The Bridge as a Connection

 
Why were the
bridges built?
 

The Bridge as Machine

 
How did they
build the bridges?
 

The Bridge as Art

 
Why do the bridges
look like they do?
  People of the Bridge
 
Who designed
the bridges?
Resources

 
The Bridge Machine Since 1950

Surviving earthquakes and lightning, and other special features of the
Current Narrows Bridge.
 

WHAT'S HERE:

 

Workmen adjust bolts on a suspender cable band, nearly 300 feet above traffic WSDOT, 10-12-00, MVC-001S
Workmen adjust bolts on a suspender cable band, nearly 300 feet above traffic WSDOT, 10-12-00, MVC-001S

How Big is the Bridge?    
"Span Stats"-- 1940 vs 1950  
Maintenance—Keeping the Span Sparkling  
The Inspection of 2000  
Paint it "Narrows Green"  
Danger, Earthquakes, and Lightning  
  Working Hard To Keep Traffic Moving

How Big is the Bridge?

The towers are how tall?
The two towers of the current Tacoma Narrows Bridge rise 467 feet above the piers. How tall is that? By comparison, the Seattle Space Needle is 138 feet taller, measuring 605 feet high. The Statue of Liberty is only 305 feet high, or 162 feet shorter than the Bridge's towers.

Weird Fact #8

The bridge is how long?
You could line up nearly 10 Seattle Space Needles end-to-end and match the length of the Narrows Bridge today. Or, lay down New York's great Empire State Building 4 times and you'd be really close. Or, try corralling 1,195 kids, say 7th graders with an average height of 5 feet, then lay them head-to-toe and they will stretch the length of the Narrows Bridge. Check out the TABLE below for other interesting comparisons.

SPAN STATS
Current Narrows Bridge (1950) Compared with Other "Structures"

Current Narrows Bridge Compared with Other "Structures"
Name Total Length
or Height
How many would fit on the Tacoma Narrows Bridge? (5,979 feet)
Space Needle, Seattle 605 feet 9.9
Golden Gate Bridge, San Francisco 6,450 feet 0.9
Empire State Building, New York 1,453 feet 4.1
Statue of Liberty, New York 305 feet 19.6
Eiffel Tower, France 1,063 feet 5.6
Titanic 885 feet 6.7
Average 7th grader 5 feet 1,195

The Bridge is How Wide?
60 feet between the main suspension cables. If you use the average 5-foot tall 7th Grader as a yardstick, you'll only need 12 of them head-to-toe.

"Span Stats"
How Does the Current Narrows Bridge Compare with Galloping Gertie?

Current Narrows Bridge & 1940 Narrows Bridge Comparison
 
LENGTH 1950 Bridge 1940 Bridge
Total Structure Length 5,979 feet 5,939 feet
Suspension Bridge Section 5,000 feet 5,000 feet
Center Span 2,800 feet 2,800 feet
Shore Suspension Spans (2), each 1,100 feet 1,100 feet
East Approach and Anchorage 365 feet 345 feet
West Approach and Anchorage 614 feet 594 feet
 
ANCHORAGES
Current Narrows Bridge and 1940 Narrows Bridge Comparison
Anchorages (shore anchors) 1950 Bridge 1940 Bridge
Weight of each anchorage 66,000 tons 52,500 tons
Concrete in each anchorage 25,000 cu. yds. 20,000 cu. yds.
West Anchorage (concrete anchor blockand gallery) 164 feet long
169 feet long
70 feet wide
66 feet deep
East Anchorage (concrete anchor block and gallery), plus approach, administration buildings and toll house 185 feet long 173 feet long
70 feet
50 feet high
West Anchorage, construction Woodworth & Co. Woodworth & Cornell, Inc.
$340,000
East Anchorage, construction Woodworth & Co. Pacific Bridge Co.
$500,000
 
PIERS
Current Narrows Bridgeand 1940 Narrows Bridge Comparison
PIERS 1950 Bridge 1940 Bridge
West Pier, total height 215 feet 198 feet
West Pier, depth of water 120 feet 120 feet
West Pier, penetration at bottom 55 feet 55 feet
East Pier, total height 265 feet 247 feet
East Pier, depth of water 135 feet 140 feet
East Pier, penetration at bottom 90 feet 105 feet
Area 118 feet, 11 inches by 65 feet, 11 inches 118 feet, 11 inches by 65 feet, 11 inches
Reinforced concrete in piers 111,234 cu. yds. 111,234 cu. yds.
Number of caisson anchors, east pier 32 32
Number of caisson anchors, west pier 24 24
Weight of each caisson anchor 570 tons 570 tons
Size of caisson anchors 12 x 12 x 51 feet 6 inches
in 900 foot diameter circle around caisson
12 x 12 x 51 feet 6 inches
in 900 foot diameter circle around caisson
Distance between piers 2,700 feet 2,700 feet
Distance to shore from east pier 650 feet 650 feet
Distance to shore from west pier 1,030 feet 1,030 feet
 
CABLES
Current Narrows Bridgeand 1940 Narrows Bridge Comparison
CABLES 1950 Bridge 1940 Bridge
Diameter of Main
Suspension Cable
20.25 inches 17.5 inches
Weight of Main
Suspension Cable (each)
5,441 tons 3,817 tons
Weight Sustained by Cables 18,160 tons 11,250 tons
Number of No. 6 Wires
in Each Cable
8,705 6,308
Sag ratio
(elevation drop per foot)
1:10 1:12
Total Length of Wire 104,094,390 feet, = 19,715 miles 74,926,424 feet, = 14,191 miles
 
TOWERS
Current Narrows Bridge and 1940 Narrows Bridge Comparison
TOWERS 1950 Bridge 1940 Bridge
Height above water 507 feet 443 feet
Height above piers 467 feet 425 feet
Height above roadway 307 feet 230 feet
Weight of each tower 2,675 tons 1,927 tons
 
ROADWAY - DECK
Current Narrows Bridgeand 1940 Narrows Bridge Comparison
ROADWAY - DECK 1950 Bridge 1940 Bridge
Center Span Height Above Water 187.5 feet 195 feet
Weight of center span 7,250 lb./ft 5,700 lb./ft
Traffic lanes 4 2
Width of Roadway 49 feet 10 inches 26 feet
Width between Cables 60 feet 39 feet
Width of Sidewalks(2), each 3 feet 10 inches 5 feet
Number of girders and type 2 Warren trusses 2 plate girders
Depth of girders 25 feet 8 feet
Suspender cables 32 foot intervals 50 foot intervals
Thickness of roadway 6-3/8 inch reinforced concrete 5-1/4 inch reinforced concrete
 
MATERIALS
Current Narrows Bridge and 1940 Narrows Bridge Comparison
Material 1940 Bridge Current
Structural Steel 10,000 tons 17,000 tons
Cable wire 3,750 tons 6,000 tons
Concrete in anchorages 20,000 cu.yds 25,000 cu.yds
Superstructure weight 5,800 lbs/foot 8,678 lbs/foot
 

SPAN RATIOS
 

Bridge Width to Length (of Center Span) Girder Depth to Length (of Center Span)
1940 Narrows Bridge 1:72 1:350
Current Narrows Bridge 1:46 1:112
Golden Gate Bridge 1:47 1:168
George Washington Bridge 1:33 1:120
Bronx-Whitestone Bridge 1:31 1:209
 
STATISTICAL PROFILE
Current Narrows Bridge and 1940 Narrows Bridge Comparison
Categories 1940 Narrows Bridge
(Galloping Gertie)
Current (1950)
Narrows Bridge
Total Structure Length 5,939 feet 5,979 feet
Suspension Bridge Section 5,000 feet 5,000 feet
Center Span 2,800 feet 2,800 feet
Shore Suspension Spans (2) Each 1,110 feet 1,110 feet
Center Span Height Above Water 195 feet 187.5 feet
Width of Deck (cables, center-to-center) 39 feet 49 feet 10 inches
Width of Sidewalks (2), each 5 feet 3 feet 10 inches
Ratio, deck to center span 1:72 1:56
Anchorages:    
Weight of Shore Anchors 52,500 tons 66,000 tons
East Approach and Anchorage 345 feet 365 feet
West Approach and Anchorage 594 feet 614 feet
Cables:    
Diameter of Main Suspension Cable 52,500 tons 66,000 tons
Weight of Main Suspension Cable 3,817 tons 5,441 tons
Weight Sustained by Cable 11,250 tons 18,160 tons
Sag Ratio (elevation drop per foot) 1:12 1:10
Number of No. 6 Wires Each Cable 6,308 8,705
Total Length of Wire 14,191 miles 19,715 miles
Towers:    
Height Above Water 443 feet 507 feet
Height Above Piers 425 feet 467 feet
Weight of Each Tower 1,927 tons 2,675 tons
Piers:    
East Pier, Total Height 247 feet 265 feet
East Pier, Depth of Water 140 feet 140 feet
East Pier, Penetration at Bottom 90 feet 90 feet
West Pier, Total Height 198 feet 215 feet
West Pier, Dept of Water 120 feet 120 feet
West Pier, Penetration at Bottom 55 feet 55 feet
Area 118 feet, 11 inches by 65 feet, 11 inches 118 feet, 11 inches by 65 feet, 11 inches
 
FINANCES & CONSTRUCTION
Current Narrows Bridgeand 1940 Narrows Bridge Comparison
FINANCING 1940 Bridge 1950 Bridge
P.W.A. grant (1938)
R.F.C. loan revenue bonds TOTAL
$2,894,958
$3,750,000
$6,644,958
-----
Bond Issue   $14,000,000
Final Cost $6,618,138 $14,011,384
Tolls Removed ------ October 1965
Time to Construct 19 months 29 Months
Tolls car and driver 75 cents one way; $1.25 roundtrip car and driver 50 cents one way; $1.00 roundtrip

Maintenance-- Keeping the Span Sparkling

From its opening in October 1950 until May 1965, the current Narrows Bridge was a toll facility. The Washington Toll Bridge Authority operated and maintained the Bridge, which collected over $19 million in tolls from motorists. Since then, the bridge has been the responsibility of the Washington Department of Highways, and its successor the Washington State Department of Transportation (WSDOT).

  The maintenance crew often works under the roadway, where motorists never see them, and where it looks like this WSDOT
  The maintenance crew often works under the roadway, where motorists never see them, and where it looks like this WSDOT
 

Today, the man in charge of keeping the bridge in top shape is Kip Wylie, Maintenance Supervisor at the Narrows Bridge. Wylie supervises a crew of five workers: three painters and two ironworkers. They stay busy with lots of replacement and repair work on the bridge, now over 50 years old. Painting season is roughly April 1 to November 1. During winter months, the crew works make sure the bridge is free of ice and snow so commuters have a safe and quick transit over the Narrows.

The cost is a very modest maintenance budget for the bridge--$1.7 million for the two-year budget period. That sounds like a lot, but it disappears fast. Now that you've studied the "Span Stats," you know just how big the bridge is. That mile-long structure with lots of moving parts takes a major maintenance job to keep it clean and in good working order. Good management by Wylie and his crew gets the most done for the least amount.
 

 

  From bottom to top—painting and other maintenance takes the crew right to the base of the towers legs WSDOT
  From bottom to top—painting and other maintenance takes the crew right to the base of the towers legs WSDOT
 

Where does the money go? Paint and street repairs are huge items. One of the biggest costs is repairing of the "expansion joints." There is a lot of movement where the East Deck and West Deck meet at the expansion joint. Each end of the bridge can move up to 16 inches, responding to the hottest summer weather (which expands the structure) and the coldest winter days (which contract the bridge deck). Often, there's little movement—not enough for motorists to notice. But, the expansion joints take a lot of punishment from traffic and from wind and temperature variations. And, they are over 50 years old, so they have become a constant repair item. When the speed limit was raised from 45 mph to 55 mph over the Narrows Bridge in the mid 1990s, the wear and tear on the expansion joints jumped significantly. And, so did the cost of repairs.

Inspections are a vital part of the maintenance work. The crew is always on the look out for signs of trouble. And, every Friday two of the crew takes do a general inspection of the towers, cables and anchorages. Once a month they look carefully at the main cables for paint cracks and other problems.

In 1983 an independent engineering consulting firm completed a comprehensive inspection of the bridge. They discovered several things. The suspender cables had stretched over the years. The towers' legs showed signs of increasing stress. And, the hydraulic dampers were not working well because the seals were deteriorating, causing loss of hydraulic fluid and pressure. Another independent consultant's inspection in 1991 used computer models and other sophisticated methods to evaluate the Current Narrows Bridge's health. Tests showed that the stretching of the suspender cables discovered in 1983 was actually not significant. Importantly, the 1991 inspection recommended a series of seismic tests to determine how well the Narrows Bridge could survive a major earthquake.

The Inspection of 2000

  During the 2000 inspection, the main suspension cable was unwrapped and wedges driven to separate the wires, so the interior could be examined for rust, deterioration and moisture. WSDOT, 9-19-00 16
  During the 2000 inspection, the main suspension cable was unwrapped and wedges driven to separate the wires, so the interior could be examined for rust, deterioration and moisture. WSDOT, 9-19-00 16
 
The inspection of 2000 marked a major milestone for the Tacoma Narrows Bridge, and for its maintenance crew. With plans moving forward for a brand new, second bridge (now under construction and to be completed in 2007), the WSDOT was required to show that the current span was in good shape, and that the new (2007) Narrows Bridge was not going to replace it. The inspection was performed by a private company that inspects bridges all over the country. At the end of the intensive evaluation, the verdict was impressive: "This bridge," they reported, "is one of the best in the nation for its maintenance and condition."

Paint It "Narrows Green"

Some call it "Gertie Green." Officially, it is "Narrows Green." It takes 6,000 gallons and 10 years of summertime work (roughly April 1 to November 1) for the crew to paint the Narrows Bridge.

Weird Fact #17

Painting the bridge is dangerous work. The bridge crew follows safety requirements and procedures closely. Each worker wears a parachute harness—a full body harness—in the event of an accidental fall. You're "hooked off" at all times with 5,000 lb. test rope. The harness is designed so you can hang suspended for several hours while waiting for rescue. Back in the 1950s when the bridge was built, painters and maintenance men wore a simple belt.

Danger, Earthquakes, and Lightning

  Walking the cable is one of the routine parts of the job
  Walking the cable is one of the routine parts of the job
WSDOT, TNB drb2
 

Routine work is different on the Narrows Bridge, but it is still routine. There is picking up debris on the roadway (thanks to careless litterbugs). There is the chore of taking the 1-man elevator up a tower leg to inspect the airplane navigation beacon atop a tower. On rainy days, the crew inspects concrete on the anchorage. And, there's also lots of shop work, machining or cobbling pieces to repair equipment.

Working on a cable suspended 300 feet over cars and trucks as they whiz along the roadway is also mundane to the crew. Sometimes, they use the "spider," a 1-man platform with a waist-high cage that uses a motor-driven winch to take the maintenance crewman up or down to a repair site. Complacency with routine is a challenge. When you clip your safety harness to a line and dangle a hundred feet over the roadway or 500 feet over the water, it's important to pay attention.

Danger comes with the territory. Kip, Moergen, and the rest of the crew routinely work at great heights and in rough weather. Any given day, they don't really know what will come up. "That's the best part of the job," says maintenance lead Jon Moergen. "It can also be the worst."

One of the most memorable incidents for Kip Wylie happened during the winter of 1997. There was a terrible thunder storm. Rain was coming down sideways in sheets, driven by a high wind. The towers were steady. Then, Wylie got a call from the Washington State Patrol, telling him there was no navigation beacon on Tower 5 (East Tower). He went up to the tower top, battling the freezing rain and buffeting gusts. What he found was more surprising that scary. Lightning had struck the beacon. It popped the huge fixture's two bulbs, but otherwise there was no damage.

An ice storm that same winter took out power in the area for 3 days. The storm left a 2-inch thick sheet of ice covering the entire bridge. There was no power for the elevator, which meant one of the crew had to climb the 280 feet to the top of each tower using the hand ladder in a tower leg. Falling icicles prompted closure of the bridge for some 16 hours.

The "Nisqually Earthquake" that struck Puget Sound in February 2001 proved a little too exciting on the Narrows Bridge. Jon Moergen vividly recalls that day. The bridge swayed more than he'd ever seen it, first one way, then back the other. There was no damage when the shaking was all over, except for a bent housing where the cable passes into the east anchorage. Nonetheless, recalls Moergen, "It was scary." For a guy like him, who thinks nothing of walking up the main cable or dangling hundreds of feet over the chilly tides of the Narrows, that's saying a lot.

Several big windstorms have blasted the Narrows Bridge over the last 5 decades. One storm hit the bridge with winds of 75 miles per hour. Kip Wylie recalls a day when gusts up near 100 miles an hour slammed the span. A few times officials have closed the bridge to avoid having cars blown into the oncoming traffic lanes. But, not once since 1950 has the current Tacoma Narrows Bridge rippled, waved, bounced, or galloped.

Weird Fact #20

  Kip Wylie straddles the cable
  Kip Wylie straddles the cable while positioning the cable compactor.
WSDOT, 9-21-00 9
 

Working Hard To Keep Traffic Moving

Keeping the traffic moving is a top priority when repairs are needed. Most commuters seldom see or notice the maintenance crew's work. Routine repairs are scheduled for times when there is the least traffic. That means the late night and early morning hours on the weekends. Sometimes, non-routine events come along.

Accidents happen all the time at the Tacoma Narrows Bridge—not just traffic fender benders, but accidents to the bridge.

For example, a few years ago, a truck hauling a submarine part to a U. S. Navy installation on the Peninsula tried to squeeze into one lane with its oversize load. The result was five long holes in the deck's pavement and a dent in one of the towers. Barges or boats run into the piers too often. Not long ago, a barge hauling a 220-foot tall crane struck the bridge's center span, causing some structural damage. Within recent months, large vehicles have ripped into various parts of the structure, including a hit on the main cable that tore off part of the wrapping wire.

Even emergency repairs are scheduled to minimize traffic disruptions. The crew works in the middle of the night and in all kinds of weather. One recent incident had the crew working all night long in a howling wind and rainstorm.

We don't notice, and that's how it's supposed to be. Repairing damage to the Tacoma Narrows Bridge is part of the work of the maintenance crew. But, it's one of the least seen, most overlooked, and least appreciated jobs they perform.

<-- Site Home
<-- WSDOT TNB project page

toptop
 


  Copyright WSDOT © 2005

    Traffic & Roads | Search | Contact WSDOT | WSDOT Business | WSDOT Home