History Still Matters, or It Should for Effective Management of Post-WWII Bridges
History Still Matters, or It Should for Effective Management of Post-WW II Bridges Why Is It So Vexing To Use History To Evaluate Bridges? Mary E. McCahon Historian TranSystems- Lichtenstein
Some of America’s Most Significant Postwar Bridges TN-1950 FL-1950 PA-1950 OH-1952
From Modest-LookingBeginning –Technology AdvancesTo Stunning Successes Zakim Bridge Boston (Cable Stayed) 1980s Moreland Interchange (Continous Box) Metro Atlanta GA DOT.
Historic Significance Same As Other Bridge Types: Use NR Guidance• Shares Common History with Other New Technologies – Think ReinforcedConcrete Types Supplanting Metal Truss Bridges Prior to WW 1.• Historic Context Varies: Some States Prestressed Leaders, Most StatesFollowers. Use NR criteria to identify significant examples.• Under Federalism, States Adopt at Their Discretion. Significance Is At StateLevel, Not Federal or National.• Early Examples of Types & Designs That Become Common Are Significant –When Technology Is New and Influential. 5 Early of 310 Pre-1960 Are Historic Not All 310 < 1960
1949-1951 Walnut Lane Bridge Introduces P/S to Bridges 1949-1951 @ Fairmount Park, Philadelphia
What Is Prestressed Concrete? Internally Stressed to Preload Before Live Loads Are Applied (Think Pre-Compressed) Pretensioned or Post-Tensioned = Prestressed
Why Prestressed Concrete? • Ancient Structural Principle. Used in TN in 1907-08. •Stronger for Given Section. •Significantly Reduces Deflection Cracking Under Load. • Fabricated/Precast Under Controlled Conditions Continues Well-Established Pre-WW II Tradition. • Speed of Building Bridges Using Small Cranes. • More Economical Alternative to Steel. Immediately Proven Advantage. 1907-09 Shelby St. Bridge @ Nashville
Near Simultaneous Developments Associated with Walnut Lane Resultin Workhorse Types That Still Dominate 1950 • Conditions Were Right for Innovation & Visionary Leaders. PA’s Own Box Beam Secondary FL’s I Beam Primary Roads. Roads. Spring Beam Test Decision to Use for Skyway
Box Beam For Secondary Road Use Is PA ProductConcrete Products Corporation of America @ Pottstown, PA • 7-Stand Wire & Prestressed @ Factory First Time EVER •Achieves H-20 Loading • Rigid & Lateral Stability • Up to 50’ Span Lengths • Easy Transport and Installation • PA Dept Hwy Support & 18’-36’ Ready Market 38’-50’
Making CPCA Beam1. Strand in Form 2. Prestressing 3. Sonotubes for Voids
Let Us now Praise Famous Men (and Bridges) “basic element that made the prestressed concrete industry possible, practical and economical in North America.” C. Zollman, 1981 1955 Use Over Expressway @ PHL Workhorse Type PA Product 102 Predate 1955 14 Eligible (pre-1953)
FL Hwy Dept Lead on Primary Road Type & Develop AASHTO BeamWilliam Dean Fl Hwy Dept SelectsP/S Beams for Signature Bridge --He Leads Nation to StandardDesign Still Used Today Builds on Walnut Lane Momentum. Industry Shows Economy & Technical Qualities; Public Servant Strives for Better Engineering.
Dean Influences National Design Standards That Make I Beam Common Technology In Many StatesStubby vs Skinny: BPR/FHWA Change & Adopt 1956-57– DOTs Make It TheirDesign Standard (Not Innovative; Followers States).Adopting European Precedent Would Have Been a Calamity for Fledgling Industry.
Bill Dean Had It Right Dean’s Beams Survive. FL State Park.Walnut Lane Bridge Replaced1992 Because of ConcreteCracking & MoisturePenetration. HAER Recorded.
Using Historic Context to Assess Ohio’s 1951-1960 Population•Leader State with Counties (Not Hwy Dept) Out In Front 1952 Roseville Bridge Muskingum County • First P/S I Beam Bridge in State -- (Now Oldest Extant in Nation) •Listed in NBI as RC, Not P/S- David Simmons Saved History • Represents Local Engineers Using FL Beam Design • Regional Influence – 400 Attend Inspection… it is apparent that in the future prestressedconcrete will be competitive in first cost withother conventional types of bridges. R. Mason , Contractor
Other OH Engineers & Fabricators Build on Roseville Bridge Success Despite Success of Box Beam, Still Experimentation As Pioneers Put Ideas About Use of Material Into Different Secondary Road Designs.1954 2’-Wide Modified T Greene Co. Charles & William Roberts Work With OH Counties & Build Casting Yard to Supply Beams.
Ross Bryan Builds First (Opened Before Walnut Lane Bridge) LinearStressed Bridge at Jackson (Madison County, TN Late in 1950 1 2 3
It’s Technology That Is Significant – It’s All About the Beams, Notthe Deck and Railings Bridge Had Wider Deck & New Metal Railings When DOT, SHPO, FHWA Determine Bridge Historic Hanly & Young, Cincinnati Local Engineers Using FL “Stubby” I Beams For Local Roads Early Use of P/S I Beams Hamilton Co. 1953/2001 Early Reuse of P/S I Beams
Later Examples Can Be Historic Too • One of First Instances 100’- Long Beams • Represents Milestone in Evolution of Now Common Type Dominates Last Half 20th Century • State-of-the-Art Yard To Fabricate Needed Length • Link to Pottstown Origin of Box Beam. • History of All Technologies = Continued Development 1959 Suder Ave @ Toledo
Each State Has Its Own Historic Context – This is State Significance, JustLike Earlier Bridge Types/Designs Michigan’s Most Significant 1950s Non-Suspension Bridge, A 1954-55 Box Beam Industry & Locals Leading- Promoting
Historic Contexts Support Not All States Have Historic P/S BridgesGeorgia Is Follower State:No Historic P/S Bridges… Yet• No Impact on Local LevelUntil After Mid-1960s. RCPrecast Designs Rule. (NBIError, Actually 25 of Them).• Adopt BPR/AASHO StandardDesigns Common To ManyStates.• Overpass Bridges AreOriginal Design Components ofI System. Look At Plan Sheets,Funding, Engineers Say So,and Scholarship Confirms.
South Carolina Also Follower State: Evaluations Ongoing Double Tee Does Double Duty Strong History Precast Slabs on Piles by State Forces Start with P/S Channel Beams in 1955 For Secondary
There is Sufficient Historic Context to Assess Prestressed SignificanceThere Seems to Be Insufficient Understanding of Readily Available History & How to Conserve Beams “… there is insufficient historic context/scholarship exists for this period of bridge building to be confidently assess significance for this structural type.” “ Character-defining features that contribute to integrity include; the slab [deck?], longitudinal beams, floor beams [diaphragms?], a parapet or railing if integral, and abutments, piers and wingwalls, when present.” “ The fact that ASCE is seeking identification of prestressed concrete structures means that this bridge type only recently has been perceived as significant.” A Context For Common Historic Bridge Types, p. 3-102
There is Sufficient Historic Context to Assess Prestressed Significance • Every State Has Its Own Context. Use Annual Reports & Technical Periodicals & Conference Proceedings. • Nationally Applicable Book Still Available (epub): Incredible Resource. • Find Old-Timers & Interview Them Before They Are Gone. • Understand That Significance Is the Beams & Technology, Not Cute Railings.
Ah That There Were Ways to Preserve Them• Problems That Cause Deterioration Same As With Other Bridge Types • Decks Leak, Drains Clogged, Moisture Penetration Rusts Steel, Cover Material Spalls, Timber Piles Rot. Sound Familiar?
Identify Historic, Then Preservation Through Conservation“I am on my way to Washington To Look Inside Historic Box Beam Bridges for FHWA.” Be Proactive About Good Maintenance Practices to Conserve Historic Ones.
May The Force Always Be With You ToUnderstand These Milestones in Civil Engineering History Thank You