Application of titanium alloy bars for strengthening reinforced concrete bridge girders (part a: shear) : final report.

Details

• Creators:
  Knudtsen, Jonathan ; Higgins, Christopher
• Corporate Creators:
  Oregon. Dept. of Transportation. Research Section
• Corporate Contributors:
  United States. Federal Highway Administration
• Subject/TRT Terms:
  • Bond strength (Materials)
  • Durability
  • Epoxides
  • Girders
  • Reinforced concrete
  • Reinforced concrete bridges
  • Reinforcing bars
  • Retrofitting
  • Strengthening (Maintenance)
  • Titanium alloys
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• Publication/ Report Number:
  FHWA-OR-RD-18-01;SPR 775
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States
• Edition:
  Final report
• Corporate Publisher:
  Oregon. Dept. of Transportation. Research Section
• Abstract:
  Large numbers of conventionally reinforced concrete bridges (RC) were constructed during the interstate ; highway expansion of the 1950’s and remain in the national inventory. Coincidently, deformed steel reinforcing ; bars were standardized. The standardized deformation requirements dramatically changed bond provisions in all ; relevant design codes and designers began to use straight-bar terminations of the flexural reinforcing bars where ; they were no longer required by calculation. This produced terminations in flexural tension zones without special ; detailing provisions. At the same time, design codes overestimated the concrete contribution to shear resistance ; and thus designs provided less transverse steel than permissible by modern standards. These poor details ; combined with heavier loads have resulted in diagonal cracking of the girders. Application of modern design ; provisions to assess vintage RC members typically results in low predicted capacity. Load restrictions or ; replacement of bridges is expensive and thus structurally effective and economical strengthening approaches are ; required. ; Near-surface mounting (NSM) of supplemental reinforcing bars has emerged as a common retrofit method for ; strengthening RC structures. In this method, bars are bonded with an adhesive within grooves that are cut into ; the surface of the member. The most common reinforcing material used in the NSM application is fiber ; reinforced polymer (FRP). FRP materials are elastic until fracture thus providing no ductility. In addition, they ; can debond prematurely limiting the effectiveness of the repair. For this reason, new titanium alloy bars (TiABs) ; were developed as a potential alternative for FRP bars in NSM applications. ; Small diameter (1/4 in.) NSM TiABS were applied to full-size bridge girder specimens that were shear deficient ; and tested to failure in the laboratory. Two different epoxy materials were considered, as well as two different ; configurations of TiAB bars (single leg and double leg stirrups). The combined effects of high-cycle fatigue ; loading and repeated freeze-thaw exposure were investigated to assess long-term durability of the proposed approach and materials. ; Results showed that NSM TiABs provided significant increases in the strength when compared to ; similar unstrengthened specimens. The TiABs were observed to achieve the yield stress prior to/at ultimate. ; Anchorage of the TiABs was sufficient to produce rupture over the main diagonal cracks. The double leg ; TiABs were easier to construct and provide additional confinement across the beam soffit. It was determined ; that some reduction in strength was observed for one of the epoxy materials due to the combined fatigue and ; environmental effects. Three methods were used to analyze the experimental results which could conservatively ; predict strength. Strength reduction factors were developed for each method to be used in design.
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• Format:
  PDF
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/32577/dot_32577_DS1.pdf
• File Type:
  [PDF - 41.06 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:332d0c29354e0cdba016a884136d6aaa7b11f8d9894600607bef223f796184ab07689b4d40ba903ad4944b765b6f65c90a395912ee037a6eadb3834e0953c20d