P1101101cm Michigan.us

The “Mighty Mac”

The Mackinac Bridge is currently the fifth longest suspension bridge in the world. In 1998, the Akashi Kaikyo Bridge in Japan became the longest with a total suspension of 12,826 feet. The Mackinac Bridge is the longest suspension bridge in the western hemisphere.

The total length of the Mackinac Bridge is 26,372 feet. The length of the suspension bridge (including anchorages) is 8,614 feet. The length from cable bent pier to cable bent pier is 7,400 feet. Length of main span (between towers) is 3,800 feet.

 

The width of the roadway is 54 feet. The outside lanes are 12 feet wide (2), the inside lanes are 11 feet wide (2), the center mall is 2 feet wide, and the catwalk, curb and rail width is 3 feet on each side – totaling 54 feet. The stiffening truss width in the suspended span is 68 feet wide making it wider than the roadway it supports.

The height of the roadway at mid-span is approximately 200 feet above water level. The vertical clearance at normal temperature is 155 feet at the center of the main suspension span and 135 feet at the boundaries of the 3,000 ft. navigation channel.

All suspension bridges are designed to move to accommodate wind, change in temperature, and weight. It is possible that the deck at center span could move as much as 35 feet (east or west) due to high winds. This would only happen under severe wind conditions. The deck would not swing or “sway” but rather move slowly in one direction based on the force and direction of the wind. After the wind subsides, the weight of the vehicles crossing would slowly move it back into center position.

The steel superstructure will support one ton per lineal foot per roadway (northbound or southbound). The length of the steel superstructure is 19,243 feet. Each direction will, therefore, support 19,243 tons. The answer is 38,486 tons (2 x 19,243 tons).

 

Facts & Figures

The Mackinac Bridge is currently the fifth longest suspension bridge in the world. The bridge opened to traffic on November 1, 1957. The following facts and figures are quoted from David Steinman’s book “Miracle Bridge at Mackinac”.

 

LENGTHS

Total Length of Bridge (5 Miles) : 26,372 Ft 8,038 Meters

Total Length of Steel Superstructure : 19,243 Ft. 5,865 Meters

Length of Suspension Bridge (including Anchorages) : 8,614 Ft. 8,614 Ft.

Total Length of North Approach : 7,129 Ft. : 2,173 Meters

Length of Main Span (between Main Towers) : 3,800 Ft. 1,158 Meters

 

HEIGHTS AND DEPTHS

Height of Main Towers above Water : 552 Ft 168.25 Meters

Maximum Depth to Rock at Midspan : Unknown Unknown

Maximum Depth of Water at Midspan : 295 Ft. 90 Meters

Maximum Depth of Tower Piers below Water : 210 Ft. 64 Meters

Height of Roadway above Water at Midspan : 199 Ft. 61 Meters

Underclearance at Midspan for Ships : 155 Ft. 47 Meters

Maximum Depth of Water at Piers : 142 Ft. 43 Meters

Maximum Depth of Piers Sunk through Overburden : 105 Ft. 32 Meters

 

CABLES

Total Length of Wire in Main Cables : 42,000 Miles 67,592 km

Maximum Tension in Each Cable : 16,000 Tons 14,515,995 kg

Number of Wires in Each Cable : 12,580

Weight of Cables : 11,840 Tons 10,741,067 kg

Diameter of Main Cables : 24 1/2 Inches 62.23 cm

Diameter of Each Wire : 0.196 Inches .498 cm

 

WEIGHTS

Total Weight of Bridge : 1,024,500 Tons 929,410,766 kg

Total Weight of Concrete : 931,000 Tons 844,589 kg

Total Weight of Substructure : 919,100 Tons 326,931,237 kg

Total Weight of Two Anchorages : 360,380 Tons 326,931,237 kg

Total Weight of Two Main Piers : 318,000 Tons 288,484,747 kg

Total Weight of Superstructure : 104,400 Tons 94,710,087 kg

Total Weight of Structural Steel : 71,300 Tons 64,682,272 kg

Weight of Steel in Each Main Tower : 6,500 Tons 5,896,701 kg

Total Weight of Cable Wire : 11,840 Tons 10,741,067 kg

Total Weight of Concrete Roadway : 6,660 Tons 6,041,850 kg

Total Weight of Reinforcing Steel : 3,700 Tons 3,356,584 kg

 

RIVETS AND BOLTS

Total Number of Steel Rivets : 4,851,700

Total Number of Steel Bolts : 1,016,600

 

DESIGN AND DETAIL DRAWINGS

Total Number of Engineering Drawings : 4,000

Total Number of Blueprints : 85,000

 

MEN EMPLOYED

Total, at the Bridge Site : 3,500

At Quarries, Shops, Mills, etc. : 7,500

Total Number of Engineers : 350

 

IMPORTANT DATES

Mackinac Bridge Authority Appointed : June, 1950

Board of Three Engineers Retained : June, 1950

Report of Board of Engineers : January, 1951

Financing and Construction Authorized by Legislature : April 30, 1952

D.B. Steinman Selected as Engineer : January, 1953

Preliminary Plans and Estimates Completed : March, 1953

Construction Contracts Negotiated : March, 1953

Bids Received for Sale of Bonds : December 17, 1953

Began Construction : May 7, 1954

Open to traffic : November 1, 1957

Formal dedication : June 25-28, 1958

50 millionth crossing : September 25, 1984

40th Anniversary Celebration : November 1, 1997

100 millionth crossing : June 25, 1998

 

In Memory Of

Forever Remembered

 

During the construction of the Mackinac Bridge in the 1950’s, five men unfortunately lost their lives.

One man died in a diving accident; one man fell in a caisson while welding; one man fell into the water and drowned; and two men fell from a temporary catwalk near the top of north tower.

The names of those five men (and the date of their deaths) are listed below.

Frank Pepper, Sept. 16, 1954

James R. LeSarge, Oct. 10, 1954

Albert Abbott, Oct. 25, 1954

Jack C. Baker, June 6, 1956

Robert Koppen, June 6, 1956

After the bridge was built and opened to traffic, one MBA maintenance worker lost his life. On August 7, 1997, Daniel Doyle, a bridge painter, fell from his painting platform and drowned in the Straits of Mackinac. His tragic and unfortunate death shocked everyone.

Dan and others who have lost their lives on the job are permanently honored by MDOT in the Clare Welcome Center located in Clare, Michigan. The Employee Memorial is a permanent tribute to highway workers all over Michigan who lost their lives along highways and bridges. The Clare memorial provides an opportunity to educate the public about the human cost of building and maintaining Michigan’s transportation system.

All six of these men will forever be remembered by many.

 

Prentiss M. Brown

1889-1973

Born in St. Ignace, Michigan, Mr. Brown Graduated from LaSalle High school in 1905, Albion College in 1911, and did post graduate work at the University of Illinois. Prentiss married Marion Walker, and practiced law with his father in the St. Ignace area. From 1932 to 1943 he served in the U.S. Congress and Senate. In 1950 Prentiss M. Brown was appointed to the Mackinac Bridge Authority and elected its first Chairman. Mr. Brown, with the assistance of fellow Authority members William Cochran, Murray Van Wagoner, and Charles Fisher, Jr., secured the financing for the Mackinac Bridge. Mr. Brown considered this to be one of his most rewarding accomplishments.

Prentiss M. Brown is well known for his struggle to get the Mackinac Bridge built over the Straits of Mackinac. Mr. Jack Carlisle, in a radio broadcast over WWJ radio station on February 22, 1954, told his listeners of Mr. Brown’s struggle. The transcript from Mr. Carlisle’s broadcast was later published in a newspaper and is as follows:

 

” After a 20-year fight which often seemed hopeless, there finally is going to be a five-mile bridge across the Straits of Mackinac. As one of the states most ambitious projects, it will link Michigan’s two peninsula’s. It will cost about $99 million. It is scheduled for completion in November, 1957.

The bridge project had many stalwart partisans. However, the project actually became a reality through the determination of one man – Prentiss M. Brown, Chairman of the Michigan Mackinac Bridge Authority. Brown, a former United States Senator and Chairman of the Board of the Detroit Edison Company, refused to accept defeat when it seemed inevitable. Prentiss M. Brown just wouldn’t stay licked.

His energetic determination to get the Mackinac Bridge financed is undoubtedly due to the fact that he was born and raised in the midst of a daily realization of the need for the bridge. Now 64 years old, Prentiss Brown spent a lifetime in his old home town of Saint Ignace, Michigan. He was once a bellhop at the old Astor Hotel on Mackinac Island. Probably the bridge idea would have died completely in the last year – if it had not been for an incident that happened to Brown 34 years ago. He was 30 years old then and a lawyer. He was scheduled to appear before the State Supreme Court in Lansing to argue a case.

Brown had to get across the Straits to catch a train at Mackinaw City. However, both of the ferry boats were stuck in the winter ice. He and another hardy voyager, who also had important business on the side of the Straits, hired a horse and a cutter. They started across the ice. They ran into ice hummocks ten feet high and had to send the cutter back to Saint Ignace. They proceeded on foot.

 

They ran into 50 acres of open water, like a big pond, and had to circle it. All in all, they hiked four miles across the ice. The wind was blowing up a small gale. It was snowing. By the time they had spent most of the day walking – well, they missed their train.

Brown said in a recollection today, “That bitter hike across the Straits made a lasting impression on me – for the need of a bridge across the Straits.”

Prentiss Brown never forgot. That is the reason that 20 years ago Brown became legal counsel for the first Mackinac Bridge Commission. Back in 1933 under Governor Comstock. And Prentiss worked for love. He would accept no money. Four years ago he became chairman of the Mackinac Bridge Authority. By 1952, it looked like the RFC woud finance the bridge across the Straits. Whereupon, a New York investment broker offered to organize a private syndicate in October, 1952, to do the financing.

He tried to float the Mackinac Bridge bonds in March and again in June, 1953. Both times he failed. As a matter of fact, it looked like the bridge project was a gone goose last June. For lack of financing. Due to the high cost of money. But Prentiss refused to stay licked. The project was revived on the New York bond market in November due to the increase in interest rates and the increase in traffic across the Straits.

 

It was only six days ago that a check for $98,500,000 to finance the Straits of Mackinac Bridge was put into Brown’s hands in New York. One hundred and fifty investment brokers underwrote the sale of revenue bonds for a commission pot of three million dollars.

Actually, the deal went through last year with just 13 days to spare before the offer of State maintenance for the bridge would have expired. In a four-year battle under Brown to get the bridge finance – this was a slim margin to win a victory.

Michigan will not soon forget the gallant fight of Prentiss M. Brown for the Straits of Mackinac Bridge.”

 

The Mackinac Bridge Authority has created a token in honor of Prentiss M. Brown. To view this and all other tokens visit Token Gift Packs / Medallion.

 

www.mackinacbridge.org/history/the-mighty-mac/

 

 

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