Democrat |date=May 1, 2012 |access-date=May 2, 2012 |archive-date=March 13, 2014 |archive-url=https://web.archive.org/web/20140313152842/http://www.pressdemocrat.com/article/20120501/news/205011005?tc=ar }}</ref>
{{Clear}}