Outer Drive Bridge
Encyclopedia
The Outer Drive Bridge, also known as the Link Bridge was started in 1929 and completed in 1937 as part of Ickes’s Public Works Administration
in Chicago
. It was planned by the Chicago Plan Commission
, using Hugh E. Young as the consulting engineer, was designed by the Strauss Engineering Company, built by the American Bridge Company
, and erected by Ketler and Elliot Company.
was meant to create many jobs for Chicagoans and ease traffic flow on Michigan Ave
and in the Loop. The Outer Drive Bridge runs along the shore of Lake Michigan
from the far South Side of the city to the Loop, across the Chicago River
, and connects the south to the north side of the city. In 1937 it was the longest, widest, and heaviest bascule bridge
in the world.
. Due to a lack of provided security by Chicago Park District
s, the allotment for the bridge was revoked until the districts were all in position to comply. The total cost of the Outer Drive is estimated at $11,563,000.
of 40,000 vehicles per day on a saving of eight minutes between Oak St.
and Seventh St., made possible by the use of the bridge rather than Michigan Ave and on a delay cost estimated to be one cent per car per minute show that the saving in vehicle operation should amount to $584,000 per annum, which, capitalized at 5% would indicate that $23,360,000 could properly be spent to eliminate this delay. This shows that the Outer Drive bridge project is economically reasonable, showing a possible saving of $11,797,000.
“Each leaf is to be operated by two sets of gear train
s, consisting of four sets of gear reductions. Each gear train is connected to two 100-hp. main operating motors, only one of which is to be used at a time. The time required for opening or closing the bridge against a 28-m.p.h. wind is stated to be 57.6 sec, of which 10 sec. is for acceleration
and 2.86 sec. for deceleration. The main operating racks are bolted to the underside of the outside trusses, the pitch radius being 20 ft. The operating pinion, with a pitch diameter of 40 in, is mounted on a shaft of the gear train.
Heavy locking devices are provided at the center of the bridge and at the rigid in its closed position. The center lock in addition to holding the leaves together in their closed position, also transmits live load shear from one leaf to the other. This center lock consists of a set of four female castings bolted to the river end of one leaf, and a second set of four male units bolted to the river end of the other leaf, all castings being on the centerlines of the trusses. The male unit consists of two castings forming a toggle
.
Heel or rear locks are necessary to prevent the leaves from opening when live loads pass over the part of the bridge between the trunnions and the rear break in the floor. Each leaf is provided with two pairs of rear locks, each pair being placed between the inside and outside trusses. The four locks of a leaf are connected by shafting, and operation by means of two 15-hp. motors set either side of the centerline of the bridge” (April 22, 1937).
Public Works Administration
The Public Works Administration , part of the New Deal of 1933, was a large-scale public works construction agency in the United States headed by Secretary of the Interior Harold L. Ickes. It was created by the National Industrial Recovery Act in June 1933 in response to the Great Depression...
in Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
. It was planned by the Chicago Plan Commission
Chicago Plan Commission
The Chicago Plan Commission is a commission implemented to promote the Plan of Chicago, often called the Burnham Plan. After official presentation of the Plan to the city on July 6, 1909, the City Council of Chicago authorized Mayor Fred A. Busse to appoint the members of the Chicago Plan Commission...
, using Hugh E. Young as the consulting engineer, was designed by the Strauss Engineering Company, built by the American Bridge Company
American Bridge Company
The American Bridge Company is a privately held civil engineering firm specializing in the construction and renovation of bridges and other large civil engineering projects, founded in 1900, and headquartered in Coraopolis, Pennsylvania, a suburb of Pittsburgh.-Products and industry positioning:The...
, and erected by Ketler and Elliot Company.
Significance/Purpose
The building of this bridgeBridge
A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...
was meant to create many jobs for Chicagoans and ease traffic flow on Michigan Ave
Michigan Avenue (Chicago)
Michigan Avenue is a major north-south street in Chicago which runs at 100 east south of the Chicago River and at 132 East north of the river from 12628 south to 950 north in the Chicago street address system...
and in the Loop. The Outer Drive Bridge runs along the shore of Lake Michigan
Lake Michigan
Lake Michigan is one of the five Great Lakes of North America and the only one located entirely within the United States. It is the second largest of the Great Lakes by volume and the third largest by surface area, after Lake Superior and Lake Huron...
from the far South Side of the city to the Loop, across the Chicago River
Chicago River
The Chicago River is a system of rivers and canals with a combined length of that runs through the city of the same name, including its center . Though not especially long, the river is notable for being the reason why Chicago became an important location, as the link between the Great Lakes and...
, and connects the south to the north side of the city. In 1937 it was the longest, widest, and heaviest bascule bridge
Bascule bridge
A bascule bridge is a moveable bridge with a counterweight that continuously balances the span, or "leaf," throughout the entire upward swing in providing clearance for boat traffic....
in the world.
Funds
While the completion of the Outer Drive was considered one of the most important projects in the PWA it took many years to complete. A main issue was fundingFunding
Funding is the act of providing resources, usually in form of money , or other values such as effort or time , for a project, a person, a business or any other private or public institutions...
. Due to a lack of provided security by Chicago Park District
Chicago Park District
The Chicago Park District is the oldest and largest park district in the U.S.A, with a $385 million annual budget. It has the distinction of spending the most per capita on its parks, even more than Boston in terms of park expenses per capita...
s, the allotment for the bridge was revoked until the districts were all in position to comply. The total cost of the Outer Drive is estimated at $11,563,000.
Economic Justification
Calculations based on a traffic flowTraffic flow
Traffic flow, in mathematics and civil engineering, is the study of interactions between vehicles, drivers, and infrastructure , with the aim of understanding and developing an optimal road network with efficient movement of traffic and minimal traffic congestion problems.-History:Attempts to...
of 40,000 vehicles per day on a saving of eight minutes between Oak St.
Oak Street (Chicago)
Oak Street is a short street on Chicago's Gold Coast at 1000 North in Chicago's street numbering system, running from 138 east to 648 west in the Near North Side community area of Chicago in Cook County, Illinois, United States. It ends without crossing the North Branch of the Chicago River...
and Seventh St., made possible by the use of the bridge rather than Michigan Ave and on a delay cost estimated to be one cent per car per minute show that the saving in vehicle operation should amount to $584,000 per annum, which, capitalized at 5% would indicate that $23,360,000 could properly be spent to eliminate this delay. This shows that the Outer Drive bridge project is economically reasonable, showing a possible saving of $11,797,000.
Bridge Operation
According to Engineering News-RecordEngineering News-Record
Engineering News-Record is a weekly magazine that provides news, analysis, data and opinion for the construction industry worldwide...
“Each leaf is to be operated by two sets of gear train
Gear train
A gear train is formed by mounting gears on a frame so that the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, this provides a smooth transmission of rotation from one gear to the next.The transmission of...
s, consisting of four sets of gear reductions. Each gear train is connected to two 100-hp. main operating motors, only one of which is to be used at a time. The time required for opening or closing the bridge against a 28-m.p.h. wind is stated to be 57.6 sec, of which 10 sec. is for acceleration
Acceleration
In physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ...
and 2.86 sec. for deceleration. The main operating racks are bolted to the underside of the outside trusses, the pitch radius being 20 ft. The operating pinion, with a pitch diameter of 40 in, is mounted on a shaft of the gear train.
Heavy locking devices are provided at the center of the bridge and at the rigid in its closed position. The center lock in addition to holding the leaves together in their closed position, also transmits live load shear from one leaf to the other. This center lock consists of a set of four female castings bolted to the river end of one leaf, and a second set of four male units bolted to the river end of the other leaf, all castings being on the centerlines of the trusses. The male unit consists of two castings forming a toggle
Toggle
Toggle may refer to:*Toggle mechanism*Toggle switch*Toggling harpoon*A type of textile closure, like an elongated button*Toggle , a character in the comic strip Doonesbury...
.
Heel or rear locks are necessary to prevent the leaves from opening when live loads pass over the part of the bridge between the trunnions and the rear break in the floor. Each leaf is provided with two pairs of rear locks, each pair being placed between the inside and outside trusses. The four locks of a leaf are connected by shafting, and operation by means of two 15-hp. motors set either side of the centerline of the bridge” (April 22, 1937).