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 Reports.com.
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.
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.
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.
Signs on the bridge tender’s house foundation, west abutment, navigation lights, and Warren truss web. 061819 #879.
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.
PORTAL VIEWS and TRAIN DECK APPROACH SPAN
Looking at the westbound portal.
Westbound portal, train approach span, train deck, Warren truss web, and rows of lights of the clear span. #860.
Near bridge center. #721.
The westbound portal from the south side of the span. #726.
Warning lights and electric utilities on approach to the west portal. #867.
Truss web on the south side of the span and the west portal. #866
Westbound portal and Warren Truss web, and lateral bracing of the train deck approach span. 06/18/19 #859.
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.
CTA bus eastbound. #695.
- Substructure: The part of any construction which supports the superstructure. The piers, pedestals, and abutments of a bridge or trestle.
- 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.
- 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.
- 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.
- 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.
- Holth, Nathan. Lake Street Bridge. NBI Data Sheet (2010 Inventory). Historic Bridges.org Bridge Browser. Bridge documented: August 12, 2006 and 2010- May 2012. https://historicbridges.org/bridges/browser/?bridgebrowser=truss/lake/ 27 October 2019.
- Wikipedia contributors. “FIPS county code.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 15 Aug. 2019. Web. 28 Oct. 2019.
- “bascule”. https://www.merriam-webster.com/dictionary/bascule.
Merriam-Webster, 2019. Web. 27 October 2019.