Lake Street Bridge Illinois S Brand 061819 #5

Pons Triangulum. The Lake Street Bridge Overview: Steel Majesty, Uplifting Functional Artwork. #1A.

By Divi Logan, Photographer and Author.

Bridge inspection has a standard format, ensuring every element is documented and nothing important is missed. Principles in these articles are based on procedures in standard bridge inspection manuals and forms from United States departments of transportation, and the National Bridge Inventory (NBI).

First comes identification of the structure. The Bridge Inspector’s Reference Manual (BIRM) from the U.S. Department of Transportation, includes the following in its Structure Inventory and Appraisal Sheet; the numerical data are taken from the NBI record at Bridge

Name of Structure: Lake Street Bridge
State Name and Code: Illinois (17)
Structure Number: 016602900000000
Inventory Route Number: 1405
Highway Agency District: City or Municipal Highway Agency (04)
County Code: Cook (031) and Place Code: Chicago (14000)
Features Intersected: South Branch, Chicago River
Facility Carried: CTA commuter rail on the upper deck; vehicular and pedestrian traffic on the lower level.

LOCATION, APPROACH and OVERVIEWS: The photos were taken before I began researching the elements of a rigorous bridge inspection. They are displayed as suggested by inspection guidelines instead of the chronological order of the photo file.

PONS Lake & Wacker LocMark #852 061810 1931.

Location: W. Lake Street and N. Upper Wacker Drive, near the historic Wacker Drive monument and plaque at the northeast approach to the westbound portal. 06/18/19 #852.

PONS Lake St NE+ N Elev #881 061819 1937

Northeast corner, with north elevation and bascule bridge features: bridge tender’s houses, round yellow fenders, abutments, wing walls, and in this case two decks and two leaves, the halves meeting in the center at the navigation lights seen just under the superstructure. 06/18/19 #881.

PONS Lake St Overview #879 061819 1937

Signs on the bridge tender’s house foundation, west abutment, navigation lights, and Warren truss web. 061819 #879.

PONS Lake St NE View #875 061819 1936

Truss web, warning lights, barricade arm and gate, a CTA train, huge gusset plates with dozens of rivets, and girders supporting the train deck approach span where it merges to the clear span over the river. 061819 #875.


Looking at the westbound portal.

PONS Lake St WPort Decks #131 061819 1813


PONS Lake St WPort Decks #132 061819 1813


PONS Lake St LatBr #681 061819 1908


PONS Lake St LatBr #682 061819 1908


PONS Lake St WestPort 2 #860 061819 1933

Westbound portal, train approach span, train deck, Warren truss web, and rows of lights of the clear span. #860.

PONS Lake St LatBr #573 061819 1856


PONS Lake St LatBr #636 061819 1904


PONS Lake St LatBr #677 061819 1908


PONS Lake St LatBr #713 061819 1912


PONS Lake St LatBr #714 061819 1912.JPG


PONS Lake St LatBr #718 061819 1913


PONS Lake St LatBr #721 061819 1914

Near bridge center. #721.

PONS Lake St LatBr #726 061819 1914

The westbound portal from the south side of the span. #726.

PONS Lake St WestPort 1 #867 061819 1935

Warning lights and electric utilities on approach to the west portal. #867.

PONS Lake St WestPort 1 #866 061819 1934

Truss web on the south side of the span and the west portal. #866

PONS Lake St Train + Warren WPort 061819 #859 1932

Westbound portal and Warren Truss web, and lateral bracing of the train deck approach span. 06/18/19 #859.

PONS Lake St Train + WPort #840 1929


PONS Lake St Truss Web Girders #837 061819 1928

Wide-angle truss web, train deck girders, sidewalk rail, guardrail, and barricade gate near or at the southeast corner of the westbound portal. 06/18/19. #837.

PONS Lake St LatBr #695 061819 1910

CTA bus eastbound. #695.

PONS Lake St LatBr #736 061819 1915


PONS Lake St LatBr #741 061819 1915


PONS Lake St LatBr #747 061819 1916


PONS Lake St LatBr #748 061819 1916


PONS Lake St WBPort #824 061819 1926


PONS Lake St WBPort #826 061819 1927


PONS Lake St WBPort #830 061819 1927


PONS Lake St WBPort #831 061819 1927


PONS Lake St WBPort #833 061819 1927



  1. Substructure: The part of any construction which supports the superstructure. The piers, pedestals, and abutments of a bridge or trestle.
  2. Superstructure: That portion of a bridge or trestle lying above the piers, pedestals, and abutments. The part of a structure which receives the live load directly.
  3. Warren Truss: some forms have no verticals and others include the verticals, wherein the diagonals carry compression and tensile forces, and the verticals are bracing elements. A true Warren Truss has equilateral triangles.
  4. Through Truss (Through Span): A span in which the traffic is carried between the trusses and which has lateral bracing in the plane of the upper chords.

*These photos are the best of the structure’s elements from my personal record-breaking picture-taking day of a single bridge, 883 different views taken between 6:02 PM and 7:39 PM on June 18, 2019. *


1. Bascule: an apparatus or structure (such as a drawbridge) in which one end is counterbalanced by the other on the principle of the seesaw or by weights; from the French, “seesaw”.
2. Culvert: primarily a hydraulic structure, and its main purpose is to transport water flow efficiently.
3. FIPS:  Federal Information Processing Standard Publication 6-4.


  1. U. S. Department of Transportation. Federal Highway Administration. Bridge Inspector’s Reference Manual. By Thomas W. Ryan, P.E, J. Eric Mann, P.E., Zachary M. Chill, E.I.T., and Bryan T. Ott. Revised. Washington: Government Printing Office. December 2012. Report No. FHWA NHI 12-050. Available from the National Technical Information Service in Springfield, Virginia 22161 and from the
    Superintendent of Documents. 27 October 2019.
  2. Holth, Nathan. Lake Street Bridge. NBI Data Sheet (2010 Inventory). Historic Bridge Browser. Bridge documented: August 12, 2006 and 2010- May 2012. 27 October 2019.
  3. Wikipedia contributors. “FIPS county code.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 15 Aug. 2019. Web. 28 Oct. 2019.
  4. “bascule”.

     Merriam-Webster, 2019. Web. 27 October 2019.

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